Solid electrolyte and battery

Abstract

The present application provides a solid electrolyte containing an electrolyte solution containing a lithium salt and a carbonate-based solvent, and metal oxide particles. In the solid electrolyte, the lithium salt is at least one selected from lithium bis(fluorosulfonyl)imide and lithium fluoroborate, the carbonate-based solvent is at least one selected from dimethyl carbonate and propylene carbonate, the molar ratio of the lithium salt to the carbonate-based solvent (lithium salt / carbonate-based solvent) is 1 / 4 or more and 1 / 1 or less, the mass ratio of the electrolyte solution to the metal oxide particles (electrolyte solution / metal oxide particles) is 72 / 28 or more and 93 / 7 or less, and the specific surface area of the metal oxide particles, measured based on the BET method, is 160 m 2 / g or more and 700 m 2 / g or less.

Description

Technical Field

[0001] This invention relates to solid electrolytes and batteries. Background Technology

[0002] Unlike liquid electrolytes, solid electrolytes do not pose a risk of leakage and can form a lightweight and flexible electrolyte membrane. Therefore, applications of solid electrolytes in secondary batteries using lithium-ion batteries are expected. For example, Patent Document 1 proposes a pseudo-solid electrolyte comprising a metal oxide and an ion-conducting material, wherein a specific ion-conducting material is supported on metal oxide particles.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-059432 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the pseudo-solid electrolyte described in Patent Document 1, a mixture of ethylene glycol dimethyl ether (glyme) or N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide and a lithium salt containing lithium bis(fluorosulfonyl)imide is used as the ion-conducting material. This ion-conducting material is an ionic liquid-type electrolyte. However, solid electrolytes using ionic liquid-type electrolytes have insufficient characteristics such as lithium-ion mobility. Therefore, further improvements are needed in the characteristics of solid electrolytes.

[0008] The purpose of this invention is to provide a solid electrolyte with high lithium-ion mobility, high ionic conductivity, and high stability relative to lithium metal, and a battery having the solid electrolyte.

[0009] Methods for solving problems

[0010] According to one aspect of the present invention, a solid electrolyte is provided, comprising an electrolyte containing a lithium salt and a carbonate solvent, and metal oxide particles, wherein the lithium salt is at least one selected from lithium bis(fluorosulfonyl)imide and lithium fluoroborate, the carbonate solvent is at least one selected from dimethyl carbonate and propylene carbonate, the molar ratio of the lithium salt to the carbonate solvent (lithium salt / carbonate solvent) is 1 / 4 or more and 1 / 1 or less, the mass ratio of the electrolyte to the metal oxide particles (electrolyte / metal oxide particles) is 72 / 28 or more and 93 / 7 or less, and the specific surface area of ​​the metal oxide particles, as determined by the BET method, is 160 m². 2 / g or more and 700m 2 / g or less.

[0011] In one embodiment of the solid electrolyte of the invention, a binder is preferably further contained.

[0012] In one embodiment of the solid electrolyte of the present invention, the binder is preferably a resin that is incompatible with the electrolyte.

[0013] In one embodiment of the solid electrolyte of the present invention, the binder is preferably polytetrafluoroethylene.

[0014] In one embodiment of the solid electrolyte of the present invention, the content of the binder is preferably 3 parts by mass or more and 10 parts by mass or less relative to the total mass of the electrolyte and the metal oxide particles of 100 parts by mass.

[0015] In one embodiment of the solid electrolyte of the present invention, the metal oxide particles are preferably silicon dioxide particles.

[0016] In one embodiment of the solid electrolyte of the present invention, the silica particles are preferably dry silica particles.

[0017] According to one aspect of the present invention, a battery having a solid electrolyte comprising one aspect of the present invention described above can be provided.

[0018] According to the present invention, a solid electrolyte with high lithium-ion mobility, high ionic conductivity, and high stability relative to lithium metal, and a battery having the solid electrolyte can be provided. Detailed Implementation

[0019] [Solid electrolyte]

[0020] The present invention will be described below with examples of embodiments. The present invention is not limited to the contents of the embodiments.

