JP2008016193A - Method of manufacturing nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a nonaqueous electrolyte secondary battery capable of easily forming a space for alleviating stress generated by expansion caused by repeated charge/discharge in a wound-around body. <P>SOLUTION: The manufacturing method includes a process of superposing a cathode C, a first separator S1, an anode A, and a second separator S2, in a long belt shape, respectively, in that order, and integrally winding them around. Before superposing them, a spacer member P1 is arranged in discontinuity between the first separator S1 and the anode A over their length direction. The spacer member P1 is removed from the wound-around body obtained by the winding-around process. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  The present applicant has previously proposed a negative electrode for a non-aqueous electrolyte secondary battery that includes a pair of front and back surfaces that are in contact with the electrolyte and have conductivity, and an active material layer that includes active material particles between the surfaces. (See Patent Document 1). A metal material having a low lithium compound forming ability is infiltrated into the active material layer of the negative electrode, and active material particles are present in the infiltrated metal material. Since the active material layer has such a structure, even if the particles are pulverized due to expansion and contraction of the particles due to charge and discharge, the active material layer is unlikely to fall off. As a result, when this negative electrode is used, there is an advantage that the cycle life of the battery becomes long.

  However, when the negative electrode is wound together with the separator and the positive electrode to form a wound body, and a wound battery of a cylindrical type or the like is produced, the wound body expands in the radial direction by repeated charge and discharge. As a result, these members may not withstand the stress and may be damaged. The expansion is remarkable especially in the negative electrode. In order to relieve the stress due to expansion, it is conceivable to loosely wind by lowering the tension at the time of winding, but it is not easy to wind uniformly and gently from the beginning to the end of winding.

  Separately from the above technique, in a lithium secondary battery including a wound body in which a positive electrode and a negative electrode are wound via a separator, by disposing metallic lithium on the surface of the negative electrode before being incorporated in the battery, It has been proposed to improve the initial charge / discharge efficiency of the negative electrode and improve the discharge capacity (Patent Document 2). The metallic lithium disposed on the surface of the negative electrode is spontaneously dissolved using the potential difference at the contact interface as a driving force, and is occluded in the negative electrode. However, in the technique described in this document, even if lithium is occluded in the active material of the negative electrode, the problem that the active material is caused by expansion and contraction at the time of charge / discharge cannot be solved. It is impossible to prevent the wound body from expanding and damaging the member.

International Publication No. 2005/055345 Pamphlet JP 2004-363076 A

  An object of the present invention is to provide a method for producing a non-aqueous electrolyte secondary battery that can eliminate the various disadvantages of the above-described prior art.

The present invention is a non-aqueous electrolysis process comprising a step of superposing a positive electrode, a first separator, a negative electrode, and a second separator, which are each in the form of a long band, in this order, and winding them together. In the method for manufacturing a liquid secondary battery,
Prior to overlapping, between the first separator and the negative electrode, disposing discontinuous spacer members over the longitudinal direction of these members,
The object is achieved by providing a method for producing a non-aqueous electrolyte secondary battery, wherein the spacer member is removed from a wound body obtained by a winding process.

The present invention also includes a step of laminating a positive electrode, a first separator, a negative electrode, and a second separator, each of which is in the form of a long band, in this order and winding them together. In the method for producing an electrolyte secondary battery,
As the first separator, a surface in which spacer members are discontinuously attached to the surface facing the negative electrode among the surfaces of the first separator over the longitudinal direction of the first separator,
The object is achieved by providing a method for producing a non-aqueous electrolyte secondary battery, wherein the spacer member is removed from a wound body obtained by a winding process.

  According to the manufacturing method of the present invention, the winding density of the wound body is reduced by removing the spacer member disposed in the wound body in which the positive electrode and the negative electrode are wound through the separator. As a result, a space is formed in the wound body to relieve stress generated by expansion caused by repeated charge / discharge, and therefore, even when expansion occurs, these members can be effectively prevented from being damaged. . As a result, the cycle characteristics of the battery can be improved.

  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 nonaqueous electrolyte secondary battery called a cylindrical shape or a rectangular shape. FIG. 1 schematically shows a first embodiment of the manufacturing method of the present invention, and FIG. 2 shows an enlarged main part in FIG. In this embodiment, as shown in FIG. 1, first, the members constituting the battery are overlapped. The constituent members used here are the four members of the first separator S1, the second separator S2, the positive electrode C, and the negative electrode A. All of these members have a long strip shape. The widths of the first separator S1 and the second separator S2 are wider than the widths of the positive electrode C and the negative electrode A.

  In FIG. 1, spacer members P1 and P2 to be described later are already attached to the negative electrode A before winding, but this is shown for convenience in understanding the invention. Actually, as shown in FIG. 2, spacer members P1 and P2 are not attached to the negative electrode A before winding (the same applies to FIG. 5 described later).

  In the four members, the positive electrode C, the first separator S1, and the negative electrode A are overlapped in this order, and the second separator S2 is overlapped on the outer surface of the negative electrode A. These four members are wound together. In overlapping of each member, adjacent members are in contact only by overlapping, and are not joined by a joining means such as an adhesive. That is, each member is only in contact with each other so as to be mechanically peelable.

  The above-mentioned members are overlapped in the order described above, and these are wound to obtain a wound body (not shown). As shown in FIG. 1, the winding is performed so that the positive electrode C side faces inward. By winding in this way, in the wound body, the positive electrode C, the first separator S1, the negative electrode A, and the second separator S2 are arranged in layers in this order.

  The positive electrode C is formed by forming an active material layer (not shown) containing a positive electrode active material on each surface of a current collector (not shown). On the other hand, the negative electrode A is formed by forming an active material layer (not shown) containing a negative electrode active material capable of occluding and releasing lithium on each surface of a current collector (not shown).

  Prior to the superposition of these four members, as shown in FIG. 2, a first spacer member P1 is disposed between the first separator S1 and the negative electrode A over the longitudinal direction of these members. At the same time, a second spacer member P2 is disposed between the second separator S2 and the negative electrode A over the longitudinal direction of these members. Note that the positive electrode C is not shown in FIG. Both spacer members P1 and P2 are discontinuously arranged at a predetermined interval over the entire lengthwise direction of the negative electrode A or the like. The first spacer member P1 and the second spacer member P2 may have the same shape or different shapes. Further, the same material or different materials may be used. In the present embodiment, the first spacer member P1 and the second spacer member P2 have the same shape and the same material. Both spacer members P1, P2 are rectangular, and are arranged so that their long sides coincide with the width direction of the negative electrode A or the like. The lengths of the long sides of both spacer members P1, P2 are substantially the same as the width of the negative electrode A or the like, or shorter than that. Considering the ease of manufacturing, it is preferable that the length of the long sides of both spacer members P1, P2 is 80 to 95% of the width of the negative electrode A or the like.

