Sulfide solid electrolyte with coating layer, preparation method of sulfide solid electrolyte and solid-state battery

Abstract

The invention provides a sulfide solid electrolyte with a coating layer, a preparation method of the sulfide solid electrolyte and a solid-state battery. The sulfide solid electrolyte with the coating layer comprises an inner core and the coating layer, the outer surface of the inner core is provided with the coating layer, the coating layer comprises a hydrophobic layer and a hydrophilic layer, the inner core is a sulfide electrolyte, the outer surface of the inner core is provided with the hydrophilic layer, and the hydrophobic layer is a hydrophobic layer. The hydrophobic layer is arranged on the outer surface, far away from the inner core, of the hydrophilic layer, and the hydrophilic layer and the hydrophobic layer are connected through a covalent bond; the hydrophilic layer comprises a hydrophilic chain segment, the hydrophilic chain segment contains oxygen atoms, and the hydrophobic layer comprises a hydrophobic chain segment. According to the sulfide solid electrolyte with the coating layer provided by the invention, hydrolysis and oxidation reactions of the sulfide electrolyte are inhibited, the interface impedance of a positive electrode material and the sulfide electrolyte is reduced, the interface side reaction of the sulfide electrolyte and Li-In alloy is blocked, the cycle life of a battery is prolonged, and the energy density of the battery is improved.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state lithium metal battery technology, and more particularly to a sulfide solid electrolyte with a coating layer, its preparation method, and a solid-state battery. Background Technology

[0002] The use of sulfide electrolytes in lithium metal batteries presents the following three problems.

[0003] Question 1: The air stability of sulfide electrolytes; Sulfide electrolytes (such as Li) 5.5 PS 4.5 Cl 1.5 Because it is sensitive to air, it is prone to oxidative decomposition when exposed to environments containing moisture or oxygen, generating byproducts such as Li3PO4 and sulfur-containing oxides, while releasing corrosive gases (such as HCl and PH3), leading to corrosion of the electrode material and a significant increase in interfacial impedance (from the initial value of several hundred Ω·cm). 2 Increased to several thousand Ω·cm 2 While traditional methods involving passivation coatings (such as LiNbO3) on the surface of sulfide electrolytes can partially alleviate the decomposition problem, the inherent low conductivity (<10) of these passivation coatings remains a significant concern. -8 The high chemical potential difference (Δχ > 2.0 eV) between the Li (S / cm) and sulfide electrolytes exacerbates the interfacial Li + Uneven distribution creates a dynamic ion transport bottleneck, further deteriorating battery cycle stability and energy density.

[0004] Question 2: The interface between the sulfide electrolyte and the high-nickel cathode; The interfacial issues between cathode materials such as high-nickel cathodes (NCM811) and sulfide electrolytes mainly lie in oxygen vacancy activation and side reactions, particularly at high voltages (>4.3 V vs Li). + / Li + Under cycling, oxygen vacancies on the surface of the cathode material undergo redox reactions with the sulfide electrolyte, leading to the dissolution of transition metals (such as Ni). 2+ Co 2+ As the SEI film continues to deplete, battery capacity decays and rate performance decreases. Taking NCM811 as an example, the specific situation is as follows: NCM811 surface oxygen vacancies (concentration > 10) 18 cm -3 At temperatures above 4.2 V, S in LiPSCl... 2- The reaction generates a Li₂SO₄ insulating layer (thickness > 50 nm), resulting in a capacity decay rate as high as 20% / 50 cycles; Ni 2+ and Co 2+ Dissolved into the electrolyte, allowing LiPSCl to dissolve into Li +The migration count decreased from 0.8 to 0.5, resulting in a 40% drop in rate performance.

[0005] Regarding question two, the existing technical solution involves coating the cathode material, specifically as follows: The first method is to use a LiTaO3 coating layer. Yamada (2023) used LiTaO3 to coat NCM811, reducing the interfacial impedance to 100 Ω·cm2. However, the coating layer thickness was uneven (CV value > 15%), and the crack density increased to 30 cracks / mm after cycling. 2 The second method uses a conductive polymer coating. Zhou (2024) used PEDOT:PSS to coat the cathode material, increasing the conductivity to 10. -3 The interfacial impedance is S / cm, but PEDOT:PSS undergoes oxidative decomposition during cycling, causing the interfacial impedance to rebound to 300 Ω·cm. 2 The third method involves using Al2O3 to coat the cathode material. However, the inorganic coating layer (such as Al2O3) is mechanically brittle and cannot adapt to the volume expansion of the cathode (ΔV≈12%), resulting in an increase in crack density after cycling.

[0006] Question 3: Compatibility issues between lithium metal anodes and sulfide electrolytes; The compatibility issues between lithium metal anodes and sulfide electrolytes mainly stem from dendrite growth and interfacial corrosion. Firstly, there is Li₂S deposition. The reaction between sulfide electrolytes and lithium metal generates Li₂S (conductivity > 10³ S / cm), forming conductive dendrites that pierce the electrolyte, causing short circuits and resulting in a cycle life of less than 5 cycles. Secondly, there is the issue of In dissolution. In lithium-indium alloys (Li-In), In reacts with LiPSCl to form Li₃In ​​(volume expansion rate > 200%), leading to interfacial structural damage. These interfacial side reactions of sulfide electrolytes with lithium metal (such as Li₂S deposition) and In dissolution issues in lithium-indium alloys result in short battery cycle life (< 10 cycles) and rapid capacity decay (less than 20% after 10 cycles). Traditional lithium salts (such as LiPF₆) cannot effectively suppress dendrite growth in solid-state systems, and the introduction of liquid electrolytes increases interfacial complexity.

[0007] Regarding question three, traditional methods include artificial SEI films and alloy interface passivation. However, artificial SEI films, formed by LiF deposition, suffer from SEI layer rupture during cycling, failing to suppress dendrite penetration and leaving the battery at risk of short circuits. Alloy interface passivation using a Li3N coating can mitigate In dissolution, but the electronic conductivity of Li3N (10⁻⁶ Ω·cm) is low. -4 The S / cm ratio triggered a side reaction, resulting in a volume retention rate of less than 80%.

[0008] To address the three issues mentioned above, there have been attempts to coat sulfide electrolytes, as detailed below. Firstly, there were early inorganic oxide coating interface control strategies (2015-2020). Kamaya (2011) first proposed coating a LiNbO3 layer (2-5 nm thick) onto the LiPSCl surface using ALD technology, which could reduce the interfacial impedance from 1200 Ω·cm. 2 Reduced to 500 Ω·cm 2 However, the electronic insulation of LiNbO3 leads to a 15% decrease in the charge transport efficiency of the cathode material. Then, polymer interface modification was employed; Zhang (2018) used polydopamine (PDA) to coat LiPSCl, reducing the interfacial contact resistance to 200 Ω·cm. 2 However, the PDA swells during cycling, leading to interfacial failure. Next came the design of composite electrolytes (2021-2023). Wang (2022) developed a Li3YCl6-LiPSCl composite electrolyte, extending the electrochemical window to 5 V, but the Li-Y-Cl phase and sulfide exhibited lattice mismatch, resulting in an interfacial shear strength of less than 10 MPa. Chen (2023) constructed a Li6PS5Cl-Li... 10 GeP2S 12 Gradient layer, interface impedance reduced to 150 Ω·cm 2 However, the high cost of Ge limits its large-scale application. Recent advancements in surface functionalization modification (2024-2025) include Liu (2024), who used F2 plasma to treat LiPSCl surfaces, generating a LiF protective layer that reduced the interfacial impedance from 220 Ω·cm. 2 Reduced to 80 Ω·cm 2 However, plasma equipment has high investment costs (>5 million USD / unit). Kim (2025) used zeolite molecular sieves to encapsulate LiPSCl, which reduced water and oxygen permeability by 90%, but the difference in the interfacial thermal expansion coefficients between the molecular sieve and the electrolyte caused stratification after cycling.

