WO2021189476A1 - 电化学装置 - Google Patents

电化学装置 Download PDF

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WO2021189476A1
WO2021189476A1 PCT/CN2020/081844 CN2020081844W WO2021189476A1 WO 2021189476 A1 WO2021189476 A1 WO 2021189476A1 CN 2020081844 W CN2020081844 W CN 2020081844W WO 2021189476 A1 WO2021189476 A1 WO 2021189476A1
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layer
polymer
porous layer
electrochemical device
inorganic compound
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French (fr)
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张益博
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Priority to CN202080094476.XA priority Critical patent/CN115380430B/zh
Priority to JP2022558294A priority patent/JP2023518890A/ja
Priority to PCT/CN2020/081844 priority patent/WO2021189476A1/zh
Priority to EP20927515.5A priority patent/EP4131628A4/en
Publication of WO2021189476A1 publication Critical patent/WO2021189476A1/zh
Priority to US17/953,811 priority patent/US20230044348A1/en
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    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
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    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the field of electrochemical devices, in particular to a lithium ion battery.
  • Lithium-ion batteries have many advantages, such as high energy density, long cycle life, high nominal voltage (>3.7V), and low self-discharge rate. They are widely used in the field of consumer electronics. With the rapid development of electric vehicles and portable electronic devices in recent years, people have higher and higher requirements for the energy density, safety, and cycle performance of lithium-ion batteries, and are looking forward to the emergence of new lithium-ion batteries with comprehensive performance improvements. . Among them, setting a separator between the positive and negative electrodes of a lithium-ion battery to replace the traditional ordinary separator is a new technology that has attracted much attention.
  • the existing technology of lithium ion batteries without a common isolation film between the positive and negative electrodes is mainly achieved by the method of preparing a polymer layer and/or ceramic layer on the surface of the electrode pole piece by a knife coating method, and its main drawbacks are as follows: The uniformity of the polymer layer is poor, and the weight and thickness of the unit area are quite different; the porosity of the polymer layer is low, which will block the lithium ion transmission path on the surface of the electrode pole piece, resulting in serious deterioration of the rate performance of the lithium ion battery; During the preparation process of the coating method, a large amount of solvents are used, which will damage the active materials and adhesives on the surface of the electrode pads; the ceramic layer and the electrode pads have weak adhesion, which may cause safety hazards. Therefore, it is necessary to develop a new material or structure to replace the traditional isolation membrane.
  • the purpose of this application is to provide an electrochemical device that does not need to use a traditional isolation membrane.
  • the first aspect of the present application provides an electrochemical device, comprising an electrode pole piece and an isolation layer formed on the surface of the electrode pole piece, and the isolation layer includes a porous layer formed on the surface of the electrode pole piece;
  • the porous layer contains nanofibers, and the electrolyte injectability of the isolation layer is 15 seconds or less.
  • the isolation layer has at least one of the following characteristics:
  • the average pore diameter of the porous layer is 20 nm to 10 ⁇ m;
  • the thickness of the isolation layer is 1 ⁇ m to 20 ⁇ m.
  • the diameter of the nanofiber is 0.1 nm to 2 ⁇ m.
  • the nanofibers include polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyphenylene ether, polypropylene carbonate, At least one of polymethyl methacrylate, polyethylene terephthalate, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene, or polyvinylidene fluoride-chlorotrifluoroethylene.
  • the isolation layer further includes a polymer layer disposed on the porous layer; the thickness of the polymer layer is 0.05 ⁇ m to 4 ⁇ m, and the The coverage area ratio of the polymer layer on the porous layer is 10% to 70%.
  • the polymer layer includes a polymer agglomerate, and the polymer agglomerate has at least one of the following characteristics:
  • the maximum coverage area of a single polymer agglomerate in the polymer layer is 1 ⁇ 10 -5 mm 2 ⁇ 1 mm 2 , preferably 0.001 m 2 ⁇ 0.05 mm 2 ;
  • the polymer layer has a regular pattern.
  • the isolation layer further includes an inorganic compound layer, the inorganic compound layer includes inorganic particles, and the inorganic compound layer is disposed on the porous layer.
  • the inorganic compound layer has at least one of the following characteristics:
  • the electronic resistivity of the inorganic compound layer is greater than 10 7 ⁇ m
  • the ionic conductivity of the inorganic compound layer is 10 -8 S/cm to 10 -2 S/cm;
  • the thickness of the inorganic compound layer is 0.1 ⁇ m to 20 ⁇ m;
  • the porosity of the inorganic compound layer is 10% to 40%, and the pore diameter is 0.001 ⁇ m to 8 ⁇ m.
  • the inorganic compound layer is provided by spraying or deposition.
  • the inorganic compound layer and the porous layer are bonded by hot pressing or bonding.
  • the average pore diameter of the porous layer varies in the thickness direction.
  • the average pore diameter of the porous layer in the region closer to the electrode pad is smaller than the average pore diameter in the region further away from the electrode pad.
  • the porous layer is prepared by electrospinning, air spinning or centrifugal spinning.
  • the second aspect of the present application provides an electronic device, which includes the electrochemical device provided by the first party of the present application.
  • a porous layer is provided on the surface of the electrode pole piece (such as the positive pole piece and/or the negative pole piece) to replace the ordinary separation membrane, thereby playing the role of isolating electrons and conducting ions; Furthermore, the porous layer has a small thickness and a strong liquid retention capacity compared with a common isolation membrane, so that the electrochemical device has a higher energy density.
  • Figure 1 is an SEM photograph of the surface of the isolation layer of the electrochemical device in Example 1 (500 times);
  • Example 2 is a SEM photograph of the surface of the isolation layer of the electrochemical device in Example 1 (2000 times);
  • Fig. 3 is an SEM photograph of a cross-section of the isolation layer of the electrochemical device of Example 1; the arrow indicates the polymer agglomerate particles embedded in the porous layer.
  • the electrochemical device of the present application can be any electrochemical device that uses electrode pads and the separator layer of the present application that are well known to those skilled in the art, such as lithium ion batteries, sodium ion batteries, magnesium ion batteries, supercapacitors, etc., as follows Take a lithium ion battery as an example. Those skilled in the art should understand that the following description is only an example and does not limit the protection scope of the present application.
  • the present application provides an electrochemical device, including an electrode pole piece and an isolation layer formed on the surface of the electrode pole piece, the isolation layer includes a porous layer formed on the surface of the electrode pole piece; the porous layer includes nano For fibers, the electrolyte injectability of the separator is 15 seconds or less.
  • electrolyte is injected into a sealed cavity (such as a packaging shell) through a quantitative pump, and the lithium-ion battery is put into the injection chamber, and then the injection chamber is evacuated with a vacuum pump.
  • the interior of the lithium-ion battery is also Create a vacuum environment, then insert the injection nozzle into the injection port of the lithium-ion battery, open the electrolyte injection valve, and pressurize the electrolyte chamber with nitrogen at the same time, hold the pressure for a certain period of time, and then deflate the injection chamber to normal pressure. Finally, let it stand for a long time so that the electrolyte can fully infiltrate the positive pole piece, the negative pole piece and the separator.
  • isolation membranes mainly use polyethylene microporous membranes or polypropylene microporous membranes or a combination of the two, and their liquid injection performance has certain limitations.
  • an isolation layer containing nanofibers is provided on the surface of the electrode pole piece, so that the electrolyte injection performance of the isolation layer can reach less than 15 seconds, which can significantly improve the injection performance of the lithium ion battery.
  • the nanofiber porous layer and the electrode pole piece have good adhesion, which can effectively prevent the separator from being washed by the electrolyte and turning over when the conventional separator is used in the lithium-ion battery during the drop process of the lithium-ion battery. , Thereby improving the safety of lithium-ion batteries.
  • the electrode pole piece mentioned in this application can be a positive pole piece and/or a negative pole piece, and the separation layer can be arranged on the positive pole piece and/or on the negative pole piece to separate the positive pole piece and the negative pole piece; in addition, the separation layer It can be arranged on one surface or both surfaces of the positive pole piece or the negative pole piece, which is not limited in this application.
  • the air permeability when the thickness of the isolation layer is converted to 20 ⁇ m is 5 s/100 cm 3 to 400 s/100 cm 3 .
  • the inventor of the present application found that when the air permeability of the isolation layer is within the above range, the liquid injection property of the isolation layer is significantly improved.
  • the porosity of the isolation layer is 30%-95%.
  • the lithium ion battery of the present application has good liquid injection properties and high ion conductivity.
  • the average pore diameter of the porous layer is 20 nm to 10 ⁇ m.
  • the pore size is less than 20nm, the liquid injection performance decreases and ion conductivity decreases; when the pore size is greater than 10 ⁇ m, the pore size is too large, and the electrode active material in the electrode pad may pass through the isolation layer, short-circuit and cause self-discharge.
  • the thickness of the isolation layer is 1 ⁇ m to 20 ⁇ m; preferably 2 ⁇ m to 18 ⁇ m, more preferably 5 ⁇ m to 15 ⁇ m, and most preferably 8 ⁇ m to 12 ⁇ m.
  • the diameter of the nanofiber is 0.1 nm to 2 ⁇ m.
  • the diameter of the nanofiber is too small, and the strength of the fiber itself is too low.
  • the nanofiber is likely to be disconnected, and the separator is pierced by the electrode active material particles, causing self-discharge; the diameter of the nanofiber is too large , The volume occupied by nanofibers in the isolation layer is too large.
  • the isolation layer contains nanofibers of the same weight, the pore size of the isolation layer may be too large.
  • the isolation layer maintains the same porosity, the content of nanofibers decreases, resulting in The strength of the isolation layer is reduced, and the pore size is too large.
  • the nanofibers include polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyphenylene ether, polypropylene carbonate, polymethyl At least one of polymers such as methyl acrylate, polyethylene terephthalate, polyethylene oxide, polyvinylidene fluoride-hexafluoropropylene, or polyvinylidene fluoride-chlorotrifluoroethylene.
  • the nanofibers comprise lithium ion conductor materials, such as polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyphenylene ether, polypropylene carbonate, poly At least one of ethylene oxide and its derivatives.
