Sulfide solid electrolyte, preparation method thereof and all-solid-state battery

Abstract

The invention provides a sulfide solid electrolyte, a preparation method thereof and an all-solid-state battery, and relates to the field of all-solid-state battery preparation. The sulfide solid electrolyte comprises positive electrode particles, a chemical passivation core layer, an ion conduction gradient layer and a mechanical buffer layer, the chemical passivation core layer coats the positive electrode particles, the ion conduction gradient layer coats the chemical passivation core layer, and the mechanical buffer layer coats the ion conduction gradient layer; the chemical passivation core layer is an amorphous lithium phosphate layer; the ion conduction gradient layer comprises a lithium phosphate layer and a lithium thiophosphate layer; and the mechanical buffer layer is an argyrodite type sulfide solid electrolyte layer containing a nano whisker structure. The structure realizes continuous gradient transition of interface components, ionic conductivity and Young modulus, and synchronously solves the problems of chemical side reaction, space charge layer effect and mechanical contact failure.

Description

Technical Field

[0001] This application relates to the field of all-solid-state battery preparation, and more particularly to a sulfide solid electrolyte, its preparation method, and an all-solid-state battery. Background Technology

[0002] In solid-state battery development, the interfacial stability between sulfide solid electrolytes and cathode materials has long constrained performance improvement. Existing interface optimization strategies face multiple technical bottlenecks. While oxide artificial coatings can suppress the oxidative decomposition of sulfide electrolytes under high voltage conditions to some extent, their inherently low ionic conductivity severely hinders rapid lithium-ion migration, leading to a significant increase in internal resistance and deterioration in rate performance. Furthermore, these coatings exhibit rigidity due to their high Young's modulus. During battery cycling, repeated volume expansion and contraction of the cathode material cause stress accumulation within the coating, resulting in microcrack propagation and even interlayer delamination. This causes the interfacial impedance to continuously increase with the number of charge-discharge cycles, ultimately accelerating battery capacity decay. Sulfide composition gradient design methods attempt to mitigate oxidation by constructing a buffer layer with an outer layer of oxygen-rich sulfides. However, the oxygen doping depth is difficult to precisely control, often leading to abrupt rather than smooth transitions in the interfacial composition. These abrupt interfaces generate localized stress concentrations during electrochemical cycling, easily inducing structural failure. In addition, the ionic conductivity in high-oxygen-content regions drops sharply, failing to meet the ion transport efficiency requirements of high-power applications.

[0003] Some studies have introduced liquid or gel-like interfacial wetting layers to improve solid-solid interface contact. However, this approach inherently weakens the core safety advantage of all-solid-state batteries. Liquid components may cause leakage or thermal runaway risks, and their poor chemical compatibility with sulfide electrolytes can easily generate byproducts that further deteriorate interfacial properties. While mechanical pressing processes can temporarily increase the initial interfacial contact density, they cannot suppress the electrochemical side reactions that continue to occur during cycling, such as redox reactions between the positive electrode active material and the electrolyte. These reactions irreversibly consume active components and accumulate interfacial impedance.

[0004] Overall, existing technologies have failed to comprehensively address key requirements such as maintaining high ionic conductivity, ensuring interfacial chemical stability, achieving continuous potential matching, and adapting to mechanical flexibility. Particularly during long-term battery cycling, the lack of effective in-situ repair mechanisms for dynamic interfacial degradation leads to continuous degradation of interfacial performance. Therefore, existing technologies urgently need improvement to address these issues. Summary of the Invention

[0005] The purpose of this application is to provide a sulfide solid electrolyte, a method for preparing the same, and an all-solid-state battery to solve the above-mentioned problems.

[0006] To achieve the above objectives, this application adopts the following technical solution: This application provides a sulfide solid electrolyte, comprising: positive electrode particles, a chemical passivation core layer, an ion conduction gradient layer, and a mechanical buffer layer; The chemical passivation core layer covers the positive electrode particles, the ion conduction gradient layer covers the chemical passivation core layer, and the mechanical buffer layer covers the ion conduction gradient layer; The chemical passivation core layer is amorphous lithium phosphate; The ion-conducting gradient layer transitions from lithium phosphate to lithium thiophosphate along the direction from the chemically passivated core layer to the mechanical buffer layer. The mechanical buffer layer includes a sulfide solid electrolyte containing a sulfide-silver germanite structure.

[0007] Optionally, the thickness of the chemical passivation core layer is no greater than 5 nm.

