Weakly polar organic solvent for halogen-containing solid-state electrolyte, preparation method therefor and use thereof

Abstract

A weakly polar organic solvent for a solid-state electrolyte containing M and X, a preparation method therefor and a use thereof. The weakly polar organic solvent comprises an alkali metal halide MX, wherein M is Li+ or Na+, and X is a halide ion. A certain amount of MX is added into the weakly polar organic solvent, and the common ion effect of MX is used, so that the dissolution of M and X on the surface of the solid-state electrolyte containing M and X can be suppressed, preventing the surface composition of the solid-state electrolyte from changing, avoiding the reduction of the ionic conductivity, and improving the solvent stability of the solid-sate electrolyte containing M and X.

Description

A weakly polar organic solvent for halogen-containing solid electrolytes, and its preparation method and application Technical Field

[0001] The present application belongs to the technical field of polymer materials, and specifically relates to a weakly polar organic solvent for halogen-containing solid electrolytes, and a preparation method and application thereof. Background Art

[0002] In recent years, solid electrolytes containing halogens such as chlorine, bromine, and iodine, with ionic conductivities greater than 0.1 mS / cm, have been reported. These include argyrodite, antiperovskite, and amorphous halides and oxyhalides. However, a common problem with these solid electrolytes is the difficulty in finding suitable solvents for wet slurrying and coating, forcing them to be prepared using a purely dry process. However, these processes suffer from poor dispersion and excessively thick films, severely hindering the application of these low-cost, high-ionic-conductivity solid electrolytes. These halogen-containing solid electrolytes rapidly decompose in protic organic solvents, producing hydrogen halides. They also decompose in highly polar aprotic solvents, forcing them to be prepared using weakly polar organic solvents such as alkanes, aromatics, halogenated alkanes, halogenated aromatics, ethers, and carboxylates. However, even these weakly polar organic solvents significantly reduce the ionic conductivity of these halogen-containing solid electrolytes upon contact, making them unable to meet the process requirements for slurrying and coating. This, in turn, limits the preparation of solid-state battery electrodes, solid-state electrolyte membranes, and solid-state battery assembly.

[0003] The solvent stability of the solid electrolyte containing M and X is poor. One reason for this is that the halogen ions on the surface of the solid electrolyte containing M and X dissolve into the solvent, causing the surface composition of the solid electrolyte containing M and X to change, resulting in a decrease in ionic conductivity.

[0004] At present, the main strategies to improve the stability of the above-mentioned solid electrolyte solvents are solid electrolyte surface coating and solid electrolyte bulk doping. For example, patent CN116666740A discloses a method for coating halide electrolytes with catecholamine self-polymers, which improves the problem of poor environmental stability of halide solid electrolytes. Patent CN116505059A discloses the use of hydrophobic materials polysiloxane and / or alkyl phosphoric acid with carbon atoms greater than or equal to 14 to coat sulfide solid electrolytes to prepare solid electrolytes that have both high ionic conductivity and excellent air stability. Patent CN116613372A discloses that by heat-treating an iodine-rich antimony-based argyrodextrin phase and a tin-based lithium sulfide superion conductor phase, antimony and tin elements diffuse into each other between the two phases, thereby preparing two mutually doped sulfide solid electrolytes, thereby improving the air stability of the sulfide solid electrolyte. Patent CN116960441A discloses a Zr-doped Li 3-4x Zr xOCl solid electrolytes improve the stability of the antiperovskite crystal structure in air. However, using coating methods to improve the air and solvent stability of solid electrolytes containing halogens such as chlorine, bromine, and iodine will inevitably significantly reduce the electrolyte's ionic conductivity. Doping and modifying electrolytes mainly improves the stability of the electrolyte itself, with limited improvement in the surface and interface stability of the electrolyte, making it difficult to significantly improve the electrolyte's solvent stability.

[0005] Therefore, how to significantly improve the solvent stability of the electrolyte while ensuring the ionic conductivity of the electrolyte is a technical problem that needs to be solved urgently. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention aims to provide a weak polar organic solvent for solid electrolyte containing M and X and its preparation method and application. In the present invention, a certain amount of alkali metal halide MX is added to the weak polar organic solvent, wherein M is Li + Or Na + , X is a halogen ion, and its application in a solid electrolyte containing M and X can inhibit the dissolution of M and X on the surface of the solid electrolyte by utilizing the common ion effect of MX, thereby preventing the surface composition of the solid electrolyte from changing, avoiding the reduction of ionic conductivity, and improving the solvent stability of the solid electrolyte containing M and X.

[0007] To achieve this goal, this application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a weakly polar organic solvent for a solid electrolyte containing M and X, wherein the weakly polar organic solvent comprises an alkali metal halide MX, wherein M is Li + Or Na + , X is a halogen ion, specifically, X is F - 、Cl - Br - or I - At least one of .

[0009] In the present application, a certain amount of MX is added to a weakly polar organic solvent, and the weakly polar organic solvent is applied to a solid electrolyte containing M and X. By utilizing the common ion effect of MX, the dissolution of M and X on the surface of the solid electrolyte can be inhibited, the surface composition of the solid electrolyte can be prevented from changing, the reduction of ionic conductivity can be avoided, and the solvent stability of the solid electrolyte containing M and X can be improved.

