JP6520565B2 - Lithium ion secondary battery and assembled battery - Google Patents

Description

  The present invention relates to a lithium ion secondary battery and a battery pack, and more particularly to a lithium ion secondary battery and a battery pack in which deterioration of a negative electrode active material is suppressed.

  In recent years, lithium-ion secondary batteries have come to be used not only as electronic devices such as mobile devices but also as power sources for transportation devices such as automobiles, and there is a demand for higher capacity. In lithium ion secondary batteries using graphite for the negative electrode currently put into practical use, the battery capacity is in a saturated state, and it is difficult to achieve a significant increase in capacity. Therefore, lithium ion secondary batteries have been developed which use, as the negative electrode, a material which is alloyed with Li such as Si other than graphite. A lithium ion secondary battery using a material which is alloyed with Li other than graphite for the negative electrode has a problem that the expansion and contraction at the negative electrode during charge and discharge are large, and the durability of the battery is deteriorated. For example, the volume expansion when occluding Li ions is about 1.2 times in the case of a graphite material, while in the case of Si material, when Si and Li are alloyed, it changes from an amorphous state to a crystalline state and a large volume change The cycle life of the electrode is reduced to cause (about 4 times).

Further, in the case of the Si negative electrode active material, there is a trade-off relationship between capacity and cycle durability, and there is a problem that it is difficult to improve high cycle durability while showing high capacity.
In order to solve such a problem, for example, Patent Document 1 proposes a negative electrode active material for a lithium ion secondary battery, which includes an amorphous alloy having Si _x M _y Al. In the present invention, by minimizing the content of metal M, in addition to high capacity, good cycle life is indicated.
Moreover, in patent document 2, suppressing the battery expansion accompanying expansion of a negative electrode active material is proposed by applying stress with respect to the inside via the exterior material of a battery.

  However, unlike expansion due to charging and discharging of a general battery, in expansion in a silicon-based negative electrode active material, the active material itself is cracked by expansion and detached from the conductive network, or a side reaction with an electrolyte or the like May be inactivated. Therefore, attempts to improve durability by applying stress from the outside of the battery have been limited to suppressing expansion of the inter-electrode distance due to expansion, and have not been able to suppress deterioration of the negative electrode itself derived from a chemical reaction.

Japanese Patent Application Publication No. 2009-517850 JP, 2011-91020, A

  An object of the present invention is to suppress deterioration of a lithium ion secondary battery and an assembled battery incorporating the same, which is caused by pulverization and dissipation due to volumetric expansion of a negative electrode active material due to charge and discharge.

  In the embodiment of the present invention, the hard magnetic material is disposed outside the power generation element of the lithium ion secondary battery, and the negative electrode active material having ferromagnetism has a magnetic force, so that the negative electrode active material is pulverized due to expansion and contraction. Dissipation is suppressed by the mutual attraction of the fine powder particles.

  In a lithium ion secondary battery and an assembled battery incorporating the same, the deterioration of the battery and the assembled battery due to the pulverization and dissipation due to volumetric expansion of the negative electrode active material containing a material to be alloyed with Li by volumetric expansion due to charge and discharge is suppressed be able to.

BRIEF DESCRIPTION OF THE DRAWINGS It is the cross-sectional schematic which showed typically the whole structure of the flat type lithium ion secondary battery of embodiment of this invention. It is the figure which showed typically the example of arrangement | positioning of the hard magnetic body in embodiment of this invention. The electrode structure of the negative electrode of embodiment of this invention, and a prior art example is shown typically. BRIEF DESCRIPTION OF THE DRAWINGS It is the cross-sectional schematic which represented typically the whole structure of the cylindrical lithium ion secondary battery of embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS The external view of the assembled battery of embodiment of this invention, and a module structure are shown typically. It is the cross-sectional schematic which showed typically the whole structure of the assembled battery of embodiment of this invention. It is the cross-sectional schematic of the flat type battery integrated in the assembled battery of embodiment of this invention.

The lithium ion secondary battery according to one embodiment of the present invention may be any one in which a hard magnetic material is disposed on the outside of a power generation element including the negative electrode using a negative electrode including a ferromagnetic material described below, There is no particular restriction on the other configuration requirements. By arranging the hard magnetic body outside the power generation element, the negative electrode active material including the ferromagnetic material of the negative electrode constituting the power generation element becomes magnetic, so even if cracking occurs due to expansion of the negative electrode active material, it is broken and pulverized The solidified particles can be aggregated to suppress dissipation.
The power generation element is configured by laminating a positive electrode, a negative electrode, and a separator, and includes an electrolytic solution therebetween. The laminate may be a single layer, but the power generating element may be configured as a structure that is usually stacked in a plurality of layer thickness directions, or cylindrically wound. The positive electrode contains a positive electrode active material (also referred to as a positive electrode active material), and the negative electrode contains a negative electrode active material (negative electrode active material).

