Sulfide solid electrolyte and preparation method and application thereof

Abstract

The invention provides a sulfide solid electrolyte as well as a preparation method and application thereof. The molecular formula of the sulfide solid electrolyte is Li P < 1-b > M S < c > O < d > X < e >, wherein: 5lt; a < lt >; 10; 0 lt; blt; 1, 3lt; clt; ct; 6, 0lt; dlt; 2.5, 4lt; c + dlt; 6, 0lt; lt, lt; 2; m is selected from one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb, Ca, Mg, Sr, Ba, Zn, Cr, Sn or Pb, X is selected from one or more of Cl, Br or I. In an X-ray diffraction pattern of the sulfide solid electrolyte powder obtained by using CuK alpha rays, diffraction peaks do not appear in the ranges of 27-27.3 degrees, 29-29.5 degrees and 35-35.2 degrees. According to the sulfide solid electrolyte as well as the preparation method and the application thereof provided by the invention, the sulfide-doped solid electrolyte with a high-purity phase can be obtained, the generation of an impure phase is inhibited, and the energy efficiency and the cycle performance of a lithium ion battery are improved.

Description

Technical Field

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

[0002] In recent years, with the rapid development of electric vehicles and large-scale energy storage systems, the demand for high-energy-density, high-safety all-solid-state lithium batteries has become increasingly urgent. Sulfide solid electrolytes are considered to be one of the most promising candidate materials for building all-solid-state lithium batteries due to their advantages such as high ionic conductivity, wide electrochemical window and good mechanical processing properties. The synthesis methods of sulfide solid electrolytes mainly include solid-phase sintering, mechanical ball milling or liquid phase methods. Among them, solid-phase sintering and mechanical ball milling are currently the most widely used preparation methods due to their relatively simple processes.

[0003] However, in the actual preparation process, it is difficult to completely avoid Li 2 The formation of impurities such as S, LiCl and P seriously reduces the ionic conductivity of sulfide solid electrolytes and affects their electrochemical stability. Although excessive sulfur treatment can reduce sulfur loss, it may lead to the formation of new impurities and increase safety hazards, making it difficult to balance performance and cost. Doping can improve the ionic conductivity of sulfide solid electrolytes, but the selection of doping elements and the optimization of doping amounts lack systematic theoretical guidance, and the mechanism of doping's influence on phase purity and electrochemical performance is not yet fully understood. Summary of the invention

[0004] The present invention proposes a sulfide solid electrolyte and a preparation method and application thereof. Through the sulfide solid electrolyte and the preparation method and application thereof provided by the present invention, a high-purity doped sulfide solid electrolyte can be obtained, which can reduce the irreversible lithium ion consumption and coulomb efficiency reduction caused by impurities, reduce these side reactions, improve coulomb efficiency, and thus improve the energy efficiency and cycle performance of lithium-ion batteries.

[0005] In order to solve the above technical problems, the present invention proposes a sulfide solid electrolyte, the molecular formula of which is Li a P 1-b M b S c O d X e; wherein: 5 < a < 10; 0 < b < 1, 3 < c < 6, 0 < d < 2.5, 4 < c + d < 6, 0 < e < 2; M is selected from one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb, Ca, Mg, Sr, Ba, Zn, Cr, Sn or Pb, and X is selected from one or more of Cl, Br or I. In the X-ray diffraction pattern obtained by using CuKα rays of the sulfide solid electrolyte powder, no diffraction peaks appear in the ranges of 27° to 27.3°, 29° to 29.5°, and 35° to 35.2°.

[0006] In one embodiment of the present invention, M is selected from one or more of Sb, In, Bi or Mg, and X is selected from Cl.

[0007] In one embodiment of the present invention, the value range of b is 0 < b ≤ 0.1.

[0008] In one embodiment of the present invention, the purity of the sulfide solid electrolyte is greater than 99%.

[0009] The present invention also provides a preparation method of the above-mentioned sulfide solid electrolyte, including the steps:

[0010] According to the chemical formula of the sulfide solid electrolyte, the Li source, P source, M source, S source and X source are mixed stoichiometrically and then subjected to grinding treatment to obtain a sulfide solid electrolyte precursor powder; and

[0011] The sulfide solid electrolyte precursor powder is subjected to calcination treatment to obtain the sulfide solid electrolyte.

[0012] In one embodiment of the present invention, the Li source is selected from one or more of LiCl, LiBr, LiI or Li 2 S; the P source is selected from one or more of elemental P, P 2 S 5 、P 4 S 6 、PCl 5 或PBr 5 ; the M source is selected from one or more of an oxide of M or a sulfide of M; the S source is selected from one or more of elemental S, Li 2 S、P 2 S 5 、P 4 S 6 或a sulfide of M, and the sulfide of M includes As 2 S 5 、As 2 S 3 、Sb 2 S 5 、Sb2 S 3 、Bi 2 S 5 、Bi 2 S 3 、Al 2 S 3 , Ga 2 S 3 、In 2 S 3 Sc 2 S 3 , MgS, CaS, SrS, BaS, ZnS, CrS, SnS or PbS; the X source is selected from LiCl, PCl 5 、LiBr、PBr 5 , LiI or I 2 One or more of; the O element in the chemical formula comes from the oxide of M.

[0013] In one embodiment of the present invention, the grinding time is 1 hour to 48 hours, the grinding speed is 50 rpm / min to 1500 rpm / min, and the ball-to-material ratio is 1:1 to 100:1.

