Composite electrolyte, electrolyte for battery, and battery

Abstract

A composite electrolyte includes an inorganic solid electrolyte and a plastic ionic crystal containing alkali metal ions.

Description

Technical Field

[0001] The present disclosure relates to a composite electrolyte, an electrolyte for a battery, and a battery. Background Art

[0002] Lithium ion batteries are used for various purposes because of their advantages such as high operating voltage and high energy density (Patent Document 1). Recently, in the case where problems regarding the safety of existing electrolytes have been attracting attention, solid electrolytes attracting attention as new electrolyte materials are excellent in safety and lithium ion conductivity.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: WO 2013 / 136446 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] However, since solid electrolytes have poor adhesion to electrodes, there are problems that the contact area of the interface is likely to become small and the interface resistance becomes large. In particular, Li 6.6 La 3 Zr 1.6 Ta 0.4 O 12 (LLZT) has high lithium ion conductivity and is expected to be used as an electrolyte for all-solid-state batteries. However, due to the large interface resistance, its high ion conductivity has not been fully utilized effectively for conventional batteries. In addition, the grain boundary resistance of the crystal grain boundaries inside the solid electrolyte is also large, and these problems need to be overcome.

[0008] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide a composite electrolyte capable of reducing the interface resistance, an electrolyte for a battery containing the composite electrolyte, and a battery.

[0009] Means for Solving the Problems

[0010] The present disclosure includes the following embodiments.

[0011] [1] A composite electrolyte comprising an inorganic solid electrolyte and a plastic ionic crystal containing an alkali metal ion.

[0012] [2] The composite electrolyte according to [1], wherein the anion contained in the plastic ionic crystal includes an anion having a -SO 2 - group.

[0013] [3] The composite electrolyte according to [1], wherein at least one of the anions contained in the plastic ionic crystal has a -SO2 NSO 2 -based or -SO 3 -group.

[0014] [4] The composite electrolyte according to [1], wherein the above-mentioned plastic ionic crystal has (FSO 2 ) 2 N - and (CF 3 SO 2 ) 2 N - at least one of them.

[0015] [5] The composite electrolyte according to any one of [1] to [4], further comprising an organic cation,

[0016] at least one of the anions contained in the above-mentioned plastic ionic crystal has -SO 2 NSO 2 -group,

[0017] For the Raman spectrum measured at 25 °C, at least one of the following conditions (1) and (2) is satisfied:

[0018] (1) The Raman shift of the peak corresponding to the S-N-S bending vibration of the anion interacting with the organic cation measured for the above-mentioned composite electrolyte is at a higher wavenumber than the Raman shift of the peak corresponding to the S-N-S bending vibration of the anion measured for the salt of the above-mentioned organic cation and the above-mentioned anion, i.e., the plastic ionic crystal, contained in the above-mentioned composite electrolyte.

[0019] (2) The Raman shift of the peak corresponding to the S-N-S bending vibration of the anion interacting with the alkali metal ion measured for the above-mentioned composite electrolyte is at a higher wavenumber than the Raman shift of the peak corresponding to the S-N-S bending vibration of the anion measured for the salt of the above-mentioned alkali metal ion and the above-mentioned anion contained in the above-mentioned composite electrolyte.

[0020] [6] The composite electrolyte according to any one of [1] to [5], further comprising an organic cation,

[0021] at least one of the anions contained in the above-mentioned plastic ionic crystal has -SO 2 NSO 2 -group,

[0022] For the Raman spectrum measured at 25 °C, the above-mentioned -SO 2The ratio of the area of the peak corresponding to the S-N-S angular vibration of the group interacting with the alkali metal ion and the group interacting with the organic cation in the base (Li+ / Org+) is smaller than the ratio of the area (Li+ / Org+) measured for the salt of the organic cation and the anion, i.e., the plastic ionic crystal, contained in the above composite electrolyte.

[0023] [7] The composite electrolyte according to any one of [1] to [6], wherein the inorganic solid electrolyte contains at least one selected from the group consisting of oxide-based inorganic electrolytes, hydride-based solid electrolytes, and halide-based solid electrolytes.

[0024] [8] The composite electrolyte according to any one of [1] to [7], wherein the inorganic solid electrolyte contains an oxide-based inorganic electrolyte.

[0025] [9] The composite electrolyte according to [8], wherein in the X-ray diffraction pattern obtained by measuring the above composite electrolyte using CuKα radiation at 25 °C, within the range of 2θ of 20° or less, at least one diffraction peak derived from the above oxide-based inorganic solid electrolyte with a half-value width of 0.18° or less is observed.

[0026]

[10] The composite electrolyte according to [8] or [9], wherein the oxide-based inorganic solid electrolyte contains an acid-treated oxide-based inorganic solid electrolyte.

[0027] In the X-ray diffraction pattern obtained by measuring using CuKα radiation at 25 °C before and after the acid treatment, the half-value width of at least one of the diffraction peaks within the range of 2θ of 20° or less observed for the above acid-treated oxide-based inorganic solid electrolyte is 0.8 times or less the half-value width of the diffraction peak from the same crystal plane observed for the oxide-based inorganic solid electrolyte before the acid treatment.

[0028]

[11] The composite electrolyte according to any one of [8] to

[10] , wherein as the above oxide-based inorganic solid electrolyte, the following oxide-based inorganic solid electrolyte is incorporated: in the X-ray diffraction pattern obtained by measuring the above oxide-based inorganic solid electrolyte using CuKα radiation at 25 °C, within the range of 2θ of 20° or less, at least one diffraction peak with a half-value width of 0.18° or less is observed.

[0029]

[12] A battery electrolyte comprising the composite electrolyte according to any one of [1] to

[11] .

[0030]

[13] A battery comprising the battery electrolyte according to

[12] .

