Sulfide solid electrolyte and its preparation method and application

Abstract

The present invention discloses a sulfide solid electrolyte and its preparation method and application. The sulfide solid electrolyte comprises: a core layer, the core layer comprises a structural formula of Li 6‑a PS 5‑a X 1+a At least one of the compounds, X is a halogen atom, a = 0 to 1; a shell layer, the shell layer is arranged on at least a portion of the surface of the core layer, and the shell layer includes a structural formula of Li 6‑a PS 5‑a X 1+a‑b Y b At least one of the compounds, Y is a pseudo-halogen atomic group, and b = 0.1 to 0.9. The sulfide solid electrolyte modified by pseudo-halogen atomic group substitution of the present invention has significantly improved resistance to organic solvent corrosion; at the same time, the dispersion ability of the electrolyte in the slurry is improved, thereby improving the stability and thixotropy of the sulfide solid electrolyte in the electrolyte slurry, and also increasing the solid content of the electrolyte slurry, thereby improving the first-cycle discharge capacity, first coulombic efficiency, and cycle life of the solid-state battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and in particular relates to a sulfide solid electrolyte and a preparation method and application thereof. Background Art

[0002] All-solid-state batteries are considered to be the next generation of high-safety batteries because they use solid electrolytes to replace the electrolytes of traditional batteries and have non-flammable properties. Among them, sulfide solid electrolytes have high ionic conductivity (up to 10 -2 S / cm) and lower grain boundary resistance, which has attracted widespread attention in the industry.

[0003] During the wet slurrying and coating process of sulfide solid electrolyte electrodes, the use of solvents for wet coating in traditional systems (such as NMP and H2O) will cause serious degradation of the sulfide electrolyte, resulting in the inability to perform the battery performance. Currently, non-polar, low-polarity solvents are mostly selected to slow down the corrosion of the solvent on the sulfide electrolyte. The use of low-polarity, non-proton solvents can slow down the damage to the sulfide electrolyte structure to a certain extent, but it cannot completely avoid the adverse reactions between the solvent and the electrolyte. In fact, even if such solvents are used to prepare sulfide electrolyte slurry, the attenuation of the ionic conductivity of the electrolyte is still obvious, which will still affect the performance of the electrode and battery.

[0004] In addition, the electrostatic interaction between low-polarity solvent molecules is small, and its dispersion ability for high-polarity inorganic particles (such as oxide positive electrode active materials and sulfide solid electrolyte particles) is weak. Therefore, the sulfide solid electrolyte particles in the slurry are easily agglomerated and settled, resulting in poor storage stability of the slurry and poor consistency of the prepared electrodes, which in turn affects the consistency of the prepared battery. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the purpose of the present invention is to propose a sulfide solid electrolyte and its preparation method and application. The sulfide solid electrolyte modified by pseudo-halogen atomic groups of the present invention has significantly improved ability to withstand organic solvent erosion; at the same time, due to the presence of pseudo-halogen groups on the surface of the sulfide solid electrolyte that are more affinity with organic solvents, the oil absorption value OA of the electrolyte can be improved to a certain extent, and the dispersion ability of the electrolyte in the slurry is improved, thereby improving the stability and thixotropy of the sulfide solid electrolyte in the electrolyte slurry, and also increasing the solid content of the electrolyte slurry, thereby improving the first-cycle discharge capacity, first coulomb efficiency and cycle life of the solid-state battery.

[0006] In one aspect of the present invention, the present invention provides a sulfide solid electrolyte. According to an embodiment of the present invention, the sulfide solid electrolyte comprises:

[0007] The core layer comprises a structural formula of Li 6-a PS 5-a X 1+a At least one of the compounds, X is a halogen atom, a = 0 to 1; a shell layer, the shell layer is arranged on at least a portion of the surface of the core layer, the shell layer includes a structural formula of Li 6-a PS 5-a X 1+a-b Y b At least one of the compounds, Y is a pseudo-halogen atomic group, and b=0.1 to 0.9.

[0008] According to the sulfide solid electrolyte of the embodiment of the present invention, the ability of the sulfide solid electrolyte to withstand corrosion by organic solvents after replacement with pseudo-halogen atomic groups is significantly improved; at the same time, due to the presence of pseudo-halogen groups on the surface of the sulfide solid electrolyte that are more affinity with organic solvents, the oil absorption value OA of the electrolyte can be improved to a certain extent, so that the surface of the electrolyte can adsorb more solvent molecules, thereby improving the dispersion ability of the electrolyte in the slurry, thereby improving the stability and thixotropy of the sulfide solid electrolyte in the electrolyte slurry, and also improving the solid content of the electrolyte slurry, thereby improving the first-cycle discharge capacity, first coulomb efficiency and cycle life of the solid-state battery.

[0009] In addition, the sulfide solid electrolyte according to the above embodiment of the present invention may also have the following additional technical features: in some embodiments of the present invention, Y includes at least one of cyanide, isocyanate, mercapto, cyanic acid, isocyanate, thiocyanate and isothiocyanate; and / or, X is F, Cl, Br or I.

[0010] In some embodiments of the present invention, the particle size D50 of the sulfide solid electrolyte is 0.1 μm to 50 μm; and / or the thickness of the shell layer is 1 nm to 100 nm.

[0011] In some embodiments of the present invention, the ionic conductivity of the sulfide solid electrolyte is 0.1 mS / cm to 10 mS / cm.

[0012] In some embodiments of the present invention, the oil absorption value OA of the sulfide solid electrolyte is 0.9 mL / g to 1.5 mL / g; and / or the ratio of the oil absorption value OA of the sulfide solid electrolyte to the specific surface area SSA of the sulfide solid electrolyte is 0.1 mL / m 2 ~0.5mL / m 2 .

