battery

Abstract

To provide a battery which can reduce an irreversible capacity.SOLUTION: The battery sequentially includes a positive electrode layer, an electrolyte layer, and a negative electrode layer. The electrolyte layer includes MeFSA (dimethylsulfamoyl fluoride) and LiFSI (Lithium bis(fluorosulfonyl)imide). The negative electrode layer contains an Si-based active material as a negative electrode active material.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a battery.

Background Art

[0002] Regarding batteries containing an Si-based active material as a negative electrode active material as disclosed in Patent Document 1, various technologies have been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When an Si-based active material as a negative electrode active material is used in a liquid battery, there is room for improvement from the viewpoint of reducing irreversible capacity.

[0005] The present disclosure has been made in view of the above circumstances, and the main object thereof is to provide a battery capable of reducing irreversible capacity.

Means for Solving the Problems

[0006] That is, the present disclosure includes the following aspects. <1> A battery having a positive electrode layer, an electrolyte layer, and a negative electrode layer in this order, wherein the electrolyte layer contains MeFSA (dimethylsulfamoyl fluoride) and LiFSI (lithium bis(fluorosulfonyl)imide), and the negative electrode layer contains an Si-based active material as a negative electrode active material.

[0007] <2> The battery according to <1>, wherein the molar ratio of LiFSI to MeFSA is LiFSI:MeFSA = 1:12 to 1:3.

[0008] <3> The negative electrode active material is porous class rate Si, the battery according to <1> or <2>.

[0009] <4> The negative electrode active material is negative electrode active material particles, The D50 of the negative electrode active material particles is 0.7 μm or less, the battery according to any one of <1> to <3>.

[0010] <5> The negative electrode active material is negative electrode active material particles, The specific surface area of the negative electrode active material particles is 25 to 60 m 2 / g, the battery according to any one of <1> to <4>.

Advantages of the Invention

[0011] The battery of the present disclosure can reduce the irreversible capacity.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments according to the present disclosure will be described. Matters other than those specifically mentioned in this specification and necessary for the implementation of the present disclosure (for example, general configurations and manufacturing processes of batteries that do not characterize the present disclosure) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The present disclosure can be implemented based on the content disclosed in this specification and common general knowledge in the relevant field.

[0014] In the present disclosure, unless otherwise specified, the average particle size (D50) of the particles is the value of the particle size (median diameter) at 50% of the integrated value in the volume-based particle size distribution measured by laser diffraction / scattering particle size distribution measurement.

[0015] In the present disclosure, a battery having a positive electrode layer, an electrolyte layer, and a negative electrode layer in this order, wherein the electrolyte layer contains MeFSA (dimethylsulfamoyl fluoride) and LiFSI (lithium bis(fluorosulfonyl)imide), and the negative electrode layer contains an Si-based active material as a negative electrode active material, is provided.

[0016] SEI (Solid Electrolyte Interphase), which is a film mainly formed by the reduction decomposition of the electrolyte at the interface between the negative electrode of the battery and the electrolyte during charging, partially collapses due to the volume change of the Si-based active material during charge and discharge, and an uneven, thick, and non-uniform SEI is formed on the surface during recharging after the collapse. As a result, the function of the SEI as an interface protection layer deteriorates, and the reduction decomposition of the electrolyte proceeds. Due to the continuous growth of the SEI caused by repeated charge and discharge, the resistance of the battery increases with charge and discharge, resulting in a decrease in the Coulomb efficiency of the battery and a decrease in the capacity retention rate.

[0017] FIG. 1 is a diagram for explaining the difference in the Li metal negative electrode potential between the case of a conventional electrolyte and the case of an electrolyte using MeFSA (dimethylsulfamoyl fluoride) as the solvent of the present disclosure. As shown in FIG. 1, conventionally, the SEI compensated for the gap between the potential window of the electrolyte and the Li metal negative electrode potential. However, in the present disclosure, by bringing the Li metal negative electrode potential closer to the reduction-side potential window of the electrolyte (upshift), the electrode reaction can proceed more easily even without the formation of SEI, and thermodynamically, the reduction decomposition of the electrolyte is suppressed, and the state of the electrolyte becomes stable. The same effect can be obtained even when changing from a Li metal negative electrode to a high-capacity negative electrode (a negative electrode containing an Si-based active material).