[0014] In one embodiment of the present invention, the temperature of the calcination treatment is 400° C. to 600° C., and the time of the calcination treatment is 1 h to 24 h.

[0015] The present invention also provides an all-solid-state lithium-ion battery, comprising at least:

[0016] Positive electrode;

[0017] A negative electrode; and

[0018] A solid electrolyte membrane, wherein the solid electrolyte membrane is disposed between the adjacent positive electrode sheet and the negative electrode sheet, and the solid electrolyte membrane comprises the above-mentioned sulfide solid electrolyte.

[0019] The present invention also provides an electronic device, comprising the all-solid-state lithium-ion battery described above.

[0020] In summary, the present invention proposes a sulfide solid electrolyte and its preparation method and application. By controlling the type of raw materials for synthesizing the sulfide solid electrolyte, it is possible to promote the nucleation of the sulfide solid electrolyte and control the direction and rate of grain growth, so that the grain size is more uniform and the crystallinity is higher, the impurity phase at the grain boundary is reduced, and the phase purity is improved. At the same time, the selection of synthetic raw materials can change the thermodynamic and kinetic conditions of the reaction, perform thermodynamic and kinetic regulation, reduce the Gibbs free energy of impurity phase formation, make the reaction more inclined to form a crystalline phase of the sulfide solid electrolyte, increase the generation rate of the target product, and inhibit the formation of impurity phases. By introducing specific doping elements and optimizing the doping amount, Li 2 The generation of impurity phases such as S, LiCl and P can obtain high-purity sulfide solid electrolytes and enhance the air stability and chemical stability of sulfide solid electrolytes. The ability to obtain high-purity doped sulfide solid electrolytes can reduce irreversible lithium ion consumption and coulomb efficiency reduction caused by impurities, reduce these side reactions, and improve coulomb efficiency, thereby improving the energy efficiency and cycle performance of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0022] Figure 1 This is the X-ray diffraction pattern of the sulfide solid electrolyte in Example 3.

[0023] Figure 2 This is the X-ray diffraction pattern of the sulfide solid electrolyte in Example 11.

[0024] Figure 3 This is the X-ray diffraction pattern of the sulfide solid electrolyte in Example 12.

[0025] Figure 4 This is the X-ray diffraction pattern of the sulfide solid electrolyte in Example 13.

[0026] Figure 5 This is the X-ray diffraction pattern of the sulfide solid electrolyte in Comparative Example 1.

[0027] Figure 6 This is the X-ray diffraction pattern of the sulfide solid electrolyte in Comparative Example 4. DETAILED DESCRIPTION

[0028] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0029] It should be understood that the present invention can be implemented in different forms and should not be construed as limited to the embodiments presented herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art.

[0030] The technical solutions of the present invention will be further described in detail below in conjunction with several embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0031] The present invention provides a sulfide solid electrolyte, and the molecular formula of the sulfide solid electrolyte is Li a P 1- b M b S c O d X e , where: 5 < a < 10; 0 < b < 1, 3 < c < 6, 0 < d < 2.5, 4 < c + d < 6, 0 < e < 2; M is selected from one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb, Ca, Mg, Sr, Ba, Zn, Cr, Sn, or Pb, etc., and X is selected from one or more of Cl, Br, or I, etc. Among them, the purity of the sulfide solid electrolyte is, for example, greater than 99%. In the X-ray diffraction pattern (X-Ray Diffraction, XRD) obtained by using CuKα rays for the sulfide solid electrolyte powder, no diffraction peaks appear in the ranges of 27° to 27.3°, 29° to 29.5°, and 35° to 35.2°. That is, no diffraction peak of Li 2 S appears in the range of 27° to 27.3°, no diffraction peak of P appears in the range of 29° to 29.5°, and no diffraction peak of LiCl appears in the range of 35° to 35.2°. That is, the present application can obtain a high-purity phase doped sulfide solid electrolyte, can reduce the irreversible lithium-ion consumption and the reduction of Coulomb efficiency caused by impurities, can reduce these side reactions, improve the Coulomb efficiency, and thus improve the energy efficiency and cycle performance of the lithium-ion battery, etc.

[0032] In an embodiment of the present invention, M is, for example, selected from one or more of Sb, In, Bi, Mg, etc. The ionic radii of these elements are close to those of the main elements in the sulfide solid electrolyte, such as sulfur and phosphorus. Therefore, during doping, they can more easily replace the positions of the main elements without causing excessive lattice distortion. And elements such as Sb, In, Bi, or Mg can form stable chemical bonds with the sulfur element in the sulfide, are difficult to be damaged by external influences, effectively improve the air stability of the sulfide solid electrolyte, enhance the air stability and chemical stability of the sulfide solid electrolyte, improve the cycle stability and performance of the battery, and improve the practicability and reliability of the sulfide solid electrolyte.

[0033] In an embodiment of the present invention, X is selected as a halogen element, and according to the different halogens, the degree of anion disorder between the 4a and 4c sites in the crystal structure of the sulfide solid electrolyte is different, from a small number of anti-site defects with X being I to 60% site disorder with X being Cl, and the lithium ionic conductivity of these compounds mainly depends on the degree of disorder of the anion and cation site occupancy. Therefore, X is, for example, also selected as Cl to improve the ionic conductivity and electrochemical stability of the sulfide solid electrolyte and improve the voltage stability. The value range of b is 0 < b ≤ 0.1. When the doping amount is too low, an effective dielectric layer may not be formed between the electrolyte and the lithium metal anode. Excessive doping will cause excessive lattice distortion and damage the original crystal structure, which may lead to a decrease in the structural stability of the material and even phase separation or amorphization, thereby reducing the ionic conductivity of the material. In a specific embodiment of the present invention, when M is a +5 valence element, b is preferably 0.04, when M is a +3 valence element, b is preferably 0.02, and when M is a +2 valence element, b is preferably 0.02 to improve the cycle performance of the lithium-ion battery.

