JP2012155886A - Lithium ion secondary battery and battery pack equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery which can suppress accumulation of gas between electrodes.SOLUTION: A lithium ion battery 10 comprises a laminate battery 1, and plate members 2, 3. The laminate battery 1 is placed so that the thickness direction DR2 is parallel with the installation surface PP of the laminate battery 1. Each of the plate members 2, 3 has an area larger than that of a sheet-like negative electrode 12 which has an area larger than that of a sheet-like positive electrode 11. The plate member 2 is in contact with one side surface of the laminate battery 1 facing the sheet-like positive electrode 11 and the sheet-like negative electrode 12, and the plate member 3 is in contact with the other side surface of the laminate battery 1 facing the sheet-like positive electrode 11 and the sheet-like negative electrode 12. The plate members 2, 3 press the laminate battery 1 in the thickness direction.

Description

  The present invention relates to a lithium ion secondary battery and a battery pack including the same.

  2. Description of the Related Art Conventionally, an electronic device including a square or laminate type lithium ion battery pressed in the thickness direction is known (Patent Document 1).

  In this electronic apparatus, the pressing area for pressing the lithium ion battery is smaller than the area of the side surface of the lithium ion battery, and is 95% or less, preferably 80% or less, more preferably 50% or less of the area of the side surface of the lithium ion battery. It is. Moreover, the center when pushing a lithium ion battery is a center part of a lithium ion battery.

  Also known is a battery pack having a structure in which laminated batteries are stacked in the vertical direction, a deformation preventing plate is sandwiched between the laminated batteries, and the laminated battery is pressed by a pressing plate from the vertical direction (patent) Reference 2).

  In this battery pack, the area of the deformation prevention plate is equal to or larger than the area of the separator, and the holding plate is larger than the laminated battery and the deformation prevention plate.

JP 2006-156612 A International Publication No. WO2007 / 043392 Pamphlet

  However, in the electronic device disclosed in Patent Document 1, the portion of the lithium ion battery that is not pressed is disposed over the entire peripheral edge of the side surface of the lithium ion battery, and thus the portion that is not pressed (the portion where the generated gas accumulates) There is a problem in that the electrolytic solution comes out and closes in the lower part, and a part of the gas accumulates between the electrodes.

  Further, in the battery pack disclosed in Patent Document 2, since the pressing plate presses the entire side surface of each laminated battery, the portion that is not pressed spreads over the entire edge of the side surface of the laminated battery, and the generated gas escape space Disappears. As a result, there is a problem that gas accumulates between the electrodes.

  Therefore, the present invention has been made to solve such a problem, and an object of the present invention is to provide a lithium ion secondary battery capable of suppressing the accumulation of gas between electrodes.

  Another object of the present invention is to provide a battery pack including a lithium ion secondary battery capable of suppressing gas from accumulating between electrodes.

  According to the embodiment of the present invention, the lithium ion secondary battery includes a laminated battery and a pressing member. A laminated battery has a structure in which power generation elements are laminated by a laminate member. The pressing member has a flat plate shape, and presses the laminated battery in the thickness direction of the laminated battery. The laminated battery is arranged so that the thickness direction of the laminated battery is parallel to the installation surface of the laminated battery. The pressing member has a larger area than the larger electrode of the positive electrode and the negative electrode included in the power generation element, and presses the side surface of the laminated battery facing the positive electrode and the negative electrode. Furthermore, the 1st area | region which is not pressed by the pressing member among the laminate-type batteries is arrange | positioned above the 2nd area | region pressed by the pressing member.

  Further, according to the embodiment of the present invention, the battery pack includes a plurality of laminated batteries and a plurality of flat plate members. The plurality of flat plate members are arranged between two adjacent laminated batteries and on both ends of the plurality of laminated batteries, and push the plurality of laminated batteries in the thickness direction of the laminated battery. Each of the plurality of laminated batteries is disposed so that the thickness direction of the laminated batteries is parallel to the installation surface of the plurality of laminated batteries. The plurality of laminated batteries and the plurality of flat plate members are alternately arranged along the installation surface. Each of the plurality of flat plate members has a larger area than the larger electrode of the positive electrode and the negative electrode of the laminated battery, and presses the side surface of the laminated battery facing the positive electrode and the negative electrode. In each of the plurality of laminated batteries, the first region that is not pressed by the flat plate member is disposed above the second region that is pressed by the flat plate member.

  In the lithium ion secondary battery according to the embodiment of the present invention, in the laminated battery, the first region that is not pressed by the pressing member is arranged above the second region that is pressed by the pressing member. As a result, the space in the first region is not blocked by the electrolytic solution, and the gas generated in the laminated battery accumulates in the space in the first region.

  Therefore, accumulation of gas between the electrodes can be suppressed.

  The battery pack according to the embodiment of the present invention includes a plurality of the laminated batteries described above, and flat plate members are disposed between the laminated batteries and at both ends of the laminated batteries. In each laminated battery, the first region that is not pressed by the flat plate member is disposed above the second region that is pressed by the flat plate member. As a result, the space in the first region is not blocked by the electrolytic solution, and the gas generated in each laminated battery accumulates in the space in the first region.

  Therefore, in each laminate type battery constituting the battery pack, it is possible to suppress the accumulation of gas between the electrodes.