[0010] In this application, by utilizing the common ion effect of MX in weakly polar organic solvents, the solvent stability of the solid electrolyte containing M and X can be improved, thereby adapting to the wet preparation process of the pole piece and the solid electrolyte membrane, thereby meeting the requirements of the pole piece preparation and battery assembly process of the solid-state battery.

[0011] As a preferred technical solution of the present application, in the weakly polar organic solvent, the concentration of MX is 10% to the saturated concentration of MX in the weakly polar organic solvent. For example, the concentration of MX can be 10%, 20%, 30%, 50%, 80%, 90% or 99% of the saturated concentration of MX in the weakly polar organic solvent, preferably 30% to its saturated concentration, and more preferably 50% to its saturated concentration.

[0012] In the present application, the weakly polar organic solvent contains a saturated concentration of MX, which can maximize the solvent stability of the solid electrolyte containing M and X.

[0013] As a preferred technical solution of the present application, the weakly polar organic solvent includes any one or a combination of at least two of alkanes, aromatic hydrocarbons, halogenated hydrocarbons, ethers or carboxylates.

[0014] Preferably, the number of carbon atoms in the alkane is 6-16, for example, 6, 8, 10, 12, 14 or 16.

[0015] Preferably, the alkane includes any one or a combination of at least two of hexane, heptane, octane, nonane, decane, dodecane, tetradecane, hexadecane, cyclohexane or methylcyclohexane.

[0016] Preferably, the alkane is a normal alkane or an isoalkane.

[0017] Preferably, the aromatic hydrocarbons include any one or a combination of at least two of toluene, p-xylene, o-xylene, m-xylene, ethylbenzene, n-propylbenzene, isopropylbenzene, n-butylbenzene, isobutylbenzene, tert-butylbenzene or cyclohexylbenzene.

[0018] Preferably, the halogenated hydrocarbon includes a halogenated alkane and / or a halogenated aromatic hydrocarbon.

[0019] Preferably, the number of carbon atoms in the halogenated alkane is 1-8, for example, 1, 2, 3, 4, 5, 6 or 8.

[0020] Preferably, the halogenated alkane includes any one or a combination of at least two of dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, dibromomethane or 1,2-dibromoethane.

[0021] Preferably, the halogenated aromatic hydrocarbon is any one of chlorobenzene, p-dichlorobenzene, m-dichlorobenzene, o-dichlorobenzene, p-chlorotoluene, m-chlorotoluene, o-chlorotoluene, chloromethylbenzene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, p-fluorotoluene, m-fluorotoluene, o-fluorotoluene or bromobenzene, or a combination of at least two thereof.

[0022] Preferably, the number of carbon atoms in the ether is 4-10, for example, 4, 6, 8 or 10.

[0023] Preferably, the ether includes any one of n-propyl ether, n-butyl ether, methyl tert-butyl ether, tetrahydrofuran, tetrahydropyran, anisole, phenethyl ether, phenylpropyl ether, phenylbutyl ether, 1,4-dioxane, cyclohexyl butyl ether, hexylphenyl ether, pentafluoropropyl ether or heptafluorobutyl ether, or a combination of at least two thereof.

[0024] Preferably, the number of carbon atoms in the carboxylic acid ester is 6-10, for example, 6, 8 or 10.

[0025] Preferably, the carboxylate comprises any one or a combination of at least two of butyl acetate, propyl propionate, butyl propionate, ethyl butyrate, propyl butyrate, butyl butyrate, phenyl acetate, benzyl acetate, ethyl cyclohexanecarboxylate, methyl benzoate, ethyl benzoate or propyl benzoate.

[0026] As a preferred technical solution of the present application, the polarity value of n-pentane is 0, and the polarity value of the weakly polar organic solvent relative to n-pentane is 0-4.5, preferably 0-3.

[0027] It should be noted that the specific polarity of a solvent can be found in Rohrschneider's polarity parameter, p1, which is specifically defined as a measure of the ability of a solvent to interact with various test solutes. p1 increases with increasing solvent polarity.

[0028] As a preferred technical solution of the present application, the solid electrolyte containing M and X includes any one or a combination of at least two of a halogen-containing argyrodite solid electrolyte, a halogen-containing antiperovskite solid electrolyte, a halide solid electrolyte or a halide oxide solid electrolyte.

[0029] Preferably, the halogen-containing argyrodite solid electrolyte comprises Li6PS5X, where X comprises any one of Cl, Br or I or a combination of at least two thereof.

[0030] Preferably, the halogen-containing Argentum solid electrolyte further comprises Li7P2S8I, Li 5.3 PS 4.3 ClBr 0.7 、Li 6-n PS 5-n Cl 1+n (n=0.25, 0.375, 0.5, 0.55, 0.6), Li6PS 5-n O n Cl(0<n≤1.5), Li 5.3 PS4.3 Br 1.7 、Li6PS 5-n O n Br(0<n≤1.5), Li 5.35 Ca 0.1 PS 4.5 Cl 1.55 、Li 9.88 GeP 1.96 Sb 0.04 S 11.88 Cl 0.12 、Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 、Li 6.6 Ge 0.6 P 0.4 S5Cl、Li 6.6 Ge 0.6 P 0.4 S5I、Li 6.6 Sb 0.4 Si 0.6 S5I、Li 6.5 Sb 0.5 Ge 0.5 S5I or (Li 5.69 Na 0.06 )PS 4.75 Cl 1.25 Any one of .

