JP6641113B2 - Lithium ion battery - Google Patents

Description

  The present invention relates to a stacked lithium ion battery having a unit cell stack structure in which at least two lithium secondary cells are stacked in series.

  2. Description of the Related Art Lithium ion (secondary) batteries have been widely used in various applications in recent years as small, lightweight secondary batteries with high capacity. In a general lithium ion battery, a positive electrode active material and a negative electrode active material are provided on one surface of a substantially flat current collector constituting a positive electrode and a negative electrode, and then heat treatment is performed to dry the positive electrode active material and the negative electrode active material. If necessary, a substantially flat lithium secondary cell is manufactured by laminating the positive electrode active material and the negative electrode active material with a separator interposed between the positive electrode active material and the negative electrode active material, if necessary. (See, for example, Patent Document 1).

JP 2003-17127 A

  In a lithium ion battery in which a plurality of unit cells are stacked, each unit cell is stacked in a state of being in close contact with each other, but when gas is generated in the unit cell due to aging or the like, the generated gas is a unit cell. May be led out of the unit cell through the current collector or the like, and may stop between adjacent unit cells. When this gas stops between adjacent unit cells, it is conceivable that the adhesion of the adjacent unit cells is hindered and battery performance is reduced.

  The present invention has been made in view of the above-described problems, and has a stacked structure in which gas generated in a single cell is led out of the single cell, and the performance of the cell is not deteriorated due to hindrance of adhesion between adjacent single cells. The purpose is to provide a lithium-ion battery.

INDUSTRIAL APPLICABILITY The present invention is applied to a stacked lithium ion battery having a unit cell stacked structure in which at least two lithium secondary cells are stacked in series. Then, at least two lithium secondary cells electrically connected to each other through an intermediate material having conductivity by providing a porous structure made of a porous material having conductivity in the unit cell stacked structure. Including the laminated structure, the intermediate material is formed in a substantially flat plate shape, and its end surface is exposed to the outside of the unit cell laminated structure, and the intermediate material is a positive electrode current collector and a negative electrode of the lithium secondary unit cell. It has a laminated surface with at least one of the current collectors , the positive electrode current collector and the negative electrode current collector are resin current collectors, and the void portion of this porous material is outward from the laminated surface to the unit cell laminated structure. By having a continuous pore structure that penetrates, at least one of the above-mentioned problems is solved.

  Accordingly, the gas generated in the battery cell reaches the intermediate material through the positive electrode or the negative electrode current collector, and is led out of the unit cell stacked structure because the intermediate material has a continuous pore structure.

  Here, in the present invention, a lithium secondary cell is a positive electrode in which a positive electrode composition layer containing a positive electrode active material and an electrolytic solution is formed on the surface of a positive electrode current collector, and a negative electrode active material and an electrolytic solution. A negative electrode having a negative electrode composition layer formed on the surface of a negative electrode current collector, the positive electrode composition and the negative electrode composition having a structure in which the negative electrode composition is laminated via a separator, a battery container, a terminal It is a battery that does not have an arrangement and an electronic control device (Reference: Japanese Industrial Standard JIS C8715-2 “Industrial lithium secondary battery cells and battery system”). Note that a lithium secondary battery may be abbreviated as a battery.

  Further, it is preferable that the unit cell is formed in a substantially flat plate shape. Note that forming a unit cell in a substantially flat plate shape means that, in a unit cell formed in a substantially flat plate shape, the upper surface and the lower surface thereof are a positive electrode current collector or a negative electrode current collector, respectively.

  Advantageous Effects of Invention According to the present invention, a gas generated in a single cell can be led out of the single cell, and a stacked lithium ion battery in which battery performance does not decrease due to hindrance of adhesion of an adjacent single cell is prevented. Can be provided.

1 is a cross-sectional view illustrating a lithium-ion battery according to one embodiment of the present invention. It is sectional drawing which expanded and showed only the principal part of the lithium ion battery of one Embodiment. It is a perspective view showing the lithium ion battery of one embodiment.

(One embodiment)
With reference to FIGS. 1 to 3, a lithium ion battery according to an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing a lithium-ion battery according to an embodiment of the present invention, FIG. 2 is an enlarged cross-sectional view showing only a main part of the lithium-ion battery according to one embodiment, and FIG. It is a perspective view which shows a lithium ion battery.

