WO2017064843A1 - 非水電解質二次電池 - Google Patents
非水電解質二次電池 Download PDFInfo
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- WO2017064843A1 WO2017064843A1 PCT/JP2016/004426 JP2016004426W WO2017064843A1 WO 2017064843 A1 WO2017064843 A1 WO 2017064843A1 JP 2016004426 W JP2016004426 W JP 2016004426W WO 2017064843 A1 WO2017064843 A1 WO 2017064843A1
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/581—Chalcogenides or intercalation compounds thereof
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
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- H01M50/411—Organic material
- H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
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- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Definitions
- the present invention relates to a non-aqueous electrolyte secondary battery.
- Non-aqueous electrolyte secondary batteries represented by lithium ion secondary batteries are widely used in portable terminals, electric vehicles, hybrid vehicles, and the like, and further improvements in energy density are expected in the future.
- lithium transition metal oxides are used as the positive electrode active material for lithium ion secondary batteries in practical use
- carbon materials are used as the negative electrode active material
- nonaqueous electrolytes in which a lithium salt is dissolved in a nonaqueous solvent are used as the electrolyte. It is used for.
- JP2015-128063A International Publication No. 2015/083314 Special table 2015-507837
- the non-aqueous electrolyte secondary battery having a large resistance at the interface between the positive electrode and the cation exchange resin layer or the negative electrode and the cation exchange resin layer and having the cation exchange resin layer
- the present inventors have found that the high rate discharge performance is low.
- a non-aqueous electrolyte secondary battery for solving the above problems is disposed between a positive electrode containing sulfur, a negative electrode, a non-aqueous electrolyte, a positive electrode and a negative electrode, and has a roughness factor of 3
- a cation exchange resin layer having the first surface as described above.
- nonaqueous electrolyte secondary battery having low interface resistance on the first surface of the cation exchange resin layer and having excellent high rate discharge performance.
- FIG. 1 is an external perspective view of a nonaqueous electrolyte secondary battery according to a first embodiment. It is typical sectional drawing which shows the local structure of the nonaqueous electrolyte secondary battery of this embodiment. It is the schematic which shows the electrical storage apparatus comprised by gathering together the nonaqueous electrolyte secondary battery which concerns on 1st embodiment. It is typical sectional drawing which shows the structure of the cell for resistance measurement used for the Example of this embodiment. It is typical sectional drawing which shows the structure of the test cell used for the Example of this embodiment. It is a figure which shows the relationship between the interface resistance in an Example, and the roughness factor of the cation exchange resin layer surface.
- a nonaqueous electrolyte secondary battery includes a first surface that is disposed between a positive electrode containing sulfur, a negative electrode, a nonaqueous electrolyte, and a positive electrode and a negative electrode, and has a roughness factor of 3 or more.
- a cation exchange resin layer is disposed between a positive electrode containing sulfur, a negative electrode, a nonaqueous electrolyte, and a positive electrode and a negative electrode, and has a roughness factor of 3 or more.
- the interface resistance of the first surface of the cation exchange resin layer is reduced, and the high-rate discharge performance of the nonaqueous electrolyte secondary battery is improved.
- the arithmetic average roughness Ra of the first surface of the cation exchange resin layer is preferably 0.5 ⁇ m or more.
- the interface resistance can be reduced.
- the maximum height roughness Rz of the first surface of the cation exchange resin layer is preferably 5 ⁇ m or more.
- the maximum height roughness Rz of the first surface of the cation exchange resin layer is 5 ⁇ m or more, even when the electrolyte salt concentration is low, the interface resistance of the first surface of the cation exchange resin layer can be reduced.
- the non-aqueous electrolyte secondary battery may further include a porous layer.
- the porous layer is preferably in contact with the first surface of the cation exchange resin layer.
- the nonaqueous electrolyte includes a positive electrode electrolyte disposed between the positive electrode and the cation exchange resin layer, and a negative electrode electrolyte disposed between the negative electrode and the cation exchange resin layer, the positive electrode electrolyte includes lithium polysulfide,
- the sulfur equivalent concentration of the negative electrode electrolyte is preferably lower than the sulfur equivalent concentration of the positive electrode electrolyte.
- the concentration in terms of sulfur of the positive electrode electrolyte is 1.2 mol / l or more.
- Such a configuration not only improves the charge / discharge cycle performance, but also increases the charge / discharge efficiency after the cycle.
- the concentration in terms of sulfur of the positive electrode electrolyte is preferably 3.0 mol / l or more.
- Such a configuration can provide a non-aqueous electrolyte secondary battery having high capacity and high energy density.
- the concentration in terms of sulfur of the positive electrode electrolyte is preferably 18 mol / l or less.
- the viscosity of the positive electrode electrolyte does not increase too much, and the interface resistance between the positive electrode electrolyte and the cation exchange resin layer does not increase too much, so the non-aqueous electrolyte secondary battery has a high utilization rate of sulfur and a high energy density. Is obtained.
- the concentration of anions contained in at least one of the positive electrode electrolyte and the negative electrode electrolyte is 0.7 mol / l or less.
- a nonaqueous electrolyte secondary battery having low interface resistance between the nonaqueous electrolyte and the cation exchange resin layer can be obtained.
- the concentration of anions contained in the positive electrode electrolyte is preferably 0.3 mol / l or less.
- At least one of the positive electrode and the negative electrode may contain a cation exchange resin, and the concentration of anions contained in the nonaqueous electrolyte may be 0.7 mol / l or less.
- the non-aqueous electrolyte secondary battery includes a non-aqueous electrolyte secondary battery including a positive electrode containing sulfur, a negative electrode, a cation exchange resin layer interposed between the positive electrode and the negative electrode, and between the positive electrode and the cation exchange resin layer.
- the first surface is provided.
- the non-aqueous electrolyte used in the non-aqueous electrolyte secondary battery usually includes an electrolyte salt and a non-aqueous solvent.
- a non-aqueous solvent that does not include an electrolyte salt is referred to as a “non-aqueous electrolyte”.
- the roughness factor is the ratio of the actual surface area to the apparent unit surface area (geometric unit area), and is an index indicating the roughness of the surface.
- the cation exchange resin layer is a layer containing a cation exchange resin and serves as a separator that keeps the positive electrode and the negative electrode in an insulating state.
- the cation exchange resin has a structure in which an anionic functional group such as a sulfonic acid group or a carboxylic acid group is bonded to a polymer mainly composed of hydrocarbon. Due to the electrostatic interaction of this anionic group, it has a high cation permeability, while the anion permeability is low. That is, the cation exchange resin allows lithium ions to pass therethrough and slightly dissociates in the positive electrode electrolyte (electrolytic solution) to block the passage of anionic lithium polysulfide. Thereby, since the cation exchange resin layer suppresses the movement of the lithium polysulfide from the positive electrode to the negative electrode, the shuttle phenomenon is suppressed.
- the lower limit of the roughness factor of the first surface which is at least one surface is 3, preferably 4, and more preferably 10.
- the upper limit of the roughness factor of the first surface of the cation exchange resin layer is preferably 20, more preferably 18, and still more preferably 16.
- the roughness factor is 3 or more, the resistance at the interface between the cation exchange resin layer and the nonaqueous electrolyte is reduced, so that the high rate discharge performance of the nonaqueous electrolyte secondary battery is improved.
- regulated to JISB0601: 2013 becomes like this.
- the arithmetic average roughness Ra satisfies the above range, the resistance at the interface between the cation exchange resin layer and the positive electrode can be reduced. Furthermore, in order to maintain the strength of the cation exchange resin layer, the arithmetic average roughness Ra is preferably 10 ⁇ m or less, more preferably 8 ⁇ m or less, and even more preferably 5 ⁇ m or less.
- the first surface of the cation exchange resin layer in the present embodiment preferably has a maximum height roughness Rz defined by JIS B 0601: 2013 of 5 ⁇ m or more, and more preferably 10 ⁇ m or more.
- the maximum height roughness Rz is preferably 30 ⁇ m or less, and more preferably 28 ⁇ m or less.
- the roughness factor, arithmetic average roughness Ra, and maximum height roughness Rz of the first surface of the cation exchange resin layer are determined by photographing and measuring the surface of the cation exchange resin layer under the following conditions and performing shape analysis.
- ⁇ Measuring equipment Ultra deep shape measuring microscope VK-8500 (manufactured by Keyence Corporation) Measurement range: 1.04 ⁇ 10 ⁇ 3 cm 2 -Shape analysis application: VK-H1A9 (manufactured by Keyence Corporation)
- Examples of the roughening treatment method in which the roughness factor of the surface of the cation exchange resin layer according to the present embodiment is 3 or more include a method of roughening the surface of the cation exchange resin layer with an abrasive such as sandpaper, and a sandblasting method. And a chemical etching method.