[0018] The battery of the present disclosure has a positive electrode, an electrolyte layer, and a negative electrode in this order.

[0019] [Positive electrode] The positive electrode includes a positive electrode layer. The positive electrode optionally includes a positive electrode current collector.

[0020] [Positive electrode layer] The positive electrode layer contains a positive electrode active material, and may contain, as optional components, a solid electrolyte, a conductive material, a binder, and the like.

[0021] Examples of the positive electrode active material include lithium, lithium nickel cobalt aluminum oxide (NCA), LiCoO2, LiNi x Co 1-x O2 (0 < x < 1), Li(Ni 0.8 Co 0.1 Mn 0.1 )O2 (NCM811), LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiMnO2, LiMn2O4, LiNiO2, LiVO2, hetero-element substituted Li-Mn spinel, lithium titanate, lithium metal phosphate, LiCoN, Li2SiO3, and Li4SiO4, etc. Hetero-element substituted Li-Mn spinel includes, for example, LiMn 1.5 Ni 0.5 O4, LiMn 1.5 Al 0.5 O4, LiMn 1.5 Mg 0.5 O4, LiMn 1.5 Co 0.5 O4, LiMn 1.5 Fe 0.5 O4, and LiMn 1.5 Zn 0.5 O4, etc. Lithium titanate is, for example, Li4Ti5O 12 etc. Lithium metal phosphate is, for example, LiFePO4, LiMnPO4, LiCoPO4, and LiNiPO4, etc. The shape of the positive electrode active material is not particularly limited, but it may be particulate (positive electrode active material particles). A coating layer containing a Li-ion conductive oxide may be formed on the surface of the positive electrode active material. This is because the reaction between the positive electrode active material and the solid electrolyte can be suppressed. Examples of the lithium ion conductive oxide include LiNbO3, Li4Ti5O 12 , and Li3PO4, etc. The thickness of the coating layer is, for example, 0.1 nm or more, and may be 1 nm or more. On the other hand, the thickness of the coating layer is, for example, 100 nm or less, and may be 20 nm or less. The coverage rate of the coating layer on the surface of the positive electrode active material is, for example, 70% or more, and may be 90% or more.

[0022] Examples of the solid electrolyte include oxide-based solid electrolytes and sulfide-based solid electrolytes.

[0023] Examples of the sulfide-based solid electrolyte include solid electrolytes containing Li element, M element (M is at least one of P, As, Sb, Si, Ge, Sn, B, Al, Ga, In), and S element. Further, the sulfide-based solid electrolyte may further contain at least one of O element and halogen element. Examples of the sulfide-based solid electrolyte include Li2S-P2S5, Li2S-SiS2, LiX-Li2S-SiS2, LiX-Li2S-P2S5, LiX-Li2O-Li2S-P2S5, LiX-Li2S-P2O5, LiX-Li3PO4-P2S5, and Li3PS4, etc. Note that the description of "Li2S-P2S5" above means a material formed using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions. In addition, "X" in the above LiX represents a halogen element. Examples of the halogen element include F element, Cl element, Br element, and I element, etc. One or more kinds of LiX may be contained in the raw material composition containing LiX. When two or more kinds of LiX are contained, the mixing ratio of the two or more kinds is not particularly limited. The molar ratio of each element in the sulfide-based solid electrolyte can be controlled by adjusting the content of each element in the raw material. Also, the molar ratio and composition of each element in the sulfide-based solid electrolyte can be measured, for example, by ICP emission spectrometry.

[0024] The sulfide-based solid electrolyte may be a sulfide glass, a crystallized sulfide glass (glass-ceramics), or a crystalline material obtained by a solid-phase reaction treatment on a raw material composition. The crystalline state of the sulfide-based solid electrolyte can be confirmed, for example, by performing powder X-ray diffraction measurement using CuKα rays on the sulfide-based solid electrolyte.

[0025] The sulfide glass can be obtained by subjecting a raw material composition (for example, a mixture of Li2S and P2S5) to an amorphous treatment. Examples of the amorphous treatment include mechanical milling.