[0034] The present invention also proposes a method for preparing a sulfide solid electrolyte, at least including: according to the chemical formula of the sulfide solid electrolyte, mixing a Li source, a P source, an M source, an S source, and an X source in stoichiometry, and then performing a grinding treatment to obtain a sulfide solid electrolyte precursor powder; calcining the sulfide solid electrolyte precursor powder to obtain the sulfide solid electrolyte.

[0035] In an embodiment of the present invention, according to the chemical formula Li a P 1-b M b S c O d X e of the sulfide solid electrolyte, mixing the Li source, the P source, the M source, the S source, and the X source evenly in stoichiometry, wherein the Li source is, for example, selected from one or more of LiCl, LiBr, LiI, or Li 2 S, etc., and the P source is selected from elemental P, P2 S 5 , P 4 S 6 、PCl 5 or PBr 5 The source of M is selected from one or more of the oxides of M or the sulfides of M, and the source of S is selected from the elemental S, Li 2 S.P. 2 S 5 , P 4 S 6 or one or more of the sulfides of M, wherein the sulfides of M include As 2 S 5 、As 2 S 3 , Sb 2 S 5 , Sb 2 S 3 、Bi 2 S 5 、Bi 2 S 3 、Al 2 S 3 , Ga 2 S 3 、In 2 S 3 Sc 2 S 3 , MgS, CaS, SrS, BaS, ZnS, CrS, SnS or PbS, etc., and the X source is selected from LiCl, PCl 5 、LiBr、PBr 5 , LiI or I 2 One or more of the above, the O element in the chemical formula comes from the oxide of M. After the raw materials are mixed evenly, they are ground by ball milling, for example, and the raw materials are placed in a ball milling jar and ball milled in an inert gas atmosphere, wherein the ball-to-material ratio is, for example, 1:1 to 100:1, the grinding speed is, for example, 50 rpm / min to 1500 rpm / min, and the grinding time is, for example, 1 h to 48 h, to obtain a sulfide solid electrolyte precursor powder. Since the doped substance is an oxide of M or a sulfide of M, its surface energy is relatively high, which will attract the surrounding Li + , P 5+ and S 2- Plasma promotes the nucleation of sulfide solid electrolyte and controls the direction and rate of grain growth, making the grain size more uniform and the crystallinity higher, reducing the impurity phase at the grain boundary and improving the phase purity.

[0036] In one embodiment of the present invention, the sulfide solid electrolyte precursor powder is calcined, wherein the calcination temperature is, for example, 400°C to 600°C, and the calcination time is, for example, 1h to 24h, to obtain a sulfide solid electrolyte. The doping of the oxide of M or the sulfide of M changes the thermodynamic and kinetic conditions of the reaction, and thermodynamic and kinetic regulation is performed. From a thermodynamic point of view, the Gibbs free energy of impurity phase formation is reduced, making the reaction more inclined to form a crystalline phase of the sulfide solid electrolyte; from a kinetic point of view, the generation rate of the target product is increased, and the formation of the impurity phase is suppressed, thereby improving the purity of the obtained sulfide solid phase.

[0037] The present invention also proposes an all-solid-state lithium-ion battery, comprising a positive electrode sheet, a negative electrode sheet and a solid electrolyte membrane, wherein the solid electrolyte membrane is arranged between adjacent positive electrode sheets and negative electrode sheets. Among them, the solid electrolyte membrane comprises the above-mentioned sulfide solid electrolyte to improve the cycle performance of the all-solid-state lithium-ion battery. In one embodiment of the present invention, the solid electrolyte membrane is obtained by, for example, cold pressing the above-mentioned sulfide solid electrolyte at a pressure of 300MPa to 400MPa, and the thickness of the solid electrolyte membrane is, for example, 100μm to 500μm. In the present invention, the all-solid-state lithium-ion battery is, for example, a primary battery or a secondary battery, and the secondary battery is, for example, a soft-pack battery, a hard-shell battery or a cylindrical battery, etc. The present invention does not specifically limit the types and types of the all-solid-state lithium-ion battery.

[0038] In one embodiment of the present invention, the positive electrode sheet includes, for example, a positive electrode current collector and a positive electrode active layer disposed on at least one side of the positive electrode current collector. The positive electrode current collector is, for example, a foil formed by surface treatment of nickel, titanium, aluminum, silver, stainless steel or carbon. In addition to the foil, the positive electrode current collector can also be used in any one or more combinations of various forms such as film, mesh, porous, foam or non-woven fabric, and the thickness of the positive electrode current collector is, for example, 8 μm to 15 μm.