  • lithium ion conductor materials such as polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyphenylene ether, polypropylene carbonate, poly At least one of ethylene oxide and its derivatives. These polymers may be used alone or in combination of two or more kinds.
  • the isolation layer further includes a polymer layer, the polymer layer has a thickness of 0.05 ⁇ m to 4 ⁇ m, and the polymer layer covers the nanofiber porous layer with a coverage area ratio of nanofibers. 10% to 70% of the porous layer, preferably 20% to 40%.
  • the polymer layer can increase the mechanical strength of the isolation layer and reduce the K value (the voltage drop of the battery per unit time, mV/d; an indicator of the self-discharge rate of the battery).
  • the polymer layer can cover these pores with larger pore sizes, reducing self-discharge.
  • the polymer layer can also improve the bonding performance of the isolation layer and the electrode pads in contact with its surface. During the winding process of the lithium ion battery, the slip between the separator and the electrode pads is prevented.
  • the polymer layer includes a polymer agglomerate, wherein the single polymer agglomerate refers to an agglomerate formed by agglomeration of one or more polymer secondary particles; it can be understood that the polymer agglomerate may include a plurality of polymer Agglomerates of secondary particles or individual polymer secondary particles.
  • the inventors of the present application have found through in-depth research that, in order to achieve better effects, the maximum coverage area of a single polymer agglomerate is 1 ⁇ 10 -5 mm 2 to 1 mm 2 , preferably 0.001 m 2 to 0.05 mm 2 .
  • the volume of a single polymer agglomerate is too small, the bonding effect of the electrode pads in contact with it is limited, and the ability to improve the pore size of the porous layer is insufficient, that is, it cannot effectively cover the larger pores in the porous nanofiber layer, so it cannot be effective Ground to prevent self-discharge. If the volume of a single polymer agglomerate is too large, it will affect the local ion transmission, resulting in inconsistent charging and discharging of the lithium-ion battery as a whole, leading to a decrease in the cycle capacity and cycle capacity retention rate at a large rate.
  • polymer agglomerates are embedded in the porous layer, as shown in FIG. 3. Embedding the polymer agglomerates in the porous layer can reduce the number of larger pores, that is, reduce the pore diameter, on the other hand, it can make the polymer agglomerates relatively fixed in the porous layer to avoid slippage. In addition, since the polymer agglomerates are embedded in the porous layer, the relative slip between the nanofibers in the porous layer will also be reduced. The inventor of the present application found that the depth of the polymer agglomerates embedded in the porous layer is preferably 0.5-5 ⁇ m, more preferably 1-2 ⁇ m.
  • the embedding depth is too small, it is difficult to effectively fill the pores in the porous layer, the effect of reducing self-discharge is limited, and it is not conducive to enhancing the riveting effect and bonding effect between the polymer agglomerates and the porous layer, and it cannot prevent the porous layer well.
  • the relative movement between nanofibers and the relative movement between polymer agglomerates and nanofibers If the embedding depth is too deep, it will affect local ion transmission, resulting in inconsistent charging and discharging of the lithium-ion battery as a whole, and reducing the cycle capacity and cycle capacity retention rate at large rates.
  • the thickness of the surface of the isolation film will generally increase by 5-10 ⁇ m, and the increase in thickness is very uneven. Part of the polymer agglomerates is large. The thickness has increased a bit more. After the liquid injection and hot pressing of the lithium-ion battery, the thickness increase will be reduced to 0.5-1 ⁇ m, but the inhomogeneity still exists.
  • the polymer layer is coated on the porous layer of the present application, the polymer agglomerates are only coated on the surface of the porous layer, and the thickness increases only below 1 ⁇ m, and the thickness of the lithium ion battery is thinner after liquid injection and hot pressing. Without being limited to any theory, the inventor believes that because the pores in the porous layer are relatively large, polymer agglomerates will be embedded in the pores, which has little effect on the thickness of the isolation layer.
  • the depth of the polymer agglomerates embedded in the porous layer accounts for 0.01% to 80% of the thickness of the porous layer. If the embedding depth is too small, the riveting effect and bonding effect of the polymer agglomerates on the porous layer is insufficient. If the embedding depth is too large, it may cause insufficient adhesion between the isolation layer and the electrode pads.
  • the portion of the polymer agglomerates embedded in the porous layer accounts for 10% to 80% of the thickness of the polymer agglomerates, preferably 40% to 60%.
  • the embedding depth ratio is too small, which is not conducive to enhancing the riveting effect and bonding effect between the polymer agglomerates and the porous layer, and the adhesion between the electrode pads and the isolation layer is limited; the embedding depth ratio is too large, which will reduce the exposure
  • the area of polymer agglomerates is also not conducive to the interface bonding between the electrode pads and the isolation layer.
  • SEM scanning electron microscope
  • the polymer layer may have a regular pattern.
  • the method of pattern formation is not particularly limited, and can be carried out by methods known to those skilled in the art, for example, using a gravure roll engraved with a special pattern to transfer the polymer layer, or using a mask to cover part of the position to expose the desired
  • the position of the polymer layer is prepared to coat the polymer layer, and then a polymer layer with a regular pattern can be prepared.
  • the pattern of the polymer layer is not particularly limited, and it may be dotted, striped, blocky, linear, or the like.
  • the polymer layer with a regular pattern can make the interface adhesion distribution more uniform and fill the pores more uniformly, thereby reducing the local residual large pores and reducing the risk of local short circuits caused by poor local mechanical strength.
  • the polymer forming the polymer layer is not particularly limited, and can be selected from any polymer known in the art, such as polyvinylidene fluoride, polyimide, polyamide, polyacrylonitrile, polyethylene glycol, polyphenylene ether, poly Propylene carbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene oxide, copolymer of vinylidene fluoride-hexafluoropropylene, copolymerization of vinylidene fluoride-chlorotrifluoroethylene One or more of these polymers and their derivatives. These polymers can be used alone or in combination of two or more.
  • the isolation layer may further include an inorganic compound layer disposed on the porous layer, and the inorganic compound layer includes inorganic particles and a binder.
  • the inorganic compound layer can further improve the mechanical strength of the isolation layer and ensure insulation performance, and reduce the electronic conductivity of the isolation layer.
  • part of the inorganic particles in the inorganic compound layer are embedded in the porous layer, and the mechanical strength of the isolation layer can be further improved by the riveting effect of the inorganic particles on the fibrous porous layer.
  • the depth at which the inorganic particles are embedded in the porous layer accounts for 0.01% to 80% of the thickness of the porous layer.
  • the electronic resistivity of the inorganic compound layer is greater than 10 7 ⁇ m, and more preferably, the electronic resistivity is greater than 10 10 ⁇ m, thereby reducing the electronic conductivity of the isolation layer.
  • the inorganic compound layer has good ion conductivity, for example, its ion conductivity is 10 -8 S/cm to 10 -2 S/cm.
  • the thickness of the inorganic compound layer is not particularly limited as long as the purpose of the present application is achieved.
  • the thickness of the inorganic compound layer is 0.1 ⁇ m to 20 ⁇ m.
  • the porosity of the inorganic compound layer is not particularly limited as long as the purpose of the application can be achieved.
  • the porosity of the inorganic compound layer is 10%-40%, and the pore diameter is 0.001 ⁇ m-8 ⁇ m.
  • the inorganic particles are selected from HfO 2 , SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, BaO, ZnO, ZrO 2 , Y 2 O 3 , Al 2 O 3 , TiO 2 , SiO 2 , boehmite, magnesium hydroxide, aluminum hydroxide and other inorganic compounds, or materials with lithium ion conductivity, such as lithium phosphate (Li 3 PO 4 ), lithium titanium phosphate (Li x Ti y (PO 4 ) 3 , where 0 ⁇ x ⁇ 2 and 0 ⁇ y ⁇ 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO 4 ) 3 , where 0 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 1 , And 0 ⁇ z ⁇ 3), where 0 ⁇ x ⁇ 1 and 0 ⁇ y ⁇ 1 Li 1+x+y (Al,Ga) x (Ti,Ge)
  • the preparation method of the inorganic compound layer is not particularly limited, and it can be carried out by a method known in the art, such as spraying or deposition setting, preferably electrospraying.
  • the bonding method between the inorganic compound layer and the porous layer is not particularly limited, and can be performed by a method known in the art.
  • the inorganic compound layer and the porous layer can be bonded by hot pressing or bonding.
  • the average pore diameter of the porous layer varies in the thickness direction, and the pore diameter refers to the pore diameter of the pores formed by nanofibers in the porous layer.
  • the ion conductivity of the porous layer can be optimized while preventing short circuit or self-discharge due to excessively large pore diameter.
  • the average pore size of the porous layer in the region closer to the electrode pad is smaller than the average pore size in the region further away from the electrode pad.
  • the type of the lithium ion battery according to the present application is not limited, and can be any type of lithium ion battery, such as button type, cylindrical, square, soft pack type, hard shell type lithium ion battery and the like.
  • the lithium ion battery according to the present application includes a positive pole piece, a negative pole piece, an electrolyte, and a separator according to the present application.
  • the isolation layer may be formed on one surface of the positive pole piece and on one surface of the negative pole piece, and then stacked in the manner of the negative pole piece+separation layer, and the positive pole piece+separation layer. Layer to form a lithium ion battery laminate.
  • the separation layer can be formed on both surfaces of the positive pole piece, and then the negative pole piece, the separation layer + the positive pole piece + the separation layer are laminated to form a lithium ion battery A laminate in which there is no separator on the surface of the negative pole piece.
  • the separation layer can be formed on both surfaces of the negative pole piece, and then stacked in the manner of separation layer + negative pole piece + separation layer, and positive pole piece to form a lithium ion battery stack. body.
  • the laminated body formed in the above-mentioned embodiment may continue to be laminated in the above-mentioned order, or it may be directly wound to form a multilayer lithium ion battery laminated body. This application does not limit the stacking mode, and those skilled in the art can make a selection according to the actual situation.
  • the positive pole piece is not particularly limited, as long as the purpose of the present application can be achieved.
  • a positive pole piece usually includes a positive current collector and a positive active material layer.
