JP2009104902A - Method for producing non-aqueous electrolyte secondary battery - Google Patents

Abstract

To provide a method for producing a non-aqueous electrolyte secondary battery capable of suppressing the expansion of a battery due to charge / discharge during normal use to a low level.
A non-aqueous electrolyte solution comprising a step of charging a battery can in which a wound body is formed by integrally winding a positive electrode, a negative electrode, and a separator interposed therebetween, and then charging the battery. This is a method for manufacturing a secondary battery. The wound body 10 is loaded into the battery can 12 having an excess space corresponding to the expansion volume of the wound body 10 caused by charging. Next, charging is performed in a state where the deformation of the battery can 12 due to the expansion of the wound body 10 is restricted.
[Selection] Figure 2

Description

  The present invention relates to a method for producing a non-aqueous electrolyte secondary battery such as a lithium secondary battery.

  In non-aqueous electrolyte secondary batteries such as lithium secondary batteries, internal pressure increases due to gas generated inside the battery due to battery charging and discharging, and expansion of the electrode during charging, thereby increasing thickness, etc. The battery may be deformed. The deformation of the battery causes the energy density to decrease. This tendency is conspicuous in a rectangular battery having a shape that is susceptible to pressure deformation as compared with a cylindrical battery. Furthermore, in the flat part of the square battery, an unreacted part is generated between the positive and negative electrodes due to the remaining of the generated gas and the swelling due to the gas, which may cause a decrease in capacity or increase the distance between the positive and negative electrodes. As a result, the uniform electrode reaction may be hindered.

  In order to solve the above-mentioned problem, in Patent Document 1, a flat wound group consisting of a positive electrode, a negative electrode and a separator and a nonaqueous electrolyte solution are inserted into a rectangular battery case, sealed and assembled, In the step of charging and finishing, a method for manufacturing a non-aqueous electrolyte secondary battery is described in which the central part of the maximum wide surface of the prismatic battery case is pressurized during or after charging. In this method, for example, the battery is charged to a final voltage of 4.07 V, and then a pressure of 120 kgf is applied to a flat portion in a range of 12 mm × 40 mm in the battery case to make the battery case 97% thick before pressurization.

JP 2007-5069 A

  The above-described manufacturing method is effective to some extent when a graphite-based negative electrode active material having a low degree of volume expansion resulting from charging is used. However, as a result of examination by the present inventors, it has been found that there is almost no effect when a silicon-based or tin-based material that is an active material having a large volume expansion is used. In addition, applying a high pressure of 120 kgf to a charged battery may be very dangerous in the manufacturing process.

  Accordingly, an object of the present invention is to provide a method for manufacturing a non-aqueous electrolyte secondary battery that can eliminate the above-mentioned drawbacks of the prior art.

The present invention includes a positive electrode and a negative electrode containing an active material capable of reversibly occluding and releasing lithium ions, and a wound body in which a separator interposed therebetween is integrally wound in a battery can. Then, in the method for producing a non-aqueous electrolyte secondary battery having a step of charging next,
The winding body is loaded into a battery can having a surplus space corresponding to the expansion volume of the winding body due to charging,
Next, the present invention provides a method for producing a non-aqueous electrolyte secondary battery, wherein charging is performed in a state where deformation of the battery can due to expansion of the wound body is regulated.

  According to the present invention, it is possible to suppress the expansion of the battery due to charging / discharging during normal use to an extremely low level.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The present embodiment relates to a method for manufacturing a rectangular nonaqueous electrolyte secondary battery. 1 and 2 schematically show a first embodiment of the manufacturing method of the present invention. In the present embodiment, first, a wound body 10 is prepared by superimposing members constituting a battery and winding them together. The members constituting the wound body 10 are a positive electrode, a negative electrode, and a separator. Each of these has a long strip shape.

  The positive electrode is formed by forming an active material layer containing a positive electrode active material capable of occluding and releasing lithium ions on each surface of a current collector. On the other hand, the negative electrode is formed by forming an active material layer containing a negative electrode active material capable of occluding and releasing lithium ions on each surface of a current collector. The separator is made of a liquid-permeable porous material that can permeate a non-aqueous electrolyte.