[0031] Preferably, the molecular formula of the halogen-containing antiperovskite solid electrolyte includes M3OX, M includes Li or Na, and X includes any one or a combination of at least two of F, Cl or Br. For example, it can be Li3OCl, Li3OBr, Na3OCl or Na3OBr.

[0032] It should be noted that the halogen-containing antiperovskite solid electrolyte can also be other types of antiperovskite electrolytes, such as Li2(OH)Cl, Li2(OH)Br, Li 2.990 Ba 0.006 OCl, Li2(OH) 0.9 F 0.1 Cl, Li 1.16 (OH 1.84 )Cl、LiOCl 0.5 Br 0.5 、Li7O2Br3、Li3SCl 0.5 (BF4) 0.5 、Li6OCl4、Li 6.5 OS 1.5 I 1.5、Li 25 O4S5I7、Na4OI2、Na 25 O4S5I7、Na 2.9 Sr 0.05 OBr 0.6 I 0.4 、Na 2.99 Ba 0.005 OCl 1-x (OH) x 、Na3SI 0.5 (BCl4) 0.5 、Na(SeO4)F 0.5 Cl 0.5 or Na3LiO5S 0.5 I2, etc.

[0033] Preferably, the molecular formula of the halide solid electrolyte includes Li3M'X6 or Li2M"X4, M' includes any one of Er, Yb, Al, Ga, In, Sc, Y or La-Lu or a combination of at least two, wherein La-Lu includes any element between the two, M" includes any one of Mg, Al, Fe, Co, Ni, Mn, Cr, Ti, V, Zr, Cd, Zn or In or a combination of at least two, and X includes any one of Cl, Br or I or a combination of at least two. Exemplary, for example, it can be Li3InCl6, Li3YCl6, Li3ErCl6, Li3YbCl6, Li3InBr6, Li3ErI6, Li3AlCl6, Li3GaCl6, Li3ScCl6, Li3LaCl6, Li3LuCl6, Li2MgCl4, LiAlCl4, LiFeCl4, LiCoCl4, LiNiCl4, Li2MnCl4, LiCrCl4, LiTiCl4, LiVCl4, Li2ZrCl6, LiCdCl4, Li2ZnBr4, LiInBr4 or LiInI4, etc.

[0034] It should be noted that the halide solid electrolyte can also be a halide electrolyte of other compositions, for example, it can be Li3InBr3I3, Li3InBr 6-y X y (X=F or I; 0<y≤2), Li6M″'X8(M″'=V, Fe, Co, Ni, Mn or Mg, X=Cl or Br), Li2In x Sc 0.666-x Cl4(0≤x≤0.666) or Na2ZrCl6, etc.

[0035] Preferably, the molecular formula of the oxyhalide solid electrolyte includes M a M 1b X c O d , M includes Li or Na, M 1 Including any one or a combination of at least two of Al, Ti, Zr, V, Nb or Ta, X includes any one or a combination of at least two of F, Cl, Br or I, 0.4≤a≤3, 0 <b<2,0≤c≤6,0≤d≤1。

[0036] It should be noted that when M 1 =Al, Ti or Zr, a, b, c and d satisfy a+3b=c+2d; when M 1 =V, Nb or Ta, a, b, c and d satisfy a+4b=c+2d.

[0037] It should be noted that the oxyhalide solid electrolyte may also be Li 2x TaO x Cl5 (1.1≤x≤1.8) or Li3HfOCl4, or other oxyhalide electrolytes, such as 0.13ZrO2-0.61NaCl-0.26Na2ZrCl6, Li 1.75 ZrCl 4.75 O 0.5 、LiTaOCl4、LiNbOCl4、Li 2.5 ZrCl 5.5 O 0.5 、ZrO2-2Li2ZrCl5F、ZrO2-2Li2ZrCl6 or NaAlCl 2.5 O 0.75 wait.

[0038] Preferably, the ionic conductivity of the solid electrolyte containing M and X is ≥0.1 mS / cm.

[0039] In a second aspect, the present application provides a method for preparing a weakly polar organic solvent for a solid electrolyte containing M and X as described in the first aspect, the preparation method comprising:

[0040] The alkali metal halide MX and the weak polar organic solvent are mixed in proportion to obtain the weak polar organic solvent for the solid electrolyte containing M and X.

[0041] As a preferred technical solution of the present application, when the MX is at a saturated concentration in the weakly polar organic solvent, the preparation method of the weakly polar organic solvent comprises the following steps:

[0042] Adding excess MX to a weakly polar organic solvent to saturate the weakly polar organic solvent with MX, and then removing excess MX to obtain a weakly polar organic solvent with a saturated concentration of MX;

[0043] Preferably, when the weakly polar organic solvent MX used for the solid electrolyte containing M and X is at a non-saturated concentration, the preparation method of the weakly polar organic solvent comprises the following steps:

[0044] To a weakly polar organic solvent saturated with MX, add a certain volume of the same weakly polar organic solvent without MX to dilute it, and after mixing, obtain a weakly polar organic solvent with a non-saturated concentration of MX. For example, to a volume of 1L of an organic solvent saturated with MX, add 1L of a blank organic solvent without MX to dilute it, and after mixing, obtain a 50% MX organic solvent.