[0009] The above-mentioned coating of sulfide electrolyte LiPSCl also presents the following problems: high interfacial impedance with the positive electrode or high cost. Summary of the Invention

[0010] To address the problems of existing sulfide electrolytes, such as high air sensitivity, increased interfacial impedance due to decomposition, capacity decay due to interfacial side reactions with positive electrode materials, capacity decay and low cycle life due to interfacial compatibility issues with lithium metal negative electrodes, this invention provides a sulfide solid electrolyte with a coating layer, its preparation method, and a solid-state battery.

[0011] In a first aspect, the present invention provides a sulfide solid electrolyte with a coating layer, comprising a core and a coating layer, wherein the coating layer is disposed on the outer surface of the core, the coating layer comprising a hydrophobic layer and a hydrophilic layer, the core being a sulfide electrolyte, the hydrophilic layer being disposed on the outer surface of the core, and the hydrophobic layer being disposed on the outer surface of the hydrophilic layer away from the core, the hydrophilic layer and the hydrophobic layer being connected by covalent bonds; the hydrophilic layer comprising hydrophilic segments containing oxygen atoms, and the hydrophobic layer comprising hydrophobic segments.

[0012] Preferably, the thickness of the hydrophilic layer is greater than the thickness of the hydrophobic layer.

[0013] Preferably, the chemical formula of the sulfide electrolyte is Li. x PS y Cl z , where 5 < x < 6, 4 < y < 5, and satisfies x + 5 = 2y + z; The hydrophobic segment includes one of a polystyrene segment and a polytetrafluoroethylene segment; the hydrophilic segment includes one of a polyethylene oxide segment and a polyethylene glycol segment.

[0014] Preferably, the thickness of the hydrophilic layer is 3~15nm, the thickness of the hydrophobic layer is 3~15nm, and the D50 particle size of the core is 0.5~15μm.

[0015] Preferably, the molar ratio of the hydrophilic segment to the hydrophobic segment is 1:(0.5~5). Preferably, the coating layer further includes doped particles, which are lithium-containing compounds, including at least one of LiFSI, LiTFSI, LiDFOB, LiPF6, and lithium niobate. The total mass of the hydrophilic and hydrophobic segments is m1, and the mass of the doped particles is m2, where m1:m2 is 10:1 to 100:1.

[0016] Secondly, this application provides a method for preparing the aforementioned sulfide solid electrolyte with a coating layer, comprising the following steps: Obtain a block copolymer containing the hydrophilic segment and the hydrophobic segment; The block copolymer, sulfide electrolyte, and organic solvent are mixed evenly to obtain a first mixed solution. The first mixed solution is heated, and after heating, it is dried to obtain the sulfide solid electrolyte with a coating layer.

[0017] Preferably, the mass ratio of the block copolymer to the sulfide electrolyte is 1:20 to 1:60; And / or, the organic solvent includes at least one of toluene, xylene, and chlorobenzene, and the mass ratio of the organic solvent to the block copolymer is 10:1 to 100:1.

[0018] Preferably, the process of obtaining the sulfide solid electrolyte with a coating layer by drying after heating includes the following steps: After heating, a second mixed solution is obtained. The second mixed solution is dried for the first time at a first stage temperature T1. After the first drying, it is dried for the second time at a second stage temperature T2. After the second drying, it is dried for the third time at a third stage temperature T3. T1 is 105~115℃, T2 is 70~90℃, and T3 is 40~60℃; The first drying time t1 is 12-24 hours; the second drying time t2 is 6-12 hours; and the third drying time t3 is 3-6 hours.

[0019] Thirdly, this application provides a solid-state battery, including the sulfide solid electrolyte with a coating layer as described above, or the sulfide solid electrolyte prepared by the preparation method of the sulfide solid electrolyte with a coating layer as described above.

[0020] The sulfide solid electrolyte with a coating layer provided in this application has the following effects: 1) Electrolyte air stability: The hydrophobic segments in the hydrophobic layer form a hydrophobic barrier (contact angle > 150°) to block the penetration of water / oxygen, inhibit the hydrolysis and oxidation of sulfide electrolyte, so that the ionic conductivity of sulfide electrolyte remains > 2 mS / cm after exposure to RH 30% environment for 24 hours, and remains > 3 mS / cm after exposure to RH < 10% environment (compared to only 0.0001 mS / cm in traditional process), breaking through the production limitation of needing inert gas protection; 2) Cathode interface optimization: A hydrophilic layer is applied to the surface of the sulfide electrolyte. This hydrophilic layer contains hydrophilic segments that react with water to generate LiOH, inhibiting the formation of HCl / PH3 and blocking the "hydrolysis-oxidation" chain reaction, thus preventing the oxidative decomposition of the sulfide electrolyte. The oxygen atoms in these hydrophilic segments can fill oxygen vacancies on the surface of the cathode material (such as the high-nickel ternary cathode material NCM811). Furthermore, the hydrophilic segments also contribute to the dynamic LiOH reaction. + Coordination repairs oxygen vacancies on the NCM811 surface, preferentially reacting with H2O to form inert LiOH, blocking the formation of corrosive products such as Li2SO4, and reducing the interfacial impedance between the cathode material and the sulfide electrolyte (interfacial impedance from >200 Ω·cm). 2 Reduced to <50 Ω·cm 2It can achieve a capacity retention rate of ≥84% after 100 cycles at a high voltage of 4.3 V, thus improving battery capacity decay; the hydrophobic segments it contains have an elastic modulus that is compatible with the positive electrode's volume expansion of ΔV≈12%; 3) Regarding anode compatibility, hydrophilic and hydrophobic segments work synergistically, with the hydrophilic segment dynamically regulating Li... + Flux distribution guides uniform lithium deposition and inhibits lithium dendrite growth; at the same time, the hydrophobic effect of the hydrophobic segments alleviates the dissolution of In in the negative electrode active material Li-In alloy, and the dense coating structure of the hydrophobic segments blocks the interfacial side reactions between the sulfide electrolyte and the Li-In alloy, thereby improving the battery cycle life and energy density. Attached Figure Description

[0021] Figure 1 The graph shows the specific capacity and coulombic efficiency of the solid-state battery obtained in Example 1 after 100 cycles of discharge. Figure 2 This is a 3000x scanning electron microscope image of the sulfide electrolyte in Comparative Example 1. Figure 3 This is an 8000x scanning electron microscope image of the sulfide solid electrolyte with a coating layer prepared in Example 1. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0023] To illustrate the technical solution of the present invention, specific embodiments are described below.

