JP2010277935A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means which improves charge and discharge characteristics at high rate. <P>SOLUTION: The nonaqueous electrolyte secondary battery has a battery element including a unit cell layer in which a positive electrode having a positive electrode active material layer containing a positive electrode active material and an electrolyte formed on the surface of a current collector and a negative electrode having a negative electrode active material layer containing a negative electrode active material and an electrolyte formed on the current collector are laminated through a separator containing the electrolyte. The electrolyte contains an ionic liquid and lithium salt, and a solvent diffusion layer containing a graft polymer chain with hydrophilicity is formed on the surface of the separator. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  An ionic liquid has attracted attention as a new medium replacing an organic solvent or water. The ionic liquid is an ionic compound, that is, a salt, but has a low melting point and is a liquid near room temperature. Although not clearly defined, generally, a salt having a melting point of 100 ° C. or lower is generally called an ionic liquid. Ionic liquids generally have characteristics such as non-volatility, incombustibility, thermal stability, chemical stability, and high ionic conductivity. It has been proposed to be used for various purposes. In particular, active research has been conducted on the use as a reaction solvent for organic synthesis and electrolytic synthesis and the use as an electrolyte of an electrochemical energy device such as a lithium ion battery (hereinafter also referred to as “electrochemical device”).

  For example, Patent Document 1 discloses a non-aqueous electrolyte secondary battery using a quaternary ammonium salt and a quaternary phosphonium salt having at least one alkoxyalkyl group as an ionic liquid.

JP 2004-146346 A

  However, the technique described in Patent Document 1 has a problem that since the ionic liquid has a high viscosity, the ionic liquid does not sufficiently diffuse into the separator, and charge / discharge characteristics at a high rate are insufficient. .

  Therefore, an object of the present invention is to provide means for improving charge / discharge characteristics at a high rate.

  The inventors of the present invention have made extensive studies in view of the above problems. As a result, it has been found that a non-aqueous electrolyte secondary battery provided with a solvent diffusion layer containing a hydrophilic graft polymer on the surface of the separator solves the above problems, and has completed the present invention.

  Since the graft polymer chain having hydrophilicity exists in a so-called brush shape on the separator surface, the ionic liquid penetrates between the graft polymer chains. Therefore, since the ionic liquid is easily diffused into the separator, the charge / discharge characteristics at a high rate are improved.

1 is a schematic cross-sectional view showing the structure of a stacked lithium ion secondary battery. 1 is a schematic cross-sectional view showing the structure of a bipolar lithium ion secondary battery. It is the schematic which represented the separator of 1st Embodiment typically. It is the schematic which represented the separator of 2nd Embodiment typically. It is the schematic which represented the separator of 3rd Embodiment typically. It is a perspective view showing the appearance of a nonaqueous electrolyte secondary battery. It is an external view of an assembled battery. It is a conceptual diagram of the vehicle carrying an assembled battery.

  First, although the nonaqueous electrolyte lithium ion secondary battery which is preferable embodiment is demonstrated, it is not restrict | limited only to the following embodiment. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may be different from the actual ratios.

  When distinguished by the structure and form of the nonaqueous electrolyte secondary battery, it is not particularly limited, such as a stacked (flat) battery or a wound (cylindrical) battery, and can be applied to any conventionally known structure. .

  Moreover, when it sees in the electrode material of a battery, or the metal ion which moves between electrodes, it does not restrict | limit in particular, It can apply to any well-known electrode material. Examples include lithium ion secondary batteries, sodium ion secondary batteries, potassium ion secondary batteries, nickel metal hydride secondary batteries, nickel cadmium secondary batteries, nickel metal hydride batteries, and the like, preferably lithium ion secondary batteries. . This is because in the lithium ion secondary battery, the voltage of the cell (single cell layer) is large, high energy density and high output density can be achieved, and it is excellent as a vehicle driving power source or an auxiliary power source.

[Battery overall structure]
FIG. 1 is a schematic diagram showing the basic configuration of an embodiment of a flat (stacked) nonaqueous electrolyte lithium ion secondary battery (hereinafter also simply referred to as “stacked battery”). As shown in FIG. 1, the stacked battery 10 a of this 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 body. . Here, in the power generation element 21, the positive electrode in which the positive electrode active material layer 13 is disposed on both surfaces of the positive electrode current collector 11, the electrolyte layer 17, and the negative electrode active material layer 15 is disposed on both surfaces of the negative electrode current collector 12. It has a configuration in which a negative electrode is laminated. Specifically, the negative electrode, the electrolyte layer, and the positive 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 stacked battery 10 of the present embodiment has a configuration in which a plurality of the single battery layers 19 are stacked and electrically connected in parallel. In addition, although the positive electrode active material layer 13 is arrange | positioned only in the single side | surface at all the outermost layer negative electrode collectors located in both outermost layers of the electric power generation element 21, an active material layer may be provided in both surfaces. That is, instead of using a current collector dedicated to the outermost layer provided with an active material layer only on one side, a current collector having an active material layer on both sides may be used as it is as an outermost current collector. In addition, the arrangement of the positive electrode and the negative electrode is reversed from that in FIG. 1, so that the outermost layer negative electrode current collector is positioned on both outermost layers of the power generation element 21, and the outermost layer negative electrode current collector is disposed on one or both surfaces. A negative electrode active material layer may be disposed.

  The positive electrode current collector 11 and the negative electrode current collector 12 are attached to 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), and are sandwiched between end portions of the laminate sheet 29. Thus, it has a structure led out of the laminate sheet 29. 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.

  FIG. 2 is a schematic cross-sectional view schematically showing the entire structure of the non-aqueous electrolyte bipolar lithium ion secondary battery 10. The bipolar lithium ion secondary battery 10 shown in FIG. 2 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 film 29 that is a battery exterior material.

  As shown in FIG. 2, the power generation element 21 of the bipolar lithium ion secondary battery 10 b is formed with a positive electrode active material layer 13 that is electrically coupled to one surface of the current collector 11, and is opposite to the current collector 11. It has a plurality of bipolar electrodes 23 formed with a negative electrode active material layer 15 electrically coupled to the side surface. Each bipolar electrode 23 is laminated 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, the positive electrode active material layer 13 of one bipolar electrode 23 and the negative electrode active material layer 15 of another bipolar electrode 23 adjacent to the one bipolar electrode 23 face each other through the electrolyte layer 17. The bipolar electrodes 23 and the electrolyte layers 17 are alternately stacked. That is, the electrolyte layer 17 is interposed between the positive electrode active material layer 13 of one bipolar electrode 23 and the negative electrode active material layer 15 of another bipolar electrode 23 adjacent to the one bipolar electrode 23. ing.

  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 lithium ion secondary 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 (insulating layer) 31 is disposed on the outer peripheral portion of the unit cell layer 19. 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 15 may be formed on both surfaces of the outermost layer current collector 11b on the negative electrode side.

  Further, in the bipolar secondary battery 10 shown in FIG. 2, a positive electrode current collector plate 25 is disposed adjacent to the outermost layer current collector 11a on the positive electrode side, and this is extended to form a laminate film 29 that is a battery exterior material. Derived. On the other hand, the negative electrode current collector plate 27 is disposed so as to be adjacent to the outermost layer current collector 11b on the negative electrode side, and similarly, this is extended and led out from the laminate film 29 which is an exterior of the battery.

  In the nonaqueous electrolyte bipolar lithium ion secondary battery 10 shown in FIG. 2, the insulating portion 31 is usually provided around each single cell layer 19. The insulating part 31 prevents the adjacent current collectors 11 in the battery from coming into contact with each other and a short circuit caused by a slight irregularity at the end of the unit cell layer 19 in the power generation element 21. Is provided. By installing such an insulating part 31, long-term reliability and safety can be ensured, and a high-quality bipolar lithium ion secondary battery 10 can be provided.

  Note that the number of stacks of the unit cell layers 19 is adjusted according to a desired voltage. Further, in the bipolar secondary battery 10, the number of stacking of the single battery layers 19 may be reduced if a sufficient output can be secured even if the thickness of the battery is made as thin as possible. In the bipolar lithium ion secondary battery 10, in order to prevent external impact and environmental degradation during use, the power generation element 21 is sealed under reduced pressure in a laminate film 29 that is a battery exterior material, and the positive electrode current collector plate 25 and A structure in which the negative electrode current collector plate 27 is taken out of the laminate film 29 is preferable.

  FIG. 3 is a schematic view of a separator (first embodiment) used in the electrolyte layer 17 of the nonaqueous electrolyte secondary battery shown in FIG. 1 or FIG. In the separator 40a shown in FIG. 3, a solvent diffusion layer 41a including a graft polymer chain 42 having hydrophilicity is formed on the surface of a separator substrate 46a.

  When an ionic liquid is used as an electrolyte solvent, the ionic liquid has a considerably higher viscosity than a non-aqueous solvent used in an ordinary electrochemical device, and hardly diffuses into the separator.

  Therefore, the device has insufficient high-rate charge / discharge characteristics (for example, charge / discharge characteristics observed when the discharge rate is 1.0 C or in the vicinity thereof; also referred to as high-rate charge / discharge characteristics) and low-temperature performance. Can not be used practically satisfied.