- an abrasive such as sandpaper
- sandpaper it is preferable to use sandpaper having a grain size of 320 to 1000 for abrasive cloth abrasives specified in JIS R 6010: 2000.
- the thickness of the cation exchange resin layer according to this embodiment is preferably 20 to 180 ⁇ m, and more preferably 30 to 180 ⁇ m.
- the thickness of the cation exchange resin layer can be sufficiently maintained even when the surface roughening treatment is performed, so that handling during battery manufacture becomes easy.
- the energy density of a battery can be improved.
- the cation exchange resin layer may be formed by forming a mixture of a cation exchange resin and other polymer into a thin film and roughening the surface.
- the other polymer materials constituting the porous layer described later can be appropriately used.
- the nonaqueous electrolyte secondary battery according to the present embodiment may further include a porous layer. It is preferable that the porous layer is in contact with the first surface of the cation exchange resin layer.
- the surface of a positive electrode and a negative electrode has the unevenness
- the porous layer containing a polymer is superior in flexibility to the cation exchange resin layer, so that the porous layer is in contact with the first surface of the cation exchange resin layer, so that the positive electrode-porous layer-cation exchange Good contact between the first surfaces of the resin layers or between the first surfaces of the negative electrode, the porous layer, and the cation exchange resin layer is maintained, and lithium ions are transmitted well. Furthermore, since the non-aqueous electrolyte can be held in the porous layer, uneven distribution of the non-aqueous electrolyte in the positive electrode or the negative electrode hardly occurs, and the charge / discharge reaction at the positive electrode or the negative electrode can be made uniform.
- the porous layer may be provided only between the positive electrode and the first surface of the cation exchange resin layer, or may be provided only between the negative electrode and the first surface of the cation exchange resin layer. Alternatively, a porous layer may be provided both between the positive electrode and the cation exchange resin layer and between the negative electrode and the cation exchange resin layer.
- the positive electrode electrolyte preferably contains lithium polysulfide. Furthermore, the sulfur equivalent concentration of the positive electrode electrolyte is preferably higher than the sulfur equivalent concentration of the negative electrode electrolyte.
- the “positive electrode electrolyte” and the “negative electrode electrolyte” may be collectively referred to as “nonaqueous electrolyte”.
- the lithium polysulfide produced at the positive electrode during the charge / discharge reaction is highly soluble in a non-aqueous solvent. Elution easily into the positive electrolyte during the discharge cycle.
- the present inventors only suppress elution of lithium polysulfide produced at the positive electrode.
- the lithium polysulfide in the positive electrode electrolyte can exhibit excellent charge / discharge cycle performance by contributing to the charge / discharge reaction as a positive electrode active material.
- the positive electrolyte contains lithium polysulfide
- the non-aqueous electrolyte secondary battery having high charge / discharge cycle performance is obtained by making the sulfur equivalent concentration of the positive electrode electrolyte higher than the sulfur equivalent concentration of the negative electrode electrolyte.
- the sulfur equivalent concentration is a value obtained by converting the concentration of the sulfur compound in the non-aqueous electrolyte into the concentration of sulfur atoms.
- 1 mol / l lithium sulfide corresponds to a sulfur equivalent concentration of 1 mol / l
- 1 mol / l Li 2 S 6 corresponds to a sulfur equivalent concentration of 6 mol / l
- 1 mol / l sulfur corresponds to a sulfur equivalent concentration of 8 mol / l.
- the lower limit of the concentration in terms of sulfur of the positive electrode electrolyte is preferably 1.2 mol / l, more preferably 1.5 mol / l, and even more preferably 3.0 mol / l.
- concentration in terms of sulfur is 3.0 mol / l or more, a non-aqueous electrolyte secondary battery having a high capacity and a high energy density can be realized.
- the upper limit of the concentration in terms of sulfur of the positive electrode electrolyte is preferably 18 mol / l, more preferably 12 mol / l, and even more preferably 9 mol / l.
- the sulfur equivalent concentration is not more than the above upper limit, the viscosity of the positive electrode electrolyte does not increase too much, and the interface resistance between the positive electrode electrolyte and the cation exchange resin layer does not become too high, so the utilization rate of sulfur is high and the energy density is high. A nonaqueous electrolyte secondary battery is obtained.
- the lithium polysulfides positive electrolyte contains, but are not limited to, lithium polysulfides represented by Li 2 S n (4 ⁇ n ⁇ 8) are preferred.
- Method for producing a lithium polysulfides represented by the composition formula Li 2 S n (4 ⁇ n ⁇ 8) is not limited.
- Li 2 S lithium sulfide
- sulfur S 8
- the mixture is placed in a sealed container and allowed to react for 4 days or longer in a thermostatic bath at 80 ° C. Can be obtained.
- the negative electrode electrolyte preferably has a lower sulfur equivalent concentration than the positive electrode electrolyte. That is, it is preferable that the total concentration of elemental sulfur, lithium polysulfide and Li 2 S contained in the negative electrode electrolyte is lower than that of the positive electrode electrolyte.
- Lithium polysulfide reacts with the negative electrode active material to reduce the charging depth of the negative electrode active material, and produces Li 2 S as a reduction product. Since Li 2 S is insoluble in the non-aqueous solvent, it precipitates on the negative electrode surface and reduces the reaction area of the negative electrode.
- the upper limit of the sulfur equivalent concentration of the negative electrode electrolyte is preferably 0.5 mol / l, and may be 0 mol / l. Since lithium polysulfide is known to react on the negative electrode surface to form a solid electrolyte coating (SEI), the negative electrode electrolyte preferably contains a small amount of lithium polysulfide.
- the concentration of the anion contained in the nonaqueous electrolyte is more preferably 0.7 mol / l or less.
- the aspect in which at least one of the positive electrode and the negative electrode includes the cation exchange resin is not particularly limited, it is preferably provided on the surface or inside of the positive electrode mixture layer or the negative electrode mixture layer. That is, the aspect which a cation exchange resin covers the surface of a mixture layer may be sufficient, and the aspect which exists in at least one part inside a mixture layer may be sufficient.
- the cation exchange resin allows only cations to pass and inhibits the passage of anions. Therefore, the transport number of lithium ions in the cation exchange resin is approximately 1. That is, the cation exchange resin is a single ion conductor.
- the transport number of lithium ions in a non-aqueous electrolyte containing a lithium salt since both lithium ions and counter anions move, the transport number of lithium ions is not 1, and the non-aqueous electrolyte is not a single ion conductor.
- the interface resistance is large at the interface between the nonaqueous electrolyte and the cation exchange resin layer.
- a lithium conduction path made of the cation exchange resin is formed between the cation exchange resin layer and the positive electrode active material or the negative electrode active material. That is, since lithium ions can go back and forth between the cation exchange resin layer and the positive electrode active material or the negative electrode active material without going through the nonaqueous electrolyte, the interface resistance of the cation exchange resin layer can be reduced. Thereby, it is estimated that the nonaqueous electrolyte secondary battery which has a high discharge capacity and the outstanding charging / discharging cycling performance can be obtained.
- the cation exchange resin provided in the positive electrode mixture layer is preferably 10% by mass to 150% by mass with respect to the total mass of the positive electrode mixture layer. It is preferable that the amount of the cation exchange resin is 10% by mass to 150% by mass with respect to the total mass of the positive electrode mixture layer because a continuous lithium ion conduction channel can be formed in the positive electrode mixture layer.
- the cation exchange resin provided in the negative electrode mixture layer is preferably 10% by mass to 150% by mass with respect to the total mass of the negative electrode mixture layer. It is preferable that the amount of the cation exchange resin is 10% by mass to 150% by mass with respect to the total mass of the negative electrode mixture layer because a continuous lithium ion conduction channel can be formed in the negative electrode mixture layer.
- the positive electrode in which the cation exchange resin is present in the positive electrode mixture layer can be produced as follows.
- a particulate positive electrode active material, a cation exchange resin, a conductive agent, and a binder are mixed with a dispersion medium such as alcohol or toluene to prepare a positive electrode mixture paste.
- the obtained positive electrode mixture paste is applied to both surfaces of a sheet-like positive electrode substrate, dried and then pressed to produce a positive electrode.
- a powder mixer such as a V-type mixer, an S-type mixer, a scraper, a ball mill, a planetary ball mill, or the like is used.
- a method of using dry or wet mixing is employed.
- the cation exchange resin the materials mentioned in the first embodiment can be used as appropriate.
- a negative electrode containing a cation exchange resin inside the negative electrode mixture layer can also be produced by the above-described method.
- a cation exchange resin covers the positive electrode or negative electrode surface by apply
- cation exchange resin exists in the mixture layer surface and inside because the solution containing a cation exchange resin permeates the inside of the mixture layer.