FIG. 1 is a cross-sectional view showing a configuration of a lithium ion secondary battery according to an embodiment of the present invention. FIG. 2 is a plan view of the laminated battery shown in FIG. FIG. 3 is a diagram for explaining a method of applying pressure to the laminated battery using a flat plate member. FIG. 4 is a diagram for explaining another method of applying pressure to the laminated battery by the flat plate member. FIG. 5 is a process diagram showing a method of manufacturing the lithium ion secondary battery shown in FIG. FIG. 6 is a perspective view of the battery pack according to the embodiment of the present invention. FIG. 7 is a process diagram showing a method of manufacturing the battery pack shown in FIG.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a cross-sectional view showing a configuration of a lithium ion secondary battery according to an embodiment of the present invention. FIG. 2 is a plan view of the laminated battery 1 shown in FIG. 1 and 2, a lithium ion secondary battery 10 according to an embodiment of the present invention includes a laminated battery 1 and flat plate members 2 and 3.

  Laminated battery 1 includes sheet-like positive electrode 11, sheet-like negative electrode 12, separator 13, laminate film 14, positive electrode tab 15, and negative electrode tab 16.

  The sheet-like positive electrode 11, the sheet-like negative electrode 12, and the separator 13 are stacked in the thickness direction DR <b> 2 perpendicular to the in-plane direction DR <b> 1 of the laminate-type battery 1 to constitute the power generation element 30. The sheet-like positive electrode 11 has a size smaller than that of the sheet-like negative electrode 12 in the in-plane direction DR1 of the laminated battery 1. The sheet-like negative electrode 12 has a size smaller than that of the separator 13 in the in-plane direction DR1.

  In the in-plane direction DR1, the sheet-like positive electrode 11, the sheet-like negative electrode 12, and the separator 13 have both ends of the separator 13 positioned outside both ends of the sheet-like negative electrode 12, and both ends of the sheet-like negative electrode 12 are sheet-like positive electrodes. 11 is arranged so as to be located on the outer side than both ends.

  The sheet-like positive electrode 11 may not be smaller than the sheet-like negative electrode 12.

  The laminate film 14 has a substantially rectangular planar shape and houses the power generation element 30. And the edge part of the laminate film 14 is sealed. That is, the laminated battery 1 has a sealing portion 14A at the peripheral edge.

  The positive electrode tab 15 has a flat shape, and one end thereof is connected to the sheet-like positive electrode 11 directly or via a lead body 17. The other end of the positive electrode tab 15 is pulled out via the laminate film 14.

  The negative electrode tab 16 has a flat plate shape, and one end thereof is connected to the sheet-like negative electrode 12 directly or via a lead body (not shown). The other end of the negative electrode tab 16 is pulled out through the laminate film 14.

  The sheet-like positive electrode 11 has, for example, a structure in which a layer (positive electrode mixture layer) made of a positive electrode mixture containing a positive electrode active material, a conductive additive, a binder, and the like is formed on one side or both sides of a current collector.

A positive electrode active material consists of an active material which can occlude / release lithium ion, for example. Such a positive electrode active material is, for example, a lithium-containing transition metal having a layered structure represented by Li _{1 + x} MO ₂ (−0.1 <x <0.1, M: Co, Ni, Mn, Al, Mg, etc.) Oxides, LiMn ₂ O ₄ , lithium manganese oxide having a spinel structure in which some of the elements are replaced with other elements, and olivine type compounds represented by LiMPO ₄ (M: Co, Ni, Mn, Fe, etc.) Consisting of either.

The lithium-containing transition metal oxide having a layered structure is, for example, LiCoO ₂ , LiNi _1-x Co _xy Al _y O ₂ (0.1 ≦ x ≦ 0.3, 0.01 ≦ y ≦ 0.2 And an oxide containing at least Co, Ni and Mn (LiMn _1/3 Ni _1/3 Co _1/3 O ₂ , LiMn _5/12 Ni _5/12 Co _1/6 O ₂ , LiNi _3/5 Mn _{1 / 5} Co _1/5 O ₂ ).

  The current collector of the positive electrode is made of, for example, an aluminum foil or an aluminum alloy foil. The thickness of the current collector varies depending on the size and capacity of the battery, but is, for example, 0.01 to 0.02 mm.

  The sheet-like positive electrode 11 is produced by the following method. A positive electrode mixture containing a positive electrode active material, a conductive additive such as graphite, acetylene black, carbon black, and fibrous carbon, and a binder such as polyvinylidene fluoride (PVDF) is mixed with N-methyl-2-pyrrolidone (NMP). ) Or the like to prepare a paste-like or slurry-like composition uniformly dispersed (the binder may be dissolved in the solvent). And this composition is apply | coated on a positive electrode electrical power collector, it dries, and the thickness of a positive mix layer is adjusted by press processing as needed. Thereby, the sheet-like positive electrode 11 is produced.

  In the embodiment of the present invention, the sheet-like positive electrode 11 may be produced using a method other than the method described above.

  The thickness of the positive electrode mixture layer in the sheet-like positive electrode 11 is preferably 10 to 100 μm per side. Moreover, it is preferable that content of each structural component in a positive mix layer shall be positive electrode active material: 80-98 weight%, conductive support agent: 1-10 weight%, and binder: 1-10 weight%.

  The positive electrode tab 15 is preferably made of aluminum or an aluminum alloy from the viewpoint of ease of connection with the equipment used.

  And it is preferable that the thickness of the positive electrode tab 15 shall be 50-300 micrometers. That is, by setting the thickness of the positive electrode tab 15 to 50 μm or more, it is possible to prevent the positive electrode tab 15 from being cut during welding of the positive electrode tab 15 and to prevent the positive electrode tab 15 from being broken by pulling and bending. it can. Moreover, by setting the thickness of the positive electrode tab 15 to 300 μm or less, it is possible to prevent a gap in the thickness direction from being generated in the heat seal portion of the laminate film 14.