  As shown in FIG. 3, the separator 40a of this embodiment has a graft polymer chain 42 having hydrophilicity on the surface of the separator base 46 in a so-called brush shape. A positive electrode active material layer containing an electrolyte and a negative electrode active material layer (not shown) containing an electrolyte are provided so as to sandwich the separator 40a. Such a structure makes it easy for the ionic liquid (electrolyte) 48 accompanied by (solvated) the lithium salt to enter the graft polymer chain 42 having hydrophilicity. And it becomes easy to osmose | permeate the inside of the separator in the back, and the wettability to the separator of the ionic liquid with lithium salt (solvated) improves. As a result, lithium ions can diffuse faster in the separator, and charge / discharge characteristics at a high rate can be improved. Furthermore, the rapid diffusion of lithium ions in the separator facilitates the entry and exit of lithium ions associated with charging and discharging, and the cycle characteristics are improved.

  The separator of this embodiment will be described in further detail.

[Base material of separator]
The base material of the separator is not particularly limited, and a conventionally known one can be used. For example, a porous sheet separator, a nonwoven fabric separator, or the like made of a polymer that absorbs or holds an electrolyte (particularly, an electrolytic solution) can be used. Examples of the porous sheet separator include a microporous membrane made of polyolefin such as polyethylene (PE) and polypropylene (PP), a laminate having a three-layer structure of PP / PE / PP, polyethylene terephthalate (PET), and polyimide. It is done. As a material of the nonwoven fabric separator, for example, conventionally known materials such as cotton, rayon, acetate, nylon, polyester, polyolefin such as polypropylene and polyethylene, polyimide, or aramid resin can be used. A separator made of cellulose or ceramic may be used. Polyethylene or aramid resin is preferable.

  Also, polyethylene in which silicone is dispersed can be suitably used.

[Fixing agent]
It is preferable to add a fixing agent to the surface of the separator in advance before immobilizing the separator to the graft polymer. With this fixing agent, the graft polymer chain is fixed on the separator surface.

  Examples of the immobilizing agent used include 2-bromoisobutyric acid (6-triethoxysilyl) hexyl and the like.

  The method for adding the fixing agent is not particularly limited, and examples thereof include a method of immersing the separator substrate in a solution in which the fixing agent is dissolved. At this time, the immersion time is preferably 1 to 24 hours, and the immersion temperature is preferably 10 to 50 ° C.

  Moreover, 1-15 mass% is preferable with respect to the mass of a separator, and, as for the quantity which adds a fixing agent to the surface of a separator, 5-10 mass% is more preferable. If it is less than 1% by mass, the graft density of the graft polymer chain becomes too small, and it may not be possible to exhibit a function sufficient to give wettability to the separator. On the other hand, if it exceeds 15% by mass, the graft polymer chains may be entangled with each other and the diffusion of lithium ions in the separator may be insufficient. The amount to which the fixing agent is added can be easily controlled by the concentration of the fixing agent in the solution and the immersion time.

[Graft polymer having hydrophilicity]
The graft polymer that forms the solvent diffusion layer has hydrophilicity. The method for forming the graft polymer is not particularly limited, but an atom transfer radical polymerization method is preferred.

  Examples of the polymerization initiator used include, for example, ethyl 2-bromoisobutyrate, ethyl 2-bromopropionate, sulfonic acid chloride, benzyl chloride, 1-trichlorosilyl-2- (m, p-chloromethylphenyl) ethane, 2- (4-chlorosulfonylphenyl) ethyltrimethoxysilane, 2- (4-chlorosulfonylphenyl) ethyltrichlorosilane, (3- (2-bromoisobutyryl) propyl) dimethylethoxysilane, 2,2′-azo Bisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 4,4′-azobis (4-cyanovaleric) acid, 1,1′-azobis (1-cyclohexanecarbonitrile), Azobisisobutyric acid amidine hydrochloride, 2,2′-azobis (2,4-dimethylvaleronite) Ril), benzoyl peroxide, di-tert-butyl peroxide and the like. These polymerization initiators may be used alone or in combination of two or more.

  The amount of the polymerization initiator used is preferably 1 to 15% by mass and more preferably 2 to 13% by mass with respect to 100% by mass of the total amount of the monomer and the polymerization initiator.

  Examples of the monomer used include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, and (meth) acrylic acid 2- Ethylhexyl, heptyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, tetradecyl (meth) acrylate, hexadecyl (meth) acrylate , Octadecyl (meth) acrylate, aminomethyl (meth) acrylate, aminoethyl (meth) acrylate, N, N-dimethylaminomethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, (Meth) acrylic acid (2,2-dimethyl-1,3-dioxolane-4- (Meth) acrylic acid esters such as (R), basic polymerizable monomers such as (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, 4-vinylpyridine, (Meth) acrylic acid, 2-butenoic acid (crotonic acid), 3-butenoic acid (vinyl acetic acid), 3-methyl-3-butenoic acid, 3-pentenoic acid, 4-pentenoic acid, 4-methyl-4-pentene Acid, 4-hexenoic acid, 5-hexenoic acid, 5-methyl-5-hexenoic acid, 5-heptenoic acid, 6-heptenoic acid, 6-methyl-6-heptenoic acid, 6-octenoic acid, 7-octenoic acid, 7-methyl-7-octenoic acid, 7-nonenoic acid, 8-nonenoic acid, 8-methyl-8-nonenoic acid, 8-decenoic acid, 9-decenoic acid, 3-phenyl-2-propenoic acid (cinnamic acid ), Carboxy Tyl (meth) acrylate, carboxyethyl (meth) acrylate, vinyl benzoic acid, vinyl phenylacetic acid, vinyl phenylpropionic acid, maleic acid, fumaric acid, methylene succinic acid (itaconic acid), hydroxystyrene, styrene sulfonic acid, vinyl toluene sulfone Acid, vinyl sulfonic acid, sulfomethyl (meth) acrylate, 2-sulfoethyl (meth) acrylate, 2-propene-1-sulfonic acid, 2-methyl-2-propene-1-sulfonic acid, 3-butene-1-sulfonic acid And acidic polymerizable monomers such as

  The graft polymer chain in the solvent diffusion layer shown in FIG. 3 is formed from one type of monomer, but may be formed from two or more types of monomers. That is, the graft polymer chain may include two or more homopolymer chains, or may have a block copolymer structure having two or more polymer blocks as described later.

  Moreover, as long as the graft polymer chain which has hydrophilicity at least is introduce | transduced like embodiment mentioned later, the graft polymer chain which has hydrophobicity may be introduce | transduced. The graft polymer chain may have a block copolymer structure having a hydrophilic polymer block and a hydrophobic polymer block.

  Among these monomers, (meth) acrylic acid and (meth) acrylic acid (2,2-dimethyl-1,3-dioxolan-4-yl) are more preferable.

  The solvent used in the atom transfer radical polymerization is not particularly limited. For example, dimethyl sulfoxide, dimethylformamide, acetonitrile, pyridine, methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, cyclohexanol, methyl Cellosolve, ethyl cellosolve, isopropyl cellosolve, butyl cellosolve, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, butyl acetate, ethyl propionate, dimethyl ether, diethyl ether, trioxane, tetrahydrofuran, pentane, cyclopentane, hexane, cyclohexane, heptane, Octane, nonane, decane, benzene, toluene, xylene, ethylbenzene, methoxybenzene And the like can be used. These may be used singly or in combination of two or more.

  The polymerization time for the atom transfer radical polymerization is preferably 2 to 24 hours, more preferably 4 to 24 hours. Moreover, the polymerization temperature of the atom transfer radical polymerization is preferably 20 to 100 ° C, more preferably 30 to 90 ° C.

  The weight average molecular weight of the graft polymer chain thus obtained is preferably 10,000 to 1,000,000, more preferably 100,000 to 500,000. When the weight average molecular weight is less than 10,000, there may be a case where a function sufficient to give wettability to the separator cannot be exhibited. On the other hand, when it exceeds 1,000,000, the graft polymer chains are entangled with each other, and the diffusion of lithium ions in the separator may be insufficient. In addition, in this specification, the value measured by GPC (gel permeation chromatography) which used polystyrene as a reference material shall be employ | adopted for a weight average molecular weight.

The graft density of the graft polymer is preferably 0.01 to 1 chain / nm ² , and more preferably 0.05 to 1 chain / nm ² . By setting it in this range, the wettability of the separator with respect to the ionic liquid is improved, lithium ions can be diffused faster in the separator, and high-speed charge / discharge is possible (high rate characteristics are improved). Furthermore, the rapid diffusion of lithium ions in the separator facilitates reversible lithium ion entry / exit associated with charging / discharging, thereby improving cycle characteristics.

  The graft density can be controlled by the amount of the fixing agent to be fixed to the separator. When the relationship between the graft amount quantified by ellipsometry and the number average molecular weight (Mn) of the free polymer was examined, it was found that the graft amount increased in proportion to Mn. Therefore, the graft amount can be determined from the slope of the graph obtained by plotting several points, taking the number average molecular weight of the polymer chain on the horizontal axis and the graft amount on the vertical axis.

  In FIG. 3, the graft polymer chain is introduced only on one surface of the separator substrate 46a, but of course, the graft polymer chain may be introduced on both surfaces of the separator substrate.