  In these figures, the lithium ion battery L of the present embodiment has a unit cell stacked structure in which a plurality of unit cells 1 each having a substantially flat outer shape are stacked in series in a hollow container 20 forming an outer shell of the lithium ion battery L. It is configured.

  As shown in detail in FIGS. 1 and 2, the unit cell 1 has a substantially plate-shaped positive electrode current collector 7 having a substantially plate-shaped positive electrode composition layer 5 containing a positive electrode active material and an electrolytic solution on the surface thereof. The formed positive electrode 2 and the negative electrode 3 in which a substantially flat negative electrode composition layer 6 including a negative electrode active material and an electrolytic solution is formed on the surface of a substantially flat negative electrode current collector 8, Similarly, they are laminated with a substantially flat separator 4 interposed therebetween, and are formed in a substantially flat plate shape as a whole. Thereby, the cell 1 having the opposed positive electrode current collector 7 and negative electrode current collector 8 in the outermost layer is configured.

  As best shown in FIG. 2, the positive electrode current collector 7 and the negative electrode current collector 8 are positioned so as to face each other at a predetermined interval by a sealing member 9 formed at an end of the unit cell 1. The end of the separator 4 is embedded in the sealing member 9 so that the separator 4 is supported and the positional relationship between the separator 4 and the positive electrode current collector 7 and the negative electrode current collector 8 is determined. I have.

  The distance between the positive electrode current collector 7 and the separator 4 and the distance between the negative electrode current collector 8 and the separator 4 are adjusted according to the capacity of the lithium ion battery. The positional relationship between the electric body 8 and the separator 4 is determined so that a necessary interval can be obtained.

  As shown best in FIG. 2, between each unit cell 1, more specifically, between the positive electrode current collector 7 and the negative electrode current collector 8 of the adjacent unit cell 1, A substantially flat intermediate member 10 is interposed so as to be in contact with the current collector 7 and the negative electrode current collector 8. The unit cells 1 and the intermediate members 10 are alternately stacked to form the lithium ion battery L of the present embodiment. However, as shown in FIG. 1, among the stacked unit cells 1, an intermediate material 10 is provided above the unit cell 1 located at the uppermost layer and below the unit cell 1 located at the lowermost layer in FIG. 1. Not placed.

  The intermediate material 10 includes a porous material having conductivity, so that at least a part thereof is formed in a porous structure. In addition, the intermediate material 10 is stacked from the surface of the positive electrode current collector 7 and the surface of the negative electrode current collector 8 of the adjacent single cell 1, It has a continuous pore structure that penetrates outward (single cell laminated structure).

  In addition, the end face 10a of the intermediate member 10 is exposed to the outside of the stacked unit cells 1 as best shown in FIG.

  Also, in FIG. 1, the upper surface of the unit cell 1 located at the uppermost layer, more specifically, in the illustrated example, the upper surface of the negative electrode current collector 8 and the lower surface of the unit cell 1 located at the lowermost layer, more specifically In the illustrated example, electrode terminals 11 and 12 are arranged on the lower surface of the positive electrode current collector 7 so as to be in contact with the positive electrode current collector 7 and the negative electrode current collector 8, respectively. 3, it is exposed outside the container 20.

The positive electrode active material includes positive electrode active material particles. Examples of the positive electrode active material particles include a composite oxide of lithium and a transition metal (eg, LiCoO ₂ , LiNiO ₂ , LiMnO _2, and LiMn ₂ O ₄ ), and a transition metal oxide. (Eg, MnO ₂ and V ₂ O ₅ ), transition metal sulfides (eg, MoS ₂ and TiS ₂ ) and conductive polymers (eg, polyaniline, polypyrrole, polythiophene, polyacetylene, poly-p-phenylene, and polycarbazole). No.

Further, the negative electrode active material is composed of negative electrode active material particles, and examples of the negative electrode active material particles include graphite, non-graphitizable carbon, amorphous carbon, and a fired polymer compound (for example, carbonized by firing a phenol resin, a furan resin, or the like). ), Coke (eg, pitch coke, needle coke, petroleum coke, etc.), carbon fiber, conductive polymer (eg, polyacetylene and polyquinoline, etc.), tin, silicon, and metal alloys (eg, lithium-tin alloy, lithium) - silicon alloy, a lithium - aluminum alloy and lithium - aluminum - manganese alloy), and a composite oxide of lithium and transition metals (e.g., Li ₄ Ti ₅ O _12, etc.) and the like.