[0031] Advantages of the Invention

[0032] According to the present disclosure, a composite electrolyte capable of reducing interfacial resistance, a battery electrolyte containing the composite electrolyte, and a battery can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a graph showing the Nyquist plot of each sample measured in each measurement battery (A).

[0034] Figure 2 It is a graph showing the Nyquist plot measured in each measurement battery (B).

[0035] Figure 3 It is a graph showing the Raman spectrum of each sample.

[0036] Figure 4 It is a graph showing the Raman spectrum of each sample.

[0037] Figure 5 It is a graph showing the Raman spectrum of each sample.

[0038] Figure 6 It is a diffraction pattern showing the result of the powder X-ray diffraction test of LLZT.

[0039] Figure 7 It is the measurement result of LSV measured for Battery 1.

[0040] Figure 8 It is the measurement result of LSV measured for Battery 2.

[0041] Figure 9 It is the measurement result of LSV measured for Battery 3.

[0042] Figure 10 It is a graph showing the result of the cycle test of the battery using the composite electrolyte of Example 2B as the electrolyte.

[0043] Figure 11 It is a graph showing the result of the cycle test of the battery using the electrolyte of Example 1A. DETAILED DESCRIPTION

[0044] The composite electrolyte of the present embodiment contains an inorganic solid electrolyte and a plastic ionic crystal containing alkali metal ions.

[0045] A so-called plastic crystal (also known as a plastic crystal) is a crystal in which the chemical species that make up the crystal exhibit a periodic and ordered arrangement. Although it is a crystal, it is considered that in most cases, the chemical species move randomly at a certain position within the crystal lattice, and their orientations are disordered. Therefore, it tends to have a soft property compared to ionic crystals. A plastic crystal in which the main component of the chemical species that make up the crystal is an ionic species is called a plastic ionic crystal.

[0046] The plastic ionic crystal contained in the composite electrolyte of this embodiment contains an alkali metal ion and an anion. The alkali metal ion can be Li + , Na + , K + , Rb + and Cs + any one of them, but may contain at least one of Li + , Na + and K + , may contain at least one of Li + and Na + , may contain Li + .

[0047] Among the alkali metal ions contained in the composite electrolyte, the proportion of one kind of alkali metal ion can be 80 mol% or more, can be 90 mol% or more, and can be 95 mol% or more. This one kind of alkali metal ion can be Li + , Na + and K + at least one of them, can be Li + and Na + at least one of them, can be Li + .

[0048] As the anion contained in the plastic ionic crystal, F - , Cl - , Br - , I - , ClO 4 - , PF 6 - , BF 4 - , an anion having a -SO 2 - group, etc. The anion may contain an anion having a -SO 2 - group. The plastic ionic crystal may contain one or more anions.

[0049] As the anion having a -SO 2 - group, those having SO4 2- , HSO 3 - , -SO 2 NSO 2 - based anions, anions having -SO 3 - based, etc. As an anion having -SO 2 NSO 2 - based, [(C h F 2h+1 )SO 2 2 N - (h is 0 to 3), [(C h F 2h+1 )SO 2 N - [(C i F 2i+1 )SO 2 (h, i are 0 to 3), etc. Specifically, (FSO 2 ) 2 N - (bis(fluorosulfonyl)amide ion, also referred to as FSA ion below.), (CF 3 SO 2 ) 2 N - (bis(trifluoromethylsulfonyl)amide ion, also referred to as TFSA ion). As an anion having -SO 3 - based, [(C h F 2h+1 )SO 3 - (h is 0 to 3), etc. Specifically, FSO 3 - , CF 3 SO 3 - , etc. The plastic ionic crystal may contain at least one anion selected from the group consisting of [(C h F 2h+1 )SO 2 2 N - , [(C h F 2h+1 )SO 2 N - (C i F 2i+1 )SO 2 and [(C h F 2h+1 )SO 3 - and may contain at least one selected from the group consisting of (FSO​​​​2 ) 2 N - ,(CF 3 SO 2 ) 2 N - 、FSO 3 - , and CF 3 SO 3 - At least one anion in the group consisting of (FSO 2 ) 2 N - and (CF 3 SO 2 ) 2 N - At least one of .

[0050] Plastic ionic crystals may contain cations other than alkali metal ions. As such cations, organic cations may be listed. The organic cation may be a cation containing a nitrogen atom having a positive formal charge (e.g., +1 valence). The organic cation may contain at least one selected from the group consisting of imidazolium cations, pyrrolidinium cations, piperidinium cations, pyridinium cations, quaternary ammonium cations, and quaternary phosphonium cations, and may contain pyrrolidinium cations. Plastic ionic crystals may contain one or more organic cations. As pyrrolidinium cations, N-ethyl-N-methylpyrrolidinium cations may be listed.

[0051] Plastic ion crystals can be obtained, for example, by mixing an alkali metal salt (which may be crystalline) with other plastic ion crystals. As alkali metal salts, alkali metal is set as M, and MF, MCl, MBr, MI, MClO can be listed. 4 、MPF 6 、MBF 4 、M 2 SO 4 、M[(C h F 2h+1 )SO 3 ](h is 0 to 3), M[(C h F 2h+1 )SO 2 ] 2 N(h is 0 to 3), M[(C h F 2h+1 )SO 2 ]N - [(C i F 2i+1 )SO 2 ] (h, i are 0 to 3), etc. One or more alkali metal salts may also be used.

[0052] As other plastic ionic crystals, there is no particular limitation, and plastic crystals containing no alkali metal ions can be cited. Specifically, imidazolium salts, pyrrolidinium salts, piperidinium salts, pyridinium salts, quaternary ammonium salts, quaternary phosphonium salts, etc. can be cited. One or more other plastic ionic crystals can also be used. As the anions contained in the other plastic ionic crystals, the anions exemplified as the anions contained in the plastic ionic crystals of the present embodiment can be cited.