  FIG. 4 is a schematic diagram showing the separator 40b of the second embodiment. The graft polymer chains (42, 43) forming the solvent diffusion layer 41b on the surface of the separator substrate 46b shown in FIG. 4 have a diblock copolymer structure formed from two different hydrophilic monomers. When the graft polymer chain is only a homopolymer chain as shown in FIG. 3, only the repulsive force between adjacent graft polymer chains works. However, as shown in FIG. 4, by making the graft polymer chain into a diblock copolymer structure, the repulsive force between the graft polymer chains becomes more effective, and as a result, the graft polymer chain is more likely to rise. A space is created between them. A positive electrode active material layer containing an electrolyte and a negative electrode active material layer (not shown) containing an electrolyte are provided so as to sandwich the separator 40b. With such a structure, the ionic liquid (electrolyte) 48 accompanied by the lithium salt can easily penetrate into the separator, and charge / discharge characteristics at a high rate can be improved. Furthermore, the rapid diffusion of lithium ions in the separator facilitates the entry and exit of lithium ions associated with charging and discharging, and the cycle characteristics are improved.

  FIG. 4 shows an embodiment in which the graft polymer chain has a diblock copolymer structure, but the present invention is not limited to this, and a multiblock copolymer structure such as a triblock structure or a tetrablock structure may be used.

  FIG. 5 is a schematic view showing a separator 40c of the third embodiment. The graft polymer chains (42, 44) forming the solvent diffusion layer 41c on the surface of the separator base 46c shown in FIG. 5 have a diblock copolymer structure formed from two different types of monomers. However, the polymer block on the side close to the separator is a hydrophobic polymer chain 44 formed from a hydrophobic monomer, and the hydrophilic polymer block 42 formed from a hydrophilic monomer is formed on the side away from the separator. ing. By adopting a graft polymer chain structure having a hydrophobic polymer block and a hydrophilic polymer chain as in the present embodiment, the repulsive force between the graft polymer chains is further increased, and as a result, the brush is likely to rise. It becomes possible to create a space between brushes. A positive electrode active material layer containing an electrolyte and a negative electrode active material layer (not shown) containing an electrolyte are provided so as to sandwich the separator 40c. With such a structure, the ionic liquid (electrolyte) 48 accompanied by the lithium salt can easily penetrate into the separator, and charge / discharge characteristics at a high rate can be improved. Furthermore, the rapid diffusion of lithium ions in the separator facilitates the entry and exit of lithium ions associated with charging and discharging, and the cycle characteristics are improved.

  Examples of monomers that form a hydrophobic polymer chain include, for example, fluorine-containing vinyl monomers such as tetrafluoroethylene, hexafluoropropylene, and vinylidene fluoride; acrylonitrile monomers such as acrylonitrile and methacrylonitrile; and ethylene and propylene. Alkenes; conjugated dienes such as butadiene and isoprene; aromatic vinyl compounds such as styrene and α-methylstyrene; vinyl chloride, vinylidene chloride, and allyl chloride. These may be used alone or two or more of them may be copolymerized.

  When the hydrophobic polymer chain is introduced into the graft polymer chain forming the solvent diffusion layer, the amount introduced is preferably 10 to 50% by mass with respect to the entire graft polymer chain. The hydrophobic polymer chain is preferably introduced on the proximity side of the separator.

  The method for forming the graft polymer chain having the block copolymer structure as described above is not particularly limited. For example, a method of forming a polymer chain by forming a polymer chain by an atom transfer radical polymerization method after adding a second monomer and a polymerization initiator to the first monomer is formed. It is done.

(Electrolytes)
The electrolyte includes an ionic liquid as a solvent and a lithium salt as an electrolyte salt, and further includes an additive as necessary.

[Ionic liquid]
An ionic liquid refers to a series of compounds that are liquid at room temperature despite being a salt composed only of cations and anions.

  The cation component constituting the ionic liquid can be substituted or unsubstituted imidazolium ions, substituted or unsubstituted pyridinium ions, substituted or unsubstituted pyrrolium ions, substituted or non-substituted Substituted pyrazolium ion, substituted or unsubstituted pyrrolinium ion, substituted or unsubstituted pyrrolidinium ion, substituted or unsubstituted piperidinium ion, substituted or unsubstituted It is preferably at least one selected from the group consisting of triazinium ions and substituted or unsubstituted ammonium ions.

  Specific examples of the substituted or unsubstituted imidazolium ion include, for example, 1-ethyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, 1-hexyl-2, 3-dimethylimidazolium, 1,3-dimethylimidazolium ion, 1-ethyl-3-methylimidazolium ion, 1,3-diethylimidazolium ion, 1-butyl-3-methylimidazolium ion, 1-hexyl- 3-methylimidazolium ion, 1-octyl-3-methylimidazolium ion, 1-decyl-3-methylimidazolium ion, 1-tetradecyl-3-methylimidazolium ion, 1-hexadecyl-3-methylimidazolium ion 1-octadecyl-3-methylimidazolium ion, 1 2,3-trimethylimidazolium ion, 1,2-dimethyl-3-ethylimidazolium ion, 1,2-dimethyl-3-propylimidazolium ion, 1-butyl-2,3-dimethylimidazolium ion, etc. Can be mentioned. However, it is not limited to these.

  Specific examples of the substituted or unsubstituted ammonium ion include, for example, trimethylethylammonium ion, trimethylpropylammonium ion, trimethylhexylammonium ion, tetrapentylammonium ion, N, N-diethyl-N-methyl-N -(2-methoxyethyl) ammonium ion etc. are mentioned. However, it is not limited to these.

  Specific examples of the substituted or unsubstituted pyridinium ion include, for example, N-methylpyridinium ion, N-ethylpyridinium ion, N-propylpyridinium ion, N-butylpyridinium ion, N-hexylpyridinium ion, 1 -Ethyl-2-methylpyridinium ion, 1-butyl-3-methylpyridinium ion, 1-butyl-4-methylpyridinium ion, 1-hexyl-4-methylpyridinium ion, 1-hexyl-3-methylpyridinium ion, 1 -Butyl-2,4-dimethylpyridinium ion etc. are mentioned. However, it is not limited to these.

  Specific examples of the substituted or unsubstituted pyrrolium ion include, for example, 1,1-dimethylpyrrolium ion, 1-ethyl-1-methylpyrrolium ion, 1-methyl-1-propylpyrrolium ion, 1-butyl. Examples include -1-methylpyrrolium ion. However, it is not limited to these.

  Specific examples of the substituted or unsubstituted pyrazolium ion include, for example, 1,2-dimethylpyrazolium ion, 1-ethyl-2-methylpyrazolium ion, 1-propyl-2-methylpyrazolium ion 1-butyl-2-methylpyrazolium ion and the like. However, it is not limited to these.

  Specific examples of the substituted or unsubstituted pyrrolium ion include, for example, 1,2-dimethylpyrrolium ion, 1-ethyl-2-methylpyrrolium ion, 1-propyl-2-methylpyrrolium ion. 1-butyl-2-methylpyrrolium ion, and the like. However, it is not limited to these.

  Specific examples of the substituted or unsubstituted pyrrolidinium ion include, for example, 1,1-dimethylpyrrolidinium ion, 1-ethyl-1-methylpyrrolidinium ion, 1-methyl-1-propylpyrrolidinium ion. 1-butyl-1-methylpyrrolidinium ion and the like. However, it is not limited to these.

  Specific examples of the substituted or unsubstituted piperidinium ion include, for example, 1,1-dimethylpiperidinium ion, 1-ethyl-1-methylpiperidinium ion, 1-methyl-1-propylpiperidinium ion. 1-butyl-1-methylpiperidinium ion and the like, but is not limited thereto.

  Specific examples of the substituted or unsubstituted triazinium ion include 1,3-diethyl-5-methyltriazinium ion, 1,3-diethyl-5-butyltriazinium ion, 1,3- Examples thereof include dimethyl-5-ethyltriazinium ion and 1,3,5-tributyltriazinium ion. However, it is not limited to these.

  Among these, the cation component is a substituted or unsubstituted imidazolium ion, a substituted or unsubstituted pyridinium ion, a substituted or unsubstituted pyrrolidinium ion, and a substituted or More preferably, it is at least one selected from the group consisting of unsubstituted ammonium ions.

Specific examples of the anion component constituting the ionic liquid include halide ions such as fluoride ion, chloride ion, bromide ion and iodide ion, nitrate ion (NO ₃ ⁻ ), tetrafluoroborate ion (BF ₄ ⁻ ), Hexafluorophosphate ion (PF ₆ ⁻ ), (FSO ₂ ) ₂ N ⁻ , AlCl ₃ ⁻ , lactate ion, acetate ion (CH ₃ COO ⁻ ), trifluoroacetate ion (CF ₃ COO ⁻ ), methane sulfonate ion _{(CH 3} SO 3 ^-), trifluoromethanesulfonate ion _(CF 3 SO ₃ ^-), bis (trifluoromethanesulfonyl) imide ion _{((CF 3 SO 2) 2} N -), bis (pentafluoroethyl sulfonyl) Imido ion ((C ₂ F ₅ SO ₂ ) ₂ N ⁻ ), BF ₃ C ₂ F ₅ ⁻ , Tris (trifluoromethanesulfonyl) carbonic acid ion ((CF ₃ SO ₂ ) ₃ C ⁻ ), perchlorate ion (ClO ₄ ⁻ ), dicyanamide ion ((CN) ₂ N ⁻ ), organic sulfate ion, organic sulfonate ^{ion, R 1 COO -, HOOCR 1} COO -, - OOCR 1 COO -, NH 2 CHR 1 COO - ( Here, ^{R 1} is a substituent, an aliphatic hydrocarbon group, alicyclic hydrocarbon group , An aromatic hydrocarbon group, an ether group, an ester group, or an acyl group, and the substituent may contain a fluorine atom).

