JP4891555B2 - Method for producing non-aqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a method for producing a nonaqueous electrolyte secondary battery such as a lithium secondary battery and a nonaqueous electrolyte secondary battery.

  In order to improve the energy density of a non-aqueous electrolyte secondary battery such as a lithium secondary battery, it is necessary to increase the amount of active material for the battery. For this purpose, it is conceivable to thin the current collector, which is one of the constituent members of the battery. Accordingly, for example, when a battery of a jelly roll type is manufactured, the number of windings can be increased, and the capacity of the battery can be increased. For example, Patent Document 1 proposes a negative electrode in which an active material layer is formed on both sides of a copper foil used as a current collector, and the thickness of the copper foil is 0.1 μm to 7 μm.

  However, when the number of windings is increased, the negative electrode or the like may be stretched due to the difference in the winding diameter between the central portion and the outer peripheral portion of the wound body, which may cause the negative electrode or the like to break. This is particularly noticeable when a flat rectangular package is manufactured by pressing a cylindrical wound body.

JP 2003-151561 A

  Accordingly, an object of the present invention is to provide a method for producing a non-aqueous electrolyte secondary battery such as a lithium secondary battery and the like and the non-aqueous electrolyte secondary battery capable of eliminating the above-described drawbacks of the prior art.

The present invention is a respective long strip shape, the positive electrode and, a first separator, a first negative electrode having no Atsumakushirube conductor thickness 12～35Myuemu, the conductive core member, the thickness And a second negative electrode not having a thick film conductor having a thickness of 12 to 35 μm are superposed in this order, and a second separator is arranged outside the positive electrode or outside the second negative electrode. The object is achieved by providing a method for producing a non-aqueous electrolyte secondary battery, wherein the separator is wound so as to be inside.

The present invention also includes a positive electrode, a first separator, a first negative electrode not having a thick film conductor having a thickness of 12 to 35 μm, a conductive core, each having a long strip shape. A superposed body in which a second negative electrode not having a thick film conductor having a thickness of 12 to 35 μm is superposed in this order, and a second separator is arranged outside the positive electrode or outside the second negative electrode. Is a lithium secondary battery provided with a wound body wound so that the second separator is inside,
The object is achieved by providing a non-aqueous electrolyte secondary battery characterized in that the first and second negative electrodes and the conductive core material are in electrical contact so as to be peelable. Is.

  According to the present invention, it is possible to prevent the electrodes from being broken during the winding operation of the electrodes and the like during battery production.

  The present invention will be described below based on preferred embodiments with reference to the drawings. In this embodiment, a battery called a square package is manufactured. The manufacturing method of this embodiment is characterized by employing a configuration in which a negative electrode not having a thick film conductor is used and the negative electrode is wound together with a conductive core material. Unlike the manufacturing method of the present embodiment, in a conventional battery manufacturing method, at least one surface of a thick film conductor for current collection (for example, a metal foil or expanded metal having a thickness of about 12 to 35 μm) generally called a current collector The negative electrode on which the negative electrode active material layer was formed was wound together with the separator and the positive electrode. That is, in the manufacturing method of the present embodiment, instead of the negative electrode composed of the negative electrode active material layer and the thick film conductor that are integrally wound by the conventional method, a member substantially composed of the negative electrode active material; The thick film conductor is handled as a separate member, and these separate members are overlapped and wound. Therefore, in the following description, the negative electrode of the present embodiment, that is, the negative electrode that is substantially composed of the negative electrode active material and does not have the thick film conductor, is the negative electrode in the conventional battery, that is, the negative electrode on the thick film conductor. In order to clarify that the active material layer has a structure different from that of the negative electrode formed integrally, the negative electrode of this embodiment is referred to as a negative electrode active material sheet.

  FIG. 1 shows an example of a negative electrode active material sheet used in the present embodiment. The negative electrode active material sheet 10 has a first surface 1a and a second surface 1b which are a pair of front and back surfaces. The negative electrode active material sheet 10 includes an active material layer 2. The active material layer 2 is continuously covered with a pair of surface layers 3 a and 3 b formed on each surface of the layer 2. Each surface layer 3a, 3b includes a first surface 1a and a second surface 1b, respectively. As is clear from FIG. 1, the negative electrode active material sheet 10 does not have a current collecting thick film conductor called a current collector, which has been used for conventional electrodes.

  The surface layers 3a and 3b have conductivity and have a function of electrically connecting the negative electrode active material sheet 10 of the present embodiment and a conductive core material described later. The surface layers 3a and 3b are also used to prevent the active material contained in the active material layer 2 from changing in volume due to charging / discharging and being pulverized and falling off.