[0053] <Inorganic solid electrolyte>

[0054] As the inorganic solid electrolyte, there is no particular limitation, and it can be an oxide (oxide-based inorganic solid electrolyte), a sulfide (sulfide-based solid electrolyte), a hydride (hydride-based solid electrolyte), a halide (halide-based solid electrolyte), etc. The inorganic solid electrolyte can contain at least one of an alkali metal element and an alkaline earth metal element, and can contain an alkali metal element.

[0055] (Oxide-based inorganic solid electrolyte)

[0056] As the oxide-based inorganic solid electrolyte, for example, perovskite-type oxides, NASICON-type oxides, LISICON-type oxides, garnet-type oxides, etc., and substances obtained by doping other cations or anions into the oxides can be cited.

[0057] As the perovskite-type oxide, Li a La 1-a TiO 3 (0 < a < 1) and other Li-La-Ti-based oxides, Li b La 1-b TaO 3 (0 < b < 1) and other Li-La-Ta-based oxides, Li c La 1-c NbO 3 (0 < c < 1) and other Li-La-Nb-based oxides, etc.

[0058] As the NASICON-type oxide, Li 1+d Al d Ti 2-d (PO 4 ) 3 (0 ≤ d ≤ 1), etc. The NASICON-type oxide is Li m M 1 n M 2 o P p O q (In the formula, M 1is one or more elements selected from the group consisting of B, Al, Ga, In, C, Si, Ge, Sn, Sb, and Se. M 2 is one or more elements selected from the group consisting of Ti, Zr, Ge, In, Ga, Sn, and Al. m, n, o, p, and q are arbitrary positive numbers.) The oxides represented include Li 1+x+y Al x (Ti, Ge) 2-x Si y P 3-y O 12 (0 < x < 2, 0 < y < 3) (LATP), etc.

[0059] As LISICON-type oxides, there are Li 4 M 3 O 4 -Li 3 M 4 O 4 (M 3 is one or more elements selected from the group consisting of Si, Ge, and Ti. M 4 is one or more elements selected from the group consisting of P, As, and V.) The oxides represented, etc.

[0060] As garnet-type oxides, there are Li 7 La 3 Zr 2 O 12 (LLZ), Li 7-a2 La 3 Zr 2-a2 Ta a2 O 12 (LLZT, 0 < a2 < 1 can be, 0.1 < a2 < 0.8 can be, 0.2 < a2 < 0.6) etc. Li-La-Zr-based oxides, etc.

[0061] The oxide-based inorganic solid electrolyte can be a crystalline material or an amorphous material.

[0062] As oxide-based inorganic solid electrolytes, there are Li 6.6 La 3 Zr 1.6 Ta 0.4 O 12 , Li 0.33 La 0.55 TiO 3 etc.

[0063] (Sulfide-based solid electrolyte)

[0064] As sulfide-based solid electrolytes, there are Li2 S-P 2 S 5 compound system, Li 2 S-SiS 2 compound system, Li 2 S-GeS 2 compound system, Li 2 S-B 2 S 3 compound system, Li 2 S-P 2 S 3 compound system, LiI-Si 2 S-P 2 S 5 , LiI-Li 2 S-P 2 O 5 , LiI-Li 3 PO 4 -P 2 S 5 , Li 10 GeP 2 S 12 etc.

[0065] The content of the plastic ionic crystal in the composite electrolyte relative to the total of the inorganic solid electrolyte and the plastic ionic crystal can be 7 to 70% by mass, and can be 10 to 60% by mass.

[0066] The content of the inorganic solid electrolyte in the composite electrolyte relative to the total of the inorganic solid electrolyte and the plastic ionic crystal can be 30 to 93% by mass, and can be 40 to 90% by mass.

[0067] The molar ratio of the alkali metal ion to the anion in the plastic ionic crystal contained in the composite electrolyte is not particularly limited and can be 1 to 95 mol%. The molar ratio of the alkali metal ion to other cations in the plastic ionic crystal contained in the composite electrolyte is not particularly limited and can be 1 to 1900 mol%, and can be 5 to 1000 mol%.

[0068] The composite electrolyte can contain at least one selected from the group consisting of an oxide-based inorganic solid electrolyte, a hydride-based solid electrolyte, and a halide-based solid electrolyte as the inorganic solid electrolyte, and can contain an oxide-based inorganic solid electrolyte.

[0069] The composite electrolyte may contain the following substances as an oxide-based inorganic solid electrolyte: in the X-ray diffraction pattern measured using CuKα radiation at 25 °C, within the range of 2θ of 20° or less, at least one diffraction peak with a half-value width of 0.18° or less is observed. The diffraction peak with a half-value width of 0.18° or less derived from the oxide-based inorganic solid electrolyte may be a diffraction peak observed in the state of being contained in the composite electrolyte, or a diffraction peak observed before being incorporated into the composite electrolyte. Such an oxide-based inorganic solid electrolyte can be obtained by pre-treating the oxide-based inorganic solid electrolyte with an acid. Examples of the acid used in the acid treatment include acids such as hydrochloric acid, sulfuric acid, and nitric acid. The concentration of the acid is not particularly limited, but it is more preferably treated at a relatively high concentration for a short time (e.g., 10 to 60 seconds).

[0070] In addition, the oxide-based inorganic solid electrolyte may also contain an oxide-based inorganic solid electrolyte that satisfies the following conditions. That is, in the X-ray diffraction pattern measured using CuKα radiation at 25 °C before and after the acid treatment, the half-value width of at least one of the diffraction peaks in the range of 2θ of 20° or less observed for the acid-treated oxide-based inorganic solid electrolyte may be 0.8 times or less of the half-value width of the diffraction peak derived from the same crystal plane observed for the oxide-based inorganic solid electrolyte before the acid treatment. The diffraction peak derived from the acid-treated oxide-based inorganic solid electrolyte may be a diffraction peak observed in the state of being contained in the composite electrolyte, or a diffraction peak observed before being incorporated into the composite electrolyte.