[0026] The glass-ceramics can be obtained, for example, by heat-treating a sulfide glass. The heat treatment temperature may be a temperature higher than the crystallization temperature (Tc) observed by thermal analysis measurement of the sulfide glass, and is usually 195°C or higher. On the other hand, the upper limit of the heat treatment temperature is not particularly limited. The crystallization temperature (Tc) of the sulfide glass can be measured by differential thermal analysis (DTA). The heat treatment time is not particularly limited as long as the desired crystallinity of the glass-ceramics can be obtained, but is, for example, in the range of 1 minute to 24 hours, and among them, the range of 1 minute to 10 hours can be mentioned. The method of the heat treatment is not particularly limited, and examples thereof include a method using a firing furnace.

[0027] Examples of the oxide-based solid electrolyte include substances having a garnet-type crystal structure containing an Li element, a La element, an A element (A is at least one of Zr, Nb, Ta, and Al), and an O element. Examples of the oxide-based solid electrolyte include Li2O-B2O3-P2O5, Li2O-SiO2, Li2O-B2O3, Li 1.3 Al 0.3 Ti 0.7 (PO4)3, Li5La3Ta2O 12 、Li7La3Zr2O 12 、Li6BaLa2Ta2O 12, Li 3.6 Si 0.6 P 0.4 O4, Li4SiO4, Li3PO4, and Li 3+x PO 4-x N x It may be, for example, (1 ≤ x ≤ 3).

[0028] From the viewpoint of good handleability, the shape of the solid electrolyte may be particulate. Also, the average particle diameter (D50) of the particles of the solid electrolyte is not particularly limited, but the lower limit may be 0.5 μm or more, and the upper limit may be 2 μm or less.

[0029] The content of the solid electrolyte in the positive electrode layer is not particularly limited, but when the total mass of the positive electrode layer is 100% by mass, it may be, for example, in the range of 1% to 80% by mass. The solid electrolyte can be used alone or in combination of two or more. When using two or more solid electrolytes, they may be mixed.

[0030] As the conductive material, known materials can be used, and examples include carbon materials and metal particles. Examples of the carbon material include acetylene black (AB), ketjen black (KB), furnace black, VGCF, carbon nanotubes, and carbon nanofibers. Among them, from the viewpoint of electron conductivity, it may be at least one selected from the group consisting of KB, VGCF, carbon nanotubes, and carbon nanofibers. Examples of the metal particles include particles of Ni, Cu, Fe, and SUS. The content of the conductive material in the positive electrode layer is not particularly limited.

[0031] Examples of the binder include polyamide-based resins, acrylonitrile-butadiene rubber (ABR), butadiene rubber (BR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), and styrene-butadiene rubber (SBR). The content of the binder in the positive electrode layer is not particularly limited.

[0032] The thickness of the positive electrode layer is not particularly limited.

[0033] The positive electrode layer can be formed by a conventionally known method. For example, a positive electrode active material and, if necessary, other components are introduced into a solvent and stirred to prepare a slurry for the positive electrode layer. The positive electrode layer is obtained by applying the slurry for the positive electrode layer onto one surface of a support such as a positive electrode current collector and drying it. Examples of the solvent include butyl acetate, butyl butyrate, heptane, and N-methyl-2-pyrrolidone. The method of applying the slurry for the positive electrode layer onto one surface of a support such as a positive electrode current collector is not particularly limited, and examples include a doctor blade method, a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a gravure coating method, and a screen printing method. As the support, those having self-supporting properties can be appropriately selected and used, and there is no particular limitation. For example, metal foils such as Cu and Al can be used.

[0034] [Positive electrode current collector] As the positive electrode current collector, known metals that can be used as a current collector of a battery can be used. Examples of such metals include metal materials containing one or more elements selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Co, Cr, Zn, Ge, and In. Examples of the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. The form of the positive electrode current collector is not particularly limited, and it can be in various forms such as a foil shape and a mesh shape.

[0035] [Electrolyte layer] The electrolyte layer contains an electrolytic solution containing MeFSA (dimethylsulfamoyl fluoride) represented by the following formula (1) as a solvent and LiFSI (lithium bis(fluorosulfonyl)imide) represented by the following formula (2) as an electrolyte salt.

