Electrolyte composition and secondary battery
阅读说明:本技术 电解质组合物和二次电池 (Electrolyte composition and secondary battery ) 是由 西村拓也 三国纮挥 于 2018-05-31 设计创作,主要内容包括:本发明公开一种电解质组合物,其含有:一种或两种以上的聚合物、具有疏水性表面的氧化物粒子、电解质盐和离子液体,所述电解质盐为选自由锂盐、钠盐、钙盐和镁盐组成的组中的至少一种。(The invention discloses an electrolyte composition, which contains: one or more than two polymers, oxide particles with hydrophobic surfaces, electrolyte salt and ionic liquid, wherein the electrolyte salt is at least one selected from the group consisting of lithium salt, sodium salt, calcium salt and magnesium salt.)
1. An electrolyte composition comprising: one or more than two polymers, oxide particles with hydrophobic surfaces, electrolyte salt and ionic liquid,
the electrolyte salt is at least one selected from the group consisting of lithium salt, sodium salt, calcium salt and magnesium salt.
2. The electrolyte composition of claim 1, wherein the oxide particles are surface treated with a silicon-containing compound.
3. The electrolyte composition according to claim 2, wherein the silicon-containing compound is at least one selected from the group consisting of an alkoxysilane, an epoxy-containing silane, an amino-containing silane, a (meth) acryl-containing silane, a silazane, and a siloxane.
4. The electrolyte composition according to any one of claims 1 to 3, wherein the oxide particles are selected from the group consisting of SiO2、Al2O3、AlOOH、MgO、CaO、ZrO2、TiO2、Li7La3Zr2O12And BaTiO3At least one particle of the group.
5. The electrolyte composition according to any one of claims 1 to 4, wherein the ionic liquid contains a quaternary ammonium salt selected from the group consisting of linear quaternary phosphonium salts
6. The electrolyte composition according to any one of claims 1 to 5, wherein the ionic liquid contains at least one of anion components represented by the following general formula (A) as an anion component,
N(SO2CmF2m+1)(SO2CnF2n+1)-(A)
m and n each independently represent an integer of 0 to 5.
7. The electrolyte composition of any one of claims 1 to 6, the polymer having a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride.
8. The electrolyte composition according to claim 7, wherein the first structural unit and a second structural unit selected from the group consisting of hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate are contained in the structural units constituting the polymer.
9. The electrolyte composition according to any one of claims 1 to 8, wherein the electrolyte salt is an imide-based lithium salt.
10. A secondary battery is provided with: a positive electrode, a negative electrode and an electrolyte layer,
the electrolyte layer is provided between the positive electrode and the negative electrode, and comprises the electrolyte composition according to any one of claims 1 to 9.
Technical Field
The present invention relates to an electrolyte composition and a secondary battery.
Background
In recent years, due to the spread of portable electronic devices, electric vehicles, and the like, high-performance secondary batteries have been required. Among them, lithium secondary batteries have been attracting attention as power sources for batteries for electric vehicles, batteries for electric power storage, and the like because of their high energy density. Specifically, lithium secondary batteries, which are batteries for electric vehicles, are used in electric vehicles such as zero-emission electric vehicles that do not have an engine mounted thereon, hybrid electric vehicles that have both an engine and a secondary battery mounted thereon, and plug-in hybrid electric vehicles that are charged directly from an electric power system. In addition, lithium secondary batteries, which are batteries for power storage, are used in stationary power storage systems and the like that supply power stored in advance when an emergency occurs in which a power system is shut down.
In order to be used in such a wide range of applications, lithium secondary batteries having higher energy densities are required, and development thereof has been made. In particular, lithium secondary batteries for electric vehicles are required to have high safety in addition to high input/output characteristics and high energy density, and therefore, higher technologies for ensuring safety and the like are required.
Conventionally, as a method for improving the safety of a lithium secondary battery, there are known: a method of making the electrolyte flame retardant by adding a flame retardant, a method of changing the electrolyte to a polymer electrolyte or a gel electrolyte, and the like. In particular, since the gel electrolyte has an ionic conductivity equivalent to that of an electrolyte used in a conventional lithium secondary battery, the amount of free electrolyte can be reduced without deteriorating the battery performance by changing the electrolyte to the gel electrolyte, thereby suppressing the combustion of the electrolyte.