  In addition, in order to increase the adhesive strength between the laminate film 14 and the positive electrode tab 15, a resin adhesive layer (for example, the laminate film 4) is previously placed on the positive electrode tab 15 where it is planned to be positioned at the heat seal portion. You may provide the contact bonding layer comprised by resin of the same kind as resin which comprises the heat sealing resin layer which the metal laminate film to comprise has.

  Examples of the method of connecting the current collector in the sheet-like positive electrode 11 or the aluminum lead body 17 connected to the current collector and the positive electrode tab 15 include resistance welding, ultrasonic welding, laser welding, caulking, and conductivity. Various methods such as a method using an adhesive can be employed. Of these, ultrasonic welding is particularly suitable.

  The sheet-like negative electrode 12 is made of, for example, an active material that can occlude / release lithium ions. Such negative electrode active materials occlude and release lithium ions such as graphite, pyrolytic carbons, cokes, glassy carbons, fired organic polymer compounds, mesocarbon microbeads (MCMB), and carbon fibers. It consists of one or a mixture of two or more possible carbon-based materials.

Other negative electrode active materials include, for example, elements such as Si, Sn, Ge, Bi, Sb, and In, alloys of Si, Sn, Ge, Bi, Sb, and In, lithium-containing nitrides, and lithium oxides. It consists of a compound (Li ₄ Ti ₅ O ₁₂ or the like) that can be charged and discharged at a low voltage close to lithium metal, lithium metal, and a lithium / aluminum alloy.

  These negative electrode active materials include a conductive additive (made of the same material as the positive electrode conductive additive), a binder (a binder of PVDF, rubber binder such as styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC), etc. ) Is added as appropriate to the negative electrode mixture, and the current collector is a finished product (negative electrode mixture layer) using the current collector as a core material, or the above-described various alloys or lithium metal foils. Those laminated on the surface of the sheet are used as the sheet-like negative electrode 12.

  And the sheet-like negative electrode 12 is produced by the following method. A paste in which a negative electrode mixture containing the above-described negative electrode active material, a binder, and, if necessary, a conductive additive such as graphite, acetylene black, and carbon black is uniformly dispersed using a solvent such as NMP. Alternatively, a slurry-like composition is prepared (the binder may be dissolved in a solvent). And this composition is apply | coated on a negative electrode electrical power collector, it dries, and the thickness or density of a negative mix layer is adjusted by press processing as needed. Thereby, the sheet-like negative electrode 12 is produced.

  In the embodiment of the present invention, the sheet-like negative electrode 12 may be produced using a method other than the method described above.

  As the negative electrode current collector, aluminum or copper is suitable. The thickness of the current collector depends on the size or capacity of the battery, but is preferably 5 μm to 20 μm, for example.

  The thickness of the negative electrode mixture layer in the sheet-like negative electrode 12 is preferably 10 to 100 μm per side. Moreover, it is preferable that content of each structural component in a negative mix layer is 80-98 weight% of negative electrode active materials, and 1-10 weight% of binders. Moreover, when using a conductive support agent for a negative electrode, it is preferable that content of the conductive support agent in a negative mix layer is 1-10 weight%.

  The negative electrode tab 16 is made of a metal foil or ribbon such as aluminum, aluminum alloy, nickel, nickel-plated copper, and nickel-copper clad. Further, the thickness of the negative electrode tab 16 is preferably 50 to 300 μm, similarly to the positive electrode tab 15.

  That is, by setting the thickness of the negative electrode tab 16 to 50 μm or more, it is possible to prevent the negative electrode tab 16 from being cut during welding of the negative electrode tab 16 and to prevent the negative electrode tab 16 from being torn by pulling and bending. it can. In addition, by setting the thickness of the negative electrode tab 16 to 300 μm or less, it is possible to prevent a gap in the thickness direction from being generated in the heat seal portion of the laminate film 14.

  In addition, in order to increase the adhesive strength between the laminate film 14 and the negative electrode tab 16, a resin adhesive layer (for example, the laminate film 14 is preliminarily disposed on a location where the negative electrode tab 16 is supposed to be located at the heat seal portion. You may provide the contact bonding layer comprised by resin of the same kind as resin which comprises the heat sealing resin layer which the metal laminate film to comprise has.

  The sheet-like negative electrode 12 and the negative electrode tab 16 may be connected by directly connecting the current collector of the sheet-like negative electrode 12 and the negative electrode tab 16, for example, via a copper lead body. May be. The thickness of the copper lead body is preferably 50 to 300 μm, similarly to the negative electrode tab 16. Such a lead body is particularly preferably used when the copper foil as the negative electrode current collector is thin and the strength is insufficient for direct connection to the negative electrode tab 16.

  The connection between the current collector in the sheet-like negative electrode 12 or the copper lead connected to the current collector and the negative electrode tab 16 is, for example, a method using resistance welding, ultrasonic welding, laser welding, caulking, and a conductive adhesive. Etc., by various methods. Among these methods, ultrasonic welding is particularly suitable.

  The separator 13 is made of, for example, a porous film or a nonwoven fabric made of polyethylene, polypropylene, a fusion of polyethylene and polypropylene, polyethylene terephthalate, polybutylene terephthalate, or the like.

  The thickness of the separator 13 is preferably 10 to 50 μm, and the porosity is preferably 30 to 70%.