[0008] Optionally, the material of the mechanical buffer layer includes a sulfide-silver-germanium mineral phase Li6PS5Cl with a nanocrystal whisker structure.

[0009] Optionally, the nanowhiskers have a diameter of 10-100 nm and a length of 0.5-2 μm.

[0010] This application also provides a method for preparing a sulfide solid electrolyte, comprising: A chemical passivation core layer is formed on the surface of positive electrode active material particles by solution dip coating. An ion-conducting gradient layer is formed on the outer surface of the chemically passivated core layer by chemical vapor deposition. A mechanical buffer layer is formed on the outer surface of the ion-conducting gradient layer by self-assembly and cold pressing processes. The sulfide solid electrolyte is obtained by mixing particles having the chemical passivation core layer, the ion conduction gradient layer, and the mechanical buffer layer with an oxidation-triggered lithium source and a phosphorus-sulfur precursor.

[0011] Optionally, the preparation process of the chemical passivation core layer includes: immersing positive electrode active material particles in an alcohol solution containing phosphate source and lithium source, reacting at 60-90°C, and sequentially centrifuging, washing, and drying to form an amorphous lithium phosphate passivation core layer; The phosphate source includes diammonium hydrogen phosphate; the lithium source includes lithium hydroxide.

[0012] Optionally, the preparation process of the ion-conducting gradient layer includes: depositing particles with the chemical passivation core layer at 100-200°C in a mixed gas atmosphere; The mixed gas includes PH3, H2S and Ar; the concentration of PH3 increases linearly from 0% to 20-40% over time, forming a gradient layer with a composition that gradually changes from lithium phosphate to lithium thiophosphate.

[0013] Optionally, the preparation process of the mechanical buffer layer includes: immersing particles having the ion conduction gradient layer into a colloidal dispersion containing sulfur-silver-germanium mineral phase electrolyte nanocrystals, drying them, and then performing cold pressing treatment under a pressure of 100-200 MPa.

[0014] Optionally, the oxidation-triggered lithium source includes Li2S2O4; the phosphorus-sulfur precursor includes P2S5 microcapsules.

[0015] This application also provides an all-solid-state battery, including the positive electrode active material with the gradient heterostructure interface structure.

[0016] Compared with the prior art, the beneficial effects of this application include: The sulfide solid electrolyte provided in this application employs a gradient heterogeneous interface structure design. Between the positive electrode active particles and the sulfide solid electrolyte, a three-dimensional heterogeneous structure is constructed, consisting of a chemical passivation core, a gradient ion-conducting layer composed of lithium phosphate and lithium thiophosphate layers, and a flexible sulfide-silver-germanium phase nanocrystal buffer layer, arranged sequentially from the inside out. This structure achieves a continuous gradient transition in interface composition, ionic conductivity, and Young's modulus, simultaneously addressing issues such as chemical side reactions, space charge layer effects, and mechanical contact failures. Furthermore, when localized high pressure at the interface causes microcracks in the passivation layer during cycling, the exposed sulfide triggers an additive reaction, generating a repair phase with lithium-ion conductivity in situ, enabling dynamic self-healing of interface damage. Detailed Implementation

[0017] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0018] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0019] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0020] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0021] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0022] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0023] To better explain the technical solution provided in this application, the technical solution provided in this application will be described in general before the specific implementation.

[0024] In a first aspect, this application provides a sulfide solid electrolyte, comprising: positive electrode particles, a chemical passivation core layer, an ion conduction gradient layer, and a mechanical buffer layer; The chemical passivation core layer covers the positive electrode particles, the ion conduction gradient layer covers the chemical passivation core layer, and the mechanical buffer layer covers the ion conduction gradient layer; The chemical passivation core layer is amorphous lithium phosphate; The ion-conducting gradient layer transitions from lithium phosphate to lithium thiophosphate; wherein, the composition of the ion-conducting gradient layer transitions continuously from lithium phosphate in the inner layer, through the intermediate lithium phosphate-lithium thiophosphate eutectic phase, to lithium thiophosphate in the outer layer. The mechanical buffer layer includes a sulfide solid electrolyte containing a sulfide-silver germanite structure.

