JP5919908B2 - Flat laminated battery - Google Patents

Description

  The present invention relates to a flat plate type battery.

  In recent years, the development of electric vehicles (EV), hybrid electric vehicles (HEV), and fuel cell vehicles (FCV) has been promoted against the background of the increasing environmental protection movement. A secondary battery that can be repeatedly charged and discharged is suitable as a power source for driving these motors, and a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery that can be expected to have a high capacity and a high output is attracting attention.

The nonaqueous electrolyte secondary battery has a positive electrode active material layer containing a positive electrode active material (for example, LiCoO ₂ , LiMnO ₂ , LiNiO _2, etc.) formed on the current collector surface. In addition, the non-aqueous electrolyte secondary battery includes a negative electrode active material (for example, carbonaceous material such as metallic lithium, coke and natural / artificial graphite, Sn, A negative electrode active material layer including a metal such as Si or an oxide material thereof. Furthermore, the nonaqueous electrolyte secondary battery includes an electrolyte layer that is provided between the positive electrode active material layer and the negative electrode active material layer and includes an electrolyte that separates the positive electrode active material layer and the negative electrode active material layer. Yes.

  Such non-aqueous electrolyte secondary batteries are known to become unsafe as capacity increases, and this safety issue is particularly important when seeking high-capacity batteries for use in automobiles and the like. It is. In order to ensure safety, solutions from various angles, such as control methods, active materials to be used, electrolytes, and additives, have been taken. One of them is a method in which a cell (single cell) structure is formed into a flat plate and is made into a laminate type (stacked type). The laminate type has much higher heat dissipation than the wound type, so it can suppress deterioration due to battery temperature rise, and the battery exterior can be made into a flexible laminate material. Energy can be dissipated in stages, and battery deterioration can be reliably suppressed.

  As a prior art in which the secondary battery is configured in a flat plate type, for example, Patent Document 1 below can be cited.

JP 2004-241328 A

  However, since the flat stacked battery is a stacked type, the maximum pressing pressure is atmospheric pressure, so the sensitivity to influence on cell performance due to in-plane variation and swelling is higher, and the output characteristics and life are reduced. There was a problem. In particular, assuming an application for mounting on automobiles, it is necessary to obtain high output for motor driving, etc., and a large number of flat-type secondary batteries are stacked, or a large number of flat-plate stacked batteries are used in the same direction. Is required. On the other hand, it is known that a negative electrode material of a non-aqueous electrolytic secondary battery such as a lithium ion secondary battery expands and contracts due to charging and discharging, and slightly expands. If individual cells swell slightly due to charging / discharging, there is a risk that the entire battery mounted on the vehicle will be greatly deformed. Therefore, a technique for suppressing expansion and contraction is also required for the negative electrode constituting each cell. This is because it is considered that the suppression of swelling realized by individual cells can effectively prevent deformation of the entire battery mounted on the vehicle.

  This invention is made | formed in view of the said situation, and it aims at providing the means which can suppress the cell swelling accompanying the expansion / contraction of the negative electrode at the time of charging / discharging in a flat laminated battery.

  A flat plate type battery according to the present invention is a flat plate type battery having a positive electrode, a negative electrode, and an electrolyte layer interposed between the positive electrode and the negative electrode, wherein the negative electrode contains carbon powder as a negative electrode active material. The ratio I110 / I004 of the peak intensity (I110) of the (110) plane and the peak intensity (I110) of the (004) plane of the graphite crystal obtained by XRD measurement of the carbon powder is 0.6 or more It has the characteristics.

  According to the flat laminate type battery of the present invention, since the expansion and contraction of the negative electrode during charging / discharging of the battery can be suppressed, cell swelling can be suppressed. As a result, the deformation of the whole battery of the flat plate type battery is effectively prevented.

1 is a schematic cross-sectional view schematically showing the entire structure of a bipolar lithium ion secondary battery (bipolar battery). It is the cross-sectional schematic which represented typically the whole structure of the laminated lithium ion secondary battery (stacked battery) which is not a bipolar type.

  Embodiments of the present invention will be described below. However, the present invention is not limited to the following embodiments.

[Flat plate battery]
One embodiment of the present invention is a flat plate type battery having a positive electrode, a negative electrode, and an electrolyte layer interposed between the positive electrode and the negative electrode, preferably a flat plate type lithium ion secondary battery. is there. The structure and form of the lithium ion secondary battery are not particularly limited, such as a bipolar stacked battery or a non-bipolar stacked battery, and can be applied to any conventionally known structure. Hereinafter, the structure of the lithium ion secondary battery according to the embodiment of the present invention will be described.

  FIG. 1 is a schematic cross-sectional view schematically showing the entire structure of a bipolar lithium ion secondary battery (bipolar battery).

  The bipolar battery 10 of this embodiment shown in FIG. 1 has a structure in which a substantially rectangular power generating element 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate sheet 29 that is a battery exterior material. Specifically, the power generation element 21 is housed and sealed by using a polymer-metal composite laminate sheet as the battery exterior and joining all of its peripheral parts by thermal fusion.

  As shown in FIG. 1, the power generating element 21 of the bipolar battery 10 according to the present embodiment includes a positive electrode active material layer 13 that is electrically coupled to one surface of the current collector 11. A plurality of bipolar electrodes having a negative electrode active material layer 15 electrically coupled to the opposite surface is provided. Each bipolar electrode is stacked via the electrolyte layer 17 to form the power generation element 21. The electrolyte layer 17 has a configuration in which an electrolyte is held at the center in the surface direction of a separator as a base material. At this time, each bipolar type is formed such that the positive electrode active material layer 13 of one bipolar electrode and the negative electrode active material layer 15 of another bipolar electrode adjacent to the one bipolar electrode face each other through the electrolyte layer 17. Electrodes and electrolyte layers 17 are alternately stacked. That is, the electrolyte layer 17 is disposed between the positive electrode active material layer 13 of one bipolar electrode and the negative electrode active material layer 15 of another bipolar electrode adjacent to the one bipolar electrode.