[0013] In a second aspect of the present invention, a method for preparing a sulfide solid electrolyte is provided. According to an embodiment of the present invention, the method comprises:

[0014] (1) Obtain the structural formula Li 6-a PS 5-a X 1+a electrolyte, X is a halogen atom, a=0~1;

[0015] (2) The electrolyte Li 6-a PS 5-a X 1+a immersed in LiY solution so that the electrolyte Li 6-a PS 5-a X 1+a The surface layer forms a compound Li 6-a PS 5-a X 1+a-b Y b , Y is a pseudo-halogen atomic group, b = 0.1 to 0.9;

[0016] (3) performing solid-liquid separation on the mixture obtained by the reaction in step (2) to obtain a solid phase, and drying the solid phase to obtain the sulfide solid electrolyte.

[0017] According to the method for preparing a sulfide solid electrolyte according to an embodiment of the present invention, a pseudohalogen group having chemical properties very close to those of halogen is introduced into the surface layer of the sulfide solid electrolyte to replace the compound Li 6-a PS 5-a X 1+a By adding the halogen atom X in the electrolyte, a sulfide solid electrolyte with a core-shell structure is obtained, thereby improving the ability of the sulfide solid electrolyte to withstand erosion by organic solvents; at the same time, due to the presence of pseudo-halogen groups on the surface of the sulfide solid electrolyte that are more affinity with organic solvents, the oil absorption value OA of the electrolyte can be improved to a certain extent, so that the surface of the electrolyte can adsorb more solvent molecules, thereby improving the dispersion ability of the electrolyte in the slurry, thereby improving the stability and thixotropy of the sulfide solid electrolyte in the electrolyte slurry, and also increasing the solid content of the electrolyte slurry, thereby improving the first-cycle discharge capacity, first coulomb efficiency and cycle life of the solid-state battery.

[0018] In addition, the method according to the above embodiment of the present invention may also have the following additional technical features:

[0019] In some embodiments of the present invention, the hard carbon material precursor comprises crushed tailings of hard carbon material, and the soft carbon material precursor comprises high-sulfur asphalt, wherein the sulfur content of the high-sulfur asphalt is 2%-4%.

[0020] In some embodiments of the present invention, in step (2), LiY includes at least one of LiCN, LiNC, LiSH, LiOCN, LiNCO, LiSCN and LiNCS; and / or, the concentration of the LiY solution is 0.0001 mol / L-1 mol / L; and / or, in step (2), the solvent in the LiY solution includes at least one of an alcohol solvent, an ester solvent, and an ether solvent; and / or, in step (2), the infiltration and stirring time is 0.5 min to 120 min.

[0021] In some embodiments of the present invention, in step (1), compound Li is prepared 6-a PS 5-a X 1+a The steps include:

[0022] (1-1) Li2S, LiCl, and P2S5 are mixed uniformly in an oxygen-free and water-free environment to obtain a mixed powder;

[0023] (1-2) sintering the mixed powder at a temperature of 300°C to 550°C in an oxygen-free and water-free environment to obtain the compound Li 6-a PS 5-a X 1+a .

[0024] In some embodiments of the present invention, in step (1-1), according to compound Li 6-a PS 5-a X 1+a Li2S, LiCl and P2S5 are weighed in the stoichiometric ratio of each element; and / or, in step (1-2), the sintering temperature is 1h to 24h.

[0025] In its third aspect, the present invention provides a positive electrode sheet. According to an embodiment of the present invention, the positive electrode sheet comprises the sulfide solid electrolyte of the above embodiment or the sulfide solid electrolyte produced by the method of the above embodiment. This improves the stability and thixotropy of the positive electrode slurry containing the sulfide solid electrolyte, thereby enhancing the quality of the positive electrode sheet.

[0026] In its fourth aspect, the present invention provides a solid-state battery. According to embodiments of the present invention, the solid-state battery comprises the sulfide solid electrolyte of the above embodiments, or the sulfide solid electrolyte produced by the method of the above embodiments. This improves the first-cycle discharge capacity, first-cycle coulombic efficiency, and cycle life of the solid-state battery.

[0027] In a fifth aspect, the present invention provides an electrical device. According to an embodiment of the present invention, the electrical device comprises a solid-state battery as described above. As a result, the electrical device possesses all the advantages of a sodium-ion solid-state battery, which will not be further elaborated here.

[0028] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments with reference to the following drawings, in which:

[0030] Figure 1 Schematic diagram of the structure of a sulfide solid electrolyte according to an embodiment of the present invention.

[0031] Reference numerals:

[0032] 1-shell; 2-core. DETAILED DESCRIPTION

[0033] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0034] In one aspect of the present invention, the present invention provides a sulfide solid electrolyte. Figure 1 The sulfide solid electrolyte includes: a core layer 2, the core layer 2 includes a structural formula of Li 6-a PS 5-a X 1+a At least one of the compounds, X is a halogen atom, a = 0 to 1; shell 1, shell 1 is arranged on at least part of the surface of the core layer 2, and shell 1 includes a structural formula of Li 6-a PS 5-a X 1+a-b Y b At least one of the compounds, Y is a pseudo-halogen atomic group, and b=0.1 to 0.9. As a result, the ability of the sulfide solid electrolyte modified by pseudo-halogen atomic group substitution of the present invention to withstand organic solvent erosion is significantly improved; at the same time, due to the presence of pseudo-halogen groups on the surface of the sulfide solid electrolyte that are more compatible with organic solvents, the oil absorption value OA of the electrolyte can be improved to a certain extent, so that the surface of the electrolyte can adsorb more solvent molecules, thereby improving the dispersion ability of the electrolyte in the slurry, thereby improving the stability and thixotropy of the sulfide solid electrolyte in the electrolyte slurry, and also increasing the solid content of the electrolyte slurry, thereby improving the first-cycle discharge capacity, first coulomb efficiency and cycle life of the solid-state battery.