  The material of the hard magnetic material is not particularly limited as long as it is a magnetic material having a magnetic flux density to such an extent that crushed powder of a ferromagnetic material is aggregated. For example, the magnetic flux density of the hard magnetic body may be 0.05 T or more. If the magnetic flux density is 0.05 T or more, the effect of aggregating the crushed powder of the ferromagnetic material can be obtained. Moreover, if it is 0.08 T or more, cohesion will become stronger and it can prevent dissipation. The magnetic flux density of the hard magnetic body may be 0.1 T or more. The hard magnetic material may be a magnetic material having a large coercive force and not easily demagnetized with respect to an external magnetic field, and a general magnet or a permanent magnet can be used. As the hard magnetic material, rare earth magnets such as ferrite magnets, NdFeB magnets, SmCo magnets, platinum iron, platinum cobalt, FeCoCr alloy, etc. can be used, but the present invention is not limited thereto. The hard magnetic material may have a thermal conductivity at 20 ° C. of 0.5 W / mk or more. If the thermal conductivity at 20 ° C. is 0.5 W / mk or more, heat in the battery is likely to be released.

  The negative electrode active material includes a material that can be alloyed with Li, and further includes a ferromagnetic material. The substance that can be alloyed with Li is not particularly limited as long as it can exchange electrons by alloying with Li, but can be selected from, for example, carbon (C), silicon (Si), tin (Sn), etc. . When the saturation magnetic flux density obtained by the magnetization curve is 1 μT or more, the ferromagnetic substance has a tendency to aggregate and dissipate even if it is broken. The ferromagnetic substance is not particularly limited as long as it is a material having ferromagnetism, but can be selected from, for example, metals such as iron (Fe), cobalt (Co), nickel (Ni) and the like. Usually, the ferromagnetic metal and the element to be alloyed with Li are alloyed and in a solid solution state. By being in a solid solution state, the entire negative electrode active material can have magnetism. Carbon (C) may be in any form such as natural graphite, artificial graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon or hard carbon. The negative electrode active material may also contain other elements, compounds, alloys and the like.

When the lithium ion secondary battery of the present embodiment is distinguished by form and structure, any form and structure conventionally known such as flat type (laminated type) battery and cylindrical type (wound type) battery can be used. Good.
In addition, when viewed from the electrical connection form (electrode structure) in the lithium ion secondary battery of the present embodiment, either the non-bipolar (internal parallel connection type) battery or the bipolar (internal serial connection type) battery It may be.
When the type of electrolyte layer in the lithium ion secondary battery of this embodiment is distinguished, a solution electrolyte type battery using a solution electrolyte such as a non-aqueous electrolyte solution in the electrolyte layer, and a polymer electrolyte in the electrolyte layer are used. The present invention is applicable to any of the conventionally known electrolyte layer types such as polymer batteries. The polymer battery is further divided into a gel electrolyte battery using a polymer gel electrolyte (also referred to simply as a gel electrolyte) and a solid polymer (all solid) battery using a polymer solid electrolyte (also referred to simply as a polymer electrolyte). Be

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. These are embodiments, and the scope of the present invention is not limited to these embodiments, and it goes without saying that there may be other embodiments included in the claims. In the description of the drawings, the same elements will be denoted by the same reference symbols, without redundant description. Also, the dimensional proportions of the drawings are exaggerated for the convenience of the description, and may differ from the actual proportions.

First Embodiment
FIG. 1 is a schematic cross-sectional view schematically showing the entire structure of the lithium ion secondary battery of the first embodiment. As shown in FIG. 1, the present embodiment is a flat type (stacked type) lithium ion secondary battery.
As shown in FIG. 1, the lithium ion secondary battery 10 according to the first embodiment includes an exterior member 9 formed of a plurality of power generation elements 1 formed by alternately stacking a plurality of negative electrodes 11, separators 17 and positive electrodes 12. Sealed by The lithium ion secondary battery 10 has a negative electrode terminal plate 5 and a positive electrode terminal plate 7.

Referring to FIG. 1, in a lithium ion secondary battery 10, a substantially rectangular power generation element 1 in which a charge / discharge reaction proceeds is sealed inside a laminate sheet which is an exterior material 9. The power generation element 1 has a configuration in which a negative electrode 11, a separator 17, and a positive electrode 12 are stacked. The adjacent negative electrode 11, separator 17 and positive electrode 12 form one unit cell layer 19. The power generation element 1 has a configuration formed by electrically connecting in parallel by stacking a plurality of unit cell layers 19. In the lithium ion secondary battery 10, the positive electrode 12 is positioned on both outermost layers of the power generation element 1 by reversing the arrangement of the negative electrode 11 and the positive electrode 12 of the lithium ion secondary battery 10 shown in FIG. Good.
The lithium ion secondary battery 10 has a rectangular flat shape, and draws out the negative electrode terminal plate 5 and the positive electrode terminal plate 7 for extracting electric power from opposite ends. The heat generating element 1 is sealed in a state where the negative electrode terminal plate 5 and the positive electrode terminal plate 7 are drawn out by heat welding around the exterior material 9.