  The wound body 10 is manufactured by superposing the positive electrode, the first separator, the negative electrode, and the second separator in this order and winding them together. The winding direction may be a direction in which the positive electrode is inside, or a direction in which the second separator is inside. Alternatively, the wound body 10 is manufactured by superimposing the negative electrode, the first separator, the positive electrode, and the second separator in this order and winding them together. The winding direction may be a direction in which the negative electrode is inward, or a direction in which the second separator is inward. In either case, current extraction tabs 11 are attached to the positive and negative electrode current collectors, respectively.

  The wound body 10 is a flat body. The wound body 10 having such a shape is obtained by manufacturing a cylindrical wound body using the above-described members and then pressing the wound body in a direction perpendicular to the axial direction to deform it flatly. Can be obtained at Alternatively, a flat wound body 10 can be obtained directly by using a flat core and winding the above-described members integrally around the core. In this case, the winding core may be pulled out after winding or may be held in the wound body without being pulled out.

  The wound body 10 thus obtained is loaded into the battery can 12. Before the winding body 10 is loaded, an insulator (not shown) is arranged at the bottom of the battery can 12. A nonaqueous electrolyte solution is injected into the battery can 12 before, after, or simultaneously with the loading of the wound body 10. The battery can 12 has a flat rectangular tube shape with a bottom having an open top. That is, the battery can 12 is a square battery can. The battery can 12 has two maximum wide surfaces 12a and 12a facing each other. The maximum wide surface 12a is generally a flat surface. The battery can 12 is made of, for example, an Al—Mn alloy, an Al—Mn—Mg alloy, a steel plate with an inner surface plated with nickel, or the like.

  The manufacturing method of this embodiment has one of the characteristics in the relationship between the internal volume of the battery can 12 and the volume of the wound body 10. Specifically, the battery can 12 has a surplus space corresponding to the expansion volume of the wound body 10 resulting from charging in addition to the volume of the wound body 10. Usually, in the production of a non-aqueous electrolyte secondary battery, in order to increase the energy density of the battery as much as possible, the internal volume of the battery can is approximately equal to the volume of the wound body or slightly smaller than the volume of the wound body. It is designed to be large. That is, in a state where the wound body is loaded in the battery can, there is almost no gap between them. When the secondary battery in which the wound body is in such a loaded state is charged during normal use, the battery can expands due to expansion of the negative electrode. The technique described in Patent Document 1 described above is a technique for preventing this expansion deformation, and the winding state of the wound body in the same document is a state in which the wound body is closely fitted in the battery can as in the prior art. Therefore, even if the battery can is pressurized and charged in that state, it is extremely difficult to reliably prevent the battery can from expanding and deforming during normal use. On the other hand, in the present embodiment, the expansion volume of the wound body 10 resulting from charging is estimated in advance to adjust the internal volume of the battery can 12 and the volume of the wound body 10, and as will be described later, the battery can Since the battery is manufactured by charging under a state where the deformation of 12 is regulated, the wound body 10 expands in a form using the surplus space. As a result, deformation and expansion of the battery can during charging / discharging during normal use of the battery can be effectively prevented.

As a method for estimating the expansion volume of the wound body 10 in advance, for example, a method using the apparatus shown in FIG. The apparatus 100 shown in the figure includes a pair of rectangular metal plates 101 and 102 arranged opposite to each other, and bolts 103 that are attached to the four corners of the metal plates 101 and 102 and slidably fix the metal plates 101 and 102. A nut 104, an upper metal plate 101, and a spring 105 disposed between the nuts 104 are provided. The battery 110 to be measured is inserted between the two metal plates 101 and 102. The pressure of 0.45 kg / cm ² is applied to the battery 110 by adjusting the degree to which the nut 104 is tightened. The battery 110 includes a positive electrode 106 in which a positive electrode active material layer 106b is formed on one side of a current collector 106a, a negative electrode 107 in which a negative electrode active material layer 107b is formed on one side of a current collector 107a, and a separator 108 disposed between both electrodes. And a housing body 109 made of an aluminum laminate material or the like for housing these members. Each of the positive electrode 106, the negative electrode 107, and the separator 108 is planar, and these are used in the planar state to form a stack type single layer, which is housed in the housing 109 to form a battery. The battery 110 is charged and discharged under the same conditions as when the wound body 10 is used, and a change in thickness due to the expansion of the battery 110 is measured using a micrometer 111. In this case, since the change in the thickness of the positive electrode 106 is negligible, it can be approximated that the change in the thickness of the battery 105 is a change in the thickness of the negative electrode 107. Based on the value of the change in the thickness of the negative electrode 107 measured in this way, the expansion volume can be estimated from the number of windings of the wound body 10.