  The adjacent positive electrode active material layer 13, electrolyte layer 17, and negative electrode active material layer 15 constitute one unit cell layer 19. Therefore, it can be said that the bipolar battery 10 has a configuration in which the single battery layers 19 are stacked. Further, for the purpose of preventing liquid junction due to leakage of the electrolytic solution from the electrolyte layer 17, a seal portion 31 is disposed on the outer peripheral portion of the unit cell layer 19. By providing the seal portion 31, it is possible to insulate between the adjacent current collectors 11 and prevent a short circuit due to contact between adjacent electrodes. A positive electrode active material layer 13 is formed only on one side of the positive electrode outermost layer current collector 11 a located in the outermost layer of the power generation element 21. The negative electrode active material layer 15 is formed only on one surface of the outermost current collector 11b on the negative electrode side located in the outermost layer of the power generation element 21. However, the positive electrode active material layer 13 may be formed on both surfaces of the outermost layer current collector 11a on the positive electrode side. Similarly, the negative electrode active material layer 13 may be formed on both surfaces of the outermost layer current collector 11b on the negative electrode side.

  Further, in the bipolar battery 10 shown in FIG. 1, a positive electrode current collector plate 25 is disposed so as to be adjacent to the positive electrode side outermost layer current collector 11a, which is extended and led out from a laminate sheet 29 which is a battery exterior material. Yes. On the other hand, the negative electrode current collector plate 27 is disposed so as to be adjacent to the negative electrode side outermost layer current collector 11b, which is similarly extended and led out from the laminate sheet 29 which is an exterior of the battery.

  FIG. 2 is a schematic cross-sectional view schematically showing the overall structure of a stacked lithium ion secondary battery (stacked battery) that is not bipolar.

  As shown in FIG. 2, the lithium ion secondary battery 10 ′ of the present embodiment has a structure in which a substantially rectangular power generation element 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate sheet 29 that is an exterior. Have

  The power generation element 21 includes a positive electrode in which the positive electrode active material layer 13 is disposed on both surfaces of the positive electrode current collector 11, an electrolyte layer 17, and a negative electrode in which the negative electrode active material layer 15 is disposed on both surfaces of the negative electrode current collector 12. It has a stacked configuration. Specifically, the positive electrode, the electrolyte layer, and the negative electrode are laminated in this order so that one positive electrode active material layer 13 and the negative electrode active material layer 15 adjacent thereto face each other with the electrolyte layer 17 therebetween. .

  Thereby, the adjacent positive electrode, electrolyte layer, and negative electrode constitute one unit cell layer 19. Therefore, it can be said that the lithium ion battery 10 of the present embodiment has a configuration in which a plurality of single battery layers 19 are stacked and electrically connected in parallel. The positive electrode active material layer 12 is disposed only on one side of the outermost positive electrode current collector located in both outermost layers of the power generation element 21. 2, the arrangement of the positive electrode and the negative electrode is reversed so that the outermost negative electrode current collector is positioned in both outermost layers of the power generation element 21, and the negative electrode is disposed only on one side of the outermost layer negative electrode current collector. An active material layer may be arranged.

  The positive electrode current collector 11 and the negative electrode current collector 12 are respectively attached with a positive electrode current collector plate 25 and a negative electrode current collector plate 27 that are electrically connected to the respective electrodes (positive electrode and negative electrode). These current collector plates (25, 27) are led out of the laminate sheet 29 so as to be sandwiched between the end portions of the laminate sheet 29, respectively. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 are ultrasonically welded to the positive electrode current collector 11 and the negative electrode current collector 12 of each electrode, respectively, via a positive electrode lead and a negative electrode lead (not shown) as necessary. Or resistance welding or the like.

  The flat plate type battery of this embodiment is suitable for automobile loading, and in order to obtain high output for driving a motor, a large number of flat plate surfaces are stacked on each other, both bipolar and non-bipolar types. Can be loaded and used side by side. For example, the flat laminated battery of the present embodiment can be used by stacking preferably 10 or more, more preferably 50 or more, still more preferably 100 or more, and most preferably 200 or more. As will be described later, since the negative electrode electrode can suppress swelling when the negative electrode expands and contracts, the flat-plate laminated battery of this embodiment can suppress cell swelling of individual batteries. Deformation can be suppressed. The effect of such slight cell bulging becomes more conspicuous as the number of battery stacks increases. If the flat battery stack of the present embodiment is used, 200 or more stacks are suitable for mounting on automobiles.

  Hereinafter, although the component which comprises the battery mentioned above is demonstrated, it is not limited only to the following form.

[Current collector]
The current collector 11 (the positive electrode current collector 11 and the negative electrode current collector 12) is a member for electrically connecting the positive electrode or negative electrode active material layers 13 and 15 and the outside, and is made of a conductive material. Is done. There is no restriction | limiting in particular about the specific form of an electrical power collector. As long as it has electroconductivity, the material, structure, etc. are not specifically limited, The conventionally well-known form used for the general lithium ion battery can be employ | adopted. As a constituent material of the current collector 2, for example, a conductive metal such as copper, nickel, silver, or SUS is used, and copper is particularly preferable. The structure of the current collector can also be a porous shape, a foil shape, a nonwoven fabric shape, a porous shape, or the like. In some cases, a current collector in which two or more metal foils are bonded together may be used. The thickness of the current collector is not particularly limited, and may be about 5 to 50 μm. The magnitude | size of an electrical power collector is determined according to a use as a flat laminated battery suitable for vehicle mounting.

[Negative electrode active material layer]
The negative electrode active material layer 15 contains a negative electrode active material, and in order to increase the ionic conductivity, a conductive material, a binder, an electrolyte (polymer matrix, ion conductive polymer, electrolytic solution, etc.) for increasing electrical conductivity as necessary. The electrolyte support salt (lithium salt) may be further included.