[0024] In one embodiment of the present invention, this application provides a sulfide solid electrolyte with a coating layer, comprising a core and a coating layer. The coating layer is disposed on the outer surface of the core. The coating layer includes a hydrophobic layer and a hydrophilic layer. The core is a sulfide electrolyte. The hydrophilic layer is disposed on the outer surface of the core. The hydrophobic layer is disposed on the outer surface of the hydrophilic layer away from the core. The hydrophilic layer and the hydrophobic layer are connected by covalent bonds. The hydrophilic layer includes hydrophilic segments containing oxygen atoms, and the hydrophobic layer includes hydrophobic segments.

[0025] The sulfide solid electrolyte provided in this application can be directly used in lithium metal solid-state batteries.

[0026] The hydrophilic and hydrophobic layers are connected by covalent bonds, which means that the hydrophilic segments are connected to the hydrophobic segments by covalent bonds, thus tightly binding the hydrophobic and hydrophilic layers together.

[0027] The sulfide solid electrolyte with a coating layer provided in this application has the following effects: 1) Electrolyte air stability: The hydrophobic segments in the hydrophobic layer form a hydrophobic barrier (contact angle > 150°) to block the penetration of water / oxygen, inhibiting the hydrolysis and oxidation of sulfide electrolytes. This allows the ionic conductivity of the sulfide electrolyte to remain > 2 mS / cm after 24 hours of exposure in a RH 30% environment, and > 3 mS / cm after exposure in a RH < 10% environment (compared to only 0.0001 mS / cm in traditional processes). This overcomes the production limitation of requiring inert gas protection conditions and reduces production costs. 2) Cathode interface optimization: A hydrophilic layer is applied to the surface of the sulfide electrolyte. This layer contains hydrophilic segments that react with water to generate LiOH, inhibiting the formation of HCl / PH3 and blocking the "hydrolysis-oxidation" chain reaction, thus preventing the oxidative decomposition of the sulfide electrolyte. The oxygen atoms in these hydrophilic segments can fill oxygen vacancies on the surface of the cathode material (such as the high-nickel ternary cathode material NCM811). Furthermore, the hydrophilic segments repair oxygen vacancies on the NCM811 surface through dynamic Li⁺ coordination, preferentially reacting with H₂O to generate inert LiOH, blocking the formation of corrosive products such as Li₂SO₄, and reducing the interfacial impedance between the cathode material and the sulfide electrolyte (interfacial impedance from >200 Ω·cm). 2 Reduced to <50 Ω·cm 2 It can achieve a capacity retention rate of ≥84% after 100 cycles at a high voltage of 4.3 V, thus improving battery capacity decay; the hydrophobic segments it contains have an elastic modulus that is compatible with the positive electrode's volume expansion of ΔV≈12%; 3) Regarding anode compatibility, hydrophilic and hydrophobic segments work synergistically, with the hydrophilic segment dynamically regulating Li... + Flux distribution guides uniform lithium deposition and inhibits lithium dendrite growth; at the same time, the hydrophobic effect of the hydrophobic segments alleviates the dissolution of In in the negative electrode active material Li-In alloy, and the dense coating structure of the hydrophobic segments blocks the interfacial side reactions between the sulfide electrolyte and the Li-In alloy, thereby improving the battery cycle life and energy density.

[0028] In some embodiments, the thickness of the hydrophilic layer is greater than the thickness of the hydrophobic layer.

[0029] Specifically, the hydrophilic layer is thicker than the hydrophobic layer, meaning the coating on the outer surface of the sulfide electrolyte has a gradient structure. The thinner hydrophobic layer effectively suppresses dendrite penetration, and its thinner structure reduces ion transport resistance. The thicker hydrophilic layer provides a stable ion conduction channel and buffers the volume expansion of the sulfide electrolyte, while its thicker structure enhances interfacial stability. This gradient coating structure of hydrophilic and hydrophobic layers works synergistically to effectively buffer the volume expansion of the sulfide electrolyte, reduce lithium dendrite formation, and contribute to improving battery cycle life and performance.

[0030] In some embodiments, the chemical formula of the sulfide electrolyte is Li x PS y Cl z , where 5 < x < 6, 4 < y < 5, and satisfies x + 5 = 2y + z.

[0031] Specifically, the sulfide electrolyte is selected from the chemical formula Li x PS y Cl z This is a compound in which 5 < x < 6, 4 < y < 5, and satisfies x + 5 = 2y + z. It belongs to the sulfide type of argillium sulfide, with space group Fd-3m and lattice parameter a = 5.94 Å. It contains argillium sulfide structure. x can be 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, etc., and y can be 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, etc.; at the same time, the values ​​of x and y must satisfy the condition x + 5 = 2y + z.

[0032] In some preferred embodiments, the sulfide solid electrolyte includes Li 5.5 PS 4.5 Cl 1.5 .

[0033] In some embodiments, the hydrophobic segment includes one of a polystyrene segment and a polytetrafluoroethylene segment; the hydrophilic segment includes one of a polyethylene oxide segment and a polyethylene glycol segment.

[0034] Specifically, polystyrene segments can form a hydrophobic barrier with a contact angle greater than 150° on the surface of the sulfide electrolyte, effectively blocking oxygen and water penetration and preventing the sulfide electrolyte from being oxidized. Simultaneously, the elastic modulus of the polystyrene segments can adapt to the positive electrode's volume expansion of ΔV≈12%, reducing post-cycle cracking. The dense coating structure of the polystyrene segments effectively blocks interfacial side reactions between the sulfide electrolyte and the negative electrode Li-In alloy, effectively reducing battery impedance and improving battery cycle performance and energy density. Specifically, the hydrophobic effect of polystyrene segments alleviates In dissolution from the Li-In alloy, extending battery cycle life to 500 hours (compared to <120 hours in conventional systems), and increasing the overall battery energy density to 350 Wh / kg (a 16.7% improvement over conventional sulfide batteries).

[0035] The oxygen atoms in the polyethylene oxide segments can fill the oxygen vacancies in the positive electrode active material and react with water to generate inert LiOH, inhibiting the formation of Li2SO4 and reducing the interfacial impedance with the positive electrode. The interfacial impedance is reduced from >200 Ω·cm² to <50 Ω·cm². After 100 cycles at a high voltage of 4.3 V, the battery retains ≥84% of its capacity while guiding uniform lithium deposition and inhibiting lithium dendrite growth (critical current density is increased to 3 mA / cm²), thus improving the battery's cycle performance and energy density.

[0036] The hydrophilic segment is selected from polyethylene glycol segments, utilizing the hydroxyl groups of the polyethylene glycol segments to react with Li. + Coordination; the hydrophobic segments are selected from polytetrafluoroethylene segments, and fluorinated blocks are introduced to enhance the hydrophobicity of the hydrophobic layer.

[0037] In some embodiments, the molecular weight of the hydrophobic segment is 10,000-1,000,000 g / mol, and the molecular weight of the hydrophilic segment is 5,000-500,000 g / mol.