<Hard magnetic material>
In the present embodiment, the core material 3 including the hard magnetic material is included in the inside of the laminate film which is the packaging material 9. The core material 3 is formed of a hard magnetic material in the form of a sheet, and both surfaces thereof are fused by a laminate film. By including the hard magnetic material as the core material 3 in the sheathing material 9, the battery space can be effectively used. In addition, the hard magnetic body may be disposed inside the exterior material 9, or may be disposed outside or inside the exterior material 9. The form of the hard magnetic body is a form that can be fixed in the battery module It may be in any form. It may be in any form such as the form of the hard magnetic material itself, the form of a hard magnetic sheet formed of a binder resin and a hard magnetic powder, or the hard magnetic layer formed by applying the package material 9.
The hard magnetic body may have a structure capable of coping with compression in the battery module, for example, by using a rubber-like composition having elasticity as a binder to form a rubber-like elastic body. The elastic modulus of the rubber-like elastic body may be 100 MPa or less. Moreover, the impact resistance of a lithium ion battery can be improved by installing in the outer surface etc. of a battery exterior material as a rubber-like elastic body.

FIG. 2 is a view schematically showing an arrangement example of the hard magnetic material. For example, the hard magnetic body 22 may be disposed on the upper and lower surfaces of the packaging material 21 formed of a laminate film as shown in FIG. 2 (a), or as shown in FIG. 2 (b) You may arrange | position to the side of the exterior material 21 formed. Moreover, as shown in FIG.2 (c)-(d), you may arrange | position between the several exterior materials 21 containing an electric power generation element, and / or the side surface. When the hard magnetic sheet is made of an adhesive sheet material, the outer covering materials 21 of the power generation element can be adhered. By appropriately selecting the positional relationship with the power generation element as described above, magnetic lines of force from the hard magnetic material can be transmitted in the film thickness direction of the electrode, and the magnetization of the negative electrode active material can be made stronger. .
Returning to FIG. 1, the configuration of the lithium ion secondary battery 10 may be any known material used for a general lithium ion secondary battery, and is not particularly limited. The current collector 11a and the negative electrode active material layer 13 of the negative electrode 11 that can be used for the lithium ion secondary battery 10, and the current collector 12a and the positive electrode active material layer 15 of the positive electrode 12, and the separator 17 will be described.

<Negative electrode>
In the negative electrode 11, a negative electrode active material layer 13 is formed on both sides of the negative electrode current collector 11a.
The negative electrode current collector 11a of the negative electrode 11 is, for example, a stainless steel foil. However, without being particularly limited to this, it is also possible to use a plated material of, for example, aluminum foil, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a combination of these metals.
The negative electrode active material layer 13 of the negative electrode 11 contains a substance that can be alloyed with Li and a ferromagnetic material. The substance that can be alloyed with Li is not particularly limited as long as it is a substance that can give and receive an electron by alloying with Li, but can be selected from one of carbon (C), silicon (Si) and tin (Sn) it can. Carbon (C) may be in any form such as natural graphite, artificial graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon or hard carbon. The ferromagnetic substance is not particularly limited as long as it is a material having ferromagnetism, but can be selected from one or more of iron (Fe), cobalt (Co), nickel (Ni), and the like. In addition, the negative electrode active material may contain other elements, compounds, alloys and the like. For example, titanium oxide, silicon oxide, a composite compound of lithium and a transition metal, Li alloy and the like can be mentioned.

As described above, the negative electrode active material may have a magnetic force, and the saturation magnetic flux density obtained by the magnetization curve may be 1 μT or more. When the saturation magnetic flux density is 1 μT or more, the negative electrode active material tends to aggregate even if it is expanded and pulverized by alloying with Li. FIG. 3 schematically shows this state, and FIG. 3 (a) shows the structure of the negative electrode, in which the electrode layer containing the negative electrode active material 32, the binder 34 and the conductive additive 33 on the current collector 31. It is formed. As shown in FIG. 3B, when the negative electrode active material 32 does not have a magnetic force, there is a problem that the negative electrode active material 32 is broken, pulverized and dissipated when the battery is repeatedly used. On the other hand, as shown in FIG. 3C, when a hard magnetic body (not shown) is disposed outside the power generation element (not shown) and a ferromagnetic body is used as the negative electrode active material 32, the negative electrode active material Since No. 32 has a magnetic force, even if it is pulverized, magnetic particles can be aggregated to prevent dissipation.
Note that FIG. 3 is only a schematic view conceptually illustrating the operation of the embodiment of the present invention, and the present invention is not limited by such an operation or the like.

<Positive electrode>
Returning to FIG. 1, in the positive electrode 12, the positive electrode active material layer 15 is formed on both sides of the positive electrode current collector 12 a.
As the positive electrode current collector 12a, the same material as that which can be used for the negative electrode current collector 11a can be used.
A generally known material can be used for the positive electrode active material layer 15 of the positive electrode 12. For example, lithium such as LiMn ₂ 0 ₄ - mentioned transition metal phosphate compound, a solid solution system, ternary, NiMn-based, NiCo system, and spinel Mn system - transition metal composite oxide, lithium - transition metal sulfates, lithium However, the invention is not particularly limited thereto. From the viewpoint of capacity and output characteristics, it is preferable to apply a lithium-transition metal composite oxide.
A binder and a conductive support agent can be added to the negative electrode active material 13 and the positive electrode active material 15 as necessary.