[0045] In a third aspect, the present application provides an application of a weakly polar organic solvent for a solid electrolyte containing M and X as described in the first aspect, wherein the weakly polar organic solvent is used to prepare a solid electrolyte membrane containing M and X and / or an electrode sheet using a solid electrolyte containing M and X, wherein M is Li + Or Na + , X is a halogen ion, specifically, X is F - 、Cl - Br - or I - At least one of .

[0046] As a preferred technical solution of the present application, the method for preparing the solid electrolyte membrane containing M and X includes:

[0047] Mixing a solid electrolyte containing M and X, a binder, and a weakly polar organic solvent to obtain a slurry, coating and drying the slurry, and then pressing it into a film to obtain the solid electrolyte membrane containing M and X;

[0048] Preferably, the method for preparing an electrode sheet using a solid electrolyte containing M and X comprises:

[0049] The electrode active material, a solid electrolyte containing M and X, a conductive agent, a binder and a weakly polar organic solvent are mixed to obtain a slurry, the slurry is coated on a current collector, and after drying, the electrode sheet using the solid electrolyte containing M and X is obtained.

[0050] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0051] Compared with the prior art, this application has the following beneficial effects:

[0052] The present application adds a certain amount of alkali metal halide MX to a weakly polar organic solvent. By utilizing the common ion effect of MX, the dissolution of M and X on the surface of the solid electrolyte can be inhibited, the surface composition of the solid electrolyte can be prevented from changing, the ionic conductivity can be avoided, and the solvent stability of the solid electrolyte containing M and X can be improved.

[0053] In this application, by means of the common ion effect of alkali metal halide MX in weakly polar organic solvents, the solvent stability of the solid electrolyte containing M and X can be improved, thereby adapting to the wet preparation process of the electrode and solid electrolyte membrane, thereby meeting the requirements of the electrode preparation and battery assembly process of the solid-state battery. DETAILED DESCRIPTION

[0054] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0055] Example 1

[0056] This embodiment provides a weakly polar organic solvent for a solid electrolyte containing M and X. The weakly polar organic solvent is dodecane, and the dodecane contains a saturated concentration of LiCl.

[0057] This embodiment provides a method for preparing the above-mentioned weakly polar organic solvent, which comprises the following steps:

[0058] An excess of LiCl is added to dodecane, and the LiCl is fully dissolved in the dodecane by ball milling at 80° C. to reach saturation in the dodecane. The excess undissolved LiCl is then removed by filtration to obtain the weakly polar organic solvent for the solid electrolyte containing M and X, which is recorded as solvent A.

[0059] This embodiment also provides a method for preparing a solid electrolyte membrane using the weakly polar organic solvent for the solid electrolyte containing M and X. The method comprises the following steps:

[0060] (1) Li containing Cl 1.75 ZrCl 4.75 O 0.5 The oxychloride electrolyte and solvent A are wet ball-milled to obtain a mixed slurry, and then the mixed slurry is vacuum-dried to obtain a solid electrolyte powder;

[0061] (2) Take 50 mg of solid electrolyte powder and press it into a solid electrolyte membrane in the model battery.

[0062] In this example, a model cell was assembled using stainless steel as a blocking electrode. The ionic conductivity of the oxychloride electrolyte treated with solvent A was measured by electrochemical impedance spectroscopy using an electrochemical workstation, and was found to be σ1. The ionic conductivity of the raw oxychloride electrolyte was measured by a similar method, and the ionic conductivity retention ratio σ1 / σ0 of the oxychloride electrolyte treated with solvent A was calculated to be 87%.

[0063] Example 2

[0064] This embodiment provides a weakly polar organic solvent for a solid electrolyte containing M and X. The weakly polar organic solvent is p-xylene, and the p-xylene contains a saturated concentration of LiBr.

[0065] This embodiment provides a method for preparing the above-mentioned weakly polar organic solvent, which comprises the following steps:

[0066] An excess of LiBr is added to p-xylene, and the LiBr is fully dissolved in the p-xylene by ball milling at 40° C. to reach saturation in the p-xylene. The excess undissolved LiBr is then filtered to remove the weakly polar organic solvent for the solid electrolyte containing M and X, which is recorded as solvent B.

[0067] This embodiment also provides a method for preparing a solid electrolyte membrane using the weakly polar organic solvent for the solid electrolyte containing M and X. The method comprises the following steps:

[0068] (1) wet-milling a Br-containing Li3OBr antiperovskite solid electrolyte and a solvent B to obtain a mixed slurry, and then vacuum-drying the mixed slurry to obtain a solid electrolyte powder;

[0069] (2) Take 50 mg of solid electrolyte powder and press it into a solid electrolyte membrane in the model battery.

[0070] In this example, a model cell was assembled using stainless steel as a blocking electrode. The ionic conductivity of the oxychloride electrolyte treated with solvent B was measured by electrochemical impedance spectroscopy using an electrochemical workstation, and was found to be σ1. The ionic conductivity of the raw oxychloride electrolyte was measured by a similar method, and the ionic conductivity retention ratio σ1 / σ0 of the oxychloride electrolyte treated with solvent B was calculated to be 81%.

[0071] Example 3

[0072] This embodiment provides a weak polar organic solvent for a solid electrolyte containing M and X. The weak polar organic solvent is n-octane, and the n-octane contains LiCl at a saturated concentration.

