Composite sulfide solid electrolyte, preparation method thereof and lithium ion battery

Abstract

The invention provides a composite sulfide solid electrolyte, a preparation method thereof and a lithium ion battery. The composite sulfide solid-state electrolyte comprises a sulfide solid-state electrolyte matrix and a composite layer coating the surface of the sulfide solid-state electrolyte matrix, the composite layer comprises an interface reaction layer and a coating layer from inside to outside, the coating layer comprises a halide material, and the interface reaction layer comprises an interface reactant obtained after the halide material and the surface of the sulfide solid electrolyte matrix are subjected to an interface reaction. According to the invention, under the action of the specific surface composite layer, the electrochemical window and mechanical property of the sulfide solid electrolyte are widened, the mechanical stability and electrochemical stability of the sulfide solid electrolyte and a positive electrode material are improved, and the interface reaction of the sulfide solid electrolyte is further inhibited.

Description

Technical Field

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

[0002] With the development of science and technology, secondary batteries, as typical energy storage devices, are widely used in many technical fields that require energy storage, ranging from portable electronic devices to electric vehicles and even smart grids. The basic structure of a traditional secondary battery includes a positive electrode, a negative electrode, and an electrolyte arranged between the positive and negative electrodes to conduct ions but isolate electrons. Traditional electrolytes are mostly organic liquid electrolytes, which are used with a diaphragm to prevent direct contact between the positive and negative electrodes. Organic liquid electrolytes have the risk of flatulence and leakage during use. In addition, for secondary batteries such as lithium ion or lithium metal, lithium dendrites generated during the charge and discharge process can easily pierce the diaphragm, causing the battery to short-circuit.

[0003] Compared with liquid electrolytes, solid electrolytes have the advantages of being non-volatile, non-flammable, non-corrosive, and having high mechanical strength. They avoid electrolyte leakage and electrode short circuit in traditional liquid lithium-ion batteries, and reduce the battery pack's sensitivity to temperature. Due to the high mechanical strength of solid electrolytes, they can effectively prevent the growth of lithium dendrites and have extremely high safety during use.

[0004] Currently, solid-state electrolytes mainly include oxides, sulfides, and polymer solid electrolytes. Oxide solid electrolytes are insensitive to the environment, have excellent water and oxygen resistance, and possess relatively stable physical and chemical properties, but they also have low electrical conductivity. Polymer solid electrolytes are formed by the complexation of polar polymers and metal salts. They have good film-forming properties, flexibility, and high safety performance, but they also have low electrical conductivity, a small lithium ion migration number, and poor mechanical properties. Sulfide solid electrolytes have ionic conductivity comparable to that of liquid electrolyte solutions, a lithium ion migration number close to 1, and good wettability between the electrolyte and electrode materials. They are suitable for high-energy-density energy storage devices and have become one of the most promising technical routes for the development of all-solid-state batteries.

[0005] However, sulfide solid electrolytes are particularly sensitive to water and oxygen, and have extremely stringent environmental requirements during their preparation and use, which severely limits their large-scale application. In addition, the electrochemical window of sulfide solid electrolytes does not match that of high-voltage positive electrode materials, often generating large impedance and multiple decomposition products at the interface, forming a space charge layer, and having poor electrochemical and mechanical stability with the positive electrode material. In addition, sulfide reacts when in contact with the metallic lithium negative electrode to generate substances with poor ion conductivity, which is not conducive to the migration of lithium ions. These problems faced by sulfide solid electrolytes greatly affect the performance of all-solid-state batteries.

[0006] Therefore, how to effectively inhibit the interfacial side reactions of sulfide solid electrolytes and improve their stability is a technical problem that needs to be solved urgently. Summary of the Invention

[0007] To address the shortcomings of the prior art, the present invention aims to provide a composite sulfide solid electrolyte, a preparation method thereof, and a lithium-ion battery. The present invention utilizes a specific surface composite layer to not only broaden the electrochemical window and mechanical properties of the sulfide solid electrolyte, enhancing its mechanical and electrochemical stability with the cathode material, but also further suppresses interfacial reactions with the sulfide solid electrolyte.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a composite sulfide solid electrolyte, comprising a sulfide solid electrolyte matrix and a composite layer coated on the surface of the sulfide solid electrolyte matrix;

[0010] The composite layer includes an interface reaction layer and a coating layer from the inside to the outside, the coating layer includes a halide material, and the interface reaction layer includes an interface reactant after the halide material undergoes an interface reaction with the surface of the sulfide solid electrolyte matrix.