  • the positive electrode current collector is not particularly limited, and may be any positive electrode current collector known in the art, such as copper foil, aluminum foil, aluminum alloy foil, and composite current collector.
  • the positive electrode active material layer includes a positive electrode active material.
  • the positive electrode active material is not particularly limited, and can be any positive electrode active material in the prior art.
  • the positive electrode active material can include lithium nickel cobalt manganate (811, 622, 523, 111), nickel cobalt aluminum At least one of lithium oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganate, lithium iron manganese phosphate, or lithium titanate.
  • the positive pole piece may further include a conductive layer, and the conductive layer is located between the positive electrode current collector and the positive electrode active material layer.
  • the composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art.
  • the conductive layer may include a conductive agent and an adhesive.
  • the negative pole piece is not particularly limited, as long as it can achieve the purpose of the present application.
  • a negative pole piece usually includes a negative current collector and a negative active material layer.
  • the negative electrode current collector is not particularly limited, and any negative electrode current collector known in the art can be used, such as copper foil, aluminum foil, aluminum alloy foil, and composite current collectors.
  • the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material is not particularly limited, and any negative electrode active material known in the art can be used.
  • it may include at least one of artificial graphite, natural graphite, mesocarbon microspheres, soft carbon, hard carbon, silicon, silicon carbon, lithium titanate, and the like.
  • the negative pole piece may further include a conductive layer, and the conductive layer is located between the negative electrode current collector and the negative electrode active material layer.
  • the composition of the conductive layer is not particularly limited, and may be a conductive layer commonly used in the art.
  • the conductive layer includes a conductive agent and an adhesive.
  • the aforementioned conductive agent is not particularly limited, and any conductive agent known in the art can be used as long as the purpose of the application can be achieved.
  • the conductive agent may be selected from at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fiber, Ketjen black, and graphene.
  • the conductive agent can be conductive carbon black (Super P).
  • the above-mentioned adhesive is not particularly limited, and any adhesive known in the art can be used as long as it can achieve the purpose of the present application.
  • the binder can be selected from polyvinylidene fluoride, polyacrylic acid, polyacrylate, styrene butadiene rubber (SBR), polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (Na -At least one of CMC).
  • the adhesive can be styrene butadiene rubber (SBR).
  • the electrolyte of the lithium ion battery is not particularly limited, and any electrolyte known in the art can be used, for example, it can be any of a gel state, a solid state, and a liquid state.
  • the liquid electrolyte may include a lithium salt and a non-aqueous solvent.
  • the lithium salt is not particularly limited, and any lithium salt known in the art can be used as long as the purpose of the application can be achieved.
  • the lithium salt can be selected from LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiB(C 6 H 5 ) 4 , LiCH 3 SO 3 , LiCF 3 SO 3 , LiN(SO 2 CF 3 ) 2 , LiC(SO 2 CF 3 ) 3 and at least one of LiPO 2 F 2.
  • LiPF 6 can be used as the lithium salt.
  • the non-aqueous solvent is not particularly limited as long as it can achieve the purpose of the present application.
  • the non-aqueous solvent may be selected from at least one of carbonate compounds, carboxylate compounds, ether compounds, nitrile compounds, and other organic solvents.
  • the carbonate compound may be selected from diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate (EPC), methyl carbonate Ethyl (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), carbonic acid 1,2-Difluoroethylene, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, carbonic acid 1-fluoro-2-methylethylene, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluorocarbonate At least one of -2-methylethylene and trifluoromethylethylene carbonate.
  • DEC diethyl carbonate
  • DMC dimethyl carbonate
  • DPC dipropyl carbonate
  • nanofibers can be deposited on one or both surfaces of the positive pole piece or the negative pole piece to form a porous layer containing nanofibers.
  • the preparation method of the electrochemical device of the present application further includes depositing a layer of polymer layer after depositing a porous layer containing nanofibers on the surface of the electrode pads.
  • the method for depositing the nanofiber porous layer and the polymer layer is not particularly limited, and can be carried out by a deposition method known in the art.
  • the porous layer can be prepared by electrospinning, air spinning or centrifugal spinning
  • the polymer layer can be prepared by electrospinning, air spinning or centrifugal spinning.
  • nanofibers can be deposited first to form a porous layer, and then polymer agglomerates can be deposited to form a polymer layer on the surface and surface of the porous layer.
  • the porous layer can be implemented with any spinning equipment known in the art, and is not particularly limited, as long as the purpose of the application can be achieved, and any spinning equipment known in the art can be used.
  • the electrospinning equipment can be Yongkang Leye Elite series, etc.
  • the air spinning equipment can be the air jet spinning machine of Nanjing Genus New Material
  • the centrifugal spinning equipment can be the centrifugal spinning machine of Sichuan Zhiyan Technology.
  • the electrospraying method can be implemented with any equipment known in the art, and is not particularly limited, as long as the purpose of the application can be achieved.
  • the electrostatic spraying equipment of Samez, France can be used.
  • the preparation method of the present application further includes depositing a porous layer containing nanofibers on the surface of the electrode pad, and then depositing an inorganic compound layer.
  • the deposition method of the inorganic compound layer is not particularly limited, and it can be performed by electrodeposition, for example.
  • the nanofiber spinning of the porous layer and the deposition of the inorganic compound layer can be performed at the same time, or it can be spun to form a porous layer of nanofibers, and then deposit the inorganic compound layer, or deposit the nanofiber porous layer and then deposit the inorganic compound layer. And repeat the process many times to alternately form multiple nanofiber porous matrix and inorganic compound layers.
  • the application also provides an electronic device including the electrochemical device according to the application.
  • Porosity the percentage of the volume of the pores in the isolation layer or the inorganic compound layer to the total volume of the isolation layer or the inorganic compound layer, which can be tested by mercury intrusion method.
  • Polymer agglomerate thickness refers to the thickness of a single polymer agglomerate in the direction perpendicular to the plane of the porous layer.
  • the negative active material artificial graphite, conductive carbon black, and styrene-butadiene rubber are mixed in a weight ratio of 96:1.5:2.5, and deionized water is added as a solvent to prepare a slurry with a solid content of 0.7, and stir it evenly.
  • the slurry was uniformly coated on one surface of a copper foil of a negative electrode current collector with a thickness of 8 ⁇ m, and dried at 110° C. to obtain a negative electrode piece with a thickness of 130 ⁇ m on a single surface coated with a negative electrode active material layer.
  • the above steps were repeated on the other surface of the negative electrode current collector to obtain a negative electrode sheet coated with a 130 ⁇ m thick negative electrode active material layer on both sides. Then, cut the negative pole piece into a size of 41mm ⁇ 61mm for later use.
  • the positive active material lithium cobalt oxide, conductive carbon black, and polyvinylidene fluoride were mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 0.75. Stir well.
  • the slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 ⁇ m and dried at 90°C to form a positive electrode active material layer with a thickness of 110 ⁇ m on one side of the positive electrode collector.
  • Repeat the above steps on the other surface of the positive electrode current collector aluminum foil to obtain a positive electrode piece coated with a 100 ⁇ m positive electrode active material layer on both sides. After the coating is completed, cut the positive pole piece into a size of 38mm ⁇ 58mm for use.
  • ethylene carbonate EC
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • LiPF 6 lithium salt lithium hexafluorophosphate
  • the following examples illustrate the preparation of an integrated isolation layer of nanofiber porous layer + polymer layer according to the present application.
  • These embodiments are described by taking the positive pole piece as an example, and an integrated isolation layer is deposited on both surfaces of the positive pole piece. It should be understood that the integrated isolation layer may also be deposited on the two surfaces of the negative pole piece, or an integrated isolation layer may be deposited on one surface of the positive pole piece and one surface of the negative pole piece, respectively.
  • the embodiments can also achieve the purpose of the present application; in addition, the integrated isolation layer can also be an integrated isolation layer of nanofiber porous layer + inorganic compound layer. Those skilled in the art should understand that these embodiments are also within the protection scope of the present application.
  • a porous layer (component PVDF) with a thickness of 12 ⁇ m was prepared by a method of mixing electrospinning and air spinning on one surface of the positive electrode sheet obtained in Preparation Example 2, with an average pore diameter of 150 nm, and the diameter of the nanofiber Is 600nm;
  • the polyvinylidene fluoride and polyacrylate are mixed in a mass ratio of 96:4, and dissolved in deionized water to form a polymer layer slurry.
  • the Dv50 of the polyvinylidene fluoride is 600 nm.
  • the polymer layer slurry is uniformly coated on the surface of the porous layer by a micro-gravure coating method, and the polymer layer is obtained through drying treatment;
  • the proportion of the total coverage area of the polymer layer is 10%, the maximum coverage area of a single polymer agglomerate is 0.1mm 2 , the depth of the polymer agglomerates embedded in the porous layer is 1 ⁇ m, and the depth of the polymer agglomerates embedded in the porous layer accounts for the thickness of the polymer agglomerates
  • the ratio is 25%, and the depth of the polymer agglomerates embedded in the porous layer accounts for 8.3% of the thickness of the porous layer.
  • the porosity of the isolation layer is 80%, the thickness is 15 ⁇ m, and the air permeability when converted to 20 ⁇ m is 112 s/100 cm 3 .
  • Example 1 Except that the total coverage area ratio of the polymer layer is 30%, and the air permeability of the isolation layer when converted to 20 ⁇ m is 123 s/100 cm 3 , the rest is the same as in Example 1.
  • Example 1 Except that the total coverage area ratio of the polymer layer is 70%, and the air permeability of the isolation layer when converted to 20 ⁇ m is 137 s/100 cm 3 , the rest is the same as in Example 1.
  • Example 2 Except that the maximum coverage area of a single polymer agglomerate is 1 ⁇ 10 -5 mm 2 , and the average pore diameter of the porous layer is 80 nm, the rest is the same as in Example 2.
  • Example 2 Except that the maximum coverage area of a single polymer agglomerate is 0.01 mm 2 and the average pore diameter of the porous layer is 100 nm, the rest is the same as in Example 2.
  • Example 2 Except that the maximum coverage area of a single polymer agglomerate is 1 mm 2 and the average pore diameter of the porous layer is 400 nm, the rest is the same as in Example 2.
  • the rest is the same as in Example 5.