[0071] When the composite electrolyte further contains an organic cation and at least one of the anions contained in the plastic ionic crystal has a -SO 2 NSO 2 - group, regarding the Raman spectrum measured for the composite electrolyte at 25 °C, the composite electrolyte may satisfy at least one of the following conditions (1) and (2).

[0072] (1) The Raman shift of the peak corresponding to the S-N-S bending vibration of the anion interacting with the organic cation measured for the composite electrolyte is at a higher wavenumber than the Raman shift of the peak corresponding to the S-N-S bending vibration of the anion measured for the salt of the organic cation and anion, i.e., the plastic ionic crystal, contained in the composite electrolyte. The difference in Raman shift between the peak corresponding to the S-N-S bending vibration of the composite electrolyte and the peak corresponding to the S-N-S bending vibration of the above-mentioned plastic crystal may be 0.5 to 20 cm -1 It may be 1 to 10 cm -1 It may be 1 to 5 cm -1 . In addition, the difference in Raman shift may be 0.5 to 10 cm-1 , it can be 0.5 to 5 cm -1 , it can be 1 to 5 cm -1 .

[0073] (2) The Raman shift of the peak corresponding to the S-N-S angular vibration of the anion interacting with the alkali metal ion measured for the composite electrolyte is at a higher wavenumber compared to the Raman shift of the peak corresponding to the S-N-S angular vibration of the anion measured for the salt of the alkali metal ion and the anion contained in the composite electrolyte. The difference in the Raman shift between the peak corresponding to the S-N-S angular vibration of the composite electrolyte and the peak corresponding to the S-N-S angular vibration of the salt of the alkali metal ion and the anion can be 0.05 to 20 cm -1 , it can be 0.1 to 20 cm -1 , it can be 0.5 to 20 cm -1 , it can be 1 to 10 cm -1 , it can be 1 to 5 cm -1 . In addition, the difference in the Raman shift can be 0.05 to 10 cm -1 , it can be 0.1 to 5 cm -1 .

[0074] Regarding (1), the salt of the organic cation and the anion, i.e., the plastic ionic crystal, contained in the composite electrolyte can contain all the organic cations and anions contained in the composite electrolyte.

[0075] Regarding (2), the salt of the alkali metal ion and the anion contained in the composite electrolyte can contain all the alkali metal ions and anions contained in the composite electrolyte.

[0076] It is known that the peak corresponding to the S-N-S angular vibration in the Raman spectrum of an anion having a -SO 2 NSO 2 - group has different peak positions depending on the cation with which it interacts. That is, it is known that the peak on the low wavenumber side of the Raman spectrum belongs to the anion interacting with the organic cation, and the peak on the high wavenumber side belongs to the anion interacting with the alkali metal ion.

[0077] When the composite electrolyte contains an anion having a -SO 2 NSO 2 - group and an organic cation, for the Raman spectrum measured at 25°C, regarding the composite electrolyte, the -SO 2 NSO 2The ratio of the area of the peak corresponding to the S-N-S bending vibration of the group interacting with the alkali metal ion and the group interacting with the organic cation in the - group (Li+ / Org+) can also be smaller than the ratio of the area (Li+ / Org+) measured for the salt of the organic cation and anion, i.e., the plastic ionic crystal, contained in the composite electrolyte.

[0078] The composite electrolyte of the present embodiment can be used, for example, as a material for electrochemical devices such as capacitors and batteries. As such a material, for example, a material for an electrolyte (solid electrolyte) as a component of a battery, i.e., a battery electrolyte, can be cited. As the battery, batteries that charge and discharge by the movement of alkali metal ions between the positive electrode and the negative electrode, such as lithium-ion batteries and sodium-ion batteries, can be cited. In addition, the composite electrolyte of the present embodiment can be used as an ion-conductive material and can also be contained in the positive electrode or the negative electrode of the battery.

[0079] The composite electrolyte of the present embodiment can also be contained in a composition (electrolyte composition) for forming a battery electrolyte (solid electrolyte). In the electrolyte composition, a conductive aid can be contained in addition to the composite electrolyte. The conductive aid is not particularly limited, and carbon materials can be cited. As the carbon materials, specifically, graphite-based materials such as natural graphite (flake graphite, etc.) and artificial graphite; carbon black-based materials such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and pyrolytic carbon black; carbon fibers; etc. can be cited. The content of the conductive aid in the electrolyte composition can be 10:3 to 10:0.1, and can be 10:2.5 to 10:0.5 in terms of the mass ratio of the composite electrolyte to the conductive aid.

[0080] Hereinafter, the battery of the present embodiment will be described taking a lithium-ion battery as an example. The lithium-ion battery includes a positive electrode, a negative electrode, and an electrolyte (solid electrolyte) disposed between the positive electrode and the negative electrode. The composite electrolyte of the present embodiment can be contained in the electrolyte of the lithium-ion battery.

[0081] The positive electrode of the lithium-ion battery is not particularly limited and can be a positive electrode containing a positive electrode active material and, if necessary, a conductive aid, a binder, etc.