  When the wound body 10 is a flat body, when the wound body 10 expands due to charging, the portion with the greatest degree of expansion is the flat portion, that is, the maximum wide surface. Therefore, when the surplus space is provided in the battery can 12, the surplus space is provided at a portion corresponding to the maximum wide surface, which is a portion where the degree of expansion in the wound body 10 is the largest, so Is preferable because it can be more effectively prevented.

  When the wound body 10 is loaded into the battery can 12 and the non-aqueous electrolyte is injected, the battery is charged for the first time. Charging is performed in a state where deformation of the battery can 12 due to the expansion of the wound body 10 is restricted. Specifically, as shown in FIGS. 2 and 3, the battery can 12 loaded with the wound body 10 is sandwiched between the two press members 20 using the two flat press members 20 and 20, The deformation of the battery can 12 is restricted. It is effective to regulate the deformation on a portion where the battery can 12 is most easily deformed. From this viewpoint, the sandwiching by the two pressing members 20 is performed from the side of the maximum wide surface 12a in the battery can 12. The press member 20 is made of a high strength material such as stainless steel.

Each pressing member 20 has a rectangular shape having a predetermined thickness, and holes 22 for inserting bolts 21 are provided at four corners thereof. The battery can 12 loaded with the wound body 10 is sandwiched between the two press members 20, 20, and the bolt 21 is passed through the hole 22 in one press member 20, and the bolt 21 is inserted into the hole in the other press member 20. 22 is passed. Then, the bolt 21 is tightened with the nut 23 to fix the battery can 12 between the two press members 20 and 20. It is important that the fixing using the press member 20 is performed so that deformation of the battery can 12 due to expansion that occurs during charging is regulated. Therefore, as long as the deformation of the battery can 12 is restricted, the applied pressure may or may not be applied to the battery can 12 before charging by fixing using the two press members 20 and 20. Depending on the material of the press member 20 and the degree of expansion of the wound body 10, when the pressure is applied, the applied pressure is preferably 10 kg / cm ² or less, particularly 3 kg / cm ² or less.

  The battery can 12 is charged in a fixed state as shown in FIG. Charging may be performed with the battery can 12 sealed, or may be performed without sealing. If charging is performed without sealing, the gas generated during the first charge can be removed to the outside, so that the expansion deformation of the battery can 12 during charging and discharging during normal use can be more effectively prevented. is there. However, in this case, it is necessary to charge in a dry room where there is no moisture. On the other hand, when charging in a sealed state, there is no need to use a dry room. However, in this case, care must be taken so that the gas generated during the first charge does not accumulate in the battery can.

  There are no particular restrictions on the conditions for the initial charge, and it can be the same as the conventional one. Charging causes the electrodes, particularly the negative electrode, to expand, and thereby the wound body 10 expands. The expansion direction of the wound body 10 is mainly a direction orthogonal to the electrode surface. The increase in the volume of the wound body 10 due to this expansion is absorbed by the above-described excess space. In this case, if charging is performed in a state where the deformation of the battery can 12 is not restricted, the wound body 10 expands freely (disorderly) and the electrode plate is bent, so that the volume of the wound body 10 increases. Minutes cannot be successfully absorbed into the surplus space. On the other hand, according to the present embodiment, since the wound body 10 expands in a state in which the deformation of the battery can 12 is restricted, the increase in the volume of the wound body 10 can be successfully achieved without bending the electrode plate. It is well absorbed into the surplus space. As described above, in the present embodiment, (a) providing an extra space in the battery can 12 and (b) charging under a state in which the deformation of the battery can 12 is restricted (the wound body 10 is expanded). In other words, it is possible for the first time to effectively suppress the expansion deformation of the battery can during charging and discharging during normal use.

  When the first charge is completed, the first discharge is then performed. There are no particular restrictions on the conditions for the first discharge, and the conditions can be the same as in the prior art. The initial discharge may be performed while the regulation using the press member 20 is maintained, or may be performed in a state where the regulation using the press member 20 is released. The initial discharge may be performed with the battery can 12 sealed, or may be performed without sealing.