[0011] The composite sulfide solid electrolyte provided by the present invention, in addition to the effects of the coating layer of the halide material and the sulfide solid electrolyte matrix, also has an interface reactant formed by the interface reaction between the halide material and the sulfide solid electrolyte at the interface contact between the two, forming a self-limiting modified layer. The interface reactant cooperates with the halide material in the coating layer and works together to not only suppress and achieve a widened electrochemical window and mechanical properties of the sulfide solid electrolyte, and improve its mechanical stability and electrochemical stability with the positive electrode material, but also suppresses the interface reaction of the sulfide matrix and further suppresses the problem of other decomposition products appearing when the matrix surface is only coated with the halide material; it also improves the lithium ion conductivity of the composite sulfide solid electrolyte; broadens its application in all-solid-state batteries, and provides an effective solution for the industrialization of all-solid-state batteries.

[0012] In the present invention, if the composite layer only contains the coating layer, that is, does not contain the interface reaction layer, the effect of changing the oxidation and reduction properties of the material cannot be achieved.

[0013] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0014] Preferably, the halide material includes metal halide and / or halide solid electrolyte.

[0015] The halide material provided by the present invention uses metal halides and / or halide solid electrolytes, which are more conducive to interfacial reactions with sulfide solid electrolytes; and further preferably uses halide solid electrolytes, which better utilize the high lithium ion conductivity characteristics of halide solid electrolytes, and can also achieve a certain interfacial reaction with sulfide solid electrolytes to generate a stable interface layer, so that the composite electrolyte can maintain a high lithium ion conductivity while improving the electrochemical window.

[0016] Further preferably, the metal halide comprises a MaXb-type metal halide, wherein M is selected from at least one of a transition metal (such as at least one of Fe, Ti, Mn, Zr, Ni or Y), a poor metal (such as at least one of Al, In or Sn), an alkaline earth metal (such as Mg and / or Ca), a lanthanide (such as at least one of La, Ce, Dy or Yb), X is selected from a halogen element (such as at least one of F, Cl, Br or I), a>0, b>0.

[0017] For example, a may be 1, 1.5, 2, 2.5 or 3, and b may be 1, 1.5, 2, 2.5 or 3, etc.

[0018] Further preferably, the halide solid electrolyte includes Li a MX b type halide solid electrolyte and / or Li a MOX b A type halide solid electrolyte, wherein M is selected from at least one of In, Sc, Cu, Zn, Cd, Mg or Ca, X is selected from at least one of halogen elements, 1.5≤a≤4.5, and b>0.

[0019] For example, the halide solid electrolyte may be Li 1.5 In 0.5 Cu 0.75 Cl 4.5 、Li 4.5 In 0.1 Cd 1.35 Cl 7.5 Or at least one of Li3InCl6.

[0020] In a second aspect, the present invention provides a method for preparing the composite sulfide solid electrolyte as described in the first aspect, the preparation method comprising the following steps:

[0021] The composite sulfide solid electrolyte matrix material and the halide material are mixed, subjected to heat treatment, and then subjected to cooling treatment to obtain the composite sulfide solid electrolyte.

[0022] It should be noted that the cooling process in the present invention is different from the conventional natural cooling process, but is a regular cooling process achieved at a certain cooling rate.

[0023] The present invention preliminarily realizes the coating of the halide material on the surface of the sulfide solid electrolyte through a mixing method; then, through the coordinated cooperation of heat treatment and subsequent cooling treatment, not only the tight coating of the halide material coating layer is completed, but also the interface reaction between the halide material and the sulfide solid electrolyte at the interface is achieved to form an interface reaction layer; thereby completing the modification treatment of the sulfide solid electrolyte.