[0082] The positive electrode can be a positive electrode in which a layer containing these materials is formed on a current collector. As the positive electrode active material, for example, a lithium-containing composite metal oxide containing lithium (Li) and at least one transition metal selected from the group consisting of V, Cr, Mn, Fe, Co, Ni, and Cu can be cited. As such a lithium composite metal oxide, for example, LiCoO 2 、LiNiO 2 、LiMn 2 O 4 、Li 2 MnO 3, LiNi x Mn y Co 1-x-y O 2 [0 < x + y < 1]), LiNi x Co y Al 1-x-y O 2 [0 < x + y < 1]), LiCr 0.5 Mn 0.5 O 2 , LiFePO 4 , Li 2 FeP 2 O 7 , LiMnPO 4 , LiFeBO 3 , Li 3 V 2 (PO 4 ) 3 , Li 2 CuO 2 , Li 2 FeSiO 4 , Li 2 MnSiO 4 etc.

[0083] As the negative electrode of the lithium - ion battery, there is no particular limitation, and it can be a negative electrode containing a negative electrode active material and, if necessary, a conductive assistant, a binder, etc. For example, single substances such as Li, Si, P, Sn, Si - Mn, Si - Co, Si - Ni, In, Au, etc., alloys or composites containing these elements, carbon materials such as graphite, substances obtained by inserting lithium ions between the layers of the carbon material, etc. can be cited.

[0084] The material of the current collector is not particularly limited, and it can be a single substance or an alloy of metals such as Cu, Mg, Ti, Fe, Co, Ni, Zn, Al, Ge, In, Au, Pt, Ag, Pd, etc.

[0085] As the solid electrolyte layer, it can have multiple layers. For example, it can also be a structure having a sulfide solid electrolyte layer in addition to the solid electrolyte layer containing the composite electrolyte of the present embodiment. It can also be a structure having a sulfide solid electrolyte layer between the solid electrolyte containing the composite electrolyte of the present embodiment and the negative electrode. As the sulfide solid electrolyte, there is no particular limitation, but for example, Li 6 PS 5 Cl, Li 2 S - PS 5 , Li 10 GeP 2 S 12 , Li 9.6P 3 S 12 、 Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 、 Li 3 PS 4 etc.

[0086] Example

[0087] (Manufacture of Plastic Ionic Crystal)

[0088] (Manufacturing Example 1)

[0089] Lithium bis(trifluoromethylsulfonyl)amide (LiTFSA, manufactured by KISHIDA CHEMICAL CO., LTD.) and [C2C1pyrr][TFSA] (N-ethyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide, manufactured by Kanto Chemical Co., Inc.) as a plastic ionic crystal were mixed at a molar ratio of 5:95 to obtain a mixture. Acetonitrile was added to the obtained mixture to form a homogeneous solution, and the acetonitrile was removed under vacuum to obtain a homogeneous plastic crystal (hereinafter, also referred to as plastic ionic crystal 1 (IPC1)).

[0090] (Manufacturing Example 2)

[0091] Lithium bis(fluorosulfonyl)amide (LiFSA, manufactured by KISHIDA CHEMICAL CO., LTD.) and [C2C1pyrr][FSA] (manufactured by Kanto Chemical Co., Inc.) as a plastic ionic crystal were mixed at a molar ratio of 5:95, and in other respects, plastic ionic crystal 2 (IPC2) was obtained in the same manner as in Manufacturing Example 1.

[0092] (Manufacturing Example 3)

[0093] Lithium bis(fluorosulfonyl)amide (LiFSA, manufactured by KISHIDA CHEMICAL CO., LTD.) and [C2C1pyrr][FSA] (manufactured by Kanto Chemical Co., Inc.) as a plastic ionic crystal were mixed at a molar ratio of 90:10, and in other respects, plastic ionic crystal 3 (IPC3) was obtained in the same manner as in Manufacturing Example 1.

[0094] (Preparation of Inorganic Solid Electrolyte)

[0095] As the inorganic solid electrolyte, LLZT particles (manufactured by Toyoshima Seisakusho Co., Ltd.) were prepared. The inorganic solid electrolyte was immersed in 36 mass% hydrochloric acid for 30 seconds or 5 minutes. Powder X-ray diffraction tests were performed on the samples before acid treatment, after 30 seconds of acid treatment, and after 5 minutes of acid treatment at 25°C. The test conditions were as follows.

[0096] Measurement device: SmalrtLab (manufactured by Rigaku Corporation)

[0097] X-ray generator: CuKα ray source, voltage 40 kV, current 30 mA

[0098] X-ray detector: Silicon strip type high-speed detector

[0099] Measurement range: Diffraction angle 2θ = 10° to 70°

[0100] Scanning speed: 1° / minute

[0101] Figure 6 It is a diffraction pattern showing the results of a powder X-ray diffraction test. In Figure 6 Among them, the three diffraction patterns are, in order from the top, the measurement results of the sample before acid treatment, after 30 seconds of acid treatment, and after 5 minutes of acid treatment. The half-value width (full width at half maximum) of the peak at 2θ = 16.7° was 0.1961° before acid treatment, but it was 0.0745° (about 0.38 times) after 30 seconds of treatment with 36 mass% hydrochloric acid. In addition, the half-value width (full width at half maximum) of the peak at 2θ = 19.3° was 0.1967° before acid treatment, but it was 0.0937° (about 0.48 times) after 30 seconds of treatment with 36 mass% hydrochloric acid. An oxide film was formed on the surface of the LLZT powder, but the oxide film was removed by acid treatment. As a result, the crystallinity was improved, and the half-value width of the diffraction peak became smaller after 30 seconds of acid treatment compared to before acid treatment. However, if the acid treatment time was extended to 5 minutes, the reaction between LLZT and hydrochloric acid progressed, and the crystallinity disappeared instead. Therefore, hereinafter, as the inorganic solid electrolyte, those obtained by treating with 2 mass% hydrochloric acid for 30 seconds are used for both particles and powders.

[0102] (Example 1A)

[0103] By mixing the above IPC1 and the inorganic solid electrolyte in a mortar and pressing them with a press (300 MPa), granular composite electrolytes were produced.