  When the first discharge is performed in a state where the regulation using the press member 20 is released, the battery can 12 is then sealed (when the first discharge is performed without sealing), and the intended secondary battery Get. When the first discharge is performed while maintaining the regulation using the press member 20, the regulation using the press member 20 is canceled to obtain the target secondary battery (however, when the sealing is not performed, the sealing is performed). I do). Alternatively, the second charging may be continued while maintaining the regulation using the press member 20 in a state where the battery can is sealed or not sealed. In general, it is preferable to repeatedly charge and discharge while maintaining the regulation using the press member 20 because the degree of expansion and deformation of the battery can during charge and discharge during normal use is further reduced. From this viewpoint, it is preferable that the number of times of charging / discharging while maintaining the regulation using the press member 20 is 2 times or more, particularly 3 times or more. Although there is no restriction | limiting in particular in an upper limit, It is preferable that it is 10 times or less from the point of productivity. When charging / discharging two times or more while maintaining the regulation using the press member 20, the battery can 12 may be in a sealed state or in a non-sealed state. Or you may be in the state which does not seal until the middle, and may be in the sealing state from the middle.

  Next, second to sixth embodiments of the present invention will be described with reference to FIGS. Regarding the points that are not particularly described with respect to these embodiments, the description regarding the first embodiment described above is appropriately applied. 4 to 9, the same members as those in FIGS. 2 and 3 are denoted by the same reference numerals.

  In the second embodiment shown in FIGS. 4 and 5, two auxiliary press members 24 are used to generate local pressure when the battery can 12 is sandwiched between the two press members 20. The auxiliary press member 24 is a rectangular flat plate having a predetermined thickness. The auxiliary press member 24 is smaller than the size of the maximum wide surface 12a in the battery can 12. The auxiliary press member 24 is disposed between the battery can 12 and the press member 20, and is opposed to and contacted with the central regions of the maximum wide surfaces 12 a facing each other in the battery can 12. When the bolts 21 and the nuts 23 are tightened under this arrangement state, only the central areas of the opposed wide surfaces 12a in the battery can 12 are selectively pressurized and the deformation of the battery can 12 is restricted. In the first embodiment described above, the two press members 20 suppress the expansion deformation of the battery can 12 during charging. In the present embodiment using the auxiliary press member 24, the auxiliary press member is used. The pressurizing force generated by 24 is positively applied to the battery can 12 in a state before charging. Since the central region of the maximum wide surface 12a is a portion having the largest degree of expansion and deformation in the battery can 12, the deformation of the battery can 12 can be effectively regulated by selectively pressurizing the portion. In addition, expansion deformation of the battery can during charging and discharging during normal use can be more effectively suppressed. In the present embodiment, a combination of the press member 20 and the auxiliary press member 24 may be used.

In the present embodiment, by appropriately adjusting the pressing force, the central region of the maximum wide surface 12a is pushed and plastically deformed by the auxiliary press member 24, and the distance between the central regions is increased as shown in FIG. It may be smaller than the previous distance. In the secondary battery thus obtained, expansion deformation of the battery can during charging and discharging during normal use can be further effectively suppressed. This is particularly effective when the secondary battery obtained by this manufacturing method is used in a device in which the fluctuation range of the battery volume is severely restricted, such as a mobile phone or a personal computer. From this viewpoint, it is preferable to selectively pressurize the central regions so that the distance between the central regions facing each other is 90 to 99%, particularly 93 to 98% of the distance before pressurization. The applied pressure at this time is preferably 0.5 to ²⁰ kg / cm ² , particularly preferably 1 to 5 kg / cm ² .

  While the embodiment described so far is a method of manufacturing one secondary battery, the third and fourth embodiments shown in FIGS. 6 and 7 include a plurality of secondary batteries. It relates to a method of manufacturing at the same time. In the embodiment shown in FIG. 6, a plurality of battery cans 12 are arranged in parallel between the two pressing members 20, 20, and the maximum wide surface of the plurality of battery cans 12 is pressed to provide the maximum wide width. The deformation of the surface is regulated. And charging / discharging is performed under this state.

  In the embodiment shown in FIG. 7, a plurality of battery cans 12 are arranged in parallel between two press members 20, 20, and an auxiliary press member 24 is arranged between adjacent battery cans 12. Further, an auxiliary press member 24 is also arranged between the press member 20 and the battery can 12. The bolts 21 and nuts 23 are tightened under this arrangement state, and only the central regions of the maximum wide surfaces facing each other in each battery can 12 are selectively pressurized to restrict deformation. And charging / discharging is performed under this state.