  As shown in FIG. 3, the first spacer member P1 and the second spacer member P2 are arranged so as to be in a positional relationship that does not overlap each other when viewed in a plan view before being wound. ing. The spacer members P1 and P2 are arranged such that a gap G is formed between their adjacent long sides when they are viewed in a plan view before being wound. By arranging both spacer members P1 and P2 in this way, when a cylindrical wound body is configured, an excessive space is prevented from being formed between the negative electrode A and both separators S1 and S2. be able to. When excessive space is formed, sagging may occur in the wound body. Moreover, it can prevent that an unevenness | corrugation is formed in the surrounding surface of a cylindrical winding body by arrange | positioning both spacer members P1 and P2 in this way.

  Thus, winding is performed in a state in which both spacer members P1, P2 are interposed between the negative electrode A and both separators S1, S2. In the obtained wound body, the negative electrode A and both separators S1, S2 are in a state of being separated by the thickness of the spacer members P1, P2. Both spacer members P1, P2 are removed from the wound body in such a state. By removing both spacer members P1, P2, a space corresponding to the thickness of the removed spacer members P1, P2 is formed between the negative electrode A and both separators S1, S2. By forming this space, the stress generated by the expansion of the positive electrode C and the negative electrode A (particularly, the negative electrode A) due to repeated charge and discharge is alleviated. As a result, even if expansion occurs, the positive electrode C, the negative electrode A, and the separators S1 and S2 can be effectively prevented from being damaged. As a result, according to the method of the present embodiment, a non-aqueous electrolyte secondary battery having excellent cycle characteristics can be easily manufactured.

    When producing a 18650 type battery, it is sufficient that the spacer members P1 and P2 have a thickness of 10 to 200 μm, particularly 15 to 100 μm, between the negative electrode A and the separators S1 and S2. It is preferable from the point that a simple space can be formed. The spacer members P1 and P2 have a short side length of 5 to 100 mm, particularly preferably 5 to 30 mm. The gap G between adjacent long sides of the spacer members P1 and P2 is preferably 3 to 60 mm, particularly 5 to 50 mm, and particularly 10 to 30 mm.

  As means for removing both spacer members P1 and P2 from the wound body, in this embodiment, both spacer members P1 and P2 are made of metallic lithium, and the metallic lithium is occluded in the active material of the negative electrode A. A method of eliminating and removing the members P1 and P2 from the wound body is adopted. This method has an advantage that both spacer members P1 and P2 can be removed without applying an external force to the wound body. Moreover, since lithium can be occluded in the negative electrode active material before the first charge / discharge, there is an advantage that the capacity of the battery can be increased. Details of the method of occluding lithium in the negative electrode active material will be described later.

The wound body is accommodated in a bottomed cylindrical battery can (not shown). The battery can is made of iron whose inner surface is nickel-plated, for example. A non-aqueous electrolyte is injected into the battery can. 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. The details are not clear, but 1,4-butanediol dimethanesulfonate and divinylsulfone are decomposed stepwise to form a film on the positive electrode, so that the film containing sulfur becomes denser. It is thought that it is to become.

  In particular, non-aqueous electrolytes include 4-fluoro-1,3-dioxolan-2-one, 4-chloro-1,3-dioxolan-2-one or 4-trifluoromethyl-1,3-dioxolane-2- It is also preferable to use a high dielectric constant solvent having a relative dielectric constant of 30 or more, such as a cyclic carbonate derivative having a halogen atom such as ON. This is because it has high resistance to reduction and is not easily decomposed. Further, an electrolytic solution obtained by mixing the high dielectric constant solvent and a low viscosity solvent having a viscosity of 1 mPa · s or less such as dimethyl carbonate, diethyl carbonate, or methyl ethyl carbonate is also preferable. This is because higher ionic conductivity can be obtained. Furthermore, it is also preferable that the content of fluorine ions in the electrolytic solution is in the range of 14 mass ppm to 1290 mass ppm. This is because, when an appropriate amount of fluorine ions is contained in the electrolytic solution, a coating film such as lithium fluoride derived from fluorine ions is formed on the negative electrode, and it is considered that the decomposition reaction of the electrolytic solution in the negative electrode can be suppressed. . Furthermore, it is preferable that 0.001 mass%-10 mass% of at least 1 sort (s) of additives from the group which consists of an acid anhydride and its derivative (s) are contained. This is because a film is formed on the surface of the negative electrode, and the decomposition reaction of the electrolytic solution can be suppressed. As this additive, a cyclic compound containing a —C (═O) —O—C (═O) — group in the ring is preferable. For example, succinic anhydride, glutaric anhydride, maleic anhydride, phthalic anhydride, anhydrous Phthalic anhydride derivatives such as 2-sulfobenzoic acid, citraconic anhydride, itaconic anhydride, diglycolic anhydride, hexafluoroglutaric anhydride, 3-fluorophthalic anhydride, 4-fluorophthalic anhydride, or anhydrous 3,6 -Epoxy-1,2,3,6-tetrahydrophthalic acid, 1,8-naphthalic anhydride, 2,3-naphthalene carboxylic acid anhydride, 1,2-cyclopentane dicarboxylic acid anhydride, 1,2-cyclohexane dicarboxylic acid, etc. 1,2-cycloalkanedicarboxylic anhydride, or cis-1,2,3,6-tetrahydrophthalic anhydride or 3,4,5,6-tetrahydrophthal Tetrahydrophthalic anhydride such as acid anhydride, or hexahydrophthalic anhydride (cis isomer, trans isomer), 3,4,5,6-tetrachlorophthalic anhydride, 1,2,4-benzene Examples thereof include tricarboxylic acid anhydride, dianhydropyromellitic acid, and derivatives thereof.

  The opening of the battery can is closed by the battery lid. A battery is thus obtained. The configuration of the battery other than these is the same as the conventional one.