<Binder>
The binder is added for the purpose of binding the active materials or the active material and the current collector to maintain the electrode structure. As a binder used for a positive electrode active material layer, any of a well-known binder can be used. For example, polyvinylidene fluoride, polyimide, styrene butadiene rubber, carboxymethylcellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, polyamide, polyamide imide and the like are used, but it is not limited thereto. These suitable binders are excellent in heat resistance, and furthermore, the potential layer is very wide and stable to both the positive electrode potential and the negative electrode potential, and can be used for the active material layer. These binders may be used alone or in combination of two or more.

<Conductive agent>
The conductive aid refers to an additive compounded to improve the conductivity of the positive electrode active material layer or the negative electrode active material layer. Examples of the conductive aid include carbon materials such as carbon black such as acetylene black, graphite and vapor grown carbon fiber. When the active material layer contains a conductive additive, an electronic network inside the active material layer is effectively formed, which can contribute to the improvement of the output characteristics of the battery.

<Separator>
The separator 17 has a porous shape and is breathable. The separator 30 constitutes an electrolyte layer by being impregnated with the electrolyte. The material of the separator 30, which is an electrolyte layer, is, for example, porous PE (polyethylene) having air permeability which can permeate the electrolyte. However, it is also possible to use other polyolefins such as PP (polypropylene), laminates having a three-layer structure of PP / PE / PP, polyamides, polyimides, aramids, non-woven fabrics, etc. without particular limitation thereto. is there. The non-woven fabric is, for example, cotton, rayon, acetate, nylon, polyester.

<Electrolyte>
The electrolyte host polymer is, for example, PVDF-HFP (copolymer of polyvinylidene fluoride and hexafluoropropylene) containing 10% of HFP (hexafluoropropylene) copolymer. However, without being limited thereto, it is also possible to apply another polymer having no lithium ion conductivity or a polymer having a ion conductivity (solid polymer electrolyte). Other polymers having no lithium ion conductivity are, for example, PAN (polyacrylonitrile) and PMMA (polymethyl methacrylate). The polymer having ion conductivity is, for example, PEO (polyethylene oxide) or PPO (polypropylene oxide).

The electrolytic solution held by the host polymer contains, for example, an organic solvent composed of PC (propylene carbonate) and EC (ethylene carbonate), and a lithium salt (LiPF ₆ ) as a supporting salt. The organic solvent is not particularly limited to PC and EC, and other cyclic carbonates, linear carbonates such as dimethyl carbonate, and ethers such as tetrahydrofuran can be applied. Lithium salt, without particularly limited to LiPF _6, other inorganic acid anion salts, organic acid anion salts such as LiCF ₃ SO _3, can be applied.

The thickness of the negative electrode 11 and the positive electrode 12 is not particularly limited, and can be set in consideration of the purpose of use of the battery.
In the lithium ion secondary battery of the present embodiment, the negative electrode active material contains a ferromagnetic material, and the power generation element including the negative electrode is surrounded by the outer covering material including the hard magnetic material as a core material. have. For this reason, even if Li ions are absorbed in the negative electrode active material and expanded and crushed during charging of the lithium ion secondary battery, the crushed negative electrode active material is not dissipated because it is aggregated by magnetic force. Therefore, the durability of the lithium ion secondary battery can be improved even if a material having a high expansion coefficient by alloying with Li is used as the negative electrode active material.

Second Embodiment
FIG. 4 is a schematic view schematically showing a cross section of a cylindrical lithium ion secondary battery of the second embodiment. As shown in FIG. 4, in the lithium ion secondary battery 40 according to the second embodiment, the battery case is formed in a state where the power generation element 41 formed by laminating the negative electrode, the separator, and the positive electrode is spirally wound. (Exterior material) 43 is sealed. A hard magnetic sheet 44 containing a hard magnetic material is cylindrically disposed on the outside of the battery case (exterior material) 43.
The non-aqueous electrolyte solution 42 is filled in the battery container 43a. The type of non-aqueous electrolyte solution 42 is not particularly limited. The non-aqueous electrolyte 42 can be appropriately used according to the type of lithium ion secondary battery, and the type of negative electrode active material and positive electrode active material to be used. In general, the non-aqueous electrolyte solution 42 is composed of a non-aqueous solution in which a non-aqueous electrolyte is dissolved in a non-aqueous solvent. Examples of non-aqueous electrolytes include lithium hexafluorophosphate (LiPF ₆ ). Specific examples of the non-aqueous solvent include ethylene carbonate (EC), 4-fluoroethylene carbonate (FEC), ethyl methyl carbonate (EMC), and mixed solvents thereof.