  Among these, the anion component is composed of halide ion, tetrafluoroborate ion, hexafluorophosphate ion, bis (trifluoromethanesulfonyl) imide ion, trifluoromethanesulfonate ion, organic sulfate ion, and organic sulfonate ion. More preferably, it is at least one selected from the group.

  Specific examples of the ionic liquid include the compounds shown below.

1,3-dimethylimidazolium methanesulfonate,
1-ethyl-3-methylimidazolium chloride,
1-ethyl-3-methylimidazolium bromide,
1-ethyl-3-methylimidazolium methanesulfonate,
1-ethyl-3-methylimidazolium hexafluorophosphate,
1-ethyl-3-methylimidazolium (L) -lactate,
1-ethyl-3-methylimidazolium tetrafluoroborate,
1-ethyl-3-methylimidazolium trifluoromethanesulfonate,
1-ethyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide 1-allyl-3-ethylimidazolium tetrafluoroborate,
1-butyl-3-methylimidazolium chloride,
1-butyl-3-methylimidazolium trifluoromethanesulfonate,
1-butyl-3-methylimidazolium (L) -lactate,
1-butyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide,
1-butyl-3-methylimidazolium tetrafluoroborate,
1-hexyl-3-methylimidazolium chloride,
1-hexyl-3-methylimidazolium bromide,
1-hexyl-3-methylimidazolium iodide,
1-hexyl-3-methylimidazolium trifluoromethanesulfonate,
1-hexyl-3-methylimidazolium hexafluorophosphate,
1-hexyl-3-methylimidazolium tetrafluoroborate,
1-octyl-3-methylimidazolium chloride,
1-octyl-3-methylimidazolium hexafluorophosphate,
1-octyl-3-methylimidazolium tetrafluoroborate,
1-decyl-3-methylimidazolium chloride,
1-dodecyl-3-methylimidazolium chloride,
1-tetradecyl-3-methylimidazolium chloride,
1-hexadecyl-3-methylimidazolium chloride,
1-octadecyl-3-methylimidazolium chloride 1-ethyl-2,3-dimethylimidazolium chloride,
1-ethyl-2,3-dimethylimidazolium bromide,
1-butyl-2,3-dimethylimidazolium bromide,
1-butyl-2,3-dimethylimidazolium chloride,
1-butyl-2,3-dimethylimidazolium tetrafluoroborate,
1-butyl-2,3-dimethylimidazolium trifluoromethanesulfonate,
1-hexyl-2,3-dimethylimidazolium bromide,
1-hexyl-2,3-dimethylimidazolium chloride,
1-hexyl-2,3-dimethylimidazolium trifluoroborate,
1-hexyl-2,3-dimethylimidazolium trifluoromethanesulfonate 1-ethylpyridinium chloride,
1-ethylpyridinium bromide,
1-butylpyridinium chloride,
1-butylpyridinium bromide,
1-butylpyridinium hexafluorophosphate,
1-butylpyridinium tetrafluoroborate,
1-butylpyridinium trifluoromethanesulfonate,
1-hexylpyridinium chloride,
1-hexylpyridinium bromide,
1-hexylpyridinium hexafluorophosphate,
1-hexylpyridinium tetrafluoroborate,
1-hexylpyridinium trifluoromethanesulfonate,
1-butyl-4-methylpyridinium tetrafluoroborate,
N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate,
N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium tetrafluoroborate,
1-butyl-3-methylimidazolium hexafluorophosphate 1-butyl-3-methylimidazolium tetrachloroaluminate,
1-hexylpyridinium hexafluorophosphate,
1-methyl-1-propylpyrrolidinium bis (trifluoromethanesulfonyl) imide,
1-methyl-1-propylpiperidinium bis (trifluoromethanesulfonyl) imide,
N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide,
N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium hexafluorophosphate,
N, N, N-trimethyl-N-propylammonium bis (trifluoromethanesulfonyl) imide.

  These ionic liquids can be used alone or in combination of two or more.

  Among these, 1-methyl-3-methylimidazolium bis (trifluoromethanesulfonyl) imide (hereinafter also simply referred to as “EMI-TFSI”), or N-methyl-N-propylpyrrolidinium bis (trifluoromethanesulfonyl) imide (Hereinafter, also simply referred to as “Py13-FSI”) is more preferable.

  Examples of the production method of the ionic liquid include a method of producing an ionic liquid by adding an alkyl halide to an organic amine, and a production method of further performing an anion exchange reaction using a salt having a target anion. It is done. There is also a method of producing by neutralizing an organic amine and an acid having a target anion. The production method of the ionic liquid may be a production method other than these, and a commercially available product may be used as the ionic liquid.

[Electrolyte salt]
As the electrolyte salt (lithium salt), for _{example, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anion salts such _as, LiCF ₃ SO 3, Li ( Examples thereof include organic acid anion salts such as CF ₃ SO ₂ ) ₂ N and Li (C ₂ F ₅ SO ₂ ) ₂ N.

  The concentration of the electrolyte salt is preferably 0.1 to 2.0M, and more preferably 0.8 to 1.2M.

[Additive]
The electrolyte may further contain an additive in addition to the ionic liquid and the electrolyte salt (lithium salt). By including an additive, charge / discharge characteristics and cycle characteristics at a high rate can be further improved.

  Specific examples of the additive include, for example, vinylene carbonate, ethylene carbonate, propylene carbonate, γ-butyllactone, γ-valerolactone, methyl diglyme, sulfolane, trimethyl phosphate, triethyl phosphate, methoxymethyl ethyl carbonate, Examples thereof include fluorinated ethylene carbonate. These may be used alone or in combination of two or more.

  The amount of the additive used is preferably 0.5 to 10% by mass, more preferably 0.5 to 5% by mass with respect to the ionic liquid.

  The method for preparing an electrolyte containing an ionic liquid, a lithium salt, and, if necessary, an additive is not particularly limited. For example, a method of sequentially mixing an ionic liquid, a lithium salt, and an additive, an ionic liquid, Examples include a method of mixing a lithium salt and an additive at a time.

  The non-aqueous electrolyte secondary battery described above is characterized by the configuration of the separator and the electrolyte. Hereinafter, other main components will be described.

(Current collector)
The current collector is made of a conductive material. The size of the current collector is determined according to the intended use of the battery. For example, if it is used for a large battery that requires a high energy density, a current collector having a large area is used. There is no particular limitation on the thickness of the current collector. The thickness of the current collector is usually about 1 to 100 μm.

  There is no particular limitation on the material constituting the current collector. For example, a metal or a resin in which a conductive filler is added to a conductive polymer material or a non-conductive polymer material can be employed. Specifically, examples of the metal include aluminum, nickel, iron, stainless steel, titanium, and copper. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Moreover, the foil by which aluminum is coat | covered on the metal surface may be sufficient. Of these, aluminum, stainless steel, and copper are preferable from the viewpoints of electronic conductivity and battery operating potential.

  Examples of the conductive polymer material include polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene, polyphenylene vinylene, polyacrylonitrile, and polyoxadiazole. Since such a conductive polymer material has sufficient conductivity without adding a conductive filler, it is advantageous in terms of facilitating the manufacturing process or reducing the weight of the current collector.

  Non-conductive polymer materials include, for example, polyethylene (PE; high density polyethylene (HDPE), low density polyethylene (LDPE), etc.), polypropylene (PP), polyethylene terephthalate (PET), polyether nitrile (PEN), polyimide (PI), polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA) , Polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), or polystyrene (PS). Such a non-conductive polymer material may have excellent potential resistance or solvent resistance.

  A conductive filler may be added to the conductive polymer material or the non-conductive polymer material as necessary. In particular, when the resin used as the base material of the current collector is made of only a non-conductive polymer, a conductive filler is inevitably necessary to impart conductivity to the resin. The conductive filler can be used without particular limitation as long as it is a substance having conductivity. For example, metals, conductive carbon, etc. are mentioned as a material excellent in electroconductivity, electric potential resistance, or lithium ion barrier | blocking property. The metal is not particularly limited, but at least one metal selected from the group consisting of Ni, Ti, Al, Cu, Pt, Fe, Cr, Sn, Zn, In, Sb, and K, or these metals It is preferable to contain an alloy or metal oxide containing. The conductive carbon is not particularly limited, but is at least selected from the group consisting of acetylene black, vulcan, black pearl, carbon nanofiber, ketjen black, carbon nanotube, carbon nanohorn, carbon nanoballoon, and fullerene. It is preferable that 1 type is included. The amount of the conductive filler added is not particularly limited as long as it is an amount capable of imparting sufficient conductivity to the current collector, and is generally about 5 to 35% by mass.

(Active material layer)
[Positive electrode (positive electrode active material layer) and negative electrode (negative electrode active material layer)]
The active material layer 13 or 15 contains an active material, and further contains other additives as necessary.

The positive electrode active material layer 13 includes a positive electrode active material. As the positive electrode active material, for example, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni—Co—Mn) O _2, and lithium-such as those in which a part of these transition metals are substituted with other elements Examples include transition metal composite oxides, lithium-transition metal phosphate compounds, and lithium-transition metal sulfate compounds. In some cases, two or more positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material from the viewpoint of capacity and output characteristics. Of course, positive electrode active materials other than those described above may be used.