  Each surface layer 3a, 3b is thinner than the thick film conductor for current collection used in the conventional electrode. Specifically, a thin layer of about 0.3 to 10 μm, particularly about 0.4 to 8 μm, particularly about 0.5 to 5 μm is preferable. As a result, the active material layer 2 can be continuously coated almost uniformly with the minimum necessary thickness. As a result, the pulverized active material can be prevented from falling off. The surface layers 3a and 3b in the above range are preferably formed by electrolytic plating as in the examples described later. The two surface layers 3a and 3b may have the same thickness or different thicknesses.

  Each surface layer 3a, 3b is comprised from the metal which can become a collector of a nonaqueous electrolyte secondary battery. Examples of such a metal include an element having a low ability to form a lithium compound. Examples of the element having a low ability to form a lithium compound include copper, nickel, iron, cobalt, and alloys of these metals. Of these metals, it is particularly preferable to use copper or nickel or an alloy thereof. In particular, it is preferable to use a nickel-tungsten alloy because the surface layers 3a and 3b can have high strength. The two surface layers 3a and 3b may have the same or different constituent materials. “Lithium compound forming ability is low” 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 active material layer 2 positioned between the surface layers 3a and 3b includes active material particles 2a. The active material layer 2 is formed, for example, by applying a conductive slurry containing active material particles 2a.

  Examples of the active material include silicon materials, tin materials, aluminum materials, germanium materials, and graphite. In particular, a silicon-based material that is a high-capacity material is preferable. Since the active material layer 2 is covered with the two surface layers 3a and 3b, the active material is effectively prevented from being pulverized and falling off due to charge / discharge. In addition, since the active material layer 2 has holes to be described later, the active material particles 2a can be in contact with the electrolytic solution, so that the electrode reaction is not hindered.

The active material particles 2a preferably have a maximum particle size of 30 μm or less, and 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 0.3 to 2 μm. When the maximum particle size is more than 30 μm, the particles are likely to fall off, and the life of the electrode may be shortened. There is no particular limitation on the lower limit of the particle size, and the smaller the better. In view of the method for producing the particles, the lower limit is about 0.01 μm. The particle size of the particles is measured by laser diffraction / scattering particle size distribution measurement or electron microscope observation.

  If the amount of the active material relative to the whole negative electrode active material sheet is too small, it is difficult to sufficiently improve the energy density of the battery. Conversely, if the amount is too large, the active material tends to fall off. Considering these, the amount of the active material is preferably 5 to 80% by weight, more preferably 10 to 50% by weight, and still more preferably 20 to 50% by weight with respect to the negative electrode active material sheet.

  The thickness of the active material layer 2 can be appropriately adjusted according to the ratio of the amount of the active material to the whole negative electrode and the particle size of the active material, and is not particularly critical in the present embodiment. Generally, the thickness is about 1 to 100 μm, particularly about 3 to 60 μm. The active material layer is preferably formed by applying a conductive slurry containing active material particles, as in the examples described later.

  In the active material layer 2, as shown in FIG. 1, a metal material 4 having a low lithium compound forming ability penetrates between particles contained in the layer. The metal material 4 is deposited between the particles by electrolytic plating. It is preferable that the metal material 4 penetrates over the entire thickness direction of the active material layer 2. The active material particles 2a are preferably present in the permeated material. That is, it is preferable that the active material particles 2a are not substantially exposed on the surface of the negative electrode active material sheet 10 and are embedded in the surface layers 3a and 3b. Thereby, the adhesiveness between the active material layer 2 and the surface layers 3a and 3b becomes strong, and the active material is further prevented from falling off. In addition, since electronic conductivity is ensured between the surface layers 3a and 3b and the active material through the material 4 that has penetrated into the active material layer 2, an electrically isolated active material can be generated, particularly the active material layer. The generation of an electrically isolated active material in the deep part of 2 is effectively prevented, and the current collecting function is maintained. As a result, functional degradation as a negative electrode is suppressed. In addition, the life can be extended. 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 metal material 4 having a low ability to form a lithium compound penetrating into the active material layer 2 has conductivity, and examples thereof include metal materials such as copper, nickel, iron, cobalt, and alloys of these metals. Is mentioned. The material may be the same type of material as that constituting the surface layers 3a and 3b, or may be a different type of material.

  It is preferable that the metal material 4 having a low ability of forming a lithium compound penetrating into the active material layer 2 penetrates the active material layer 2 in the thickness direction. Thereby, the two surface layers 3a and 3b are electrically connected through the metal material 4, and the electron conductivity of the negative electrode active material sheet 10 as a whole is further increased. The permeation of the metal material 4 having a low lithium compound forming ability throughout the thickness direction of the active material layer 2 can be confirmed by electron microscope mapping using the material as a measurement target. A metal material 4 having a low lithium compound forming ability penetrates into the active material layer 2 by electrolytic plating.