[0036] [Chemistry]

[0037] [Chemistry]

[0038] The molar ratio of LiFSI to MeFSA may be LiFSI:MeFSA = 1:12 to 1:3. The electrolyte layer may hold an electrolytic solution and may have a separator or the like for preventing contact between the positive electrode layer and the negative electrode layer. The thickness of the electrolyte layer is not particularly limited, and may be, for example, 0.1 μm or more or 1 μm or more, and may also be 2 mm or less or 1 mm or less. Examples of the separator include those made of resins such as polyethylene (PE), polypropylene (PP), polyester, and polyamide. The separator may have a single-layer structure or a multi-layer structure. Examples of the multi-layer structure separator include a separator having a two-layer structure of PE / PP, or a separator having a three-layer structure of PP / PE / PP or PE / PP / PE. The separator may be made of a non-woven fabric such as a cellulose non-woven fabric, a resin non-woven fabric, or a glass fiber non-woven fabric.

[0039] [Negative electrode] The negative electrode includes a negative electrode layer. The negative electrode may include a negative electrode current collector as needed.

[0040] [Negative electrode layer] The negative electrode layer contains an Si-based active material as the negative electrode active material, and may contain the above conductive material, the above binder, etc. as needed. The Si-based active material may be, for example, elemental Si, Si oxide, Si-C composite, Si alloy, etc. The Si-based active material may be porous Si. The Si-based active material may be diamond-type crystalline Si, clathrate Si, amorphous Si, etc., and may be porous clathrate Si. The clathrate Si may be of clathrate type I or clathrate type II. The negative electrode active material may be negative electrode active material particles. The average particle diameter D50 of the negative electrode active material particles may be 0.5 μm or more, may be 2.6 μm or less, and may be 0.7 μm or less. The specific surface area of the negative electrode active material particles is 1 m 2 / g or more, may be 25 m 2 / g or more, and may be 60 m 2 / g or less, and may be 33 m 2 / g or less.

[0041] The thickness of the negative electrode layer is not particularly limited.

[0042] [Negative electrode current collector] Examples of the material of the negative electrode current collector include SUS, copper, nickel, etc. Examples of the form of the negative electrode current collector include foil shape and plate shape, etc. The planar shape of the negative electrode current collector is not particularly limited, and examples thereof include circular shape, elliptical shape, rectangular shape, and any polygonal shape, etc. Also, the thickness of the negative electrode current collector varies depending on the shape, but may be, for example, in the range of 1 μm to 50 μm, and may be in the range of 5 μm to 20 μm.

[0043] The battery may be provided with an exterior body that houses a positive electrode layer, a negative electrode layer, an electrolyte layer, etc. as necessary. The material of the exterior body is not particularly limited as long as it is stable to the electrolyte, and examples thereof include resins such as polypropylene, polyethylene, and acrylic resin.

[0044] Examples of the shape of the battery include coin type, laminate type, cylindrical type, and square type, etc.

[0045] The battery may be a primary battery or a secondary battery. Examples of the applications of the battery include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles. Among them, it may be used as a driving power source for a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), or a battery electric vehicle (BEV). Further, the battery may be used as a power source for a moving body other than a vehicle (e.g., railway, ship, aircraft), and may also be used as a power source for electric products such as information processing devices.

Examples

[0046] (Reference Experimental Examples 1 to 5) [Electrolyte] In Reference Experimental Example 1, a first electrolyte solution containing LiFSI as an electrolyte salt and MeFSA as a solvent at a molar ratio of LiFSI:MeFSA = 1:12 was used. In Reference Experimental Example 2, a second electrolyte solution containing LiFSI as an electrolyte salt and MeFSA as a solvent at a molar ratio of LiFSI:MeFSA = 1:8 was used. In Reference Experimental Example 3, a third electrolyte solution containing LiFSI as an electrolyte salt and MeFSA as a solvent at a molar ratio of LiFSI:MeFSA = 1:4 was used. In Reference Experimental Example 4, a fourth electrolyte solution containing LiFSI as an electrolyte salt and MeFSA as a solvent at a molar ratio of LiFSI:MeFSA = 1:3 was used. In Reference Experimental Example 5, an electrolyte solution containing 1.2 M of LiPF6 as an electrolyte salt and a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC) as a solvent was used as a conventional electrolyte solution.