[0073] This embodiment provides a method for preparing the above-mentioned weakly polar organic solvent, which comprises the following steps:

[0074] An excess of LiCl is added to n-octane, and the LiCl is fully dissolved in the n-octane by ball milling at 25° C. to reach saturation in the n-octane. The excess undissolved LiCl is then filtered to remove the weakly polar organic solvent for the solid electrolyte containing M and X, which is recorded as solvent C.

[0075] This embodiment also provides a method for preparing a solid electrolyte membrane using the weakly polar organic solvent for the solid electrolyte containing M and X. The method comprises the following steps:

[0076] The Cl-containing argyrodite Li6PS5Cl solid electrolyte and solvent C were wet-ball milled and mixed. The resulting adhesive solution, prepared by adding binder styrene-butadiene rubber (SBR) and solvent C, was further ball-milled. The mixture was then coated on a PET release film and rolled to produce a 40μm-thick Li6PS5Cl solid electrolyte membrane.

[0077] In this example, the ionic conductivity of the Li6PS5Cl solid electrolyte membrane was measured as σ1 using an electrochemical impedance spectroscopy method using an electrochemical workstation, and the ionic conductivity of the argyrodite Li6PS5Cl solid electrolyte raw material was measured as σ0. The ionic conductivity retention rate σ1 / σ0 of the Li6PS5Cl solid electrolyte membrane was calculated to be 38%.

[0078] Example 4

[0079] This embodiment provides a weakly polar organic solvent for a solid electrolyte containing M and X. The weakly polar organic solvent is 1,2-dichloroethane, and the 1,2-dichloroethane contains a saturated concentration of LiCl.

[0080] This embodiment provides a method for preparing the above-mentioned weakly polar organic solvent, which comprises the following steps:

[0081] An excess of LiCl is added to 1,2-dichloroethane, and the LiCl is fully dissolved in the 1,2-dichloroethane by ball milling at 25° C. to reach saturation in the 1,2-dichloroethane. The excess undissolved LiCl is then filtered to obtain the weakly polar organic solvent for the solid electrolyte containing M and X, which is recorded as solvent D.

[0082] This embodiment also provides a method for preparing a positive electrode sheet using the weakly polar organic solvent for the solid electrolyte containing M and X, the method comprising the following steps:

[0083] The positive electrode active material NCM811, Li6PS5Cl solid electrolyte, conductive agent SP (conductive carbon black) and binder HNBR (hydrogenated nitrile rubber) were mixed in a mass ratio of 65:30:3:2, solvent D was added, and the mixture was stirred evenly to form a slurry; the slurry was coated on a carbon-coated aluminum foil, dried, and finally vacuum-dried to obtain a positive electrode sheet containing the Li6PS5Cl argyrodite solid electrolyte.

[0084] In this example, a Li6PS5Cl solid electrolyte was used to prepare an electrolyte separator by powder tableting. An In sheet was used as the negative electrode, and this was assembled with the aforementioned positive electrode sheet to produce a model battery. The model battery was cycled according to the following charge and discharge regime: constant current and constant voltage charging at 0.1C to 4.2V, a cutoff current of 0.05C, and then constant current discharge at 0.1C to 2.0V. The model battery had an initial discharge capacity of 186mAh / g, and the ohmic impedance of the model battery at 50% SOC was measured by electrochemical impedance spectroscopy to be 2.85Ω.

[0085] Example 5

[0086] This embodiment provides a weak polar organic solvent for a solid electrolyte containing M and X. The weak polar organic solvent is tetrahydrofuran, and the tetrahydrofuran contains a saturated concentration of LiI.

[0087] This embodiment provides a method for preparing the above-mentioned weakly polar organic solvent, which comprises the following steps:

[0088] An excess amount of LiI is added to tetrahydrofuran, and the LiI is fully dissolved in the tetrahydrofuran by ball milling at 30° C. to reach saturation in the tetrahydrofuran. The excess undissolved LiI is then filtered to obtain the weakly polar organic solvent for the solid electrolyte containing M and X, which is recorded as solvent E.

[0089] This embodiment also provides a method for preparing a negative electrode sheet using the weakly polar organic solvent for the solid electrolyte containing M and X, the method comprising the following steps:

[0090] The negative electrode active materials Si / C, Li7Sb 0.05 P 2.95 S 10.5 I 0.5 Solid electrolyte, conductive agent SP (conductive carbon black) and binder SBR were mixed in a mass ratio of 61:35:2:2, solvent E was added, stirred evenly, and a slurry was prepared; the slurry was coated on a carbon-coated copper foil, dried, and finally vacuum-dried to obtain a slurry containing Li7Sb 0.05 P 2.95 S 10.5 I 0.5 Silicon-carbon anode sheet of solid electrolyte.

[0091] In this example, the electrolyte separator was prepared by powder tableting using a Li6PS5Cl solid electrolyte. The positive electrode prepared in Example 4 was used as the positive electrode of this example, and was assembled with the aforementioned silicon-carbon negative electrode to produce a model battery. The model battery was cycled according to the following charge-discharge mechanism: constant current and constant voltage charging at 0.1C to 4.2V, a cutoff current of 0.05C, and then constant current discharge at 0.1C to 2.0V. The model battery had an initial discharge capacity of 179mAh / g, and the ohmic impedance of the model battery at 50% SOC was measured by electrochemical impedance spectroscopy to be 3.68Ω.