  The compounding ratio of the components contained in the negative electrode active material layer 15 is not particularly limited, and can be adjusted by appropriately referring to known knowledge about the lithium ion secondary battery. Moreover, there is no restriction | limiting in particular also about the thickness of an active material layer, The conventionally well-known knowledge about a lithium ion secondary battery can be referred suitably. For example, the thickness of the negative electrode active material layer 15 is about 2 to 100 μm.

(Negative electrode active material)
In this embodiment, the negative electrode active material has a ratio I110 / I004 of the peak intensity (I110) of the (110) plane and the peak intensity (I110) of the (004) plane of graphite crystals obtained by XRD measurement of 0.6 or more. Contains some carbon powder.

  The ratio I110 / I004 reflects the orientation of the graphite crystal. The larger the value of I110 / I004, the lower the orientation, and the smaller the value, the higher the orientation. When graphite crystals are used for the negative electrode of a lithium ion secondary battery, expansion occurs when lithium ions enter between the particles of the carbon powder during charging, and contraction occurs when lithium ions are released during discharging. It is considered that the phenomenon of cell swelling occurs due to such expansion and contraction of the carbon powder in the negative electrode. At that time, if the orientation of the carbon powder is higher, the expansion and contraction of the carbon grains occur in one direction because they occur on the uniform crystal plane, and the degree of swelling of the entire cell increases. However, if the orientation is lower, the expansion and contraction of the carbon grains becomes isotropic, and the cell expansion is reduced as a whole. Therefore, in the present embodiment, carbon powder having I110 / I004 of 0.6 or more and 1.4 or less is used for the negative electrode. If I110 / I004 is within this range, cell swelling can be effectively prevented even when the battery is repeatedly charged and discharged, and the invention can be applied to a flat-plate laminated battery for mounting on automobiles. The ratio of I110 / I004 is more preferably 1.0 to 1.4. XRD measurement (X-ray diffraction measurement) can be performed by the method described in the examples described later.

  The content of the negative electrode active material with respect to the total amount of 100% by mass of the negative electrode active material layer 15 is usually about 40 to 100% by mass, preferably 50 to 90% by mass, more preferably 70 to 90% by mass, Most preferably, it is 75-85 mass%.

  Although there is no restriction | limiting in particular in order to obtain the carbon powder whose ratio of I110 / I004 is 0.6 or more, For example, it can manufacture by the following methods. That is, a carbon material having a high crystallinity and a constant particle size is uniformly impregnated with a certain amount of carbon material and combined, and then the carbon material is carbonized at a high temperature. Thereby, it is possible to produce a carbon powder having a substantially uniform structure from the surface of the particle to the central portion, having little deformation / orientation due to pressurization, and having the ratio of I110 / I004.

  Preferably, it is produced by a step of attaching and / or penetrating an organic compound or a solution thereof as a carbon material to carbonaceous particles as a core material, and a step of carbonizing and / or graphitizing the organic compound. Moreover, it is also preferable to perform by the process which adheres and / or osmose | permeates an organic compound or its solution to the carbonaceous particle used as a nucleus, the process of heat-processing the said organic compound, and the process of carbonizing and / or graphitizing. This is because the organic compound adheres to the carbonaceous particles by polymerization or the like by heat-treating the organic compound after adhering and / or infiltrating the organic compound or a solution thereof and before the carbonization and / or graphitization step.

  The carbonaceous particles serve as a core material of carbon powder as the negative electrode active material, but the type thereof is not particularly limited as long as lithium ions can be inserted and released. The lithium ion insertion / release amount is preferably as large as possible. From such a viewpoint, highly crystalline graphite such as natural graphite is preferable. Further, as the carbonaceous particles, particles made of a graphitizable carbon material (soft carbon) that is graphitized by a heat treatment at 1800 to 3300 ° C. in a subsequent step can also be used. Specific examples include particles made of coke such as petroleum pitch coke and coal pitch coke. The shape of the carbonaceous particles preferably used as the core material may be a lump shape, a scale shape, a sphere shape, a fiber shape, or the like, preferably a sphere shape or a lump shape.

  Next, the carbon material is combined with the carbonaceous particles as the core material. The carbon material is not particularly limited, and examples thereof include pitch heat-treated products, coke, and organic compound heat-treated products. Moreover, it is preferable that the organic compound which adheres and / or penetrates into the core material particles as the composite carbon material is a polymer having adhesiveness to the core material particles. For example, the polymer is preferably at least one selected from the group consisting of phenol resin, polyvinyl alcohol resin, furan resin, cellulose resin, polystyrene resin, polyimide resin, and epoxy resin. Preferably, a phenol resin and a polyvinyl alcohol resin are used.

  In addition, as an organic compound that adheres and / or permeates into the carbonaceous particles as the core material, a polymer raw material is also preferable. This is because the raw material has a lower molecular weight / lower viscosity and penetrates uniformly into the carbonaceous particles. As described above, the polymer is preferably a phenol resin, and therefore, the polymer material is preferably a phenol resin material such as formalin or a phenol derivative. The organic compound is preferably used as a solution because it has a low viscosity and penetrates uniformly into the core carbonaceous particles.

  The composite amount of the carbon material is not particularly limited, but is preferably 2 to 200 parts by mass, more preferably 4 to 100 parts by mass, and particularly preferably 10 to 25 parts by mass with respect to 100 parts by mass of the carbonaceous particles of the core material. is there.

  The composite of the polymer raw material and the carbonaceous particles of the core material is preferably performed by reacting the raw material while mixing with the core material particles in the presence of a catalyst. The polymerization temperature can be carried out at 100 to 500 ° C.

  Since the graphite powder that can be used as the core material has already high crystallinity, heat treatment at a high temperature is not particularly necessary, but a certain amount of heat treatment is necessary to develop the crystallinity of the composite carbon layer. A specific heat treatment temperature is 1800 to 3300 ° C, preferably 2300 ° C or higher, more preferably 2500 ° C or higher, further preferably 2800 ° C or higher, and most preferably 3000 ° C or higher.