Patent document 1 discloses a gel-like electrolyte layer containing a plasticizer containing a lithium salt, a matrix polymer in which the plasticizer is dispersed, and a fibrous insoluble substance. In the case where the fibrous insoluble matter is contained in the gel electrolyte in an amount of 0.1 wt% or more and 50 wt% or less, the cycle characteristics and the high-temperature storage characteristics of the battery are improved by setting the ratio of the fiber length to the fiber diameter to 10 wt% or more and 3000 or less, setting the fiber length to 10 μm or more and 1cm or less, and setting the fiber diameter to 0.05 μm or more and 50 μm or less.
Disclosure of Invention
Problems to be solved by the invention
However, the conventional gel electrolyte as described above has insufficient conductivity, and when the gel electrolyte is applied to a secondary battery as an electrolyte, for example, the discharge characteristics of the secondary battery may be significantly reduced.
Accordingly, a main object of the present invention is to provide an electrolyte composition capable of producing a secondary battery having excellent discharge characteristics.
Means for solving the problems
A first aspect of the present invention is an electrolyte composition containing: one or more than two polymers, oxide particles with hydrophobic surfaces, electrolyte salt and ionic liquid, wherein the electrolyte salt is at least one selected from the group consisting of lithium salt, sodium salt, calcium salt and magnesium salt.
The oxide particles are preferably surface-treated with a silicon-containing compound. The silicon-containing compound is preferably at least one selected from the group consisting of an alkoxysilane, an epoxysilane-containing silane, an aminosilane-containing silane, a (meth) acryloylsilane-containing silane, a silazane and a siloxane.
The oxide particles are preferably selected from the group consisting of SiO2、Al2O3、AlOOH、MgO、CaO、ZrO2、TiO2、Li7La3Zr2O12And BaTiO3At least one particle of the group.
The ionic liquid preferably contains a quaternary ammonium salt selected from the group consisting of
Cation, piperidineCation, pyrrolidineCation, pyridineCation and imidazoleAt least one of the group consisting of cations as the cationic component.The ionic liquid preferably contains at least one of the anion components represented by the following general formula (a) as an anion component.
N(SO2CmF2m+1)(SO2CnF2n+1)-(A)
[ m and n each independently represents an integer of 0 to 5. ]
The polymer preferably has a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride.
The polymer preferably contains, among the structural units constituting the polymer, a first structural unit and a second structural unit selected from the group consisting of hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate.
The electrolyte salt is preferably an imide lithium salt.
A second aspect of the invention is a secondary battery provided with a positive electrode, a negative electrode, and an electrolyte layer that is provided between the positive electrode and the negative electrode and that includes an electrolyte composition.
Effects of the invention
According to the present invention, an electrolyte composition capable of producing a secondary battery having excellent discharge characteristics can be provided. In addition, according to the present invention, a secondary battery using such an electrolyte composition can be provided.
Drawings
Fig. 1 is a perspective view showing a secondary battery according to embodiment 1.
Fig. 2 is an exploded perspective view showing an embodiment of an electrode group in the secondary battery shown in fig. 1.
Fig. 3 is a schematic cross-sectional view showing one embodiment of an electrode group in the secondary battery shown in fig. 1.
Fig. 4(a) is a schematic cross-sectional view showing an electrolyte sheet according to an embodiment, and (b) is a schematic cross-sectional view showing an electrolyte sheet according to another embodiment.
Fig. 5 is a schematic cross-sectional view showing one embodiment of an electrode group in the secondary battery according to
Detailed Description
Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including steps) are not essential unless otherwise explicitly stated. The sizes of the components in the drawings are conceptual, and the relative relationship between the sizes of the components is not limited to those shown in the drawings.
The numerical values and ranges thereof in this specification do not limit the invention. The numerical range expressed by the term "to" in the present specification means a range including numerical values described before and after the term "to" as a minimum value and a maximum value, respectively. In the numerical ranges recited in the present specification, the upper limit or the lower limit recited in one numerical range may be replaced with the upper limit or the lower limit recited in another numerical range. In the numerical ranges described in the present specification, the upper limit or the lower limit of the numerical range may be replaced with the values shown in the examples.