  Moreover, the effect which prevents a short circuit can be improved and the reliability of a battery can be improved more by using several separators, such as overlapping a porous film and a nonwoven fabric.

The electrolytic solution used for the laminated battery 1 is made of, for example, a solution (nonaqueous electrolytic solution) in which a solute such as LiPF ₆ or LiBF ₄ is dissolved in a high dielectric constant solvent or an organic solvent. As the high dielectric constant solvent, ethylene carbonate (EC), propylene carbonate (PC), γ-butyrolactone (BL), or the like can be used. The organic solvent is composed of a low-viscosity solvent such as linear dimethyl carbonate (DMC), diethyl carbonate (DEC), and methyl ethyl carbonate (EMC).

  In addition, it is preferable to use the mixed solvent of the high dielectric constant solvent mentioned above and a low-viscosity solvent as electrolyte solution solvent. Alternatively, PVDF, a rubber-based material, an alicyclic epoxy, a material having an oxetane-based three-dimensional crosslinked structure, and the like may be mixed and solidified into the above-described solution to form a polymer electrolyte.

  The laminated battery 1 is arranged such that the thickness direction DR2 of the laminated battery 1 is parallel to the installation surface PP of the laminated battery 1. The laminated battery 1 is sandwiched between the flat plate members 2 and 3 and receives a pressure described later from the flat plate members 2 and 3 in the thickness direction DR2.

  Each of the flat plate members 2 and 3 is made of stainless steel, for example. The flat plate member 2 is disposed on one side of the laminated battery 1 in contact with the laminated battery 1, and the flat plate member 3 is disposed on the other side of the laminated battery 1 in contact with the laminated battery 1. More specifically, the flat plate members 2 and 3 are disposed in contact with the region 14B excluding the sealing portion 14A of the laminate film 14. The region 14 </ b> B is a region facing the sheet-like positive electrode 11 and the sheet-like negative electrode 12.

  Each of the flat plate members 2 and 3 has an area larger than that of the sheet-like negative electrode 12 having a larger area among the sheet-like positive electrode 11 and the sheet-like negative electrode 12. In the laminated battery 1, the area of the region 14B pushed by the flat plate members 2 and 3 is 0.8S or more and 0.98S or less, assuming that the area of the portion other than the sealing portion 14A of the laminated battery 1 is S. It is.

  When each of the flat plate members 2 and 3 has an area smaller than the area of the sheet-like negative electrode 12, deformation of the end portion of the sheet-like negative electrode 12 cannot be prevented. Therefore, in order to prevent the entire deformation of the sheet-like positive electrode 11 and the sheet-like negative electrode 12 including the end portions, the flat plate members 2 and 3 are sheets having the larger area of the sheet-like positive electrode 11 and the sheet-like negative electrode 12. It was decided to have a larger area than the negative electrode 12.

  In addition, when the area of the region 14B is less than 0.8S, the volume of the portion that does not function as a battery in the laminated battery 1 increases, leading to a decrease in effective capacity per volume, and the area of the region 14B is 0. When it exceeds .98S, there is not sufficient space for storing the gas generated inside the laminated battery 1, and the sheet-like positive electrode 11 and the sheet negative electrode 12 are deformed by the pressure of the gas. Therefore, the region 14B has an area of 0.8S or more and 0.98S or less.

  Each of the flat plate members 2 and 3 is disposed so as to be in contact with the side surface of the laminated battery 1 facing the sheet-like positive electrode 11 and the sheet-like negative electrode 12 of the laminated battery 1. That is, each of the flat plate members 2 and 3 is disposed so as to be in contact with the side surface of the laminated battery 1 excluding the space 18 formed in the laminated battery 1 on the positive electrode tab 15 and negative electrode tab 16 side of the laminated battery 1. The That is, each of the flat plate members 2 and 3 is arranged so that the region (= space 18) not pressed by the flat plate members 2 and 3 in the laminated battery 1 is located above the region pressed by the flat plate members 2 and 3. The laminated battery 1 is disposed in contact with the side surface.

  As a result, even if the flat plate members 2 and 3 push the laminated battery 1, the electrolytic solution does not block the space 18, and the gas generated in the laminated battery 1 accumulates in the space 18.

  Therefore, accumulation of gas between the electrodes (between the sheet-like positive electrode 11 and the sheet-like negative electrode 12) can be suppressed. And it can prevent that the sheet-like positive electrode 11 and the sheet-like negative electrode 12 deform | transform with gas.

  Further, the laminated battery 1 is arranged so that the thickness direction DR2 is parallel to the installation surface PP. As a result, the power generation element 30 is pulled toward the installation surface PP, and the volume of the space 18 is increased. Therefore, more gas generated in the laminate-type battery 1 can be stored, and it is possible to further suppress the gas from being stored between the electrodes. Further, the deformation of the sheet-like positive electrode 11 and the sheet-like negative electrode 12 due to the gas can be further prevented.

The pressure with which the flat plate members 2 and 3 press the laminated battery 1 is 1 g / cm ² or more and 100 g / cm ² or less. When the pressure at which the flat plate members 2 and 3 press the laminated battery 1 is less than 1 g / cm ² , the above pressing effect cannot be obtained, and the pressure at which the flat plate members 2 and 3 press the laminated battery 1 is 100 g / cm. ^This is because if the number exceeds ² , the electrolyte in the electrodes (positive electrode and negative electrode) included in each laminated battery 1 is squeezed out, and the laminated battery 1 may not function as a battery.