[0039] In one embodiment of the present invention, the positive electrode active layer includes, for example, a positive electrode active material, a positive electrode electrolyte, a positive electrode conductor, and a positive electrode binder, wherein the positive electrode active material is, for example, selected from at least one of lithium nickel cobalt manganese oxide (NCM), lithium nickel oxide (LNO), lithium manganese oxide (LMO), lithium nickel manganese oxide (LNMO), lithium cobalt oxide (LCO), or lithium nickel cobalt aluminum oxide (NCA), etc., the positive electrode electrolyte is, for example, a halide solid electrolyte, the positive electrode conductor is, for example, selected from at least one of graphite, graphene, conductive carbon black (Super P), nanocarbon fiber (Vapor-grown Carbon Fiber, VGCF) or carbon nanotubes, etc., and the positive electrode binder is, for example, selected from polyvinylidene fluoride (Polyvinylidene Fluoride, PVDF), carboxymethyl cellulose (Carboxymethyl Cellulose, CMC), styrene butadiene rubber (Polymerized Styrene Butadiene Rubber, SBR), polyvinyl pyrrolidone (Polyvinyl Pyrrolidone, PVP), polymethyl methacrylate (Polymethyl methacrylate, PVP), etc. Methacrylate, PMMA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyurethane (PU), polyvinyl alcohol (PVA), sodium alginate (Alg), ethylene-propylene-diene monomer (EPDM), styrene-butadiene rubber, fluorine rubber (Fluororubber), β-cyclodextrin polymer (β-CDp), polypropylene emulsion (LA132), polytetrafluoroethylene (PTFE), ethylene-tetrafluoroethylene copolymer (ETFE), fluorinated ethylene-propylene copolymer (FEP), perfluoroalkoxy resin (PFA), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (Ethylene-chlorotrifluoroethylene copolymer, ECTFE), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP) or polyvinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE).

[0040] In one embodiment of the present invention, the positive electrode current collector is, for example, aluminum foil, and the positive electrode active material is, for example, LiNi 0.8 Co 0.1 Mn 0.1 O 2 , the positive electrode electrolyte is, for example, Li 2.35 Zr 0.65 Fe 0.35 Cl 5 Br 0.5 I 0.5 , the positive electrode conductive agent includes, for example, Super P and VGCF, and the mass ratio of Super P and VGCF is, for example, 1:1, and the positive electrode binder is, for example, PTFE. After the positive electrode active material, the positive electrode electrolyte, the positive electrode conductive agent and the positive electrode binder are uniformly mixed in a mass ratio of, for example, 69:29:1:1, they are compounded with aluminum foil by dry pressing to obtain a positive electrode sheet. The present invention does not limit the mass ratio of the positive electrode active material, the positive electrode electrolyte, the positive electrode conductive agent and the positive electrode binder, which can be selected according to actual needs, and the positive electrode current collector can be not provided as needed.

[0041] In one embodiment of the present invention, the negative electrode plate is selected from at least one of a metal lithium plate, a metal indium plate or a lithium indium alloy plate. In another embodiment of the present invention, the negative electrode plate includes, for example, a negative electrode current collector and a negative electrode active layer coated on the surface of at least one side of the negative electrode current collector. The negative electrode current collector is, for example, a copper foil current collector, a composite copper foil current collector, a carbon current collector, a foam copper current collector or a stainless steel current collector, and the thickness of the negative electrode current collector is, for example, 8 μm to 15 μm.

[0042] In one embodiment of the present invention, the negative electrode active layer includes, for example, a negative electrode active material, a negative electrode electrolyte, a negative electrode conductive agent and a negative electrode binder, etc. The negative electrode active material is selected from at least one of a graphite material, a silicon material or a composite material of a graphite material and a silicon material, etc. The silicon material is, for example, at least one of a silicon oxide material or a silicon carbon material, etc. The negative electrode electrolyte is, for example, the above-mentioned sulfide solid electrolyte, the negative electrode conductive agent is selected from at least one of graphite, graphene, Super P, VGCF or carbon nanotubes, etc., and the negative electrode binder is selected from at least one of PVDF, CMC, SBR, PVP, PMMA, PAN, PAA, PU, ​​PVA, Alg, EPDM, styrene-butadiene rubber, fluororubber, β-CDp, LA132, PTFE, ETFE, FEP, PFA, PCTFE, ECTFE, PVDF-HFP or PVDF-CTFE, etc.

[0043] In one embodiment of the present invention, the negative electrode current collector is, for example, copper foil, the negative electrode active material is, for example, a mixture of silicon oxide material and graphite, and the ratio of silicon oxide material to graphite is, for example, 5:95, the negative electrode electrolyte is, for example, the above-mentioned sulfide solid electrolyte, the negative electrode conductive agent includes, for example, Super P and VGCF, and the mass ratio of Super P to VGCF is, for example, 1:1, and the negative electrode binder is, for example, SBR. After the negative electrode active material, the negative electrode electrolyte, the negative electrode conductive agent and the negative electrode binder are uniformly mixed in a mass ratio of, for example, 72:22:3:3, they are compounded with copper foil by dry pressing to obtain a negative electrode sheet. The present invention does not limit the mass ratio of the negative electrode active material, the negative electrode electrolyte, the negative electrode conductive agent and the negative electrode binder, which can be selected according to actual needs, and the negative electrode current collector may not be provided as needed.

[0044] In one embodiment of the present invention, the above-mentioned positive electrode sheet, solid electrolyte membrane sheet and negative electrode sheet are placed in sequence, pressed and sealed to obtain an all-solid-state lithium-ion battery. The assembly process of the all-solid-state battery is completed in an inert atmosphere glove box.

[0045] Hereinafter, the present invention will be explained in more detail by citing examples, which should not be construed as limiting. Appropriate modifications may be made within the scope consistent with the gist of the present invention, all of which fall within the technical scope of the present invention.