- the method for applying a solution containing a cation exchange resin include a spray method, a dispensing method, a dipping method, and a blade coating method.
- the cation exchange resin may be contained in at least one of the positive electrode and the negative electrode, but is preferably contained in the positive electrode, and may be contained in both the positive electrode and the negative electrode.
- the lithium polysulfide produced at the positive electrode during the charge / discharge reaction is suppressed from being eluted into the positive electrode electrolyte in the vicinity of the positive electrode, and the capacity of the positive electrode is unlikely to decrease.
- the cation exchange resin in the positive electrode and the negative electrode a lithium ion conduction path is formed by the cation exchange resin from the positive electrode through the cation exchange resin layer to the negative electrode. High discharge capacity and charge / discharge efficiency can be achieved.
- the nonaqueous electrolyte may contain an anion derived from an electrolyte salt.
- the anion in the present embodiment refers to an anion derived from an electrolyte salt dissolved in a non-aqueous solvent, and an anionic functional group such as a sulfonic acid group contained in the molecular structure of the cation exchange resin or a lithium-rich group. It does not include compounds in which a part of sulfide and lithium polysulfide is dissociated and anionic.
- the upper limit of the concentration of the anion contained in at least one of the positive electrode electrolyte and the negative electrode electrolyte is preferably 0.7 mol / l, more preferably 0.5 mol / l, still more preferably 0.3 mol / l.
- the upper limit of the concentration of the anion contained in the positive electrode electrolyte is preferably 0.3 mol / l, more preferably 0.2 mol / l, and may be 0 mol / l.
- the anion concentration is not more than the above upper limit, it is possible to reduce the viscosity of the nonaqueous electrolyte, and it is possible to obtain a nonaqueous electrolyte secondary battery having a high discharge capacity and excellent charge / discharge cycle performance.
- the lower limit of the concentration of the anion contained in at least one of the positive electrode electrolyte and the negative electrode electrolyte may be 0 mol / l, preferably 0.1 mol / l, and more preferably 0.3 mol / l.
- the positive electrode according to the present embodiment includes a positive electrode base material and a positive electrode mixture layer disposed directly or via an intermediate layer on the positive electrode base material.
- the positive electrode base material a known material can be appropriately used as long as it is an electronic conductor that does not adversely affect the battery.
- the positive electrode base material include aluminum, titanium, stainless steel, nickel, baked carbon, conductive polymer, conductive glass, etc., and aluminum and copper for the purpose of improving adhesiveness, conductivity, and oxidation resistance. Or the like can be used which have been treated with carbon, nickel, titanium, silver or the like.
- the shape of the positive electrode base material a film shape, a sheet shape, a net shape, a punched or expanded material, a lath body, a porous body, a foamed body, a formed body of fiber groups, and the like are used in addition to a foil shape.
- the thickness is not particularly limited, but a thickness of 1 to 500 ⁇ m is used.
- the intermediate layer is a coating layer on the surface of the positive electrode substrate, and reduces the contact resistance between the positive electrode substrate and the positive electrode mixture layer by containing a conductive agent such as carbon particles.
- a conductive agent such as carbon particles.
- the configuration of the intermediate layer is not particularly limited, and can be formed by, for example, a composition containing a binder and a conductive agent.
- the positive electrode mixture layer includes an active material, a conductive agent, and a binder, and the active material includes sulfur.
- the active material sulfur combined with a conductive material is preferably used.
- the conductive substance include carbon materials such as porous carbon, carbon black, graphite, and carbon fiber, and electron conductive polymers such as polyaniline, polythiophene, polyacetylene, and polypyrrole.
- the positive electrode mixture layer may contain an active material other than sulfur, a thickener, a filler, and the like as necessary.
- the positive electrode mixture layer may not contain solid-state sulfur.
- the positive electrode mixture layer contains only the conductive agent and the binder, and the lithium polysulfide in the positive electrode electrolyte contributes to charge / discharge as an active material. It is preferable to contain solid sulfur because the discharge capacity and energy density of the nonaqueous electrolyte secondary battery can be improved.
- any known material can be used as long as it is a positive electrode active material capable of occluding and releasing lithium ions.
- a composite oxide represented by Li x MO y (M represents at least one transition metal) (Li x CoO 2 , Li x NiO 2 , Li x Mn 2 O 4 , Li x MnO 3 , Li x Ni y Co (1-y) O 2 , Li x Ni y Mn z Co (1-yz) O 2 , Li x Ni y Mn (2-y) O 4, etc.), or Li w Me x (XO y ) z (Me represents at least one kind of transition metal, and X represents, for example, P, Si, B, V) polyanion compounds (LiFePO 4 , LiMnPO 4 , LiNiPO 4 , LiCoPO 4 , Li 3 V 2 (PO) 4 ) 3 , Li 2 MnSiO 4 ,
- the elements or polyanions in these compounds may be partially substituted with other elements or anion species, and the surface is coated with a metal oxide such as ZrO 2 , MgO, Al 2 O 3 or carbon. Also good. Further, examples thereof include, but are not limited to, conductive polymer compounds such as disulfide, polypyrrole, polyaniline, polyparastyrene, polyacetylene, and polyacene-based materials, pseudographite-structured carbonaceous materials, and simple sulfur. Moreover, these compounds may be used independently and may mix and use 2 or more types.
- the conductive agent is not limited as long as it is an electron conductive material that does not adversely affect the battery performance.
- natural graphite scale-like graphite, scale-like graphite, like-like graphite
- artificial graphite carbon black
- acetylene black Use of one or a mixture of two or more conductive materials such as ketjen black, carbon whisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) powder, metal fiber, and conductive ceramic material it can.
- acetylene black is preferable from the viewpoints of electron conductivity and coatability.
- the addition amount of the conductive agent is preferably 0.1% by mass to 50% by mass and more preferably 0.5% by mass to 30% by mass with respect to the total mass of the positive electrode mixture layer. It is preferable to use acetylene black by pulverizing it into ultrafine particles of 0.1 to 0.5 ⁇ m because the necessary carbon amount can be reduced.
- binders generally used for non-aqueous electrolyte secondary batteries can be used.
- thermoplastic resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene, and polypropylene
- PTFE polytetrafluoroethylene
- PVDF polyvinylidene fluoride
- EPDM ethylene-propylene-diene terpolymer
- SBR styrene butadiene rubber
- fluororubber ethylene-propylene-diene terpolymer
- the addition amount of the binder is preferably 1 to 50% by mass, and more preferably 2 to 30% by mass with respect to the total mass of the positive electrode mixture layer.
- the thickener examples include polysaccharide polymers such as carboxymethylcellulose (CMC) and methylcellulose.
- CMC carboxymethylcellulose
- methylcellulose a functional group that reacts with lithium
- the filler is not particularly limited as long as it does not adversely affect the battery performance.
- the main component of the filler include polyolefins such as polypropylene and polyethylene, silica, alumina, zeolite, and glass.
- the negative electrode according to the present embodiment includes a negative electrode substrate and a negative electrode mixture layer disposed on the negative electrode substrate directly or via an intermediate layer.
- the negative electrode mixture layer includes a negative electrode active material and a binder.
- the negative electrode mixture layer may contain a conductive agent, a thickener, a filler, and the like as necessary.
- the intermediate layer of the negative electrode can be the same as the intermediate layer of the positive electrode described above.
- the negative electrode active material used for the negative electrode mixture layer is not particularly limited as long as it is a substance capable of electrochemically occluding and releasing lithium ions, and a known material can be appropriately used.
- Examples thereof include carbonaceous materials, metal oxides such as tin oxide and silicon oxide, metal composite oxides, lithium alloys such as lithium alone and lithium aluminum alloys, and metals that can form alloys with lithium such as Sn and Si.
- Examples of the carbonaceous material include graphite (graphite), cokes, non-graphitizable carbon, graphitizable carbon, fullerene, carbon nanotube, carbon black, activated carbon and the like.
- graphite is preferable as a negative electrode active material because it has an operating potential very close to that of metallic lithium and can realize charge and discharge at a high operating voltage.
- artificial graphite and natural graphite are preferable.
- graphite in which the surface of the negative electrode active material particles is modified with amorphous carbon or the like is desirable because it generates less gas during charging.
- These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio.
- carbonaceous materials or lithium composite oxides are preferably used from the viewpoint of safety.
- the various binders described above can be used.
- the negative mix layer may contain the above-mentioned electrically conductive agent, a thickener, a filler, etc.
- the negative electrode substrate in addition to copper, nickel, iron, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al—Cd alloy, etc., adhesion, conductivity, reduction resistance
- a surface of copper or the like treated with carbon, nickel, titanium, silver or the like can be used.
- a film shape, a sheet shape, a net shape, a punched or expanded material, a lath body, a porous body, a foamed body, a formed body of fiber groups, and the like are used in addition to the foil shape.