The negative electrode active material layer 15 includes a negative electrode active material. Examples of the negative electrode active material include carbon materials such as graphite, soft carbon, and hard carbon, lithium-transition metal composite oxides (for example, Li ₄ Ti ₅ O ₁₂ ), metal materials, lithium alloy negative electrode materials, and the like. . In some cases, two or more negative electrode active materials may be used in combination. Preferably, from the viewpoint of capacity and output characteristics, a carbon material or a lithium-transition metal composite oxide is used as the negative electrode active material. Of course, negative electrode active materials other than those described above may be used.

  The average particle diameter of each active material contained in each active material layer 13, 15 is not particularly limited, but is preferably 1 to 20 μm from the viewpoint of increasing the output.

  The positive electrode active material layer 13 and the negative electrode active material layer 15 include a binder.

  Although it does not specifically limit as a binder used for an active material layer, For example, the following materials are mentioned. Polyethylene, polypropylene, polyethylene terephthalate (PET), polyether nitrile (PEN), polyacrylonitrile, polyimide, polyamide, cellulose, carboxymethyl cellulose (CMC), ethylene-vinyl acetate copolymer, polyvinyl chloride, styrene-butadiene rubber (SBR) ), Isoprene rubber, butadiene rubber, ethylene / propylene rubber, ethylene / propylene / diene copolymer, styrene / butadiene / styrene block copolymer and hydrogenated product thereof, styrene / isoprene / styrene block copolymer and hydrogenated product thereof Thermoplastic polymers such as products, polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene copolymer (FE) ), Tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA), ethylene / tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE) , Fluororesin such as polyvinyl fluoride (PVF), vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-) TFE fluorine rubber), vinylidene fluoride-pentafluoropropylene fluorine rubber (VDF-PFP fluorine rubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene Fluoro rubber (VDF-PFP-TFE fluoro rubber), vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene fluoro rubber (VDF-PFMVE-TFE fluoro rubber), vinylidene fluoride-chlorotrifluoroethylene fluoro rubber Examples thereof include vinylidene fluoride-based fluororubber such as (VDF-CTFE-based fluororubber), an epoxy resin, and the like. Among these, polyvinylidene fluoride, polyimide, styrene / butadiene rubber, carboxymethyl cellulose, polypropylene, polytetrafluoroethylene, polyacrylonitrile, and polyamide are more preferable. These suitable binders are excellent in heat resistance, have a very wide potential window, are stable at 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.

  The amount of the binder contained in the active material layer is not particularly limited as long as it is an amount capable of binding the active material, but is preferably 0.5 to 15% by mass with respect to the active material layer. Yes, more preferably 1 to 10% by mass.

  The active material layer contains an electrolyte containing an ionic liquid, an electrolyte salt, and, if necessary, an additive. Since specific examples of the electrolyte are as described above, description thereof is omitted here.

  Furthermore, as another additive that can be included in the active material layer, for example, a conductive additive can be mentioned.

  The conductive assistant refers to an additive that is blended in order to improve the conductivity of the positive electrode active material layer or the negative electrode active material layer. Examples of the conductive assistant 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 improvement of the output characteristics of the battery.

  The compounding ratio of the components contained in the positive electrode active material layer and the negative electrode active material layer is not particularly limited. The mixing ratio can be adjusted by appropriately referring to known knowledge about the non-aqueous solvent secondary battery. The thickness of each active material layer is not particularly limited, and conventionally known knowledge about the battery can be appropriately referred to. For example, the thickness of each active material layer is about 2 to 100 μm.

(Outermost layer current collector)
As the material of the outermost layer current collector, for example, a metal or a conductive polymer can be adopted. From the viewpoint of ease of taking out electricity, a metal material is preferably used. Specifically, metal materials, such as aluminum, nickel, iron, stainless steel, titanium, copper, are mentioned, for example. In addition to these, a clad material of nickel and aluminum, a clad material of copper and aluminum, or a plating material of a combination of these metals can be preferably used. Moreover, the foil by which aluminum is coat | covered on the metal surface may be sufficient. Of these, aluminum and copper are preferable from the viewpoints of electron conductivity and battery operating potential.

(Tabs and leads)
A tab may be used for the purpose of taking out the current outside the battery. The tab is electrically connected to the outermost layer current collector or current collector plate, and is taken out of the laminate sheet which is a battery exterior material.

  The material which comprises a tab in particular is not restrict | limited, The well-known highly electroconductive material conventionally used as a tab for lithium ion secondary batteries can be used. As a constituent material of the tab, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable, and aluminum, copper, and the like are more preferable from the viewpoint of light weight, corrosion resistance, and high conductivity. Is preferred. Note that the same material may be used for the positive electrode tab and the negative electrode tab, or different materials may be used.

  The positive terminal lead and the negative terminal lead are also used as necessary. As the material of the positive terminal lead and the negative terminal lead, a terminal lead used in a known lithium ion secondary battery can be used. It should be noted that the part taken out from the battery outer packaging material 29 has a heat insulating property so as not to affect the product (for example, automobile parts, particularly electronic devices) by contacting with peripheral devices or wiring and causing leakage. It is preferable to coat with a heat shrinkable tube or the like.

(Battery exterior material)
As the battery exterior material 29, a known metal can case can be used, and a bag-like case using a laminate film containing aluminum that can cover a power generation element (battery element) can be used. For example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used as the laminate film, but the laminate film is not limited thereto. A laminate film is desirable from the viewpoint that it is excellent in high output and cooling performance, and can be suitably used for a battery for large equipment for EV and HEV.

(Insulation part)
The insulating part 31 prevents a liquid junction due to leakage of the electrolytic solution from the electrolyte layer 17. Further, the insulating part 31 is intended to prevent current collectors adjacent to each other in the battery from contacting each other or a short circuit caused by a slight irregularity at the end of the unit cell layer 19 in the power generation element 21. Is provided.

  The material constituting the insulating portion 31 may have insulating properties, sealing properties against falling off of the solid electrolyte, sealing properties against moisture permeation from the outside (sealing properties), heat resistance at the battery operating temperature, and the like. That's fine. For example, urethane resin, epoxy resin, polyethylene resin, polypropylene resin, polyimide resin, rubber and the like can be used. Among these, polyethylene resin and polypropylene resin are preferably used as the constituent material of the insulating portion 31 from the viewpoints of corrosion resistance, chemical resistance, ease of production (film forming property), economy, and the like.

  In addition, said non-aqueous electrolyte secondary battery can be manufactured with a conventionally well-known manufacturing method.

<External configuration of nonaqueous electrolyte secondary battery>
FIG. 6 is a perspective view showing the appearance of a stacked flat lithium ion secondary battery which is a typical embodiment of a nonaqueous electrolyte secondary battery.

  As shown in FIG. 6, the laminated flat lithium ion secondary battery 50 has a rectangular flat shape, and a positive electrode tab 58 and a negative electrode tab 59 for taking out electric power from both sides thereof. Has been pulled out. The power generation element (battery element) 57 is wrapped by the battery outer packaging material 52 of the lithium ion secondary battery 50, and the periphery thereof is heat-sealed. The power generation element (battery element) 57 includes a positive electrode tab 58 and a negative electrode tab 59. It is sealed in a state where it is pulled out to the outside. Here, the power generation element (battery element) 57 corresponds to the power generation element (battery element) 21 of the nonaqueous electrolyte secondary battery 10 shown in FIGS. 1 and 2 described above. The power generation element (battery element) 57 is formed by laminating a plurality of single battery layers (single cells) 19 including a positive electrode (positive electrode active material layer) 13, an electrolyte layer 17, and a negative electrode (negative electrode active material layer) 15. .

  The lithium ion battery is not limited to a laminated flat shape, and a wound lithium ion battery may have a cylindrical shape, or such a cylindrical shape. There is no particular limitation such that the object may be deformed into a rectangular flat shape. In the said cylindrical shape thing, a laminate film may be used for the exterior material, and the conventional cylindrical can (metal can) may be used, for example, It does not restrict | limit. Preferably, the power generation element (battery element) is covered with an aluminum laminate film. With this configuration, weight reduction can be achieved.

  6 is not particularly limited, and the positive electrode tab 58 and the negative electrode tab 59 may be drawn from the same side, or the positive electrode tab 58 and the negative electrode tab 59 may be pulled out. However, the present invention is not limited to the one shown in FIG. 6, for example. Further, in a wound type lithium ion battery, instead of a tab, for example, a terminal may be formed using a cylindrical can (metal can).

  The lithium ion battery is suitable as a power source for driving a vehicle or an auxiliary power source that requires a high volume energy density and a high volume output density as a large capacity power source for an electric vehicle, a hybrid electric vehicle, a fuel cell vehicle, a hybrid fuel cell vehicle, etc. Can be used.

<Battery assembly>
The assembled battery is formed by connecting a plurality of the nonaqueous electrolyte secondary batteries. Specifically, at least two or more are used, and are configured by serialization, parallelization, or both. Capacitance and voltage can be freely adjusted by paralleling in series.

  7 is an external view of a typical embodiment of an assembled battery, FIG. 7A is a plan view of the assembled battery, FIG. 7B is a front view of the assembled battery, and FIG. 7C is a side view of the assembled battery. is there.