[0025] It is understandable that the following layer-by-layer construction is performed on the surface of the cathode particle (such as NCM811): chemical passivation core: ultrathin (<5nm) amorphous Li3PO4 layer (ionic conductivity 10). -7 S / cm), stabilizing interfacial oxygen through strong PO bonds; ion-conducting gradient layer: from the inside out, the composition gradually changes from Li3PO4 to Li3PS4 (ionic conductivity 10). -4 The continuous transition between Li3PO4 (high oxidation stability), Li3PO4-Li3PS4 eutectic, and Li3PS4 is achieved through a mechanical buffer layer: the outermost layer is a flexible silver-sulfur germanium mineral phase Li6PS5Cl (ionic conductivity >10mS / cm), whose nanocrystal structure provides elasticity.

[0026] In one optional implementation, the thickness of the chemical passivation core layer is no greater than 5 nm.

[0027] Optionally, the thickness of the chemical passivation core layer can be 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, or any value not greater than 5 nm.

[0028] In an alternative embodiment, the material of the mechanical buffer layer comprises a sulfide-silver-germanium mineral phase Li6PS5Cl with a nanofiber structure.

[0029] In one optional embodiment, the nanowhiskers have a diameter of 10-100 nm and a length of 0.5-2 μm.

[0030] Optionally, the diameter of the nanowhiskers can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value between 10 and 100 nm; the length of the nanowhiskers can be 0.5 μm, 1 μm, 1.5 μm, 2 μm, or any value between 0.5 and 2 μm.

[0031] Secondly, this application also provides a method for preparing a sulfide solid electrolyte, comprising: A chemical passivation core layer is formed on the surface of positive electrode active material particles by solution dip coating. An ion-conducting gradient layer is formed on the outer surface of the chemically passivated core layer by chemical vapor deposition. A mechanical buffer layer is formed on the outer surface of the ion-conducting gradient layer by self-assembly and cold pressing processes. The sulfide solid electrolyte is obtained by mixing particles having the chemical passivation core layer, the ion conduction gradient layer, and the mechanical buffer layer with an oxidation-triggered lithium source and a phosphorus-sulfur precursor.

[0032] In an optional embodiment, the preparation process of the chemical passivation core layer includes: immersing positive electrode active material particles in an alcohol solution containing phosphate source and lithium source, reacting at 60-90°C, and sequentially centrifuging, washing, and drying to form an amorphous lithium phosphate passivation core layer; The phosphate source includes diammonium hydrogen phosphate; the lithium source includes lithium hydroxide.

[0033] Optionally, during the preparation of the chemical passivation core layer, the reaction temperature can be 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, or any value between 60℃ and 90℃.

[0034] In an optional embodiment, the preparation process of the ion-conducting gradient layer includes: depositing particles having the chemically passivated core layer in a mixed gas atmosphere at 100-200°C. The mixed gas includes PH3, H2S and Ar; the concentration of PH3 increases linearly from 0% to 20-40% over time, forming a gradient layer with a composition that gradually changes from lithium phosphate to lithium thiophosphate.

[0035] Optionally, during the preparation of the ion-conducting gradient layer, the reaction temperature of the deposition reaction can be 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, or any value between 100℃ and 200℃.

[0036] Optionally, the preparation process of the mechanical buffer layer includes: immersing particles having the ion conduction gradient layer into a colloidal dispersion containing sulfur-silver-germanium mineral phase electrolyte nanocrystals, drying, and then performing cold pressing treatment under a pressure of 100-200 MPa.

[0037] In an optional embodiment, the oxidation-triggered lithium source comprises Li2S2O4; and the phosphorus-sulfur precursor comprises P2S5 microcapsules.

[0038] This application also provides an all-solid-state battery, including the positive electrode active material with the gradient heterostructure interface structure.

[0039] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0040] Example 1 This embodiment provides a sulfide solid electrolyte: The positive electrode particles are coated with a chemical passivation core layer, the chemical passivation core layer is coated with an ion conduction gradient layer, and the ion conduction gradient layer is coated with a mechanical buffer layer.

[0041] The positive electrode particles are commercially available NCM811 with D50=5μm.

[0042] The chemical passivation core layer is amorphous lithium phosphate (Li3PO4).

[0043] The ion conduction gradient layer transitions from lithium phosphate to lithium thiophosphate (Li3PO4→Li3PS4).

[0044] The mechanical buffer layer is a Li6PS5Cl nanocrystal composite material of sulfide-germanium ore type; the nanocrystals have a diameter of 50 nm and a length of 1 μm.

[0045] This application also provides a method for preparing a sulfide solid electrolyte, the specific steps of which are as follows: Cathode particle pretreatment: Commercial NCM811 was air annealed at 600℃ for 2 hours to remove surface lithium impurities.