  The space between the active material particles 2a in the active material layer 2 is preferably not completely filled with the metal material 4 having a low lithium compound forming ability, but preferably has voids between the particles. Due to the presence of the voids, the volume change of the active material particles 2a due to charging / discharging is alleviated. From this viewpoint, the proportion of voids in the active material layer 2 is preferably about 0.1 to 30% by volume, particularly about 0.5 to 5% by volume. The void ratio can be determined by electron microscope mapping. Since the active material layer 2 is formed by applying and drying a conductive slurry containing the active material particles 2 a, voids are naturally formed in the active material layer 2. Accordingly, in order to set the void ratio within the above range, for example, the particle diameter of the active material particles 2a, the composition of the conductive slurry, and the application conditions of the slurry may be appropriately selected. In addition, after the slurry is applied and dried to form the active material layer 2, the proportion of voids may be adjusted by pressing under appropriate conditions.

  The active material layer may contain a conductive carbon material in addition to the active material particles 2a. This further imparts electronic conductivity to the negative electrode active material sheet 10. For example, when an active material layer is formed using the conductive slurry described above, the conductive carbon material is preferably 0.1 to 20 wt%, more preferably 1 to 10 wt% in the slurry. By blending, sufficient electron conductivity can be imparted. For example, particles such as acetylene black and graphite are used as the conductive carbon material. The particle diameter of these particles is preferably 40 μm or less, and particularly preferably 20 μm or less from the viewpoint of further imparting electron conductivity. The lower limit of the particle size of the particles is not particularly limited and is preferably as small as possible. In view of the method for producing the particles, the lower limit is about 0.01 μm.

  As shown in FIG. 1, the negative electrode active material sheet 10 has a large number of holes 5 that are open on each surface and extend in the thickness direction of the active material layer 2 and the surface layers 3 a and 3 b. The holes 5 penetrate through the negative electrode active material sheet 10 in the thickness direction. In the active material layer 2, the active material layer 2 is exposed on the wall surface of the hole 5. The role of the hole 5 is roughly divided into the following two.

  One is the role of supplying the electrolytic solution into the active material layer through the active material layer 2 exposed on the wall surface of the hole 5. In this case, the active material layer 2 is exposed on the wall surface of the hole 5, but the metal material 4 permeates between the active material particles 2a in the active material layer, so that the particles 2a are prevented from falling off. Has been.

  The other is the role of relaxing the volume change when the volume of the active material particles 2a in the active material layer changes due to charge / discharge. The volume change occurs mainly in the planar direction of the negative electrode active material sheet 10. Therefore, even if the volume of the active material particles 2a is increased by charging, the increased amount is absorbed by the holes 5 which are spaces. As a result, significant deformation of the negative electrode active material sheet 10 is effectively prevented.

  The opening ratio of the holes 5 opened on the surface of the negative electrode active material sheet 10, that is, the total area of the holes 5, was divided by the apparent area of the surface of the negative electrode active material sheet 10 and multiplied by 100. The value is preferably 0.3 to 30%, more preferably 2 to 15%, in order to effectively supply the electrolytic solution into the active material layer and to change the volume of the active material particles 2a effectively. It is effective from the viewpoint of mitigating. In the present embodiment, the hole 5 is open on both the first surface 1a and the second surface 1b of the negative electrode active material sheet 10, and substantially the same position on the surfaces 1a and 1b. Since the holes are sized, the opening ratio of the surface 1a and the opening ratio of the surface 1b are substantially the same. However, the aperture ratios on each surface do not need to be the same. If the aperture ratio on at least one surface is within the above range, the intended purpose is achieved.

  In addition to setting the opening ratio of the holes 5 in the above range, the diameter of the holes 5 opened on the surface of the negative electrode active material sheet 10 is preferably 5 to 500 μm, more preferably 20 to 100 μm. It is effective from the viewpoint of sufficiently supplying the electrolytic solution into the active material layer and from the viewpoint of effectively mitigating the volume change of the active material particles 2a. As described above, in the present embodiment, the diameter of the hole 5 opened in the first surface 1a of the negative electrode active material sheet 10 and the hole 5 opened in the second surface 1b. The diameter is the same, but they may be different. Further, the diameters of the holes 5 opened in the first surface 1a are the same, but the holes 5 having different diameters may be formed as long as the diameters in the above range are satisfied. Furthermore, in a range that does not impair the effects of the present invention, a small number of holes having a diameter outside the above range may be formed. The same applies to the second surface 1b.

  The pitch of the holes 5 is also important, although it is related to the aforementioned open area ratio and diameter. By setting the pitch to preferably 20 to 600 μm, the electrolytic solution can be sufficiently supplied into the active material layer, and the volume change of the active material particles 2a can be effectively mitigated. The pitch is defined by the length connecting the centers of the adjacent holes 5. If the arrangement of the holes 5 is random, the average value is used as the pitch value. In the present embodiment, the pitch on the first surface 1a of the negative electrode active material sheet 10 and the pitch on the second surface 1b are substantially the same. However, the pitch on each surface does not need to be the same. If the pitch on at least one surface is within the aforementioned range, the intended purpose is achieved.