The carbon powder that can be used for the negative electrode active material is a core material made of graphite having an interlayer distance (d value) of d (002) plane of 0.3350 nm or more and 0.3380 nm or less, and 1580 cm ⁻¹ in an argon ion laser Raman spectrum. A multi-layer structure carbonaceous powder comprising a surface layer made of graphite having an R value which is a peak intensity ratio of 1360 cm ^{−1 to} a peak intensity of 0.1 to 0.30, more preferably 0.1 to 0.25. It is preferable that Such a carbon powder having a multi-layer structure is suitable for obtaining a carbon powder having an I110 / I004 ratio of 0.6 or more as described above, and the effect of the present invention for suppressing cell swelling is reliably obtained. Therefore, it is preferable.

  The carbon powder preferably has a particle size distribution measurement by a laser diffraction scattering method in which 90% or more of all particles are in the range of 5 to 50 μm. When the particle size distribution is within this range, the effect of improving the cycle characteristics of the flat plate type secondary battery can be obtained more reliably. For the particle size distribution, a particle size distribution measured by a laser diffraction / scattering particle size distribution measuring apparatus is used. The particle size distribution can be measured, for example, using a Microtrac particle size distribution measuring device (model HRA9320-X100) manufactured by Nikkiso Co., Ltd.

Moreover, it is preferable that the BET specific surface area of the said carbon powder is 0.5-30 m < ² > / g, More preferably, it is 15-25. If the BET specific surface area is within this range, the effect of improving the cycle characteristics of the flat plate type secondary battery can be obtained more reliably. The BET specific surface area can be measured by a nitrogen adsorption method.

In addition to the carbon powder having a specific ratio of I110 / I004, a conventionally known negative electrode active material may be mixed and used. For example, a metal material such as lithium metal, a lithium-transition metal composite oxide such as lithium-titanium composite oxide (lithium titanate: Li ₄ Ti ₅ O ₁₂ ), and other conventionally known negative electrode active materials can be used. is there.

(Conductive aid)
The conductive assistant is blended for the purpose of improving the conductivity of the negative electrode active material layer 3. The conductive auxiliary agent that can be used in the present embodiment is not particularly limited, and conventionally known forms can be appropriately referred to. Examples thereof include carbon blacks such as acetylene black, furnace black, channel black, and thermal black; carbon fibers such as vapor grown carbon fiber (VGCF); and carbon materials such as graphite. When the active material layer includes a conductive material, an electronic network inside the active material layer is effectively formed, which can contribute to improvement of output characteristics of the battery including the negative electrode of the present embodiment.

  The content of the conductive additive with respect to 100% by mass of the total amount of the negative electrode active material layer 3 is usually about 0 to 30% by mass, preferably 1 to 10% by mass, and more preferably 3 to 7% by mass.

(Binder)
Examples of the binder include, but are not limited to, polyvinylidene fluoride (PVDF), carboxymethylcellulose (CMC), polytetrafluoroethylene (PTFE), polyvinyl acetate, and acrylic resin (for example, liquid silicone rubber (LSR)). ), Thermosetting resins such as polyimide, epoxy resin, polyurethane resin, and urea resin, and rubber-based materials such as styrene-butadiene rubber (SBR).

  The content of the binder with respect to the total amount of 100% by mass of the negative electrode active material layer 3 is usually about 0 to 50% by mass, preferably 5 to 45% by mass, more preferably 10 to 25% by mass, and particularly preferably. Is 15 to 20% by mass.

(Electrolyte / Supporting salt)
Examples of the electrolyte include, but are not limited to, ion conductive polymers (solid polymer electrolytes) including lithium salts such as polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. There is nothing.

The supporting salt (lithium salt), but are not limited _{to, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, inorganic acid anion salts such as _{Li 2 B 10 Cl 10; LiCF} 3 SO ₃ , organic acid anion salts such as Li (CF ₃ SO ₂ ) ₂ N and Li (C ₂ F ₅ SO ₂ ) ₂ N. These supporting salts may be used alone or in combination of two or more.

[Positive electrode (positive electrode active material layer)]
The positive electrode active material layer 13 includes a positive electrode active material, and may include other additives as necessary. Among the constituent elements of the positive electrode active material layer 13, except for the positive electrode active material, the same form as described above for the negative electrode active material layer 15 can be adopted, and thus the description thereof is omitted here. The compounding ratio of the components contained in the positive electrode active material layer 13 and the thickness of the positive electrode active material layer are not particularly limited, and conventionally known knowledge about the lithium ion secondary battery can be appropriately referred to.

(Positive electrode active material layer)
The positive electrode active material layer 13 preferably contains a manganese-containing positive electrode active material. The positive electrode active material layer may further include additives such as a positive electrode active material other than the manganese-containing positive electrode active material, a conductive additive, and a binder.

Manganese-containing positive electrode active material The manganese-containing positive electrode active material has a composition capable of releasing lithium ions during charging and occluding lithium ions during discharging. The manganese-containing positive electrode active material has a manganese elution amount of 0.04% by mass or less, preferably 0.035% by mass or less, and more preferably 0.001 to 0.03% by mass. Since manganese is relatively abundant as a resource, the manganese-containing positive electrode active material has the advantages that the raw materials are inexpensive and easily available, and the burden on the environment is small. Therefore, it can be said that the manganese-containing positive electrode active material is a suitable material as the positive electrode active material.

  The manganese-containing positive electrode active material is not particularly limited as long as it contains manganese and has a manganese elution amount of 0.04% by mass or less, and examples thereof include lithium-manganese composite oxide (lithium manganate). A part of manganese in the lithium-manganese composite oxide contains other metal elements (Ni, Co, Fe, Al, Mg, B, Ga, In, Si, Zr, Nb, Mo, Y, Sn, Ti, V , Cr, Cu, Ag, Zn, etc.). For example, the manganese-containing positive electrode active material of this embodiment may be a lithium-manganese composite oxide having a composition formula represented by the following chemical formula 1.