[0035] The following is a detailed explanation of the principle by which the sulfide solid electrolyte proposed in the present invention can achieve the above beneficial effects:

[0036] In the related technology, a sulfide solid electrolyte slurry formed by a low-polarity, aprotic solvent is used. The attenuation of the ionic conductivity of the sulfide solid electrolyte is more obvious, which will affect the quality of the electrode and the electrolyte membrane, and thus affect the performance of the battery.

[0037] In addition, the electrostatic interaction between low-polarity solvent molecules is small, and its ability to disperse high-polarity sulfide solid electrolyte particles is weak. Therefore, the sulfide solid electrolyte particles in the slurry are easily agglomerated and settled, resulting in poor storage stability of the slurry. The prepared electrodes have poor consistency, which in turn affects the consistency of the prepared battery.

[0038] In order to solve the above problems, the present invention introduces pseudohalogen groups with chemical properties very close to those of halogens on the surface of the sulfide solid electrolyte to replace the compound Li 6-a PS 5-a X 1+a The halogen atom X in the electrolyte is used to obtain a sulfide solid electrolyte with a core-shell structure, the core layer of which is still composed of Li 6-a PS 5-a X 1+a , the shell component is Li 6-a PS 5-a X 1+a-b Y b , wherein Y is a pseudo-halogen atomic group, which is more compatible with organic solvents. Therefore, the ability of the sulfide solid electrolyte modified by pseudo-halogen atomic groups to withstand organic solvent erosion is significantly improved; at the same time, due to the presence of pseudo-halogen groups on the surface of the sulfide solid electrolyte that are more compatible with organic solvents, the oil absorption value OA of the electrolyte can be improved to a certain extent, so that the surface of the electrolyte can adsorb more solvent molecules, thereby improving the dispersion ability of the electrolyte in the slurry, thereby improving the stability and thixotropy of the sulfide solid electrolyte in the electrolyte slurry, and also increasing the solid content of the electrolyte slurry, thereby improving the first-cycle discharge capacity, first coulomb efficiency and cycle life of the solid-state battery.

[0039] In addition, pseudohalogen groups have certain similarities with halogen atoms in many chemical properties. Therefore, partial substitution of halogen atoms is beneficial to the argyrodite electrolyte Li 6-a PS 5-a X 1+a Surface modification will not lead to significant changes in the ionic conductivity of the sulfide solid electrolyte powder.

[0040] According to some specific embodiments of the present invention, Y may include at least one of cyanogen (CN), isocyanate (NC), mercapto (SH), cyanic acid (OCN), isocyanate (NCO), thiocyanate (SCN), and isothiocyanate (NCS); and / or, X may be F, Cl, Br, or I. As a result, the aforementioned pseudo-halogen atoms are more compatible with organic solvents, further improving the ability of the sulfide solid electrolyte to withstand corrosion by organic solvents, and at the same time, further improving the oil absorption value OA of the electrolyte, thereby further improving the stability and thixotropy of the sulfide solid electrolyte in the electrolyte slurry.

[0041] According to some further specific embodiments of the present invention, the particle size D50 of the sulfide solid electrolyte can be 0.1 μm to 50 μm, preferably 500 nm to 3 μm. The thickness of the shell layer can be 1 nm to 100 nm. By limiting the thickness of the shell layer to the above range, the ability of the sulfide solid electrolyte to withstand organic solvent corrosion and the stability and thixotropy of the sulfide solid electrolyte in the electrolyte slurry are further ensured, while avoiding the negative effects caused by excessive modification of the pseudo-halogen atomic group Y. Preferably, the thickness of the shell layer can be 5 nm to 30 nm.

[0042] According to further specific embodiments of the present invention, the ionic conductivity of the sulfide solid electrolyte can be 0.1 mS / cm to 10 mS / cm. Thus, the sulfide solid electrolyte of the present invention has relatively excellent ionic conductivity. Preferably, the ionic conductivity of the sulfide solid electrolyte can be 2 mS / cm to 10 mS / cm.

[0043] According to further specific embodiments of the present invention, the oil absorption value OA of the sulfide solid electrolyte can be 0.9 mL / g to 1.5 mL / g, thereby improving the wettability of the sulfide solid electrolyte in organic solvents, thereby improving the dispersion ability of the electrolyte in the slurry, thereby improving the stability and thixotropy of the sulfide solid electrolyte in the electrolyte slurry, and also increasing the solid content of the electrolyte slurry. The oil absorption value OA of the sulfide solid electrolyte is preferably 1.1 mL / g to 1.5 mL / g.

[0044] According to some specific embodiments of the present invention, the ratio of the oil absorption value OA of the sulfide solid electrolyte to the specific surface area SSA of the sulfide solid electrolyte OA / SSA can be 0.1 mL / m 2 ~0.5mL / m 2The inventors found that the OA value and OA / SSA value should be within a moderate range. Too low a value will lead to poor dispersion of the sulfide solid electrolyte in the solvent, resulting in poor stability of the slurry; too high a value will lead to a low solid content of the prepared electrolyte slurry, which will have an adverse effect on the electrode structure of the electrode and battery performance. Preferably, OA / SSA can be 0.10mL / m 2 ~0.25mL / m 2 .