[0038] The thickness of the hydrophilic layer can be adjusted by controlling the molecular weight of the hydrophilic segments, and the thickness of the hydrophobic layer can be adjusted by controlling the molecular weight of the hydrophobic segments, thus forming a coating layer with a thickness gradient.

[0039] In some embodiments, the molecular weight of the polystyrene segment is 10,000 to 1,000,000 g / mol; The molecular weight of the polyoxyethylene segments is 5,000~500,000 g / mol.

[0040] Specifically, the molecular weight of polystyrene segments can be in the following ranges: 10,000~50,000 g / mol, 50,000~100,000 g / mol, 100,000~800,000 g / mol, or 800,000~1,000,000 g / mol.

[0041] The molecular weight of the polyethylene oxide segments can be in the following ranges: 5,000~10,000 g / mol, 10,000~50,000 g / mol, 50,000~100,000 g / mol, 100,000~300,000 g / mol or 300,000~500,000 g / mol.

[0042] By controlling the molecular weight of polystyrene segments, the thickness of the hydrophobic layer can be adjusted; by controlling the molecular weight of polyethylene oxide segments, the thickness of the hydrophilic layer can be adjusted, forming a coating layer with a gradient structure, which enhances the binding force with the sulfide electrolyte interface.

[0043] In some embodiments, the thickness of the hydrophilic layer is 3-15 nm, the thickness of the hydrophobic layer is 3-15 nm, and the D50 particle size of the core is 0.5-15 μm.

[0044] Specifically, when the thickness of the hydrophilic layer, the thickness of the hydrophobic layer, and the D50 particle size of the core are within the above range, the gradient coating structure of the hydrophilic and hydrophobic layers is beneficial to effectively alleviate the volume expansion of the sulfide electrolyte, reduce the formation of lithium dendrites, effectively improve the battery cycle life and energy density, reduce the interfacial impedance between the positive electrode and the sulfide electrolyte, and improve the compatibility between the lithium metal negative electrode and the sulfide electrolyte.

[0045] The thickness of the hydrophilic layer can be 3~5nm, 5~8nm, 8~12nm or 12~15nm.

[0046] The thickness of the hydrophobic layer can be 3~5nm, 5~8nm, 8~12nm, or 12~15nm. The D50 particle size of the core can be 0.5~3μm, 3~6μm, 6~10μm, 10~12μm, or 12~15μm, as long as the D50 particle size of the core is within the range of 0.5~15μm.

[0047] In some embodiments, the molar ratio of the hydrophilic segment to the hydrophobic segment is 1:(0.5~5).

[0048] Specifically, in sulfide solid electrolytes with a coating layer, a molar ratio of hydrophilic to hydrophobic segments within the range of 1:(0.5~5) is beneficial for forming a coating structure with a thickness gradient. The hydrophilic and hydrophobic layers work together to reduce the interfacial impedance between the sulfide electrolyte and the positive electrode, reduce the formation of lithium dendrites, reduce side reactions between the negative electrode and the sulfide electrolyte, and improve the cycle performance and energy density of the battery.

[0049] Specifically, the molar ratio of hydrophilic segments to hydrophobic segments can be in the following ranges: 1: (0.5~1), 1: (1~1.5), 1: (1.5~2.5), 1: (2.5~3.5), 1: (3.5~4.5), or 1: (4.5~5.0).

[0050] In some embodiments, the coating layer further includes doped particles, the doped particles comprising lithium-containing compounds, the lithium-containing compounds comprising at least one of LiFSI, LiTFSI, LiDFOB, LiPF6, and lithium niobate, the total mass of the hydrophilic segments and the hydrophobic segments being m1, the mass of the doped particles being m2, and the ratio of m1 to m2 being 10:1 to 100:1.

[0051] The coating layer includes doped particles, which include the types mentioned above, and the ratio of m1 to m2 is limited to 10:1 to 100:1. This effectively prevents side reactions between the positive electrode and the sulfide electrolyte, further increases the battery cycle capacity retention rate, and enhances the battery's high voltage resistance, with a maximum withstand voltage of 5.2V.

[0052] In some preferred embodiments, the molar ratio of hydrophilic segments to hydrophobic segments is 1:(2.5~3.5).

[0053] In some preferred embodiments, the molar ratio of the hydrophilic segment to the hydrophobic segment is 1:3.

[0054] Secondly, this application provides a method for preparing the above-mentioned sulfide solid electrolyte with a coating layer, comprising the following steps: Obtain a block copolymer containing the hydrophilic segment and the hydrophobic segment; The block copolymer, sulfide electrolyte, and organic solvent are mixed evenly to obtain a first mixed solution. The first mixed solution is heated, and after heating, it is dried to obtain the sulfide solid electrolyte with a coating layer.

[0055] The block copolymer containing hydrophilic and hydrophobic segments is directly mixed with sulfide electrolyte and organic solvent, and then heated to facilitate the coating of the block copolymer onto the outer surface of the sulfide electrolyte, forming a uniform coating structure with a thickness gradient.

[0056] The method for preparing a sulfide solid electrolyte with a coating layer provided in this application has the following advantages: 1) The preparation process is simple, compatible with existing coating equipment, requires no additional drying or inert gas environment, improves process efficiency (by at least 30%), and enables low-cost large-scale production; 2) Block copolymers containing hydrophilic and hydrophobic segments are used for interface engineering of the sulfide electrolyte. Through the bicontinuous structure of hydrophilic and hydrophobic segments, a gradient coating structure layer with both mechanical strength and ion conductivity is constructed; 3) The resulting sulfide solid electrolyte with a coating layer effectively reduces the interfacial impedance between the positive electrode and the sulfide electrolyte, reduces the formation of lithium dendrites, reduces side reactions between the negative electrode and the sulfide electrolyte, and significantly improves the air stability of the resulting sulfide solid electrolyte, effectively preventing the sulfide electrolyte from being oxidized. It is suitable for lithium metal solid batteries containing high-nickel positive electrodes and lithium metal negative electrodes.

[0057] In some embodiments, the mass ratio of the block copolymer to the sulfide electrolyte is 1:20 to 1:60; And / or, the organic solvent includes at least one of toluene, xylene, and chlorobenzene, and the mass ratio of the organic solvent to the block copolymer is 10:1 to 100:1.

[0058] Specifically, a mass ratio of block copolymer to sulfide electrolyte of 1:(20~50) is beneficial for the block copolymer to adsorb onto the surface of the sulfide electrolyte, forming a sulfide solid electrolyte with a coating layer. The mass ratio of block copolymer to sulfide electrolyte can be in the following ranges: 1:(20~25), 1:(25~30), 1:(30~35), 1:(35~40), 1:(40~50), or 1:(50~60).

[0059] The organic solvent includes at least one of toluene, xylene, and chlorobenzene. The mass ratio of the organic solvent to the block copolymer is in the range of 10:1 to 100:1, which is beneficial for the organic solvent to dissolve the block copolymer.