  Wherein M is selected from the group consisting of Ni, Co, Fe, Al, Mg, B, Ga, In, Si, Zr, Nb, Mo, Y, Sn, Ti, V, Cr, Cu, Ag, Zn. Represents one or more elements. From the viewpoint of further improving the performance of the positive electrode active material, M is at least one element selected from the group consisting of Ni, Co, Fe, Al, Mg, Ga, Sn, Ti, V, and Cr. It is preferable. Further, x is preferably −0.1 <x <0.1, and more preferably 0.01 <x <0.06. Furthermore, y is preferably 0 ≦ y <1. Further, z is preferably 0 ≦ z <0.2, and more preferably 0 ≦ z <0.2.

The specific surface area of the manganese-containing positive electrode active material is preferably 0.2~0.6m ² / g, more preferably 0.25~0.5m ² / g. A specific surface area of 0.2 m ² / g or more is preferable because sufficient battery output can be obtained. On the other hand, it is preferable that the specific surface area is 0.6 m ² / g or less because elution of manganese can be suppressed. In addition, in this specification, the value measured by the method of an Example shall be employ | adopted as the value of a specific surface area unless there is particular notice.

  As an average particle diameter of a manganese containing positive electrode active material, it is preferable that it is 10-20 micrometers, and it is more preferable that it is 12-18 micrometers. It is preferable that the average particle size is 10 μm or more because elution of manganese can be suppressed. On the other hand, when the average particle size is 20 μm or less, it is preferable that foil breakage, clogging, and the like can be suppressed in the application step to the current collector during the production of the positive electrode. In addition, in this specification, the value measured by the method of an Example shall be employ | adopted as the value of an average particle diameter unless there is particular notice.

The said manganese containing positive electrode active material may use what was prepared by itself, and may use a commercial item. When the manganese-containing positive electrode active material is prepared by itself, the manganese-containing positive electrode active material includes manganese compounds (Mn ₂ O ₃ , MnO ₂ , Mn ₃ O ₄ , MnSO ₄ , MnCO ₃ , Mn (NO ₃ ) ₂ , ( CH ₃ COO) ₂ Mn, etc.) and a lithium compound (Li ₂ CO ₃ , Li (OH), LiNO ₃ , CH ₃ COOLi, Li ₂ O, etc.) are mixed at a predetermined ratio and fired at 700 to 1000 ° C. Can be prepared. At this time, in order to set the manganese elution amount to 0.04 mass% or less, methods for suppressing elution of manganese can be appropriately combined. As a method for suppressing elution of manganese, for example, a method for controlling firing conditions (firing temperature, multistage firing), a different element (Ni, Co, Fe, Al, Mg, B, Ga, In, Si, Zr, Method of adding Nb, Mo, Y, Sn, Ti, V, Cr, Cu, Ag, Zn, etc., surface treatment of manganese-containing positive electrode active material (titanium monoxide, tin monoxide, vanadium monoxide, niobium monoxide) , Coating method with molybdenum dioxide, tungsten dioxide, etc., additives (sintering aids such as boron oxide, boric acid, lithium borate, ammonium borate; ammonium dihydrogen phosphate, lithium phosphate, calcium phosphate, phosphoric acid A method of mixing crystal surface growth inhibitors such as trisodium, sodium dihydrogen phosphate, aluminum hydroxide, aluminum chloride, and aluminum sulfate). It is. These methods may be applied in combination of two or more.

  The elution of manganese is considered to occur when the positive electrode active material reacts with an electrolyte component such as hydrofluoric acid. High crystallization of the crystal structure of the manganese-containing positive electrode active material by the above method; reduction of the contact area with the electrolyte by controlling the properties (average particle size, specific surface area, lattice constant, etc.) of the manganese-containing positive electrode active material; It is possible to prevent contact between the manganese-containing positive electrode active material and the electrolytic solution. As a result, elution of manganese can be suppressed.

  Manganese (manganese ions) eluted in the electrolytic solution is considered to move to the negative electrode, be reduced and deposited at the negative electrode, and then react with the electrolytic solution to form a complex with an organic substance. The single battery layer can be expanded by manganese deposited on the negative electrode, a manganese-organic composite formed on the negative electrode, or the like. In the present invention, the use of a manganese-containing positive electrode active material having an elution amount of manganese of 0.04% by mass or less can suppress the expansion of the single cell layer. Therefore, the flat plate laminated battery in which the single cell layers are laminated is excellent. Battery performance. Therefore, the flat laminated battery according to the present invention can suppress deterioration of battery performance based on the expansion of the single cell layer while realizing high output and high capacity, and is preferably applied to an electric vehicle. Can do.

Positive electrode active material other than manganese-containing positive electrode active material The positive electrode active material other than manganese-containing positive electrode active material is not particularly limited. For example, lithium-nickel composite oxide (LiNiO ₂ etc.), lithium-cobalt composite oxide (LiCoO) ₂ ), lithium-iron composite oxide (LiFeO ₂ etc.), lithium-nickel-cobalt composite oxide (LiNi _0.8 Co _0.2 O ₂ etc.), lithium-transition metal phosphate compound (LiFePO ₄ etc.) , And lithium-transition metal sulfate compounds (Li _x Fe ₂ (SO ₄ ) ₃ ) and the like.

The specific surface area of the positive electrode active material other than the manganese-containing positive electrode active material is not particularly limited, is preferably from 0.1~30m ² / g, more preferably 0.2~20m ² / g. A specific surface area within the above range is preferable because sufficient output can be obtained.

  The average particle size of the positive electrode active material other than the manganese-containing positive electrode active material is not particularly limited, but is preferably 1 to 100 μm from the viewpoint of increasing the capacity of the positive electrode active material, reactivity, and cycle durability. More preferably, it is 20 μm. When the average particle size is in the above range, an increase in the internal resistance of the battery during charging / discharging under high output conditions is suppressed, and a sufficient current can be taken out.