  FIG. 3 is a view for explaining a method of applying pressure to the laminated battery 1 by the flat plate members 2 and 3.

Referring to FIG. 3, overall thickness D1 of laminated battery 1 and flat plate members 2 and 3 when a pressure of 1 g / cm ² or more and 100 g / cm ² or less is applied to laminated battery 1 by flat plate members 2 and 3. Measure.

  Then, a battery case 40 having a width W1 substantially the same as the measured thickness D1 is produced. In this case, the width W <b> 1 is a width inside the battery case 40.

  Then, the laminated battery 1 and the flat plate members 2 and 3 are accommodated in the battery case 40 so that the region 14B of the laminated battery 1 described above is sandwiched between the flat plate members 2 and 3. In this case, the laminated battery 1 and the flat plate members 2 and 3 are arranged in the battery case 40 so that the positive electrode tab 15 and the negative electrode tab 16 of the laminated battery 1 are located on the opening surface 40B side facing the bottom surface 40A of the battery case 40. It is stored in. In FIG. 3, the opening surface 40B is indicated by a dotted line.

Thereby, the laminated battery 1 receives a pressure of 1 g / cm ² or more and 100 g / cm ² or less from the flat plate members 2 and 3.

  FIG. 4 is a diagram for explaining another method of applying pressure to the laminated battery 1 by the flat plate members 2 and 3.

Referring to FIG. 4, in laminated battery 1, region 14 </ b> B described above is sandwiched between flat plate members 2 and 3. Then, the plate members 2 and 3 are sandwiched between the plate members 41 and 42, and both ends of the plate members 41 and 42 are tightened with screws 43 and 44. In this case, the screws 43 and 44 are tightened so that the flat plate members 2 and 3 apply a pressure of 1 g / cm ² or more and 100 g / cm ² or less to the laminated battery 1.

  More specifically, the screws 43 and 44 are tightened so that the distance between the two plate members 41 and 42 is substantially equal to the thickness D1 described above.

Thereby, the laminated battery 1 receives a pressure of 1 g / cm ² or more and 100 g / cm ² or less from the flat plate members 2 and 3.

  FIG. 4 shows a state in which the laminated battery 1 is arranged in the horizontal direction for easy viewing of the drawing. However, in practice, the method of applying pressure to the above-described laminated battery 1 is a laminated type. The process is executed in a state where the battery 1 is arranged in the vertical direction.

The laminated battery 1 may receive a pressure of 1 g / cm ² or more and 100 g / cm ² or less from the flat plate members 2 and 3 by a method other than the method shown in FIGS.

  FIG. 5 is a process diagram showing a method of manufacturing the lithium ion secondary battery 10 shown in FIG. Referring to FIG. 5, when production of lithium ion secondary battery 10 is started, laminated battery 1 is manufactured (step S1).

  And the flat plate members 2 and 3 are produced (step S2). Thereafter, the laminated battery 1 is arranged so that the thickness direction DR2 of the laminated battery 1 is parallel to the installation surface PP of the laminated battery 1 (step S3).

Then, the laminated battery 1 is sandwiched between the two flat plate members 2 and 3 so as to be in contact with the region 14B of the laminated battery 1 (= the region facing the sheet-like positive electrode 11 and the sheet-like negative electrode 12). A pressure of not less than / cm ^{2 and not} more than 100 g / cm ² is applied to the laminated battery 1 (step S4). Thereby, the lithium ion secondary battery 10 is completed.

  In step S1, the laminated battery 1 is manufactured by the following method. The sheet-like positive electrode 11, the sheet-like negative electrode 12, and the separator 13 are produced by the method described above. Then, the sheet-like positive electrode 11 and the sheet-like negative electrode 12 are laminated via the separator 13, the positive electrode tab 15 is welded to the sheet-like positive electrode 11, and the negative electrode tab 16 is welded to the sheet-like negative electrode 12.

  Thereafter, the laminated sheet-like positive electrode 11, sheet-like negative electrode 12 and separator 13 are covered with a laminate film 14, and the peripheral portion of the laminate film 14 is thermally welded, leaving one side for injecting the electrolyte solution. And electrolyte solution is inject | poured from the remaining one side of the laminate film 14, and the remaining one side of the laminate film 14 is heat-welded after that. Thereby, the laminated battery 1 is completed.

  As described above, in the lithium ion secondary battery 10, the laminated battery 1 includes the flat plate member 2, the region 14 </ b> B facing the sheet positive electrode 11 and the sheet negative electrode 12 sandwiched between the two flat plate members 2 and 3. 3 receives pressure in the thickness direction. Each of the flat plate members 2 and 3 has an area larger than that of the sheet-like negative electrode 12 having a larger area among the sheet-like positive electrode 11 and the sheet-like negative electrode 12. The laminated battery 1 is arranged so that the thickness direction DR2 is parallel to the installation surface PP of the laminated battery 1, and the region of the laminated battery 1 that is not pressed by the flat members 2 and 3 is the flat member 2. 3 above the area pressed by 3.

  As a result, the space 18 in the region not pressed by the flat plate members 2 and 3 is not blocked by the electrolytic solution, and the gas generated in the laminated battery 1 accumulates in the space 18. The entire sheet-like positive electrode 11 and sheet-like negative electrode 12 are pressed by the flat plate members 2 and 3. Furthermore, the power generation element 30 is pulled toward the installation surface PP side of the laminated battery 1, and the volume of the space 18 becomes larger.