  • the rest is the same as in Example 5.
  • the rest is the same as in Example 5.
  • the rest is the same as in Example 5.
  • the rest is the same as in Example 5.
  • the rest is the same as in Example 5.
  • the thickness of the porous layer is adjusted to 4 ⁇ m, the depth of the polymer agglomerates embedded in the porous layer is 1 ⁇ m, the thickness of the isolation layer is 5 ⁇ m, and the depth of the polymer agglomerates embedded in the porous layer accounts for 50% of the thickness of the polymer agglomerates, the rest is the same as the examples 5 is the same.
  • Example 5 Except for adjusting the porosity of the isolation layer to 95%, the rest is the same as in Example 5.
  • nanofiber material is replaced with polyethylene oxide (PEO), the rest is the same as in Example 5.
  • PEO polyethylene oxide
  • a porous layer (component PVDF) with a thickness of 12 ⁇ m was prepared by a method of mixing electrospinning and air spinning.
  • the diameter of the nanofibers was 600nm, and the porous
  • the average pore size of the region of the layer closer to the positive pole piece is 100nm
  • the average pore size of the porous layer is 500nm in the region further away from the positive pole piece.
  • the average pore size of the porous layer gradually increases from the region closer to the positive pole piece to the region further away from the positive pole piece. Big.
  • Polyvinylidene fluoride and polyacrylate are mixed according to a mass ratio of 96:4 and dissolved in deionized water to form a polymer layer slurry.
  • the Dv50 of polyvinylidene fluoride is 600 nm.
  • the polymer layer slurry is uniformly coated on the surface of the porous layer by a micro-gravure coating method, and the polymer layer is obtained through drying treatment.
  • the proportion of the total coverage area of the polymer layer is 30%, the maximum coverage area of a single polymer aggregate is 0.01mm 2 , the depth of the polymer aggregate embedded in the porous layer is 1.5 ⁇ m, and the depth of the polymer aggregate embedded in the porous layer accounts for the thickness of the polymer aggregate
  • the ratio is 50%, the depth of the polymer agglomerates embedded in the porous layer accounts for 8.3% of the thickness of the porous layer, the porosity of the isolation layer is 80%, and the thickness is 15 ⁇ m.
  • the conductive carbon black and styrene-butadiene rubber are mixed according to a weight ratio of 95:5, and deionized water is added as a solvent to prepare a slurry with a solid content of 0.8, and stir it evenly.
  • the slurry was uniformly coated on the two surfaces of a negative electrode current collector copper foil with a thickness of 8 ⁇ m, and dried at 110° C. to obtain a negative electrode conductive layer with a thickness of 2 ⁇ m on one side.
  • the negative electrode active material graphite, conductive carbon black, and styrene-butadiene rubber are mixed according to a weight ratio of 96:1.5:2.5, and deionized water is added as a solvent to prepare a slurry with a solid content of 0.7, and stir it evenly.
  • the slurry was uniformly coated on the conductive layer, and dried at 110° C., to obtain a negative electrode sheet with a thickness of 130 ⁇ m and a negative electrode active material coated on one side.
  • Repeat the above steps on the other surface of the negative pole piece to obtain a negative pole piece coated with negative active material on both sides. Then, cut the pole piece into a size of 41mm ⁇ 61mm for use.
  • the conductive carbon black and styrene-butadiene rubber are mixed according to a weight ratio of 97:3, and deionized water is added as a solvent to prepare a slurry with a solid content of 0.85, and stir evenly.
  • the slurry was uniformly coated on two surfaces of a positive electrode current collector aluminum foil with a thickness of 10 ⁇ m and dried at 110° C. to obtain a positive electrode conductive layer with a thickness of 2 ⁇ m on one side.
  • the positive active material lithium cobalt oxide, conductive carbon black, and polyvinylidene fluoride were mixed in a weight ratio of 97.5:1.0:1.5, and N-methylpyrrolidone (NMP) was added as a solvent to prepare a slurry with a solid content of 0.75. Stir well.
  • the slurry was uniformly coated on the above-mentioned positive electrode conductive layer and dried at 90° C. to obtain a positive electrode sheet coated with a 100 ⁇ m positive electrode active material layer on both sides. After coating, cut the pole piece into 38mm ⁇ 58mm specifications for later use.
  • the separator was prepared according to the following steps.
  • a porous layer with a thickness of 12 ⁇ m (component PVDF) is prepared by a method of mixed use of electrospinning and air spinning on one surface of the positive pole piece, with an average pore diameter of 100 nm and a nanofiber diameter of 600 nm.