  In the cell 1, the positive electrode and the negative electrode active material particles are preferably coated active material particles having at least a part of the surface coated with a coating agent containing a coating resin and a conductive additive.

  The coating agent contains a coating resin, and when the periphery of the positive electrode active material particles is coated with the coating agent, a change in volume of the electrode is reduced, and expansion of the electrode can be suppressed. Examples of the coating resin include vinyl resin, urethane resin, polyester resin, polyamide resin, epoxy resin, polyimide resin, silicone resin, phenol resin, melamine resin, urea resin, aniline resin, ionomer resin, and polycarbonate. Among them, vinyl resin, urethane resin, polyester resin and polyamide resin are preferable.

  The conductive assistant is selected from materials having conductivity.

  Specifically, metal [aluminum, stainless steel (SUS), silver, gold, copper, titanium, etc.], carbon [graphite and carbon black (acetylene black, Ketjen black, furnace black, channel black, thermal lamp black, single layer) Carbon nanotubes, multi-walled carbon nanotubes, etc.), and mixtures thereof, but are not limited thereto.

  These conductive assistants may be used alone or in combination of two or more. Further, these alloys or metal oxides may be used. From the viewpoint of electrical stability, preferably aluminum, stainless steel, carbon, silver, gold, copper, titanium and a mixture thereof, more preferably silver, gold, aluminum, stainless steel and carbon, more preferably carbon. is there. In addition, these conductive assistants may be those obtained by coating a conductive material (metal among the above-mentioned conductive assistant materials) around a particle-based ceramic material or a resin material by plating or the like.

  It is also possible to use conductive fibers as the conductive assistant. Examples of the conductive fiber include carbon fibers such as PAN-based carbon fiber and pitch-based carbon fiber, conductive fibers obtained by uniformly dispersing a highly conductive metal or graphite in synthetic fibers, and metals such as stainless steel. Examples include fibrous metal fibers, conductive fibers in which the surfaces of organic fibers are coated with a metal, and conductive fibers in which the surfaces of organic fibers are coated with a resin containing a conductive substance. Among these conductive fibers, carbon fibers are preferred.

  The coated active material particles are, for example, in a state where the active material particles are put in a universal mixer and stirred at 30 to 500 rpm, a resin solution containing the coating resin is dropped and mixed over 1 to 90 minutes, and the conductive auxiliary agent is further added. It can be obtained by mixing, heating to 50 to 200 ° C. with stirring, reducing the pressure to 0.007 to 0.04 MPa, and holding for 10 to 150 minutes.

  As the electrolyte, an electrolyte containing an electrolyte and a non-aqueous solvent, which is used for manufacturing a lithium ion battery, can be used.

As the electrolyte, those used in ordinary electrolytes and the like can be used. For example, lithium salts of inorganic acids such as LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ and LiClO ₄ , and LiN (CF ₃ SO ₂ ) ₂ , lithium salts of organic acids such as LiN (C ₂ F ₅ SO ₂ ) ₂ and LiC (CF ₃ SO ₂ ) ₃ . Among these, LiPF ₆ is preferable from the viewpoint of battery output and charge / discharge cycle characteristics.

  As the non-aqueous solvent, those used in ordinary electrolytic solutions and the like can be used. For example, lactone compounds, cyclic or chain carbonates, chain carboxylic esters, cyclic or chain ethers, phosphates, nitriles Compounds, amide compounds, sulfones, sulfolanes and the like and mixtures thereof can be used.

  One type of non-aqueous solvent may be used alone, or two or more types may be used in combination.

  Among the non-aqueous solvents, preferred from the viewpoint of battery output and charge / discharge cycle characteristics are lactone compounds, cyclic carbonates, chain carbonates and phosphates, and more preferred are lactone compounds, cyclic carbonates and chains. Carbonic acid ester is more preferable, and a mixed solution of cyclic carbonate and chain carbonate is more preferable. Particularly preferred is propylene carbonate (PC) or a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC).

  As the separator 4, polyethylene, polypropylene or the like, a polyolefin microporous membrane film, a multilayer film of a porous polyethylene film and polypropylene, a polyester fiber, an aramid fiber, a nonwoven fabric made of glass fiber, and the like, and silica on their surface, What adhere | attached the ceramic fine particles, such as alumina and titania, etc. are mentioned.