- the thickness is not particularly limited, but a thickness of 1 to 500 ⁇ m is used.
- the cation exchange resin layer serves as a separator that insulates the positive electrode from the negative electrode.
- the cation exchange resin layer contains a cation exchange resin.
- the cation exchange resin include polyacrylic acid, polymethacrylic acid, polyvinylbenzenesulfonic acid, polybenzenemethanesulfonic acid, and polyacrylamide-2-methyl-1-propanesulfonic acid.
- a cation exchange resin can be obtained by introducing a sulfonic acid group (—SO 3 H), a carboxylic acid group (—COOH), or a hydroxyl group (—OH) into various resins.
- Examples of the various resins include perfluorocarbon resins, aromatic polyether ketone resins, polyphenylene sulfide resins, polyether sulfone resins, polyphenylene oxide resins, and polybenzimidazole resins.
- a perfluorocarbon sulfonic acid resin in which a sulfonic acid group is introduced into the perfluorocarbon resin is preferable because high ion conductivity is obtained.
- the form in which the cation exchange resin layer contains the cation exchange resin is not particularly limited.
- a cation exchange membrane in which a cation exchange resin is formed into a film may be used, or a commercially available ion exchange membrane may be used. Specific examples include Nafion membrane (trade name, manufactured by DuPont), Flemion (trade name, manufactured by Asahi Glass Co., Ltd.), Aciplex (trade name, manufactured by Asahi Kasei Co., Ltd.), and the like.
- the cation exchange resin layer may be formed by filling the inside of the porous structure of the porous layer with a cation exchange resin.
- the filling method is not particularly limited, and examples thereof include a spray method, a dispensing method, a dipping method, and a blade coating method.
- the cation exchange resin layer does not have pores communicating from one surface to the other surface, that is, is non-porous. By being non-porous, the positive electrode electrolyte and the negative electrode electrolyte are not mixed, and the possibility that the lithium polysulfide reaches the negative electrode is reduced. Note that at least one surface may have pores or irregularities that do not communicate with the other surface.
- a commercially available cation exchange resin or cation exchange membrane is a proton (H + ) type in which a proton is bonded to an anionic functional group.
- H + proton
- a cation exchange resin or a cation exchange membrane When applying a cation exchange resin or a cation exchange membrane to a non-aqueous electrolyte secondary battery, it is preferable to replace the H + type with a lithium (Li + ) type.
- the substitution to the Li + type is performed by immersing the separator in an aqueous lithium hydroxide solution. After immersion, the separator is washed with deionized water at 25 ° C. until the washing water becomes neutral.
- the temperature of the lithium hydroxide aqueous solution is preferably 70 to 90 ° C., and the immersion time is preferably 2 to 6 hours.
- the cation exchange resin layer preferably contains a non-aqueous solvent for the conduction of lithium ions therein.
- a non-aqueous solvent contained in the cation exchange resin layer various non-aqueous solvents that can be used for a positive electrode electrolyte or a negative electrode electrolyte described later can be appropriately used.
- a cation exchange resin layer not containing a non-aqueous solvent may be applied to a non-aqueous electrolyte secondary battery as it is, but some cation exchange resins have a low swelling property of a non-aqueous solvent (or non-aqueous electrolyte). Therefore, it is preferable to perform the swelling treatment with a non-aqueous solvent in advance before battery production.
- the swelling treatment is performed by immersing the cation exchange resin layer substituted with the Li + type in a non-aqueous solvent.
- the swelling treatment time is preferably 12 to 48 hours.
- the amount of the non-aqueous solvent contained in the cation exchange resin layer may be 30% by mass or less based on the cation exchange resin layer.
- a method for adjusting the mass of the nonaqueous solvent contained in the cation exchange resin layer it may be performed by using a nonaqueous solvent with low impregnation into the cation exchange resin, or a nonaqueous solvent in which the cation exchange resin is immersed. You may carry out the quantity of 30 mass% or less previously with respect to the quantity of a cation exchange resin.
- Examples of the solvent having low impregnation property to the cation exchange resin layer include 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane, methyl diglyme, dimethyl ether, diethyl
- examples include ethers such as ether, chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, and cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate.
- the nonaqueous solvent used for the positive electrode electrolyte or the negative electrode electrolyte described later can be appropriately used.
- Examples of the material constituting the porous layer include polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polybutylene terephthalate, polyvinylidene fluoride, and vinylidene fluoride-hexafluoropropylene.
- Polymer vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride- Hexafluoroacetone copolymer, vinylidene fluoride-ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoro Ethylene - hexafluoropropylene copolymer, vinylidene fluoride - ethylene - can be used tetrafluoroethylene copolymer.
- the nonaqueous solvent used for the positive electrode electrolyte and the negative electrode electrolyte is not limited, and those generally proposed for use in lithium secondary batteries and the like can be used.
- the non-aqueous solvent include cyclic carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, and vinylene carbonate; cyclic esters such as ⁇ -butyrolactone and ⁇ -valerolactone; dimethyl carbonate, diethyl carbonate, Chain carbonates such as ethyl methyl carbonate; chain esters such as methyl formate, methyl acetate and methyl butyrate; tetrahydrofuran or derivatives thereof; 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1 Ethers such as 1,4-dibutoxyethane and methyldiglyme; nitriles such as acetonitrile and benzonitrile; diox
- the positive electrode electrolyte or the negative electrode electrolyte may contain an additive.
- an electrolyte additive generally used for a nonaqueous electrolyte secondary battery can be used.
- aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenylether, dibenzofuran; 2-fluorobiphenyl, o-cyclohexylfluorobenzene , Fluorinated anisole compounds such as 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, and 3,5-difluoroanisole; Cyclic hydrocarbons such as vinylene carbonate, methyl vinylene carbonate, ethyl vinylene carbonate, fluoroethylene carbonate, difluoro
- electrolyte salt contained in the positive electrode electrolyte or the negative electrode electrolyte known electrolyte salts can be appropriately used.
- An inorganic ion salt containing one of sodium (Na) or potassium (K) LiCF 3 SO 3 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , LiN (CF 3 SO 2) (C 4 F 9 SO 2), LiC (CF 3 SO 2) 3, LiC (C 2 F 5 SO 2) 3, (CH 3) 4 NBF 4, (CH 3) 4 NBr, (C 2 H 5) 4 NClO 4, (C 2 H 5) 4 NI, (C 3 H 7) 4 NBr, (n-C 4 H 9) 4
- the viscosity of the electrolyte can be lowered.
- the performance can be improved, and self-discharge can be suppressed, which is more preferable.
- the non-aqueous electrolyte may be a room temperature molten salt or ionic liquid.
- the nonaqueous electrolyte secondary battery according to this embodiment is manufactured by the following method.
- the manufacturing method includes, for example, (1) a step of producing a positive electrode, (2) a step of producing a negative electrode, (3) a step of preparing a positive electrode electrolyte and a negative electrode electrolyte, and (4) a first surface of a cation exchange resin layer.
- a step of performing a roughening treatment (5) a step of immersing the cation exchange resin layer in a nonaqueous electrolyte or a nonaqueous solvent, (6) a step of injecting a positive electrode electrolyte between the positive electrode and the cation exchange resin layer, (7 ) A step of injecting a negative electrode electrolyte between the negative electrode and the cation exchange resin layer, and (8) forming an electrode group in which the positive electrode and the negative electrode are alternately superimposed by laminating or winding the cation exchange resin layer.
- a step, (9) a step of accommodating the positive electrode and the negative electrode (electrode group) in the battery case (case), and (10) a step of sealing the opening of the battery case.
- the steps (1) to (4) may be performed in any order, and the steps (6) to (8) may be performed simultaneously or sequentially.
- non-aqueous electrolyte secondary battery of the present embodiment for example, a non-aqueous electrolyte secondary battery 1 (lithium ion secondary battery) shown in FIG.
- the nonaqueous electrolyte secondary battery 1 includes a container 3, a positive electrode terminal 4, and a negative electrode terminal 5, and the container 3 is a container main body and an upper wall that accommodate the electrode group 2 and the like. And a cover plate.
- an electrode group 2, a positive electrode lead 4 ', and a negative electrode lead 5' are arranged inside the container body.
- the positive electrode is electrically connected to the positive electrode terminal 4 via the positive electrode lead 4 ', and the negative electrode is electrically connected to the negative electrode terminal 5 via the negative electrode lead 5'. Note that although the positive electrode is impregnated with the positive electrode electrolyte and the negative electrode is impregnated with the negative electrode electrolyte, the illustration of the liquid is omitted.
- the electrode group 2 includes a positive electrode, a negative electrode, and a separator, and can store electricity. Specifically, as shown in FIG. 2, the electrode group 2 is formed in a layered manner so that the separator 25 is sandwiched between the negative electrode 23 and the positive electrode 21.