  A method of eliminating and removing both spacer members P1, P2 from the wound body by occluding lithium in the negative electrode active material is as follows. The wound body at the time of being accommodated in the battery can has spacer members P1 and P2. When the spacer members P1 and P2 come into contact with the nonaqueous electrolyte in the battery can, lithium constituting the spacer members P1 and P2 diffuses into the negative electrode active material. Thereby, the negative electrode active material occludes lithium. Hereinafter, this operation is called aging.

  The degree of lithium occlusion varies depending on the aging time and the aging temperature. From the viewpoint of efficiently storing a desired amount of lithium, the aging time is preferably 24 to 300 hours, particularly 24 to 100 hours. The aging temperature is preferably 10 to 80 ° C, particularly 20 to 60 ° C.

  The aging is preferably performed until the metallic lithium constituting the spacer members P1 and P2 is completely occluded in the negative electrode active material. If metallic lithium remains, lithium dendrite due to charge / discharge of the battery may occur using the remaining metallic lithium as a deposition site. This dendrite causes a short circuit of the battery.

The amount of metallic lithium is determined in relation to the amount of the negative electrode active material. Specifically, the occlusion amount of lithium is preferably set to 10 to 40%, more preferably 20 to 40%, and still more preferably 25 to 35% with respect to the initial charge theoretical capacity of the negative electrode active material. For example, when silicon is used as the negative electrode active material, theoretically, silicon occludes lithium to the state represented by the composition formula SiLi _4.4 , so that the occlusion amount of lithium is 100% of the initial charge theoretical capacity of silicon. That is, lithium is occluded by silicon up to the state represented by the composition formula SiLi _4.4 .

  From the viewpoint of forming a sufficient space between the negative electrode A and the separators S1 and S2, the thickness of the spacer members P1 and P2 can be increased, or the spacer members P1 and P2 can be arranged in a continuous state. Good. However, when such a means is adopted, the amount of metallic lithium is excessively large relative to the amount of the negative electrode active material, and the negative electrode active material cannot absorb all of lithium. In that case, metallic lithium remains in the battery. As described above, the remaining metallic lithium causes the generation of dendrites that cause a short circuit of the battery. In order to prevent this, in the method of the present embodiment, the spacer members P1 and P2 are discontinuously arranged to balance the amount of metallic lithium and the amount of negative electrode active material.

  As another method of eliminating and removing both spacer members P1, P2 from the wound body by occluding lithium in the negative electrode active material, the following method may be mentioned. In this method, the wound body is housed in a battery can, and the inside of the can is sealed with a battery lid to produce a battery, and then the battery is charged and discharged under predetermined conditions. By this charge and discharge, lithium constituting both spacer members P1 and P2 is occluded in the negative electrode active material.

  Specifically, as shown in FIG. 4, charging / discharging is performed using a constant current galvanostat 100. The galvanostat 100 includes a positive voltage probe 101 and a current probe 102, and a negative voltage probe 103 and a current probe 104. The positive voltage probe 101 and the current probe 102 are connected to the positive electrode of the battery 200. The negative voltage probe 103 and the current probe 104 are connected to the negative electrode of the battery 200. Usually, the voltage probes 101 and 103 are connected to the side closer to the battery terminal than the current probes 102 and 104.

  Charging / discharging conditions are appropriately set according to the type of active material. For example, lithium is used as the negative electrode active material, and lithium-containing metal composites such as lithium-transition metal composite oxides such as lithium nickel composite oxide, lithium manganese composite oxide, and lithium cobalt composite oxide are used as the positive electrode active material. When an oxide is used, it is preferable to perform charging / discharging comprising the following two steps.

(1) Charging at an environmental temperature of 10 to 70 ° C. at 0.5 C or lower for a predetermined time, and then leaving it for 1 to 48 hours as one step, this step is repeated twice or more until the charging potential becomes 4 V or higher.
(2) Discharge for a predetermined time at an ambient temperature of 10 to 70 ° C. at a temperature of 0.5 C or less, and then leave it for 1 to 48 hours as one step. repeat.

  In step (1), the above-described charging and leaving operation is a single step, and this step is repeated twice or more until the charging potential is 4 V or higher. There is no particular limitation on the number of times this process is repeated, but an increase in the number of times is not advantageous from the viewpoint of productivity. Therefore, it is preferable that the number of repetitions is at most 20, particularly at most 10. In this case, it is preferable to perform the charging operation in each step so that the charge amount is the same. The time for the leaving operation in each step may be the same or different.

  In the step (2), the above-described discharge and leaving operation is one step, and this step is repeated twice or more until the discharge potential becomes 3.3 V or less. There is no particular limitation on the number of times this process is repeated, but an increase in the number of times is not advantageous from the viewpoint of productivity. Therefore, it is preferable that the number of repetitions is at most 20, particularly at most 10. In this case, it is preferable to perform the discharge operation in each step so that the discharge amount is the same. The time for the leaving operation in each step may be the same or different.

  By performing charge and discharge comprising the above two steps, lithium can be uniformly occluded over the entire active material layer of the negative electrode. Note that 1 C discharging (charging) means, for example, discharging (charging) a battery having a capacity of 1000 mAh with a current of 1000 mA in one hour. Therefore, for example, when charging (discharging) at 0.5 C, it means that a 1000 mAh battery is discharged (charged) with a current of 1000 mA in 2 hours.

  Next, second and third embodiments of the present invention will be described with reference to FIGS. The present embodiment will be described only with respect to differences from the first embodiment, and the description detailed with respect to the first embodiment is applied as appropriate to points that are not particularly described. 5 to 8, the same members as those in FIGS. 1 to 3 are denoted by the same reference numerals.

  This embodiment is different from the first embodiment in that the long sides of the first and second spacer members P1 and P2 are larger than the width of the negative electrode A or the like. Further, the spacer members P1 and P2 having such a shape are arranged between the negative electrode A and both the separators S1 and S2 so that their longitudinal ends extend from the side edges of the negative electrode A or the like. This is also different from the first embodiment.

  Specifically, as shown in FIG. 6, with respect to the arrangement position of the first spacer member P1, the first short side M1 and the first side edge L1 such as the negative electrode A coincide with each other, and the second short side The end portion on the M2 side is arranged to extend from the second side edge L2 of the negative electrode A or the like. Regarding the second spacer member P2, the first short side N1 and the second side edge L2 of the negative electrode A and the like coincide with each other, and the end on the second short side N2 side is the first side of the negative electrode A and the like. It is arranged to extend from the edge L1.