In the cylindrical lithium ion secondary battery of the present embodiment, the materials used for the negative electrode, the separator, the positive electrode, the hard magnetic body, etc. constituting the lithium ion secondary battery may be the same as in the first embodiment. it can.
The battery case 43 preferably has high rigidity from the viewpoint of high impact of the lithium ion secondary battery, and the volume of the storage space is preferably substantially unchanged. Therefore, the battery case 43 may be made of metal such as stainless steel or nickel.
In the present embodiment, the hard magnetic body is disposed on the outside of the battery case (exterior material) 43 as the hard magnetic sheet 44, but if the arrangement location of the hard magnetic body is on the outside of the power generation element 41, the battery case (exterior Material) Even the inner surface 43a may be disposed in the battery container (exterior material) 43. The magnetic lines of force generated from the hard magnetic material may be disposed so as to pass through the electrode thickness direction of the power generation element. The form of the hard magnetic material is also the form of the hard magnetic material itself, the form of the hard magnetic sheet formed of the binder resin and the hard magnetic powder, or the hard magnetic layer formed by applying to a battery container (exterior material) 43 or the like. It may be in any form.

The hard magnetic body may have a structure capable of coping with compression in a battery container by using, for example, a rubber-like composition having elasticity as a binder to form a rubber-like elastic body. Moreover, the impact resistance of a lithium ion battery can be improved by installing in the outer surface etc. of a battery container as a rubber-like elastic body.
In the lithium ion secondary battery of the present embodiment, the negative electrode active material contains a ferromagnetic material, and the power generation element including the negative electrode is surrounded by the outer covering material including the hard magnetic material as a core material. have. For this reason, even if Li ions are absorbed in the negative electrode active material and expanded and crushed during charging of the lithium ion secondary battery, the crushed negative electrode active material is not dissipated because it is aggregated by magnetic force. Therefore, the durability of the lithium ion secondary battery can be improved even if a material having a high expansion coefficient by alloying with Li is used as the negative electrode active material.

Third Embodiment
The third embodiment relates to a battery assembly obtained by connecting a plurality of the lithium ion secondary batteries of the first embodiment in parallel or in series. In the present embodiment, the hard magnetic material is not limited to being disposed on the outside of the power generation element, but the location to be disposed is the outer layer between the plurality of lithium ion secondary batteries and the plurality of lithium ion secondary batteries It is arranged in the outermost layer.
In the third embodiment, the configuration and materials of the individual lithium ion secondary batteries constituting the assembled battery may be the same configuration and materials as those described in the first embodiment.

  For example, the battery pack may have a module structure. In this case, the module structure has a plurality of spaces for accommodating a plurality of lithium ion secondary batteries, and the hard magnetic material can be disposed between the module structure spaces or in the outermost layer. In FIG. 5, the structure in case each lithium ion secondary battery which comprises an assembled battery is cylindrical is shown typically. FIG. 5 (a) schematically shows the battery assembly 51 and its internal structure, and FIGS. 5 (b) and 5 (c) show a module structure 53 and a module structure disposed inside the battery assembly. A hole 52 is shown in which a cylindrical lithium ion secondary battery formed in the body 53 is inserted.

  In the present embodiment, a hard magnetic body (not shown) may form, for example, a module structure 53. The surface of the module structure 53 (hard magnetic body) can form an insulating layer so as not to be in direct contact with the electrode. In addition, the hard magnetic body and the module structure 53 can be formed as separate members on the inner peripheral surface of the inside of the module structure 53 or the hole (space) 52 into which the cylindrical battery is inserted. The magnetic lines of force generated from the module structure 53 or the hard magnetic material may be disposed so as to pass through the electrode thickness direction of the power generation element. Thus, the battery space can be effectively utilized by arranging the hard magnetic body inside the module structure (structure itself) or adjacent to the module structure.

Although FIG. 5 shows that the module structure has a battery accommodation space, the form of the module structure is not particularly limited as long as it is a structure for combining batteries. It may be in the form. At that time, the fastening material or the fixing material itself may be formed of a hard magnetic material, or a hard magnetic material may be attached. By using the module structure as the fastening material or the fixing material, it is possible to suppress the displacement of the battery due to the vibration.
The hard magnetic body is, for example, a rubber-like elastic body using a rubber-like composition having elasticity as a binder to form a rubber-like elastic body, and disposed in a space of a module structure or used as a fastening material to expand and shrink the battery. Can relieve the pressure involved. The elastic modulus of the rubber-like elastic body may be, for example, 100 MPa or less. Moreover, the impact resistance of a lithium ion battery can be improved by comprising module structure itself as a rubber-like elastic body containing a hard magnetic body.

The hard magnetic material may have a thermal conductivity at 20 ° C. of 0.5 W / mk or more. By setting the thermal conductivity at 20 ° C. to 0.5 W / mk or more, heat distortion during heat generation of the battery can be suppressed, and deterioration of the lithium ion secondary battery can be prevented. Heat dissipation can be expected to be enhanced by disposing a hard magnetic material having high thermal conductivity around a portion having a large amount of heat generation, such as an output terminal portion.
Although FIG. 5 shows the case where each lithium ion secondary battery constituting the assembled battery is cylindrical, the shape of each lithium ion secondary is any shape such as flat type, prismatic type, rectangular solid, etc. May be