[Electrolyte layer]
The electrolyte layer 17 functions as a spatial partition (spacer) between the positive electrode active material layer and the negative electrode active material layer. In addition, it also has a function of holding an electrolyte that is a lithium ion transfer medium between the positive and negative electrodes during charging and discharging.

  There is no restriction | limiting in particular in the electrolyte which comprises an electrolyte layer, Polymer electrolytes, such as a liquid electrolyte and a polymer gel electrolyte and a polymer solid electrolyte, can be used suitably.

The liquid electrolyte has a form in which a lithium salt as a supporting salt is dissolved in an organic solvent as a plasticizer. Examples of the organic solvent used as the plasticizer include carbonates such as ethylene carbonate (EC), diethyl carbonate, and propylene carbonate (PC). As the supporting salt (lithium _{salt), LiN (SO 2 C 2} F 5) 2, LiN (SO 2 CF 3) 2, LiPF 6, LiBF 4, LiClO 4, electrodes such as LiAsF 6, LiSO ₃ CF ₃ A compound that can be added to the active material layer can be similarly used.

  On the other hand, the polymer electrolyte is classified into a gel electrolyte containing an electrolytic solution and a polymer solid electrolyte containing no electrolytic solution.

  The gel electrolyte has a configuration in which the above liquid electrolyte is injected into a matrix polymer having lithium ion conductivity. Examples of the matrix polymer having lithium ion conductivity include polyethylene oxide (PEO), polypropylene oxide (PPO), and copolymers thereof. In such a matrix polymer, an electrolyte salt such as a lithium salt can be well dissolved.

  In addition, when an electrolyte layer is comprised from a liquid electrolyte or a gel electrolyte, you may use a separator for an electrolyte layer. Specific examples of the separator include a microporous film made of a polyolefin such as polyethylene or polypropylene, a hydrocarbon such as polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), glass fiber, or the like.

  The polymer solid electrolyte has a structure in which a supporting salt (lithium salt) is dissolved in the matrix polymer, and does not include an organic solvent that is a plasticizer. Therefore, when the electrolyte layer is composed of a polymer solid electrolyte, there is no fear of liquid leakage from the battery, and the battery reliability can be improved.

  A matrix polymer of a polymer gel electrolyte or a polymer solid electrolyte can exhibit excellent mechanical strength by forming a crosslinked structure. In order to form a crosslinked structure, thermal polymerization, ultraviolet polymerization, radiation polymerization, electron beam polymerization, etc. are performed on a polymerizable polymer (for example, PEO or PPO) for forming a polymer electrolyte, using an appropriate polymerization initiator. A polymerization treatment may be performed. In addition, the said electrolyte may be contained in the active material layer of an electrode.

[Seal part]
The seal portion 31 is a member unique to the bipolar battery, and is disposed on the outer peripheral portion of the single cell layer 19 for the purpose of preventing leakage of the electrolyte layer 17. In addition to this, it is possible to prevent current collectors adjacent in the battery from coming into contact with each other and a short circuit due to a slight unevenness at the end of the laminated electrode. In the form shown in FIG. 1, the seal portion 31 is sandwiched between the respective current collectors 11 constituting the two adjacent unit cell layers 19 so as to penetrate the outer peripheral edge portion of the separator that is the base material of the electrolyte layer 17. Further, it is arranged on the outer peripheral portion of the unit cell layer 19. Examples of the constituent material of the seal portion 31 include polyolefin resins such as polyethylene and polypropylene, epoxy resins, rubber, and polyimide. Of these, polyolefin resins are preferred from the viewpoints of corrosion resistance, chemical resistance, film-forming properties, economy, and the like.

[Positive electrode current collector and negative electrode current collector]
The material which comprises a current collector plate (25, 27) is not restrict | limited in particular, The well-known highly electroconductive material conventionally used as a current collector plate for lithium ion secondary batteries can be used. As a constituent material of the current collector plate, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable. From the viewpoint of light weight, corrosion resistance, and high conductivity, aluminum and copper are more preferable, and aluminum is particularly preferable. Note that the positive electrode current collector plate 25 and the negative electrode current collector plate 27 may be made of the same material or different materials. Further, the outermost layer current collector (11a, 11b) may be extended to form a current collector plate, or a separately prepared tab may be connected to the outermost layer current collector.

[Positive lead and negative lead]
Moreover, although illustration is abbreviate | omitted, you may electrically connect between the collector 11 and the current collector plates (25, 27) via a positive electrode lead or a negative electrode lead. As a constituent material of the positive electrode and the negative electrode lead, materials used in known lithium ion secondary batteries can be similarly employed. In addition, heat-shrinkable heat-shrinkable parts are removed from the exterior so that they do not affect products (for example, automobile parts, especially electronic devices) by touching peripheral devices or wiring and causing leakage. It is preferable to coat with a tube or the like.

[Exterior]
As the exterior, a laminate sheet 29 as shown in FIGS. 1 and 2 can be used. For example, the laminate sheet may be configured as a three-layer structure in which polypropylene, aluminum, and nylon are laminated in this order. In some cases, a conventionally known metal can case can also be used as an exterior.

  The bipolar battery 10 and the stacked battery 10 ′ of the present embodiment use the negative electrode described above. Therefore, in these batteries, generation | occurrence | production of the cell swelling resulting from the expansion / contraction of the negative electrode active material layer at the time of charging / discharging of a battery is relieved. As a result, a flat plate type secondary battery excellent in cycle durability can be provided.

[Production method]
The manufacturing method of the flat laminated battery of this embodiment is not particularly limited, and can be manufactured by appropriately referring to conventionally known knowledge. Hereinafter, the battery manufacturing method of this embodiment will be briefly described.

The battery electrode can be produced, for example, by preparing an active material slurry containing an active material, a binder, and a solvent, applying the active material slurry onto a current collector, drying it, and pressing it.