  It is preferable that the holes 5 are uniformly distributed on both the first surface 1 a and the second surface 1 b of the negative electrode active material sheet 10. From this point of view, when paying attention to an arbitrary part on the surface of the negative electrode active material sheet 10, an average of 100 to 250,000, particularly 1000 to 40000, particularly 5000 to 20000, in a 1 cm × 1 cm square observation visual field. The holes 5 are preferably open.

  In the negative electrode active material sheet 10, the holes 5 penetrate in the thickness direction of the negative electrode active material sheet 10. However, in view of the role of the holes 5 to sufficiently supply the electrolytic solution into the active material layer and relieve the volume change of the active material particles 2 a, the holes 5 extend in the thickness direction of the negative electrode active material sheet 10. It is not necessary to penetrate, and it is sufficient that the hole is formed in the surface of the negative electrode active material sheet 10 and extends in the thickness direction at least in the active material layer 2. When the hole 5 is opened only on one surface of the negative electrode active material sheet 10, it faces the separator among the two surfaces of the negative electrode active material sheet 10 from the viewpoint of ensuring the flow of the electrolytic solution. It is preferable that the hole 5 is opened in the surface to be performed.

  The hole 5 can be formed by, for example, laser processing. Alternatively, drilling can be performed mechanically with a needle or punch. Further, the perforation can be performed by sandblasting. Moreover, the surface layer 3a, 3b may be formed on the surface of the active material layer containing the particles of the active material by electrolytic plating to form a hole (a fine void) extending in the thickness direction of the negative electrode active material sheet 10. It is possible (see FIG. 8 in Example 1 described later). However, from the viewpoint of accurately controlling the diameter and pitch of the holes, it is preferable to use laser machining, mechanical drilling, sandblasting, or the like.

  One embodiment of the production method of the present invention using the negative electrode active material sheet 10 having the above-described configuration is shown in FIG. As shown in FIG. 2, first, the members constituting the battery are overlapped. The constituent members used here are the first separator S1, the second separator S2, the positive electrode C, the first negative electrode active material sheet A1, the second negative electrode active material sheet A2, and the conductive core material F. is there. All of these members have a long strip shape. These members are all the same width. The first separator S1 and the second separator S2 may be the same or different. Similarly, the first negative electrode active material sheet A1 and the second negative electrode active material sheet A2 may be the same or different. A tab T <b> 1 extending in a direction orthogonal to the longitudinal direction of the core material F is attached to one side edge portion of the conductive core material F in the longitudinal direction. Similarly, a tab T <b> 2 extending in a direction orthogonal to the longitudinal direction of the positive electrode C is attached to one side edge of the positive electrode C in the longitudinal direction. The tabs T1 and T2 are used as output terminals for extracting current, respectively. The tabs T1 and T2 are respectively attached to the positive electrode C and the core material F by a method such as ultrasonic welding, laser welding, solder connection, resistance welding, or the like.

  As shown in FIG. 2, these members include a positive electrode C, a first separator S1, a first negative electrode active material sheet A1, a conductive core material F, and a second negative electrode active material sheet A2 stacked in this order. Is done. Furthermore, the second separator S2 is disposed outside the second negative electrode active material sheet A2. In superimposing these members, as shown in FIG. 2, the position of one end of each member is sequentially shifted. When these members are integrally wound in the winding step described later, a difference in winding diameter occurs between the member positioned on the inner side and the member positioned on the outer side, and the difference is absorbed. Therefore, the position of the one end part of each member which is a position of the winding start is shifted.

  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. As shown in FIG. 3, the winding is performed so that the second separator S2 side faces inward. By winding in this way, in the wound body, the second separator S2, the second negative electrode active material sheet A2, the conductive core material F, the first negative electrode active material sheet A1, the first The separator S1 and the positive electrode C are arranged in layers in this order.

  As shown in FIG. 4, pressure is applied to the wound body obtained in this way from the direction orthogonal to the axis. By this applied pressure, the cylindrical wound body is deformed into a flat body FB. In this deformation process, each member constituting the wound body is plastically deformed. The portions with the greatest degree of deformation are the left and right side portions S, S in the flat body FB. Therefore, a large stress is applied to the side portion S during deformation. As a result, each member located on the side portion S is likely to tear. In particular, when the number of windings is increased for the purpose of increasing the capacity of the battery, the difference in elongation due to the difference in the winding diameter of each member becomes remarkable, and tearing is more likely to occur. When tearing occurs, the portion located farther from the tearing position when viewed from the tabs T1 and T2 does not contribute to the electrode reaction, so that the capacity is significantly reduced. In this case, the active material sheets A1 and A2 for the negative electrode, which are thin and have a metal material deposited in the active material layer and have high rigidity, are integrally formed on the thick film conductor. Further, tearing is likely to occur due to differences in elongation and thickness between the negative electrode active material sheets A1 and A2 and the thick film conductor. However, in the present embodiment, the negative electrode active material sheets A1 and A2 are not formed in close contact with the thick film conductor, but are superimposed on the conductive core material F that is a member corresponding to the thick film conductor. Therefore, the negative electrode active material sheets A1 and A2 and the conductive core material F can be extended independently and the negative electrode active material sheets A1 and A2 are effectively prevented from being broken. Even if tearing occurs, the portion located on the far side from the tearing position when viewed from the tabs T1 and T2 is maintained in electrical contact by the conductive core material F, so that the portion is also subjected to electrode reaction. Can contribute.