  • the electrospray method sprays the suspension on the surface of the positive pole piece with the porous layer to form an inorganic compound layer with a thickness of 3 ⁇ m, a conductivity of 10 8 ⁇ m, and an ionic conductivity of 10 -5 S/ cm, the average pore diameter is 0.5 ⁇ m, the depth at which inorganic particles are embedded in the porous layer accounts for 8.3% of the thickness of the porous layer, and the thickness of the isolation layer is 15 ⁇ m.
  • a porous layer with a thickness of 15 ⁇ m (component PVDF) was prepared by electrospinning, with an average pore diameter of 150 nm, a diameter of nanofibers of 600 nm, and a porosity of 80%.
  • the air permeability when converted to 20 ⁇ m is 112s/100cm 3 , and then the above steps are repeated on the other surface of the positive pole piece and dried at 90° C. to obtain a double-sided coated positive pole piece.
  • the negative pole piece prepared in the above preparation example 1 and the positive pole piece with the separator prepared in each embodiment are opposed and stacked. After fixing the four corners of the entire laminated structure with tape, put it in the aluminum plastic After the top side sealing, the electrolyte in Preparation Example 3 was injected into the film, and then packaged to obtain a lithium-ion laminated battery. Among them, in Example 21, the negative pole piece in Example 21 was used instead of the negative pole piece in Preparation Example 1.
  • Polyethylene with a thickness of 15 ⁇ m is selected as the separator, and it is placed between the negative pole piece and the positive pole piece of Preparation Examples 1 and 2 as the separator. Lay the negative pole piece, the positive pole piece and the separator opposite and stack up. After fixing the four corners of the entire laminated structure with tape, placing it in an aluminum plastic film, sealing on the top side, injecting the electrolyte in the preparation example, and packaging to finally obtain a lithium-ion laminated battery.
  • the isolation layer of Example 23 does not contain polymer agglomerates.
  • the binding force between the isolation layer and the negative electrode is significantly increased, and the safety of the battery is Be improved.

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Abstract

一种电化学装置及包含该电化学装置的电子装置。该电化学装置包括电极极片以及形成在该电极极片表面的隔离层，该隔离层中包含形成在该电极极片表面的多孔层；该多孔层包含纳米纤维，该隔离层的电解液注液性为15秒以下。该电化学装置无需单独的隔离膜，且具有较高的能量密度。

Description

电化学装置 技术领域
本申请涉及电化学装置领域，具体涉及一种锂离子电池。
背景技术
锂离子电池具有能量密度高、循环寿命长、标称电压高(>3.7V)、自放电率低等许多优点，在消费电子领域具有广泛的应用。随着近年来电动汽车和可移动电子设备的高速发展，人们对锂离子电池的能量密度、安全性、循环性能等相关要求越来越高，期待着综合性能全面提升的新型锂离子电池的出现。其中，在锂离子电池的正负极之间设置一隔离层代替传统的普通隔离膜是一种备受瞩目的新型技术。
现有锂离子电池在正负极之间不设置普通隔离膜的技术主要是通过刮涂的方法在电极极片表面制备聚合物层和(或)陶瓷层的方法来实现，其主要弊端如下：聚合物层的均一性较差，单位面积的重量和厚度存在较大差异；聚合物层孔隙率较低，会堵塞电极极片表面的锂离子传输通路，导致锂离子电池倍率性能严重恶化；刮涂法制备过程中需要使用大量溶剂，对电极极片表面的活性物质和粘接剂产生破坏；陶瓷层与电极极片粘结力较弱，会引发安全隐患。因此，还需发展一种新的材料或结构，来代替传统的隔离膜。
发明内容
本申请的目的是提供一种电化学装置，不需使用传统的隔离膜。
本申请第一方面提供了一种电化学装置，包括电极极片以及形成在所述电极极片表面的隔离层，所述隔离层中包含形成在所述电极极片表面的多孔层；所述多孔层包含纳米纤维，所述隔离层的电解液注液性为15秒以下。
在本申请第一方面的一些实施方式中，所述隔离层具有以下特征中的至少一者：
(a)将所述隔离层的厚度换算为20μm时的透气度为5s/100cm 3～400s/100cm 3；
(b)所述隔离层的孔隙率为30％～95％；
(c)所述多孔层的平均孔径为20nm～10μm；
(d)所述隔离层的厚度为1μm～20μm。
在本申请第一方面的一些实施方式中，所述纳米纤维的直径为0.1nm～2μm。
在本申请第一方面的一些实施方式中，所述纳米纤维包括聚偏二氟乙烯、聚酰亚胺、聚酰胺、聚丙烯腈、聚乙二醇、聚苯醚、聚碳酸亚丙酯、聚甲基丙烯酸甲酯、聚对苯二甲酸乙二醇酯、聚环氧乙烷、聚偏二氟乙烯-六氟丙烯或聚偏二氟乙烯-三氟氯乙烯中的至少一种。
在本申请第一方面的一些实施方式中，所述隔离层还包括聚合物层，所述聚合物层设置于所述多孔层上；所述聚合物层的厚度为0.05μm～4μm，所述聚合物层在所述多孔层上的覆盖面积比例为10％～70％。
在本申请第一方面的一些实施方式中，所述聚合物层包括聚合物团聚体，所述聚合物团聚体具有以下特征中的至少一者：
(a)所述聚合物层中单个聚合物团聚体的最大覆盖面积为1×10 -5mm 2～1mm 2，优选为0.001m 2～0.05mm 2；
(b)所述聚合物层中的聚合物团聚体嵌入所述多孔层的深度占所述多孔层厚度的0.01％～80％；
(c)所述聚合物层中的聚合物团聚体嵌入所述多孔层的深度占聚合物团聚体厚度的10％～80％。
在本申请第一方面的一些实施方式中，所述聚合物层具有规则的图案。
在本申请第一方面的一些实施方式中，所述隔离层还包括无机化合物层，所述无机化合物层包括无机颗粒，所述无机化合物层设置于所述多孔层上。
在本申请第一方面的一些实施方式中，所述无机化合物层具有以下特征中的至少一者：
(a)所述无机化合物层中的部分无机颗粒嵌入所述多孔层中；
(b)所述无机化合物层的无机颗粒嵌入所述多孔层的深度占所述多孔层厚度的0.01％～80％；
(c)所述无机化合物层的电子电阻率大于10 7Ω·m；
(d)所述无机化合物层的离子电导率为10 -8S/cm～10 -2S/cm；
(e)所述无机化合物层的厚度为0.1μm～20μm；
(f)所述无机化合物层的孔隙率为10％～40％，孔径为0.001μm～8μm。
在本申请第一方面的一些实施方式中，所述无机化合物层通过喷涂或沉积设置。
在本申请第一方面的一些实施方式中，所述无机化合物层和所述多孔层通过热压或粘合实现粘结。
在本申请第一方面的一些实施方式中，所述多孔层的平均孔径在厚度方向上是变化的。
在本申请第一方面的一些实施方式中，其中所述多孔层更靠近所述电极极片区域的平均孔径小于更远离所述电极极片区域的平均孔径。
在本申请第一方面的一些实施方式中，所述多孔层通过电纺丝、气纺丝或离心纺丝制备。
本申请第二方面提供了一种电子装置，其包含本申请第一方所提供的电化学装置。
本申请的方案所提供的电化学装置，通过在电极极片(例如正极极片和/或负极极片)表面设置多孔层，以替代普通隔离膜，从而起到隔离电子，传导离子的作用；进一步地，所述多孔层与普通隔离膜相比厚度小，保液能力强，因而使电化学装置具有较高的能量密度。
附图说明
为了更清楚地说明本申请实施例和现有技术的技术方案，下面对实施例和现有技术中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的附图。
图1为实施例1的电化学装置隔离层表面SEM照片(500倍)；
图2为实施例1的电化学装置隔离层表面SEM照片(2000倍)；
图3为实施例1的电化学装置隔离层断面SEM照片；箭头所指为嵌入多孔层中的聚合物团聚体颗粒。
具体实施方式
为使本申请的目的、技术方案、及优点更加清楚明白，以下参照附图和实施例，对本申请进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域技术人员在没有作出创造性劳动前提下所获得的 所有其他实施例，都属于本申请保护的范围。