  As shown in FIG. 7, the assembled battery 300 forms a small assembled battery 250 in which a plurality of nonaqueous electrolyte secondary batteries are connected in series or in parallel to be detachable. A large capacity and large output suitable for a vehicle driving power source and an auxiliary power source that require a high volume energy density and a high volume output density by connecting a plurality of these detachable small assembled batteries 250 in series or in parallel. It is also possible to form an assembled battery 300 having 7A is a plan view of the assembled battery, FIG. 7B is a front view, and FIG. 7C is a side view. The small assembled battery 250 that can be attached and detached is provided with an electrical connection means such as a bus bar. The assembled battery 250 is stacked in a plurality of stages using the connection jig 310. How many non-aqueous electrolyte secondary batteries are connected to produce the assembled battery 250, and how many assembled batteries 250 are laminated to produce the assembled battery 300 depends on the mounted vehicle (electric vehicle). Depending on the battery capacity and output.

<Vehicle>
A vehicle is equipped with the non-aqueous electrolyte secondary battery or an assembled battery formed by combining a plurality of these. Since a long-life battery excellent in long-term reliability and output characteristics can be configured, a plug-in hybrid electric vehicle having a long EV mileage and an electric vehicle having a long charge mileage can be formed by installing such a battery. In other words, the non-aqueous electrolyte secondary battery or an assembled battery formed by combining a plurality of these can be used as a power source for driving the vehicle. A non-aqueous electrolyte secondary battery or a combination battery composed of a plurality of these is used, for example, in the case of automobiles, such as hybrid cars, fuel cell cars, electric cars (all automobiles such as automobiles, trucks, buses, etc. (In addition to automobiles, etc.), motorcycles (including motorcycles) and tricycles) can be used to provide a long-life and highly reliable automobile. However, the application is not limited to automobiles. For example, it can be applied to various power sources for moving vehicles such as other vehicles, for example, trains, and power sources for mounting such as uninterruptible power supplies. It is also possible to use as.

  FIG. 8 is a conceptual diagram of a vehicle equipped with an assembled battery.

  As shown in FIG. 8, in order to mount the assembled battery 300 on a vehicle such as the electric vehicle 400, the battery pack 300 is mounted under the seat at the center of the vehicle body of the electric vehicle 400. 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 300 is mounted is not limited to the position under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. The electric vehicle 400 using the assembled battery 300 as described above has high durability and can provide sufficient output even when used for a long period of time. Furthermore, it is possible to provide electric vehicles and hybrid vehicles that are excellent in fuel efficiency and running performance.

  The present invention will be described in further detail using the following examples and comparative examples. However, the technical scope of the present invention is not limited only to the following examples.

Example 1
1. Production of Polymer-Grafted Separator A polyethylene separator as a base material was immersed in a toluene solution of 2-bromoisobutyric acid (6-triethoxysilyl) hexyl, and 2-bromoisobutyric acid (6-triethoxy was deposited on the surface of the separator. Silyl) hexyl was immobilized. The amount of immobilized 2-bromoisobutyric acid (6-triethoxysilyl) hexyl was 10% by mass relative to the separator. Next, this separator was put into toluene, and 1.5 g of acrylic acid was polymerized by an atom transfer radical polymerization method using 2- (4-chlorosulfonylphenyl) ethyltrichlorosilane as a polymerization initiator (polymerization initiator and monomer). The mass ratio is 5:95). The polymerization was carried out in toluene at 60 ° C. for 24 hours to form a graft polymer chain (the graft polymer formed from acrylic acid is also referred to herein as “hydrophilic polymer 1”). The weight average molecular weight of the graft polymer chain was 250,000, and the graft density of the graft polymer was 1.0 chain / nm ² .

2. Electrolyte Layer Fabrication Step Py13-FSI containing 1.0 M LiPF ₆ was used as the electrolyte. An electrolyte layer (thickness 20 μm) was obtained by impregnating the separator with an electrolytic solution at 40 ° C. under reduced pressure.

3. Step of forming positive electrode layer As a positive electrode active material, a solid content of 85% by mass of LiMn ₂ O ₄ (average particle size: 10 μm), 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.

  The positive electrode slurry was applied to one side of a stainless steel foil as a current collector and dried to form a positive electrode layer. Pressing was performed so that the thickness of this positive electrode layer was 36 μm on one side.

4). Formation of negative electrode layer and completion process of bipolar electrode NMP, which is a slurry viscosity adjusting solvent, is used as a negative electrode active material with respect to a solid content of 90% by mass of hard carbon (average particle size: 10 μm) and 10% by mass of PVdF as a binder. An appropriate amount was added to prepare a negative electrode slurry.

  The negative electrode slurry was applied to the surface of the current collector on which one side of the positive electrode layer was formed, on which the positive electrode layer was not formed, and dried to form a negative electrode layer. Pressing was performed so that the thickness of the negative electrode layer was 30 μm on one side. This formed a bipolar electrode in which a positive electrode layer was formed on one side of the current collector and a negative electrode layer was formed on the other side.

  The obtained bipolar electrode was cut into 140 mm × 90 mm, and the peripheral portion of the electrode 10 mm was prepared with a portion where no electrode layer (both positive electrode layer and negative electrode layer) was previously applied. As a result, a bipolar electrode having a 120 mm × 70 mm electrode portion and a 10 mm seal margin in the peripheral portion was produced.

Applying the electrolytic solution (N-methyl-N-propylpyrrolidinium bis (trifluoromethanesulfonyl) imide containing 1.0M LiPF ₆ ) to the entire surface of the positive electrode layer and the negative electrode layer on both sides of the bipolar electrode. Thus, a bipolar electrode infiltrated with electrolyte was completed. Note that the thickness of the positive electrode layer remained 36 μm, and the thickness of the negative electrode layer remained 30 μm.

5). Lamination Step An electrolyte layer was placed on the positive electrode layer of the bipolar electrode obtained above, and a polyethylene film having a width of 12 mm and a thickness of 100 μm was placed around it as a sealing material. After laminating 6 layers of such bipolar electrodes, the sealing material is pressed (heat and pressure) from above and below, and each layer is sealed (press conditions: 0.2 MPa, 160 ° C., 5 s) to seal Part was formed.

  A part (electrode tab: electrode tab: part of a 130 μm × 80 mm 100 μm thick Al plate (electrode current collector plate) that can cover the entire projection surface of the obtained battery element. An electrode current collector (high voltage terminal) having a width of 20 mm was produced. The battery element was sandwiched between and covered with the current collector plate, and was vacuum-sealed with a laminate film containing aluminum as a battery exterior material, whereby both sides of the battery element were pressed and pressurized at atmospheric pressure. Then, a bipolar secondary battery having a five-line structure (a structure in which five cells are connected in series) with improved contact between the electrode current collector plate and the battery element was completed.

(Example 2)
A bipolar secondary battery in the same manner as in Example 1 except that a mixed solvent of Py13-FSI (99% by mass) and vinylene carbonate (1% by mass) as an additive was used as a solvent for the electrolytic solution. Was completed. The weight average molecular weight of the graft polymer chain was 250,000, and the graft density of the graft polymer chain was 1.0 chain / nm ² .

(Example 3)
A bipolar secondary battery was completed in the same manner as in Example 1 except that an aramid resin separator was used as the separator substrate. The weight average molecular weight of the graft polymer chain was 250,000, and the graft density of the graft polymer chain was 1.0 chain / nm ² .

Example 4
A separator made of an aramid resin was used as the separator substrate, and a mixed solvent of Py13-FSI (99% by mass) and vinylene carbonate (1% by mass) as an additive was used as a solvent for the electrolytic solution. Except for these, a bipolar secondary battery was completed in the same manner as in Example 1. The weight average molecular weight of the graft polymer chain was 250,000, and the graft density of the graft polymer chain was 1.0 chain / nm ² .

(Example 5)
The base aramid resin separator is immersed in a toluene solution of 2-bromoisobutyric acid (6-triethoxysilyl) hexyl, and 2-bromoisobutyric acid (6-triethoxysilyl) hexyl is immobilized on the surface of the separator. I let you. The amount of immobilized 2-bromoisobutyric acid (6-triethoxysilyl) hexyl was 10% by mass relative to the separator. Next, this separator is put in toluene, 2- (4-chlorosulfonylphenyl) ethyltrichlorosilane is used as a polymerization initiator, and methacrylic acid (2,2-dimethyl-1,3-dioxolan-4-yl) is atomized. Polymerization was performed by a transfer radical polymerization method. The mass ratio of the polymerization initiator to the monomer was 5:95. The polymerization was carried out in toluene at 60 ° C. for 24 hours, and a graft polymer chain was formed on the separator (the graft polymer formed from methacrylic acid (2,2-dimethyl-1,3-dioxolan-4-yl) (Also referred to as “hydrophilic polymer 2”). The weight average molecular weight of the graft polymer chain was 350,000, and the graft density of the graft polymer was 1.0 chain / nm ² .

  Other than this, a bipolar secondary battery was completed in the same manner as in Example 1.

(Example 6)
A mixed solvent of EMI-TFSI (99% by mass) and vinylene carbonate (1% by mass) as an additive was used as a solvent for the electrolytic solution. Except for this, a bipolar secondary battery was completed in the same manner as in Example 5. The weight average molecular weight of the graft polymer chains 350,000, the graft density of the graft polymer chains was 1.0 chain / nm ^2.