[0021] The solid electrolyte of this embodiment contains: an electrolyte comprising a specific lithium salt and a specific carbonate solvent (described later), and metal oxide particles. By setting the molar ratio of the lithium salt to the solvent and the mass ratio of the electrolyte to the metal oxide within specific ranges, and further using metal oxide particles with a specific surface area within a specific range, a solid electrolyte with high lithium-ion mobility, high ionic conductivity, and high stability relative to lithium metal can be obtained. The reason for this can be inferred as follows.

[0022] In the solid electrolyte of this embodiment, at least one of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium fluoroborate (LiBF4) is used as the lithium salt. Additionally, at least one of dimethyl carbonate and propylene carbonate is used as the carbonate solvent. The electrolyte containing these lithium salts and these carbonate solvents exhibits high stability relative to lithium metal. By including a metal oxide with a specific surface area within a specific range at a specific mass ratio relative to the electrolyte, the thixotropic properties (hereinafter, sometimes referred to as thixotropy) of the electrolyte are improved. Therefore, it is possible to achieve film formation of a mixture containing the metal oxide and the electrolyte. Since this film formation is possible, leakage of the electrolyte can be suppressed while simultaneously suppressing the impairment of the ionic conductivity of the electrolyte. Based on the above, it can be deduced that, according to this embodiment, a solid electrolyte with high lithium-ion mobility, high ionic conductivity, and high stability relative to lithium metal (especially high stability relative to lithium metal) can be obtained.

[0023] Electrolyte

[0024] The electrolyte of this embodiment can be obtained by containing a specific lithium salt and a specific carbonate solvent in a specific molar ratio.

[0025] (Lithium salt)

[0026] The lithium salt in this embodiment is selected from at least one of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium fluoroborate (LiBF4). Either lithium bis(fluorosulfonyl)imide or lithium fluoroborate can be used alone, or in combination. In the solid electrolyte, the lithium salt can exist as a lithium metal cation and a counterion of that cation. The solid electrolyte of this embodiment is stabilized relative to lithium metal by using these lithium salts.

[0027] (carbonate solvents)

[0028] The carbonate solvent in this embodiment is at least one selected from dimethyl carbonate (DMC) and propylene carbonate (PC). Either dimethyl carbonate or propylene carbonate can be used alone, or they can be used in combination. Here, the carbonate solvent in this embodiment refers to a compound having a carbonate backbone in its molecular structure.

[0029] (Molar ratio of lithium salt to carbonate solvent)

[0030] In the electrolyte of this embodiment, the molar ratio of lithium salt to carbonate solvent (lithium salt / carbonate solvent) is 1 / 4 or more and 1 / 1 or less. When this molar ratio is 1 / 4 or more, the stability relative to lithium metal is improved. On the other hand, when it is 1 / 1 or less, the lithium salt is more easily soluble in the carbonate solvent. From the viewpoint of stability relative to lithium metal, this molar ratio can be 1 / 3 or more and 1 / 1 or less, or it can be 1 / 2 or more and 1 / 1 or less.

[0031] The electrolyte of this embodiment exhibits excellent stability relative to lithium metal by containing the lithium salt and the carbonate solvent described above in the aforementioned molar ratio. In contrast, although the reason is not yet clear, electrolytes composed of lithium salts other than those described above combined with carbonate solvents other than those described above exhibit reduced stability relative to lithium metal.

[0032] <Metal Oxide Particles>

[0033] The solid electrolyte of this embodiment contains metal oxide particles. In the solid electrolyte of this embodiment, by including an electrolyte and metal oxide particles, the electrolyte is supported on the metal oxide particles. Here, in this embodiment, the supported state means that the electrolyte coats at least a portion of the surface of the metal oxide particles.