[0060] Specifically, the block copolymer and sulfide electrolyte were dissolved in an organic solvent at 60±2℃ and mixed thoroughly for 12-24 hours. The 60±2℃ temperature facilitated the rapid and complete dissolution of the block copolymer in the organic solvent. It should be noted that ultrasonic vibration or other methods can be used to accelerate the dissolution of the block copolymer in the organic solvent.

[0061] The heating temperature is 80±5℃ and the heating time is 24~48h, which is conducive to the uniform and full adsorption of block copolymers on the surface of sulfide electrolyte, forming a gradient coating structure with a hydrophilic layer on the outer surface of sulfide electrolyte and a hydrophobic layer on the outer surface of hydrophilic layer away from sulfide electrolyte.

[0062] The hydrophobic segment is selected from polystyrene segments. These polystyrene segments form a dense hydrophobic layer through hydrophobic interactions, blocking H2O / O2 from contacting the sulfide electrolyte and inhibiting its hydrolysis. When the hydrophilic segment is selected from polyethylene oxide segments, the polyethylene oxide segments react with Li... + It coordinates preferentially with H2O to form LiOH, thus blocking the formation of HCl.

[0063] Polystyrene segments provide mechanical strength and hydrophobic properties to sulfide solid electrolytes.

[0064] When polyoxyethylene segments are in the form of Li-OP bonds with sulfide electrolytes, the hydrophilic layer and the core are tightly bound together, which improves the adsorption strength and reduces the interfacial resistance with the positive electrode.

[0065] In some preferred embodiments, the polystyrene segment molecular weight is 100,000 g / mol and the polyethylene oxide segment molecular weight is 50,000 g / mol, resulting in a block copolymer that can enhance the binding force with the sulfide electrolyte.

[0066] In some embodiments, drying after heating to obtain the sulfide solid electrolyte with a coating layer includes the following steps: After heating, a second mixed solution is obtained. The second mixed solution is dried for the first time at a first stage temperature T1. After the first drying, it is dried for the second time at a second stage temperature T2. After the second drying, it is dried for the third time at a third stage temperature T3. T1 is 105~115℃, T2 is 70~90℃, and T3 is 40~60℃; The first drying time t1 is 12-24 hours; the second drying time t2 is 6-12 hours; and the third drying time t3 is 3-6 hours.

[0067] Specifically, polystyrene segments and polyethylene oxide segments have different solubilities in organic solvents. Polystyrene segments are weakly polar, so during drying, the organic solvent preferentially evaporates from the hydrophobic layer, causing the hydrophobic layer to solidify first. The polyethylene oxide segments contained in the hydrophobic layer are highly polar, so the organic solvent is retained for a longer time, resulting in a larger thickness after solidification. This forms a gradient coating structure with a thickness gradient on the outer surface of the sulfide electrolyte.

[0068] This application involves drying the second mixed solution in three stages after heating, which is beneficial for forming a uniform coating structure on the surface of the sulfide electrolyte. The drying process is divided into three stages, with the drying temperatures in the three stages meeting the range of T1 being 105~115℃, T2 being 70~90℃, and T3 being 40~60℃, thus avoiding thermal stress that could cause cracks in the hydrophilic and hydrophobic layers.

[0069] The first stage temperature T1 can be in the following ranges: 105~108℃, 108~110℃, 110~113℃ or 113~115℃; the second stage temperature T2 can be in the following ranges: 70~75℃, 75~80℃, 80~85℃ or 85~90℃; the third stage temperature T3 can be in the following ranges: 40~45℃, 45~50℃, 50~55℃ or 55~60℃.

[0070] It should be noted that block copolymers can be obtained by purchasing or by preparation. Block copolymers are prepared by copolymerizing compounds containing hydrophilic and hydrophobic segments.

[0071] In some implementations, obtaining a block copolymer containing the hydrophilic segment of polyethylene oxide and the hydrophobic segment of polystyrene includes the following steps: Synthesis of PEO (polyethylene oxide) prepolymers (living anionic polymerization): Under an argon-filled protective atmosphere, 0.044 mmol of compound 1 and 0.2 mol of ethylene oxide, along with 40 mL of tetrahydrofuran, were added to a dry reactor. The reaction was carried out in a sealed reactor at 60°C for 24 hours. The polymerization reaction was quenched with methanol. The resulting prepolymer was purified by dissolving it in chloroform and then precipitating it in petroleum ether.

[0072] Using compound 1 as an initiator, living anionic polymerization of ethylene oxide was carried out to synthesize polyethylene oxide prepolymers with terminal quantitative functionalized TEMPO groups.

[0073] The structural formula of compound 1 is The structural formula of compound 2 is: Initiator compound 1 was prepared by reacting compound 2 with sodium in anhydrous tetrahydrofuran at 40°C.

[0074] Synthesis of SEO, a diblock copolymer containing polystyrene and polyethylene oxide segments (living radical polymerization): 5.0 g of PEO (polyethylene oxide) prepolymer (molecular weight Mn approximately 200,000), 20.0 g of St (styrene), 0.1 g of AIBN (azobisisobutyronitrile), and 20 mL of toluene were added to a 100 mL L Schlenk flask. The mixture was stirred at room temperature for 10 minutes. The flask was then degassed using a three-cycle freeze-evacuation-thawing process. Afterward, the reaction mixture was stirred at 120°C for 15 hours under an argon atmosphere. The resulting product was purified by extraction with cold water and cyclohexane to remove unreacted PEO prepolymer and the resulting PS homopolymer.

[0075] Styrene was subjected to living radical polymerization using AIBN (azobisisobutyronitrile) as an initiator and PEO (polyethylene oxide) prepolymer with nitroxide radicals as a macromolecular scavenger. This process produced diblock copolymers containing polystyrene and polyethylene oxide segments with a narrow molecular weight distribution.

[0076] In the above formula, m and n are related to the molar ratio of hydrophilic and hydrophobic segments in the product. In the above example, with the addition of 0.2 mol EO (ethylene oxide) and 20 g St (styrene), the corresponding m is 0.192 mol and n is 0.2 mol. It should be noted that m and n can also be other values, as long as they conform to the range of 1:(0.5~5) for the molar ratio of hydrophilic to hydrophobic segments specified in this application.

[0077] Thirdly, this application provides a solid-state battery, including the sulfide solid electrolyte with a coating layer as described above, or the sulfide solid electrolyte prepared by the preparation method of the sulfide solid electrolyte with a coating layer as described above.

[0078] The solid-state battery provided in this application uses a sulfide solid electrolyte with a coating layer. The hydrophilic and hydrophobic layers can suppress the hydrolysis and oxidation reactions of the sulfide electrolyte, improve the stability of the sulfide electrolyte, reduce the interfacial impedance between the positive electrode and the sulfide electrolyte, improve the cycle performance of the battery, and mitigate the capacity decay of the battery. At the same time, it can suppress the growth of lithium dendrites, alleviate the dissolution of In in the negative electrode active material Li-In alloy, block the interfacial side reactions between the sulfide electrolyte and the Li-In alloy, and improve the cycle life and energy density of the battery.

[0079] Solid-state batteries include lithium metal solid-state batteries.