本申请的电化学装置可以是使用本领域技术人员所熟知的电极极片和本申请的隔离层的任何电化学装置，例如锂离子电池、钠离子电池、镁离子电池、超级电容器等，以下以锂离子电池为例进行说明。本领域技术人员应当理解，以下说明仅为举例说明，并不限定本申请的保护范围。
本申请提供一种电化学装置，包括电极极片以及形成在所述电极极片表面的隔离层，所述隔离层中包含形成在所述电极极片表面的多孔层；所述多孔层包含纳米纤维，所述隔离层的电解液注液性为15秒以下。
在锂离子电池组装过程中，通常，电解液通过定量泵注入密封腔内(例如包装壳)，将锂离子电池放入注液室，然后用真空泵对注液室抽真空，锂离子电池内部也形成真空环境，然后将注液嘴插入锂离子电池注液口，打开电解液注液阀，同时用氮气将电解液腔室加压，保压一定时间，注液室再放气至常压，最后长时间静置，从而让电解液充分浸润正极极片、负极极片和隔离层。当注液完成后，将锂离子电池密封。一般来说，在注液过程中，电解液首先渗透到隔离层中，然后在逐渐渗透到正负极材料中。因此，注液性是锂离子电池的一个重要指标。传统的隔离膜主要采用聚乙烯微孔膜或聚丙烯微孔膜或者二者的组合，其注液性具有一定的局限性。本申请采用在电极极片表面设置包含纳米纤维的隔离层，使得隔离层的电解液注液性达到15秒以下，可以显著改善锂离子电池的注液性能。
另外，纳米纤维多孔层与电极极片之间具有较好的粘接力，在锂离子电池跌落过程中，可以有效避免锂离子电池中使用常规隔离膜时，隔离膜被电解液冲刷而翻折，从而提高锂离子电池的安全性。
本申请中所说的电极极片可以是正极极片和/或负极极片，隔离层可以设置于正极极片上和/或负极极片上，以隔离正极极片和负极极片；另外，隔离层可以设置于正极极片或负极极片的一个表面上或两个表面上，本申请在此不做限定。
在本申请的一些实施方案中，在将所述隔离层的厚度换算为20μm时的透气度为5s/100cm 3～400s/100cm 3。本申请发明人发现，当隔离层的透气度在上述范围内时，隔离层的注液性明显提高。
在本申请的一些实施方案中，所述隔离层的孔隙率为30％～95％。当隔离层的孔隙率在上述范围内时，本申请的锂离子电池具有很好的注液性，并具有高离子传导性。在本申请的另一些实施方案中，所述多孔层的平均孔径为20nm～10μm。当孔径小于20nm时， 注液性下降，离子传导性降低；当孔径大于10μm时，孔径过大，电极极片中的电极活性物质可能会穿过隔离层，发生短路，产生自放电现象。当隔离层的厚度过小，隔离层不能很好地起到隔离正极和负极之间电子的作用，自放电增大，当隔离层厚度过大，会使得锂离子电池的能量密度显著降低；在本申请的另一些实施方案中，所述隔离层的厚度为1μm～20μm；优选为2μm至18μm，更优选为5μm至15μm，最优选为8μm至12μm。
在本申请的一些实施方案中，所述纳米纤维的直径为0.1nm～2μm。纳米纤维的直径过小，纤维本身的强度太低，在锂离子电池制备或使用过程中，容易导致纳米纤维断开，隔离层被电极活性物质颗粒刺穿，发生自放电；纳米纤维直径过大，则隔离层中纳米纤维占据的体积太大，在隔离层含有相同重量的纳米纤维时，可能导致隔离层的孔径过大，在隔离层保持相同孔隙率的情况下，纳米纤维含量降低，导致隔离层强度降低，孔径尺寸过大。
在本申请的一些实施方案中，所述纳米纤维包括聚偏二氟乙烯、聚酰亚胺、聚酰胺、聚丙烯腈、聚乙二醇、聚苯醚、聚碳酸亚丙酯、聚甲基丙烯酸甲酯、聚对苯二甲酸乙二醇酯、聚环氧乙烷、聚偏二氟乙烯-六氟丙烯或聚偏二氟乙烯-三氟氯乙烯等聚合物中的至少一种。优选地，所述纳米纤维包含锂离子导体材料，例如聚偏氟乙烯-六氟丙烯、聚偏氟乙烯、聚丙烯腈、聚甲基丙烯酸甲酯、聚苯醚、聚碳酸亚丙酯、聚环氧乙烷等及其衍生物中的至少一种。这些聚合物可以单独使用一种，也可以两种以上组合使用。
在本申请的一些实施方案中，所述隔离层还包括聚合物层，所述聚合物层的厚度为0.05μm～4μm，聚合物层覆盖在纳米纤维多孔层上，其覆盖面积比例为纳米纤维多孔层的10％～70％，优选为20％～40％。聚合物层可以提高隔离层的机械强度，降低K值(单位时间内的电池的电压降，mV/d；电池自放电率的一种指标)。此外，当纳米纤维多孔层中存在较大孔隙时，聚合物层可以覆盖这些孔径较大的孔隙，减少自放电。如果覆盖面积太小，对降低K值的作用不明显，对增大隔离层机械强度的效果也不明显。如果覆盖面积太大，则影响隔离层的离子传导，降低倍率性能。另外，聚合物层还可以提高隔离层和与其表面接触的电极极片的粘结性能。在锂离子电池卷绕过程中，防止隔离层与电极极片之间的滑动。
聚合物层包括聚合物团聚体，其中，所述的单个聚合物团聚体是指由一个或者多个聚合物二次颗粒团聚形成的团聚体；可以理解为聚合物团聚体可以是包含多个聚合物二次颗粒的团聚体或单独的聚合物二次颗粒。本申请发明人经过深入研究发现，要达到较优的效 果，单个聚合物团聚体的最大覆盖面积为1×10 -5mm 2～1mm 2，优选为0.001m 2～0.05mm 2。单个聚合物团聚体体积太小时，与其相接触的电极极片的粘接效果有限，且改善多孔层孔径的能力不足，即不能有效地覆盖纳米纤维多孔层中的较大孔隙，因此不能够有效地防止自放电。如果单个聚合物团聚体的体积太大，则会影响局部的离子传输，导致锂离子电池整体充放电不一致，引发大倍率下循环容量和循环容量保持率降低。
在本申请的一个优选的实施方案中，聚合物团聚体嵌入到多孔层中，如图3所示。聚合物团聚体嵌入多孔层中，一方面可以减小较大孔的数量，即减小孔直径，另一方面可以使聚合物团聚体在多孔层中相对固定，避免滑移。此外，由于聚合物团聚体嵌入多孔层中，也会减小多孔层中的纳米纤维之间的相对滑移。本申请发明人发现，聚合物团聚体嵌入多孔层的深度优选为0.5～5μm，更优选为1～2μm。如果嵌入深度太小，则难以有效填充多孔层中的孔，降低自放电的作用有限，并且不利于增强聚合物团聚体与多孔层的铆合效应和粘接作用，不能很好地防止多孔层中纳米纤维之间的相对移动以及聚合物团聚体与纳米纤维之间的相对移动。如果嵌入深度太深，则会影响局部离子传输，导致锂离子电池整体充放电不一致，降低大倍率下的循环容量和循环容量保持率。
应当注意的是，在常规隔离膜上涂覆聚合物层时，一般会使隔离膜的表面的厚度增大5～10μm，并且厚度增加是很不均匀的，部分聚合物团聚体大的位置，厚度增长的更多一些。在锂离子电池注液热压后，厚度增加幅度会降低至0.5～1μm，但不均一性依旧存在。但是，在本申请的多孔层上涂覆聚合物层时，聚合物团聚体仅涂在多孔层表面上，厚度增加仅1μm以下，锂离子电池注液和热压后，厚度更薄。不限于任何理论，发明人认为，由于多孔层中的孔比较大，聚合物团聚体会嵌入孔隙中，对隔离层厚度的影响较小。
在本申请的一些优选的实施方案中，聚合物团聚体嵌入多孔层的深度占多孔层厚度的0.01％～80％。嵌入深度太小，则聚合物团聚体对多孔层的铆合效应和粘接作用不足。嵌入深度太大，有可能导致隔离层与电极极片粘结作用不足。
在本申请的一些优选的实施方案中，聚合物团聚体嵌入多孔层的部分占聚合物团聚体厚度的比例为10％～80％，优选为40％～60％。嵌入深度比例太小，不利于增强聚合物团聚体与多孔层的铆合效应和粘接作用，电极极片与隔离层之间的粘接力有限；嵌入深度比例太大，会降低暴露在外的聚合物团聚体的面积，同样不利于电极极片与隔离层间的界面粘接，嵌入效果的扫描电镜(SEM)照片如图3所示。
在本申请的一些优选的实施方案中，聚合物层可以具有规则的图案。形成图案的方法 没有特别限制，可以用本领域技术人员已知的方法进行，例如，利用刻有特殊图案的凹版辊进行聚合物层的转移涂布，或者利用掩模板来遮蔽部分位置，露出需要制备聚合物层的位置来进行聚合物层的涂覆，即可制备得到具有规则图案的聚合物层。聚合物层的图案没有特别限制，可以是点状、条纹状、块状、线状等。具有规则图案的聚合物层可以使得界面粘接力分布更加均匀，对孔隙填充更加均匀，从而减少局部残余大孔，减小局部机械强度差而导致局部短路的风险。
形成聚合物层的聚合物没有特别限制，可以选自本领域公知的任何聚合物，例如聚偏氟乙烯、聚酰亚胺、聚酰胺、聚丙烯腈、聚乙二醇、聚苯醚、聚碳酸亚丙酯、聚甲基丙烯酸甲酯、聚对苯二甲酸乙二酯、聚环氧乙烷、偏二氟乙烯-六氟丙烯的共聚物、偏二氟乙烯-三氟氯乙烯的共聚物及其衍生物中的一种或多种，这些聚合物可以单独使用一种，也可以两种以上组合使用。
在本申请的一些优选的实施方案中，隔离层还可以包括设置在多孔层上的无机化合物层，所述无机化合物层包括无机颗粒和粘接剂。无机化合物层可以进一步提高隔离层的机械强度并确保绝缘性能，降低隔离层的电子传导性。优选地，无机化合物层中的部分无机颗粒嵌入多孔层中，通过无机颗粒对纤维多孔层的铆合效应，可以进一步提高隔离层的机械强度。优选地，无机颗粒嵌入多孔层的深度占多孔层厚度的0.01％～80％。无机颗粒嵌入深度太小，则铆合效应不明显。嵌入深度太大，则可能贯穿整个多孔层，降低无机化合物层的保护作用。优选地，无机化合物层的电子电阻率大于10 7Ω·m，更优选的，电子电阻率大于10 10Ω·m，从而降低隔离层的电子传导性。优选地，无机化合物层具有良好的离子传导性，例如，其离子电导率为10 -8S/cm～10 -2S/cm。无机化合物层的厚度没有特别限制，只要实现本申请的目的即可，例如，无机化合物层的厚度为0.1μm～20μm。无机化合物层的孔隙率没有特别限制，只要能实现本申请的目的即可，例如，无机化合物层的孔隙率为10％～40％，孔径为0.001μm～8μm。
在本申请的一个优选实施方案中，所述无机颗粒选自HfO 2、SrTiO 3、SnO 2、CeO 2、MgO、NiO、CaO、BaO、ZnO、ZrO 2、Y 2O 3、Al 2O 3、TiO 2、SiO 2、勃姆石、氢氧化镁、氢氧化铝等无机化合物，或者具有锂离子传导能力的材料，如磷酸锂(Li 3PO 4)、锂钛磷酸盐(Li xTi y(PO 4) 3，其中0<x<2且0<y<3)、锂铝钛磷酸盐(Li xAl yTi z(PO 4) 3，其中0<x<2，0<y<1，且0<z<3)、其中0≤x≤1且0≤y≤1的Li 1+x+y(Al,Ga) x(Ti,Ge) 2-xSi yP 3-yO 12、锂镧钛酸盐(Li xLa yTiO 3，其中0<x<2且0<y<3)、锂锗硫代磷酸盐(Li xGe yP zS w，其中0<x<4，0<y<1， 0<z<1，且0<w<5)、锂氮化物(Li xN y，其中0<x<4，0<y<2)、SiS 2玻璃(Li xSi yS z，其中0≤x<3，0<y<2，且0<z<4)、P 2S 5玻璃(Li xP yS z，其中0≤x<3，0<y<3，且0<z<7)、Li 2O、LiF、LiOH、Li 2CO 3、LiAlO 2、Li 2O-Al 2O 3-SiO 2-P 2O 5-TiO 2-GeO 2陶瓷、和石榴石陶瓷(Li 3+xLa 3M 2O 12，其中0≤x≤5，且M为Te、Nb或Zr)，这些无机颗粒可以单独使用一种，也可以两种以上组合使用。
无机化合物层的制备方法没有特别限制，可以采用本领域公知的方法进行，例如通过喷涂或沉积设置，优选电喷涂。
无机化合物层与多孔层之间的粘结方式没有特别限制，可以采用本领域公知的方法进行，例如无机化合物层和多孔层可以通过热压或粘合实现粘结。