[ embodiment 1]
Fig. 1 is a perspective view showing a secondary battery according to embodiment 1. As shown in fig. 1, a secondary battery 1 includes an
The battery exterior body 3 may be formed of a laminate film, for example. The laminate film may be, for example, a laminate film in which a resin film such as a polyethylene terephthalate (PET) film, a metal foil such as aluminum, copper, or stainless steel, and a sealant layer such as polypropylene are sequentially laminated.
Fig. 2 is an exploded perspective view showing one embodiment of the
The positive electrode collector 9 may be formed of aluminum, stainless steel, titanium, or the like. Specifically, the positive electrode current collector 9 may be, for example, an aluminum perforated foil, a metal expanded mesh, a foamed metal plate, or the like having holes with a diameter of 0.1 to 10 mm. The positive electrode current collector 9 may be formed of any material other than the above as long as it is not changed by dissolution, oxidation, or the like during use of the battery, and the shape, the production method, or the like thereof are not limited.
The thickness of the positive electrode current collector 9 may be 10 μm or more and 100 μm or less, and is preferably 10 μm or more and 50 μm or less from the viewpoint of reducing the volume of the entire positive electrode, and more preferably 10 μm or more and 20 μm or less from the viewpoint of winding the positive electrode with a small curvature when forming a battery.
In one embodiment, the positive
The positive electrode active material may be a lithium transition metal compound such as a lithium transition metal oxide or a lithium transition metal phosphate.
The lithium transition metal oxide may be, for example, lithium manganate, lithium nickelate, lithium cobaltate, or the like. The lithium transition metal oxide may be one in which a part of transition metals such as Mn, Ni, and Co contained in lithium manganate, lithium nickelate, and lithium cobaltate is substituted with one or two or more kinds of other transition metals or metal elements (typical elements) such as Mg and Al. That is, the lithium transition metal oxide may be LiM1O2Or LiM1O4(M1Comprising at least one transition metal). Specifically, the lithium transition metal oxide may be Li (Co)1/3Ni1/3Mn1/3)O2、LiNi1/2Mn1/2O2、LiNi1/2Mn3/2O4And the like.
From the viewpoint of further improving the energy density, the lithium transition metal oxide is preferably a compound represented by the following formula (1).
LiaNibCocM2 dO2+e(1)
[ in the formula (1), M2Is at least one selected from the group consisting of Al, Mn, Mg and Ca, and a, b, c, d and e are numbers satisfying 0.2. ltoreq. a.ltoreq.1.2, 0.5. ltoreq. b.ltoreq.0.9, 0.1. ltoreq. c.ltoreq.0.4, 0. ltoreq. d.ltoreq.0.2, -0.2. ltoreq. e.ltoreq.0.2, and b + c + d.ltoreq.1, respectively.]
The lithium transition metal phosphate may be LiFePO4、LiMnPO4、LiMnxM3 1-xPO4(0.3≤x≤1,M3Is at least one element selected from the group consisting of Fe, Ni, Co, Ti, Cu, Zn, Mg, and Zr), and the like.
The positive electrode active material may be primary particles without being granulated or may be secondary particles obtained by granulation.
The particle diameter of the positive electrode active material is adjusted to be equal to or less than the thickness of the positive
The average particle diameter of the positive electrode active material is preferably 0.1 μm or more, more preferably 1 μm or more, and further preferably 30 μm or less, more preferably 25 μm or less. The average particle diameter of the positive electrode active material is a particle diameter (D50) when the ratio (volume fraction) of the average particle diameter to the entire volume of the positive electrode active material is 50%. The average particle diameter (D50) of the positive electrode active material was obtained as follows: a suspension obtained by suspending the positive electrode active material in water was measured by a laser light scattering method using a laser scattering type particle size measuring apparatus (e.g., Microtrac).
The content of the positive electrode active material may be 70% by mass or more, 80% by mass or more, or 85% by mass or more, based on the total amount of the positive electrode mixture layer. The content of the positive electrode active material may be 95% by mass or less, 92% by mass or less, or 90% by mass or less, based on the total amount of the positive electrode mixture layer.