  As the positive and negative electrode current collectors 7 and 8, a metal current collector or a resin current collector can be used. As the metal current collector, a known metal current collector can be used. For example, the metal current collector is selected from the group consisting of copper, aluminum, titanium, nickel, tantalum, niobium, hafnium, zirconium, zinc, tungsten, bismuth, antimony, and alloys containing one or more of these, as well as stainless steel alloys. It is preferred that it be composed of at least one of The metal current collector may be formed from a thin plate or a metal foil, or a metal layer may be formed on the surface of the base material by a technique such as sputtering, electrodeposition, or coating.

  The polymer material constituting the resin current collector may be a conductive polymer or a polymer having no conductivity.

  Polymer materials include polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polycycloolefin (PCO), polyethylene terephthalate (PET), polyether nitrile (PEN), and polytetrafluoroethylene (PTFE). Styrene butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVdF), epoxy resin, silicone resin, or a mixture thereof.

  From the viewpoint of electrical stability, polyethylene (PE), polypropylene (PP), polymethylpentene (PMP) and polycycloolefin (PCO) are preferred, and polyethylene (PE), polypropylene (PP) and polymethylpentene are more preferred. (PMP).

  In addition, the resin current collector is used for improving the conductivity of the resin current collector containing a conductive polymer material, or imparting conductivity to a resin current collector containing a polymer material having no conductivity. It is preferable to include a conductive filler for the purpose of doing so. The conductive filler is selected from materials having conductivity. Preferably, from the viewpoint of suppressing ion permeation in the current collector, it is preferable to use a material having no conductivity with respect to ions used as the charge transfer medium. Specific examples include, but are not limited to, carbon materials, aluminum, gold, silver, copper, iron, platinum, chromium, tin, indium, antimony, titanium, nickel, and the like. These conductive fillers may be used alone or in combination of two or more. Further, these alloy materials such as stainless steel (SUS) may be used. From the viewpoint of corrosion resistance, aluminum, stainless steel, carbon material, nickel, and more preferably carbon material are preferable. In addition, these conductive fillers may be obtained by coating the above-mentioned metal with plating or the like around a particle-based ceramic material or a resin material.

  As a specific example of the resin current collector, a material obtained by dispersing 5 to 20 parts of acetylene black as a conductive filler in polypropylene and then rolling the same with a hot press machine is exemplified. In addition, the thickness is not particularly limited, and can be applied in the same manner as that of a known one or appropriately changed.

  The material constituting the sealing member 9 is not particularly limited as long as it has adhesiveness to the positive electrode and the negative electrode current collectors 7 and 8 and is durable to the electrolytic solution. Thermosetting resins are preferred. Specific examples include an epoxy resin, a polyolefin resin, a polyurethane resin, and a polyvinylidene fluoride resin. An epoxy resin is preferable because of its high durability and easy handling.

  As described above, as a material constituting the intermediate member 10, the intermediate member 10 includes a porous material having conductivity, and further includes lithium ion from the surface of the battery cell 1 on which the positive electrode or the negative electrode current collectors 7 and 8 are laminated. Since it has a continuous pore structure that penetrates outside the battery L, a porous metal film, a microporous film made of polyolefin such as polyethylene and polypropylene similar to the separator 4 described above, a porous polyethylene film and polypropylene And a nonwoven fabric made of polyester fiber, aramid fiber, glass fiber and the like.

  In addition, in order to impart conductivity to these films and sheets, the intermediate material 10 is made of a conductive material (metal among the materials of the above-mentioned conductive assistants) for the microporous film, the multilayer film, the nonwoven fabric and the like. Those coated with plating or the like, and those containing a conductive filler like the above-mentioned resin current collector are preferable. The conductive filler is selected from materials having conductivity. In addition, these conductive fillers may be obtained by coating the above-mentioned metal with plating or the like around a particle-based ceramic material or a resin material.

  Further, the material constituting the intermediate member 10 has a continuous pore structure penetrating from the stacked surface of the unit cell 1 with the positive electrode or the negative electrode current collectors 7 and 8 to the outside of the unit cell stacked structure. Techniques for forming pores in films and sheets of the above-described materials are well known, and various techniques can be arbitrarily selected.