  As described above, according to the manufacturing method of the present embodiment, it is possible to effectively prevent the active material sheets A1 and A2 for the negative electrode from being ruptured during the winding operation of each member during battery production. The flat body FB thus obtained is placed in a predetermined container. The container is filled with a non-aqueous electrolyte, and then the container is sealed to obtain a target secondary battery having a square package.

  The members used in the production method will be described. Details of the negative electrode active material sheets A1 and A2 are as described above, and the conductive core material disposed between the negative electrode active material sheets A1 and A2. As F, it is preferable to use a thin and high-strength conductive material from the viewpoint of preventing the occurrence of tearing and improving the energy density. Furthermore, the conductive core material F is preferably made of a material having a low ability to form a lithium compound. From these viewpoints, as the conductive core material F, a high-strength copper foil, a foil made of Ni-W which is a material having high toughness, a stainless steel foil, or the like can be used. As the high-strength copper foil, a rolled copper foil, a rolled copper alloy foil, or the like can be used. It is also preferable to use an electrolytic copper foil having high elongation characteristics such as HTE foil (trade name of Mitsui Mining & Smelting Co., Ltd.). Although depending on the type of the conductive core material F, the thickness is preferably 1 to 40 μm, particularly preferably 3 to 12 μm. The conductive core material F may be formed with holes having the same or different diameter and / or pitch as the holes 5 formed in the negative electrode active material sheet 10 described above.

  In particular, as the conductive core F, it is preferable to use a conductive lithium foil having a metal lithium layer formed on at least one surface thereof. When such a conductive core material F is used, in the battery obtained, a metal lithium layer is disposed between the negative electrode active material sheets A1 and A2 and the conductive foil. With such a configuration, the metal lithium layer forms a local battery with the negative electrode active material in the presence of the non-aqueous electrolyte. Thereby, metallic lithium chemically reacts with an active material located in the vicinity of the metallic lithium layer to form a lithiated product. Alternatively, lithium reacts with the active material due to a lithium concentration gradient to form a lithiated product. That is, the metal lithium layer functions as a lithium supply source. As a result, even if lithium is consumed due to a reaction with the electrolyte during charge / discharge cycles or long-term storage, the lithium depletion problem is solved because lithium is supplied from the lithiated product. Thereby, the life of the battery is extended. The metal lithium layer is not exposed on the surface of the negative electrode active material sheet and is located inside the negative electrode active material sheet, and the lithium reacts with the active material to form a lithiated material. There is little risk of lithium dendrites that can cause short circuits or fire.

  It should be noted that a battery having a metallic lithium layer undergoes a reaction between metallic lithium and the negative electrode active material without being charged. The reaction between metallic lithium and the negative electrode active material occurs before charging, so that the negative electrode active material has already increased in volume before charging. Therefore, even if it charges / discharges after that, the expansion coefficient of the active material sheet for negative electrodes resulting from charging / discharging is very small. As a result, the battery obtained according to the present embodiment has a very advantageous effect that deformation due to the volume change of the negative electrode active material due to charge / discharge is extremely difficult to occur.

  The amount of metallic lithium is preferably 0.1 to 70%, particularly 5 to 30%, based on the saturation reversible capacity of the negative electrode active material, because the capacity recovery characteristics are good.

For the same purpose as described above, it is also possible to dispose a metal lithium foil between the first negative electrode active material sheet A1 and the first separator S1. However, in that case, in order to prevent generation of lithium dendrite due to charge / discharge at the interface between the first negative electrode active material sheet A1 and the first separator S1, a metal is used before using the battery. It is necessary to incorporate lithium into the negative electrode active material layer. For this purpose, the amount of metallic lithium and aging conditions may be adjusted as appropriate. Instead of or in addition to arranging the metal lithium foil between the first negative electrode active material sheet A1 and the first separator S1, the metal lithium foil is placed outside the second negative electrode active material sheet A2. Can also be arranged.

  As the positive electrode C, a positive electrode material mixture obtained by applying a positive electrode mixture on each surface of a thick film conductive material and then rolling and pressing it can be used. The positive electrode mixture is obtained by suspending a positive electrode active material and, if necessary, a conductive agent and a binder in an appropriate solvent. As the positive electrode active material, conventionally known positive electrode active materials such as lithium nickel composite oxide, lithium manganese composite oxide, and lithium cobalt composite oxide are used.