  By arranging the first and second spacer members P1 and P2 in this way, the wound body R in the state shown in FIG. 7A is obtained. The wound body R has a cylindrical shape, and ends of both spacer members P1, P2 protrude from the upper and lower surfaces thereof.

  Next, both spacer members P1, P2 are removed from the wound body R in the state shown in FIG. As a means for removing both spacer members P1, P2 from the wound body R, in this embodiment, both spacer members P1, P2 are made of a material that is not occluded by the active material of the negative electrode A, and both spacer members P1, P2 are A method of pulling out and removing from the wound body R is adopted. In this case, the first spacer member P1 and the second spacer member P2 are pulled out simultaneously and at the same speed in directions opposite to each other by 180 degrees. By pulling out both spacer members P1, P2 under such conditions, both spacer members P1, P2 can be successfully removed without impairing the winding state of the wound body R.

  As described above, the spacer members P1 and P2 used in this embodiment are made of a material that is not occluded by the active material of the negative electrode A. Specifically, both spacer members P1, P2 can be made of plastic or paper. Both spacer members P1, P2 can also be made of metal.

  Next, a third embodiment of the present invention will be described. This embodiment is the same as the first embodiment, except that the arrangement of both spacer members P1, P2 is different from the first embodiment. Specifically, the first and second spacer members P1 and P2 are respectively attached in advance to the first and second separators S1 and S2, and these spacer members P1 and P2 are attached. The first and second separators S1 and S2 are wound together with the positive electrode C and the negative electrode A.

  As shown in FIG. 8, the first separator S1 has a first spacer member P1 at a predetermined interval across the longitudinal direction of the first separator S1 on the surface facing the negative electrode A of the two surfaces. It is mounted discontinuously. On the other hand, in the second separator S2, the second spacer member P2 is discontinuously attached to the surface facing the negative electrode A among the two surfaces over the longitudinal direction of the second separator S2 at a predetermined interval. ing. Although not shown, the spacer members P1 and P2 are both rectangular and are arranged so that their long sides coincide with the width direction of the separators S1 and S2. The long sides of the spacer members P1 and P2 are slightly shorter than the widths of the separators S1 and S2. Specifically, the length of the long sides of the spacer members P1, P2 is preferably 80 to 95% of the width of the separators S1, S2.

  The spacer members P1 and P2 used in the present embodiment are made of metallic lithium as in the first embodiment. When the metallic lithium comes into contact with the non-aqueous electrolyte in the battery can after the wound body is formed, it is occluded and removed by the active material of the negative electrode A. The spacer members P1 and P2 made of metallic lithium are attached to the separators S1 and S2 by a dry thin film forming method such as sputtering, vacuum deposition, laser ablation, or ion plating. Moreover, you may affix metal lithium foil to separator S1, S2.

  The first spacer member P1 and the second spacer member P2 are attached to the separators S1 and S2 so that when they are viewed in a plan view before they are wound, they are in a positional relationship that does not overlap each other. ing. Further, the spacer members P1, P2 are arranged such that a gap is formed between their adjacent long sides when viewed in plan. The advantage of arranging both spacer members P1 and P2 in this way is the same as in the first embodiment.

  According to the present embodiment, in addition to the effects exhibited in the first embodiment, there is an effect that spacer members P1 and P2 made of a thin metal lithium layer, for example, a metal lithium layer of 30 μm or less can be formed. With the current technology, it is not easy to form a metal lithium foil having a thickness of 30 μm or less.

  Next, details of members used in each of the above-described embodiments will be described. FIG. 9 shows a schematic diagram of a cross-sectional structure of an embodiment of the negative electrode used in the present invention. A negative electrode 10 shown in FIG. 9 includes a current collector 11 and an active material layer 12 formed on at least one surface thereof. Note that FIG. 9 shows a state in which the active material layer 12 is formed only on one side of the current collector 11 for convenience, but the active material layer may be formed on both sides of the current collector. .

  The active material layer 12 includes active material particles 12a. As the active material, a material capable of occluding and releasing lithium is used. The active material layer 12 is formed, for example, by applying a slurry containing active material particles 12a. Examples of the active material include silicon-based materials, tin-based materials, aluminum-based materials, and germanium-based materials. As the tin-based material, for example, an alloy containing tin, cobalt, carbon, and at least one of nickel and chromium is preferably used. Other examples of materials that can occlude and release lithium include carbon materials such as graphite, non-graphitizable carbon, and graphitizable carbon. According to the manufacturing method of the present invention, considering that it is possible to easily form a space between the negative electrode and the separator to relieve stress generated by the expansion of the negative electrode active material, among these various negative electrode active material materials, The advantage of the present invention is particularly remarkable when a silicon-based material, which is a material that causes a volume change, is used.

  As the silicon-based material, 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. Among these metals, Cu, Ni, and Co are preferable, and Cu and Ni are preferably used from the viewpoint of excellent electronic conductivity and a low ability to form a lithium compound. A particularly preferable silicon-based material is silicon or silicon oxide in view of the high occlusion amount of lithium.

  In the active material layer 12, at least a part of the surface of the particle 12a is covered with a metal material 13 having a low lithium compound forming ability. The metal material 13 is a material different from the constituent material of the particles 12a. Gaps are formed between the particles 12a coated with the metal material. That is, the metal material covers the surface of the particle 12a in a state in which a gap is ensured so that the non-aqueous electrolyte containing lithium ions can reach the particle 12a. In FIG. 9, the metal material 13 is conveniently represented as a thick line surrounding the periphery of the particle 12a. In the figure, among the particles 12 a included in the active material layer 12, there are particles that are drawn so that there is no contact with other particles. This is because the active material layer 12 is two-dimensionally illustrated. In fact, each particle is in direct contact with other particles or through the metal material 13. “Low lithium compound forming ability” means that lithium does not form an intermetallic compound or solid solution, or even if formed, lithium is in a very small amount or very unstable.

  The metal material 13 has conductivity, and examples thereof include copper, nickel, iron, cobalt, and alloys of these metals. In particular, the metal material 13 is preferably a highly ductile material in which even if the active material particles 12a expand and contract, the coating on the surface of the particles 12a is not easily broken. It is preferable to use copper as such a material.