Below, the case where each lithium ion secondary battery which comprises an assembled battery is a flat type is demonstrated in detail. FIG. 6 (a) is a perspective view for explaining the battery assembly of this embodiment, and FIG. 6 (b) is a perspective view for explaining a cell unit inside the metal container shown in FIG. 6 (a). FIG. 7 is a cross-sectional view for explaining a flat battery constituting the laminate shown in FIG. 6 (b). The flat type battery which comprises the laminated body shown by FIG.6 (b) may have a structure shown in FIG.
As shown to Fig.6 (a), the battery module 100 which concerns on this embodiment has the case (metal container) 120, and as shown in FIG.6 (b), the cell unit is shown in the inside of the said case 120. 140 and an insulating cover 170 with electrical insulation. The battery module 100 can be used alone, but, for example, a plurality of battery modules 100 are serialized and / or parallelized to form a battery pack corresponding to desired current, voltage, and capacity. be able to. The insulating cover 170 prevents a short circuit with the case 120 as described later, there is no need to increase the insulation of the inner surface of the case 120, and an increase in product cost is suppressed.

In FIG. 6A, the case 120 is used to accommodate the cell unit 140, and has a lower case 122 having a substantially rectangular box shape and an upper case 124 forming a lid. The edge of the upper case 124 is crimped to the edge of the peripheral wall of the lower case 122 by caulking. The lower case 122 and the upper case 124 are formed of a relatively thin steel plate or aluminum plate, and are given a predetermined shape for securing strength by pressing or for holding the cell unit 140.
Lower case 122 and upper case 124 have through holes 130. The through holes 130 are disposed at four places in the corner, and are used to insert through bolts (not shown) for stacking a plurality of battery modules 100 stacked to be held as a battery. Lower case 122 also has openings 132, 133 and 134 formed in the side wall of front surface 123.

  FIG. 7 schematically shows the cross-sectional shape of the side surface of a battery pack formed by stacking the flat batteries 144A to 144D (142) of FIG. 6B. As shown in FIG. 7, the flat batteries 144A to 144D respectively include the power generation element 71, the sheathing material 73 for sealing the electricity generation element 71, and tabs (electrode terminals) 75 and 77 led to the outside from the sheathing material 73. Have. By disposing the hard magnetic sheet 79 containing the hard magnetic material outside the exterior material 73, the hard magnetic sheet 79 containing the hard magnetic material can be disposed between the flat type batteries 144A to 144D and in the outermost layer.

The power generation element 71 is formed by sequentially laminating a positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate has a positive electrode active material layer made of, for example, a lithium-transition metal complex oxide such as LiMn ₂ O ₄ . The negative electrode plate has, for example, a negative electrode active material layer. The separator is formed, for example, of porous PE (polyethylene) having air permeability which can permeate an electrolyte.
The exterior material 73 is a sheet such as a polymer-metal composite laminate film in which a metal (including an alloy) such as aluminum, stainless steel, nickel, or copper is covered with an insulator such as a polypropylene film from the viewpoint of weight reduction and thermal conductivity. It is made of a material, and part or all of the outer peripheral portion thereof is joined by heat fusion. As described above, the hard magnetic material may be formed by incorporating it as a core material in a laminate film which is an exterior material.

  The hard magnetic sheet 79 is a sheet of hard magnetic powder and binder resin, but is not limited thereto. When the hard magnetic sheet 79 is made of an adhesive sheet material, the battery case materials 73 can be adhered to each other. As long as the placement place of the hard magnetic body is the outside of the power generation element 71, it may be placed in the exterior material 73 or may be disposed on the inner surface of the exterior material 73. In addition, the form of the hard magnetic material may be any form such as the form of the hard magnetic material itself or the hard magnetic layer formed by applying the package material 73. Further, for example, when a rubber-like composition having elasticity is used as a binder to form a rubber-like elastic body, it is possible to relieve pressure and the like accompanying expansion and contraction of the battery. Furthermore, when the hard magnetic body has a thermal conductivity of 0.5 W / mk or more at 20 ° C., the heat in the battery is easily released, and the thermal deterioration of the battery can be prevented.

  In this embodiment, in a battery assembly incorporating a lithium ion secondary battery, the negative electrode active material of the incorporated lithium ion battery contains a ferromagnetic material, and the individual lithium ion batteries are provided between and at the outermost layer. Because the hard magnetic material is disposed, the negative electrode active material has a magnetic force. For this reason, even if Li ions are absorbed in the negative electrode active material and expanded and crushed during charging of the lithium ion secondary battery, the crushed negative electrode active material is not dissipated because it is aggregated by magnetic force. Therefore, it is possible to improve the durability of the assembled battery incorporating the lithium ion secondary battery.

Next, embodiments of the present invention will be described by way of examples. The following description shows the examples of the embodiment of the present invention, and the present invention is not limited by these examples.
Example 1
<Manufacture of negative electrode>
First, a Si alloy active material was manufactured by a mechanical alloy method. Specifically, using a planetary ball mill P-6 manufactured by Fritsch in Germany, the amount of each raw material powder of zirconia and the alloy is regulated to a predetermined atomic fraction and charged in a zirconia crushing pot. The alloy was alloyed at 600 rpm for 48 hours. The mass ratio of the silicon alloy active material A (Si ₈₀ Fe ₂₀ ) thus obtained, acetylene black as a conductive additive, and polyamic acid (Pyre-ML) as a binder is 90: 5: 5, respectively. The mixture was formulated as such, to which N-methylpyrrolidone was added as a solvent, and mixed to form a negative electrode slurry. A copper foil was used as a current collector, and each negative electrode slurry obtained above was applied and sufficiently dried. Then, it baked at 300 degreeC under vacuum for 24 hours, and obtained the target Si alloy negative electrode.