As the separator, a synthetic resin nonwoven fabric, polyethylene, polypropylene porous film or the like is preferably used. The nonaqueous electrolytic solution is a solution in which a lithium salt as a supporting electrolyte is dissolved in an organic solvent. The lithium salt, for _{example, LiC1O 4, LiA1Cl 4, LiBF} 4, LiPF 6, LiAsF 6, LiSbF 6, LiSCN, LiC1, LiBr, LiI, etc. _{LiCF 3 SO 3, LiC 4 F} 9 SO 3 are exemplified.

  The battery manufactured according to the above method has the second negative electrode active material sheet A2, the conductive core material F, the first negative electrode active material sheet A1, the first separator S1, and the positive electrode C. A stack in which the second separator S2 is placed on the outer side of the second negative electrode active material sheet A2 is wound in such a manner that the second separator S2 is on the inner side. It has a round body. As described above, these members are in contact with each other only by overlapping. Therefore, the first negative electrode active material sheet A1 and the second negative electrode active material sheet A2 are electrically in contact with the conductive core material F so as to be mechanically peelable. With such a configuration, even if the negative electrode active material changes in volume due to charge / discharge and the negative electrode active material sheets A1 and A2 are deformed, the conductive core material F is affected by the deformation. It becomes difficult to receive. For example, generation of wrinkles of the conductive core material F and tearing of the conductive core material F are less likely to occur. As a result, the current collecting property by the conductive core material F is ensured, and the life of the battery is extended.

  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 negative electrode active material sheets A1 and A2 in the above embodiment, the surface layers 3a and 3b are formed on each surface of the active material layer 2, but one or both of these surface layers may not be formed. When a surface layer is formed only on one surface of the active material layer 2, it is preferable that the negative electrode active material sheet and the separator are overlapped so that the surface layer faces the separator. Further, although the metal material has permeated into the active material layer 2, an active material layer in a state in which the metal material does not penetrate may be used.

  Further, as the negative electrode active material sheet, in addition to the form shown in FIG. 1, a foil made of a material having a high ability to form a lithium compound (for example, tin foil, tin alloy foil, aluminum foil, aluminum alloy foil, etc.), For example, a thin layer made of a material having a low lithium compound forming ability may be used on one surface of the foil.

  The active material layer and the surface layer may be formed by a sputtering method, a vacuum deposition method, or a plating method.

In the embodiment, the second separator S2 is disposed outside the second negative electrode active material sheet A2 and wound so that the second separator S2 is inside. Alternatively, the second separator S2 may be disposed outside the positive electrode C, and winding may be performed so that the second separator S2 is on the inner side. Also in that case, it is possible to arrange a metal lithium foil between the first negative electrode active material sheet A1 and the first separator S1. Further, instead of or in addition to arranging a metal lithium foil between the first negative electrode active material sheet A1 and the first separator S1, a metal lithium foil is arranged outside the second separator S2. You can also

  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]
The negative electrode active material sheet 10 shown in FIG. 1 was manufactured according to the method shown in FIGS. First, as shown in FIG. 5A, the copper carrier foil 11 (thickness: 35 μm) obtained by electrolysis was acid-washed at room temperature for 30 seconds. Subsequently, it was washed with pure water at room temperature for 30 seconds. Next, the carrier foil 11 was immersed in a 3.5 g / l CBTA (carboxybenzotriazole) solution kept at 40 ° C. for 30 seconds. As a result, a release layer 12 was formed as shown in FIG. After the release layer 12 was formed, it was lifted from the solution and washed with pure water for 15 seconds.

The carrier foil 11 was immersed in an H ₂ SO ₄ / CuSO ₄ plating bath for electrolytic plating. As a result, a surface layer 3b made of copper was formed on one surface of the carrier foil 11, as shown in FIG. The composition of the plating bath was 250 g / l for CuSO _{4 and} 70 g / l for H ₂ SO ₄ . The current density was 5 A / dm ² . The surface layer 3b was formed to a thickness of 5 μm. After lifting from the plating bath, it was washed with pure water for 30 seconds and dried in the air.

Next, as shown in FIG. 5 (d), the active material layer 2 was formed by applying a slurry containing negative electrode active material particles on the surface layer 3 b to a thickness of 15 μm. The active material particles were made of Si, and the average particle size was D ₅₀ = 2 μm. The composition of the slurry was active material: acetylene black: styrene butadiene rubber = 98: 2: 1.7.