[0080] Solid-state batteries include positive electrode sheets and negative electrode sheets. The positive electrode sheet includes positive electrode active materials, which include one or more of ternary materials, lithium cobalt oxide, and lithium iron phosphate. Ternary materials include uncoated ternary materials or ternary materials with a coating layer.

[0081] Ternary materials containing coatings include LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811) is pre-coated with LiTaO3 to form a LiTaO3 coating layer. Then, a polystyrene-ethylene oxide block copolymer is coated onto the surface of the LiTaO3 coating layer to reduce dependence on sulfide electrolytes. However, this coating structure increases process complexity. Preferably, the thickness of the LiTaO3 coating layer can be 2 nm.

[0082] The negative electrode sheet includes a negative electrode active material, which includes lithium metal or lithium alloy. Lithium alloy includes Li-In alloy.

[0083] Solid-state batteries also include solid electrolytes containing LiTFSI. The mass content of LiTFSI in the electrolyte is 1%, which can synergistically form a dynamic SEI layer with PSPEO.

[0084] The present invention will be further illustrated by the following examples.

[0085] Example 1 1) Preparation of sulfide solid electrolytes with coating layers S1: Preparation of polystyrene-ethylene oxide block copolymer; S11: Synthesis of PEO prepolymer (living anionic polymerization): The anionic ring-opening polymerization of EO was carried out in an argon-filled glove box. 0.044 mmol of compound 1 and 0.2 mol of EO, along with 40 mL of tetrahydrofuran, were added to a dry reactor. The reaction was carried out in a sealed reactor at 60°C for 24 hours. The polymerization was quenched with methanol. The resulting prepolymer was purified by dissolving it in chloroform and then precipitating it in petroleum ether, with a near-quantitative yield.

[0086] The structural formula of compound 1 is .

[0087] S12: Synthesis of SEO diblock copolymers (living radical polymerization): Add 5.0 g of the PEO prepolymer (molecular weight Mn approximately 200,000) obtained in step S11, 20.0 g of St, 0.1 g of AIBN, and 20 mL of toluene to a 100 mL L Schlenk flask. Stir the mixture at room temperature for 10 minutes. Then, degas the flask by performing three freeze-evacuation-thawing cycles. Afterward, stir the reaction mixture at 120°C for 15 hours under an argon atmosphere. The resulting product is purified by extraction with cold water and cyclohexane to remove unreacted PEO prepolymer and the generated PS homopolymer, yielding the final product, a polystyrene-ethylene oxide block copolymer.

[0088] In the obtained polystyrene-ethylene oxide block copolymer, the molecular weight of the polystyrene segment is 100,000 g / mol; the molecular weight of the polyethylene oxide segment is 50,000 g / mol; and the molar ratio of the polystyrene segment to the polyethylene oxide segment is 0.96:1.

[0089] S2: Preparation of sulfide solid electrolytes with coating layers S21: Polystyrene-ethylene oxide block copolymer was dissolved in toluene at 60℃ for 12 hours; then doped particles LiNbO3 and sulfide electrolyte Li were added. 5.5 PS 4.5 Cl 1.5 The mixture is thoroughly mixed to obtain the first mixed solution.

[0090] The total mass of the polystyrene-ethylene oxide block copolymer is m1, and the mass of the doped LiNbO3 particles is m2, with a m1:m2 ratio of 100:5. The mass ratio of the polystyrene-ethylene oxide block copolymer to the sulfide electrolyte is 1:30. The mass ratio of toluene to the polystyrene-ethylene oxide block copolymer is 50:1.

[0091] S22: The first mixed solution obtained in step S21 is heated and coated at a temperature of 80°C for 24 hours. After heating, a second mixed solution is obtained.

[0092] S23: The second mixed solution obtained in step S22 is dried for the first time at a first stage temperature T1 of 105℃ for 24 hours; after the first drying, it is dried for the second time at a second stage temperature T2 of 80℃ for 12 hours; after the second drying, it is dried for the third time at a third stage temperature T3 of 50℃ for 6 hours; after the third drying, a sulfide solid electrolyte with a coating layer is obtained.

[0093] Among them, the sulfide electrolyte Li in step S21 5.5 PS 4.5 Cl 1.5 The D50 particle size is in the range of 0.5~15μm; the thickness of the hydrophilic layer and the thickness of the hydrophobic layer in the sulfide solid electrolyte with coating layer prepared by step S23 are shown in Table 1.

[0094] Examples 2-8, Example 15 Examples 2-8, Example 15 and Example 1 have the same main steps, the difference is that the mass ratio of polystyrene-polyethylene oxide block copolymer and sulfide electrolyte added in step S21 is different, as shown in Table 1; the rest is the same as Example 1.

[0095] Example 9 Most of the steps in this embodiment are the same as those in Example 4, except that the polystyrene-ethylene oxide block copolymer prepared in step S1 has a molar ratio of polystyrene segments to ethylene oxide segments of 5:1; the rest are the same as in Example 1.

[0096] Example 10 Most of the steps in this embodiment are the same as those in Example 4, except that the polystyrene-ethylene oxide block copolymer prepared in step S1 has a molecular weight of 10,000 g / mol for the polystyrene segments and 5,000 g / mol for the ethylene oxide segments; the rest is the same as in Example 1.

[0097] Example 11 Most of the steps in this embodiment are the same as those in Example 4, except that the polystyrene-ethylene oxide block copolymer prepared in step S1 has a molecular weight of 1,000,000 g / mol for the polystyrene segments and 500,000 g / mol for the ethylene oxide segments; the rest is the same as in Example 1.

[0098] Example 12 Most of the steps in this embodiment are the same as those in Embodiment 4. The difference is that step S23 uses direct drying instead of a three-stage drying process. Step S23 in Embodiment 12 is as follows, and the rest are the same as those in Embodiment 1.

[0099] S23: The second mixed solution obtained in step S22 is dried at 105°C for 48 hours. After drying, a sulfide solid electrolyte with a coating layer is obtained.

[0100] Example 13 Most of the steps in this embodiment are the same as those in Embodiment 4, except that in step S21, there are no doped LiNbO3 particles.

[0101] Example 14 Most of the steps in this embodiment are the same as those in embodiment 4, except that in step S21, m1:m2 is 100:1.

[0102] Comparative Example 1 Comparative Example 1 directly uses sulfide electrolyte Li 5.5 PS 4.5 Cl 1.5 .

[0103] The sulfide solid electrolytes with coating layers prepared in the above embodiments and the sulfide electrolytes obtained in the comparative examples are used to prepare sulfide solid electrolytes, which are then assembled into lithium metal solid batteries. The preparation method of lithium metal solid batteries is as follows.

[0104] A1: Preparation of positive electrode powder: LiNi cathode material 0.8 Co 0.1 Mn 0.1 O2(NCM811), Li 5.5 PS 4.5Cl 1.5 The powders were mixed at a mass ratio of 7:3 to obtain the positive electrode powder.

[0105] A2: Preparation of the negative electrode sheet: Using In-coated metal and Li-Cu alloy as negative electrode plates A3: Preparation of sulfide solid electrolyte layer The sulfide solid electrolytes with coating layers prepared in the above embodiments are thoroughly mixed in a grinder to obtain electrolyte layer dry powder; similarly, the sulfide electrolytes are stirred evenly in a grinder to obtain sulfide electrolyte powder.