[0024] In the present invention, if the temperature is not lowered after the heat treatment, it is impossible to maintain the high temperature phase and the interface reaction layer with a certain reaction depth.

[0025] Preferably, the median particle size D501 of the sulfide solid electrolyte material to be composited and the median particle size D502 of the halide material satisfy: D501 ≥ 1.5D502, for example, 1.5D502, 1.6D502, 1.7D502, 1.8D502, 1.9D502, 2D502, 2.3D502, 2.5D502, 3D502, 3.5D502, 4D502, 4.5D502, 5D502, 5.5D502, 6D502, 6.5D502, 7D502, 7.5D502, 8D502, 8.5D502, 9D502, 9.5D502 or 10D502, etc., but are not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0026] For the present invention, the median particle size D501 of the sulfide solid electrolyte material to be composited and the median particle size D502 of the halide material satisfy: D501≥1.5D502, which is more conducive to the halide material being coated on the surface of the sulfide solid electrolyte, and the coating effect is more excellent.

[0027] Preferably, the median particle size D501 of the sulfide solid electrolyte to be composited is 500nn~10μm, for example, 500nm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm or 10μm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] Preferably, the median particle size D502 of the halide material is 200 nm to 1 μm, for example, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, 900 nm or 1 μm, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0029] In the present invention, the median particle size D501 of the composite sulfide solid electrolyte is regulated to be 500nn~10μm and / or the median particle size D502 of the halide material is regulated to be 200nm~1μm, which can further exert the synergistic effect of the two and improve the performance of the composite solid electrolyte.

[0030] Preferably, the mixing method comprises any one of grinding, ball milling or high-speed stirring, or a combination of at least two thereof.

[0031] Preferably, the volume ratio of the sulfide solid electrolyte matrix material to be composited and the halide material is (51-99):(49-1), preferably (80-95):(20-5), for example, 70:30, 80:20, 85:15, 90:10 or 95:5.

[0032] It should be noted that the volume of the material in the present invention can be obtained by dividing the mass of the material by the true density of the material, and then calculating the volume ratio of the material.

[0033] In the present invention, the volume ratio of the sulfide solid electrolyte matrix material to be composited and the halide material is regulated to (80-95):(20-5), which is conducive to material coating and can better realize the construction of an interface reaction layer with controllable reaction depth.

[0034] Preferably, the grinding time is 20 to 180 min, for example, 20 min, 50 min, 80 min, 100 min, 120 min, 150 min or 180 min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0035] Preferably, the ball mill rotation speed is 180-500 rpm, for example, 180 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] Preferably, the ball milling time is 20 to 180 min, for example, 20 min, 50 min, 80 min, 100 min, 120 min, 150 min or 180 min, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0037] Preferably, the rotation speed of the high-speed stirring is 1000-30000 r / min, for example, 1000 r / min, 3000 r / min, 5000 r / min, 8000 r / min, 10000 r / min, 13000 r / min, 15000 r / min, 18000 r / min, 20000 r / min, 23000 r / min, 25000 r / min, 28000 r / min or 30000 r / min, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0038] Preferably, the high-speed stirring time is 1 to 10 minutes, for example, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes or 10 minutes, etc., but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0039] Furthermore, the present invention has found that since sulfide electrolytes are more sensitive to moisture in the air, their operating environment requirements are high. When sulfide electrolyte materials and halide electrolyte materials are mixed under an inert atmosphere, the environment can be effectively avoided from affecting the final prepared sulfide. The mixing can be carried out under an inert atmosphere.

[0040] Preferably, the heat treatment is performed under a vacuum environment or under a protective atmosphere.

[0041] It is understood that the protective atmosphere in the present invention is a conventional gas environment that does not affect the normal progress of the reaction; for example, it can be a nitrogen atmosphere and / or an inert gas atmosphere, and the inert gas includes at least one of helium, argon or neon.

[0042] Preferably, the holding time of the heat treatment is 60-300°C, for example, 60°C, 80°C, 100°C, 125°C, 150°C, 175°C, 200°C, 225°C, 250°C, 275°C or 300°C, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0043] In the present invention, the holding time of the heat treatment is further preferably 60 to 300°C, which can not only avoid the decomposition of the halide caused by excessively high temperature, but also make the structure of the coated sulfide electrolyte more stable. At the same time, it is also beneficial to the occurrence of interfacial reactions during the subsequent cooling treatment, and thus is more conducive to improving the structural stability and electrochemical stability of the sulfide electrolyte.