  The metal material 13 is preferably present on the surface of the particle 12 over the entire thickness direction of the active material layer 12. The active material particles 12 a are preferably present in the matrix of the metal material 13. Thus, even if the particles 12a are pulverized due to expansion and contraction due to charge / discharge, the particles are less likely to fall off. In addition, since the electronic conductivity of the entire active material layer 12 is ensured through the metal material 13, the electrically isolated active material particles 12 a are generated, and in particular, the electrically isolated active material is deep in the active material layer 12. Generation of the particles 12a of the substance is effectively prevented. This is particularly advantageous when a material that is a semiconductor and has poor electron conductivity, such as a silicon-based material, is used as the active material. The presence of the metal material 13 on the surface of the active material particles 12a over the entire thickness direction of the active material layer 12 can be confirmed by electron microscope mapping using the material 13 as a measurement target.

  The metal material 13 coats the surface of the particle 12a continuously or discontinuously. When the metal material 13 continuously covers the surfaces of the particles 12a, it is preferable to form fine voids in the coating of the metal material 13 that allow the non-aqueous electrolyte to flow. When the metal material 13 discontinuously coats the surface of the particle 12a, the non-aqueous electrolyte is supplied to the particle 12a through a portion of the surface of the particle 12a that is not covered with the metal material 13. In order to form the coating of the metal material 13 having such a structure, the metal material 13 may be deposited on the surfaces of the particles 12a by, for example, electrolytic plating in accordance with conditions described later.

  The average thickness of the metal material 13 covering the surface of the active material particles 12a is preferably 0.05 to 2 μm, more preferably 0.1 to 0.25 μm. That is, the metal material 13 covers the surface of the active material particles 12a with a minimum thickness. As a result, while the energy density is increased, the particles 12a are prevented from falling off due to expansion / contraction and pulverization due to charge / discharge. Here, the “average thickness” is a value calculated based on a portion of the surface of the active material particle 12 a that is actually covered with the metal material 13. Accordingly, the portion of the surface of the active material particle 12a that is not covered with the metal material 13 is not used as a basis for calculating the average value.

  Gaps are formed between the particles 12 a covered with the metal material 13. This void serves as a flow path for the non-aqueous electrolyte containing lithium ions. Since the non-aqueous electrolyte easily reaches the active material particles 12a due to the presence of the voids, it is possible to reduce the overvoltage of the initial charge. As a result, lithium dendrite is prevented from being generated on the surface of the negative electrode. The generation of dendrite causes a short circuit between the two poles. The ability to reduce the overvoltage is also advantageous from the viewpoint of preventing decomposition of the non-aqueous electrolyte. This is because the irreversible capacity increases when the non-aqueous electrolyte is decomposed. Furthermore, the ability to reduce the overvoltage is advantageous in that the positive electrode is less susceptible to damage.

  Further, the voids formed between the particles 12a also have a function as a space for relieving stress caused by the volume change of the active material particles 12a due to charge and discharge. The increase in the volume of the active material particles 12a whose volume has been increased by charging is absorbed by the voids. As a result, pulverization of the particles 12a is difficult to occur, and significant deformation of the negative electrode 10 is effectively prevented.

  In addition, the void formed between the particles 12a also has a function of causing the particles 12a to occlude the metal lithium, which is a constituent material of the spacer members P1 and P2, described above. Specifically, lithium dissolved from the spacer members P1 and P2 smoothly diffuses in the thickness direction and the planar direction of the active material layer 12 through the gap. As a result, lithium is occluded uniformly throughout the active material layer 12. This is advantageous in that even if the spacer members P1 and P2 are discontinuously arranged, lithium is occluded uniformly.

  As described later, the active material layer 12 is preferably electrolyzed using a predetermined plating bath on a coating film obtained by applying a slurry containing particles 12a and a binder onto a current collector and drying the slurry. It forms by plating and depositing the metal material 13 between the particle | grains 12a.

  In order to form necessary and sufficient voids in the active material layer 12 in which the non-aqueous electrolyte can be circulated, it is preferable to sufficiently infiltrate the plating solution into the coating film. In addition to this, it is preferable to make conditions suitable for depositing the metal material 13 by electrolytic plating using the plating solution. The plating conditions include the composition of the plating bath, the pH of the plating bath, and the current density of electrolysis. Regarding the pH of the plating bath, it is preferable to adjust this to 7.1-11. By controlling the pH within this range, the dissolution of the active material particles 12a is suppressed, the surface of the particles 12a is cleaned, and plating on the particle surface is promoted. Is formed. The value of pH is measured at the temperature at the time of plating.

When using copper as the metal material 13 for plating, it is preferable to use a copper pyrophosphate bath. When nickel is used as the metal material, for example, an alkaline nickel bath is preferably used. In particular, it is preferable to use a copper pyrophosphate bath, even if the active material layer 12 is thick, because the voids can be easily formed over the entire thickness direction of the layer. Further, since the metal material 13 is deposited on the surface of the active material particles 12a and the metal material 13 is less likely to be deposited between the particles 12a, the voids between the particles 12a are also successfully formed. preferable. When using a copper pyrophosphate bath, the bath composition, electrolysis conditions and pH are preferably as follows.
Copper pyrophosphate trihydrate: 85-120 g / l
-Potassium pyrophosphate: 300-600 g / l
-Potassium nitrate: 15-65 g / l
-Bath temperature: 45-60 ° C
・ Current density: 1 to 7 A / dm ²
PH: Ammonia water and polyphosphoric acid are added to adjust the pH to 7.1 to 9.5.

In particular, when a copper pyrophosphate bath is used, it is preferable to use one having a P ratio defined by a ratio of P ₂ O ₇ weight to Cu weight (P ₂ O ₇ / Cu) of 5 to 12. . When the P ratio is less than 5, the metal material covering the active material particles 12a tends to be thick, and it may be difficult to form desired voids between the particles 12a. Further, when a P ratio exceeding 12 is used, current efficiency is deteriorated, and gas generation is likely to occur, so that production stability may be lowered. When a copper pyrophosphate bath having a P ratio of 6.5 to 10.5 is used as a more preferable copper pyrophosphate bath, the size and number of voids formed between the active material particles 12a may be reduced. This is very advantageous for the flow of the water electrolyte.