[0034] The specific surface area of ​​the metal oxide particles, determined by the BET method, is 160 m². 2 / g or more and 700m 2 The specific surface area (BET method) of the metal oxide particles is less than / g. 2 At concentrations above a certain value (g), thixotropy readily increases, facilitating the formation of films containing mixtures of metal oxide particles and electrolyte (i.e., solid electrolytes). Additionally, the specific surface area (BET method) is 700 m². 2 When the surface area is below a certain value (g), the miscibility with the electrolyte becomes good, facilitating the formation of a solid electrolyte film. From the viewpoint of easier solid electrolyte film formation, the specific surface area (BET method) of the metal oxide particles is preferably 165 m². 2 / g or more, preferably 170m 2 / g or more. Furthermore, from the same perspective, 600m is preferred. 2 / g or less, preferably 520m 2 / g or less. Here, the BET method refers to a method that adsorbs gas molecules (usually nitrogen) onto solid particles and measures the specific surface area of ​​the solid particles based on the amount of gas molecules adsorbed. Specific surface area can be measured using various BET measuring devices.

[0035] The metal oxide particles can be a single type exhibiting the aforementioned specific surface area, or a combination of two or more metal oxide particles with different specific surface areas. The type of metal oxide particles is not particularly limited, but examples include: silicon dioxide particles, aluminum oxide particles, zirconium oxide particles, cerium dioxide particles, magnesium silicate particles, calcium silicate particles, zinc oxide particles, antimony oxide particles, indium oxide particles, tin oxide particles, titanium oxide particles, iron oxide particles, magnesium oxide particles, aluminum hydroxide particles, magnesium hydroxide particles, potassium titanate particles, and barium titanate particles. A single type of these metal oxide particles can be used, or a combination of two or more can be used. From the viewpoint of improved thixotropy, the metal oxide particles are preferably selected from at least one of silicon dioxide particles, aluminum oxide particles, zirconium oxide particles, magnesium oxide particles, and barium titanate particles. From the viewpoint of being lightweight and having a small particle size, the metal oxide particles are preferably silicon dioxide particles.

[0036] When using silica particles as metal oxide particles, either wet silica particles or dry silica particles can be used. Examples of wet silica particles include sedimentation particles obtained by the neutralization reaction of sodium silicate with an inorganic acid, and wet silica particles obtained by the sol-gel method. Examples of dry silica particles include combustion silica particles (gas-phase silica particles) obtained by burning silane compounds, and detonation silica particles obtained by explosively burning metallic silicon powder. When the silica particles are dry silica particles, the mixing of moisture originating from the silica particles can be suppressed, thus easily suppressing electrolyte degradation. Therefore, from the viewpoint of suppressing electrolyte degradation, dry silica particles are preferred, and gas-phase silica particles are more preferred.

[0037] From the viewpoint of facilitating the formation of a solid electrolyte film, the content of metal oxide particles in the solid electrolyte is preferably 68% by mass or more, more preferably 76% by mass or more, relative to the total solid electrolyte content. Furthermore, from the same viewpoint, it is preferably 89% by mass or less, more preferably 86% by mass or less.

[0038] <Mass ratio of electrolyte to metal oxide>

[0039] For the solid electrolyte of this embodiment, the mass ratio of electrolyte to metal oxide particles (electrolyte / metal oxide particles) is 72 / 28 or more and 93 / 7 or less. When this mass ratio is 72 / 28 or more, the mass ratio of metal oxide particles does not become excessive, making it easy to form a solid electrolyte film. When this mass ratio is 93 / 7 or less, the mass ratio of metal oxide particles does not become too low, which can easily lead to an increased thixotropic effect, making it difficult to form a solid electrolyte film. From the viewpoint of making it easier to form a solid electrolyte film, this mass ratio (electrolyte / metal oxide particles) is preferably 75 / 25 or more, more preferably 80 / 20 or more. Furthermore, from the same viewpoint, it is preferably 92 / 8 or less, more preferably 90 / 10 or less.

[0040] <Adhesive>

[0041] From the viewpoint of easily forming a solid electrolyte membrane, the solid electrolyte of this embodiment may include a binder. When a binder is included, the binder content is preferably 3 parts by mass or more and 10 parts by mass or less relative to 100 parts by mass of the total mass of the electrolyte and the metal oxide particles. More preferably, the binder content is 4 parts by mass or more, and even more preferably 7 parts by mass or less.