- the electrode group 2 includes a positive electrode electrolyte 22 between the positive electrode 21 and the separator 25, and includes a negative electrode electrolyte 24 between the negative electrode 23 and the separator 25.
- the positive electrode electrolyte 22 and the negative electrode electrolyte 24 may be the same or different.
- the separator 25 includes a cation exchange resin layer 25a having a first surface 25c and a second surface 25d and a porous layer 25b, and the first surface 25c and the porous layer 25b are in contact with each other.
- the roughness factor of the first surface 25c of the cation exchange resin layer 25a is 3 or more.
- the positive electrode electrolyte 22 is disposed between the positive electrode 21 and the porous layer 25b, and the negative electrode electrolyte 24 is disposed between the negative electrode 23 and the cation exchange resin layer 25a.
- the positive electrode electrolyte 22 is impregnated in the positive electrode 21 and the porous layer 25b, and the negative electrode electrolyte 24 is impregnated in the negative electrode 23, in a normal battery, the positive electrode 21 is in contact with the porous layer 25b, and the negative electrode 23 is It is in contact with the cation exchange resin layer 25a. That is, in the battery, the positive electrode 21, the porous layer 25b, the cation exchange resin layer 25a, and the negative electrode 23 are laminated in this order.
- the separator 25 has a structure in which a cation exchange resin layer 25a having a first surface 25c and a porous layer 25b are laminated.
- the first surface 25c is in contact with the porous layer 25b.
- the cation exchange resin layer 25a contains a cation exchange resin and suppresses the lithium polysulfide Li 2 S x (4 ⁇ x ⁇ 8) produced at the positive electrode 21 and / or contained in the positive electrode electrolyte 22 from reaching the negative electrode. To do. For this reason, the lithium polysulfide produced at the positive electrode 21 and / or contained in the positive electrode electrolyte 22 is prevented from reaching the negative electrode, and the shuttle phenomenon is suppressed.
- the positive electrode, the porous layer, the cation exchange resin layer, and the negative electrode are arranged in this order, and the roughness factor of the surface in contact with the porous layer, which is the first surface of the cation exchange resin layer
- the roughness factor of the surface in contact with the negative electrode, which is the second surface may be 3 or more. That is, the roughness factors of the first surface and the second surface of the cation exchange resin layer may be 3 or more, respectively.
- the positive electrode, the cation exchange resin layer, the porous layer, and the negative electrode may be arranged in this order, and the roughness factor of the surface of the cation exchange resin layer in contact with the porous layer may be 3 or more.
- the interface resistance of a cation exchange resin layer and a porous layer can be made low.
- the cation exchange resin layer and the porous layer are formed as a single layer, but a plurality of cation exchange resin layers or porous layers may be provided.
- the first surface having a roughness factor of 3 or more may be provided in all the cation exchange resin layers, but may be provided in at least one cation exchange resin layer. This is because the interfacial resistance of the cation exchange resin layer can be lowered and the high rate discharge performance of the battery can be improved.
- the configuration of the nonaqueous electrolyte secondary battery according to the present invention is not particularly limited, and examples thereof include a cylindrical battery, a square battery (rectangular battery), a flat battery, and the like. It is good also as an electrical storage apparatus provided with two or more said nonaqueous electrolyte secondary batteries.
- a power storage device is shown in FIG. In FIG. 3, the power storage device 100 includes a plurality of power storage units 20. Each power storage unit 20 includes a plurality of nonaqueous electrolyte secondary batteries 1.
- the power storage device 100 can be mounted as a power source for vehicles such as an electric vehicle (EV), a hybrid vehicle (HEV), a plug-in hybrid vehicle (PHEV), and the like.
- Example 1-1 As a cation exchange membrane, both sides of a 50 ⁇ m-thick Nafion membrane (manufactured by Sigma-Aldrich) were roughened using a P320 sandpaper having a grain size of abrasive material for abrasive cloth of 320 ⁇ m as defined in JIS R 6010: 2000. Surface treatment. The number of times of sandpaper polishing was 80 per side. This membrane is used as the cation exchange membrane of Example 1-1.
- Example 1-2 The Nafion film was roughened in the same manner as in Example 1-1 except that P400 sandpaper was used. This membrane is used as the cation exchange membrane of Example 1-2.
- Example 1-3 The Nafion membrane was roughened in the same manner as in Example 1-1 except that P1000 sandpaper was used. This membrane is used as the cation exchange membrane of Example 1-3.
- Example 1-4 was carried out in the same manner as Example 1-3, except that the number of times of polishing with sandpaper was changed and the roughness factor, arithmetic average roughness Ra, and maximum height roughness Rz were changed to the values shown in Table 1.
- a cation exchange membrane of ⁇ 1-6 was prepared.
- the obtained Li + -type cation exchange membrane was mixed with a mixed solvent in which 1,2-dimethoxyethane (DME) and 1,3-dioxolane (DOL) were mixed at a volume ratio of 50:50 at 25 ° C. for 12 hours. Impregnation treatment was performed by dipping. By this treatment, the cation exchange membrane after the impregnation treatment was impregnated with 20% by mass of a mixed solvent with respect to the mass of the cation exchange membrane before the impregnation treatment. The thickness of the cation exchange membrane before and after the impregnation treatment was 50 ⁇ m and 64 ⁇ m, respectively.
- a resistance measurement cell 30 was produced using the cation exchange membrane of each Example and Comparative Example after the impregnation treatment and an electrochemical measurement cell 31 (manufactured by Nippon Tomcell Co., Ltd.) as shown in FIG.
- a stainless steel plate electrode 31e and a porous membrane (porous layer) 36 sandwich a cation exchange resin layer 35 inside an O-ring 31f having an inner diameter of 26 mm and an outer diameter of 34 mm provided on a stainless steel plate support 31a. Laminated.
- the resistance measurement cell 30 was assembled by stacking a stainless steel plate lid 31b on the laminate and fastening a bolt 31c and a nut 31d.
- the microporous membrane 36 made of polyethylene includes a non-aqueous electrolyte containing 0.3 mol / l lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) and mixing DME and DOL at 50:50 (volume ratio). Impregnated.
- LiTFSI lithium bis (trifluoromethanesulfonyl) imide
- the electrolyte layer resistance R was measured by AC impedance measurement.
- the AC impedance measurement was performed at an applied voltage amplitude of 5 mV and a frequency of 1 MHz to 100 mHz.
- a Nyquist diagram of the measurement results was prepared, and fitting was performed using an equivalent circuit. The value on the low frequency side of the intersection of the curve and the real axis fitted with the arc appearing on the highest frequency side was read and used as the electrolyte resistance R.
- the electrolyte layer resistance R includes a porous layer resistance Re that is the resistance of the polyethylene microporous membrane 36, an interface resistance Ri that is a resistance at the interface between the polyethylene microporous membrane 36 and the cation exchange membrane 35 after the impregnation treatment, and an impregnation treatment.
- a cation exchange resin layer resistance Rc which is the resistance of the subsequent cation exchange membrane 35, is included and is represented by the following formula (1).
- R 2Re + 2Ri + Rc (1)
- the interface resistance Ri was calculated using the formula (1).
- the concentration of LiTFSI in the electrolyte solution impregnated in the polyethylene microporous membrane was changed to the value shown in Table 2, and the AC impedance measurement was performed using the cation exchange membranes of the Examples and Comparative Examples after the impregnation treatment, and the interface The resistance Ri was calculated.
- the LiTFSI concentration was 0.5 mol / l, only Examples 1-1 to 1-3 and Comparative Example 1-1 were measured.
- the sulfur conversion concentration of lithium polysulfide in the electrolyte solution impregnated in the polyethylene microporous membrane was 3.0 mol / l, and the concentration of LiTFSI was The impedance was changed to the values shown in Table 3, AC impedance measurement was performed, and the interface resistance Ri was calculated.
- the electrolyte solution containing lithium polysulfide was produced as follows. In a glove box having a dew point of ⁇ 50 ° C. or less, DME and lithium polysulfide (Li 2 S) and sulfur (S 8 ) are in a stoichiometric ratio (molar ratio 8: 5) that Li 2 S 6 can generate.
- Table 1 shows the roughness factor, arithmetic average roughness Ra, and maximum height roughness Rz of the cation exchange membrane of each Example and Comparative Example, and the concentrations of the cation exchange membrane, LiTFSI and lithium polysulfide after impregnation were changed.
- Tables 2 and 3 show the interfacial resistance Ri with the polyethylene microporous membrane containing the electrolytic solution at the time.
- divided the interface resistance of Examples 1-1 to 1-6 by the interface resistance of the comparative example 1-1 with respect to roughness factor, arithmetic mean roughness Ra, and maximum height roughness Rz is a figure. Shown in 6-8.