[0104] (Example 2A)

[0105] Except for changing the mixing ratio of LLZT powder and the above IPC1 as shown in Table 1, composite electrolytes were produced in the same manner as in Example 1A.

[0106] (Comparative Examples 1A to 3A)

[0107] Samples for each comparative example were prepared as shown in Table 1. It should be noted that for the sample of Comparative Example 1A, granular LLZT electrolytes were produced by pressing LLZT powder with a press (300 MPa).

[0108] <Measurement of hardness>

[0109] For each sample of the examples and comparative examples, the hardness was measured using a Type A durometer based on JIS K 6253. As the sample, a granular sample with a diameter of 8 mm was used. The hardness was measured at five points for each sample of the examples and comparative examples, and the average value was taken.

[0110] Table 1

[0111] Composition * Hardness Example 1A IPC1: LLZT = 10:90 84.8 Example 2A IPC1: LLZT = 30:70 87.8 Comparative Example 1A LLZT 100% ＞95 Comparative Example 2A [C2C1pyrr][TFSA] 100% Destruction Comparative Example 3A IPC1 Destruction

[0112] * Mass ratio

[0113] In Table 1, although the sample of Comparative Example 1 had high strength, depending on the measurement position, the sample was sometimes damaged during the measurement and the hardness could not be measured. Regarding Comparative Examples 2A and 3A, the sample was damaged at any point during the measurement and the hardness could not be measured. It is speculated that by incorporating a plastic ionic crystal into the inorganic solid electrolyte, the particles of the inorganic solid electrolyte are bonded more strongly to each other, making the sample less prone to cracking.

[0114] (Examples 1B to 2B)

[0115] IPC2 was used instead of IPC1, and the composition was set as in Table 2. Except for this, the composite electrolyte was prepared in the same manner as in Example 1.

[0116] (Examples 3B to 4B)

[0117] IPC3 was used instead of IPC1, and the composition was set as in Table 2. Except for this, the composite electrolyte was prepared in the same manner as in Example 1.

[0118] (Comparative Example 4B)

[0119] 1-Ethyl-3-methylimidazolium bis(fluorosulfonyl)amide ([C2C1im][FSA]), which is an ionic liquid, was used instead of IPC1, and the composition was set as in Table 2. Except for this, the composite electrolyte was prepared in the same manner as in Example 1.

[0120] For the composite electrolytes of Examples 1B to 4B and Comparative Example 4B, the hardness was measured using a Type A durometer as described above. The results are shown in Table 2.

[0121] Table 2

[0122] Composition * Hardness Example 1B IPC2: LLZT = 10:90 80.4 Example 2B IPC2: LLZT = 30:70 79.8 Example 3B IPC3: LLZT = 10:90 85.4 Example 4B IPC3: LLZT = 30:70 89.2 Comparative Example 4B IL: LLZT = 20:80 Destruction

[0123] * Mass ratio

[0124] <Measurement of impedance>

[0125] The specimens of Comparative Example 1A and the composite electrolytes of Example 1A and Example 2A were each sandwiched between two Li plates to fabricate measurement cells (A). In addition, the specimens of Comparative Example 1A, the composite electrolytes of Example 1A and Example 2A were each sandwiched between two SUS (SUS316L) plates to fabricate measurement cells (B).

[0126] The two Li plates of each measurement cell (A) were electrically connected to the terminals of an impedance analyzer (Sl1260 manufactured by Solatron Analytical) respectively, and the measurement of the alternating current impedance spectrum was carried out. The measurement was carried out in the range of 25 °C and a frequency of 10 mHz to 10 MHz. Similarly, each measurement cell (B) was also measured. The obtained resistance values are shown in Table 3.

[0127] Figure 1 It is a graph showing the Nyquist curves measured in each measurement cell (A). In addition, Figure 2 It is a graph showing the Nyquist curves measured in each measurement cell (B).

[0128] Table 3

[0129] Battery for measurement (A) Battery for measurement (B) Example 1A 60000Ω <80000Ω Example 1B 5000Ω 5000Ω Comparative Example 1A Unable to measure * Unable to measure *

[0130] * The resistance was too high to measure.

[0131] As can be seen from Table 3, for the composite electrolytes of Example 1A and Example 2A, the interfacial adhesion was improved and the interfacial resistance was reduced.

[0132] <Measurement of Raman spectrum>

[0133] A Raman spectrometer (DRX3 manufactured by Thermo Fisher Scientific) was used to measure the Raman spectrum. The measurement was carried out by placing each specimen in a sealable glass bottle and irradiating the particles with a laser (wavelength 785 nm).

[0134] Figure 3 The Raman spectra of each specimen are shown in. Figure 3 The six Raman spectra in respectively correspond to the following specimens in order from the top. It should be noted that Figures 3 - 5 The vertical axis of is intensity (arbitrary unit).

[0135] (1-1) Composite electrolyte of Example 2A

[0136] (1-2) A substance obtained by mixing LLZT and [C2C1pyrr][TFSA] at 70:30 (mass ratio)

[0137] (1-3) Composite electrolyte of Example 1A

[0138] (1-4) IPC1

[0139] (1-5) [C2C1pyrr][TFSA]

[0140] (1-6) LLZT

[0141] The Figure 3 spectra of (1-1) to (1-6) were curve-fitted to separate the peaks. In addition, by comparing the peak positions of the separated peaks, the assignment can be made as follows.