[0045] In a second aspect of the present invention, the present invention provides a method for preparing the sulfide solid electrolyte of the above embodiment. According to an embodiment of the present invention, the method comprises:

[0046] S100: Get the structural formula of Li 6-a PS 5-a X 1+a electrolytes

[0047] In this step, the structural formula is Li 6-a PS 5-a X 1+a The electrolyte of X is a halogen atom, and a=0 to 1. Li can be prepared by solid phase ball milling-sintering method or wet dissolution-crystallization-sintering synthesis method. 6-a PS 5-a X 1+a The electrolyte is preferably synthesized by a wet dissolution-crystallization-sintering method.

[0048] Specifically, the solid phase ball milling-sintering method is as follows:

[0049] In an oxygen-free and water-free environment, Li2S, LiCl and P2S5 are placed in a sealed zirconia-lined ball mill jar and ball milled at a speed of 100RPM to 2000RPM for 1h to 24h. The powder is taken out and pressed into a dense powder cake using a powder cold press at a pressure of 400MPa to 600MPa. The powder cake is then sealed in a vacuum quartz tube and placed in a muffle furnace and sintered at a temperature of 300℃ to 550℃ for 1h to 24h. Li2S, LiCl and P2S5 react to form the compound Li 6-a PS 5-a X 1+a ; Take out the powder cake and crush it into powder to obtain electrolyte Li 6-a PS 5-a X 1+a .

[0050] The wet dissolution-crystallization-sintering method is as follows:

[0051] In an oxygen-free and water-free environment, Li2S, LiCl and P2S5 are mixed in a solvent and fully stirred to dissolve Li2S, LiCl and P2S5; after the dissolution is completed, the solvent is slowly evaporated at 70°C to 100°C to allow the solute to slowly precipitate; after the precipitation is complete, the collected solute is placed in a vacuum tube furnace and sintered at a temperature of 300°C to 550°C for 1h to 24h, and Li2S, LiCl and P2S5 react to generate the compound Li 6-a PS 5-a X 1+a , take out and get the electrolyte Li 6-a PS 5-a X 1+a .

[0052] It is understandable that the above-mentioned oxygen-free and water-free environment refers to an environment without water or oxygen or containing a small amount of acceptable water vapor and / or oxygen, such as an Ar gas environment glove box or a -40°C dew point air environment.

[0053] The type of solvent used in the wet dissolution-crystallization-sintering method is not particularly limited. As some specific examples, the solvent may include at least one of tetrahydrofuran (THF), acetonitrile (ACN), isopropyl alcohol (IPA), and propanol (PA).

[0054] According to some specific embodiments of the present invention, in the solid phase ball milling-sintering method and the wet dissolution-crystallization-sintering method, the compound Li 6-a PS 5-a X 1+a Weigh the masses of Li2S, LiCl and P2S5 according to the stoichiometric ratio of each element.

[0055] S200: In electrolyte Li 6-a PS 5-a X 1+a The surface layer forms a compound Li 6-a PS 5-a X 1+a-b Y b

[0056] In this step, the electrolyte Li 6-a PS 5-a X 1+a Immerse in LiY solution, soak and stir to make the electrolyte Li 6-a PS 5- a X 1+a Some of the halogen atoms X in the surface layer exchange with the solute ions in the LiY solution so that 6- a PS 5-a X 1+aThe surface layer forms a compound Li 6-a PS 5-a X 1+a-b Y b , Y is a pseudo-halogen atomic group, b = 0.1 ~ 0.9.

[0057] According to some specific embodiments of the present invention, LiY includes at least one of LiCN, LiNC, LiSH, LiOCN, LiNCO, LiSCN and LiNCS.

[0058] According to some specific embodiments of the present invention, the concentration of the above-mentioned LiY solution can be 0.0001mol / L-1mol / L, preferably 0.005mol / L-0.5mol / L. Thus, by limiting the concentration of the above-mentioned LiY solution to the above-mentioned range, the electrolyte Li 6-a PS 5-a X 1+a Some of the halogen atoms X in the surface layer can exchange with the solute ions in the LiY solution to form a 6-a PS 5-a X 1+a The surface layer forms a compound Li 6-a PS 5-a X 1+a-b Y b , Y is a pseudohalogen atomic group.

[0059] In the embodiments of the present invention, the specific type of the solvent in the above-mentioned LiY solution is not particularly limited, and those skilled in the art can select it according to actual needs. As some preferred solutions, the solvent in the LiY solution can include at least one of an alcohol solvent, an ester solvent, and an ether solvent.

[0060] According to some specific embodiments of the present invention, the time of soaking and stirring can be 0.5min to 120min, preferably 5min to 40min, thereby ensuring that the electrolyte Li 6-a PS 5-a X 1+a The surface layer forms a suitable thickness of compound Li 6- a PS 5-a X 1+a-b Y b , thereby further ensuring the ability of the sulfide solid electrolyte to withstand corrosion by organic solvents and the stability and thixotropy of the sulfide solid electrolyte in the electrolyte slurry, while avoiding the negative effects caused by excessive modification of the pseudo-halogen atomic group Y.

[0061] S300: solid-liquid separation, drying

[0062] In this step, after step S200 is completed, a high-speed centrifuge is used to separate the solid-liquid mixture obtained by the reaction in step S200 to obtain a solid phase, and the solid phase portion is dried (for example, the solid phase portion is heat-treated in a vacuum tube furnace at a temperature of 90°C to 200°C for 1h to 24h) to obtain a sulfide solid electrolyte.