[0042] The binder in this embodiment is not particularly limited. The binder can be either compatible with the electrolyte or incompatible with it. When the binder is compatible with the electrolyte, it easily leads to an increase in electrolyte viscosity, sometimes resulting in a decrease in ionic conductivity. On the other hand, by making the binder incompatible with the electrolyte, the increase in electrolyte viscosity is suppressed, thus suppressing the effect on the decrease in ionic conductivity. From this viewpoint, it is preferable that the binder is incompatible with the electrolyte. Specific examples of binders include, for instance, fluoropolymers such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), and one or two of these can be used. For the binder, polytetrafluoroethylene is preferred as an binder that is incompatible with the electrolyte. When using polytetrafluoroethylene, it is easy to obtain a solid electrolyte membrane with high heat resistance and flexibility. Solid electrolyte membranes using polytetrafluoroethylene as a binder tend to undergo plastic deformation easily at room temperature.

[0043] The solid electrolyte of this embodiment includes the lithium salt, carbonate solvent, metal oxide, and binder added as needed, as described above. The solid electrolyte of this embodiment may also contain other components without prejudice to the purpose of the invention.

[0044] The method for manufacturing the solid electrolyte of this embodiment is not particularly limited, and may include, for example, a first step of obtaining an electrolyte comprising the lithium metal salt and the carbonate solvent in the aforementioned molar ratio, and a second step of obtaining a mixture comprising the electrolyte and metal oxide particles having the aforementioned specific surface area in the aforementioned mass ratio. In the second step, a binder may be mixed into the mixture comprising the electrolyte and the metal oxide particles as needed. The mixture comprising the electrolyte and the metal oxide particles (and, if necessary, the binder mixture) may then be compression molded, for example, using a mold exhibiting peelability. Through such a process, the solid electrolyte of this embodiment can be obtained.

[0045] The form and composition of the solid electrolyte in this embodiment are not particularly limited. For example, it can be a membrane-like solid electrolyte (i.e., a solid electrolyte membrane). The solid electrolyte membrane preferably has self-supporting properties. A self-supporting solid electrolyte membrane has excellent operability. A self-supporting membrane is one that can be peeled from a support while maintaining its shape and can be operated. For example, a solid electrolyte membrane can be obtained by compression molding a mixture containing electrolyte and metal oxide particles using a mold (such as a fluororesin mold) exhibiting peelability.

[0046] [Battery]

[0047] The battery of this embodiment includes the solid electrolyte of this embodiment. In this embodiment, the solid electrolyte of this embodiment is preferably used as the constituent material of the electrolyte layer of the battery. The battery is composed of an anode, a cathode, and an electrolyte layer disposed between the anode and the cathode. With this configuration, a battery with excellent characteristics can be obtained. Furthermore, as the battery, a secondary battery is preferred, and a lithium-ion secondary battery is more preferred. The various components included in the lithium-ion secondary battery of this embodiment are not particularly limited, and materials commonly used in batteries can be used, for example.

[0048] It should be noted that the present invention is not limited to the above-described embodiments, and all modifications and improvements within the scope of achieving the purpose of the present invention are included in the present invention.

[0049] Example

[0050] The present invention will now be described in more detail with reference to specific embodiments, but the invention is not limited to these embodiments in any way. It should be noted that the measurements or evaluations in the following embodiments and comparative examples were performed using the methods shown below.

[0051] [Determination of Ionic Conductivity of Solid Electrolytes]

[0052] A solid electrolyte membrane was cut into 6mm diameter circles and sandwiched between two stainless steel plates used as electrodes. The impedance between the stainless steel plates was measured. In the measurement, the AC impedance method was used to measure the resistance component by applying an alternating current (10mV) between the electrodes. The ionic conductivity was calculated from the real impedance intercept of the obtained Cole-Cole plot. It should be noted that a potentiostat / galvanostat (VMP-300biologic) was used in the measurement.

[0053] Ionic conductivity (σ) A It can be obtained through the following mathematical expression (F1).

[0054] σ A =L A / (R A ×S A (F1)

[0055] In the mathematical expression (F1), σ A Ionic conductivity (unit: S·cm) -1 ), R A Represents resistance (unit: Ω), S A The cross-sectional area of ​​the solid electrolyte membrane during measurement (unit: cm²) 2 ), L A Indicates the distance between electrodes (unit: cm).