[0092] Example 6

[0093] The difference between this embodiment and embodiment 1 is that the preparation method of the weakly polar organic solvent comprises:

[0094] A certain volume of LiCl was added to dodecane, and the LiCl was fully dissolved in the dodecane by ball milling at 80° C. to obtain a weakly polar organic solvent F having a LiCl concentration of 50% of the saturation concentration.

[0095] The rest of the preparation methods and parameters remained the same as in Example 1.

[0096] The ionic conductivity retention ratio σ1 / σ0 of the oxychloride electrolyte treated with solvent F measured in this embodiment is 55%.

[0097] Example 7

[0098] The difference between this embodiment and embodiment 1 is that the preparation method of the weakly polar organic solvent comprises:

[0099] A certain volume of LiCl was added to dodecane, and the LiCl was fully dissolved in the dodecane by ball milling at 80° C. to obtain a weakly polar organic solvent G having a LiCl concentration of 30% of the saturation concentration.

[0100] The rest of the preparation methods and parameters remained the same as in Example 1.

[0101] The ionic conductivity retention ratio σ1 / σ0 of the oxychloride electrolyte treated with solvent G measured in this example is 47%.

[0102] Example 8

[0103] The difference between this embodiment and embodiment 1 is that the preparation method of the weakly polar organic solvent comprises:

[0104] A certain volume of LiCl was added to dodecane, and the LiCl was fully dissolved in the dodecane by ball milling at 80° C. to obtain a weakly polar organic solvent H having a LiCl concentration of 20% of the saturation concentration.

[0105] The remaining preparation methods and parameters were consistent with those in Example 1.

[0106] The ionic conductivity retention ratio σ1 / σ0 of the oxychloride electrolyte treated with solvent H measured in this embodiment is 42%.

[0107] Example 9

[0108] The difference between this embodiment and embodiment 1 is that the preparation method of the weakly polar organic solvent comprises:

[0109] A certain volume of LiCl was added to dodecane, and the LiCl was fully dissolved in the dodecane by ball milling at 80° C. to obtain a weakly polar organic solvent I having a LiCl concentration of 10% of the saturation concentration.

[0110] The rest of the preparation methods and parameters remained the same as in Example 1.

[0111] The ionic conductivity retention rate σ1 / σ0 of the oxychloride electrolyte treated with solvent I measured in this example is 37%.

[0112] Comparative Example 1

[0113] The difference between this comparative example and Example 1 is that dodecane is used as the solvent instead of solvent A.

[0114] The rest of the preparation methods and parameters remained the same as in Example 1.

[0115] The ionic conductivity of the oxychloride electrolyte measured in this comparative example is σ2, and the ionic conductivity retention ratio σ2 / σ0 is 35%.

[0116] Comparative Example 2

[0117] The difference between this comparative example and Example 2 is that p-xylene is used as solvent instead of solvent B.

[0118] The rest of the preparation methods and parameters remained the same as in Example 2.

[0119] The ionic conductivity of the oxychloride electrolyte measured in this comparative example was σ2, and the ionic conductivity retention ratio σ2 / σ0 was 33%.

[0120] Comparative Example 3

[0121] The difference between this comparative example and Example 3 is that n-octane is used as the solvent instead of solvent C.

[0122] The rest of the preparation methods and parameters remained the same as in Example 3.

[0123] The ionic conductivity of the Li6PS5Cl solid electrolyte membrane measured in this comparative example is σ2, and the ionic conductivity retention ratio σ2 / σ0 is 12%.

[0124] Comparative Example 4

[0125] The difference between this comparative example and Example 4 is that 1,2-dichloroethane is used as the solvent instead of solvent D.

[0126] The remaining preparation methods and parameters remained the same as those in Example 4.

[0127] The first-cycle discharge capacity of the model battery measured in this comparative example is 179 mAh / g, and the ohmic impedance of the model battery measured at 50% SOC by electrochemical impedance spectroscopy is 5.77Ω.

[0128] Comparative Example 5

[0129] The difference between this comparative example and Example 5 is that tetrahydrofuran is used as solvent instead of solvent E.

[0130] The rest of the preparation methods and parameters remained the same as in Example 5.

[0131] The first-cycle discharge capacity of the model battery measured in this comparative example is 165 mAh / g, and the ohmic impedance of the model battery measured at 50% SOC by electrochemical impedance spectroscopy is 6.98 Ω.

[0132] analyze:

[0133] It can be seen from Example 1 and Examples 6-9 that if the LiCl concentration in the weakly polar organic solvent is 50%, 30%, 20%, and 10% of the saturation concentration, the solvent stability of the solid electrolyte can be improved to a certain extent, and the closer the LiCl content in the weakly polar organic solvent is to the saturation concentration, the better the effect.

[0134] From Example 1 and Comparative Example 1, it can be seen that the Li 1.75 ZrCl 4.75 O 0.5 The ionic conductivity retention of the chloride oxide electrolyte is significantly higher than that of the LiCl electrolyte treated with dodecane as a solvent. 1.75 ZrCl 4.75 O 0.5 The electrolyte ion conductivity retention rate shows that the weak polar organic solvent containing saturated concentration of LiCl in the present application can significantly improve the halogen-containing Li 1.75 ZrCl 4.75 O 0.5 Solvent stability of oxychloride electrolytes, thereby broadening the wet processing performance of halogen-containing solid electrolytes.