The conductive agent is not particularly limited, and may be a carbon material such as graphite, acetylene black, carbon fiber, or carbon nanotube. The conductive agent may be a mixture of two or more of the above carbon materials.
The content of the conductive agent may be 0.1% by mass or more, 1% by mass or more, or 3% by mass or more, based on the total amount of the positive electrode material mixture layer. From the viewpoint of suppressing the increase in volume of the
The binder is not limited as long as it is not decomposed on the surface of the
The content of the binder may be 0.5% by mass or more, 1% by mass or more, or 3% by mass or more, based on the total amount of the positive electrode material mixture layer. The content of the binder may be 20% by mass or less, 15% by mass or less, or 10% by mass or less, based on the total amount of the positive electrode material mixture layer.
The positive
As the ionic liquid, those used in the electrolyte composition described later can be used. The content of the ionic liquid contained in the positive
The electrolyte salt may be dissolved in the ionic liquid contained in the positive
From the viewpoint of further improving the conductivity, the thickness of the positive
The negative electrode
The thickness of the negative electrode
In one embodiment, the negative
As the negative electrode active material, a negative electrode active material commonly used in the field of energy devices can be used. Specific examples of the negative electrode active material include metallic lithium and lithium titanate (Li)4Ti5O12) Lithium alloy or other metal compound, carbon material, metal complex, organic polymer compound, and the like. The negative electrode active material may be a single one of these materials or a mixture of two or more of these materials. Examples of the carbon material include graphite (graphite) such as natural graphite (e.g., flake graphite) and artificial graphite; amorphous carbon, carbon fiber; and carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black and thermal black. The negative electrode active material may be silicon, tin, or a compound containing these elements (oxide, nitride, alloy with other metals) from the viewpoint of obtaining a larger theoretical capacity (for example, 500 to 1500 Ah/kg).
The average particle diameter (D) of the negative electrode active material is determined from the viewpoint of obtaining a balanced negative electrode in which the irreversible capacity increase accompanying the particle diameter reduction is suppressed and the electrolyte salt retention ability is improved50) It is preferably not less than 1 μm, more preferably not less than 5 μm, still more preferably not less than 10 μm, and further preferably not less than 50 μm, more preferably not less than 40 μm, and still more preferably not less than 30 μm.Average particle diameter (D) of negative electrode active material50) By the average particle diameter (D) of the positive electrode active material50) The same method is used for determination.
The content of the negative electrode active material may be greater than or equal to 60 mass%, greater than or equal to 65 mass%, or greater than or equal to 70 mass%, based on the total amount of the negative electrode mixture layer. The content of the negative electrode active material may be 99 mass% or less, 95 mass% or less, or 90 mass% or less, based on the total amount of the negative electrode mixture layer.
The binder and the content thereof may be the same as those in the positive
The negative
The negative
As the ionic liquid, those used in the electrolyte composition described later can be used. The content of the ionic liquid contained in the negative
The same electrolyte salt as that usable for the positive
The thickness of the negative
The
The polymer preferably has a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride.
The structural unit constituting the polymer may include the first structural unit and a second structural unit selected from the group consisting of hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate. That is, the first constitutional unit and the second constitutional unit may be contained in one polymer to constitute a copolymer, or may be contained in different polymers to constitute at least two polymers of a first polymer having the first constitutional unit and a second polymer having the second constitutional unit.
Specifically, the polymer may be polytetrafluoroethylene, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, or the like.
The content of the polymer is preferably 3% by mass or more based on the total amount of the electrolyte composition (electrolyte layer). The content of the polymer is preferably 50% by mass or less, more preferably 40% by mass or less, based on the total amount of the electrolyte composition. The content of the polymer is preferably 3 to 50% by mass or 3 to 40% by mass based on the total amount of the electrolyte composition.
The polymer according to the present embodiment has excellent affinity with the ionic liquid contained in the electrolyte composition, and therefore retains the electrolyte in the ionic liquid. This can suppress leakage of the ionic liquid when a load is applied to the electrolyte composition.