[0044] Preferably, the holding time of the heat treatment is 1 to 24 hours, for example, 1 hour, 3 hours, 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours or 24 hours, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0045] Preferably, the ambient temperature during the cooling treatment is -100 to 25°C, for example, -100°C, -75°C, -25°C, 0°C, 5°C, 10°C, 15°C, 20°C or 25°C, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0046] Preferably, the cooling time is 1 min to 1 h, for example, 1 min, 10 min, 20 min, 30 min, 40 min, 50 min or 60 min, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] The present invention has found that the cooling process affects the degree of the interfacial reaction between the halide material and the sulfide solid electrolyte material; by regulating the ambient temperature and cooling time during the cooling process, the cooling rate can be further limited, thereby achieving the purpose of regular cooling at a fixed cooling rate, thereby effectively regulating the interfacial reaction process and being more conducive to the formation of the interfacial reaction layer.

[0048] It should also be noted that:

[0049] The cooling treatment in the present invention refers to the process of cooling from the holding temperature of the heat treatment to room temperature, and the room temperature is the temperature in the routine experimental process of those skilled in the art, which can be 20-30°C, for example, 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C, etc.

[0050] The present invention does not impose any special restrictions on the composite sulfide solid electrolyte, and the material types are selected according to conventional technical solutions, for example, Li7P3S11, β-Li3PS4, Li6PS5Cl, Li6PS5Br, Li7P2S8I, Li4PS4I, Li6PS5Cl x Br 1-x 、Li6PS5Cl y I1-y or Li6PS5Br z I 1-z Any one or a combination of at least two of , where 0≤x≤1, 0≤y≤1, and 0≤z≤1.

[0051] For example, x can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc.; y can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc.; and z can be 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc.

[0052] In a third aspect, the present invention further provides a lithium-ion battery, comprising the composite sulfide solid electrolyte as described in the first aspect or the composite sulfide solid electrolyte prepared by the preparation method as described in the second aspect.

[0053] Preferably, the lithium-ion battery comprises an all-solid-state battery.

[0054] For the present invention, the provided composite sulfide solid electrolyte is preferably used in an all-solid-state battery, and is more preferably used in the positive electrode of an all-solid-state battery; however, its possible use in a liquid lithium-ion battery and its use in the solid electrolyte layer or negative electrode of an all-solid-state battery are not excluded. Those skilled in the art can make adaptive selections and adjustments based on actual needs.

[0055] Preferably, the all-solid-state battery comprises a positive electrode, a solid electrolyte layer and a negative electrode, and the positive electrode comprises the composite sulfide solid electrolyte.

[0056] Preferably, the positive electrode active material in the positive electrode includes any one of a lithium cobalt oxide positive electrode material, a ternary positive electrode material or a lithium-rich manganese-based oxide positive electrode material, or a combination of at least two thereof.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) The composite sulfide solid electrolyte provided by the present invention, in addition to the role of the coating layer of the halide material and the sulfide solid electrolyte matrix, also has an interface reactant formed by the halide material and the sulfide solid electrolyte through the interface reaction at the interface contact between the two, forming a self-limiting modification layer. The interface reactant cooperates with the halide material in the coating layer and works together, which not only suppresses the electrochemical window and mechanical properties of the sulfide solid electrolyte, but also improves its mechanical stability and electrochemical stability with the positive electrode material. At the same time, it also suppresses the interface reaction of the sulfide matrix and further suppresses the problem of other decomposition products appearing when the matrix surface is only coated with the halide material; it also improves the lithium ion conductivity of the composite sulfide solid electrolyte; broadens its application in all-solid-state batteries, and provides an effective solution for the industrialization of all-solid-state batteries.