(Example 7)
The base aramid resin separator is immersed in a toluene solution of 2-bromoisobutyric acid (6-triethoxysilyl) hexyl, and 2-bromoisobutyric acid (6-triethoxysilyl) hexyl is immobilized on the surface of the separator. I let you. The amount of immobilized 2-bromoisobutyric acid (6-triethoxysilyl) hexyl was 10% by mass relative to the separator. Next, this separator was put in toluene, and 0.5 g of acrylic acid was polymerized by an atom transfer radical polymerization method using 2- (4-chlorosulfonylphenyl) ethyltrichlorosilane as a polymerization initiator. The mass ratio of the polymerization initiator to the monomer was 5:95. Polymerization was performed in toluene at 60 ° C. for 12 hours, and the polymer chain of hydrophilic polymer 1 was introduced onto the separator. Next, 0.5 g of methacrylic acid (2,2-dimethyl-1,3-dioxolan-4-yl) was polymerized at 60 ° C. for 12 hours, and the polymer chain of hydrophilic polymer 2 was introduced onto the separator. The weight average molecular weight of the graft polymer chain is 210,000, the graft density of the graft polymer is 1.0 chain / nm ² (the graft density of hydrophilic polymer 1 is 0.5 chain / nm ² , the graft density of hydrophilic polymer 2) Was 0.5 chain / nm ² ).

  Moreover, the mixed solvent of Py13-FSI (99 mass%) and the vinylene carbonate (1 mass%) which is an additive was used as a solvent of electrolyte solution.

  A bipolar secondary battery was completed in the same manner as Example 1 except for the above.

(Example 8)
The base aramid resin separator is immersed in a toluene solution of 2-bromoisobutyric acid (6-triethoxysilyl) hexyl, and 2-bromoisobutyric acid (6-triethoxysilyl) hexyl is immobilized on the surface of the separator. I let you. The amount of immobilized 2-bromoisobutyric acid (6-triethoxysilyl) hexyl was 10% by mass relative to the separator. Next, this separator was put in toluene, 2- (4-chlorosulfonylphenyl) ethyltrichlorosilane was used as a polymerization initiator, and methacrylic acid (2,2-dimethyl-1,3-dioxolan-4-yl). 5 g was polymerized by an atom transfer radical polymerization method. The mass ratio of the polymerization initiator to the monomer was 5:95. Polymerization was carried out in toluene at 60 ° C. for 12 hours, and the polymer chain of hydrophilic polymer 2 was introduced onto the separator. Next, benzoyl peroxide as a polymerization initiator and 0.5 g of styrene were added to the reaction system. The mass ratio of the polymerization initiator to the monomer was 5:95. Polymerization was carried out at 60 ° C. for 12 hours, and polystyrene polymer chains were introduced onto the separator. Other than this, a bipolar secondary battery was completed in the same manner as in Example 1. The weight average molecular weight of the graft polymer chain is 180,000, the graft density of the graft polymer is 1.0 chain / nm ² (the graft density of hydrophilic polymer 2 is 0.5 chain / nm ² , and the graft density of polystyrene is 0.00. 5 chains / nm ² ). In the present specification, the graft polymer formed from styrene is also referred to as “hydrophobic polymer 1”.

  Moreover, the mixed solvent of Py13-FSI (99 mass%) and the vinylene carbonate (1 mass%) which is an additive was used as a solvent of electrolyte solution.

  A bipolar secondary battery was completed in the same manner as Example 1 except for the above.

Example 9
The base aramid resin separator is immersed in a toluene solution of 2-bromoisobutyric acid (6-triethoxysilyl) hexyl, and 2-bromoisobutyric acid (6-triethoxysilyl) hexyl is immobilized on the surface of the separator. I let you. The amount of immobilized 2-bromoisobutyric acid (6-triethoxysilyl) hexyl was 10% by mass relative to the separator. Next, this separator was put in toluene, and 0.5 g of acrylic acid was polymerized by an atom transfer radical polymerization method using 2- (4-chlorosulfonylphenyl) ethyltrichlorosilane as a polymerization initiator. The mass ratio of the polymerization initiator to the monomer was 5:95. Polymerization was performed in toluene at 60 ° C. for 12 hours, and the polymer chain of hydrophilic polymer 1 was introduced onto the separator. Subsequently, 2- (4-chlorosulfonylphenyl) ethyltrichlorosilane which is a polymerization initiator and 0.5 g of methacrylic acid (2,2-dimethyl-1,3-dioxolan-4-yl) were added to the reaction system. . The mass ratio of the polymerization initiator to the monomer was 5:95. Polymerization was carried out at 60 ° C. for 12 hours, and the polymer chain of hydrophilic polymer 2 was introduced so that the polymer chain of hydrophilic polymer 1 was elongated. The weight average molecular weight of the graft polymer chain was 240,000, and the graft density of the graft polymer was 1.0 chain / nm ² .

  Moreover, the mixed solvent of Py13-FSI (99 mass%) and the vinylene carbonate (1 mass%) which is an additive was used as a solvent of electrolyte solution.

  A bipolar secondary battery was completed in the same manner as Example 1 except for the above.

(Example 10)
A bipolar secondary battery was prepared in the same manner as in Example 9 except that methacrylic acid (2,2-dimethyl-1,3-dioxolan-4-yl) was polymerized first and acrylic acid was polymerized later. Completed. The weight average molecular weight of the graft polymer chain was 220,000, and the graft density of the graft polymer chain was 1.0 chain / nm ² .

(Example 11)
The base aramid resin separator is immersed in a toluene solution of 2-bromoisobutyric acid (6-triethoxysilyl) hexyl, and 2-bromoisobutyric acid (6-triethoxysilyl) hexyl is immobilized on the surface of the separator. I let you. The amount of immobilized 2-bromoisobutyric acid (6-triethoxysilyl) hexyl was 10% by mass relative to the separator. Next, this separator was put in toluene, benzoyl peroxide was used as a polymerization initiator, and styrene was polymerized by an atom transfer radical polymerization method (mass ratio of polymerization initiator to monomer was 5:95). Polymerization was carried out in toluene at 60 ° C. for 12 hours, and the polymer chain of hydrophilic polymer 2 was introduced onto the separator. Next, 2- (4-chlorosulfonylphenyl) ethyltrichlorosilane, which is a polymerization initiator, and 0.5 g of acrylic acid were added to the reaction system. The mass ratio of the polymerization initiator to the monomer was 5:95. The polymerization was carried out in toluene at 60 ° C. for 12 hours, and the polymer chain of the hydrophilic polymer 1 was introduced so as to extend the polymer chain of the hydrophobic polymer 1. The weight average molecular weight of the graft polymer chain was 160,000, and the graft density of the graft polymer was 1.0 chain / nm ² .

  Moreover, the mixed solvent of Py13-FSI (99 mass%) and the vinylene carbonate (1 mass%) which is an additive was used as a solvent of electrolyte solution.

  A bipolar secondary battery was completed in the same manner as Example 1 except for the above.

(Example 12)
A bipolar secondary battery was completed in the same manner as in Example 1 except that a silicone-dispersed polyethylene separator was used as the separator substrate. The weight average molecular weight of the graft polymer chain was 250,000, and the graft density of the graft polymer chain was 1.0 chain / nm ² .

(Example 13)
A separator made of silicone-dispersed polyethylene was used as the separator substrate, and a mixed solvent of Py13-FSI (99% by mass) and vinylene carbonate (1% by mass) as an additive was used as a solvent for the electrolytic solution. Except for these, a bipolar secondary battery was completed in the same manner as in Example 1. The weight average molecular weight of the graft polymer chain was 250,000, and the graft density of the graft polymer chain was 1.0 chain / nm ² .

(Example 14)
The amount of acrylic acid used is 0.75 g, the polymerization time of acrylic acid is 15 hours, the solvent of the electrolyte solution is Py13-FSI (99% by mass) and vinylene carbonate (1% by mass) as an additive. A mixed solvent was used. Except for these, a bipolar secondary battery was completed in the same manner as in Example 1. The weight average molecular weight of the graft polymer chain was 250,000, and the graft density of the graft polymer chain was 0.5 chain / nm ² .

(Example 15)
The amount of acrylic acid used is 0.15 g, the polymerization time of acrylic acid is 4 hours, and Py13-FSI (99% by mass) and vinylene carbonate (1% by mass) as an additive are used as a solvent for the electrolytic solution. A mixed solvent was used. Except for these, a bipolar secondary battery was completed in the same manner as in Example 1. The weight average molecular weight of the graft polymer chain was 250,000, and the graft density of the graft polymer chain was 0.1 chain / nm ² .

(Example 16)
The amount of acrylic acid used is 0.015 g, the polymerization time of acrylic acid is 2 hours, the solvent of the electrolytic solution is Py13-FSI (99% by mass) and vinylene carbonate (1% by mass) as an additive. A mixed solvent was used. Except for these, a bipolar secondary battery was completed in the same manner as in Example 1. The weight average molecular weight of the graft polymer chain was 250,000, and the graft density of the graft polymer chain was 0.01 chain / nm ² .

(Example 17)
A polyethylene separator was used as the separator substrate, the amount of acrylic acid used was 0.012 g, and the polymerization time of acrylic acid was 30 minutes. Moreover, the mixed solvent of Py13-FSI (99 mass%) and the vinylene carbonate (1 mass%) which is an additive was used as a solvent of electrolyte solution. Except for these, a bipolar secondary battery was completed in the same manner as in Example 1. The weight average molecular weight of the graft polymer chain was 250,000, and the graft density of the graft polymer chain was 0.008 chain / nm ² .