The oxide particles may be, for example, particles of an inorganic oxide. The inorganic oxide may be, for example, an inorganic oxide containing Li, Mg, Al, Si, Ca, Ti, Zr, La, Na, K, Ba, Sr, V, Nb, B, Ge, or the like as a constituent element. The oxide particles are preferably selected from the group consisting of SiO2、Al2O3、AlOOH、MgO、CaO、ZrO2、TiO2、Li7La3Zr2O12And BaTiO3At least one particle of the group. Since the oxide particles have polarity, the dissociation of the electrolyte in the
The oxide particles have a hydrophobic surface. The oxide particles generally have hydroxyl groups on their surfaces, and tend to exhibit hydrophilicity. The oxide particles having a hydrophobic surface have a reduced number of hydroxyl groups on the surface as compared with oxide particles having no hydrophobic surface. Therefore, if oxide particles having a hydrophobic surface are used, then the electrolyte composition contains an ionic liquid (for example, the anion component has N (SO)2F)2 -、N(SO2CF3)2 -Etc.) is hydrophobic, and therefore it is predicted that the affinity of these oxide particles with the ionic liquid will be improved. Therefore, it is considered that the liquid retention of the ionic liquid in the electrolyte layer is further improved, and as a result, the ionic conductivity is further improved.
The oxide particles having a hydrophobic surface can be obtained by, for example, treating oxide particles exhibiting hydrophilicity with a surface treatment agent capable of imparting a hydrophobic surface. That is, the oxide particles having a hydrophobic surface may be oxide particles surface-treated with a surface treatment agent capable of imparting a hydrophobic surface. Examples of the surface treatment agent include silicon-containing compounds.
The oxide particles having a hydrophobic surface may be oxide particles surface-treated with a silicon-containing compound. That is, the oxide particles having a hydrophobic surface may be particles in which silicon atoms of the silicon-containing compound are bonded to the surface of the oxide particles through oxygen atoms. The silicon-containing compound as the surface treatment agent is preferably at least one selected from the group consisting of an alkoxysilane, an epoxy-containing silane, an amino-containing silane, a (meth) acryloyl-containing silane, a silazane, and a siloxane.
The alkoxysilane may be methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethoxydiphenylsilane, n-propyltrimethoxysilane, hexyltrimethoxysilane, tetraethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, n-propyltriethoxysilane, etc.
The epoxy-containing silane can be 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, etc.
The amino-containing silane can be N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, etc.
The (meth) acryloylsilane may be 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, etc. In the present specification, a (meth) acryloyl group means an acryloyl group or a methacryloyl group corresponding thereto.
The silazane may be hexamethyldisilazane or the like.
The siloxane may be silicone oil such as dimethyl siloxane. They may also have a reactive functional group (e.g., carboxyl group, etc.) at one or both of their terminals.
The oxide particles having a hydrophobic surface (surface-treated oxide particles) may be particles produced by a known method or may be commercially available.
The oxide particles may generally include primary particles (particles not constituting secondary particles) in which single particles are integrally formed, as determined from the apparent geometric morphology, and secondary particles formed by aggregation of a plurality of primary particles.
The specific surface area of the oxide particles may be, for example, 2 to 380m2(ii) in terms of/g. If the specific surface area is 2 to 380m2(g), the obtained secondary battery has excellent discharge characteristicsThe tendency is different. From the same viewpoint, the specific surface area of the oxide particles may be 5m or more2A ratio of 10m or more in terms of/g2A number of grams of more than or equal to 15m2A ratio of/g to 20m or more2(ii)/g, or greater than or equal to 30m2(ii) in terms of/g. In addition, the specific surface area of the oxide particles may be 350m or less from the viewpoint of easiness of peeling of the electrolyte layer in the electrolyte sheet from the substrate2(ii) g, less than or equal to 300m2(ii) 250m or less per gram2(ii) g, less than or equal to 200m2(ii)/g, less than or equal to 180m2Per g, less than or equal to 150m2G, 130m or less2A ratio of/g to 100m or less2(ii) 80m or less per g2(ii)/g, or less than or equal to 60m2(ii) in terms of/g. The specific surface area of the oxide particles is the specific surface area of the entire oxide particles including the primary particles and the secondary particles, and is measured by the BET method.