[0063] According to the method for preparing a sulfide solid electrolyte according to an embodiment of the present invention, a pseudohalogen group having chemical properties very close to those of halogen is introduced into the surface layer of the sulfide solid electrolyte to replace the compound Li 6-a PS 5-a X 1+a By adding the halogen atom X in the electrolyte, a sulfide solid electrolyte with a core-shell structure is obtained, thereby improving the ability of the sulfide solid electrolyte to withstand erosion by organic solvents; at the same time, due to the presence of pseudo-halogen groups on the surface of the sulfide solid electrolyte that are more affinity with organic solvents, the oil absorption value OA of the electrolyte can be improved to a certain extent, so that the surface of the electrolyte can adsorb more solvent molecules, thereby improving the dispersion ability of the electrolyte in the slurry, thereby improving the stability and thixotropy of the sulfide solid electrolyte in the electrolyte slurry, and also increasing the solid content of the electrolyte slurry, thereby improving the first-cycle discharge capacity, first coulomb efficiency and cycle life of the solid-state battery.

[0064] In its third aspect, the present invention provides a positive electrode sheet. According to an embodiment of the present invention, the positive electrode sheet comprises the sulfide solid electrolyte of the above embodiment or the sulfide solid electrolyte produced by the method of the above embodiment. This improves the stability and thixotropy of the positive electrode slurry containing the sulfide solid electrolyte, thereby enhancing the quality of the positive electrode sheet.

[0065] Specifically, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer. The positive electrode active material layer is disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a sulfide solid electrolyte, a positive electrode binder, and a conductive agent. The mass content of the positive electrode active material can be 40% to 95%, the mass content of the sulfide solid electrolyte can be 5% to 60%, and the mass content of the conductive agent can be 0% to 10%.

[0066] In an embodiment of the present invention, the specific type of the above-mentioned positive electrode current collector is not particularly limited. For example, a metal foil, a porous metal plate or a composite current collector can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PYT), polystyrene (PS), polyethylene (PE), etc.) on a substrate.

[0067] Similarly, the specific types of the above-mentioned positive electrode active materials are not particularly limited. As some specific examples, the positive electrode active materials may include olivine (such as LiFePO4, etc.), layered oxides (such as NCM, NCA or LiCoO2, etc.), spinels (such as LiMn2O4, Li4Ti5O 12 The conductive agent may be selected from commonly used conductive agents for positive electrodes, such as acetylene black, carbon nanotubes, carbon fibers, carbon black, etc. The binder may be selected from commonly used binders for positive electrodes. For example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0068] In some embodiments of the present application, the positive electrode sheet can be prepared by the following method: the above-mentioned components for preparing the positive electrode sheet, such as the positive electrode active material, the sulfide solid electrolyte, the positive electrode binder and the conductive agent are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0069] In its fourth aspect, the present invention provides a solid-state battery. According to embodiments of the present invention, the solid-state battery comprises the sulfide solid electrolyte of the above embodiments, or the sulfide solid electrolyte produced by the method of the above embodiments. This improves the first-cycle discharge capacity, first-cycle coulombic efficiency, and cycle life of the solid-state battery.

[0070] Specifically, the solid-state battery includes a positive electrode sheet, a negative electrode sheet, and a solid electrolyte layer, wherein the solid electrolyte layer is disposed between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet may include the sulfide solid electrolyte of the above embodiment or the sulfide solid electrolyte prepared by the method of the above embodiment; and / or the negative electrode sheet may include the sulfide solid electrolyte of the above embodiment or the sulfide solid electrolyte prepared by the method of the above embodiment; and / or the solid electrolyte layer may include the sulfide solid electrolyte of the above embodiment or the sulfide solid electrolyte prepared by the method of the above embodiment.

[0071] The solid-state batteries described above may be in the form of battery cells, battery modules, and battery packs. In some embodiments, battery cells may be assembled into battery modules, each of which may contain one or more battery cells, the specific number of which may be selected by those skilled in the art based on the application and capacity of the battery module. In some embodiments, battery modules may also be assembled into battery packs, each of which may contain one or more battery modules, the specific number of which may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0072] In a fifth aspect, the present invention provides an electrical device. According to an embodiment of the present invention, the electrical device comprises a solid-state battery as described above. Thus, the electrical device has all the advantages of a solid-state battery, which will not be further elaborated here.

[0073] Specifically, the above-mentioned electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery-powered vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.

[0074] The following examples of the present invention are described in detail. It should be noted that the following examples are illustrative and are intended only to explain the present invention and are not to be construed as limiting the present invention. In addition, unless otherwise expressly stated, all reagents used in the following examples are commercially available or can be synthesized according to methods described herein or known methods. Reaction conditions not listed are also readily available to those skilled in the art.

[0075] Example 1

[0076] 1) Preparation of basic electrolyte:

[0077] In an Ar atmosphere glove box, 20.70 g of Li2S, 7.90 g of LiCl, and 21.40 g of P2S5 were accurately weighed according to the chemical composition of Li6PS5Cl and fully dissolved in a sufficient amount of anhydrous ethanol / tetrahydrofuran (the mass ratio of anhydrous ethanol to tetrahydrofuran was 1:1) mixed solution. After being fully dissolved, stirring was continued for 6 h to ensure thorough mixing. The solvent was then slowly evaporated at 85°C to allow the solute to slowly precipitate. After complete precipitation, the collected solute was placed in a vacuum tube furnace and sintered at 350°C for 5 h. The basic electrolyte sample Li6PS5Cl was obtained.

[0078] 2) Electrolyte surface treatment:

[0079] The obtained electrolyte sample was immersed in a sufficient amount of 0.01 mol / L LiSCN isopropyl alcohol PA solution, stirred for 20 minutes, separated by a centrifuge, and dried to obtain a treated electrolyte sample.