After the active material layer 2 was formed, the carrier foil 11 was immersed in a Watt bath having the following bath composition, and nickel was applied to the active material layer 2 by electrolysis. The current density was 5 A / dm ² , the bath temperature was 50 ° C., and the pH was 5. A nickel electrode was used as the anode. A DC power source was used as the power source. This infiltration plating was performed to such an extent that some active material particles were exposed from the plating surface. After lifting from the plating bath, it was washed with pure water for 30 seconds and dried in the air.
・ NiSO ₄・ 6H ₂ O 250g / l
・ NiCl ₂・ 6H ₂ O 45g / l
・ H ₃ BO ₃ 30g / l

Next, electrolytic plating was performed by immersing the carrier foil 11 in a Cu-based plating bath. The composition of the plating bath was 200 g / l for H ₃ PO _{4 and} 200 g / l for Cu ₃ (PO ₄ ) ₂ .3H ₂ O. The plating conditions were a current density of 5 A / dm ² and a bath temperature of 40 ° C. As a result, a surface layer 3a made of copper was formed on the active material layer 2 as shown in FIG. The surface layer 3a was formed to a thickness of 9 μm. After lifting from the plating bath, it was washed with pure water for 30 seconds and dried in the air.

Next, as shown in FIG. 5F, the surface layer 3a formed on the active material layer 2 was irradiated with a YAG laser to form the holes 5 regularly. The hole 5 was formed so as to penetrate both the surface layers 3a and 3b and the active material layer 2 positioned therebetween. The diameter of the holes 5 was 25 μm, and the pitch was 100 μm (10000 holes / cm ² ).

  Finally, as shown in FIG.5 (g), the carrier foil 11 and the surface layer 3b which contact | connects it were peeled, and the active material sheet 5 for negative electrodes was obtained. The cross section and surface electron micrographs of the obtained negative electrode active material sheet are shown in FIGS. 6 and 7, respectively. An enlarged image of the surface is shown in FIG. From these electron micrographs, it can be seen that a large number of through holes are regularly formed in the negative electrode active material sheet. It can also be seen that fine voids are formed in the surface layer.

Using the thus obtained negative electrode active material sheet, positive electrode, separator, and conductive core material, a square package lithium secondary battery was obtained according to the method shown in FIGS. As the positive electrode, an oxide containing Li, Mn, Co, and Ni was used on each surface of a 20 μm aluminum foil. As the separator, a microporous film obtained by uniaxially stretching a polyethylene film was used. As the conductive core material, 18 μm rolled copper foil was used. As the non-aqueous electrolyte, a mixed solution of LiPF ₆ / ethylene carbonate and dimethyl carbonate (1: 1 volume ratio) was used.

[Comparative Example 1]
In Example 1, as the carrier foil 11, the conductive core material (18 μm rolled copper foil) used in Example 1 was used. An active material sheet for a negative electrode was formed on one surface of this rolled copper foil by the method shown in FIGS. The operation shown in FIG. 5 (g) was not performed. In this way, a negative electrode was obtained in which the negative electrode active material sheet was integrally formed on one surface of the rolled copper foil. Using this negative electrode in place of the negative electrode active material sheet and conductive core in Example 1, a lithium secondary battery having a square package was obtained in the same manner as in Example 1. In the battery thus obtained, the negative electrode active material sheet constituting the negative electrode and the rolled copper foil are not in a state of being in contact with each other so as to be mechanically peelable.

[Evaluation]
The battery thus obtained was disassembled before being charged and discharged, and it was observed whether or not tearing occurred in the negative electrode active material sheet or the like. The results are shown in FIGS. FIG. 9 shows a state in which the battery obtained in Example 1 is disassembled, with the upper side showing the negative electrode active material sheet and the lower side showing the positive electrode. From this result, in the battery obtained in Example 1, it can be seen that no tearing occurred in the negative electrode active material sheet. On the other hand, FIG. 10 shows a state in which the battery obtained in Comparative Example 1 is disassembled, with the upper side being a negative electrode (in which a negative electrode active material sheet is integrally formed on a conductive core material) and the lower side being a negative electrode. The positive electrode is shown. From this result, it can be seen that in the battery obtained in Comparative Example 1, the negative electrode active material sheet was torn.

  Separately from the above observation, the obtained battery was charged and discharged 20 times. Thereafter, the battery was disassembled, and the surface state of the conductive core material was observed. In Example 1, since the negative electrode active material sheet and the conductive core material are in a peelable state, it is easy to expose the surface of the conductive core material. In Comparative Example 1, since the negative electrode active material sheet is integrally formed only on one surface of the conductive core material, the surface of the conductive core material from the side where the negative electrode active material sheet is not formed. The condition was observed. The results are shown in FIG. 11 and FIG. FIG. 11 shows the surface state of the conductive core material in the battery obtained in Example 1, and FIG. 12 shows the surface state of the conductive core material in the battery obtained in Comparative Example 1. In FIG. 11, generation | occurrence | production of a wrinkle or a tear is not observed in a conductive core material. On the other hand, in FIG. 12, many wrinkles are generated in the conductive core material.