From the viewpoint of further improving the conductivity, the average primary particle diameter of the oxide particles (average primary particle diameter) is preferably 0.005 μm (5nm) or more, more preferably 0.01 μm (10nm) or more, and still more preferably 0.015 μm (15nm) or more. From the viewpoint of making the
The average particle diameter of the oxide particles is preferably 0.005 μm or more, more preferably 0.01 μm or more, and still more preferably 0.03 μm or more. The average particle diameter of the oxide particles is preferably 5 μm or less, more preferably 3 μm or less, and still more preferably 1 μm or less. The average particle diameter of the oxide particles is measured by a laser diffraction method, and corresponds to a particle diameter at which the volume accumulation reaches 50% when a volume accumulation particle size distribution curve is drawn from the small particle diameter side.
The shape of the oxide particles may be, for example, a bulk shape or a substantially spherical shape. From the viewpoint of facilitating the thinning of the
The content of the oxide particles is preferably not less than 5% by mass, more preferably not less than 10% by mass, further preferably not less than 15% by mass, particularly preferably not less than 20% by mass, and further preferably not less than 60% by mass, more preferably not more than 50% by mass, and further preferably not more than 40% by mass, based on the total amount of the electrolyte composition (electrolyte layer).
The electrolyte salt is at least one selected from the group consisting of lithium salt, sodium salt, calcium salt and magnesium salt. The electrolyte salt is a compound for supplying and receiving cations between the
The anion component of the electrolyte salt may be halide ion (I)-、Cl-、Br-Etc.), SCN-、BF4 -、BF3(CF3)-、BF3(C2F5)-、PF6 -、ClO4 -、SbF6 -、N(SO2F)2 -、N(SO2CF3)2 -、N(SO2C2F5)2 -、B(C6H5)4 -、B(O2C2H4)2 -、C(SO2F)3 -、C(SO2CF3)3 -、CF3COO-、CF3SO2O-、C6F5SO2O-、B(O2C2O2)2 -And the like. The anion component of the electrolyte salt is preferably N (SO)2F)2 -、N(SO2CF3)2 -An anion component represented by the formula (A) exemplified as an anion component of an ionic liquid described later, PF6 -、BF4 -、B(O2C2O2)2 -Or ClO4 -。
Hereinafter, the following abbreviations may be used.
[FSI]-:N(SO2F)2 -Bis (fluorosulfonyl) imide anions
[TFSI]-:N(SO2CF3)2 -Bis (trifluoromethanesulfonyl) imide anions
[BOB]-:B(O2C2O2)2 -Bis (oxalato) borate anion
[f3C]-:C(SO2F)3 -Tris (fluorosulfonyl) carbanion
The lithium salt may be selected from the group consisting of LiPF6、LiBF4、Li[FSI]、Li[TFSI]、Li[f3C]、Li[BOB]、LiClO4、LiBF3(CF3)、LiBF3(C2F5)、LiBF3(C3F7)、LiBF3(C4F9)、LiC(SO2CF3)3、CF3SO2OLi、CF3COOLi, and R 'COOLi (R'Is an alkyl group having 1 to 4 carbon atoms, a phenyl group, or a naphthyl group. ) At least one of the group consisting of.
The sodium salt may be selected from NaPF6、NaBF4、Na[FSI]、Na[TFSI]、Na[f3C]、Na[BOB]、NaClO4、NaBF3(CF3)、NaBF3(C2F5)、NaBF3(C3F7)、NaBF3(C4F9)、NaC(SO2CF3)3、CF3SO2ONa、CF3COONa and R 'COONa (R' is an alkyl group having 1 to 4 carbon atoms, a phenyl group or a naphthyl group).
The calcium salt can be selected from Ca (PF)6)2、Ca(BF4)2、Ca[FSI]2、Ca[TFSI]2、Ca[f3C]2、Ca[BOB]2、Ca(ClO4)2、Ca[BF3(CF3)]2、Ca[BF3(C2F5)]2、Ca[BF3(C3F7)]2、Ca[BF3(C4F9)]2、Ca[C(SO2CF3)3]2、(CF3SO2O)2Ca、(CF3COO)2Ca. And (R' COO)2Ca (R' is alkyl with 1-4 carbon atoms, phenyl or naphthyl).