在本申请的一个优选的实施方案中，所述多孔层的平均孔径在厚度方向上是变化的，所述孔径是指多孔层中由纳米纤维形成的孔的孔径。通过平均孔径在厚度方向上的变化，可以优化多孔层的离子传导性，同时防止由于孔径过大而导致短路或发生自放电。优选地，多孔层更靠近电极极片区域的平均孔径小于更远离电极极片区域的平均孔径。
根据本申请的锂离子电池的型式没有限制，可以为任何型式的锂离子电池，例如纽扣型、圆柱形、方形、软包型、硬壳型锂离子电池等任何型式。根据本申请的锂离子电池包括正极极片、负极极片、电解液和根据本申请的隔离层。
在本申请的一种实施方式中，隔离层可以形成在正极极片的一个表面上和负极极片的一个表面上，然后按照负极极片+隔离层、正极极片+隔离层的方式进行叠层，形成锂离子电池层叠体。在本申请的另一种实施方式中，隔离层可以形成在正极极片的两个表面上，然后按照负极极片、隔离层+正极极片+隔离层的方式进行叠层，形成锂离子电池层叠体，其中负极极片表面上没有隔离层。在本申请的另一种实施方式中，隔离层可以形成在负极极片的两个表面上，然后按照隔离层+负极极片+隔离层、正极极片的方式进行层叠，形成锂离子电池层叠体。在上述实施方式中形成的层叠体，可以继续按照上述顺序层叠，也可以直接卷绕，形成多层的锂离子电池层叠体。本申请对于层叠方式没有限制，本领域技术人员可以根据实际情况进行选择。
在本申请的实施方案中，正极极片没有特别限制，只要能够实现本申请的目的即可。例如，正极极片通常包含正极集流体和正极活性材料层。其中，正极集流体没有特别限制，可以为本领域公知的任何正极集流体，例如铜箔、铝箔、铝合金箔以及复合集流体等。正极活性材料层包括正极活性材料，正极活性材料没有特别限制，可以为现有技术的任何正 极活性材料，正极活性材料可以包括镍钴锰酸锂(811、622、523、111)、镍钴铝酸锂、磷酸铁锂、钴酸锂、锰酸锂、磷酸锰铁锂或钛酸锂中的至少一种。
任选地，正极极片还可以包含导电层，导电层位于正极集流体和正极活性材料层之间。导电层的组成没有特别限制，可以是本领域常用的导电层。例如，导电层可以包括导电剂和粘接剂。
在本申请的实施方案中，负极极片没有特别限制，只要能够实现本申请目的即可。例如，负极极片通常包含负极集流体和负极活性材料层。其中，负极集流体没有特别限制，可以使用本领域公知的任何负极集流体，例如铜箔、铝箔、铝合金箔以及复合集流体等。负极活性材料层包括负极活性材料，负极活性材料没有特别限制，可以使用本领域公知的任何负极活性材料。例如，可以包括人造石墨、天然石墨、中间相碳微球、软碳、硬碳、硅、硅碳、钛酸锂等中的至少一种。
任选地，负极极片还可以包含导电层，导电层位于负极集流体和负极活性材料层之间。导电层的组成没有特别限制，可以是本领域常用的导电层。例如，导电层包括导电剂和粘接剂。
上述导电剂没有特别限制，可以使用本领域公知的任何导电剂，只要能实现本申请目的即可。例如，导电剂可以选自导电炭黑(Super P)、碳纳米管(CNTs)、碳纤维、科琴黑、石墨烯中的至少一种。例如，导电剂可选用导电炭黑(Super P)。上述粘接剂没有特别限制，可以使用本领域公知的任何粘接剂，只要能实现本申请目的即可。例如，粘接剂可以选自聚偏氟乙烯、聚丙烯酸、聚丙烯酸酯、丁苯橡胶(SBR)、聚乙烯醇(PVA)、聚四氟乙烯(PTFE)、羧甲基纤维素钠(Na-CMC)中的至少一种。例如，粘接剂可选用丁苯橡胶(SBR)。
锂离子电池的电解液没有特别限制，可以使用本领域公知的任何电解液，例如可以是凝胶态、固态和液态中的任一种。例如，液态电解液可以包括锂盐和非水溶剂。
锂盐没有特别限制，可以使用本领域公知的任何锂盐，只要能实现本申请的目的即可。例如，锂盐可以选自LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3和LiPO 2F 2中的至少一种。例如，锂盐可选用LiPF 6。
非水溶剂没有特别限定，只要能实现本申请的目的即可。例如，非水溶剂可以选自碳酸酯化合物、羧酸酯化合物、醚化合物、腈化合物、其它有机溶剂中的至少一种。
例如，碳酸酯化合物可以选自碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸甲乙酯(MEC)、碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、碳酸乙烯基亚乙酯(VEC)、碳酸氟代亚乙酯(FEC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯、碳酸三氟甲基亚乙酯中的至少一种。
本申请的电化学装置的制备方法没有任何限制，例如可以在正极极片或负极极片的一个或两个表面上沉积纳米纤维，形成包含纳米纤维的多孔层。
在一个优选的实施方案中，本申请电化学装置的制备方法还包括在电极极片表面沉积包含纳米纤维的多孔层后，再沉积一层聚合物层。
沉积纳米纤维多孔层和聚合物层的方法没有特别限制，可以采用本领域公知的沉积方法进行，例如，多孔层可以通过电纺丝、气纺丝或离心纺丝制备而成，聚合物层通过电喷涂法制备而成。例如，可以先沉积纳米纤维，形成多孔层，再沉积聚合物团聚体，以在多孔层表层和表面形成聚合物层。
多孔层可以用本领域已知的任何纺丝设备实施，没有特别限制，只要能实现本申请目的即可，可以使用本领域已知的任何纺丝设备，例如电纺丝设备可以为永康乐业Elite系列等；气纺丝设备可以为南京捷纳思新材料的气喷纺丝机等；离心纺丝设备可以为四川致研科技的离心纺丝机等。电喷涂法可以用本领域已知的任何设备实施，没有特别限制，只要能实现本申请的目的即可。例如可以使用法国萨麦斯的静电喷涂设备。
在一个优选的实施方案中，本申请的制备方法还包括在电极极片表面沉积包含纳米纤维的多孔层后，再沉积一个无机化合物层。
无机化合物层的沉积方法没有特别限制，例如可以通过电沉积进行。所述多孔层的纳米纤维纺丝和无机化合物层的沉积可以同时进行，也可以先纺丝形成纳米纤维的多孔层，然后沉积无机化合物层，或者先沉积纳米纤维多孔层，然后沉积无机化合物层，并将该过程重复多次，交替形成多个纳米纤维多孔基体和无机化合物层。
本申请还提供一种电子装置，其包含根据本申请的电化学装置。
本申请中所用的术语一般为本领域技术人员常用的术语，如果与常用术语不一致，以本申请中的术语为准。
具体地，在本申请中，以下术语的含义如下：
孔隙率：隔离层或无机化合物层中孔隙的体积占隔离层或无机化合物层总体积的百分比，可以使用压汞法进行测试。
聚合物团聚体厚度：指单个聚合物团聚体在垂直于多孔层平面的方向上的厚度。
测试方法：
锂离子电池自放电速率K值：
将锂离子电池以0.5C的电流放电至3.0V，静置5min，接着将锂离子电池以0.5C的电流恒定电流充电至3.85V，然后以3.85V的电压恒定电压充电至电流为0.05C，在25℃±3℃的环境中静置两天，测试并记录此时的电压OCV1。接着，将锂离子电池继续在25℃±3℃的环境静置两天，测试并记录此时的电压OCV2，通过如下公式获得K值：K(mV/h)＝(OCV2-OCV1)/48h*1000。
容量保持率：
将锂离子电池以0.5C的电流恒定电流充电至4.4V，然后以4.4V的电压恒定电压充电至电流为0.05C，在25℃±3℃的环境中静置10min，然后以0.5C的电流放电至3.0V，记录首次放电容量为Q 1，如此重复循环50次，记录此时放电容量为Q 50，通过如下公式得到50次循环后的容量保持率η：η＝Q 50/Q 1*100％。
实施例
制备例1：负极极片的制备
将负极活性材料人造石墨、导电炭黑、丁苯橡胶按照重量比96:1.5:2.5进行混合，加入去离子水作为溶剂，调配成固含量为0.7的浆料，搅拌均匀。将浆料均匀涂覆在厚度为8μm的负极集流体铜箔的一个表面上，110℃条件下烘干，得到厚度为130μm的单面涂覆负极活性材料层的负极极片。在该负极集流体的另一个表面上重复以上步骤，得到双面涂覆130μm厚的负极活性材料层的负极极片。然后，将负极极片裁切成41mm×61mm的规格待用。
制备例2：正极极片的制备
将正极活性材料钴酸锂、导电炭黑、聚偏二氟乙烯按照重量比97.5:1.0:1.5进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成固含量为0.75的浆料，搅拌均匀。将浆料 均匀涂覆在厚度为10μm的正极集流体铝箔的一个表面上，90℃条件下烘干，在正极集流体的一面上形成厚度为110μm的正极活性材料层。在正极集流体铝箔的另一个表面上，重复以上步骤，得到双面涂覆有100μm正极活性材料层的正极极片。涂覆完成后，将正极极片裁切成38mm×58mm的规格待用。
制备例3：电解液的制备
在干燥氩气气氛中，首先将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)和碳酸二乙酯(DEC)以质量比EC:EMC:DEC＝30:50:20混合为溶剂，然后向溶剂中加入锂盐六氟磷酸锂(LiPF 6)溶解并混合均匀，得到锂盐浓度为1.15mol/L的电解液。
以下实施例举例说明根据本申请的纳米纤维多孔层+聚合物层的一体化隔离层的制备。这些实施例以正极极片为例进行说明，并且在正极极片的两个表面上沉积一体化隔离层。应当理解，所述的一体化隔离层也可以沉积在负极极片的两个表面上，或者在正极极片的一个表面上和负极极片的一个表面上分别沉积一层一体化隔离层，这些实施方案同样可以实现本申请的目的；此外，所述的一体化隔离层还可以是纳米纤维多孔层+无机化合物层的一体化隔离层。本领域技术人员，应当理解，这些实施方案同样在本申请的保护范围内。
实施例1
在制备例2中所得的正极极片的一个表面上通过电纺丝和气纺丝混合使用的方法，制备一层厚度为12μm的多孔层(成分为PVDF)，平均孔径为150nm，纳米纤维的直径为600nm；
将聚偏二氟乙烯与聚丙烯酸酯依照质量比96:4混合，并将其溶入到去离子水中以形成聚合物层浆料，聚偏二氟乙烯的Dv50为600nm。随后采用微凹涂布法将聚合物层浆料均匀涂布到多孔层的表面上，经过干燥处理以获得聚合物层；
聚合物层总覆盖面积比例为10％，单个聚合物团聚体的最大覆盖面积为0.1mm 2，聚合物团聚体嵌入多孔层深度为1μm，聚合物团聚体嵌入多孔层深度占聚合物团聚体厚度比例为25％，聚合物团聚体嵌入所述多孔层的深度占所述多孔层厚度的8.3％。隔离层的孔隙率为80％，厚度为15μm，换算成20μm时的透气度为112s/100cm 3。然后在该正极极片的另一个表面上重复上述步骤，并在90℃条件下干燥，去除聚合物层中的溶剂，得到双面涂布完成的正极极片。隔离层表面SEM照片如图1、图2所示。
实施例2
除了聚合物层的总覆盖面积比例为30％，隔离层换算成20μm时的透气度为123s/100cm 3以外，其余与实施例1相同。
实施例3
除了聚合物层的总覆盖面积比例为70％，隔离层换算成20μm时的透气度为137s/100cm 3以外，其余与实施例1相同。
实施例4
除了单个聚合物团聚体最大覆盖面积为1×10 -5mm 2，多孔层平均孔径为80nm以外，其余与实施例2相同。
实施例5
除了单个聚合物团聚体最大覆盖面积为0.01mm 2，多孔层平均孔径为100nm以外，其余与实施例2相同。
实施例6
除了单个聚合物团聚体最大覆盖面积为1mm 2，多孔层平均孔径为400nm以外，其余与实施例2相同。