  Furthermore, about the active material sheet for negative electrodes obtained in Example 1, this was laminated | stacked in order of the active material sheet for negative electrodes, the electroconductive core material, the active material sheet for negative electrodes, the separator, the positive electrode, and the separator. Then, a metal round bar having a diameter of 3.5 mm is placed on the separator in a direction perpendicular to the longitudinal direction, and whether or not tearing occurs when the whole of these stacked bodies is bent along the round bar. Was observed. The result is shown in FIG. The same observation was performed on the negative electrode active material sheet obtained in Comparative Example 1. The result is shown in FIG. As is clear from these results, the laminate including the negative electrode active material sheet obtained in Example 1 was not torn, whereas the negative electrode active material sheet obtained in Comparative Example 1 was obtained. It can be seen that the superposed body including ruptured.

It is a schematic diagram which shows one Embodiment of the active material sheet for negative electrodes used for this invention. It is a schematic diagram which shows one Embodiment of the manufacturing method of this invention. It is a schematic diagram which shows the stage in the middle of the manufacturing method of this invention. It is a schematic diagram which shows the state which pressurizes the wound body obtained by the manufacturing method of this invention, and obtains a flat body. It is a schematic diagram which shows the manufacturing method of the active material sheet for negative electrodes shown in FIG. 2 is an electron micrograph showing a cross section of a negative electrode active material sheet in the battery obtained in Example 1. FIG. 3 is an electron micrograph showing the surface of the negative electrode active material sheet in the battery obtained in Example 1. FIG. 2 is an electron micrograph showing an enlarged surface of a negative electrode active material sheet in the battery obtained in Example 1. FIG. 4 is a photograph showing a state in which the battery obtained in Example 1 is disassembled. 4 is a photograph showing a state in which a battery obtained in Comparative Example 1 is disassembled. It is a photograph which shows the state disassembled, after charging / discharging the battery obtained in Example 1 20 times. It is a photograph which shows the state disassembled, after charging / discharging the battery obtained by the comparative example 1 20 times. It is a photograph which shows a state when the active material sheet for negative electrodes obtained in Example 1 is bent along a round bar. It is a photograph which shows a state when the active material sheet for negative electrodes obtained by the comparative example 1 is bent along a round bar.

Explanation of symbols

1a, 1b Surface 2 Active material layer 3, 3a, 3b Surface layer 4 Metal material with low lithium compound forming ability 5 Hole 10, A1, A2 Negative electrode active material sheet C Positive electrode F Conductive core material S1, S2 Separator

Claims (10)

Each of which is in the shape of a long strip, the positive electrode, the first separator, the first negative electrode not having a thick film conductor having a thickness of 12 to 35 μm, the conductive core, and the thickness of 12 to 35 μm. The second negative electrode not having the thick film conductor is superposed in this order, and a second separator is arranged outside the positive electrode or outside the second negative electrode. These are wound so that it may become, The manufacturing method of the nonaqueous electrolyte secondary battery characterized by the above-mentioned.   2. The first and second negative electrodes each having an active material layer containing particles of a negative electrode active material, wherein a metal material precipitated by electrolytic plating penetrates between the particles is used in the active material layer. Manufacturing method. As the first and second negative electrodes, on at least one surface of the active material layer, a surface layer having a thickness of 0.3 to 10 μm made of a metal that can be a current collector of a non-aqueous electrolyte secondary battery is disposed. The manufacturing method of Claim 2 which uses what is.   The method according to claim 2 or 3, wherein the first and second negative electrodes have a large number of holes that are open on at least one surface and extend in the thickness direction of the active material layer.   The manufacturing method in any one of Claim 1 thru | or 4 using what a metal lithium layer was formed in at least one surface of electroconductive foil as an electroconductive core material.   The manufacturing method according to any one of claims 1 to 4, wherein a metal lithium foil is further disposed between the first negative electrode and the first separator. Disposing a second separator on the outside of the positive electrode, further a manufacturing method of claim 6, further arranging the metal lithium foil outside side of the second separator. Second disposing a separator, further manufacturing process according to claim 6, further arranging the metal lithium foil outside side of the second negative electrode on the outside of the second negative electrode.   The manufacturing method according to any one of claims 1 to 8, wherein a wound body obtained by winding is pressed from a direction orthogonal to the axis thereof to form a flat body. Each of which is in the shape of a long strip, the positive electrode, the first separator, the first negative electrode not having a thick film conductor having a thickness of 12 to 35 μm, the conductive core, and the thickness of 12 to 35 μm. The second negative electrode not having the thick film conductor is superposed in this order, and the superposed body in which the second separator is disposed outside the positive electrode or outside the second negative electrode is the second negative electrode. A lithium secondary battery including a wound body that is wound so that the separator is inside,
A non-aqueous electrolyte secondary battery, wherein the first and second negative electrodes and the conductive core member are in electrical contact so as to be peelable.