<Manufacture of positive electrode>
Li (Ni _0.33 Mn _0.33 Co _0.33 ) O ₂ is blended as a positive electrode active material, acetylene black as a conductive additive, and PVDF as a binder in a mass ratio of 94: 3: 3, to which N-methylpyrrolidone is added. As a solvent and mixed to form a positive electrode slurry. An aluminum foil was used as a current collector, the positive electrode slurry obtained above was applied, sufficiently dried, and dried under vacuum for 24 hours to obtain a positive electrode.
<Manufacture of battery>
The negative electrode and the positive electrode prepared above were made to face each other, the laminate of this negative electrode, separator and positive electrode was placed in an aluminum laminate cell, and 1M LiPF6 EC + DEC (1: 2) was injected into the cell as an electrolytic solution and sealed. , Obtained a lithium ion secondary battery.

<Measurement of capacity retention>
About the lithium ion secondary battery produced by the above method, charge and discharge cycle test is conducted in the state where the hard magnetic material sheet having magnetic flux density of 0.06 T (600 G) is arranged on one side of the laminate cell, and the discharge capacity retention is investigated did. That is, in a 30 ° C. atmosphere, using a charge-discharge tester SM-8 manufactured by Hokuto Denko, charge at a current density of 1 C and an upper limit voltage of 4.2 V by a constant current constant voltage charge system, and let rest for 1 minute The battery was discharged to 2.5 V at a current density of 1 C by a constant current discharge method. After repeating this charge and discharge cycle 100 times, the capacity retention was measured from the ratio of the discharge capacity at the 100th cycle to the discharge capacity at the first cycle.

(Example 2)
The test was conducted in the same manner as in Example 1 except that a hard magnetic sheet having a magnetic flux density of 0.08 T (800 G) was used as the hard magnetic sheet disposed on one side of the laminate cell.
(Example 3)
Other than using a Si alloy negative electrode active material B (Si ₈₀ Co ₂₀ ) as a negative electrode active material and using a hard magnetic material sheet having a magnetic flux density of 0.08 T (800 G) as a hard magnetic sheet disposed on one side of a laminate cell All of the tests were conducted in the same manner as in Example 1.
(Example 4)
Other than using a Si alloy negative electrode active material C (Si ₈₀ Ni ₂₀ ) as a negative electrode active material and using a hard magnetic material sheet having a magnetic flux density of 0.08 T (800 G) as a hard magnetic sheet disposed on one side of a laminate cell The tests were conducted under the same conditions as in Example 1.

(Comparative example 1)
The test was conducted in the same manner as Example 1 except that the hard magnetic sheet was not disposed on one side of the laminate cell.
(Comparative example 2)
The test was conducted in the same manner as Comparative Example 1 except that Si alloy negative electrode active material B (Si ₈₀ Co ₂₀ ) was used as the negative electrode active material.
(Comparative example 3)
The test was conducted in the same manner as Comparative Example 1 except that the Si alloy negative electrode active material C (Si ₈₀ Ni ₂₀ ) was used as the negative electrode active material.
(Comparative example 4)
The test was conducted in the same manner as Comparative Example 1 except that Si alloy negative electrode active material D (Si ₈₀ Al ₂₀ ) was used as the negative electrode active material.
(Comparative example 5)
Similar to Comparative Example 1 except that a Si alloy negative electrode active material D (Si ₈₀ Al ₂₀ ) was used as a negative electrode active material, and a hard magnetic material sheet having a magnetic flux density of 0.08 T (800 G) was disposed on one surface of the laminate cell. Tests were conducted according to the method.

(Reference Example 1)
The test was conducted in the same manner as in Comparative Example 1 except that graphite was used as a negative electrode active material of a lithium ion secondary battery, PVDF was used as a negative electrode binder, and the drying temperature under vacuum was 100 ° C.
(Reference Example 2)
Similar to Comparative Example 1 except that graphite was used as a negative electrode active material of lithium ion secondary battery, PVDF was used as a negative electrode binder, and a hard magnetic material sheet having a magnetic flux density of 0.08 T (800 G) was disposed on one side of a laminate cell. The test was performed by the method of

  The capacity retention rates after 100 cycles obtained in Examples 1 to 4 and Comparative Examples 1 to 4 and Reference Examples 1 and 2 are shown in Table 1. Further, Table 1 also shows the type of the negative electrode active material, the saturation magnetic flux density, and the magnetic flux density of the hard magnetic material.

  About the lithium ion secondary battery comprised from the Si alloy negative electrode containing iron which is a ferromagnetic, about the durability improvement effect by arrange | positioning the magnet sheet which is a hard magnetic body, Example 1, 2 and a comparative example By comparing 1 to 3, it is understood that the durability is improved and the capacity retention is improved by 20% or more by arranging the magnet sheet which is a hard magnetic body. For Comparative Examples 4 and 5, the effect of the presence or absence of the magnetic field on the durability of the LIB composed of the SiAl alloy negative electrode not containing the ferromagnetic material was confirmed, regardless of the presence or absence of the arrangement of the hard magnetic material. It did not improve.