  First, an active material slurry is prepared by mixing a desired active material, the above-described predetermined binder, and other components (for example, a conductive additive, a supporting salt, etc.) as necessary in a solvent. The binder may be mixed in the active material slurry by mixing the solid content of the active material and the like in a powder state and then adding a solvent and mixing the active material and the solvent. You may mix in an active material slurry by the method of adding to the mixture containing. In order to produce a positive electrode, a positive electrode active material is added to the slurry, and in order to produce a negative electrode, a negative electrode active material is added to the slurry.

  The kind of solvent and the mixing means are not particularly limited, and conventionally known knowledge can be referred to as appropriate. As an example of the solvent, N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylformamide and the like can be used.

  Subsequently, a current collector for forming an active material layer is prepared, and the prepared active material slurry is applied to the surface of the current collector to form a coating film.

The application means for applying the active material slurry is not particularly limited, but generally used means such as a self-propelled coater may be employed. However, when an ink jet method, a doctor blade method, or a combination thereof is used as the application unit, a thin layer can be formed.

  Thereafter, the coating film formed on the surface of the current collector is dried. Thereby, the solvent in a coating film is removed. The drying means for drying the coating film is not particularly limited, and conventionally known knowledge about electrode production can be appropriately referred to. For example, heat treatment is exemplified. Drying conditions (drying time, drying temperature, etc.) can be appropriately set according to the application amount of the active material slurry and the volatilization rate of the solvent of the slurry.

  Then, the coating film prepared above is pressed. The pressing means is not particularly limited, and conventionally known means can be appropriately employed. Examples of the pressing means include a calendar roll and a flat plate press.

  The positive electrode and negative electrode produced above and a separator (electrolyte layer) are laminated to produce a power generation element. The method for producing the electrolyte layer is not particularly limited, and can be produced by a conventionally known method. When the electrolyte layer contains a gel, the electrolyte layer can be formed by applying these electrolytes to the separator in advance, and further drying and heating.

  As for the insulating layer, for example, the periphery of the electrode forming portion is immersed or impregnated or impregnated with epoxy resin (precursor solution) or the like with a predetermined width. In any case, the electrode terminal plate, the electrode lead, the electrode tab, or the current collector portion to which these need to be connected are masked in advance using a releasable masking material or the like. Thereafter, the epoxy resin is cured to form an insulating portion, and then the masking material is peeled off.

  Subsequently, a lead is joined to each current collector of the obtained power generation element, and the positive electrode or the negative electrode lead is collectively joined to the positive electrode or the negative electrode tab. Next, the power generation element is placed in a laminate sheet so that the positive electrode and the negative electrode tab are exposed to the outside of the battery, and sealed in a vacuum. The electrolyte layer is formed by injecting an electrolyte with a liquid injector before sealing the laminate sheet. This fills the gap with the electrolyte. In order to add the additive to the electrolytic solution, the additive, the hydrocarbon solvent and the supporting salt may be appropriately mixed and used. In this way, the lithium ion battery of this embodiment is configured.

  The structure of the secondary battery of the present embodiment is a flat plate type battery obtained by laminating the flat structure shown in FIG. 1 and FIG. 2, and this is suitable for automobile loading. Further, when viewed in terms of electrical connection form (electrode structure) in the lithium ion secondary battery, it can be applied to both non-bipolar batteries and bipolar batteries.

[Battery]
An assembled battery may be configured by connecting a plurality of bipolar batteries or stacked batteries of the above-described embodiments. Specifically, an assembled battery can be configured by connecting at least two batteries in series, parallel, or both. At this time, it is possible to freely adjust the capacity and voltage by serialization and parallelization.

  The number of secondary batteries constituting the assembled battery of the present embodiment and the manner of connection can be determined according to the output and capacity required of the battery. According to this embodiment, a highly reliable assembled battery can be provided. In addition, by configuring the assembled battery of the present embodiment, it is possible to reduce the influence on the entire assembled battery due to deterioration of one single battery layer (single cell) constituting the assembled battery.

  As the assembled battery, a plurality of batteries (10, 10 ') of the above-described embodiment are connected in series and / or in parallel to form a small assembled battery that can be attached and detached. A plurality of small assembled batteries that can be attached and detached are connected in series and / or in parallel to form a larger assembled battery. As a result, the assembled battery is an assembled battery having a large capacity and a large output suitable for a vehicle driving power source and an auxiliary power source that require high volume energy density and high volume output density. The small assembled batteries that can be attached and detached are connected to each other using an electrical connection means such as a bus bar, and the assembled batteries are stacked in a plurality of stages using a connection jig. How many flat-stacked secondary batteries are connected to create an assembled battery, and how many assembled batteries are stacked to create a large assembled battery depends on the battery of the vehicle (electric vehicle) to be mounted It may be determined according to the capacity and output. Since the assembled battery of this embodiment is comprised using the flat laminated battery of embodiment mentioned above, it is excellent in durability.

[vehicle]
The secondary battery and the assembled battery of the above-described embodiment can be used as a driving power source for the vehicle. These secondary batteries or assembled batteries are, for example, hybrid vehicles, fuel cell vehicles, electric vehicles (all are automobiles (commercial vehicles such as passenger cars, trucks and buses, light vehicles), etc.) as well as motorcycles ( Motorcycles) and tricycles). Thereby, a long-life and highly reliable automobile can be provided. However, the application is not limited to automobiles. For example, if it is another vehicle, it can be applied to various power sources for moving bodies such as trains, and it can be used for mounting uninterruptible power supplies and the like. It can also be used as a power source.

  In order to mount the assembled battery on a vehicle such as an electric vehicle, it is mounted under the seat at the center of the body of the electric vehicle. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the assembled battery is mounted is not limited to the position under the seat, but may be a lower portion of the rear trunk room or an engine room in front of the vehicle. An electric vehicle using the assembled battery as described above has excellent durability and can provide a sufficient output even when used for a long time. Furthermore, it is possible to provide electric vehicles and hybrid vehicles that are excellent in fuel efficiency and running performance.