  The first to fourth embodiments described so far relate to a method for manufacturing a rectangular secondary battery. The fifth embodiment described below is a method for manufacturing a cylindrical secondary battery. It is related to.

  In the fifth embodiment shown in FIG. 8, a cylindrical wound body 10 is loaded into a bottomed cylindrical battery can 12 having an open top. The battery can 12 of the present embodiment also has an extra space corresponding to the expansion volume of the wound body 10 resulting from charging in addition to the volume of the wound body 10 in the same manner as the previous embodiments. Have. Since the wound body 10 in the present embodiment is cylindrical, expansion of the wound body 10 due to charging occurs substantially uniformly in the radial direction. Therefore, the position of the surplus space provided in the battery can 12 is defined by the inner wall of the battery can 12 and the outer surface of the wound body 10 when viewed from a direction orthogonal to the axial direction of the battery can 12. An annular region is preferred.

  When the wound body 10 is loaded into the battery can 12 and the non-aqueous electrolyte is injected, the battery is charged for the first time. Charging is performed in a state where deformation of the battery can 12 due to the expansion of the wound body 10 is restricted. Specifically, as shown in FIGS. 8 and 9, two press members 20 are used in which one side of a rectangular parallelepiped block is hollowed out into a semi-cylindrical shape. The curvature of the cutout portion 25 in the plan view of the press member 20 is the same as the curvature of the battery can 12 in the plan view. Using two press members 20, 20 having such a shape, the battery can 12 loaded with the wound body 10 is sandwiched between the cutout portions 25 of the two press members 20, and tightened with bolts 21 and nuts 23. The deformation of the battery can 12 is regulated. Charging is performed in this state. Charging conditions and other procedures are the same as in the above-described embodiment.

  The sixth embodiment shown in FIG. 9 is a modification of the embodiment shown in FIG. The embodiment shown in FIG. 8 is a method for manufacturing a single secondary battery, whereas the embodiment shown in FIG. 9 relates to a method for manufacturing a plurality of secondary batteries simultaneously. In the present embodiment, two press members 20 similar to those used in the embodiment shown in FIG. 8 are used. In addition to this, one or more of the same positions of the two opposite side surfaces in the rectangular parallelepiped block body, which are hollowed out in a semi-cylindrical shape, are used as the second press member 20 ′ (four in FIG. 9 are used). ing.). The shape of the cutout portion is the same as the shape of the cutout portion in the press member 20.

  The press member 20 and the second press member 20 'are arranged in series so that they are aligned in a straight line. In this case, the two press members 20 are arranged so as to be located at both ends, respectively, and the second press member 20 ′ is arranged so as to be located between the two press members 20. A semi-cylindrical cutout portion 25 faces between the press member 20 and the second press member 20 ′, and a semicylindrical cutout portion also exists between two adjacent second press members 20 ′. Are designed to face each other. Under such an arrangement state, the battery can 12 loaded with the wound body is sandwiched between the two cut-out portions facing each other, and the bolt 21 and the nut 23 are tightened to restrict deformation of the battery can 12. Charging is performed in this state.

Next, details of members used in each of the above-described embodiments will be described. The positive electrode is prepared by suspending a positive electrode active material and, if necessary, a conductive agent and a binder in an appropriate solvent to produce a positive electrode mixture, applying this to a current collector made of aluminum or the like, drying, roll rolling, pressing It is obtained by further cutting and punching. That is, the positive electrode is one in which a positive electrode active material layer is formed on one surface or both surfaces of a current collector. As the positive electrode active material, conventionally known positive electrode active materials such as lithium-containing transition metal composite oxides such as lithium nickel composite oxide, lithium manganese composite oxide, and lithium cobalt composite oxide are used. Further, as the positive electrode active material, a lithium transition metal composite oxide in which LiCoO ₂ contains at least both Zr and Mg, a lithium transition metal composite oxide having a layered structure and containing at least both Mn and Ni, A mixture thereof can also be preferably used. The use of such a positive electrode active material can be expected to increase the end-of-charge voltage without deteriorating charge / discharge cycle characteristics and thermal stability. The average value of the primary particle diameter of the positive electrode active material is preferably 5 μm or more and 10 μm or less in view of the packing density and the reaction area, and the weight average molecular weight of the binder used for the positive electrode is 350,000 or more and 2,000. It is preferable that the polyvinylidene fluoride is 1,000 or less. This is because it can be expected to improve discharge characteristics in a low temperature environment.