[0046] Example 1

[0047] Preparation of sulfide solid electrolyte: Under argon atmosphere, 2.015 mol of Li 2 S, 1.5 mol LiCl, 0.495 mol P 2 S 5 and 0.01 mol of MgO were placed in a tungsten steel ball mill, and tungsten steel balls were added at a ball-to-material ratio of 40:1. The ball mill was ground at a speed of 100 rpm / min for 10 minutes, and then ground at 800 rpm / min for 16 hours to obtain a uniformly mixed sulfide solid electrolyte precursor powder. The sulfide solid electrolyte precursor powder was placed in a crucible and calcined at 500°C for 10 hours. After cooling, Li 5.53 P 0.99 Mg 0.01 S 4.49 O 0.01 Cl 1.5 .

[0048] Preparation of solid electrolyte membrane: 50 mg of Li 5.5 P 0.99 Sb 0.01 S 4.475 O 0.025 Cl 1.5The solid electrolyte membrane was prepared by cold pressing at 360 MPa, and the solid electrolyte membrane had a thickness of 400 μm and a diameter of 10 mm.

[0049] Preparation of positive electrode: LiNi 0.8 Co 0.1 Mn 0.1 O 2 , conductive agent, Li 2.35 Zr 0.65 Fe 0.35 Cl 5 Br 0.5 I 0.5 The PTFE is mixed in a mass ratio of 69:1:29:1, and after being uniformly mixed, it is compounded with aluminum foil by dry pressing and cut into discs with a diameter of 10 mm to obtain a positive electrode sheet. The positive electrode conductive agent includes Super P and VGCF, and the mass ratio of Super P to VGCF is 1:1.

[0050] Negative electrode sheet: Select a single lithium sheet and cut it into a disc with a diameter of 10 mm to obtain a negative electrode sheet.

[0051] Assembly of all-solid-state batteries: The positive electrode sheets, solid electrolyte membrane sheets and negative electrode sheets prepared above are stacked in sequence, pressed and sealed, and assembled into all-solid-state lithium-ion batteries.

[0052] Example 2

[0053] By 2.0225 mol Li 2 S, 1.5 mol LiCl, 0.4925 mol P 2 S 5 The chemical formula of the sulfide solid electrolyte prepared by mixing 0.015 mol of MgO is Li 5.545 P 0.985 Mg 0.015 S 4.485 O 0.015 Cl 1.5 , other operations remain the same as those in Example 1.

[0054] Example 3

[0055] By 2.03 mol of Li 2 S, 1.5 mol LiCl, 0.49 mol P 2 S 5 The chemical formula of the sulfide solid electrolyte prepared by mixing 0.02 mol of MgO is Li 5.56 P 0.98 Mg 0.02 S 4.48 O 0.02 Cl 1.5, other operations remain the same as those in Example 1.

[0056] Example 4

[0057] By 2.09 mol of Li 2 S, 1.5 mol LiCl, 0.47 mol P 2 S 5 The sulfide solid electrolyte prepared by 0.06 mol MgO is Li 5.68 P 0.94 Mg 0.06 S 4.44 O 0.06 Cl 1.5 , other operations remain the same as those in Example 1.

[0058] Example 5

[0059] By 2.15 mol Li 2 S, 1.5 mol LiCl, 0.45 mol P 2 S 5 The chemical formula of the sulfide solid electrolyte prepared by mixing 0.1 mol of MgO is Li 5.8 P 0.9 Mg 0.1 S 4.4 O 0.1 Cl 1.5 , other operations remain the same as those in Example 1.

[0060] Example 6

[0061] By 1.83 mol Li 2 S, 1.9 mol LiCl, 0.49 mol P 2 S 5 The chemical formula of the sulfide solid electrolyte prepared by mixing 0.02 mol of MgO is Li 5.16 P 0.98 Mg 0.02 S 4.08 O 0.02 Cl 1.9 , other operations remain the same as those in Example 1.

[0062] Example 7

[0063] By 2.53 mol of Li 2 S, 1 mol of LiCl, 0.49 mol of P 2 S 5 The chemical formula of the sulfide solid electrolyte prepared by mixing 0.02 mol of MgO is Li 6.06 P 0.98 Mg 0.02 S4.98 O 0.02 C1, other operations are consistent with those in Example 1.

[0064] Example 8

[0065] By 3.43 mol of Li 2 S, 0.1 mol LiCl, 0.49 mol P 2 S 5 The chemical formula of the sulfide solid electrolyte prepared by mixing 0.02 mol of MgO is Li 6.96 P 0.98 Mg 0.02 S 5.88 O 0.02 Cl 0.1 , other operations remain the same as those in Example 1.

[0066] Example 9

[0067] By 2.03 mol of Li 2 S, 1.4 mol LiCl, 0.1 mol LiBr, 0.49 mol P 2 S 5 The chemical formula of the sulfide solid electrolyte prepared by mixing 0.02 mol of MgO is Li 5.56 P 0.98 Mg 0.02 S 4.48 O 0.02 Cl 1.4 Br 0.1 , other operations remain the same as those in Example 1.

[0068] Example 10

[0069] By 2.03 mol of Li 2 S, 1.3 mol LiCl, 0.1 mol LiBr, 0.1 mol LiI, 0.49 mol P 2 S 5 The chemical formula of the sulfide solid electrolyte prepared by mixing 0.02 mol of MgO is Li 5.56 P 0.98 Mg 0.02 S 4.48 O 0.02 Cl 1.3 Br 0.1 I 0 .1 , other operations remain the same as those in Example 1.