[0059] (2) The present invention preliminarily realizes the coating of halide materials on the surface of sulfide solid electrolyte by a mixing method; and then, through the coordinated cooperation of heat treatment and subsequent cooling treatment, not only the tight coating of the halide material coating layer is completed, but also the interface reaction between the halide material and the sulfide solid electrolyte at the interface is achieved to form an interface reaction layer; thereby completing the modification treatment of the sulfide solid electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] Figure 1 This is an SEM image of the composite sulfide solid electrolyte provided in Example 1.

[0061] Figure 2 This is the XPS spectrum of the surface and the etched interface of the composite sulfide solid electrolyte provided in Example 1. DETAILED DESCRIPTION

[0062] The technical solution of the present invention is further described below by way of specific embodiments. It should be understood by those skilled in the art that the embodiments are merely to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0063] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application are intended to cover non-exclusive inclusions.

[0064] In the description of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly indicate the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0065] Example 1

[0066] This embodiment provides a composite sulfide solid electrolyte, which includes a sulfide solid electrolyte matrix Li6PS5Cl (LPSC) and a composite layer coated on the surface of the sulfide solid electrolyte matrix;

[0067] The composite layer includes an interface reaction layer and a coating layer from the inside to the outside, the coating layer includes a halide material Li3InCl6, and the interface reaction layer includes an interface reactant after the halide material reacts with the surface of the sulfide solid electrolyte matrix;

[0068] The preparation method of the composite sulfide solid electrolyte is as follows:

[0069] (1) LPSC powder with a median particle size of 5 μm and Li3InCl6 solid electrolyte with a median particle size of 500 nm were ground in a mortar at a volume ratio of 80:20 under an argon atmosphere for 30 minutes, so that Li3InCl6 was coated on the surface of the LPSC powder particles to initially form a coating layer. The powder was then transferred to a vacuum tube and heat treated at 80°C for 6 hours, followed by cooling treatment. During the cooling process, the ambient temperature was -25°C and the cooling time was 30 minutes. The temperature was regularly cooled to room temperature of 25°C at a fixed cooling rate to obtain the composite sulfide solid electrolyte.

[0070] Figure 1 The SEM image of the composite sulfide solid electrolyte provided in Example 1 is shown. Figure 1 It can be seen that the Li3InCl6 solid electrolyte particles are evenly coated on the surface of LPSC.

[0071] Figure 2 The XPS spectra of the surface and the etched interface of the composite sulfide solid electrolyte provided in Example 1 are shown. Figure 2 The XPS data of the In3d spectra and peak fitting of the surface and interface of the Li3InCl6 solid electrolyte composite sulfide solid electrolyte after etching show that the binding state of In changes to In2S3 after etching to a depth of 100nm, indicating the formation of an interfacial reaction layer between the Li3InCl6 solid electrolyte and the LPSC.

[0072] Example 2

[0073] This embodiment provides a composite sulfide solid electrolyte, which includes a sulfide solid electrolyte matrix Li6PS5Cl (LPSC) and a composite layer coated on the surface of the sulfide solid electrolyte matrix;

[0074] The composite layer includes an interface reaction layer and a coating layer from the inside to the outside, the coating layer includes a halide material Li3InCl6, and the interface reaction layer includes an interface reactant after the halide material reacts with the surface of the sulfide solid electrolyte matrix;

[0075] The preparation method of the composite sulfide solid electrolyte is as follows:

[0076] (1) LPSC powder with a median particle size of 500 nm and Li3InCl6 solid electrolyte with a median particle size of 200 nm were stirred at a volume ratio of 85:15 in an argon atmosphere at a speed of 3000 r / min for 3 minutes, so that Li3InCl6 was coated on the surface of the LPSC powder particles to initially form a coating layer. The powder was then transferred to a vacuum tube and heat treated at 150°C for 3 hours, and then cooled. During the cooling process, the ambient temperature was 25°C, the cooling time was 10 minutes, and the temperature was regularly cooled to room temperature of 25°C at a fixed cooling rate to obtain the composite sulfide solid electrolyte.