[0106] A4: Assembling Solid-State Batteries 1) Electrolyte tableting: Weigh 120 mg of the electrolyte layer dry powder or sulfide electrolyte powder obtained in step A3 into the mold battery sleeve and press it at 4.0 T for about 2 minutes to obtain the sulfide solid electrolyte layer.

[0107] 2) Positive electrode tableting: Weigh approximately 10 mg of the mixed positive electrode powder and spread it on top of the electrolyte layer for tableting. Then place a stainless steel foil as the current collector, press at 4.0T, and hold for about 2 minutes.

[0108] 3) Negative electrode pressing: Flip the mold battery sleeve and assemble it in the order of In and Li-Cu sheets (In metal is in contact with the solid electrolyte, and the Li of the Li-Cu sheet faces the In sheet), then press it at 1.0T and hold the pressure for about 2 minutes.

[0109] 4) Stainless steel mold pressure holding: Place the assembled battery into the external clamp, press with 0.5T, then tighten the screws, put it into the sealing cup to seal, and complete the final assembly. Before testing, the positive and negative terminals must not be short-circuited.

[0110] 5) After the mold battery is assembled, measure the EIS before cycling on the electrochemical workstation (the open-circuit voltage and impedance value need to be recorded. The same experimental system must be consistent, that is, the open-circuit voltage and EIS are basically the same). Performance testing 1) Measure the ionic conductivity of the electrolyte under the same exposure conditions. The sulfide solid electrolyte with a coating layer prepared in Example 4 and the sulfide electrolyte Li from Comparative Example 1 were used together. 5.5 PS 4.5 Cl 1.5 When exposed to the same humidity and dew point environment, its ionic conductivity and H2S gas release were tested. The specific test results are shown in Table 2.

[0111] 2) Test the interfacial impedance between the positive electrode and the sulfide electrolyte. The sulfide solid electrolyte with a coating layer prepared in Example 1 and the sulfide electrolyte Li from Comparative Example 1 were used.5.5 PS 4.5 Cl 1.5 The cathode material NCM811 was hand-ground into powder at a mass ratio of 3:7. The interfacial impedance was tested using electrochemical impedance spectroscopy (EIS, frequency range 0.1 Hz~1 MHz). The test results are shown in Table 3.

[0112] 3) The impedance, ionic conductivity, hydrophilic layer thickness, hydrophobic layer thickness, sulfide solid electrolyte thickness, and sulfide electrolyte thickness of the sulfide solid electrolyte prepared in the above embodiments and the sulfide electrolyte obtained in the comparative example were tested. The test results are shown in Table 1.

[0113] Battery performance test 4) Coulomb efficiency The battery was charged to 4.3V at a constant current and constant voltage of 0.5C, with a cutoff current of 0.005C. After full charge, the charging capacity C was recorded. 01 Then, it was discharged at a constant current of 0.5C, and the discharge capacity C was recorded. 02 .

[0114] Battery coulombic efficiency = C 02 / C 01 *100%.

[0115] 5) 25℃ ambient temperature circulation At 25℃, the battery is charged to 4.3V using a constant current and constant voltage of 1C, with a cutoff current of 0.005C. After full charging, it is discharged using a constant current of 1C, and the discharge capacity C1 is recorded. After 100 cycles of the above process, the discharge capacity C of the 100th battery is obtained. 100 .

[0116] 100-cycle capacity retention rate = C 100 / C1*100%.

[0117] The test results for battery performance are shown in Table 4.

[0118] 6) Mass energy density Based on the discharge capacity C1 obtained from the room temperature cycling test in section 5), the mass energy density = C1 / total battery mass. The test results are shown in Table 4.

[0119] Table 1 As shown in Table 1, comparing Examples 1-4, 15, and 5-8, when the mass ratio of polystyrene-polyethylene oxide block copolymer to sulfide electrolyte is in the range of 1:20 to 1:60, the resulting sulfide solid electrolyte with a coating layer has a hydrophilic layer thickness in the range of 3 to 15 nm and a hydrophobic layer thickness in the range of 3 to 15 nm. The ionic conductivity of the sulfide solid electrolyte is greater than 2 mS / cm.

[0120] Table 2 As shown in Table 2, the sulfide solid electrolyte with a coating layer prepared in Example 4, after being exposed to 10% RH for 24 hours, exhibited low ionic conductivity. In contrast, the sulfide solid electrolyte in Comparative Example 1 showed higher ionic conductivity under the same humidity and exposure time. This indicates that the hydrophobic segments in the hydrophobic layer of the sulfide solid electrolyte with the coating layer form a hydrophobic barrier (contact angle > 150°) that blocks water / oxygen penetration, inhibiting hydrolysis and oxidation reactions of the sulfide electrolyte. As a result, the ionic conductivity of the sulfide solid electrolyte remained > 2 mS / cm after exposure to 30% RH for 24 hours, and > 3 mS / cm after exposure to < 10% RH (compared to only 0.0001 mS / cm in the traditional process).

[0121] Table 3 Compared with Comparative Example 1, the sulfide solid electrolyte with a coating layer provided in this application has a hydrophilic layer covering the outer surface of the sulfide electrolyte. The hydrophilic layer contains hydrophilic segments that can react with water to generate LiOH, inhibiting the generation of HCl / PH3, blocking the "hydrolysis-oxidation" chain reaction, and preventing the oxidative decomposition of the sulfide electrolyte. The oxygen atoms contained in the hydrophilic segments can fill the oxygen vacancies on the surface of the cathode material (such as the high-nickel ternary cathode material NCM811). That is, the hydrophilic segments also repair the oxygen vacancies on the surface of NCM811 through dynamic Li⁺ coordination, preferentially reacting with H₂O to generate inert LiOH, blocking the generation of corrosive products such as Li₂SO₄, and reducing the interfacial impedance between the cathode material and the sulfide electrolyte (interfacial impedance from >200 Ω·cm). 2 Reduced to <50 Ω·cm 2 This technology can achieve a capacity retention rate of ≥84% after 100 cycles at a high voltage of 4.3 V, thus improving battery capacity degradation.

[0122] Table 4 Figure 1 The graph shows the discharge specific capacity and coulombic efficiency of the solid-state battery in Example 1 after 100 cycles. Figure 2 This is a 3000x scanning electron microscope image of the sulfide electrolyte in Comparative Example 1; Figure 2 In the image, a is the original image from a scanning electron microscope, b, c, and d are images from an energy dispersive spectrometer, b is a control image, c is the carbon distribution image, and d is the sulfur distribution image.

[0123] Figure 3 This is an 8000x scanning electron microscope image of the sulfide solid electrolyte with a coating layer prepared in Example 1; Figure 3 In the image, a is the original image from a scanning electron microscope, b and f are images from an energy dispersive spectroscopy (EDS) instrument, b is a control image, and cf are the distributions of carbon, phosphorus, chlorine, and sulfur, respectively.