When an alkaline nickel bath is used, the bath composition, electrolysis conditions and pH are preferably as follows.
Nickel sulfate: 100 to 250 g / l
Ammonium chloride: 15-30 g / l
・ Boric acid: 15-45 g / l
-Bath temperature: 45-60 ° C
・ Current density: 1 to 7 A / dm ²
-PH: 25% by weight ammonia water: Adjust to pH 8-11 within the range of 100-300 g / l.
When this alkaline nickel bath and the above-described copper pyrophosphate bath are compared, there is a tendency that an appropriate void is formed in the active material layer 12 when the copper pyrophosphate bath is used, and the life of the negative electrode is increased. It is preferable because it is easy to plan.

  The characteristics of the metal material 13 can be appropriately adjusted by adding various additives used in the electrolytic solution for producing copper foil such as protein, active sulfur compound, and cellulose to the above various plating baths.

The ratio of the voids in the entire active material layer formed by the various methods described above, that is, the void ratio is preferably about 15 to 45% by volume, particularly about 20 to 40% by volume. By setting the porosity within this range, it is possible to form necessary and sufficient voids in the active material layer 12 that allow the nonaqueous electrolyte to flow. The porosity is measured by the following procedures (1) to (7).
(1) The weight per unit area of the coating film formed by applying the slurry is measured, and the weight of the particles 12a and the weight of the binder are calculated from the blending ratio of the slurry.
(2) From the weight change per unit area after electrolytic plating, the weight of the plated metal species is calculated.
(3) After electrolytic plating, the thickness of the active material layer 12 is determined by SEM observation of the cross section of the negative electrode.
(4) The volume of the active material layer 12 per unit area is calculated from the thickness of the active material layer 12.
(5) The respective volumes are calculated from the weight of the particles 12a, the weight of the binder, the weight of the plating metal species, and the respective compounding ratios.
(6) From the volume of the active material layer 12 per unit area, the volume of the voids is calculated by subtracting the volume of the particles 12a, the volume of the binder, and the volume of the plating metal species.
(7) The void volume calculated in this way is divided by the volume of the active material layer 12 per unit area, and a value obtained by multiplying by 100 is defined as a void ratio (%).

The porosity can also be controlled by appropriately selecting the particle size of the active material particles 12a. From this viewpoint, the particle 12a has a maximum particle size of preferably 30 μm or less, more preferably 10 μm or less. Moreover, when the particle diameter of the particle is expressed by a D ₅₀ value, it is preferably 0.1 to 8 μm, particularly preferably 0.3 to 4 μm. The particle size of the particles is measured by laser diffraction / scattering particle size distribution measurement and electron microscope observation (SEM observation).

  If the amount of the active material relative to the whole negative electrode is too small, it is difficult to sufficiently improve the energy density of the battery. Conversely, if the amount is too large, the strength decreases and the active material tends to fall off. Considering these, the thickness of the active material layer is 10 to 40 μm, preferably 15 to 30 μm, and more preferably 18 to 25 μm.

  In the negative electrode 10 of the present embodiment, a thin surface layer (not shown) may be formed on the surface of the active material layer 12. Further, the negative electrode 10 may not have such a surface layer. The thickness of the surface layer is 0.25 μm or less, preferably 0.1 μm or less. There is no restriction | limiting in the lower limit of the thickness of a surface layer.

  When the negative electrode 10 has the thin surface layer or does not have the surface layer, a secondary battery is assembled using the negative electrode 10 to reduce the overvoltage when the battery is initially charged. Can do. This means that lithium can be prevented from being reduced on the surface of the negative electrode 10 when the secondary battery is charged. The reduction of lithium leads to the generation of dendrites that cause a short circuit between the two electrodes.

  When the negative electrode 10 has a surface layer, the surface layer covers the surface of the active material layer 12 continuously or discontinuously. When the surface layer continuously covers the surface of the active material layer 12, the surface layer has a large number of microscopic voids (not shown) that are open at the surface and communicate with the active material layer 12. It is preferable. The fine voids are preferably present in the surface layer so as to extend in the thickness direction of the surface layer. The fine voids allow the non-aqueous electrolyte to flow. The role of the fine voids is to supply a non-aqueous electrolyte into the active material layer 12. When the surface of the negative electrode 10 is viewed in plan by electron microscope observation, the fine voids are such that the ratio of the area covered with the metal material 13, that is, the coverage is 95% or less, particularly 80% or less, especially 60% or less. It is preferable that the size is large.

  The surface layer is made of a metal material having a low lithium compound forming ability. This metal material may be the same as or different from the metal material 13 present in the active material layer 12. The surface layer may have a structure of two or more layers made of two or more different metal materials. Considering the ease of manufacture of the negative electrode 10, the metal material 13 present in the active material layer 12 and the metal material constituting the surface layer are preferably the same type.

  As the current collector 11 in the negative electrode 10, the same one as conventionally used as the current collector of the negative electrode for the non-aqueous electrolyte secondary battery can be used. The current collector 11 is preferably made of a metal material having a low lithium compound forming ability as described above. Examples of such metallic materials are as already described. In particular, it is preferably made of copper, nickel, stainless steel or the like. Also, it is possible to use a copper alloy foil represented by a Corson alloy foil. Further, as the current collector, a metal foil having a normal tensile strength (JIS C 2318) of preferably 500 MPa or more, for example, a copper film layer formed on at least one surface of the aforementioned Corson alloy foil can be used. Furthermore, it is preferable to use a current collector having a normal elongation (JIS C 2318) of 4% or more. This is because when the tensile strength is low, wrinkles are generated due to stress when the active material expands, and when the elongation is low, the current collector may crack. By using these current collectors, it is possible to further improve the folding resistance of the negative electrode 10 described above. The thickness of the current collector 11 is preferably 9 to 35 μm considering the balance between maintaining the strength of the negative electrode 10 and improving the energy density. In addition, when using copper foil as the electrical power collector 11, it is preferable to give the rust prevention process using organic compounds, such as a chromate process and a triazole type compound and an imidazole type compound.

  A preferred method for producing the negative electrode shown in FIG. 9 will be described with reference to FIG. In this manufacturing method, a coating film is formed on the current collector 11 using a slurry containing particles of an active material and a binder, and then electrolytic plating is performed on the coating film.

  First, a current collector 11 is prepared as shown in FIG. Then, a slurry containing active material particles 12 a is applied onto the current collector 11 to form a coating film 15. The slurry contains a binder and a diluting solvent in addition to the active material particles. The slurry may contain a small amount of particles of a conductive material such as acetylene black or graphite. In particular, when the active material particles 12a are made of a silicon-based material, the conductive carbon material is preferably contained in an amount of 1 to 3% by weight based on the weight of the active material particles 12a. When the content of the conductive carbon material is less than 1% by weight, the viscosity of the slurry is lowered and the sedimentation of the active material particles 12a is promoted, so that it is difficult to form a good coating film 15 and uniform voids. . On the other hand, if the content of the conductive carbon material exceeds 3% by weight, plating nuclei concentrate on the surface of the conductive carbon material, and it becomes difficult to form a good coating.