[0047] [Measurement of Li Electrode Potential] Using a three-electrode cell, the Li electrode potential when each of the electrolyte solutions of Reference Experimental Examples 1 to 5 was used was measured by the following method. 1 mM of ferrocene (Fc) was added to each of the electrolytes in Reference Experimental Examples 1 to 5, and a three-electrode cell was prepared using platinum for the working electrode, Li metal for the counter electrode and reference electrode. Cyclic voltammetry (CV) measurements were performed in a three-electrode cell in the potential range of 2.5 V to 4 V vs Li / Li + and the average redox potential of ferrocene on the working electrode was measured with respect to Li. The redox potential of ferrocene is almost constant (about 3.2 V vs. Li / Li + ) regardless of the electrolyte concentration and type. Therefore, it is considered that the ferrocene redox potential that varies depending on the electrolyte type is due to the variation of the electrode potential of Li used as the reference electrode depending on the electrolyte type. Therefore, the measured "ferrocene redox potential based on Li" can be rewritten as the "Li electrode potential based on ferrocene", and the Li electrode potential based on ferrocene is shown in Table 1.

[0048] [Calculation of average dissolution and deposition efficiency] Using a two-electrode coin cell, the average dissolution and deposition efficiency of the Li electrode when using each of the electrolytes in Reference Experimental Examples 1 to 5 was calculated by the following method. Using each of the electrolytes in Reference Experimental Examples 1 to 5, a two-electrode coin cell was prepared using a copper foil for the working electrode, Li metal for the counter electrode, and a glass filter for the separator. In the two-electrode coin cell, Li metal was deposited on the copper foil at a current density of 0.5 mAh / cm 2 for 1 hour, and then, with the same current density, Li metal was dissolved until the voltage reached 0.5 V (cut-off voltage). One cycle was defined as this process, and the average dissolution and deposition efficiency of the Li electrode was calculated when this cycle was repeated. In Reference Experimental Example 1, the average dissolution and deposition efficiency was calculated when 14 cycles were performed, in Reference Experimental Example 2, when 19 cycles were performed, and in Reference Experimental Examples 3 to 5, when 20 cycles were performed. The results are shown in Table 1.

[0049]

Table 1

[0050] As shown in Table 1, it can be seen that in Reference Experimental Examples 1 to 4, the Li electrode potential increased and shifted upward compared to Reference Experimental Example 5. Also, since the average dissolution deposition efficiency in Reference Experimental Examples 1 to 4 is improved compared to Reference Experimental Example 5, it can be seen that the reactivity of the Li electrode is increased by using an electrolyte solution containing LiFSI as the electrolyte salt and MeFSA as the solvent.

[0051] (Examples 1 to 12, Comparative Examples 1 to 3) [Fabrication of Half-Cell] In each of Examples 1 to 12 and Comparative Examples 1 to 3, a half-cell was fabricated comprising the following negative electrode layer, negative electrode current collector, counter electrode, and electrolyte solution. A negative electrode layer containing an Si-based active material as a negative electrode active material, a polyamide-based resin as a binder, KB and VGCF as conductive materials in this order at a ratio of 82:12:5:1 (wt%) was prepared. As the polyamide-based resin, a product obtained by thermally curing a polyamic acid solution at a high temperature was used. For each of the Si-based active materials in Examples 1 to 12 and Comparative Examples 1 to 3, those shown in Table 2 were used. The particles of the first diamond-type crystalline Si shown in Table 2 had an average particle size D50 of 2.6 μm and a specific surface area of 1 m 2 / g. The particles of the second diamond-type crystalline Si (nano-sized crystalline Si) shown in Table 2 had an average particle size D50 of 0.5 μm and a specific surface area of 25 m 2 / g. The particles of the porous class rate II-type Si (pcSi) shown in Table 2 had an average particle size D50 of 0.7 μm and a specific surface area of 33 m 2 / g. A Cu foil was used as the negative electrode current collector. Li metal was used as the counter electrode. In Examples 1 to 3, the first electrolyte solution used in Reference Experimental Example 1 was used. In Examples 4 to 6, the second electrolyte solution used in Reference Experimental Example 2 was used. In Examples 7 to 9, the third electrolyte solution used in Reference Experimental Example 3 was used. In Examples 10 to 12, the fourth electrolyte solution used in Reference Experimental Example 4 was used. In Comparative Examples 1 to 3, the conventional electrolytes used in Reference Experimental Example 5 were used.