[0080] XPS was used to characterize the shell composition of the electrolyte sample of this embodiment, and the shell chemical formula was obtained as follows: Li6PS5Cl 0.7 SCN 0.3 The thickness of the shell is shown in Table 1.

[0081] The particle size D50 of the electrolyte sample was measured using a laser particle size analyzer (Mastersizer 3000). The results are shown in Table 1.

[0082] Example 2

[0083] The difference between this embodiment and embodiment 1 is that:

[0084] LiNCS was used instead of LiSCN. Other contents were the same as those in Example 1.

[0085] XPS was used to characterize the shell composition of the electrolyte sample of this embodiment, and the shell chemical formula was obtained as follows: Li6PS5Cl 0.7 NCS 0.3 The thickness of the shell is shown in Table 1.

[0086] The particle size D50 of the electrolyte sample was measured using a laser particle size analyzer (Mastersizer 3000). The results are shown in Table 1.

[0087] Example 3

[0088] The difference between this embodiment and embodiment 1 is that:

[0089] LiOCN was used instead of LiSCN. Other contents were the same as those in Example 1.

[0090] XPS was used to characterize the shell composition of the electrolyte sample of this embodiment, and the shell chemical formula was obtained as follows: Li6PS5Cl 0.7 OCN 0.3 The thickness of the shell is shown in Table 1.

[0091] The particle size D50 of the electrolyte sample was measured using a laser particle size analyzer (Mastersizer 3000). The results are shown in Table 1.

[0092] Example 4

[0093] The difference between this embodiment and embodiment 1 is that:

[0094] EtOH was used instead of PA. Other contents were the same as those in Example 1.

[0095] XPS was used to characterize the shell composition of the electrolyte sample of this embodiment, and the shell chemical formula was obtained as follows: Li6PS5Cl 0.65 SCN 0.35 The thickness of the shell is shown in Table 1.

[0096] The particle size D50 of the electrolyte sample was measured using a laser particle size analyzer (Mastersizer 3000). The results are shown in Table 1.

[0097] Example 5

[0098] The difference between this embodiment and embodiment 1 is that:

[0099] According to Li 5.7 PS 4.7 Cl 1.3 The chemical composition of Li2S was accurately weighed 18.91g, LiCl 10.31g and P2S5 20.78g. 5.7 PS 4.7 Cl 1.3 Electrolyte. The electrolyte sample after surface treatment is Li 5.7 PS 4.7 Cl 1.3-b SCN b .

[0100] The rest of the contents are the same as those in Example 1.

[0101] XPS was used to characterize the shell composition of the electrolyte sample of this embodiment, and the shell chemical formula was obtained as follows: Li 5.7 PS 4.7 Cl 0.9 SCN 0.4 The thickness of the shell is shown in Table 1.

[0102] The particle size D50 of the electrolyte sample was measured using a laser particle size analyzer (Mastersizer 3000). The results are shown in Table 1.

[0103] Example 6

[0104] The difference between this embodiment and embodiment 1 is that:

[0105] According to Li 5.7 PS 4.7 Cl 1.3 The chemical composition of Li2S was accurately weighed 18.91g, 10.31g, LiCl and 20.78g, P2S5. 5.7 PS 4.7 Cl1.3 The electrolyte sample after surface treatment is Li 5.7 PS 4.7 Cl 1.3-b NCO b .

[0106] The rest of the contents are the same as those in Example 1.

[0107] XPS was used to characterize the shell composition of the electrolyte sample of this embodiment, and the shell chemical formula was obtained as follows: Li 5.7 PS 4.7 Cl 0.9 NCO 0.4 The thickness of the shell is shown in Table 1.

[0108] The particle size D50 of the electrolyte sample was measured using a laser particle size analyzer (Mastersizer 3000). The results are shown in Table 1.

[0109] Example 7

[0110] The difference between this embodiment and embodiment 1 is that:

[0111] Step 2) The time for the electrolyte surface treatment was changed to 10 min. Other contents were the same as those in Example 1.

[0112] XPS was used to characterize the shell composition of the electrolyte sample of this embodiment, and the shell chemical formula was obtained as follows: Li6PS5Cl 0.8 SCN 0.2 The thickness of the shell is shown in Table 1.

[0113] The particle size D50 of the electrolyte sample was measured using a laser particle size analyzer (Mastersizer 3000). The results are shown in Table 1.

[0114] Example 8

[0115] The difference between this embodiment and embodiment 1 is that:

[0116] The time for the electrolyte surface treatment in step 2) was changed to 40 min. Other contents were the same as those in Example 1.

[0117] XPS was used to characterize the shell composition of the electrolyte sample of this embodiment, and the shell chemical formula was obtained as follows: Li6PS5Cl 0.5 SCN 0.5 The thickness of the shell is shown in Table 1.

[0118] The particle size D50 of the electrolyte sample was measured using a laser particle size analyzer (Mastersizer 3000). The results are shown in Table 1.

[0119] Example 9

[0120] The difference between this embodiment and embodiment 1 is that:

[0121] Step 2) The concentration of the solution was 0.1 mol; the surface treatment time was changed to 5 min. Other contents were the same as in Example 1.

[0122] XPS was used to characterize the shell composition of the electrolyte sample of this embodiment, and the shell chemical formula was obtained as follows: Li6PS5Cl 0.8 SCN 0.2 The thickness of the shell is shown in Table 1.

[0123] The particle size D50 of the electrolyte sample was measured using a laser particle size analyzer (Mastersizer 3000). The results are shown in Table 1.