  As the negative electrode, one in which an active material layer containing a negative electrode active material is formed on one surface or both surfaces of a current collector is used. Examples of the negative electrode active material include graphite-based materials such as natural graphite, artificial graphite, hard carbon, and soft carbon, silicon-containing materials, tin-containing materials, aluminum-containing materials, and germanium-containing materials. As the material containing tin, for example, an alloy containing tin, cobalt, carbon, and at least one of nickel and chromium is preferably used. In order to improve the capacity density per weight of the negative electrode, a material containing silicon is particularly preferable. In addition, since the material containing silicon and the material containing tin have a very large degree of expansion at the time of charging, the effect is most prominent when the manufacturing method of the present invention is performed.

  As a material containing silicon, a material that can occlude lithium and contains silicon, for example, silicon alone, an alloy of silicon and metal, silicon oxide, or the like can be used. These materials can be used alone or in combination. Examples of the metal include one or more elements selected from the group consisting of Cu, Ni, Co, Cr, Fe, Ti, Pt, W, Mo, and Au. Of these metals, Cu, Ni, and Co are preferable. In particular, Cu and Ni are desirably used from the viewpoint of excellent electronic conductivity and low ability to form a lithium compound. Further, lithium may be occluded in an active material made of a material containing silicon before or after the negative electrode is incorporated in the battery. A particularly preferable silicon-containing material is silicon alone or silicon oxide in view of the high occlusion amount of lithium.

  The negative electrode active material layer can be formed by a dry thin film manufacturing method such as physical vapor deposition or chemical vapor deposition, or a wet thin film manufacturing method such as electrolytic plating or electroless plating. Alternatively, a slurry containing particles containing an active material can be applied onto a current collector to form a coating film, and the coating film can be sintered to form an active material layer. Moreover, the negative electrode active material layer which has a structure as described in WO2007 / 46327 concerning the previous application of the present applicant can also be adopted. The negative electrode active material layer described in this publication has particles containing an active material, and at least a part of the surface of the particles is coated with a metal material having a low ability to form a lithium compound and is coated with the metal material. A void is formed between the formed particles. The metal material is present throughout the active material layer in the thickness direction, and forms a conductive network.

  As the separator, a synthetic resin nonwoven fabric, a polyolefin such as polyethylene or polypropylene, or a polytetrafluoroethylene porous film is preferably used. In particular, for example, a porous polyolefin film (manufactured by Asahi Kasei Chemicals; N9420G) can be preferably used as the separator. From the viewpoint of suppressing the heat generation of the electrode that occurs when the battery is overcharged, it is preferable to use a separator in which a thin film of a ferrocene derivative is formed on one side or both sides of a polyolefin microporous membrane. The separator preferably has a puncture strength of 0.2 N / μm thickness or more and 0.49 N / μm thickness or less, and a tensile strength in the winding axis direction of 40 MPa or more and 150 MPa or less. This is because even when a negative electrode active material that greatly expands and contracts with charge and discharge is used, damage to the separator can be suppressed, and occurrence of internal short circuits can be suppressed.

The nonaqueous electrolytic solution is a solution in which a lithium salt as a supporting electrolyte is dissolved in an organic solvent. Examples of the lithium salt include LiClO ₄ , LiA1Cl ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiSCN, LiCl, LiBr, LiI, LiCF ₃ SO ₃ , LiC ₄ F ₉ SO _{3 and the} like. Examples of the organic solvent include ethylene carbonate, diethyl carbonate, dimethyl carbonate, propylene carbonate, butylene carbonate, and the like. In particular, 0.5 to 5% by weight of vinylene carbonate and 0.1 to 1% by weight of divinyl sulfone and 0.1 to 1.5% by weight of 1,4-butanediol dimethanesulfonate with respect to the whole non-aqueous electrolyte. It is preferable from the viewpoint of further improving the charge / discharge cycle characteristics.