[0142] (1-1)

[0143] The S-N-S bending vibration of the TFSA anion interacting with the organic cation (743.3 cm -1 ) and the S-N-S bending vibration of the TFSA anion interacting with the alkali metal ion (749.6 cm -1 )

[0144] The peak of LLZT (743.4 cm -1 )

[0145] (1-2)

[0146] The S-N-S bending vibration of the TFSA anion interacting with the organic cation (743.2 cm -1 )

[0147] The peak of LLZT (743.4 cm -1 )

[0148] (1-3)

[0149] The S-N-S bending vibration of the TFSA anion interacting with the organic cation (743.2 cm -1 )

[0150] The peak of LLZT (743.4 cm -1 )

[0151] (1-4)

[0152] The S-N-S bending vibration of the TFSA anion interacting with the organic cation (741.7 cm -1 ) and the S-N-S bending vibration of the TFSA anion interacting with the alkali metal ion (749.3 cm -1 )

[0153] (1-5)

[0154] The S-N-S bending vibration of the TFSA anion interacting with the organic cation (741.5 cm -1 )

[0155] (1 - 6)

[0156] The peak of LLZT (743.4 cm -1 )

[0157] In Figure 3 the spectrum of (1 - 5), the peak corresponding to the S - N - S bending vibration of the TFSA anion interacting with the organic cation is seen at 741.5 cm -1 . In addition, in Figure 3 the spectrum of (1 - 4), the peak corresponding to the S - N - S bending vibration of the TFSA anion interacting with the organic cation is seen at approximately the same position as (1 - 5), i.e., 741.7 cm -1 , and the peak corresponding to the S - N - S bending vibration of the TFSA anion interacting with the lithium ion is seen at 749.3 cm -1 . On the other hand, in the spectra of (1 - 1), (1 - 2), and (1 - 3) containing LLZT, the peak corresponding to the S - N - S bending vibration of the TFSA anion interacting with the organic cation is shifted to around 743.2 cm -1 . This implies that an interaction between the TFSA anion and LLZT is also generated. It should be noted that the Raman spectrum of LLZT is a very broad peak as shown in (1 - 6), so it can be clearly distinguished from the peak corresponding to the S - N - S bending vibration of the TFSA anion.

[0158] In the spectrum (1 - 4), the ratio of the area of the peak (Li+) attributed to the S - N - S bending vibration (749.3 cm -1 ) of the TFSA anion interacting with the alkali metal ion and the area of the peak (Org+) attributed to the S - N - S bending vibration (741.7 cm -1 ) of the TFSA anion interacting with the organic cation is (20 / 80) = 0.25. On the other hand, in the spectrum (1 - 4), the ratio of the area of the peak (Li+) attributed to the S - N - S bending vibration (749.6 cm -1 ) of the TFSA anion interacting with the alkali metal ion and the area of the peak (Org+) attributed to the S - N - S bending vibration (743.3 cm -1 ) of the TFSA anion interacting with the organic cation is (13 / 87) = 0.15. By adding LLZT to the IPC in this way, the area of the peak attributed to LiTFSI relatively decreases. In the spectrum (1 - 2), the S - N - S bending vibration (749.3 cm -1) The peak of + basically disappeared. From this, it was learned that the interaction between Li+ and TFSI anions weakened. As a result, it was learned that Li

[0159] Figure 4 The Raman spectra of each sample are shown in Figure 4 The five Raman spectra in

[0160] respectively correspond to the following samples in order from the top.

[0161] (2-1) Composite electrolyte of Example 1B

[0162] (2-2) Composite electrolyte of Example 2B

[0163] (2-3) Substance obtained by mixing [C2C1pyrr][FSA] and LLZT at 30:70 (mass ratio)

[0164] (2-4) IPC2

[0165] By Figure 4 the results shown in

[0166] In addition, Figure 5 the Raman spectra of each sample are shown in Figure 5 The four Raman spectra in

[0167] respectively correspond to the following samples in order from the top.

[0168] (3-1) Composite electrolyte of Example 3B

[0169] (3-2) Composite electrolyte of Example 4B

[0170] (3-3) IPC3

[0171] By Figure 5 the results shown in

[0172] <Oxidation resistance test (linear sweep voltammetry (LSV))>

[0173] Linear sweep voltammetry measurements were performed on three cells (two-electrode cells) with the following configurations.

[0174] Battery 1: (Lithium / Electrolyte 11 / Aluminum mesh)

[0175] Battery 2: (Lithium / Electrolyte 21 / Electrolyte 22 / Aluminum mesh)

[0176] Battery 3: (Lithium / Electrolyte 31 / Electrolyte 32 / Aluminum mesh)

[0177] It should be noted that the composition of each electrolyte is as follows.

[0178] Electrolyte 11: Soak the substance obtained by mixing LLZT and acetylene black (AB) in a mass ratio of 10:2 with 1 M LiPF 6 solution (the solvent is a mixed solvent of ethylene carbonate (EC): dimethyl carbonate (DMC) = 1:1 (volume ratio)) to obtain the electrolyte

[0179] Electrolyte 21: The composite electrolyte of Example 2B

[0180] Electrolyte 22: The substance obtained by mixing the above IPC2 and acetylene black in a mass ratio of 7:3. Electrolyte 31: The composite electrolyte of Example 2B

[0181] Electrolyte 32: The substance obtained by mixing the composite electrolyte of Example 2B and acetylene black in a mass ratio of 10:2

[0182] The LSV was measured using a VPS manufactured by Bio-Logic. The conditions for the LSV measurement were: scan rate: 0.1 mV / s, the area of the electrolyte particles was 0.79 cm 2 , and the electrode area was 0.50 cm 2 (The area is the area perpendicular to the direction of voltage application.). It should be noted that the potential of the working electrode is expressed with Li / Li + as the reference.

[0183] Figures 7 - 9 These are the LSV measurement results obtained by measuring Batteries 1 to 3 respectively. As Figure 7 shown, for Battery 1 without using IPC, an oxidation peak was observed near 4V. On the other hand, as Figure 8 shown, for Battery 2 using the IPC2 electrolyte, no oxidation current was observed up to around 5.2V. In addition, as Figure 9 shown, for Battery 3 using the composite electrolyte of Example 2B and acetylene black, no oxidation current was observed. From this, it is considered that the oxidative decomposition of LLZT was suppressed by using IPC and LLZT together.