<Example 1>
1. Preparation of Electrolytic Solution A solvent mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (30:70 (volume ratio)) was used. An electrolyte was prepared using 1.0M LiPF ₆ as a supporting salt. “1.0 M LiPF ₆ ” means that the concentration of the supporting salt (LiPF ₆ ) in the mixture of the mixed solvent and the supporting salt is 1.0 M.

2. Production of Positive Electrode A solid content consisting of 85% by mass of LiMn ₂ O ₄ (average particle size: 15 μm) as a positive electrode active material, 5% by mass of acetylene black as a conductive additive, and 10% by mass of PVdF as a binder was prepared. An appropriate amount of N-methyl-2-pyrrolidone (NMP), which is a slurry viscosity adjusting solvent, was added to the solid content to prepare a positive electrode slurry. Next, the positive electrode slurry was applied to one side of an aluminum foil (20 μm) as a current collector and dried to prepare a positive electrode.

3. Production of Negative Electrode As a negative electrode active material, a solid content composed of 85% by mass of the multilayered carbon powder of A shown in Table 1 below, 5% by mass of acetylene black as a conductive additive and 10% by mass of PVdF as a binder was prepared. An appropriate amount of NMP, which is a slurry viscosity adjusting solvent, was added to the solid content to prepare a negative electrode slurry. Next, the negative electrode slurry was applied to one side of a copper foil (15 μm) as a current collector and dried to produce a negative electrode.

  Moreover, about the used carbon powder, the ratio of I110 / I004 was calculated | required by the XRD measurement. As the XRD measurement apparatus, an X-ray diffraction apparatus (MXP18VAHF type) manufactured by Mac Science, voltage / current: 40 kV, 300 mA, X-ray wavelength: CuKα was used.

  Further, the particle size distribution of the used carbon powder was measured by a laser diffraction method. As a measuring device, a microtrack particle size distribution measuring device (model HRA9320-X100) manufactured by Nikkiso Co., Ltd. was used.

  Further, the BET specific surface area of the used carbon powder was measured by a nitrogen adsorption method.

4). Step of Completing Single Cell A heated roll press was applied to each of the positive electrode and the negative electrode, and the hot press was performed so that the porosity was 20 to 30%. The porosity was calculated from the electrode thickness after pressure molding, the basis weight, the blending ratio of electrode materials, and the true density of each material.

  Thereafter, these were cut into a 90 × 90 mm square shape, and the positive electrode and the negative electrode were bonded together via a 95 × 95 mm separator (polyolefin microporous film, thickness 20 μm).

  A tab was welded to each of the positive electrode and the negative electrode, and sealed together with the electrolytic solution of this example in an exterior made of an aluminum laminate film, to complete a single cell.

5. Evaluation of Battery The flat laminated battery (unit cell) produced as described above was evaluated by a charge / discharge performance test. This charge / discharge performance test was performed in a thermostatic chamber maintained at 55 ° C. after the battery temperature was set to 55 ° C. Charging was performed by constant current charging (CC) up to 4.2 V at a current rate of 1 C, and then charging at a constant voltage (CV) for 3 hours. Thereafter, after a 10-minute rest period, discharging was performed at a current rate of 1 C up to 2.5 V, followed by a 10-minute rest period. These were made into 1 cycle, and the charging / discharging test was implemented. The ratio of discharge after 300 cycles with respect to the initial discharge capacity was defined as the capacity retention ratio, and the electrode swelling ratio was calculated from the electrode thickness before and after cell disassembly and the cross-sectional SEM photographs. The evaluation results are shown in Table 1 below.

<Examples 2 to 4>
A flat laminated battery was produced in the same manner as in Example 1 except that carbon powders B to D shown in Table 1 were used as the negative electrode active material. The obtained battery was evaluated in the same manner as in Example 1.

<Comparative Examples 1-4>
A flat laminated battery was manufactured in the same manner as in Example 1 except that carbon powders E to H shown in Table 1 below were used as the negative electrode active material. The obtained battery was evaluated in the same manner as in Example 1.

  As can be seen from Table 1, each of Examples 1 to 4 in which carbon powder having a ratio of I110 / I004 of 0.6 or more was used as the negative electrode active material, compared with Comparative Examples 1 to 4, all of which were swollen. Was small and showed excellent cycle characteristics.

10 Bipolar battery,
10 'stacked battery,
11 Current collector (positive electrode current collector),
11a Positive electrode side outermost layer current collector,
11b The negative electrode side outermost layer current collector,
12 negative electrode current collector,
13 positive electrode active material layer,
15 negative electrode active material layer,
17 electrolyte layer,
19 cell layer,
21 power generation elements,
25 positive current collector,
27 negative current collector,
29 Laminate sheet,
31 Seal part.

Claims (3)

A positive electrode;
A negative electrode,
An electrolyte layer interposed between the positive electrode and the negative electrode;
A flat plate battery having
The negative electrode contains carbon powder as a negative electrode active material, and the ratio of the peak intensity (I110) of the (110) plane and the peak intensity (I110) of the (004) plane of the graphite crystal obtained by XRD measurement of the carbon powder is I110 / I004 Ri der is 0.6 or more,
Wherein the carbon powder is, d (002) plane peak intensity ratio of 1360 cm ^-1 to the peak intensity of 1580 cm ^-1 interlayer distance (d value) and the nuclear material consisting of graphite 0.3380Nm, in the argon ion laser Raman spectrum of in it R values Ru multilayer structure carbonaceous powder der comprising a surface layer consisting of graphite is 0.1 or more, the flat plate laminate type nonaqueous electrolyte secondary battery. The flat laminate type nonaqueous electrolyte secondary battery according to claim 1, wherein the carbon powder has a BET specific surface area of 0.5 to 30 m ² / g. The flat-plate laminated nonaqueous electrolyte secondary battery according to claim 1 or 2 , wherein the positive electrode includes a manganese-containing positive electrode active material having a manganese elution amount of 0.04 mass% or less as a positive electrode active material.

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