  As mentioned above, although this invention was demonstrated based on the preferable embodiment, this invention is not restrict | limited to the said embodiment. For example, in the above embodiment, the embodiment shown in FIGS. 2 and 4 is intended for a single prismatic battery, but instead, a state in which a plurality of prismatic single cells are stacked. The battery may be the target.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, “%” and “part” mean “% by weight” and “part by weight”, respectively.

[Example 1]
(1) Production of positive electrode LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ was used as a positive electrode active material. This was suspended in N-methylpyrrolidone as a solvent together with acetylene black and polyvinylidene fluoride to obtain a positive electrode mixture. The weight ratio of the blending was positive electrode active material: acetylene black: polyvinylidene fluoride = 88: 6: 6. This positive electrode mixture was applied to each surface of a current collector made of aluminum foil (thickness 20 μm) using an applicator, dried at 120 ° C., and then subjected to a roll press with a load of 0.5 ton / cm. Obtained.

(2) Manufacture of negative electrode A negative electrode was manufactured according to the method described in WO2007 / 46327 related to the previous application of the present applicant. A current collector made of an electrolytic copper foil having a thickness of 18 μm was acid washed at room temperature for 30 seconds. Subsequently, it was washed with pure water for 15 seconds. Si particles having an average particle diameter D ₅₀ of 2.5 μm were used as the active material particles. 1.7 parts of styrene butadiene rubber as a binder was used with respect to 100 parts of the active material particles. Further, acetylene black as a conductive material was used in 2 parts. These were dispersed in N-methylpyrrolidone to form a slurry. This slurry was applied to each surface of the current collector so as to have a film thickness of 15 μm to form a coating film. The current collector on which the coating film was formed was immersed in a copper pyrophosphate bath having the following bath composition, and copper was plated on the coating film by electrolysis to form an active material layer. The electrolysis conditions were as follows. DSE was used for the anode. A DC power source was used as the power source. In the negative electrode active material layer thus obtained, at least part of the surface of the active material particles was covered with copper, and voids were formed between the copper-coated particles. . The copper coating was present throughout the active material layer in the thickness direction.
Copper pyrophosphate trihydrate: 105 g / l
-Potassium pyrophosphate: 450 g / l
・ Potassium nitrate: 30 g / l
・ Bath temperature: 50 ° C
・ Current density: 3 A / dm ²
-PH: Ammonia water and polyphosphoric acid were added to adjust to pH 8.2.

(3) Manufacture of lithium secondary battery The obtained positive electrode and negative electrode were used together with a separator made of a polypropylene porous film to obtain a cylindrical wound body. The wound body was pressed from a direction orthogonal to the axial direction to form a flat body. The expansion volume due to charging / discharging of this flat wound body was 150% with respect to the volume before expansion. The wound body was loaded into a prismatic battery can having an excess space corresponding to the expanded volume, and a non-aqueous electrolyte was further injected. And the battery can was attached to the apparatus shown in FIG. 2, and the deformation | transformation of the battery can was controlled as shown in FIG. At this time, no pressure was applied to the battery can. Under this condition, first charge / discharge was performed. Charging / discharging was performed without sealing the battery can. The charging conditions were a final voltage of 4.2 V, a rate of 0.05 C, and a constant current / constant voltage. The discharge conditions were a constant current at a final voltage of 2.7 V and a rate of 0.05 C. After completion of the discharge, the deformation restriction state was released, and the battery can was sealed by a conventional method to obtain the intended lithium secondary battery. These series of operations were performed in a dry room. The pressure generated by the expansion of the battery can during charging was 10 kg / cm ² at maximum.

[Example 2]
Charging / discharging was repeated twice while maintaining the deformation restricted state using the press member. Thereafter, a lithium secondary battery was obtained in the same manner as in Example 1. The initial charge / discharge conditions were the same as in Example 1. The second charging / discharging conditions were the same as the first charging / discharging conditions.

Example 3
Charging / discharging was repeated 5 times while maintaining the restricted state of deformation using the press member. Thereafter, a lithium secondary battery was obtained in the same manner as in Example 1. The initial charge / discharge conditions were the same as in Example 1. The charging conditions after the sixth time were a constant current and a constant voltage at a final voltage of 4.2 V and a rate of 0.5 C. The discharge conditions were a final voltage of 2.7 V and a constant current of 0.5 C.