[0135] It can be seen from Example 2 and Comparative Example 2 that the ionic conductivity retention rate of the Li3OBr antiperovskite solid electrolyte obtained by using p-xylene containing a saturated concentration of LiBr as a weakly polar organic solvent is significantly higher than the ionic conductivity retention rate of the Li3OBr antiperovskite solid electrolyte treated with p-xylene not containing LiBr as a solvent. This indicates that the weakly polar organic solvent containing a saturated concentration of LiBr in the present application can significantly improve the solvent stability of the halogen-containing Li3OBr antiperovskite solid electrolyte, thereby broadening the wet processing performance of halogen-containing solid electrolytes.

[0136] It can be seen from Example 3 and Comparative Example 3 that, when the same Li6PS5Cl solid electrolyte membrane preparation process is used, the ionic conductivity of the Li6PS5Cl solid electrolyte membrane prepared using n-octane solvent C containing a saturated concentration of LiCl is more than three times that of the Li6PS5Cl solid electrolyte membrane prepared using pure n-octane solvent, indicating that n-octane containing a saturated concentration of LiCl can improve the stability of the halogen-containing Li6PS5Cl solid electrolyte.

[0137] From Example 4 and Comparative Example 4, it can be seen that the positive electrode capacity of the Cl-containing solid electrolyte prepared using 1,2-dichloroethane solvent containing saturated LiCl is better than the positive electrode prepared using 1,2-dichloroethane solvent without LiCl. The impedance of the model battery assembled with the positive electrode of the Cl-containing solid electrolyte prepared using 1,2-dichloroethane solvent containing saturated LiCl is significantly lower than the impedance of the model battery assembled with the positive electrode prepared using 1,2-dichloroethane solvent without LiCl. The main reason is that the 1,2-dichloroethane solvent containing saturated LiCl improves the stability of the Cl-containing Li6PS5Cl solid electrolyte.

[0138] It can be seen from Example 5 and Comparative Example 5 that the capacity of the negative electrode containing solid electrolyte I prepared by tetrahydrofuran solvent containing saturated concentration of LiI is better than that of the silicon-carbon negative electrode prepared by tetrahydrofuran solvent not containing LiI. The impedance of the model battery assembled by the silicon-carbon negative electrode containing solid electrolyte I prepared by tetrahydrofuran solvent containing saturated concentration of LiI is significantly lower than that of the model battery assembled by the silicon-carbon negative electrode containing solid electrolyte I prepared by tetrahydrofuran solvent not containing LiI. The main reason is that the tetrahydrofuran solvent containing saturated concentration of LiI increases the Li7Sb 0.05 P 2.95 S 10.5 I 0.5 Stability of solid electrolytes.

[0139] The applicant declares that while the present application uses the above-mentioned embodiments to illustrate the process of the present application, the present application is not limited to the above-mentioned embodiments, which does not mean that the present application must rely on the above-mentioned embodiments in order to be implemented. Those skilled in the art should understand that any improvements to the present application, equivalent replacements for the raw materials of the present application's products, addition of auxiliary ingredients, and selection of specific methods, etc., fall within the scope of protection and disclosure of the present application.

Claims

1. A weakly polar organic solvent for a solid electrolyte containing M and X, characterized in that: The weakly polar organic solvent comprises an alkali metal halide MX, wherein M is Li + Or Na + , X is a halogen ion.

2. The weakly polar organic solvent according to claim 1, characterized in that The concentration of MX is 10% to the saturated concentration of MX in the weakly polar organic solvent.

3. The weakly polar organic solvent according to claim 2, characterized in that The concentration of MX is 30% to the saturated concentration of MX in the weakly polar organic solvent.

4. The weakly polar organic solvent according to claim 3, characterized in that The concentration of MX is 50% to the saturated concentration of MX in the weakly polar organic solvent.

5. The weakly polar organic solvent according to claim 1, characterized in that The weakly polar organic solvent includes any one or a combination of at least two of alkanes, aromatic hydrocarbons, halogenated hydrocarbons, ethers or carboxylates; Preferably, the number of carbon atoms in the alkane is 6-16; Preferably, the alkane includes any one or a combination of at least two of hexane, heptane, octane, nonane, decane, dodecane, tetradecane, hexadecane, cyclohexane or methylcyclohexane; Preferably, the alkane is a normal alkane or an isoalkane; Preferably, the aromatic hydrocarbons include any one or a combination of at least two of toluene, p-xylene, o-xylene, m-xylene, ethylbenzene, n-propylbenzene, isopropylbenzene, n-butylbenzene, isobutylbenzene, tert-butylbenzene or cyclohexylbenzene; Preferably, the halogenated hydrocarbon comprises a halogenated alkane and / or a halogenated aromatic hydrocarbon; Preferably, the number of carbon atoms in the halogenated alkane is 1-8; Preferably, the halogenated alkane includes any one or a combination of at least two of dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, dibromomethane or 1,2-dibromoethane; Preferably, the halogenated aromatic hydrocarbon is any one of chlorobenzene, p-dichlorobenzene, m-dichlorobenzene, o-dichlorobenzene, p-chlorotoluene, m-chlorotoluene, o-chlorotoluene, chloromethylbenzene, fluorobenzene, p-difluorobenzene, m-difluorobenzene, o-difluorobenzene, p-fluorotoluene, m-fluorotoluene, o-fluorotoluene or bromobenzene, or a combination of at least two thereof; Preferably, the number of carbon atoms in the ether is 4-10; Preferably, the ether includes any one of n-propyl ether, n-butyl ether, methyl tert-butyl ether, tetrahydrofuran, tetrahydropyran, anisole, phenethyl ether, phenylpropyl ether, phenylbutyl ether, 1,4-dioxane, cyclohexyl butyl ether, hexylphenyl ether, pentafluoropropyl ether or heptafluorobutyl ether, or a combination of at least two thereof; Preferably, the number of carbon atoms in the carboxylic acid ester is 6-10; Preferably, the carboxylic acid ester includes any one of butyl acetate, propyl propionate, butyl propionate, ethyl butyrate, propyl butyrate, butyl butyrate, phenyl acetate, benzyl acetate, ethyl cyclohexanecarboxylate, methyl benzoate, ethyl benzoate or propyl benzoate, or a combination of at least two thereof.