[0184] (Cyclic test)

[0185] In a glove box under a dry argon atmosphere, an evaluation cell of a coin-type battery CR2032 was assembled. Specifically, in the evaluation cell, each layer was stacked in the following order to fabricate a test laminate. As the electrolyte, the composite electrolyte of Example 2B and Comparative Example 1A (LLZT only) were used. It should be noted that for the area perpendicular to the voltage application direction in the battery, the Li electrode was 0.50 cm 2 , and the electrolyte was 0.79 cm 2 .

[0186] (lithium / electrolyte / lithium)

[0187] For the above evaluation cell (lithium-lithium symmetric cell), using an electrochemical measurement system (manufactured by Bio-Logic, VSP), an arbitrary current density of X mA / cm was alternately passed for 1 hour each 2 and -X mA / cm 2 (The value of X will be described below.).

[0188] Figure 10 is a graph showing the results of a cycling test of a lithium-lithium symmetric cell using the composite electrolyte of Example 2B as the electrolyte. As shown in Figure 10 , lithium deposition and dissolution were repeated 10 cycles at a current density of 20 μA / cm 2 , 10 cycles at 50 μA / cm 2 , 10 cycles at 100 μA / cm 2 , and then again 20 cycles at 20 μA / cm 2 , and it was confirmed that stable cycling was possible.

[0189] Figure 11 Regarding the lithium-lithium battery using Comparative Example 1A (LLZT only) as the electrolyte, the current density was 100 μA / cm 2 . In the case of Comparative Example 1A, charge and discharge could not be performed.

Claims

1. A composite electrolyte comprising an inorganic solid electrolyte and a plastic ionic crystal containing alkali metal ions.

2. The composite electrolyte according to claim 1, wherein, The anions contained in the plastic ionic crystal include anions having a -SO 2 - group.

3. The composite electrolyte according to claim 1, wherein, At least one of the anions contained in the plastic ionic crystal has a -SO 2 NSO 2 - group or a -SO 3 - group.

4. The composite electrolyte according to claim 1, wherein, The plastic ionic crystal has (FSO 2 ) 2 N - and (CF 3 SO 2 ) 2 N - at least one of them.

5. The composite electrolyte according to claim 1 or 2, wherein, further comprising an organic cation, At least one of the anions contained in the plastic ionic crystal has a -SO 2 NSO 2 - group, for the Raman spectrum measured at 25 °C, satisfying at least one of the following conditions (1) and (2): (1) The Raman shift of the peak corresponding to the S-N-S bending vibration of the anion interacting with the organic cation measured for the composite electrolyte is at a higher wavenumber than the Raman shift of the peak corresponding to the S-N-S bending vibration of the anion measured for the salt of the organic cation and the anion, i.e., the plastic ionic crystal, contained in the composite electrolyte; (2) The Raman shift of the peak corresponding to the S-N-S bending vibration of the anion interacting with the alkali metal ion measured for the composite electrolyte is at a higher wavenumber than the Raman shift of the peak corresponding to the S-N-S bending vibration of the anion measured for the salt of the alkali metal ion and the anion contained in the composite electrolyte.

6. The composite electrolyte according to claim 1 or 2, wherein, further comprising an organic cation, At least one of the anions contained in the plastic ionic crystal has a -SO 2 NSO 2 - group, for the Raman spectrum measured at 25 °C, the ratio (Li+ / Org+) of the areas of the peaks corresponding to the S-N-S bending vibration of the anions interacting with the alkali metal ion and the anions interacting with the organic cation in the anions measured for the composite electrolyte is less than the ratio (Li+ / Org+) of the areas measured for the salt of the organic cation and the anion, i.e., the plastic ionic crystal, contained in the composite electrolyte.

7. The composite electrolyte according to claim 1 or 2, wherein, the inorganic solid electrolyte comprises at least 1 selected from the group consisting of oxide-based inorganic solid electrolytes, hydride-based solid electrolytes, and halide-based solid electrolytes.

8. The composite electrolyte according to claim 1 or 2, wherein, the inorganic solid electrolyte comprises an oxide-based inorganic solid electrolyte.

9. The composite electrolyte according to claim 8, wherein, in the X-ray diffraction pattern obtained by measuring the composite electrolyte with CuKα radiation at 25 °C, within the range of 2θ of 20° or less, at least one diffraction peak derived from the oxide-based inorganic solid electrolyte with a half-value width of 0.18° or less is observed.

10. The composite electrolyte according to claim 8, wherein, the oxide-based inorganic solid electrolyte comprises an acid-treated oxide-based inorganic solid electrolyte, Before and after the acid treatment, in the X-ray diffraction pattern obtained by measurement using CuKα radiation at 25°C, the half-value width of at least one of the diffraction peaks in the range of 2θ of 20° or less observed for the acid-treated oxide-based inorganic solid electrolyte is 0.8 times or less of the half-value width of the diffraction peak originating from the same crystal plane as that diffraction peak observed for the oxide-based inorganic solid electrolyte before the acid treatment.

11. The composite electrolyte according to claim 8, wherein as the oxide-based inorganic solid electrolyte, an oxide-based inorganic solid electrolyte is incorporated: in the X-ray diffraction pattern obtained by measuring the oxide-based inorganic solid electrolyte using CuKα radiation at 25°C, in the range of 2θ of 20° or less, at least one diffraction peak having a half-value width of 0.18° or less is observed.

12. A battery electrolyte comprising the composite electrolyte according to claim 1 or 2.

13. A battery comprising the battery electrolyte according to claim 12.

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