[Comparative Example 1]
The volume of the wound body was adjusted so that the inner volume of the battery can and the volume of the wound body were substantially the same. This wound body was loaded into a battery can. In the loaded state, there was almost no gap between the inner wall of the battery can and the outer surface of the wound body. The battery can was charged and discharged once in the same manner as in Example 1 without sealing the battery can. The deformation of the battery can during charging / discharging was not regulated. Thereafter, a lithium secondary battery was obtained in the same manner as in Example 1.

[Comparative Example 2]
This comparative example is a method similar to the method described in Patent Document 1. In Comparative Example 1, after charging was completed, the battery can was deformed by applying a pressure of 10 kg / cm ² to the battery can. The distance between the maximum wide surfaces in the pressed state was 95% of the distance before pressing. Thereafter, a lithium secondary battery was obtained in the same manner as in Example 1.

[Evaluation]
Charging / discharging was repeated about the battery obtained by the Example and the comparative example. The charging conditions were a final voltage of 4.2 V, a rate of 0.5 C, and a constant current / constant voltage. The discharge conditions were a final voltage of 2.7 V and a constant current of 0.5 C. And the expansion coefficient of the battery when the 1st charge was completed and the expansion coefficient of the battery when the 100th charge was completed were measured. The results are shown in Table 1. The number of samples was set to n = 5 in each example and each comparative example. The expansion coefficient of the battery was measured by the following method.

[Measurement method of battery expansion coefficient]
Using a micrometer, the increase in thickness at the central portion of the maximum wide surface of the battery was measured, and the expansion coefficient was calculated from the value.

  As is clear from the results shown in Table 1, it can be seen that the battery obtained in the example has a smaller expansion coefficient at the time of charging than the battery obtained in the comparative example. In particular, in the battery obtained in the comparative example, when the charge / discharge cycle is repeated, the rate of increase in the expansion rate becomes very large, whereas in the battery obtained in the example, the charge / discharge cycle is repeated. It can be seen that the rate of increase of the expansion rate remains in a small range.

It is a disassembled perspective view which shows 1st Embodiment of the manufacturing method of this invention. It is a figure which shows the charge condition of the battery in 1st Embodiment. It is a schematic diagram which shows the apparatus which estimates the expansion | swelling volume of the battery resulting from charge. It is a disassembled perspective view which shows 2nd Embodiment of the manufacturing method of this invention. It is a figure which shows the charge condition of the battery in 2nd Embodiment. It is a figure which shows the charge condition of the battery in 3rd Embodiment. It is a figure which shows the charge condition of the battery in 4th Embodiment. It is a disassembled perspective view which shows 5th Embodiment of the manufacturing method of this invention. It is a figure which shows the charge condition of the battery in 6th Embodiment.

Explanation of symbols

10 Winding body 12 Battery can 20 Press member 24 Auxiliary press member

Claims (7)

A positive electrode and a negative electrode containing an active material capable of reversibly occluding and releasing lithium ions, and a wound body in which a separator interposed between them is wound together are loaded into a battery can, and then charged. In the method for producing a non-aqueous electrolyte secondary battery having a step of performing,
The winding body is loaded into a battery can having a surplus space corresponding to the expansion volume of the winding body due to charging,
Next, charging is performed in a state where deformation of the battery can due to expansion of the wound body is restricted, and a method for manufacturing a nonaqueous electrolyte secondary battery.   2. The non-aqueous electrolyte 2 according to claim 1, wherein the surplus space is provided in a portion in the battery can corresponding to a portion where the degree of expansion is greatest when the wound body expands due to charging. A method for manufacturing a secondary battery.   The wound body is a flat body, the battery can is a rectangular battery can, and the surplus space is provided in a portion in the battery can corresponding to the maximum wide surface of the wound body. A method for producing a non-aqueous electrolyte secondary battery according to 1 or 2.   The method for manufacturing a non-aqueous electrolyte secondary battery according to claim 3, wherein charging is performed while selectively pressing only the central regions of the opposite wide surfaces of the rectangular battery can, and the deformation of the battery can is regulated. .   The method for producing a non-aqueous electrolyte secondary battery according to claim 4, wherein pressurization is performed so that a distance between the opposed central regions is 85 to 99% of a distance before pressurization.   The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein charging is performed in a state where the battery can is not sealed.   The method for manufacturing a non-aqueous electrolyte secondary battery according to claim 1, wherein the negative electrode active material is made of a material containing silicon or tin.

Images