[0056] The measurement temperature was 25℃. Additionally, the ionic conductivity (σ) was calculated based on the results of the complex impedance measurement. A ).

[0057] [Determination of Ionic Conductivity of Electrolyte]

[0058] A circular mesh fabric (α-UX SCREEN 150-035 / 380TW, manufactured by NBCMESHTEC Co., Ltd.) with a diameter of 19 mm was used as a separator. An electrolyte was prepared according to a predetermined formula, combining the lithium salt and carbonate solvent used in each example and comparative example. This electrolyte was impregnated with the separator, and two stainless steel plates with a diameter of 16 mm were sandwiched between them as electrodes. The impedance between the stainless steel plates was measured. In the measurement, an AC impedance method was used, where an alternating current (applied voltage of 10 mV) was applied between the electrodes to measure the resistance component. The ionic conductivity was calculated from the real impedance intercept of the obtained Cole-Cole plot. It should be noted that a potentiostat / galvanometer (manufactured by VMP-300biologic Co., Ltd.) was used in the measurement.

[0059] Ionic conductivity (σ) B It can be obtained from the following mathematical expression (F2).

[0060] σ B =L B / (R B ×S B (F2)

[0061] In the mathematical expression (F2), σ B Ionic conductivity (unit: S·cm) -1 ), R B Represents resistance (unit: Ω), S B The cross-sectional area of ​​the electrode (unit: cm²) 2 ), L B Indicates the distance between electrodes (unit: cm).

[0062] The measurement temperature was 25℃. Additionally, the ionic conductivity (σ) was calculated based on the results of the complex impedance measurement. B ).

[0063] [Stability evaluation relative to lithium metal (dissolution and leaching test)]

[0064] A 19mm diameter circle was cut from a solid electrolyte membrane and sandwiched between two lithium metal electrodes to fabricate a lithium-ion symmetric battery. The lithium metal electrodes were set to a diameter of 16mm. The current density was set to 3mA / cm² at 25°C. 2 Apply oxidation current up to 3 mAh / cm 2 Then, a reduction current is applied until it reaches 3 mAh / cm². 2 This series of operations was repeated for 200 cycles, and the voltage change after 200 cycles was measured. The dissolution and precipitation behavior of lithium metal was investigated based on this voltage measurement. When dissolution / precipitation occurred repeatedly with a constant voltage, without short circuits or other abnormalities, stability with lithium metal was confirmed. The number of cycles in which the operation was performed at a potential within ±30% of the initial cycle voltage was defined as the stable operating cycle number, and the stability of each example with respect to lithium metal was compared.

[0065] [Lithium-ion mobility measurement]

[0066] The obtained solid electrolyte membrane was cut into 6mm diameter circles, and two lithium plates were sandwiched between them as electrodes to fabricate a battery. The battery was then connected to a potentiostat / galvanostat (VMP-300biologic) and incubated at 25°C for at least 2 hours before measurements were taken. In the measurements, complex impedance was first measured to calculate the resistance value (R0), and then a DC polarization measurement was performed by applying a 30mV voltage. The initial current value (I0) and the steady-state current value (Ist) when the current value reached a constant value were measured. S After confirming the stable current, a complex impedance measurement was performed again, and the resistance value (R) was calculated.S The lithium-ion mobility (t) was calculated using the following mathematical formula (F3) (Evans formula). + ).

[0067] t + =Is(ΔV-I0×R0) / I0(ΔV-I S ×R S (F3)

[0068] In the mathematical formula (F3), ΔV represents the applied voltage, and R0 and R... S I0 and I S Same as above.

[0069] [Example 1]

[0070] First, lithium bis(fluorosulfonyl)imide (LiFSI) was prepared as a lithium salt. Dimethyl carbonate (DMC) was prepared as a carbonate solvent. Fumed silica particles (AEROSIL 380, NIPPON AEROSIL Co., Ltd., with a specific surface area of ​​350 m² based on the BET method) were prepared as metal oxide particles. 2 / g-410m 2 / g). Polytetrafluoroethylene (PTFE) was prepared as a binder. It should be noted that the specific surface area is 350 m² / g. 2 / g-410m 2 / g indicates a specific surface area of ​​350m² 2 / g to 410m 2 The range of / g. The same applies to other similar records below.