[0077] Example 3

[0078] This embodiment provides a composite sulfide solid electrolyte, which includes a sulfide solid electrolyte matrix Li6PS5Cl (LPSC) and a composite layer coated on the surface of the sulfide solid electrolyte matrix;

[0079] The composite layer includes an interface reaction layer and a coating layer from the inside to the outside, the coating layer includes a halide material Li3InCl6, and the interface reaction layer includes an interface reactant after the halide material reacts with the surface of the sulfide solid electrolyte matrix;

[0080] The preparation method of the composite sulfide solid electrolyte is as follows:

[0081] (1) LPSC powder with a median particle size of 10 μm and Li3InCl6 solid electrolyte with a median particle size of 1 μm were stirred at a high speed of 5000 r / min for 2 minutes in an argon atmosphere at a volume ratio of 90:10, so that Li3InCl6 was coated on the surface of the LPSC powder particles to initially form a coating layer. The powder was then transferred to a vacuum tube and heat treated at 300°C for 0.5h, and then cooled. During the cooling process, the ambient temperature was -100°C and the cooling time was 1h. The temperature was regularly cooled to room temperature of 25°C at a fixed cooling rate to obtain the composite sulfide solid electrolyte.

[0082] Example 4

[0083] The difference between this embodiment and embodiment 1 is that the halide material in step (1) of this embodiment is Li2ZrF6.

[0084] The rest of the preparation methods and parameters were the same as those in Example 1.

[0085] Example 5

[0086] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the sulfide solid electrolyte to be composited is Li7P3S11, and the halide material is Li 1.5 In 0.5 Cu 0.75 Cl 4.5 .

[0087] The rest of the preparation methods and parameters were the same as those in Example 1.

[0088] Example 6

[0089] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the median particle size of LPSC is 700 nm.

[0090] The rest of the preparation methods and parameters were the same as those in Example 1.

[0091] Example 7

[0092] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the cooling time is 1.5 hours.

[0093] The rest of the preparation methods and parameters were the same as those in Example 1.

[0094] Comparative Example 1

[0095] The difference between this comparative example and Example 1 is that the composite sulfide solid electrolyte in this comparative example is a sulfide solid electrolyte matrix.

[0096] In the preparation method, the composite sulfide solid electrolyte is not subjected to any treatment.

[0097] The rest of the preparation methods and parameters were the same as those in Example 1.

[0098] Comparative Example 2

[0099] The difference between this comparative example and Example 1 is that the composite sulfide solid electrolyte in this comparative example does not contain an interface reaction layer.

[0100] In step (2) of the preparation method, after the heat treatment, a natural cooling treatment is performed.

[0101] The rest of the preparation methods and parameters were the same as those in Example 1.

[0102] [Compound sulfide solid electrolyte performance test]

[0103] Ionic conductivity: 100 mg of the composite sulfide solid electrolyte powder provided in the examples and comparative examples was weighed and placed in an insulating outer cylinder. The powder was pressurized at a pressure of 300 MPa and subjected to an AC impedance spectroscopy test. The ionic conductivity of the electrolyte material was calculated based on the impedance value and the Arrhenius equation.

[0104] Voltage window test: The composite sulfide solid electrolyte powder and conductive carbon powder provided in the examples and comparative examples were weighed in a weight ratio of 70:30 and ground evenly using an agate mortar. In an insulating outer cylinder with a diameter of 10 mm, 20 mg of the above composite sulfide solid electrolyte-conductive carbon powder mixture and 20 mg of Li6PS5Cl were stacked. It was press-formed at a pressure of 360 MPa, and then a piece of lithium foil was stacked on the Li6PS5Cl side. It was press-formed at a pressure of 100 MPa. After that, a stainless steel collector was configured on the stack, and a collector lead was laid on the collector. A linear sweep voltammetry test was performed with a scan range of 2.5-7 V and a scan rate of 0.1 mV / S. A tangent was drawn to the oxidation peak of the test curve, and the intersection of the tangent and the horizontal axis was the oxidation potential of the material.

[0105] The test results of the above tests are shown in Table 1.