[0052] [Calculation of Average Coulombic Efficiency over 50 Cycles by Half-Cell] In each of Examples 1 to 12 and Comparative Examples 1 to 3, with a charging capacity standard of 1200 mAh / g, charge and discharge of each half-cell were carried out for 50 cycles under the conditions of a temperature of 25°C and 0.1C, and the average coulombic efficiency of each half-cell was calculated. The results are shown in Table 2. Coulombic efficiency (%) = (discharge capacity / charging capacity) × 100

[0053]

Table 2

[0054] As shown in Table 2, it was confirmed that the average coulombic efficiency of the half-cell improved by 0.1 to 0.6% compared to the conventional electrolyte.

[0055] (Examples 13 to 15, Comparative Examples 4 to 6) [Fabrication of Full Cell] In each of Examples 13 to 15 and Comparative Examples 4 to 6, a full cell equipped with the following negative electrode layer, positive electrode layer, and electrolyte was fabricated. A negative electrode layer containing an Si-based active material as a negative electrode active material, a polyamide-based resin as a binder, KB and VGCF as conductive materials in this order at a ratio of 82:12:5:1 (wt%) was prepared. In Examples 13 to 15 and Comparative Examples 4 to 6, the Si-based active materials shown in Table 3 were used. The first diamond-type crystalline Si, the second diamond-type crystalline Si (nanosize crystalline Si), and porous class rate II-type Si (pcSi) shown in Table 3 are the same as those used in the half-cells shown in Table 2. A positive electrode layer containing NCM811 as a positive electrode active material, PVdF as a binder, and AB as a conductive material in this order at a ratio of 90:5:5 (wt%) was prepared. As a separator, a three-layer separator having micropores of PE / PP / PE was used. In Examples 13 to 15, the third electrolyte solution (LiFSI:MeFSA = 1:4 (molar ratio)) used in Reference Experimental Example 3 was used. In Comparative Examples 4 to 6, the conventional electrolyte solution used in Reference Experimental Example 5 was used. The amount of the electrolyte solution injected into the full cell was 700 μl.

[0056] [Calculation of Discharge Capacity Retention Rate after 100 Cycles with Full Cell] In each of Examples 13 to 15 and Comparative Examples 4 to 6, with a charging capacity specified as 1200 mAh / g, the charge and discharge of each full cell were performed 100 cycles in the range of a temperature of 25°C and a cut-off voltage of 2.5 V - 4.35 V, and the discharge capacity retention rate of each full cell was calculated. For the 1st, 50th, and 100th cycles, the charge and discharge were performed under the condition of 0.1C, and for the 2nd to 49th and 51st to 99th cycles, the charge and discharge were performed under the condition of 1C. The results are shown in Table 3.

[0057]

Table 3

[0058] Figure 2 is a graph showing the initial Coulomb efficiency, average Coulomb efficiency, and discharge capacity retention rate measured in Examples 7 to 9, 13 to 15, and Comparative Examples 1 to 6. As shown in Table 3, it was confirmed that the discharge capacity retention rate after 100 cycles in the full cell was improved by about 2 times compared with the conventional electrolyte solution. As shown in Figure 2, in the conventional electrolyte solution, the discharge capacity retention rate decreases due to an increase in the specific surface area of the Si-based active material, but in the electrolyte solution of the present disclosure, it was confirmed that the irreversible capacity is reduced due to an increase in the specific surface area of the Si-based active material, and the discharge capacity retention rate is improved, showing a tendency opposite to that of the conventional electrolyte solution.

Claims

1. A battery having a positive electrode layer, an electrolyte layer, and a negative electrode layer in this order, wherein the electrolyte layer contains MeFSA (dimethylsulfamoyl fluoride) and LiFSI (lithium bis(fluorosulfonyl)imide), and the negative electrode layer contains a Si-based active material as a negative electrode active material.

2. The battery according to claim 1, wherein the molar ratio of LiFSI to MeFSA is LiFSI:MeFSA = 1:12 to 1:

3.

3. The battery according to claim 1, wherein the negative electrode active material is porous class rate Si.

4. The negative electrode active material is negative electrode active material particles, and the D50 of the negative electrode active material particles is 0.7 μm or less. The battery according to claim 1.

5. The negative electrode active material is negative electrode active material particles, The specific surface area of the negative electrode active material particles is 25 to 60 m ２ / g. The battery according to claim 1.

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