[0071] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 3, and thoroughly stirred to prepare an electrolyte. Next, the electrolyte and fumed silica particles were weighed to achieve a mass ratio of electrolyte / fumed silica particles = 80 / 20, and thoroughly mixed. Further, 5 parts by mass of polytetrafluoroethylene (PTFE) were added relative to 100 parts by mass of the total electrolyte and fumed silica particles, and thoroughly mixed using an agate mortar. This mixture was then compressed and molded in a fluororesin mold to obtain a solid electrolyte membrane.

[0072] [Example 2]

[0073] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 2, and stirred thoroughly to prepare an electrolyte. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0074] [Example 3]

[0075] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 2. The mixture was stirred thoroughly to prepare an electrolyte. The electrolyte and fumed silica particles were further weighed to achieve a mass ratio of electrolyte / fumed silica particles = 85 / 15. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0076] [Example 4]

[0077] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 2. The mixture was stirred thoroughly to prepare an electrolyte. The electrolyte and fumed silica particles were then weighed to achieve a mass ratio of electrolyte / fumed silica particles = 93 / 7. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0078] [Example 5]

[0079] Lithium fluoroborate (LiBF4) was prepared as a lithium salt.

[0080] Lithium fluoroborate (LiBF4) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiBF4 / DMC = 1 / 3, and stirred thoroughly to prepare an electrolyte. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0081] [Example 6]

[0082] Lithium fluoroborate (LiBF4) was prepared as a lithium salt.

[0083] Lithium fluoroborate (LiBF4) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiBF4 / DMC = 1 / 2, and stirred thoroughly to prepare an electrolyte. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0084] [Example 7]

[0085] Lithium fluoroborate (LiBF4) was prepared as a lithium salt.

[0086] Lithium fluoroborate (LiBF4) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiBF4 / DMC = 1 / 2. The mixture was stirred thoroughly to prepare an electrolyte. The electrolyte and fumed silica particles were then weighed to achieve a mass ratio of electrolyte / fumed silica particles = 93 / 7. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0087] [Example 8]

[0088] Propylene carbonate (PC) was prepared as a carbonate solvent.

[0089] Lithium bis(fluorosulfonyl)imide (LiFSI) and propylene carbonate (PC) were weighed to achieve a molar ratio of LiFSI / PC = 1 / 2, and stirred thoroughly to prepare an electrolyte. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0090] [Example 9]

[0091] As metal oxide particles, fumed silica particles (Airlica F-3, Tokuyama Co., Ltd., with a specific surface area of ​​502 m² based on the BET method) were prepared. 2 / g).

[0092] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 2. The mixture was stirred thoroughly to prepare an electrolyte. The electrolyte and fumed silica particles were then weighed to achieve a mass ratio of electrolyte / fumed silica particles = 80 / 20. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0093] [Example 10]

[0094] As metal oxide particles, fumed silica particles (Airlica F-3, Tokuyama Co., Ltd., with a specific surface area of ​​502 m² based on the BET method) were prepared. 2 / g).

[0095] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 2. The mixture was stirred thoroughly to prepare an electrolyte. The electrolyte and fumed silica particles were then weighed to achieve a mass ratio of electrolyte / fumed silica particles = 90 / 10. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0096] [Example 11]

[0097] As metal oxide particles, fumed silica particles (AEROSIL 200, NIPPONAEROSIL Co., Ltd., with a specific surface area of ​​175 m² based on the BET method) were prepared. 2 / g-225m 2 / g).

[0098] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 2. The mixture was stirred thoroughly to prepare an electrolyte. The electrolyte and fumed silica particles were then weighed to achieve a mass ratio of electrolyte / fumed silica particles = 80 / 20. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0099] [Example 12]

[0100] As metal oxide particles, fumed silica particles (AEROSIL 200, NIPPONAEROSIL Co., Ltd., with a specific surface area of ​​175 m² based on the BET method) were prepared. 2 / g-225m 2 / g).