[0124] As shown in Table 4, comparing Examples 1-4, Example 15, and Examples 5-8, the batteries obtained in Examples 5-8 exhibited low coulombic efficiency, low room-temperature cycle capacity retention, or low energy density. This indicates that a mass ratio of polystyrene-polyethylene oxide block copolymer to sulfide electrolyte within the range of 1:20 to 1:60 results in batteries with high room-temperature cycle capacity retention and high energy density. Further preferably, a mass ratio of polystyrene-polyethylene oxide block copolymer to sulfide electrolyte of 1:40 to 1:50 leads to even higher cycle capacity retention and energy density. The ionic conductivity values ​​of the sulfide solid electrolytes in Examples 1-14 in Table 1 are generally lower than those in Comparative Example 1. This is because the coated sulfide solid electrolyte, containing a polystyrene-polyethylene oxide block copolymer coating, reduces the overall ionic conductivity of the sulfide solid electrolyte, but significantly improves the cycle capacity retention and energy density of the battery.

[0125] Examples 4 and 9 demonstrate that a molar ratio of polystyrene segments to ethylene oxide segments in the polystyrene-polyethylene oxide block copolymer within the range of (0.5~5):1 can improve the cycle capacity retention, energy density, and coulombic efficiency of the battery. Examples 4 and 10-11 demonstrate that when the molecular weight of the hydrophobic segments is in the range of 10,000-1,000,000 g / mol and the molecular weight of the hydrophilic segments is in the range of 5,000-500,000 g / mol, the coating layer effectively reduces the interfacial impedance between the cathode material and the sulfide electrolyte, blocks interfacial side reactions between the sulfide electrolyte and the Li-In alloy, and improves the battery cycle life and energy density.

[0126] Comparing Example 1 and Comparative Example 1, the sulfide electrolyte in Comparative Example 1, which was not coated with a block copolymer, resulted in low coulombic efficiency, low cycle capacity retention, and low energy density. This demonstrates that the sulfide solid electrolyte with a coating layer provided in this application comprises a hydrophobic layer and a hydrophilic layer. The core is a sulfide electrolyte. The hydrophilic layer reduces the interfacial impedance between the cathode material and the sulfide electrolyte, improving battery cycle performance. The hydrophobic layer blocks moisture / oxygen permeation, inhibits hydrolysis and oxidation reactions of the sulfide electrolyte, and blocks interfacial side reactions between the sulfide electrolyte and the Li-In alloy. The hydrophilic and hydrophobic segments work synergistically to improve battery coulombic efficiency, cycle life, and energy density.

[0127] Comparing Example 4 and Example 12, Example 12 uses direct drying instead of a three-stage drying process. Direct drying may cause cracks in the hydrophilic and hydrophobic layers, resulting in poor battery cycle performance and low energy density. This shows that using a three-stage drying process is beneficial for forming a uniform coating structure on the surface of the sulfide electrolyte, improving the battery's cycle capacity retention and energy density, and enhancing battery performance.

[0128] Comparing Examples 4, 14, and 13, Example 13, which did not contain doped lithium niobate particles in its coating layer, exhibited slightly lower energy density and cycle capacity retention. This indicates that doping the coating layer with particles, and with m1:m2 in the range of 10:1 to 100:1, resulted in batteries with higher energy density and cycle capacity retention. Comparing Examples 13 and 4, Example 4 showed lower coulombic efficiency. This is presumably because lithium niobate primarily protects the positive electrode. However, the polystyrene-polyethylene oxide block copolymer also played a role in protecting the positive electrode, thus preventing the lithium niobate from fully realizing its potential.

[0129] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A sulfide solid electrolyte with a coating layer, characterized in that, The device includes a core and a coating layer. The coating layer is disposed on the outer surface of the core. The coating layer includes a hydrophobic layer and a hydrophilic layer. The core is a sulfide electrolyte. The hydrophilic layer is disposed on the outer surface of the core. The hydrophobic layer is disposed on the outer surface of the hydrophilic layer away from the core. The hydrophilic layer and the hydrophobic layer are connected by covalent bonds. The hydrophilic layer includes hydrophilic segments containing oxygen atoms. The hydrophobic layer includes hydrophobic segments.

2. The sulfide solid electrolyte with a coating layer according to claim 1, characterized in that, The thickness of the hydrophilic layer is greater than the thickness of the hydrophobic layer.

3. The sulfide solid electrolyte with a coating layer according to claim 1, characterized in that, The chemical formula of the sulfide electrolyte is Li x PS y Cl z , where 5 < x < 6, 4 < y < 5, and satisfies x + 5 = 2y + z; The hydrophobic segment includes one of a polystyrene segment and a polytetrafluoroethylene segment; the hydrophilic segment includes one of a polyethylene oxide segment and a polyethylene glycol segment.

4. The sulfide solid electrolyte with a coating layer according to claim 1, characterized in that, The thickness of the hydrophilic layer is 3~15nm, the thickness of the hydrophobic layer is 3~15nm, and the D50 particle size of the core is 0.5~15μm.

5. The sulfide solid electrolyte with a coating layer according to claim 1, characterized in that, The molar ratio of the hydrophilic segment to the hydrophobic segment is 1:(0.5~5).

6. The sulfide solid electrolyte with a coating layer according to claim 1, characterized in that, The coating layer further includes doped particles, which are lithium-containing compounds, including at least one of LiFSI, LiTFSI, LiDFOB, LiPF6, and lithium niobate. The total mass of the hydrophilic and hydrophobic segments is m1, and the mass of the doped particles is m2, where m1:m2 is 10:1 to 100:

1.

7. The method for preparing a sulfide solid electrolyte with a coating layer as described in any one of claims 1 to 6, characterized in that, Includes the following steps: Obtain a block copolymer containing the hydrophilic segment and the hydrophobic segment; The block copolymer, sulfide electrolyte, and organic solvent are mixed evenly to obtain a first mixed solution. The first mixed solution is heated, and after heating, it is dried to obtain the sulfide solid electrolyte with a coating layer.

8. The method for preparing a sulfide solid electrolyte with a coating layer according to claim 7, characterized in that, The mass ratio of the block copolymer to the sulfide electrolyte is 1:20 to 1:60; And / or, the organic solvent includes at least one of toluene, xylene, and chlorobenzene, and the mass ratio of the organic solvent to the block copolymer is 10:1 to 100:

1.

9. The method for preparing a sulfide solid electrolyte with a coating layer according to claim 7, characterized in that, The process of drying after heating to obtain the sulfide solid electrolyte with a coating includes the following steps: After heating, a second mixed solution is obtained. The second mixed solution is dried for the first time at a first stage temperature T1. After the first drying, it is dried for the second time at a second stage temperature T2. After the second drying, it is dried for the third time at a third stage temperature T3. T1 is 105~115℃, T2 is 70~90℃, and T3 is 40~60℃; The first drying time t1 is 12-24 hours; the second drying time t2 is 6-12 hours; and the third drying time t3 is 3-6 hours.

10. A solid-state battery, characterized in that, This includes the sulfide solid electrolyte with a coating layer as described in any one of claims 1 to 6, or the sulfide solid electrolyte with a coating layer prepared by the preparation method of the sulfide solid electrolyte with a coating layer as described in any one of claims 7 to 9.

Images