  As the binder, styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyethylene (PE), ethylene propylene diene monomer (EPDM), or the like is used. As a diluting solvent, N-methylpyrrolidone, cyclohexane or the like is used. The amount of the active material particles 12a in the slurry is preferably about 30 to 70% by weight. The amount of the binder is preferably about 0.4 to 4% by weight. A dilution solvent is added to these to form a slurry.

  The formed coating film 15 has a large number of minute spaces between the particles 12a. The current collector 11 on which the coating film 15 is formed is immersed in a plating bath containing a metal material having a low lithium compound forming ability. By immersion in the plating bath, the plating solution enters the minute space in the coating film 15 and reaches the interface between the coating film 15 and the current collector 11. Under this condition, electrolytic plating is performed to deposit plating metal species on the surfaces of the particles 12a (hereinafter, this plating is also referred to as permeation plating). The osmotic plating is performed by using the current collector 11 as a cathode, immersing a counter electrode as an anode in a plating bath, and connecting both electrodes to a power source.

  The deposition of the metal material by the osmotic plating is preferably progressed from one side of the coating film 15 to the other side. Specifically, as shown in FIGS. 10B to 10D, electrolytic plating is performed so that deposition of the metal material 13 proceeds from the interface between the coating film 15 and the current collector 11 toward the surface of the coating film. I do. By precipitating the metal material 13 in this way, the surface of the active material particles 12a can be successfully coated with the metal material 13, and a void is successfully formed between the particles 12a coated with the metal material 13. be able to. In addition, it becomes easy to set the void ratio of the voids to the above-described preferable range.

  As described above, the conditions of the infiltration plating for depositing the metal material 13 include the composition of the plating bath, the pH of the plating bath, the current density of electrolysis, and the like. Such conditions are as already described.

  As shown in FIGS. 10B to 10D, when plating is performed so that the deposition of the metal material 13 proceeds from the interface between the coating film 15 and the current collector 11 toward the surface of the coating film. In the forefront portion of the precipitation reaction, fine particles 13a made of plating nuclei of the metal material 13 are present in layers with a substantially constant thickness. As the deposition of the metal material 13 proceeds, adjacent microparticles 13a combine to form larger particles, and when the deposition proceeds further, the particles combine to continuously cover the surface of the active material particles 12a. It becomes like this.

  The permeation plating is terminated when the metal material 13 is deposited on the entire thickness direction of the coating film 15. By adjusting the end point of plating, a surface layer (not shown) can be formed on the upper surface of the active material layer 12. In this way, the target negative electrode is obtained as shown in FIG.

The positive electrode C used in the present embodiment 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, and drying. Then, it is obtained by roll rolling, pressing, further cutting and punching. As the positive electrode active material, conventionally known positive electrode active materials such as lithium-containing 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 separators S1 and S2 used in the present embodiment, a synthetic resin nonwoven fabric, a polyolefin such as polyethylene or polypropylene, a polytetrafluoroethylene porous film, or the like 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 present invention is not limited to the embodiment. For example, in the above-described embodiment, the first and second spacer members P1 and P2 are disposed over the entire longitudinal direction of the negative electrode A or the like, but may be disposed over a part of the longitudinal direction of the negative electrode A or the like instead. For example, the spacer members P1 and P2 may be disposed only at the winding start position, or may be disposed only at the winding end position.

  Further, the arrangement of the spacer members is not limited to the above embodiment. For example, as shown in FIG. 11A, narrow strip-like first and second spacer members P <b> 1 and P <b> 2 extending in the longitudinal direction of the negative electrode A may be arranged in multiple rows over the width direction of the negative electrode A. . Moreover, as shown in FIG.11 (b), you may arrange | position rectangular 1st and 2nd spacer members P1 and P2 in a checkered pattern. 11A and 11B, the first and second spacer members P1 and P2 have a positional relationship that does not overlap each other when the spacer members P1 and P2 are viewed in plan. It is preferable that it is arranged.

  Moreover, the structure of the negative electrode applied to the method of the present invention is not limited to that shown in FIG. For example, the negative electrode formed by applying a slurry containing particles of the negative electrode active material on a current collector to form a coating film, or the negative electrode formed by firing the coating film, the production method of the present invention Can be applied to. Furthermore, a negative electrode provided with a thin film of a negative electrode active material formed on a current collector by a dry thin film forming means such as sputtering or a wet thin film forming means such as electrolytic plating can be applied to the production method of the present invention. .

  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.

[Example 1]
This embodiment is an embodiment of the manufacturing method shown in FIG. First, a current collector made of an electrolytic copper foil having a thickness of 18 μm was acid-washed at room temperature for 30 seconds. After the treatment, it was washed with pure water for 15 seconds. A slurry containing Si particles was applied to each surface of the current collector to a thickness of 15 μm to form a coating film. The composition of the slurry was particles: styrene butadiene rubber (binder): acetylene black = 100: 1.7: 2 (weight ratio). The average particle diameter D ₅₀ of the Si particles was 2 μm. The average particle diameter D ₅₀ was measured using a Microtrac particle size distribution measuring device (No. 9320-X100) manufactured by Nikkiso Co., Ltd.

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 permeated to 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.
Copper pyrophosphate trihydrate: 105 g / l
-Potassium pyrophosphate: 450 g / l
・ Potassium nitrate: 30 g / l
-P ratio: 7.7
・ Bath temperature: 50 ° C
・ Current density: 3 A / dm ²
-PH: Ammonia water and polyphosphoric acid were added to adjust to pH 8.2.

  The permeation plating was terminated when copper was deposited over the entire thickness direction of the coating film. In this way, a target negative electrode was obtained.

The positive electrode was manufactured by applying a slurry containing LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ powder to each surface of an aluminum foil to form a coating film and drying the slurry. As the first and second separators, those having a thickness of 16 μm and a Gurley permeability of 300 seconds were used.