  Therefore, accumulation of gas between the electrodes can be suppressed. Moreover, even if the lithium ion secondary battery 10 is used for a long time, the deformation of the sheet-like positive electrode 11 and the sheet-like negative electrode 12 can be accurately prevented. Furthermore, deformation of the sheet-like positive electrode 11 and the sheet-like negative electrode 12 due to the gas generated in the laminated battery 1 can be prevented.

  In the embodiment of the present invention, the flat plate members 2 and 3 constitute a “pressing member”.

  FIG. 6 is a perspective view of the battery pack according to the embodiment of the present invention. Referring to FIG. 6, battery pack 100 according to the embodiment of the present invention includes laminated batteries 101 to 105 and flat plate members 111 to 116.

  Each of the laminated batteries 101 to 105 has the same configuration as the laminated battery 1 shown in FIGS. 1 and 2. Laminated batteries 101-105 are arranged such that thickness direction DR2 of laminated batteries 101-105 is parallel to installation surface PP of laminated batteries 101-105.

  Laminated batteries 101 to 105 are sandwiched between flat plate members 111 and 112, flat plate members 112 and 113, flat plate members 113 and 114, flat plate members 114 and 115, and flat plate members 115 and 116, respectively.

  Laminated batteries 101 to 105 are electrically connected in series. More specifically, the positive electrode tabs 15 of the laminated batteries 101 to 104 are connected to the negative electrode tabs 16 of the laminated batteries 102 to 106, respectively.

  Each of the flat plate members 111 to 116 is made of the same material as the flat plate members 2 and 3 described above. And among the laminated batteries 101 to 105, the areas of the regions pressed by the flat plate members 111 and 112, the flat plate members 112 and 113, the flat plate members 113 and 114, the flat plate members 114 and 115, and the flat plate members 115 and 116, respectively, The laminated battery 1 has the same area as the area of the region pressed by the flat plate members 2 and 3.

  The flat plate member 111 is disposed on one side of the laminated battery 101 in contact with the region 14B of the laminated battery 101.

  The flat plate member 112 is disposed in contact with both the regions 14B of the laminated batteries 101 and 102. The flat plate member 113 is disposed in contact with both regions 14B of the laminated batteries 102 and 103. The flat plate member 114 is disposed in contact with both the regions 14B of the laminated batteries 103 and 104. The flat plate member 115 is disposed in contact with both the regions 14B of the laminated batteries 104 and 105.

  The flat plate member 116 is disposed on the other side of the laminated battery 105 in contact with the region 14 </ b> B of the laminated battery 105.

The flat plate members 111 to 116 push the laminated batteries 101 to 105 in the thickness direction DR2. In this case, the flat plate members 111 to 116 push the laminated batteries 101 to 105 so that a pressure of 1 g / cm ² or more and 100 g / cm ² or less is applied to each laminated battery.

  Laminated batteries 101 to 105 and flat plate members 111 to 116 are alternately arranged along installation surface PP.

In the battery pack 100, the laminate batteries 101 to 105 are applied with a pressure of 1 g / cm ² or more and 100 g / cm ² or less per laminate battery by the method shown in FIG. 3 or FIG.

  FIG. 7 is a process diagram showing a method of manufacturing the battery pack 100 shown in FIG. Referring to FIG. 7, when manufacturing of battery pack 100 is started, laminated batteries 101-105 are manufactured (step S11).

  And the flat plate members 111-116 are produced (step S12). Thereafter, the laminated battery 101 and the flat plate member 111 are arranged so that the region 14B of the laminated battery 101 is in contact with the flat plate member 111 and the thickness direction DR2 of the laminated battery 101 is parallel to the installation surface PP of the laminated battery 101. (Step S13).

  Subsequently, the flat plate member 112 is disposed so that the flat plate member 112 is in contact with the region 14B of the laminated battery 101 (step S14).

  Then, the laminated battery 102 is arranged so that the region 14B of the laminated battery 102 is in contact with the flat plate member 112 and the thickness direction DR2 of the laminated battery 102 is parallel to the installation surface PP of the laminated battery 102 (step S15). .

  Thereafter, steps S14 and S15 are sequentially executed for the flat plate members 113 to 115 and the laminated batteries 103 to 105 (step S16).

  Further, the flat plate member 116 is disposed so that the flat plate member 116 contacts the region 14B of the laminated battery 105 (step S17).

Then, pressure is applied to the laminated batteries 101 to 105 and the flat plate members 111 to 116 so that a pressure of 1 g / cm ² or more and 100 g / cm ² or less is applied per one laminated battery (step S18).

  Thereby, the battery pack 100 is completed.

  As described above, in the battery pack 100, the laminated batteries 101 to 105 include the flat plate members 111 and 112, the flat plate members 112 and 113, the flat plate members 113 and 114, the flat plate members 114 and 115, and the flat plate members 115, 115, respectively. 116, and receives pressure from the plate members 111 and 112, the flat plate members 112 and 113, the flat plate members 113 and 114, the flat plate members 114 and 115, and the flat plate members 115 and 116 in the thickness direction. And each of the flat plate members 111-116 has an area larger than the sheet-like negative electrode 12 with a larger area among the sheet-like positive electrode 11 and the sheet-like negative electrode 12. Each of the laminated batteries 101 to 105 is arranged so that the thickness direction DR2 is parallel to the installation surface PP of the laminated batteries 101 to 105, and among the laminated batteries 101 to 105, the flat plates 111 to 116 are used. The region that is not pressed is disposed above the region that is pressed by the flat plate members 111 to 116.