[0101] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 2. The mixture was stirred thoroughly to prepare an electrolyte. The electrolyte and fumed silica particles were then weighed to achieve a mass ratio of electrolyte / fumed silica particles = 75 / 25. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0102] [Example 13]

[0103] Lithium fluoroborate (LiBF4) was prepared as the lithium salt. Fumed silica particles (AEROSIL 200, NIPPON AEROSIL Co., Ltd., with a specific surface area of ​​175 m² based on the BET method) were prepared as the metal oxide particles. 2 / g-225m 2 / g).

[0104] Lithium fluoroborate (LiBF4) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiBF4 / DMC = 1 / 2. The mixture was stirred thoroughly to prepare an electrolyte. The electrolyte and fumed silica particles were then weighed to achieve a mass ratio of electrolyte / fumed silica particles = 75 / 25. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0105] [Comparative Example 1]

[0106] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 12, and stirred thoroughly to prepare an electrolyte. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0107] [Comparative Example 2]

[0108] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 6, and stirred thoroughly to prepare an electrolyte. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0109] [Comparative Example 3]

[0110] Lithium fluoroborate (LiBF4) was prepared as a lithium salt.

[0111] Lithium fluoroborate (LiBF4) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiBF4 / DMC = 1 / 12, and stirred thoroughly to prepare an electrolyte. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0112] [Comparative Example 4]

[0113] Lithium fluoroborate (LiBF4) was prepared as a lithium salt.

[0114] Lithium fluoroborate (LiBF4) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiBF4 / DMC = 1 / 6, and stirred thoroughly to prepare an electrolyte. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0115] [Comparative Example 5]

[0116] Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) was prepared as a lithium salt.

[0117] Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiTFSI / DMC = 1 / 2, and stirred thoroughly to prepare an electrolyte. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0118] [Comparative Example 6]

[0119] Diethyl carbonate (DEC) was prepared as a carbonate solvent.

[0120] Lithium bis(fluorosulfonyl)imide (LiFSI) and diethyl carbonate (DEC) were weighed to achieve a molar ratio of LiFSI / DEC = 1 / 2, and stirred thoroughly to prepare an electrolyte. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0121] [Comparative Example 7]

[0122] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 2, and thoroughly stirred to prepare the electrolyte. Next, the electrolyte and fumed silica particles were weighed to achieve a mass ratio of electrolyte / fumed silica particles = 70 / 30, and thoroughly mixed. Further, 5 parts by mass of polytetrafluoroethylene (PTFE) were added, and the mixture was thoroughly mixed using an agate mortar. This mixture was then compressed in a fluoropolymer mold, but failed to form a film shape, thus a solid electrolyte membrane could not be obtained.

[0123] [Comparative Example 8]

[0124] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 2, and thoroughly stirred to prepare the electrolyte. Next, the electrolyte and fumed silica particles were weighed to achieve a mass ratio of electrolyte / fumed silica particles = 95 / 5, and thoroughly mixed. Further, 5 parts by mass of polytetrafluoroethylene (PTFE) were added and thoroughly mixed using an agate mortar. This mixture was then compressed in a fluoropolymer mold, but failed to form a film shape, thus failing to obtain a solid electrolyte membrane.

[0125] [Comparative Example 9]

[0126] As metal oxide particles, fumed silica particles (AEROSIL (registered trademark) 130, NIPPONAEROSIL Co., Ltd., with a specific surface area of ​​105 m² based on the BET method) were prepared. 2 / g-155m 2 / g).

[0127] Lithium bis(fluorosulfonyl)imide (LiFSI) and dimethyl carbonate (DMC) were weighed to achieve a molar ratio of LiFSI / DMC = 1 / 2, and stirred thoroughly to prepare the electrolyte. The electrolyte and fumed silica particles were then weighed to achieve a mass ratio of electrolyte / fumed silica particles = 90 / 10, and thoroughly mixed. Next, 5 parts by mass of polytetrafluoroethylene (PTFE) were added and thoroughly mixed using an agate mortar. This mixture was compressed in a fluoropolymer mold, but failed to form a film shape, thus a solid electrolyte membrane could not be obtained.