- the concentration of LiTFSI when the concentration of LiTFSI is as low as 0.3 mol / l, in Examples 1-1 to 1-4 where the maximum height roughness on the surface of the cation exchange membrane is 10 ⁇ m or more, the maximum height roughness is 10 ⁇ m. It was found that the interface resistance was lower than those in Examples 1-5 and 1-6, which are less than the above.
- the concentration of LiTFSI when the concentration of LiTFSI is as high as 1.0 mol / l, Examples 1-1 to 1-3 and Examples 1-5 and 1-6, in which the arithmetic average roughness Ra is 0.5 ⁇ m or more, Compared with Example 1-4 in which the arithmetic average roughness Ra is less than 0.5 ⁇ m, the interface resistance was low. As shown in Table 3, it was found that even when lithium polysulfide was included, the interface resistance was lowered by roughening the surface of the cation exchange membrane.
- Example 2-1 Magnesium citrate was carbonized at 900 ° C. under an argon atmosphere for 1 hour, and then immersed in a 1 mol / l sulfuric acid aqueous solution to extract MgO. Subsequently, washing and drying were performed to obtain porous carbon. This porous carbon and sulfur were mixed at a mass ratio of 30:70. The mixture was sealed in a sealed container under an argon atmosphere, heated to 150 ° C. at a heating rate of 5 ° C./min, held for 5 hours, and then allowed to cool to 80 ° C. Thereafter, the temperature was raised again to 300 ° C. at a heating rate of 5 ° C./min, and heat treatment was performed for 2 hours to obtain a carbon-sulfur composite (hereinafter also referred to as “SPC composite”).
- SPC composite carbon-sulfur composite
- Positive electrode paste using SPC composite as positive electrode active material, acetylene black as conductive agent, and polyvinylidene fluoride (PVDF) as binder at a mass ratio of 85: 5: 10, and using N-methylpyrrolidone (NMP) as a solvent was made.
- the obtained positive electrode paste was filled in a nickel mesh current collector and dried to prepare a positive electrode plate.
- the coating amount of the positive electrode paste was 1.2 mg / cm 2 .
- a metal foil was attached to a copper foil having a thickness of 10 ⁇ m so that the total thickness of the negative electrode was 310 ⁇ m.
- a Nafion membrane which was subjected to a roughening treatment on only one side using a P400 sandpaper, was used.
- the positive electrode electrolyte a solution containing 3.0 mol / l of lithium polysulfide in terms of sulfur and mixed with DME and DOL at a volume ratio of 50:50 was used.
- a test cell 40 was produced using an electrochemical measurement cell 41 (manufactured by Nippon Tomcell) as shown in FIG.
- the positive electrode 43 produced as described above is placed inside an O-ring 41f having an inner diameter of 26 mm and an outer diameter of 34 mm provided on a stainless steel plate support 41a.
- a porous membrane (porous layer) 46 impregnated with the positive electrode electrolyte After laminating a porous membrane (porous layer) 46 impregnated with the positive electrode electrolyte, a cation exchange resin layer 45 having a size larger than the inner diameter of the O-ring was disposed. At this time, the cation exchange resin layer 45 was disposed so that the first surface 45 a subjected to the roughening treatment was in contact with the porous membrane 46.
- a negative electrode 44 impregnated with the negative electrode electrolyte was laminated thereon.
- a test cell 40 (hereinafter also referred to as a “battery”) is formed by disposing a stainless steel plate electrode 41e on the negative electrode 44, and overlapping a stainless steel plate lid 41b and fastening a bolt 41c and a nut 41d. Assembled. This is designated as Example Battery 2-1.
- Comparative Example 2-1 A test cell 30 according to Comparative Example 2-1 was produced in the same manner as in Example 2-1, except that a Nafion membrane that had not been roughened was used as the cation exchange membrane. This is designated as Comparative Example Battery 2-1.
- Example battery 2-1 and Comparative example battery 2-1 are measured by the following method, and the 0.2 C discharge capacity is divided by the 0.1 C discharge capacity. Thus, a 0.2C / 0.1C ratio (%) was calculated.
- a 0.1 C constant current discharge up to 1.5 V at 25 ° C. and a 0.1 C constant current charge up to 3.0 V were performed.
- the charge and discharge termination conditions were set until the set voltage was reached or 10 hours had passed.
- the above-described 0.1 C discharging and charging step was set as one cycle, and this cycle was repeated three times.
- a value obtained by dividing the discharge capacity at the third cycle by the mass of the SPC composite was taken as 0.1 C discharge capacity (mAh / g).
- 1C is a current value at which the capacity of the positive electrode active material is discharged in one hour when the capacity per mass of the SPC composite used as the positive electrode active material is set to 1675 mAh / g which is a theoretical capacity.
- 0.2C constant current discharge to 1.5V and 25C constant current charge to 3.0V were performed at 25 degreeC.
- the charge and discharge termination conditions were until the set voltage was reached or 5 hours had passed.
- the above-described 0.2 C discharging and charging step was set as one cycle, and this cycle was repeated three times.
- a value obtained by dividing the discharge capacity at the third cycle by the mass of the SPC composite was defined as 0.2 C discharge capacity (mAh / g).
- the 0.2C / 0.1C ratio (%) was calculated by dividing the 0.2C discharge capacity by the 0.1C discharge capacity.
- Table 4 shows the 0.1 C discharge capacity, 0.2 C discharge capacity, and 0.2 C / 0.1 C ratio (%) of Example Battery 2-1 and Comparative Example Battery 2-1.
- FIG. 9 shows discharge curves of 0.1 C and 0.2 C of Example battery 2-1 and Comparative example battery 2-1.
- Example Battery 2-1 exhibited a high discharge capacity of 1150 mAh / g at both discharge currents of 0.1 C and 0.2 C, and the ratio of 0.2 C / 0.1 C was 100%.
- the comparative battery 2-1 had a 0.1C discharge capacity equivalent to that of the example battery 2-1, but the 0.2C discharge capacity was low, and the 0.2C / 0.1C ratio was 71.7. %Met. This is presumably because, in Example Battery 2-1, the cation exchange membrane whose surface was roughened was used as the cation exchange resin layer, so that the interface resistance was lowered and the high rate discharge performance was improved.
- Example Battery 2-1 as shown in FIG.
- a non-aqueous electrolyte secondary battery excellent in high-rate discharge performance can be obtained, so that it is useful as a secondary battery for a wide range of uses such as in-vehicle use and stationary use.