[0070] Embodiment 11

[0071] By 2.02 mol of Li 2S, 1.5 mol LiCl, 0.49 mol P 2 S 5 and 0.01 mol In 2 O 3 The chemical formula of the core of the prepared sulfide solid electrolyte is Li 5.54 P 0.98 In 0.02 S 4.47 O 0.03 Cl 1.5 , other operations remain the same as those in Example 1.

[0072] Example 12

[0073] By 2.02 mol of Li 2 S, 1.5 mol LiCl, 0.49 mol P 2 S 5 and 0.01 mol Bi 2 O 3 The chemical formula of the core of the prepared sulfide solid electrolyte is Li 5.54 P 0.98 Bi 0.02 S 4.47 O 0.03 Cl 1.5 , other operations remain the same as those in Example 1.

[0074] Embodiment 13

[0075] By 2 mol Li 2 S, 1.5 mol LiCl, 0.48 mol P 2 S 5 and 0.02 mol of Sb 2 O 5 The chemical formula of the core of the prepared sulfide solid electrolyte is Li 5.5 P 0.96 Sb 0.04 S 4.40 O 0.10 Cl 1.5 , other operations remain the same as those in Example 1.

[0076] Embodiment 14

[0077] By 2.03 mol of Li 2 S, 1.5 mol LiCl, 0.49 mol P 2 S 5 The chemical formula of the sulfide solid electrolyte core made by mixing 0.02 mol of CaO is Li 5.56 P 0.98 Ca 0.02 S4.48 O 0.02 Cl 1.5 , other operations remain the same as those in Example 1.

[0078] Embodiment 15

[0079] By 2.03 mol of Li 2 S, 1.5 mol LiCl, 0.49 mol P 2 S 5 The chemical formula of the sulfide solid electrolyte core made of 0.02 mol ZnO is Li 5.56 P 0.98 Zn 0.02 S 4.48 O 0.02 Cl 1.5 , other operations remain the same as those in Example 1.

[0080] Comparative Example 1

[0081] By 2 mol Li 2 S, 1.5 mol LiCl and 0.5 mol P 2 S 5 The chemical formula of the prepared sulfide solid electrolyte is Li 5.5 PS 4.5 Cl 1.5 , other operations remain the same as those in Example 1.

[0082] Comparative Example 2

[0083] By 2 mol Li 2 S, 1.4 mol LiCl, 0.1 mol LiBr and 0.5 mol P 2 S 5 The chemical formula of the prepared sulfide solid electrolyte is Li 5.5 PS 4.5 Cl 1.4 Br 0.1 , other operations remain the same as those in Example 1.

[0084] Comparative Example 3

[0085] By 2 mol Li 2 S, 1.3 mol LiCl, 0.1 mol LiBr, 0.1 mol LiI and 0.5 mol P 2 S 5 The chemical formula of the prepared electrolyte is Li 5.5 PS 4.5 Cl 1.3 Br 0.1 I 0.1 , other operations remain the same as those in Example 1.

[0086] Comparative Example 4

[0087] By 2.21 mol of Li 2 S, 1.5 mol LiCl, 0.43 mol P 2 S 5 The chemical formula of the sulfide solid electrolyte prepared by mixing 0.14 mol of MgO is Li 5.92 P 0.86 Mg 0.14 S 4.36 O 0.14 Cl 1.5 , other operations remain the same as those in Example 1.

[0088] In one embodiment of the present invention, the XRD test is to grind and sieve the sulfide solid electrolyte powder material to make a powder material suitable for XRD testing, for example, through a 60-200 mesh sieve, and place the sieved powder on a standard sample table to fill and flatten it, and set the XRD detection angle range to 10° to 80°. According to different models of X-ray diffractometers, the corresponding X-ray scanning speed can be set, generally less than 15° / min, to obtain an XRD spectrum.

[0089] In one embodiment of the present invention, the purity test is to add the sulfide solid electrolyte into a sealed high-pressure acid for digestion, the acid is, for example, nitric acid (HNO 3 ) and hydrochloric acid (HCl), and HNO 3 The volume ratio of HCl is, for example, 3:1, and a small amount of hydrofluoric acid (HF) is added to assist in dissolving sulfides, and the content of hydrofluoric acid is, for example, 0.1% v / v. The mixed solution is placed in a microwave digestion apparatus, digested at 200°C for 30 minutes, and then quickly transferred to a polytetrafluoroethylene container. The total molar amount of Li, P, M, S and X elements is determined by inductively coupled plasma mass spectrometry (ICP-MS), which is recorded as n Li 、n P 、n M 、n S and n X ; Assuming that the impurity Li in the sulfide solid electrolyte 2 S is ymol, LiCl is zmol, P is wmol, and the main phase Li a P 1-b M b S c O d X e Set up the system of equations for xmol:

[0090]

[0091] Solve the system of equations to get the values ​​of x, y, z, and w;

[0092] Substitute into the formula:

[0093]

[0094] The phase purity of the sulfide solid electrolyte is obtained, where M is the relative molecular mass of the substance.

[0095] In Examples 1-15 and Comparative Examples 1-4 of the present invention, different sulfide solid electrolytes are used to obtain lithium-ion batteries. The lithium-ion batteries prepared above are subjected to long-cycle charge and discharge at 25°C, and their discharge capacity is measured, and the energy density is calculated. The working voltage range of the battery test is 2.5V to 4.3V, the charge and discharge rate is 1C / 1C, and the discharge capacity of the first cycle is recorded as the 1C discharge capacity. When the battery capacity reaches 80% of the first cycle capacity (80% State of Health, 80% SOH), the test is terminated to obtain the number of cycles at room temperature. The symmetrical battery is charged at 1 mA / cm 2 The constant current charge-discharge cycle test was carried out at a current density of , and the test results are shown in Table 1.