[0128] [Comparative Example 10]

[0129] Tetraethylene glycol dimethyl ether (G4) was prepared as a carbonate solvent.

[0130] Lithium bis(fluorosulfonyl)imide (LiFSI) and tetraethylene glycol dimethyl ether (G4) were weighed to achieve a molar ratio of LiFSI / G4 = 1 / 1. The mixture was stirred thoroughly to prepare an electrolyte. The electrolyte and fumed silica particles were then weighed to achieve a mass ratio of electrolyte / fumed silica particles = 80 / 20. Otherwise, a solid electrolyte membrane was prepared in the same manner as in Example 1.

[0131] [Evaluation of Solid Electrolytes]

[0132] For the solid electrolyte membranes obtained in Examples 1-13 and Comparative Examples 1-10, the above-described dissolution test, ionic conductivity measurement, and lithium-ion mobility measurement were performed. Additionally, the above-described ionic conductivity measurement of the electrolytes used in each example and comparative example was performed. Regarding Comparative Examples 7, 8, and 9, since a solid electrolyte membrane could not be fabricated, the dissolution test, ionic conductivity measurement, and lithium-ion mobility measurement were not performed. Regarding Comparative Examples 1-6, since electrolyte degradation occurred due to the reaction of the solid electrolyte membrane with lithium, the lithium-ion mobility measurement could not be performed.

[0133] The composition of the solid electrolyte membranes for each example is shown in Table 1, and the results of the dissolution test, ionic conductivity measurement, and lithium ion mobility measurement are shown in Table 2. In Table 1, Li salt represents lithium salt, and solvent represents carbonate solvent.

[0134] [Table 1]

[0135]

[0136] [Table 2]

[0137]

[0138] Regarding the results of the dissolution test, it can be seen that each example achieved more than 200 cycles and operated stably for more than 200 cycles. In contrast, the comparative example achieved less than 200 cycles. In the comparative example, the voltage increased with the passage of cycles, and it failed to operate stably.

[0139] Regarding the results of ionic conductivity, it can be seen that each embodiment exhibits ionic conductivity to the same extent as when the electrolyte is immersed in the separator.

[0140] Regarding the results on lithium-ion mobility, it can be seen that the lithium-ion mobility of each embodiment exceeds 0.5. Generally, ionic liquid electrolytes tend to have low lithium-ion mobility. For example, the lithium-ion mobility of ionic liquid electrolytes is less than 0.5. Among them, the lithium-ion mobility of Comparative Example 10 is 0.35. In contrast, the solid electrolytes of each embodiment are superior.

[0141] As can be seen from the above, compared with the solid electrolyte membranes obtained in the comparative examples, the solid electrolyte membranes obtained in the various embodiments exhibit higher lithium-ion mobility, ionic conductivity, and stability relative to lithium metal. This confirms the superior characteristics of the solid electrolyte of the present invention.

Claims

1. A solid electrolyte comprising: Electrolytes containing lithium salts and carbonate solvents, and Silica particles, The lithium salt is at least one selected from lithium bis(fluorosulfonyl)imide and lithium fluoroborate. The carbonate solvent is at least one selected from dimethyl carbonate and propylene carbonate. The molar ratio of the lithium salt to the carbonate solvent is more than 1 / 4 and less than 1 / 1. The mass ratio of the electrolyte to the silica particles is 72 / 28 or higher and 93 / 7 or lower. The specific surface area of ​​the silica particles, as determined by the BET method, is 160 m². 2 / g or more and 700m 2 / g or less.

2. The solid electrolyte according to claim 1, further comprising a binder.

3. The solid electrolyte according to claim 2, wherein, The binder is a resin that is incompatible with the electrolyte.

4. The solid electrolyte according to claim 2 or 3, wherein, The adhesive is polytetrafluoroethylene.

5. The solid electrolyte according to claim 2 or 3, wherein, The content of the binder is 3 parts by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the total mass of the electrolyte and the silica particles.

6. The solid electrolyte according to claim 1, wherein, The silica particles are dry silica particles.

7. A battery comprising the solid electrolyte according to any one of claims 1 to 6.

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