实施例7
除了聚合物团聚体嵌入纳米纤维多孔层中的深度为0.5μm，聚合物团聚体嵌入多孔层深度占聚合物团聚体厚度比例为14％以外，其余与实施例5相同。
实施例8
除了聚合物团聚体嵌入纳米纤维多孔层中的深度为0.8μm，聚合物团聚体嵌入多孔层深度占聚合物团聚体厚度比例为21％以外，其余与实施例5相同。
实施例9
除了聚合物团聚体嵌入纳米纤维多孔层中的深度为1.5μm，聚合物团聚体嵌入多孔层深度占聚合物团聚体厚度比例为33％以外，其余与实施例5相同。
实施例10
除了聚合物团聚体嵌入纳米纤维多孔层中的深度为3.0μm，聚合物团聚体嵌入多孔层深度占聚合物团聚体厚度比例为50％以外，其余与实施例5相同。
实施例11
除了聚合物团聚体嵌入纳米纤维多孔层中的深度为5.0μm，聚合物团聚体嵌入多孔层深度占聚合物团聚体厚度比例为62.5％以外，其余与实施例5相同。
实施例12
除了聚合物团聚体嵌入纳米纤维多孔层中的深度为8.0μm，聚合物团聚体嵌入多孔层深度占聚合物团聚体厚度比例为72.5％以外，其余与实施例5相同。
实施例13
除了聚合物层具有条纹状图案以外，其余与实施例5相同。
实施例14
除了聚合物层具有点状图案以外，其余与实施例5相同。
实施例15
除了聚合物层具有块状图案以外，其余与实施例5相同。
实施例16
除了将多孔层的平均孔径调整到500nm以外，其余与实施例5相同。
实施例17
除了将多孔层厚度调整为4μm，聚合物团聚体嵌入多孔层深度为1μm，隔离层厚度为5μm，聚合物团聚体嵌入多孔层深度占聚合物团聚体厚度比例为50％以外，其余与实施例5相同。
实施例18
除了将隔离层孔隙率调整为95％以外，其余与实施例5相同。
实施例19
除了将纳米纤维材料替换为聚环氧乙烷(PEO)以外，其余与实施例5相同。
实施例20
在制备例2中得到的正极极片的一个表面上，通过电纺丝和气纺丝混合使用的方法，制备一层厚度为12μm的多孔层(成分为PVDF)，纳米纤维的直径为600nm，多孔层更靠近正极极片的区域平均孔径为100nm，多孔层更远离正极极片的区域平均孔径为500nm，多孔层的平均孔径从更靠近正极极片的区域向更远离正极极片的区域逐渐增大。
聚偏二氟乙烯与聚丙烯酸酯依照质量比96:4混合，并将其溶入到去离子水中以形成聚合物层浆料，聚偏二氟乙烯的Dv50为600nm。随后采用微凹涂布法将聚合物层浆料均匀涂布到多孔层的表面上，经过干燥处理以获得聚合物层。
聚合物层总覆盖面积比例为30％，单个聚合物团聚体最大覆盖面积为0.01mm 2，聚合物团聚体嵌入多孔层深度为1.5μm，聚合物团聚体嵌入多孔层深度占聚合物团聚体厚度比 例为50％，聚合物团聚体嵌入所述多孔层的深度占所述多孔层厚度的8.3％，隔离层的孔隙率为80％，厚度为15μm。然后在该正极极片的另一个表面上重复上述步骤，并在90℃条件下干燥，去除聚合物层中的溶剂，得到双面涂布完成的正极极片。
实施例21
负极极片的制备
将导电炭黑、丁苯橡胶按照重量比95:5进行混合，加入去离子水作为溶剂，调配成为固含量为0.8的浆料，并搅拌均匀。将浆料均匀涂覆在厚度为8μm的负极集流体铜箔的2个表面上，110℃条件下烘干，得到负极导电层，其单面厚度为2μm。
将负极活性材料石墨、导电炭黑、丁苯橡胶按照重量比96:1.5:2.5进行混合，加入去离子水作为溶剂，调配成固含量为0.7的浆料，搅拌均匀。将浆料均匀涂覆在上述导电层上，在110℃条件下烘干，得到厚度为130μm的单面涂覆负极活性材料的负极极片。在该负极极片的另一个表面上重复以上步骤，得到双面涂覆负极活性材料的负极极片。然后，将极片裁切成41mm×61mm的规格待用。
正极极片的制备
将导电炭黑、丁苯橡胶按照重量比97:3进行混合，加入去离子水作为溶剂，调配成固含量为0.85的浆料，搅拌均匀。将浆料均匀涂覆在厚度为10μm的正极集流体铝箔的2个表面上，110℃条件下烘干，得到正极导电层，其单面厚度为2μm。
将正极活性材料钴酸锂、导电炭黑、聚偏二氟乙烯按照重量比97.5:1.0:1.5进行混合，加入N-甲基吡咯烷酮(NMP)作为溶剂，调配成固含量为0.75的浆料，搅拌均匀。将浆料均匀涂覆于上述正极导电层上，90℃条件下烘干，得到双面涂覆有100μm正极活性材料层的正极极片。涂布完成后，将极片裁切成38mm×58mm的规格待用。
然后，重复实施例5的步骤。
实施例22
使用实施例21中得到的带有正极导电层的正极极片，按以下步骤制备隔离层。
在正极极片的一个表面上通过电纺丝和气纺丝混合使用的方法，制备一层厚度为12μm的多孔层(成分为PVDF)，平均孔径为100nm，纳米纤维的直径为600nm。
将勃姆石和羟甲基纤维素钠分散在二甲基甲酰胺/丙酮(7:3)溶剂中，搅拌均匀至浆料粘度稳定，得到质量分数为40％的悬浊液作为浆料，利用电喷涂的方法将悬浊液喷涂在上述 带有多孔层的正极极片的表面，形成无机化合物层，其厚度为3μm，电导率为10 8Ω·m，离子电导率为10 -5S/cm，平均孔径为0.5μm，无机颗粒嵌入所述多孔层的深度占所述多孔层厚度的8.3％，隔离层厚度为15μm。
实施例23
在制备例2中的正极极片表面通过电纺丝的方法，制备一层厚度为15μm的多孔层(成分为PVDF)，平均孔径为150nm，纳米纤维的直径为600nm；孔隙率为80％，换算成20μm时的透气度为112s/100cm 3，然后在该正极极片的另一个表面上重复上述步骤，并在90℃条件下干燥，得到双面涂布完成的正极极片。
锂离子电池的制备
将以上制备例1中制备的负极极片和各实施例中制备的带有隔离层的正极极片相对并叠好，用胶带将整个叠片结构的四个角固定好后，置入铝塑膜中，经过顶侧封，注入制备例3中的电解液，然后封装，得到锂离子叠片电池。其中，在实施例21中，用实施例21中的负极极片代替制备例1中的负极极片。
对比例1
选用厚度15μm的聚乙烯作为隔离膜，将其放置于制备例1和2的负极极片与正极极片之间作为隔离膜。将负极极片、正极极片和隔离膜相对并叠好。用胶带将整个叠片结构的四个角固定好后，置入铝塑膜中，经顶侧封、注入制备例中的电解液、封装后，最终得到锂离子叠片电池。
对比例2
在制备例2中的正极极片表面通过电纺丝的方法，制备一层厚度为15μm的PVDF无纺布纤维层，随后配制PVDF悬浊液，并在纤维层表面利用刮涂法制备一层致密的PVDF涂层，其在极片表面覆盖率为100％。纤维层平均孔径为50nm，孔隙率为80％。然后，在该正极极片的另一个表面重复上述步骤，并在90℃条件下烘干涂层中的溶剂和分散剂，即得到双面涂布完成的正极极片。
将涂布好的负极极片和正极极片相对并叠好，用胶带将整个叠片结构的四个角固定好后，置入铝塑膜中，经顶侧封、注入制备例中的电解液、封装后，最终得到锂离子叠片电池。
各实施例和对比例的数据和测试结果见表1。
Figure PCTCN2020081844-appb-000001
Figure PCTCN2020081844-appb-000002
从表1可以看出，与对比例1相比，本申请各实施例中隔离层与负极的粘结力明显增大，并且2C放电比容量与0.1C放电比容量比例显著提高。
与对比例2相比，2C放电比容量与0.1C放电比容量比例显著提高，并且50次充放电循环后的放电容量/首次放电容量明显提高，说明电池的循环性能明显提高。
另外，实施例23的隔离层中不含有聚合物团聚体，通过与其他实施例的比较可以看出，加入聚合物团聚体后，隔离层与负极的粘结力明显增大，电池的安全性得到提高。
以上所述仅为本申请的较佳实施例，并不用以限制本申请，凡在本申请的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本申请保护的范围之内。

Claims (15)

  1. 一种电化学装置，其包括电极极片以及形成在所述电极极片表面的隔离层，所述隔离层中包含形成在所述电极极片表面的多孔层；所述多孔层包含纳米纤维，所述隔离层的电解液注液性为15秒以下。
  2. 根据权利要求1所述的电化学装置，其中所述隔离层具有以下特征中的至少一者：
    (a)将所述隔离层的厚度换算为20μm时的透气度为5s/100cm 3～400s/100cm 3；
    (b)所述隔离层的孔隙率为30％～95％；
    (c)所述多孔层的平均孔径为20nm～10μm；
    (d)所述隔离层的厚度为1μm～20μm。
  3. 根据权利要求1所述的电化学装置，其中所述纳米纤维的直径为0.1nm～2μm。
  4. 根据权利要求1所述的电化学装置，其中所述纳米纤维包括聚偏二氟乙烯、聚酰亚胺、聚酰胺、聚丙烯腈、聚乙二醇、聚苯醚、聚碳酸亚丙酯、聚甲基丙烯酸甲酯、聚对苯二甲酸乙二醇酯、聚环氧乙烷、聚偏二氟乙烯-六氟丙烯或聚偏二氟乙烯-三氟氯乙烯中的至少一种。
  5. 根据权利要求1所述的电化学装置，其中所述隔离层还包括聚合物层，所述聚合物层设置于所述多孔层上，所述聚合物层的厚度为0.05μm～4μm，所述聚合物层在所述多孔层上的覆盖面积比例为10％～70％。
  6. 根据权利要求5所述的电化学装置，其中，所述聚合物层包括聚合物团聚体，所述聚合物团聚体具有以下特征中的至少一者：
    (a)所述聚合物层中单个聚合物团聚体的最大覆盖面积为1×10 -5mm 2～1mm 2，优选为0.001m 2～0.05mm 2；
    (b)所述聚合物层中的聚合物团聚体嵌入所述多孔层的深度占所述多孔层厚度的0.01％～80％；
    (c)所述聚合物层中的聚合物团聚体嵌入所述多孔层的深度占聚合物团聚体厚度的10％～80％。
  7. 根据权利要求5所述的电化学装置，其中所述聚合物层具有规则的图案。
  8. 根据权利要求1-4中任一项所述的电化学装置，其中所述隔离层还包括无机化合物层，所述无机化合物层包括无机颗粒，所述无机化合物层设置于所述多孔层上。
  9. 根据权利要求8所述的电化学装置，其中所述无机化合物层具有以下特征中的至少 一者：
    (a)所述无机化合物层中的部分无机颗粒嵌入所述多孔层中；
    (b)所述无机化合物层的无机颗粒嵌入所述多孔层的深度占所述多孔层厚度的0.01％～80％；
    (c)所述无机化合物层的电子电阻率大于10 7Ω·m；
    (d)所述无机化合物层的离子电导率为10 -8S/cm～10 -2S/cm；
    (e)所述无机化合物层的厚度为0.1μm～20μm；
    (f)所述无机化合物层的孔隙率为10％～40％，孔径为0.001μm～8μm。
  10. 根据权利要求8所述的电化学装置，其中所述无机化合物层通过喷涂或沉积设置。
  11. 根据权利要求8所述的电化学装置，其中所述无机化合物层和所述多孔层通过热压或粘合实现粘结。
  12. 根据权利要求1-11中任一项所述的电化学装置，其中所述多孔层的平均孔径在厚度方向上是变化的。
  13. 根据权利要求12所述的电化学装置，其中所述多孔层更靠近所述电极极片区域的平均孔径小于更远离所述电极极片区域的平均孔径。
  14. 根据权利要求1所述的电化学装置，其中所述多孔层通过电纺丝、气纺丝或离心纺丝制备。
  15. 一种电子装置，其包含根据权利要求1-14中任一项所述的电化学装置。
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