[0096] Table 1. Performance of sulfide solid electrolytes and lithium-ion batteries in Examples 1-15 and Comparative Examples 1-4

[0097]

[0098] See also Figures 1 to 5 As shown, by comparing Examples 3, 11-13 and Comparative Examples 1 and 4, it can be seen that by doping with different M elements and controlling the doping amount of the M element, the sulfide solid electrolyte obtained in the present application has strong diffraction peaks at 2θ of 17.5±0.3°, 25.5±0.3°, 30.5±0.3° and 32±0.3°, which are the diffraction peaks of the (111), (220), (311) and (222) crystal planes, respectively. This shows that when different M elements are doped and at the optimal content of the M element, the sulfide solid electrolyte has a better crystalline structure and thus has a higher ionic conductivity, indicating that the doping of the M element will not destroy the crystalline structure of the sulfide solid electrolyte. Figure 5 As shown, Comparative Example 1 did not carry out any doping of Li 5.5 PS 4.5 Cl 1.5 In the XRD spectrum, Li 2 The diffraction peak of S appears at 29.1°, the diffraction peak of P appears at 35.1°, and the diffraction peak of LiCl appears at 35.1°. Figure 1-4 As shown, after doping Li 5.56 P0.98 Mg 0.02 S 4.48 O 0.02 Cl 1.5 , Li 5.54 P 0.98 In 0.02 S 4.47 O 0.03 Cl 1.5 , Li 5.54 P 0.98 Bi 0.02 S 4.4 7 O 0.03 Cl 1.5 and Li 5.5 P 0.96 Sb 0.04 S 4.40 O 0.10 Cl 1.5 In the XRD spectrum of , under the condition of different M element doping, no diffraction peaks appear in the range of 2θ 27°~27.3°, 29°~29.5° and 35°~35.2°, indicating that by introducing specific doping elements and optimizing the doping amount, Li 2 The formation of impurity phases such as S, LiCl and P can obtain high-purity sulfide solid electrolyte. Figure 6 As shown, after doping Li 5.92 P 0.86 Mg 0.14 S 4.36 O 0.14 Cl 1.5 In the XRD diagram, when the M element is doped excessively in the spectrum, b>0.1, the diffraction peak of MgO appears at the position of 43.3° at 2θ, indicating that the introduction of excessive specific doping elements will also lead to the formation of new impurity phases.

[0099] As shown in Table 1, by comparing Examples 1-15 and 1-3, it can be seen that when the sulfide solid electrolyte is not doped with M element and O element, the sulfide solid electrolyte has at least Li 2 The diffraction peak of an impurity in S, P or LiCl, the purity of the sulfide solid electrolyte is low. When doped with M and O elements, no diffraction peak appears in the XRD spectrum within the range of 2θ of 27° to 27.3°, 29° to 29.5° and 35° to 35.2°, and the purity of the sulfide solid electrolyte is greater than 99%, indicating that doping can inhibit the generation of impurities, thereby reducing irreversible lithium ion consumption and reducing side reactions such as coulomb efficiency, thereby improving the coulomb efficiency of lithium-ion batteries, thereby improving the energy efficiency and cycle performance of lithium-ion batteries.

[0100] Please refer to Table 1. It can be seen from the comparison of Examples 1-5 and Comparative Example 4 that when the M element in the sulfide solid electrolyte is Mg, as the Mg doping amount increases, the purity of the sulfide solid electrolyte first increases and then decreases, and the cycle performance of the lithium-ion battery gradually increases and then gradually decreases. This is because when the Mg doping amount is low, the main diffraction peaks of these samples are well aligned with the pure argyrodite structure (Li 7 PS 6 , refer to the XRD standard card PDF#0868), there is no obvious impurity phase in the spectrum, which indicates the successful manufacture of the target Mg-O co-doped electrolyte. However, with the further increase of doping concentration, the diffraction peak of MgO impurity phase will appear in the XRD diagram, which will lead to the decrease of purity and electrochemical performance of sulfide solid electrolyte. Therefore, controlling the doping amount of M element can inhibit the generation of impurity phase, while improving the purity of sulfide solid electrolyte and electrochemical performance of lithium-ion battery.

[0101] As shown in Table 1, by comparing Examples 3, 6-8, it can be seen that when the Mg doping amount in the sulfide solid electrolyte is the same, increasing or decreasing the Cl element content does not change the purity much, but will reduce the cycle performance of the lithium-ion battery. Therefore, controlling the doping amount of M can control the purity of the sulfide solid electrolyte and the content of the Cl element to ensure the performance of the lithium-ion battery of the sulfide solid electrolyte.

[0102] Please refer to Table 1. Comparative Examples 3, 9-10 show that when the doping amount of Mg element in the sulfide solid electrolyte is the same, the addition of one or more of Br or I elements will reduce the cycle performance of the battery, and the purity does not change much. Therefore, X selects Cl element to improve the electrical properties of lithium-ion batteries. Comparative Examples 3, 11-15 show that when M doping element selects other elements, controlling the doping amount of M can also suppress the generation of impurity phases and improve the purity of sulfide solid electrolytes, but when M element selects Sb, In, Bi or Mg, the cycle performance of lithium-ion batteries is better. Therefore, controlling the doping type and doping amount of M element can regulate the nucleation and growth of sulfide solid electrolytes, regulate thermodynamics and kinetics during the growth process, increase the generation rate of target products, and suppress the formation of impurity phases, thereby improving phase purity and thus improving the performance of lithium-ion batteries.