6. The weakly polar organic solvent according to any one of claims 1 to 5, characterized in that: Assuming that the polarity value of n-pentane is 0, the polarity value of the weakly polar organic solvent relative to n-pentane is 0-4.

5.

7. The weakly polar organic solvent according to claim 6, characterized in that The polarity value of n-pentane is 0, and the polarity value of the weakly polar organic solvent relative to n-pentane is 0-3.

8. The weakly polar organic solvent according to any one of claims 1 to 5, characterized in that: The solid electrolyte containing M and X includes any one or a combination of at least two of a halogen-containing argyrodite solid electrolyte, a halogen-containing antiperovskite solid electrolyte, a halide solid electrolyte or a halide oxide solid electrolyte; Preferably, the halogen-containing argyrodite solid electrolyte comprises Li6PS5X, where X comprises any one of Cl, Br or I or a combination of at least two thereof; Preferably, the molecular formula of the halogen-containing antiperovskite solid electrolyte includes M3OX, M includes Li or Na, and X includes any one or a combination of at least two of F, Cl or Br; Preferably, the molecular formula of the halide solid electrolyte includes Li3M'X6 or Li2M"X4, M' includes any one of Er, Yb, Al, Ga, In, Sc, Y or La-Lu or a combination of at least two, M" includes any one of Mg, Al, Fe, Co, Ni, Mn, Cr, Ti, V, Zr, Cd, Zn or In or a combination of at least two, and X includes any one of Cl, Br or I or a combination of at least two; Preferably, the molecular formula of the oxyhalide solid electrolyte includes M a M 1 b X c O d , M includes Li or Na, M 1 Including any one or a combination of at least two of Al, Ti, Zr, V, Nb or Ta, X includes any one or a combination of at least two of F, Cl, Br or I, 0.4≤a≤3, 0 <b<2,0≤c≤6,0≤d≤1。 9. The weakly polar organic solvent according to any one of claims 1 to 5, characterized in that: The ion conductivity of the solid electrolyte containing M and X is ≥0.1 mS / cm.

10. A method for preparing a weakly polar organic solvent for a solid electrolyte containing M and X as claimed in any one of claims 1 to 9, characterized in that: The preparation method comprises: The alkali metal halide MX and the weak polar organic solvent are mixed in proportion to obtain the weak polar organic solvent for the solid electrolyte containing M and X.

11. The preparation method according to claim 10, characterized in that: When the MX is at a saturated concentration in the weakly polar organic solvent, the preparation method of the weakly polar organic solvent comprises the following steps: An excess amount of MX is added to the weak polar organic solvent to make MX reach saturation in the weak polar organic solvent, and then the excess MX is removed to obtain a weak polar organic solvent with a saturated concentration of MX.

12. The preparation method according to claim 11, characterized in that: When the MX is at a non-saturated concentration in the weakly polar organic solvent, the preparation method of the weakly polar organic solvent comprises the following steps: A certain volume of the same weak polar organic solvent without MX is added to a weak polar organic solvent with a saturated concentration of MX for dilution, and after uniform mixing, a weak polar organic solvent with a non-saturated concentration of MX is obtained.

13. Use of a weakly polar organic solvent for a solid electrolyte containing M and X as claimed in any one of claims 1 to 9, characterized in that: The weakly polar organic solvent is used to prepare a solid electrolyte membrane containing M and X and / or an electrode sheet using a solid electrolyte containing M and X, wherein M is Li + Or Na + , X is a halogen ion.

14. The use according to claim 13, characterized in that The method for preparing the solid electrolyte membrane containing M and X comprises: A solid electrolyte containing M and X, a binder and a weakly polar organic solvent are mixed to obtain slurry, the slurry is coated and dried, and then pressed into a film to obtain the solid electrolyte membrane containing M and X.

15. The use according to claim 13, characterized in that: The method for preparing an electrode sheet using a solid electrolyte containing M and X comprises: The electrode active material, the solid electrolyte containing M and X, the conductive agent, the binder and the weak polar organic solvent are mixed to obtain a slurry, the slurry is coated on the current collector, and the electrode sheet using the solid electrolyte containing M and X is obtained after drying.