  Moreover, about the battery comprised from a graphite negative electrode about the reference example 1 and 2, the magnetic field presence or absence confirmed the influence which it has on durability. In the case of a graphite negative electrode containing no ferromagnetic material, the magnetic field did not affect the durability. Although both have high capacity retention, when using only graphite, there is a problem in increasing the capacity of the battery, and since the volume expansion coefficient is originally low due to alloying with Li and the deterioration is small, the reference example And In the above embodiment, a Si alloy is used as the negative electrode active material, but the same effect can be expected even if an alloy or a compound of Sn or C and a ferromagnetic material (Fe, Ni, Co, etc.) is used.

  From the above results, it is possible to improve the durability by applying a magnetic field to the cell by including a ferromagnetic material in the negative electrode active material, and a battery composed of a silicon-based negative electrode active material having a problem of deterioration due to expansion and contraction. Was shown to be effective.

1 Power generation element 3 Core material (hard magnetic sheet)
DESCRIPTION OF SYMBOLS 5 negative electrode terminal plate 7 positive electrode terminal plate 9 exterior material 11 negative electrode 11a negative electrode collector 12 positive electrode 12a positive electrode collector 13 negative electrode active material 15 positive electrode active material 17 separator 19 cell layer 21 exterior body (laminated cell)
22 Hard magnetic sheet 31 current collector 32 negative electrode active material 33 conductive support agent 34 binder 40 cylindrical lithium ion secondary battery 41 power generation element 42 non-aqueous electrolyte solution 43 battery case (exterior material)
43a battery case (exterior material) inner surface 44 hard magnetic sheet 51 assembled battery 52 cylindrical battery entry hole 53 module structure 100 battery module 120 case 122 lower case 123 front surface 124 upper case 130 through hole 132 to 134 opening 140 cell unit 142 Laminated body 144 (144A to 144D) Flat type battery 160 (160A to 160E) Spacer (insulation plate)
164, 165 through hole 166, 167 output terminal 170 insulation cover 172 main body base 190 side portion

Claims (14)

A power generation element including a positive electrode, a negative electrode, a separator, and an electrolyte, and an outer package sealing the power generation element inside;
The power generation element is configured by stacking the positive electrode, the negative electrode, and the separator.
The negative electrode includes a negative active material having ferromagnetism, said hard magnetic material on the outside of the power generating element is arranged so magnetic field lines from the hard magnetic material is transmitted through the electrode film thickness direction of the power generating element Feature Lithium-ion rechargeable battery.   The lithium ion secondary battery according to claim 1, wherein the negative electrode active material has a coercive force of 1 μT or more obtained by a magnetization curve.   The said negative electrode active material contains 1 type selected from the group which consists of C, Si, and Sn, and 1 or more types selected from the group which consists of Fe, Co, and Ni. The lithium ion secondary battery as described in.   The lithium ion secondary battery according to any one of claims 1 to 3, wherein the shape of the lithium ion secondary battery is flat, cylindrical or rectangular.   The lithium ion secondary battery according to any one of claims 1 to 4, wherein the hard magnetic material has a magnetic flux density of 0.05 T or more. The hard magnetic material of the lithium ion secondary battery according to any one of claims 1 to 5, characterized in that contained in the outer body. The outer body, a sheet-like core including the hard magnetic material, a lithium ion secondary of claim 6, characterized in that it comprises a laminated film having a heat-sealable resin layer on one or both sides primary battery. The hard magnetic material, a lithium ion secondary battery according to any one of claims 1 to 5, characterized in that it is arranged on the upper and lower surface side of the outer body. The hard magnetic material, a lithium ion secondary battery according to any one of claims 1 to 5, characterized in that it is arranged on the side surface side of the outer body.   The lithium ion secondary battery according to any one of claims 1 to 5, wherein the hard magnetic material is disposed between the power generation elements.   A battery assembly comprising a plurality of lithium ion secondary batteries according to any one of claims 1 to 5 connected in parallel or in series with each other, wherein said hard magnetic material is formed between said plurality of lithium ion secondary batteries and / or said A battery assembly characterized in that it is disposed in the outermost layer of a plurality of lithium ion secondary batteries. The battery pack has a module structure having a plurality of spaces for receiving the plurality of lithium ion secondary batteries, the hard magnetic material of the plurality of spaces between and / or of the module structure top The assembled battery according to claim 11, which is disposed in the outer layer.   The assembled battery according to claim 12, wherein the plurality of lithium ion secondary batteries have a columnar shape, and the plurality of spaces are formed by columnar holes.   The plurality of lithium ion secondary batteries are flat batteries, and the assembled battery has a module structure in which the plurality of flat batteries are stacked and arranged in the thickness direction, and the hard magnetic material is between spaces of the module structure The battery assembly according to claim 11, wherein the battery assembly is disposed in the outermost layer.

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