[0124] Example 10

[0125] The difference between this embodiment and embodiment 1 is that:

[0126] Step 2) The concentration of the solution was 0.5 mol; the surface treatment time was changed to 1 min.

[0127] The rest of the contents are the same as those in Example 1.

[0128] XPS was used to characterize the shell composition of the electrolyte sample of this embodiment, and the shell chemical formula was obtained as follows: Li6PS5Cl 0.7 SCN 0.3 The thickness of the shell is shown in Table 1.

[0129] The particle size D50 of the electrolyte sample was measured using a laser particle size analyzer (Mastersizer 3000). The results are shown in Table 1.

[0130] Comparative Example 1

[0131] The difference between this comparative example and Example 1 is only that:

[0132] The surface treatment of the electrolyte in step 2) is eliminated.

[0133] The rest of the contents are the same as those in Example 1.

[0134] Comparative Example 2

[0135] The difference between this comparative example and Example 5 is only that:

[0136] The surface treatment of the electrolyte in step 2) is eliminated.

[0137] The rest of the contents are the same as those in Example 5.

[0138] The parameters of Examples 1-10 and Comparative Examples 1-2 are shown in Table 1.

[0139] Table 1

[0140]

[0141]

[0142] Performance test items:

[0143] 1) Electrolyte oil absorption value OA and specific surface area SSA test:

[0144] The oil absorption values ​​OA of the solid electrolyte powders of Examples 1-10 and Comparative Examples 1-2 were tested using an oil absorption value tester (ASAHI-S500). The results are shown in Table 2.

[0145] The specific surface areas SSA of the solid electrolyte powders of Examples 1-10 and Comparative Examples 1-2 were respectively tested using a specific surface area tester (BET model Autosorb-iQ). The results are shown in Table 2.

[0146] 2) Test of electrolyte solvent stability:

[0147] In an Ar atmosphere, an appropriate amount of electrolyte sample was taken to test its initial conductivity. 1g of electrolyte powder was placed in 5mL of xylene, anisole, and butyl butyrate, respectively, and stirred thoroughly at room temperature for 2h. The solvents were then dried at 100°C. The ionic conductivity of the electrolyte after immersion in each of the three solvents was measured, and the ratio of the electrolyte ionic conductivity after immersion to the initial value was calculated. The results are shown in Table 3. The closer the ratio is to 1, the better the stability of the electrolyte solvent.

[0148] The test method for the ionic conductivity of the electrolyte is as follows:

[0149] 100 mg of electrolyte powder was weighed in a glove box under argon atmosphere. The solid-state battery mold is pressed into an electrolyte sheet at 120MPa, and then two electrolyte sheets are added on each side. The carbon-coated aluminum foil of 1.5-1.5-meter size was pressed again to 600 MPa to obtain a symmetrical battery with a carbon-coated aluminum foil | solid electrolyte | carbon-coated aluminum foil structure. The battery impedance was tested using an electrochemical workstation EIS, and the ionic conductivity of the electrolyte was calculated.

[0150] 3) Stability and thixotropy test of electrolyte slurry:

[0151] Accurately weigh 10 g of electrolyte sample, 1.5 g of 10% NBR xylene solution, and 5.42 g of xylene, and place them together with 15 g of ZrO2 ball milling beads in a ZrO2-lined ball mill jar, and mix them at a speed of 900 RPM for 30 minutes to obtain an electrolyte slurry.

[0152] The stability and thixotropy of the electrolyte slurry can be tested by rheometer. The stability test requires taking the freshly prepared electrolyte slurry (0h) and the electrolyte slurry stored for 24h to test their rheological curves respectively, and record the rheological curves of the two electrolyte slurries in 1s. -1 The viscosity η 0h and η 24h , calculate η 24h / η 0h The closer the ratio of the two is to 100%, the more stable the slurry is. Thixotropy can test the rheological curve of the electrolyte slurry at 0h and record the slurry at 1s. -1 and 50s -1 The viscosity values ​​η1 and η 50 , calculate 1-(η 50 The value of η / η1) is shown in Table 4. The thixotropy is preferably around 0.7.

[0153] 4) Positive electrode coating and testing

[0154] Accurately weigh 5g of electrolyte sample, 20g of NCM955 positive electrode material, 0.125g of conductive agent Sup P, 3.75g of 10% NBR xylene solution, 13.54g of xylene, and 25g of ZrO2 ball milling beads and place them together in a ZrO2-lined ball mill jar, mix at a speed of 900RPM for 30min to obtain the positive electrode slurry.

[0155] A coating machine was used to coat the composite positive electrode sheet, and a powder battery was used to test the electrochemical performance of the sheet. Specifically, a lithium-indium alloy (lithium content of 5%) was used as the counter electrode. The composite positive electrode sheet and the lithium-indium alloy sheet were cut into 15mm small discs, 200mg of electrolyte powder was weighed in an argon atmosphere glove box, and a 15mm mold was used to press the electrolyte sheet at 120MPa. The electrode disc was added to one side of the electrolyte sheet and a pressure of 380MPa was applied as the working electrode. The lithium-indium alloy sheet was placed on the other side as the counter electrode to assemble into a half-cell. The mold battery assembled by the above method was subjected to constant current charge and discharge tests using the Land multi-channel charge and discharge test system (LAND CT2001A). The test results are shown in Table 5.