  As a result, in each of the laminated batteries 101 to 105, the space 18 in the region where the electrolytic solution is not pressed by the flat plate members 111 to 116 is not blocked, and the gas generated in the laminated batteries 101 to 105 is caused by the flat plate members 111 to 116. It collects in the space 18 of the area | region which is not pushed. Further, the entire sheet-like positive electrode 11 and the sheet-like negative electrode 12 are pressed by the flat plate members 111 to 116. Furthermore, the power generation element 30 is pulled toward the installation surface PP of the laminated batteries 101 to 105, and the volume of the space 18 becomes larger.

  Therefore, in the battery pack 100, it can suppress that gas accumulates between electrodes. And the deformation | transformation of the sheet-like positive electrode 11 and the sheet-like negative electrode 12 by the gas generated in each laminated battery 101-105 can be prevented. Moreover, even if the battery pack 100 is used for a long time, the deformation of the sheet-like positive electrode 11 and the sheet-like negative electrode 12 can be accurately prevented.

Hereinafter, based on an Example, this invention is demonstrated concretely.
Example 1
90 parts by weight of spinel Mn having a primary particle size of 700 nm, 5 parts by weight of acetylene black having a primary particle size of 100 nm, and 5 parts by weight of PVDF were mixed by a mixer using NMP as a solvent to prepare a positive electrode mixture. The sheet-like positive electrode 11 was prepared by applying the prepared positive electrode mixture (paint) to both surfaces of an aluminum current collector. In this case, the thickness of the positive electrode mixture applied to one side of the current collector is 30 μm.

Also, 90 parts by weight of Li ₄ Ti ₅ O ₁₂ having a primary particle diameter of 1 μm, 5 parts by weight of acetylene black having a primary particle diameter of 100 nm, and 5 parts by weight of PVDF were mixed by a mixer using NMP as a solvent. Thus, a negative electrode mixture was produced, and the produced negative electrode mixture (paint) was applied to both surfaces of an aluminum current collector to produce a sheet-like negative electrode 12. In this case, the thickness of the negative electrode mixture applied to one side of the current collector is 25 μm.

  Then, the sheet-like positive electrode 11 and the sheet-like negative electrode 12 were cut into 100 mm × 100 mm, and 20 sets of the cut sheet-like positive electrode 11 and the sheet-like negative electrode 12 were stacked with a porous separator interposed therebetween, thereby producing a power generation element 30. .

  Thereafter, the power generation element 30 was covered with the laminate film 14, and the periphery of the laminate film 14 was sealed by thermal welding, leaving one side of the square laminate film 14.

Subsequently, LiPF ₆ was dissolved at a concentration of 1.5 mol / l in a solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 3 to prepare an electrolytic solution. Then, 10 ml of the produced electrolyte solution is injected into the laminate film 14 from one side of the laminate film 14 that is not sealed, and the other side of the laminate film 14 is sealed by thermal welding to produce a laminated battery. did.

  After that, the laminated battery region 14B was sandwiched between two stainless steel plates so that the area of the pressing part was 0.9S, and a load of 1 kg was applied to produce a lithium ion secondary battery.

(Example 2)
In Example 1, a lithium ion secondary battery was fabricated in the same manner as in Example 1 except that the area of the portion pressed by the stainless steel plate was 0.95S.

(Example 3)
In Example 1, a lithium ion secondary battery was produced in the same manner as in Example 1 except that the pressing load was 3 kg.

Example 4
Ten laminated batteries prepared in Example 1 are arranged in the horizontal direction, and stainless steel plates are arranged between the laminated batteries and at both ends of the ten laminated batteries so that the area of the holding portion is 0.9S. Then, a load of 5 kg was applied in the thickness direction of the laminated battery to produce a battery pack.

(Comparative Example 1)
In Example 1, a lithium ion secondary battery was produced in the same manner as in Example 1 except that the sandwiching by the stainless steel plate was omitted.

(Comparative Example 2)
In Comparative Example 1, a lithium ion secondary battery was produced in the same manner as in Comparative Example 1, except that the injection amount of the electrolytic solution was 20 ml.

(Comparative Example 3)
In Example 1, a lithium ion secondary battery was produced in the same manner as in Example 1 except that the laminate-type battery was sandwiched between stainless plates so that the area of the holding part was 1.0S.

(Comparative Example 4)
In Example 1, a lithium ion secondary battery was fabricated in the same manner as in Example 1 except that the area of the portion pressed by the stainless steel plate was 0.99S.

(Comparative Example 5)
In Example 1, the area of the stainless steel plate was 90% of the area of the electrodes (sheet-like positive electrode and sheet-like negative electrode), and the area of the presser part was 0.9 S. An ion secondary battery was produced.

(Comparative Example 6)
In Example 1, a lithium ion secondary battery was produced in the same manner as in Example 1 except that the pressing load was 50 g.

(Comparative Example 7)
In Example 1, a lithium ion secondary battery was produced in the same manner as in Example 1 except that the pressing load was 20 kg.

(Comparative Example 8)
In Example 4, a battery pack was produced in the same manner as in Example 4 except that 10 laminated batteries were arranged in the vertical direction.

  A cycle test and a high-temperature storage test were performed on the batteries prepared in Examples 1 to 4 and Comparative Examples 1 to 8 described above.

  A cycle test was performed by evaluating the capacity maintenance rate after 5000 cycles, with 2.9 V and 10 C CC charging at the end and CC discharge at 1.5 V and 10 C as one cycle.

  In addition, a high temperature storage test was conducted by evaluating the capacity retention rate when left in an environment of 80 ° C. for 1 week in a charged state.