[0106] Table 1

[0107]

[0108]

[0109] [Battery preparation and performance testing]

[0110] Battery preparation: In an argon glove box, sulfide electrolyte, positive electrode active material Li (Ni 0.8 Co 0.1 Mn 0.1)O2(NCM811) were weighed at a weight ratio of 20:80. They were ground evenly using an agate mortar to produce a composite positive electrode material. In an insulating outer cylinder with a diameter of 10 mm, 14 mg of the above-mentioned positive electrode material and 70 mg of sulfide electrolyte material Li6PS5Cl(were layered. It was press-formed at a pressure of 360 MPa to obtain a positive electrode sheet and a solid electrolyte layer. Subsequently, a piece of aluminum foil was stacked on one side of the positive electrode sheet to form a current collector on one side of the positive electrode sheet. Then, an indium sheet with a thickness of 200 μm and a diameter of 10 mm was placed on the side of the solid electrolyte layer away from the positive electrode sheet as a negative electrode material. It was press-formed at a pressure of 80 MPa to produce a stack consisting of a positive electrode sheet, a solid electrolyte layer and a negative electrode sheet. Subsequently, a stainless steel current collector was arranged on the stack, and a current collector lead was laid on the current collector to obtain a solid-state battery.

[0111] Performance test: The assembled solid-state battery was subjected to a cycle performance test under the following test conditions: a current density of 0.1C for 3 cycles and then 0.3C for 200 cycles, with a voltage range of 2.7-4.5V (Li+ / Li).

[0112] The test results of the above tests are shown in Table 2.

[0113] Table 2

[0114]

[0115] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A composite sulfide solid electrolyte, characterized in that: The composite sulfide solid electrolyte comprises a sulfide solid electrolyte matrix and a composite layer coated on the surface of the sulfide solid electrolyte matrix; The composite layer includes an interface reaction layer and a coating layer from the inside to the outside, the coating layer includes a halide material, and the interface reaction layer includes an interface reactant after the halide material undergoes an interface reaction with the surface of the sulfide solid electrolyte matrix.

2. The composite sulfide solid electrolyte according to claim 1, characterized in that The halide material includes metal halide and / or halide solid electrolyte.

3. A method for preparing the composite sulfide solid electrolyte according to claim 1 or 2, characterized in that: The preparation method comprises the following steps: The composite sulfide solid electrolyte matrix material and the halide material are mixed, subjected to heat treatment, and then subjected to cooling treatment to obtain the composite sulfide solid electrolyte.

4. The preparation method according to claim 3, characterized in that The median particle size D501 of the sulfide solid electrolyte material to be composited and the median particle size D502 of the halide material satisfy: D501 ≥ 1.5D502; Preferably, the median particle size D501 of the sulfide solid electrolyte to be composited is 500nn~10μm; Preferably, the median particle size D502 of the halide material is 200 nm to 1 μm.

5. The preparation method according to claim 3, characterized in that The mixing method includes any one of grinding, ball milling or high-speed stirring or a combination of at least two thereof; Preferably, the grinding time is 20 to 180 minutes; Preferably, the ball milling speed is 180 to 500 rpm, and the ball milling time is 20 to 180 min; Preferably, the rotation speed of the high-speed stirring is 1000 to 30000 r / min, and the time of the high-speed stirring is 1 to 10 minutes.

6. The preparation method according to claim 3, characterized in that The volume ratio of the sulfide solid electrolyte matrix material to be composited to the halide material is (51-99):(49-1), preferably (80-95):(20-5).

7. The preparation method according to claim 3, characterized in that The heat treatment is carried out in a vacuum environment or in a protective atmosphere; Preferably, the heat treatment is carried out at a temperature of 60 to 300° C. for a period of 1 to 24 hours.

8. The preparation method according to claim 3 or 7, characterized in that The ambient temperature during the cooling process is -100 to 25° C., and the cooling time is 1 minute to 1 hour.

9. A lithium-ion battery, characterized in that: The lithium-ion battery comprises the composite sulfide solid electrolyte according to claim 1 or 2 or the composite sulfide solid electrolyte prepared by the preparation method according to any one of claims 3 to 8.

10. The lithium-ion battery according to claim 9, characterized in that The lithium-ion battery includes an all-solid-state battery; Preferably, the all-solid-state battery comprises a positive electrode, a solid electrolyte layer and a negative electrode, and the positive electrode comprises the composite sulfide solid electrolyte.

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