[0103] The present invention also provides an electronic device, the electronic device includes at least one of the above-mentioned lithium-ion batteries, and the lithium-ion battery is used to provide electrical energy. Among them, the electronic device can be a vehicle, a mobile phone, a portable device, a laptop computer, a ship, a spacecraft, an electric toy and an electric tool, etc. In one embodiment of the present invention, the vehicle is, for example, a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc. Spacecraft include airplanes, rockets, space shuttles and spacecrafts, etc. Electric toys include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys and electric airplane toys, etc. Electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators and electric planers, etc. The electronic device includes the above-mentioned lithium-ion battery, so the advantages of the above-mentioned lithium-ion battery are included, which will not be elaborated here.

[0104] In summary, the present invention proposes a sulfide solid electrolyte and its preparation method and application. By controlling the type of raw materials for synthesizing the sulfide solid electrolyte, it is possible to promote the nucleation of the sulfide solid electrolyte and control the direction and rate of grain growth, so that the grain size is more uniform and the crystallinity is higher, the impurity phase at the grain boundary is reduced, and the phase purity is improved. At the same time, the selection of synthetic raw materials can change the thermodynamic and kinetic conditions of the reaction, perform thermodynamic and kinetic regulation, reduce the Gibbs free energy of impurity phase formation, make the reaction more inclined to form a crystalline phase of the sulfide solid electrolyte, increase the generation rate of the target product, and inhibit the formation of impurity phases. By introducing specific doping elements and optimizing the doping amount, Li 2 The generation of impurity phases such as S, LiCl and P can obtain high-purity sulfide solid electrolytes and enhance the air stability and chemical stability of sulfide solid electrolytes. The ability to obtain high-purity doped sulfide solid electrolytes can reduce irreversible lithium ion consumption and coulomb efficiency reduction caused by impurities, reduce these side reactions, and improve coulomb efficiency, thereby improving the energy efficiency and cycle performance of lithium-ion batteries.

[0105] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the inventive concept, such as a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

[0106] Except for the technical features described in the specification, the remaining technical features are known technologies to those skilled in the art. In order to highlight the innovative features of the present invention, the remaining technical features will not be described here in detail.

Claims

1. A sulfide solid electrolyte, characterized in that: The molecular formula of the sulfide solid electrolyte is Li a P 1- b M b S c O d X e ; wherein: 5 < a < 10; 0 < b < 1, 3 < c < 6, 0 < d < 2.5, 4 < c + d < 6, 0 < e < 2; M is selected from one or more of Al, Ga, In, Ti, Sc, As, Sb, Bi, V, Nb, Ca, Mg, Sr, Ba, Zn, Cr, Sn or Pb, X is selected from one or more of Cl, Br or I, and in the X-ray diffraction pattern obtained by using CuKα rays of the sulfide solid electrolyte powder, no diffraction peaks appear in the ranges of 27° to 27.3°, 29° to 29.5° and 35° to 35.2°.

2. The sulfide solid electrolyte according to claim 1, characterized in that M is selected from one or more of Sb, In, Bi and Mg, and X is selected from Cl.

3. The sulfide solid electrolyte according to claim 1, characterized in that The value range of b is 0<b≤0.

1.

4. The sulfide solid electrolyte according to claim 1, characterized in that The purity of the sulfide solid electrolyte is greater than 99%.

5. A method for preparing the sulfide solid electrolyte according to any one of claims 1 to 4, characterized in that: Includes steps: According to the chemical formula of the sulfide solid electrolyte, a Li source, a P source, an M source, a S source and an X source are mixed in stoichiometric amounts, and then ground to obtain a sulfide solid electrolyte precursor powder; and The sulfide solid electrolyte precursor powder is calcined to obtain the sulfide solid electrolyte.

6. The method for preparing a sulfide solid electrolyte according to claim 5, characterized in that: The Li source is selected from one or more of LiCl, LiBr, LiI or Li2S; the P source is selected from one or more of elemental P, P2S5, P4S6, PCl5 or PBr5; the M source is selected from one or more of M oxides or M sulfides; the S source is selected from one or more of elemental S, Li2S, P2S5, P4S6 or M sulfides, and the sulfides of M include one or more of As2S5, As2S3, Sb2S5, Sb2S3, Bi2S5, Bi2S3, Al2S3, Ga2S3, In2S3, Sc2S3, MgS, CaS, SrS, BaS, ZnS, CrS, SnS or PbS; the X source is selected from one or more of LiCl, PCl5, LiBr, PBr5, LiI or I2; the O element in the chemical formula comes from the oxide of M.

7. The method for preparing a sulfide solid electrolyte according to claim 5, characterized in that: The grinding time is 1h to 48h, the grinding speed is 50rpm / min to 1500rpm / min, and the ball-to-material ratio is 1:1 to 100:

1.

8. The method for preparing a sulfide solid electrolyte according to claim 5, characterized in that: The calcination temperature is 400° C. to 600° C., and the calcination time is 1 h to 24 h.

9. An all-solid-state lithium-ion battery, characterized in that: At least: Positive electrode; Negative electrode; as well as A solid electrolyte membrane, wherein the solid electrolyte membrane is disposed between the adjacent positive electrode sheet and the negative electrode sheet, and the solid electrolyte membrane comprises the sulfide solid electrolyte according to any one of claims 1 to 4.

10. An electronic device, characterized in that: Including the all-solid-state lithium-ion battery as described in claim 9.

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