  The results of the cycle test and the high temperature storage test are shown in Table 1.

  The batteries of Examples 1 to 4 are superior to the batteries of Comparative Examples 1 to 8 in both the capacity retention after cycle and the capacity retention after high temperature storage.

  In the battery of Comparative Example 2, it is considered that the capacity retention rate after the cycle was high because the electrolyte solution was excessive, so that the electrolyte solution was not depleted even when the electrode was deformed. Further, in the battery of Comparative Example 2, the capacity retention rate after high-temperature storage is remarkably low because the elution and movement of the metal of the positive electrode is promoted due to the excess electrolyte solution, and the metal is deposited on the separator and soft short It is estimated that this was caused.

  In the battery of Comparative Example 5, the capacity retention rate after high-temperature storage is remarkably low because the deformation of the electrode part that is not suppressed by the stainless steel plate becomes significant, and an abnormal electric field is generated to accelerate metal elution. Presumed.

  Moreover, after performing a cycle test and a high temperature storage test, the battery was disassembled and the surface state of the electrode was observed. As a result, in the batteries of Examples 1 to 4, electrode deformation and discoloration were not observed. On the other hand, in the batteries of Comparative Examples 1 to 8, deformation of the electrodes was observed. Further, in the batteries of Comparative Examples 1 to 8, mottled discoloration was observed in the vicinity of the tab, and the edge of the electrode was severely damaged.

  Thus, in the batteries of Examples 1 to 4, deformation and discoloration of the electrodes were not observed, and it was demonstrated that the deformation of the electrodes can be accurately prevented by pressing the laminated battery with the stainless steel plate.

  The lithium ion secondary battery according to the embodiment of the present invention includes a laminated battery and a flat plate member that pushes the laminated battery from the thickness direction, and the thickness direction of the laminated battery is parallel to the installation surface of the laminated battery. The laminated battery is disposed so that the region that is not pressed by the flat plate member in the laminated battery may be disposed above the region that is pressed by the flat plate member.

  With such a configuration, the space in the region where the electrolyte solution is not pushed by the flat plate member is not blocked, the gas generated in the laminated battery is accumulated in the space in the region not pushed by the flat plate member, and the gas is accumulated between the electrodes. This is because it can be suppressed.

  The battery pack according to the embodiment of the present invention includes a plurality of laminated batteries and a plurality of flat plate members so that the thickness direction of each laminated battery is parallel to the installation surface of the plurality of laminated batteries. A plurality of laminate-type batteries are arranged, and it is only necessary that the area of each laminate-type battery not pressed by the flat plate member is arranged above the area pressed by the flat plate member.

  With such a configuration, in each laminated battery, the space of the region where the electrolyte is not pressed by the flat plate member is not blocked, and the gas generated in the laminated battery is accumulated in the space of the region where the flat plate member is not pressed, It is because it can suppress that gas accumulates between electrodes.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to a lithium ion secondary battery and a battery pack including the same.

  1,101-105 Laminated battery, 2,3, 111-116 Flat plate member, 10 Lithium ion battery, 11 Sheet-like positive electrode, 12 Sheet-like negative electrode, 13 Separator, 14 Laminated film, 14A, Sealing part, 15 Positive electrode tab , 16 negative electrode tab, 17 lead body, 18 space, 40 battery case, 41, 42 plate member, 43, 44 screw, 100 battery pack.

Claims (6)

A laminated battery having a structure in which a power generation element is laminated by a laminate member;
It has a flat plate shape, and includes a pressing member that presses the laminated battery in the thickness direction of the laminated battery,
The laminated battery is arranged so that the thickness direction of the laminated battery is parallel to the installation surface of the laminated battery,
The pressing member has a larger area than the larger electrode of the positive electrode and the negative electrode included in the power generation element, and presses the side surface of the laminated battery facing the positive electrode and the negative electrode.
The 1st area | region which is not pressed by the said press member among the said laminate type batteries is a lithium ion secondary battery arrange | positioned above the 2nd area | region pressed by the said press member.   2. The lithium ion secondary battery according to claim 1, wherein the second region has an area of 80% or more and 98% or less of an area of a portion surrounded by the sealing portion of the laminated battery. The lithium ion secondary battery according to claim 1 or 2, wherein a pressure at which the pressing member presses the laminated battery is 1 g / cm ² or more and 100 g / cm ² or less. A plurality of laminated batteries,
A plurality of flat plate members disposed between two adjacent laminated batteries and on both ends of the plurality of laminated batteries, and pressing the plurality of laminated batteries in the thickness direction of the laminated battery;
Each of the plurality of laminated batteries is arranged such that a thickness direction of the laminated batteries is parallel to an installation surface of the plurality of laminated batteries,
The plurality of laminated batteries and the plurality of flat plate members are alternately arranged along the installation surface,
Each of the plurality of flat plate members has a larger area than the larger electrode of the positive electrode and the negative electrode of the laminate battery, and pushes the side surface of the laminate battery facing the positive electrode and the negative electrode. ,
In each of the plurality of laminated batteries, the first region that is not pressed by the flat plate member is disposed above the second region that is pressed by the flat plate member.   5. The battery pack according to claim 4, wherein the second region has an area of 80% or more and 98% or less of an area of a portion surrounded by the sealing portion of the laminated battery. The battery pack according to claim 4 or 5, wherein a pressure at which the plurality of flat plate members press the plurality of laminated batteries is 1 g / cm ² or more and 100 g / cm ² or less per one laminated battery.

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