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Abstract
Description
しかしながら、充放電中に正極で生成したリチウム多硫化物(Li2Sn、4≦n≦8)が非水電解質に溶出し、負極に到達して還元されることにより自己放電が進行するシャトル現象が課題となっている。シャトル現象を抑制するために、正極と負極との間にカチオン交換樹脂層を配置する技術が知られている。(特許文献1~3、非特許文献1、2)。
本実施形態におけるカチオン交換樹脂層の第一面は、JIS B 0601:2013に規定される算術平均粗さRaが、好ましくは0.5μm以上、より好ましくは2μm以上である。上記算術平均粗さRaが上記範囲を満たすことにより、カチオン交換樹脂層と正極との界面の抵抗を低減することができる。さらに、カチオン交換樹脂層の強度を維持するために、上記算術平均粗さRaは、10μm以下が好ましく、8μm以下がより好ましく、5μm以下がさらに好ましい。
・測定機器:超深度形状測定顕微鏡VK-8500(キーエンス社製)
・測定範囲:1.04×10-3 cm2
・形状解析アプリケーション:VK-H1A9(キーエンス社製)
通常、正極及び負極の表面は、粒子状の活物質に由来する凹凸を有している。そのため、柔軟性が低いカチオン交換樹脂層を用いた場合、粗面化した第一面と正極又は負極との接触面積が、粗面化していない場合に比べて低下する虞がある。ポリマーを含む多孔質層は、カチオン交換樹脂層に比べて柔軟性に優れているため、多孔質層がカチオン交換樹脂層の第一面に接していることで、正極-多孔質層-カチオン交換樹脂層の第一面間、又は負極-多孔質層-カチオン交換樹脂層の第一面間の接触が良好に保たれ、リチウムイオンが良好に伝達される。さらに、多孔質層に非水電解質を保持させることができるので、正極又は負極中での非水電解質の偏在が起こりにくく、正極又は負極での充放電反応を均一化できる。
なお、多孔質層は、正極とカチオン交換樹脂層の第一面との間のみに設けられてもよいし、負極とカチオン交換樹脂層の第一面との間のみに設けられてもよい。あるいは、正極とカチオン交換樹脂層の間及び負極とカチオン交換樹脂層の間の両方に、多孔質層を設けてもよい。
カチオン交換樹脂が、正極及び負極の少なくとも一方に含まれることにより、カチオン交換樹脂層と正極活物質又は負極活物質との間にカチオン交換樹脂からなるリチウム伝導パスが形成される。すなわち、リチウムイオンは、非水電解質を経由することなく、カチオン交換樹脂層と正極活物質又は負極活物質との間を行き来できることから、カチオン交換樹脂層の界面抵抗を小さくすることができる。これにより、高い放電容量と優れた充放電サイクル性能を有する非水電解質二次電池を得ることができると推測される。
負極合剤層内部にカチオン交換樹脂が含まれている負極も、上述の方法により作製できる。
正極電解質及び負極電解質の少なくとも一方に含まれるアニオンの濃度の上限は、0.7mol/lが好ましく、0.5mol/lがより好ましく、0.3mol/lがさらに好ましい。正極電解質に含まれるアニオンの濃度の上限は、0.3mol/lが好ましく、0.2mol/lがより好ましく、0mol/lであってもよい。アニオンの濃度が上記上限以下であることにより、非水電解質の粘度を下げることが可能となり、放電容量が高く、充放電サイクル性能に優れた非水電解質二次電池を得ることができる。
正極合剤層は、固体状態の硫黄を含まなくてもよい。この場合、正極合剤層は導電剤及び結着剤のみを含有し、正極電解質中のリチウム多硫化物が活物質として充放電に寄与する。固体状硫黄を含有することで、非水電解質二次電池の放電容量及びエネルギー密度を向上させられるため、好ましい。
負極基材の形状については、フォイル状の他、フィルム状、シート状、ネット状、パンチ又はエキスパンドされた物、ラス体、多孔質体、発泡体、繊維群の形成体等が用いられる。厚みの限定は特にないが、1~500μmのものが用いられる。
高いイオン伝導性が得られるため、パーフルオロカーボン樹脂にスルホン酸基を導入したパーフルオロカーボンスルホン酸樹脂が好ましい。
上記(1)~(4)の工程はどのような順序で行ってもよく、(6)~(8)の工程は同時に行っても逐次行ってもよい。
なお、図2では、正極21と多孔質層25bとの間に正極電解質22が配置され、負極23とカチオン交換樹脂層25aとの間に負極電解質24が配置されている。しかしながら、正極電解質22は、正極21及び多孔質層25bに含浸されており、負極電解質24は負極23に含浸されているため、通常の電池では正極21は多孔質層25bに接し、負極23はカチオン交換樹脂層25aに接している。すなわち、電池内では、正極21、多孔質層25b、カチオン交換樹脂層25a、負極23の順に積層されて配置されている。
カチオン交換膜として、厚み50μmのナフィオン膜(シグマアルドリッチ社製)の両面を、JIS R 6010:2000に規定される研磨布紙用研磨材の粒度が320μmであるP320番のサンドペーパーを用いて粗面化処理した。サンドペーパーによる研磨回数は片面あたり80回とした。この膜を実施例1-1のカチオン交換膜とする。
P400番のサンドペーパーを用いたこと以外は、実施例1-1と同様にしてナフィオン膜の粗面化処理を行った。この膜を実施例1-2のカチオン交換膜とする。
P1000番のサンドペーパーを用いたこと以外は、実施例1-1と同様にしてナフィオン膜の粗面化処理を行った。この膜を実施例1-3のカチオン交換膜とする。
サンドペーパーによる研磨回数を変更し、ラフネスファクター、算術平均粗さRa及び最大高さ粗さRzを表1に示す値としたこと以外は、実施例1-3と同様にして実施例1-4~1-6のカチオン交換膜を作製した。
粗面化処理を行わなかったナフィオン膜を、比較例1-1のカチオン交換膜とする。
次の条件で、実施例1-1~1-6、及び比較例1-1のカチオン交換膜の表面形態観察を行い、ラフネスファクター、算術平均粗さRa、及び最大高さ粗さRzを算出した。
・測定機器:超深度形状測定顕微鏡VK-8500(キーエンス社製)
・測定範囲:1.04×10-3 cm2
・形状解析アプリケーション:VK-H1A9(キーエンス社製)
[2-1.カチオン交換膜の含浸処理]
実施例1-1~1-6、及び比較例1-1のカチオン交換膜を、1mol/lの水酸化リチウムの水/アルコール溶液に浸漬し、80℃で12時間撹拌することにより、カチオン交換膜中のプロトンをリチウムイオンに交換した。撹拌後の各実施例及び比較例のカチオン交換膜は、脱イオン水で洗浄し、120℃の脱気下で乾燥することにより、水酸化リチウム及び溶媒の除去を行った。
得られたLi+型カチオン交換膜を、1,2-ジメトキシエタン(DME)と1,3-ジオキソラン(DOL)とを体積比50:50で混合した混合溶媒に、25℃環境下で12時間浸漬することにより、含浸処理を行った。この処理により、含浸処理後のカチオン交換膜には、含浸処理前のカチオン交換膜の質量に対して20質量%の混合溶媒が含浸された。含浸処理前後のカチオン交換膜の厚みは、それぞれ50μm、64μmであった。
含浸処理後の各実施例及び比較例のカチオン交換膜、及び図4に示すような電気化学測定用セル31(日本トムセル社製)を用いて、抵抗測定用セル30を作製した。ステンレス鋼板製支持体31aに設けられた内径26mm、外径34mmのO-リング31fの内側に、ステンレス鋼板製電極31e及び多孔質膜(多孔質層)36が、カチオン交換樹脂層35を挟み込む形で積層した。積層体上に、ステンレス鋼板製蓋体31bを重ねてボルト31cとナット31dとを締結することにより、抵抗測定用セル30を組み立てた。なお、ポリエチレン製微多孔膜36には、0.3mol/lのリチウムビス(トリフルオロメタンスルホニル)イミド(LiTFSI)を含み、DMEとDOLとを50:50(体積比)で混合した非水電解質が含浸されている。
R=2Re+2Ri+Rc (1)
0.3mol/lのLiTFSIを含むDME:DOL=50:50(体積比)の電解液が含浸されたポリエチレン製微多孔膜を配置しないこと以外は[2-2.電解質層抵抗Rの測定]と同様にして、交流インピーダンス測定を行った。この測定により求められた抵抗を、カチオン交換樹脂層抵抗Rcとした。
含浸処理後のカチオン交換膜を配置せずに、0.3mol/lのLiTFSIを含むDME:DOL=50:50(体積比)の電解液が含浸されたポリエチレン製微多孔膜1枚のみを配置したこと以外は[2-3.カチオン交換樹脂層抵抗Rcの測定]と同様にして、交流インピーダンス測定を行った。この測定により求められた抵抗を、多孔質層抵抗Reとした。
なお、リチウム多硫化物を含む電解液は次のようにして作製した。露点-50℃以下のグローブボックス内で、リチウム多硫化物(Li2S)と硫黄(S8)をLi2S6が生成し得る量論比(モル比8:5)にて、DMEとDOLとを体積比50:50で混合した非水溶媒に投入し、撹拌した。この溶液を密閉容器に封入し、80℃の恒温槽内に4日間静置することにより、Li2SとS8とを反応させ、リチウム多硫化物を含む溶液を作製した。このリチウム多硫化物溶液には、硫黄に換算した場合3.0mol/lに相当するリチウム多硫化物が溶解している。この溶液に、LiTFSIの濃度が0、0.3、0.5又は1.0mol/lとなるようにLiTFSIを溶解させて、リチウム多硫化物を含む電解液を作製した。
表3に示した通り、リチウム多硫化物を含む場合であっても、カチオン交換膜表面を粗面化することにより、界面抵抗は低下することがわかった。
(実施例2-1)
クエン酸マグネシウムを900℃、アルゴン雰囲気下で1時間炭化処理したのち、1mol/lの硫酸水溶液中に浸漬することによって、MgOを抽出した。続いて、洗浄及び乾燥して、多孔性カーボンを得た。この多孔性カーボンと硫黄とを質量比30:70で混合した。この混合物を、アルゴン雰囲気下で密閉容器に封入し、昇温速度5℃/分で150℃まで昇温し、5時間保持した後、80℃まで放冷した。その後、再び昇温速度5℃/分で300℃まで昇温し、2時間保持する熱処理を行い、カーボン-硫黄複合体(以下、「SPC複合体」ともいう)を得た。
カチオン交換膜として粗面化処理を行っていないナフィオン膜を用いたこと以外は、実施例2-1と同様にして比較例2-1に係る試験用セル30を作製した。これを、比較例電池2-1とする。
25℃で1.5Vまでの0.1C定電流放電、及び3.0Vまでの0.1C定電流充電を行った。充電及び放電の終止条件は、設定電圧に到達するか10時間経過するまでとした。上記0.1Cの放電及び充電の工程を1サイクルとして、このサイクルを3サイクル繰り返した。3サイクル目の放電容量をSPC複合体の質量で除した値を、0.1C放電容量(mAh/g)とした。