  Any material can be suitably applied to the container 20 as long as the container 20 can accommodate the unit cell stacked structure. However, in consideration of the possibility that the cell 1 and the container 20 may come into contact with each other, the material forming the container 20 is preferably a material having an insulating property. In addition, from the viewpoint of maintaining the characteristics of the lithium ion battery L, it is preferable that the inside of the container 20 is sealed after degassing under reduced pressure. In this case, the material forming the container 20 is a material having airtightness. Is preferred. One example of such a material is a film called a laminate film, in which a metal foil is covered on both sides with a polymer film.

  The unit cell 1 having the above-described configuration includes a positive electrode composition 5 containing a positive electrode active material and an electrolytic solution, and a negative electrode active material and an electrolytic solution on the surfaces of the positive electrode current collector 7 and the negative electrode current collector 8, respectively. To form the positive electrode 2 and the negative electrode 3. The method for forming the positive electrode 2 and the negative electrode 3 is arbitrary, and the positive electrode current collector 7 and the negative electrode electrode composition 6 are applied to the surfaces of the positive electrode current collector 7 and the negative electrode current collector 8, respectively. And various methods such as placing the positive electrode composition 5 and the negative electrode composition 6 on the respective surfaces of the negative electrode current collector 8 via a nozzle or the like and then leveling them to a predetermined thickness with a spatula or the like. Is mentioned. Thereafter, the positive electrode 2 and the negative electrode 3 are stacked with the separator 4 interposed therebetween, and the ends of the positive electrode current collector 7 and the negative electrode current collector 8 and the end of the separator 4 are further sealed with a sealing member 9 to thereby form the battery cell 1. Can be manufactured.

  Next, the unit cells 1 and the intermediate members 10 manufactured by the above-described steps are alternately arranged such that the end surfaces 10a of the intermediate members 10 are exposed outward in a state where the unit cells 1 and the intermediate members 10 are stacked. After stacking and further arranging the electrode terminals 11 and 12 on the upper and lower surfaces of the stacked unit cells 1, these unit cell stacked structure and the electrode terminals 11 and 12 are housed in a container 20, and if necessary, By sealing the inside of the container 20 after degassing under reduced pressure, the lithium ion battery L of the present embodiment can be manufactured.

  Therefore, in the lithium ion battery L of the present embodiment, the unit cells 1 and the intermediate member 10 are alternately stacked so as to be exposed to the outside of the unit cell stacked structure with the end surfaces of the intermediate member 10 stacked. Therefore, the gas generated in the single cell 1 passes through the positive electrode or negative electrode current collectors 7 and 8 to reach the intermediate material 10, and since the intermediate material 10 has a pore structure, the It is derived outward. Thereby, it is possible to realize a lithium ion battery capable of guiding the gas generated in the unit cell 1 to the outside of the unit cell stacked structure.

  In the above-described embodiment, the unit cells 1 and the intermediate members 10 are alternately stacked. However, the number of the intermediate members 10 is determined in consideration of the probability of gas generation in the unit cells 1. And the like may be appropriately set, and an appropriate adjustment is possible, for example, by laminating one intermediate member 10 on a plurality of unit cells 1 laminated.

L Lithium ion battery 1 Single cell 2 Positive electrode 3 Negative electrode 4 Separator 5 Positive electrode composition 6 Negative electrode composition 7 Positive current collector 8 Negative current collector 9 Sealing member 10 Intermediate material 10a End faces 11, 12 Electrode terminal 20 Container

Claims (2)

A stacked lithium-ion battery having a unit cell stack structure in which at least two lithium secondary cells are stacked in series,
Including a structure in which at least two of the lithium secondary cells electrically connected to each other via an intermediate material having conductivity by being provided with a porous structure made of a porous material having conductivity are stacked,
The intermediate member is formed in a substantially flat plate shape, and an end surface thereof is exposed to the outside of the unit cell stacked structure,
The intermediate material has a laminated surface with at least one of a positive electrode current collector and a negative electrode current collector of the lithium secondary battery,
The positive electrode current collector and the negative electrode current collector are a resin current collector,
A lithium ion battery, wherein the void portion of the porous material has a continuous pore structure penetrating from the lamination surface to the outside of the unit cell laminated structure. The lithium ion battery according to claim 1,
The cell is formed in a substantially flat plate shape.

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