[0156] Table 2

[0157]

[0158] Table 3

[0159]

[0160]

[0161] Table 4

[0162]

[0163] Table 5

[0164]

[0165]

[0166] As can be seen from Table 2, the electrolyte oil absorption values ​​OA of Examples 1-10 are all in the range of 1.1-1.5 mL / g, and the OA / SSA ratios are all in the range of 0.13-0.21 mL / m 2 It can be seen that the surface-treated electrolytes of Examples 1-10 of the present invention have good dispersibility in the slurry, good stability, and high solid content. However, the oil absorption values ​​OA and OA / SSA ratios of the electrolytes without surface treatment of Comparative Examples 1 and 2 are both low, indicating that the electrolytes of Comparative Examples 1 and 2 have poor dispersibility and poor stability.

[0167] As can be seen from Table 3, the ratios of the electrolyte ion conductivities of the surface-treated electrolytes of Examples 1-10 before and after immersion in the three solvents of xylene, anisole, and butyl butyrate to the initial values ​​were all above 85%, demonstrating good electrolyte solvent stability. In contrast, the ratios of the electrolyte ion conductivities of the untreated electrolytes of Comparative Examples 1 and 2 before and after immersion in the three solvents of xylene, anisole, and butyl butyrate to the initial values ​​were all below 70%, demonstrating poor electrolyte solvent stability.

[0168] As can be seen from Table 4, the η of the slurries formed by the surface-treated electrolytes of Examples 1-10 is 24h / η 0h are all close to 100%, and the 1-(η 50 The values ​​of η1) are all close to 70%, which proves that the stability and thixotropy are excellent. 24h / η 0h were significantly higher than 100%, and 1-(η 50 The values ​​of / η1) are significantly higher by 70%, indicating that its stability and thixotropy are poor.

[0169] As can be seen from Table 5, compared with Comparative Examples 1-2, the first cycle discharge capacity, first coulombic efficiency and cycle life of the half-cell formed by the surface-treated electrolyte of Examples 1-10 are significantly improved.

[0170] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0171] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A sulfide solid electrolyte, characterized in that: include: The core layer comprises a structural formula of Li 6-a PS 5-a X 1+a At least one of the compounds, X is a halogen atom, a = 0 to 1; Shell layer, the shell layer is arranged on at least part of the surface of the core layer, and the shell layer includes a structural formula of Li 6-a PS 5- a X 1+a-b Y b At least one of the compounds, Y is a pseudo-halogen atomic group, and b=0.1 to 0.

9.

2. The sulfide solid electrolyte according to claim 1, characterized in that Y includes at least one of cyanide, isocyanide, mercapto, cyanic acid, isocyanate, thiocyanate and isothiocyanate; and / or, X is F, Cl, Br or I.

3. The sulfide solid electrolyte according to claim 1, characterized in that The particle size D50 of the sulfide solid electrolyte is 0.1 μm to 50 μm; And / or, the thickness of the shell layer is 1 nm to 100 nm.

4. The sulfide solid electrolyte according to any one of claims 1 to 3, characterized in that The ionic conductivity of the sulfide solid electrolyte is 0.1 mS / cm to 10 mS / cm.

5. The sulfide solid electrolyte according to any one of claims 1 to 3, characterized in that The oil absorption value OA of the sulfide solid electrolyte is 0.9 mL / g to 1.5 mL / g; And / or, the ratio of the oil absorption value OA of the sulfide solid electrolyte to the specific surface area SSA of the sulfide solid electrolyte is 0.1 mL / m 2 ~0.5mL / m 2 .

6. A method for preparing a sulfide solid electrolyte, characterized in that: include: (1) Obtain the structural formula Li 6-a PS 5-a X 1+a electrolyte, X is a halogen atom, a=0~1; (2) The electrolyte Li 6-a PS 5-a X 1+a immersed in LiY solution so that the electrolyte Li 6-a PS 5-a X 1+a The surface layer forms a compound Li 6-a PS 5-a X 1+a-b Y b , Y is a pseudo-halogen atomic group, b = 0.1 to 0.9; (3) performing solid-liquid separation on the mixture obtained by the reaction in step (2) to obtain a solid phase, and drying the solid phase to obtain the sulfide solid electrolyte.

7. The method according to claim 6, characterized in that In step (2), LiY includes at least one of LiCN, LiNC, LiSH, LiOCN, LiNCO, LiSCN and LiNCS; and / or, in step (2), the concentration of the LiY solution is 0.0001 mol / L-1 mol / L; and / or, in step (2), the solvent in the LiY solution includes at least one of an alcohol solvent, an ester solvent, and an ether solvent; And / or, in step (2), the time of infiltration and stirring is 0.5 min to 120 min.

8. The method according to claim 6, characterized in that In step (1), compound Li is prepared 6-a PS 5-a X 1+a The steps include: (1-1) Li2S, LiCl, and P2S5 are mixed uniformly in an oxygen-free and water-free environment to obtain a mixed powder; (1-2) sintering the mixed powder at a temperature of 300°C to 550°C in an oxygen-free and water-free environment to obtain the compound Li 6-a PS 5-a X 1+a .

9. The method according to claim 8, characterized in that In step (1-1), according to compound Li 6-a PS 5-a X 1+a The stoichiometric ratios of the elements in the mixture are Li2S, LiCl and P2S5; And / or, in step (1-2), the sintering temperature is 1 hour to 24 hours.

10. A positive electrode sheet, characterized in that: The invention comprises the sulfide solid electrolyte according to any one of claims 1 to 5 or the sulfide solid electrolyte prepared by the method according to any one of claims 6 to 9.

11. A solid-state battery, characterized in that: The invention comprises the sulfide solid electrolyte according to any one of claims 1 to 5 or the sulfide solid electrolyte prepared by the method according to any one of claims 6 to 9.

12. An electrical device, characterized in that: Including the solid-state battery according to claim 11.

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