なお、1Cは、正極活物質として用いたSPC複合体の質量あたりの容量を、理論容量である1675mAh/gとしたときに、正極活物質の容量を1時間で放電する電流値とした。
次に、25℃で1.5Vまでの0.2C定電流放電、及び3.0Vまでの0.2C定電流充電を行った。充電及び放電の終止条件は、設定電圧に到達するか5時間経過するまでとした。上記0.2Cの放電及び充電の工程を1サイクルとして、このサイクルを3サイクル繰り返した。3サイクル目の放電容量をSPC複合体の質量で除した値を、0.2C放電容量(mAh/g)とした。0.2C放電容量を0.1C放電容量で除することにより、0.2C/0.1C比(%)を算出した。
なお、実施例電池2-1では、図9(a)に示したように、正極活物質層中の硫黄の容量に相当する1150mAh/g放電後にも、放電電位は低下しなかった。一方、比較例電池2-1では、図9(b)に示したように、放電末期に放電電位が低下する現象が観測された。これは、粗面化処理によってカチオン交換樹脂層の界面抵抗が低下したことに起因して、正極表面の電流分布がより均一になったためと考えられる。また、粗面化処理により、正極表面でのリチウム多硫化物の保持性が向上したことに起因して、正極電解液中に含有されるリチウム多硫化物の充放電反応への寄与が高まったためと考えられる。
2 電極群
3 電池容器
4 正極端子
4’ 正極リード
5 負極端子
5’ 負極リード
20 蓄電ユニット
21、43 正極
22 正極電解液
23、44 負極
24 負極電解液
25 セパレータ
25a、35、45 カチオン交換樹脂層
25b、36、46 多孔質層(多孔質膜)
25c、45a 第一面
25d 第二面
30 抵抗測定用セル
31、41 電気化学測定用セル
31a、41a 支持体
31b、41b 蓋体
31c、41c ボルト
31d、41d ナット
31e、41e 電極
31f、41f O-リング
40 試験用セル
100 蓄電装置
Claims (12)
- 硫黄を含む正極と、
負極と、
非水電解質と、
正極と負極との間に配され、ラフネスファクターが3m2/m2以上である第一面を有するカチオン交換樹脂層と、を備える
非水電解質二次電池。 - カチオン交換樹脂層の第一面の算術平均粗さRaが0.5μm以上である
請求項1の非水電解質二次電池。 - カチオン交換樹脂層の第一面の最大高さ粗さRzが5μm以上である
請求項1又は2の非水電解質二次電池。 - さらに多孔質層を備え、多孔質層はカチオン交換樹脂層の第一面に接している、
請求項1~3のいずれかの非水電解質二次電池。 - 非水電解質は、正極電解質と負極電解質とを備え、
正極電解質はリチウム多硫化物を含み、
正極電解質の硫黄換算濃度が負極電解質の硫黄換算濃度よりも高い
請求項1~4のいずれかの非水電解質二次電池。 - 正極電解質の硫黄換算濃度が、1.2mol/l以上である
請求項5の非水電解質二次電池。 - 正極電解質の硫黄換算濃度が、3.0mol/l以上である
請求項6の非水電解質二次電池。 - 正極電解質の硫黄換算濃度が、18mol/l以下である
請求項5~7のいずれかの非水電解質二次電池。 - 正極電解質及び負極電解質の少なくとも一方に含まれるアニオンの濃度が0.7mol/l以下である
請求項5~8のいずれかの非水電解質二次電池。 - 正極電解質に含まれるアニオンの濃度が0.3mol/l以下である
請求項5~9のいずれかの非水電解質二次電池。 - 正極及び負極の少なくとも一方がカチオン交換樹脂を備え、
非水電解質に含まれるアニオンの濃度が0.7mol/l以下である
請求項1~4のいずれかの非水電解質二次電池。 - 硫黄を含む正極と、負極と、正極と負極との間に介在し、ラフネスファクターが3以上である第一面を備えるカチオン交換樹脂層を備えた非水電解質二次電池の製造方法であって、
正極とカチオン交換樹脂層との間に、リチウム多硫化物を含む正極電解質を注入し、負極とカチオン交換樹脂層との間に、正極電解質よりもリチウム多硫化物の濃度が低い負極電解質を注入することを含む
非水電解質二次電池の製造方法。
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| CN202111215600.6A CN114122387B (zh) | 2015-10-14 | 2016-09-30 | 非水电解质二次电池 |
| CN201680059805.0A CN108140899B (zh) | 2015-10-14 | 2016-09-30 | 非水电解质二次电池 |
| US15/766,866 US11196078B2 (en) | 2015-10-14 | 2016-09-30 | Nonaqueous electrolyte secondary battery |
| EP16855099.4A EP3364490B1 (en) | 2015-10-14 | 2016-09-30 | Nonaqueous electrolyte secondary battery |
| US17/517,347 US12107208B2 (en) | 2015-10-14 | 2021-11-02 | Nonaqueous electrolyte secondary battery |
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| CN108878747A (zh) * | 2018-06-13 | 2018-11-23 | 力源(广州)新能源科技有限公司 | 改善锂硫电池性能的功能隔膜及包含该功能隔膜的锂硫电池 |
| WO2020090986A1 (ja) * | 2018-11-01 | 2020-05-07 | 株式会社Gsユアサ | 非水電解液二次電池 |
| CN111902990A (zh) * | 2018-03-29 | 2020-11-06 | 松下知识产权经营株式会社 | 电化学器件 |
| JP2022181107A (ja) * | 2021-05-25 | 2022-12-07 | 旭化成株式会社 | 蓄電デバイスおよび蓄電デバイス用セパレータ |
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| KR102268181B1 (ko) * | 2017-11-21 | 2021-06-22 | 주식회사 엘지화학 | 황-탄소 복합체의 제조방법 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN111902990A (zh) * | 2018-03-29 | 2020-11-06 | 松下知识产权经营株式会社 | 电化学器件 |
| CN108878747A (zh) * | 2018-06-13 | 2018-11-23 | 力源(广州)新能源科技有限公司 | 改善锂硫电池性能的功能隔膜及包含该功能隔膜的锂硫电池 |
| CN108878747B (zh) * | 2018-06-13 | 2021-12-03 | 力源(广州)新能源科技有限公司 | 改善锂硫电池性能的功能隔膜及包含该功能隔膜的锂硫电池 |
| WO2020090986A1 (ja) * | 2018-11-01 | 2020-05-07 | 株式会社Gsユアサ | 非水電解液二次電池 |
| JPWO2020090986A1 (ja) * | 2018-11-01 | 2021-09-24 | 株式会社Gsユアサ | 非水電解液二次電池 |
| JP2024153730A (ja) * | 2018-11-01 | 2024-10-29 | 株式会社Gsユアサ | 非水電解液二次電池 |
| US12463253B2 (en) | 2018-11-01 | 2025-11-04 | Gs Yuasa International Ltd. | Nonaqueous electrolyte solution secondary battery |
| JP2022181107A (ja) * | 2021-05-25 | 2022-12-07 | 旭化成株式会社 | 蓄電デバイスおよび蓄電デバイス用セパレータ |
| JP7570280B2 (ja) | 2021-05-25 | 2024-10-21 | 旭化成株式会社 | 蓄電デバイスおよび蓄電デバイス用セパレータ |
Also Published As
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| EP3364490A1 (en) | 2018-08-22 |
| US10892513B2 (en) | 2021-01-12 |
| US11196078B2 (en) | 2021-12-07 |
| JPWO2017064843A1 (ja) | 2018-08-02 |
| EP3364490A4 (en) | 2019-06-05 |
| EP3364486A4 (en) | 2019-05-22 |
| US12107208B2 (en) | 2024-10-01 |
| CN108140875B (zh) | 2021-02-26 |
| CN108140899A (zh) | 2018-06-08 |
| US20180294506A1 (en) | 2018-10-11 |
| JPWO2017064842A1 (ja) | 2018-08-02 |
| WO2017064842A1 (ja) | 2017-04-20 |
| EP3364486A1 (en) | 2018-08-22 |
| JP6856027B2 (ja) | 2021-04-07 |
| CN114122387B (zh) | 2024-05-31 |
| CN108140875A (zh) | 2018-06-08 |
| CN114122387A (zh) | 2022-03-01 |
| US20180287120A1 (en) | 2018-10-04 |
| EP3364490B1 (en) | 2021-03-03 |
| EP3364486B1 (en) | 2021-02-17 |
| JP6757504B2 (ja) | 2020-09-23 |
| US20220131177A1 (en) | 2022-04-28 |
| CN108140899B (zh) | 2021-11-09 |
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