The magnesium salt may be selected from Mg (PF)6)2、Mg(BF4)2、Mg[FSI]2、Mg[TFSI]2、Mg[f3C]2、Mg[BOB]2、Na(ClO4)2、Mg[BF3(CF3)]2、Mg[BF3(C2F5)]2、Mg[BF3(C3F7)]2、Mg[BF3(C4F9)]2、Mg[C(SO2CF3)3]2、(CF3SO3)2Mg、(CF3COO)2Mg, and (R' COO)2Mg (R' is a C1-4 one)Alkyl, phenyl or naphthyl. ) At least one of the group consisting of.
The electrolyte salt is preferably one selected from the group consisting of imide lithium salts, imide sodium salts, imide calcium salts, and imide magnesium salts, and more preferably an imide lithium salt.
The imide-based lithium salt may be Li [ TFSI ]]、Li[FSI]And the like. The imide sodium salt may be Na [ TFSI ]]、Na[FSI]And the like. The imide-based calcium salt may be Ca [ TFSI ]]2、Ca[FSI]2And the like. The imide-based magnesium salt may be Mg [ TFSI ]]2、Mg[FSI]2And the like.
The ionic liquid contains the following anionic component and cationic component. The ionic liquid in the present embodiment is a liquid at-20 ℃ or higher.
The anionic component of the ionic liquid is not particularly limited, and may be Cl-、Br-、I-Halogen anions; BF (BF) generator4 -、N(SO2F)2 -Inorganic anions such as ammonium; b (C)6H5)4 -、CH3SO2O-、CF3SO2O-、N(SO2C4F9)2 -、N(SO2CF3)2 -、N(SO2C2F5)2 -And organic anions and the like.
The anionic component of the ionic liquid preferably contains at least one of the anionic components represented by the following general formula (a).
N(SO2CmF2m+1)(SO2CnF2n+1)-(A)
m and n each independently represent an integer of 0 to 5. m and n may be the same as or different from each other, and are preferably the same as each other.
The anion component represented by the formula (A) may be N (SO)2C4F9)2 -、N(SO2F)2 -、N(SO2CF3)2 -、N(SO2C2F5)2 -。
From the viewpoint of further improving the ionic conductivity at a relatively low viscosity and further improving the charge and discharge characteristics, the anionic component of the ionic liquid is more preferably selected from the group consisting of N (SO)2C4F9)2 -、CF3SO2O-、N(SO2F)2 -、N(SO2CF3)2 -、N(SO2C2F5)2 -At least one member of the group consisting of N (SO) and more preferably N (SO)2F)2 -。
The cationic component of the ionic liquid is not particularly limited, and is preferably selected from the group consisting of linear quaternary ammonium salts
Cation, piperidineCation, pyrrolidineCation, pyridineCation and imidazoleAt least one member of the group consisting of cations.Chain season
The cation is, for example, a compound represented by the following general formula (2).[ solution 1]
[ in the formula (2), R1~R4Each independently represents a chain alkyl group having 1 to 20 carbon atoms or R-O- (CH)2)n -The chain alkoxyalkyl group (R represents a methyl group or an ethyl group, n represents an integer of 1 to 4), and X represents a nitrogen atom or a phosphorus atom. R1~R4The number of carbon atoms of the alkyl group is preferably 1 to 20, more preferably 1 to 10, and still more preferably 1 to 5.]
Piperidine derivatives
The cation is, for example, a nitrogen-containing six-membered cyclic compound represented by the following general formula (3).[ solution 2]
[ in the formula (3), R5And R6Each independently represents an alkyl group having 1 to 20 carbon atoms or R-O- (CH)2)nAn alkoxyalkyl group represented by (R represents a methyl group or an ethyl group, and n represents an integer of 1 to 4). R5And R6The number of carbon atoms of the alkyl group is preferably 1 to 20, more preferably 1 to 10, and still more preferably 1 to 5.]
Pyrrolidine as a therapeutic agent
The cation is, for example, a five-membered ring cyclic compound represented by the following general formula (4).[ solution 3]
[ in the formula (4), R7And R8Each independently represents an alkyl group having 1 to 20 carbon atoms or R-O- (CH)2)nAn alkoxyalkyl group represented by (R represents a methyl group or an ethyl group, and n represents an integer of 1 to 4). R7And R8The number of carbon atoms of the alkyl group is preferably 1 to 20, more preferably 1 to 10, and still more preferably 1 to 5.]