  The negative electrode, the positive electrode, and the first and second separators were formed in a long band shape having a width of 60 mm. These members were overlapped and wound in the order shown in FIG. Prior to winding, first and second spacer members made of metal lithium foil were disposed between the negative electrode and the first and second separators. The metal lithium foil had a long side length of 53 mm, a short side length of 20 mm, and a thickness of 30 μm. The gap G shown in FIG. 3 was set to 5 mm.

The obtained wound body was accommodated in an iron battery can whose inner surface was plated with nickel, and the inside thereof was filled with a non-aqueous electrolyte, and the battery can was sealed. As the non-aqueous electrolyte, a solution obtained by adding 2% by volume of vinylene carbonate to a solution obtained by dissolving 1 mol / l LiPF ₆ in a 1: 1 volume% mixed solvent of ethylene carbonate and diethyl carbonate was used.

This battery was connected to the apparatus shown in FIG. 4, and the lithium foil was occluded in the negative electrode silicon. In this way, the intended battery was obtained. The storage conditions were as follows.
(1) Charge to 10% of the battery capacity at 0.05 C, and then leave it for 6 hours. This operation is repeated as one unit until the battery voltage exceeds 4V. The number of repetitions was nine.
(2) Discharge up to 10% of the battery capacity at 0.05 C, and then leave it for 6 hours. This operation is repeated as one unit until the battery voltage becomes less than 2.8V. The number of repetitions was nine.

[Example 2]
Instead of the metal lithium foil used in Example 1, a spacer member made of nickel was used, and the manufacturing method shown in FIG. 5 was performed. The spacer member had a long side length of 80 mm, a short side length of 2.5 mm, and a thickness of 100 μm. The gap G shown in FIG. 3 was set to 100 mm. The spacer member was pulled out and removed from the wound body, and then the wound body was accommodated in a battery can and the battery can was sealed to obtain a target battery.

[Comparative Example 1]
In Example 1, when manufacturing the wound body, a battery was obtained in the same manner as in Example 1 except that the spacer member was not used and lithium was not occluded.

[Evaluation]
About the battery obtained by the Example and the comparative example, the capacity maintenance rate to 100 cycles was measured. The capacity retention rate was calculated by measuring the discharge capacity at each cycle, dividing those values by the initial discharge capacity, and multiplying by 100. The charging conditions were 0.5 C, 4.2 V, and a constant current / constant voltage (CCCV). The discharge conditions were 0.5 C, 2.7 V, and a constant current (CC). However, the first cycle was 0.05 C, the second to fourth cycles were 0.1 C, the fifth to seventh cycles were 0.5 C, and the eighth to tenth cycles were 1 C. As a result, the capacity retention rate of the battery of Example 1 was 95% and 80% in Example 2, whereas in the battery of Comparative Example 1, a short circuit occurred in the 50th cycle, and more Measurement was not possible. The reason why the short circuit occurred was that the electrode was damaged due to stress resulting from expansion of the negative electrode due to charge / discharge. As is clear from the comparison of the results of Example 1 and Example 2, it is understood that the cycle characteristics are further improved by preliminarily storing lithium in the negative electrode active material before the first charge / discharge.

It is a schematic diagram which shows 1st Embodiment of the manufacturing method of this invention. It is a principal part enlarged view in FIG. It is a schematic diagram which shows the arrangement | positioning state by the planar view of a spacer member. It is a schematic diagram which shows the state which occludes lithium in a negative electrode active material. It is a schematic diagram which shows 2nd Embodiment of the manufacturing method of this invention. It is a schematic diagram which shows the arrangement | positioning state by the planar view of a spacer member. It is a perspective view which shows the wound body which has a spacer member. It is a schematic diagram which shows 3rd Embodiment of the manufacturing method of this invention. It is a schematic diagram which shows the cross-section of one Embodiment of the negative electrode used for the manufacturing method of this invention. It is process drawing which shows the manufacturing method of the negative electrode shown in FIG. It is a schematic diagram which shows the arrangement | positioning state by the planar view of a spacer member.

Explanation of symbols

A negative electrode C positive electrode S1 first separator S2 second separator P1 first spacer member P2 second spacer member 10 negative electrode 11 current collector 12 active material layer 12a active material particles 13 metal having low lithium compound forming ability Material 15 Paint

Claims (9)

A nonaqueous electrolyte secondary battery comprising a step of superposing a positive electrode, a first separator, a negative electrode, and a second separator, each of which is in the form of a long strip, in this order and winding them together. In the manufacturing method of
Prior to overlapping, between the first separator and the negative electrode, disposing discontinuous spacer members over the longitudinal direction of these members,
A method for producing a non-aqueous electrolyte secondary battery, wherein the spacer member is removed from a wound body obtained by a winding process.   The manufacturing method according to claim 1, wherein the spacer member is made of metal lithium, and the spacer member is extinguished and removed from the wound body by occluding metal lithium in the active material of the negative electrode.   The manufacturing method according to claim 1, wherein the spacer member is made of a material that is not occluded by the active material of the negative electrode, and the spacer member is pulled out and removed from the wound body.   The manufacturing method according to any one of claims 1 to 3, wherein a spacer member is disposed discontinuously between the second separator and the negative electrode in the longitudinal direction of these members prior to superposition.   The spacer member disposed between the first separator and the negative electrode and the spacer member disposed between the second separator and the negative electrode are obtained when the spacer members are viewed in plan view. The manufacturing method according to any one of claims 1 to 4, wherein the manufacturing method is arranged so as to have a positional relationship that does not overlap each other. A nonaqueous electrolyte secondary battery comprising a step of superposing a positive electrode, a first separator, a negative electrode, and a second separator, each of which is in the form of a long strip, in this order and winding them together. In the manufacturing method of
As the first separator, a surface in which spacer members are discontinuously attached to the surface facing the negative electrode among the surfaces of the first separator over the longitudinal direction of the first separator,
A method for producing a non-aqueous electrolyte secondary battery, wherein the spacer member is removed from a wound body obtained by a winding process.   The manufacturing method according to claim 6, wherein a spacer member is discontinuously attached to a surface of the second separator facing the negative electrode over the longitudinal direction of the second separator.   The spacer member attached to the first separator and the spacer member attached to the second separator are arranged so as to have a positional relationship that does not overlap each other when the spacer members are viewed in plan. The manufacturing method according to claim 6 or 7. The manufacturing method according to claim 6, wherein the spacer member is made of metal lithium, and the spacer member is eliminated from the wound body by occluding metal lithium in the active material of the negative electrode.

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