(Example 18)
The base aramid resin separator is immersed in a toluene solution of 2-bromoisobutyric acid (6-triethoxysilyl) hexyl, and 2-bromoisobutyric acid (6-triethoxysilyl) hexyl is immobilized on the surface of the separator. I let you. The amount of immobilized 2-bromoisobutyric acid (6-triethoxysilyl) hexyl was 10% by mass relative to the separator. Next, this separator was put into toluene, and 2- (4-chlorosulfonylphenyl) ethyltrichlorosilane was used as a polymerization initiator, and 0.5 g of acrylic acid was polymerized by an atom transfer radical polymerization method (polymerization initiator and monomer). The mass ratio is 5:95). Polymerization was carried out in toluene at 60 ° C. for 12 hours, and the polymer chain of hydrophilic polymer 1 was introduced onto the separator. Next, benzoyl peroxide as a polymerization initiator and 0.5 g of styrene were added to the reaction system (mass ratio of polymerization initiator to monomer was 5:95). The polymerization was carried out in toluene at 60 ° C. for 12 hours, and the polymer chain of the hydrophobic polymer 1 was introduced so that the polymer chain of the hydrophilic polymer 1 was elongated. The weight average molecular weight of the graft polymer chain was 170,000, and the graft density of the graft polymer was 1.0 chain / nm ² .

  Moreover, the mixed solvent of Py13-FSI (99 mass%) and the vinylene carbonate (1 mass%) which is an additive was used as a solvent of electrolyte solution.

  Other than this, a bipolar secondary battery was completed in the same manner as in Example 1.

(Comparative Example 1)
A bipolar secondary battery was completed in the same manner as in Example 1 except that a polyethylene separator having no graft polymer chain was used.

(Comparative Example 2)
A bipolar secondary battery was completed in the same manner as in Example 2 except that a silicone-dispersed polyethylene separator in which no graft polymer chain was formed was used.

(Comparative Example 3)
A bipolar secondary battery was completed in the same manner as in Example 3 except that an aramid resin separator having no graft polymer chain was used.

(Comparative Example 4)
The base aramid resin separator is immersed in a toluene solution of 2-bromoisobutyric acid (6-triethoxysilyl) hexyl, and 2-bromoisobutyric acid (6-triethoxysilyl) hexyl is immobilized on the surface of the separator. I let you. The amount of immobilized 2-bromoisobutyric acid (6-triethoxysilyl) hexyl was 10% by mass relative to the separator. Next, this separator was put into toluene, benzoyl peroxide was used as a polymerization initiator, and 0.5 g of styrene was polymerized by an atom transfer radical polymerization method (mass ratio of polymerization initiator to monomer was 5:95). The polymerization was carried out in toluene at 60 ° C. for 12 hours, and the polymer chain of the hydrophobic polymer 1 was introduced onto the separator. The weight average molecular weight of the graft polymer chain was 150,000, and the graft density of the graft polymer was 1.0 chain / nm ² .

  A bipolar secondary battery was completed in the same manner as Example 1 except for the above.

(Comparative Example 5)
The base aramid resin separator is immersed in a toluene solution of 2-bromoisobutyric acid (6-triethoxysilyl) hexyl, and 2-bromoisobutyric acid (6-triethoxysilyl) hexyl is immobilized on the surface of the separator. I let you. The amount of immobilized 2-bromoisobutyric acid (6-triethoxysilyl) hexyl was 10% by mass relative to the separator. Next, this separator was put into toluene, benzoyl peroxide was used as a polymerization initiator, and 0.5 g of styrene was polymerized by an atom transfer radical polymerization method (mass ratio of polymerization initiator to monomer was 5:95). The polymerization was carried out in toluene at 60 ° C. for 12 hours, and the polymer chain of the hydrophobic polymer 1 was introduced onto the separator. Next, 0.5 g of tetrafluoroethylene was polymerized at 60 ° C. for 12 hours, and a polymer chain of polytetrafluoroethylene was introduced onto the separator. The weight average molecular weight of the graft polymer chain is 130,000, the graft density of the graft polymer is 1.0 chain / nm ² (the graft density of hydrophilic polymer 2 is 0.5 chain / nm ² , the graft density of polytetrafluoroethylene Was 0.5 chain / nm ² ). In the present specification, a graft polymer (polytetrafluoroethylene) formed from tetrafluoroethylene is also referred to as “hydrophobic polymer 2”.

  Moreover, the mixed solvent of Py13-FSI (99 mass%) and the vinylene carbonate (1 mass%) which is an additive was used as a solvent of electrolyte solution.

  A bipolar secondary battery was completed in the same manner as Example 1 except for the above.

(Comparative Example 6)
The base aramid resin separator is immersed in a toluene solution of 2-bromoisobutyric acid (6-triethoxysilyl) hexyl, and 2-bromoisobutyric acid (6-triethoxysilyl) hexyl is immobilized on the surface of the separator. I let you. The amount of immobilized 2-bromoisobutyric acid (6-triethoxysilyl) hexyl was 10% by mass relative to the separator. Next, this separator was put into toluene, benzoyl peroxide was used as a polymerization initiator, and 0.5 g of styrene was polymerized by an atom transfer radical polymerization method (mass ratio of polymerization initiator to monomer was 5:95). The polymerization was carried out in toluene at 60 ° C. for 12 hours, and the polymer chain of the hydrophobic polymer 1 was introduced onto the separator. Next, benzoyl peroxide as a polymerization initiator and 0.5 g of tetrafluoroethylene were added to the reaction system (mass ratio of the polymerization initiator to the monomer was 5:95), and polymerization was performed at 60 ° C. for 12 hours. The polymer chain of the hydrophobic polymer 2 was introduced so that the polymer chain of the hydrophobic polymer 1 was elongated. The weight average molecular weight of the graft polymer chains 130,000, the graft density of the graft polymer was 1.0 chain / nm ^2.

  Moreover, the mixed solvent of Py13-FSI (99 mass%) and the vinylene carbonate (1 mass%) which is an additive was used as a solvent of electrolyte solution.

  A bipolar secondary battery was completed in the same manner as Example 1 except for the above.

(Evaluation)
For the rate characteristics, a relative value was obtained when the value of 0.2 C of a commonly used electrolyte (1.0 M LiPF ₆ , ethylene carbonate (EC) / diethyl carbonate (DEC) = 2/3) was set to 1. As for cycle characteristics, 0.2 C, the discharge capacity at the 20th cycle was measured. The data of the cycle characteristics in Table 1 are relative values when the first discharge capacity is 100%.

  The evaluation results are shown in Table 1 below.

  In the comparison of the types of hydrophilic polymers, since the hydrophilic polymer 2 has stronger hydrophilicity and better electrochemical stability, rate characteristics and cycle characteristics were improved (Examples 4 and 5). Compared with the type of ionic liquid, Py13-FSI has lower viscosity and better electrochemical stability than EMI-TFSI, so that rate characteristics and cycle characteristics are improved (Examples 5 and 6). . Moreover, rate characteristics and cycle characteristics improved as the graft density increased (Example 4, Examples 14 to 17).

  In Example 7, the performance was between Example 4 in which the graft polymer chain was only hydrophilic polymer 1 and Example 5 in which the graft polymer chain was only hydrophilic polymer 2. Moreover, when Example 7 and Example 8 were compared, the performance of Example 7 which does not have a hydrophobic polymer chain was superior.

  Comparing the case where the graft polymer chain has a diblock copolymer structure, the performance was better when the hydrophilic polymer 2 having a strong hydrophilicity was on the side away from the separator (Examples 9 to 11). Furthermore, the performance of the diblock copolymer structure was superior to that of the graft polymer chain having only the homopolymer chain (Examples 7 and 9).

  In the comparison of the presence or absence of the additive, the performance was superior in both rate characteristics and cycle characteristics when the additive was added (Examples 1 to 4 and Examples 12 to 13).

10a, 10b, 50 non-aqueous electrolyte secondary battery,
11 Current collector,
11a The outermost layer current collector on the positive electrode side,
11b The outermost layer current collector on the negative electrode side,
13 positive electrode active material layer,
15 negative electrode active material layer,
17 electrolyte layer,
19 cell layer,
21, 57 power generation element,
23 Bipolar electrode,
25 positive current collector,
27 negative current collector,
29 Laminated film,
31 seal part,
40a, 40b, 40c separators,
41a, 41b, 41c solvent diffusion layer,
42, 43 Graft polymer chain having hydrophilicity,
44 Graft polymer chain having hydrophobicity,
46a, 46b, 46c separator base material,
48 Ionic liquid (electrolyte) with lithium salt,
52 Battery exterior material,
58 positive electrode tab,
59 Negative electrode tab,
250 small battery pack,
300 battery packs,
310 connection jig,
400 Electric car.

Claims (5)

A positive electrode in which a positive electrode active material layer containing a positive electrode active material and an electrolyte is formed on the surface of a current collector;
A non-aqueous electrolyte having a battery element including a single battery layer in which a negative electrode formed by forming a negative electrode active material layer containing a negative electrode active material and an electrolyte on a surface of a current collector, and a separator containing an electrolyte A secondary battery,
The electrolyte includes an ionic liquid and a lithium salt;
A non-aqueous electrolyte secondary battery in which a solvent diffusion layer including a hydrophilic graft polymer chain is formed on the surface of the separator. The nonaqueous electrolyte secondary battery according to claim 1, wherein a graft density of the graft polymer chain is 0.01 to 1 chain / nm ² .   The nonaqueous electrolyte secondary battery according to claim 1 or 2, which is a bipolar type.   The assembled battery with which the nonaqueous electrolyte secondary battery of any one of Claims 1-3 was connected.   The vehicle which mounts the nonaqueous electrolyte secondary battery of any one of Claims 1-3, or the assembled battery of Claim 4 as a motor drive power supply.

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