Pyridine compound
The cation is, for example, a compound represented by the general formula (5).[ solution 4]
[ in the formula (5), R9~R13Each independently represents an alkyl group having 1 to 20 carbon atoms, R-O- (CH)2)nAn alkoxyalkyl group represented by the formula (R represents a methyl group or an ethyl group, and n represents an integer of 1 to 4), or a hydrogen atom. R9~R13The number of carbon atoms of the alkyl group is preferably 1 to 20, more preferably 1 to 10, and still more preferably 1 to 5.]
Imidazole
The cation is, for example, a compound represented by the general formula (6).[ solution 5]
[ in the formula (6), R14~R18Each independently represents an alkyl group having 1 to 20 carbon atoms, R-O- (CH)2)nAn alkoxyalkyl group represented by the formula (R represents a methyl group or an ethyl group, and n represents an integer of 1 to 4), or a hydrogen atom. R14~R18The number of carbon atoms of the alkyl group is preferably 1 to 20, more preferably 1 to 10, and still more preferably 1 to 5.]
From the viewpoint of suitably producing the electrolyte layer, the content of the total of the electrolyte salt and the ionic liquid (the ionic liquid in which the electrolyte salt is dissolved) may be 10% by mass or more and 80% by mass or less, based on the total amount of the electrolyte composition (electrolyte layer). From the viewpoint of enabling the lithium secondary battery to be charged and discharged at a high load factor, the content of the ionic liquid is preferably not less than 20% by mass, more preferably not less than 30% by mass, based on the total amount of the electrolyte composition.
From the viewpoint of further improving the charge-discharge characteristics, the molar concentration of the ionic liquid in which the electrolyte salt is dissolved (the amount of the substance of the electrolyte salt per unit volume of the ionic liquid) is preferably not less than 0.5mol/L, more preferably not less than 0.7mol/L, still more preferably not less than 1.0mol/L, preferably not more than 2.0mol/L, more preferably not more than 1.8mol/L, and still more preferably not more than 1.6 mol/L.
The thickness of the
Next, a method for manufacturing the secondary battery 1 will be described. The method for manufacturing the secondary battery 1 according to the present embodiment includes: a 1 st step of forming a positive
In the 1 st step, the
The dispersion medium used in step 1 may be water, 1-methyl-2-pyrrolidone (hereinafter, also referred to as NMP), or the like. The dispersion medium is a compound other than the ionic liquid.
In the 2 nd step, the method for forming the negative
In step 3, in one embodiment, the
The
The
The
The thickness of the
The electrolyte sheet may be continuously manufactured while being wound in a roll shape. In that case, the surface of the
The
From the viewpoint of reducing the volume of the
From the viewpoint of suppressing deterioration in a low-temperature environment and softening in a high-temperature environment, the heat-resistant temperature of the
As for a method of providing the
In the 3 rd step, in another embodiment, the
[ 2 nd embodiment ]
Next, the secondary battery according to
The bipolar electrode 16 includes a bipolar electrode collector 17, a positive
In the bipolar electrode collector 17, the positive electrode surface may preferably be formed of a material having excellent oxidation resistance, and may be formed of aluminum, stainless steel, titanium, or the like. The negative electrode surface of the bipolar electrode collector 17 using graphite or an alloy as a negative electrode active material may be formed of a material that does not form an alloy with lithium, specifically, stainless steel, nickel, iron, titanium, or the like. When different metals are used for the positive electrode surface and the negative electrode surface, the bipolar electrode collector 17 may be a clad material in which different metal foils are laminated. However, when the
The thickness of the bipolar electrode collector 17 may be 10 μm or more and 100 μm or less, and is preferably 10 μm or more and 50 μm or less from the viewpoint of reducing the volume of the entire positive electrode, and more preferably 10 μm or more and 20 μm or less from the viewpoint of winding the bipolar electrode with a small curvature when forming a battery.
Next, a method for manufacturing a secondary battery according to
The 1 st step and the 2 nd step may be the same methods as those of the 1 st step and the 2 nd step in embodiment 1.
In the 3 rd step, the method of forming the positive
In the 4 th step, as a method for providing the
In the 4 th step, the
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