[0046] Gradient interface construction: Chemical passivation of the core layer (Li3PO4 core layer): NCM811 was immersed in a 0.1M (NH4)2HPO4 and 0.15M LiOH ethanol solution, stirred at 80℃ for 2h, centrifuged, washed and dried.

[0047] Ion-conducting gradient layer (Li3PO4-Li3PS4 gradient layer): The above particles are placed in a fluidized bed and PH3 / H2S / Ar is introduced (PH3 concentration increases linearly from 0% to 30%), and the reaction is carried out at 150℃ for 1 hour.

[0048] Mechanical buffer layer (Li6PS5Cl): The particles were immersed in acetonitrile colloid (10wt%) containing Li6PS5Cl nanocrystals (50nm in diameter and 1μm in length), dried, and then cold-pressed at 150MPa for 10s.

[0049] Electrolyte and additive compounding: Li6PS5Cl powder was ball-milled and mixed with 2wt% bifunctional additive (Li2S2O4 and P2S5 microcapsules 1:1).

[0050] This embodiment also provides an all-solid-state battery: All-solid-state battery assembly: positive electrode (interface modified NCM811:Li6PS5Cl:CNT=70:25:5), composite electrolyte layer, lithium indium negative electrode, cold-pressed at 300MPa.

[0051] Performance testing: 25℃ test: EIS measurement of interface impedance; 0.5C cycling (3.0-4.3V); constant voltage 4.5V for 24h to measure leakage current; d) XPS / TOF-SIMS analysis of interface composition after disassembly.

[0052] Comparative Example 1 This comparative example provides a sulfide solid electrolyte, which differs from Example 1 in that the outermost mechanical buffer layer (i.e., the Li6PS5Cl buffer layer) is omitted, while the other parameters are the same as in Example 1.

[0053] Comparative Example 2 This comparative example provides a sulfide solid electrolyte with the same structure as Example 1. The difference from Example 1 is that in the preparation method, the electrolyte and additive composite step only uses Li2S2O4 (1wt%) without adding P2S5 microcapsules. The remaining steps and parameters are the same as in Example 1.

[0054] Comparative Example 3 This comparative example provides a sulfide solid electrolyte. Unlike Example 1, the positive electrode particles NCM811 are in direct contact with the Li6PS5Cl electrolyte. The remaining steps and parameters are the same as in Example 1.

[0055] Comparative Example 4 This comparative example provides a solid electrolyte with an interface structure using existing technology, specifically by depositing a 5nm LiNbO3 coating using ALD without adding any additives. The testing method is the same as in Example 1.

[0056] Comparative Example 5 This comparative example provides a solid electrolyte with no independent interface layer, using Li6PS5Cl and Li... 3.2 P 0.8 O 0.2 S 3.8 Gradient electrolyte (outer layer to inner layer oxygen doping 0→20at%), no additives added, test method is the same as in Example 1.

[0057] The electrical performance of the all-solid-state batteries provided in the examples and comparative examples is shown in Table 1.

[0058] Table 1 Comparison of Electrical Performance

[0059] As can be seen from Table 1, the technical solution provided in this application (Example 1) exhibits an ultra-low initial interface impedance (8.2 Ω·cm). 2 Excellent high-voltage stability (leakage current 0.15 μA / cm) 2It also boasts an ultra-long cycle life (92.5% retention after 500 cycles). This is attributed to: a) the gradient heterostructure completely blocks oxidation side reactions and eliminates the space charge layer; b) the buffer layer absorbs mechanical stress; and c) the bifunctional additive enables in-situ repair. In-situ repair experiments further validate its dynamic maintenance capabilities.

[0060] In Comparative Example 1, the lack of an outer buffer layer led to a significant deterioration of physical contact during cycling (86% retention rate), demonstrating the crucial role of the mechanical buffer layer in maintaining long-term contact.

[0061] In Comparative Example 2, a single lithium source additive could not generate an effective repair phase (retention rate of 82.5%), verifying the necessity of Li2S2O4 / P2S5 synergistic generation of Li3PS4.

[0062] In Comparative Examples 3-6, the untreated interface suffered severe failure; the LiNbO3 coating's performance was limited due to its high impedance and brittleness; although the composition gradient electrolyte was superior to the untreated group, it suffered a large loss in ionic conductivity and had no repair capability.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0064] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A sulfide solid electrolyte, characterized in that, include: Positive electrode particles, chemical passivation core layer, ion conduction gradient layer, and mechanical buffer layer; The chemical passivation core layer covers the positive electrode particles, the ion conduction gradient layer covers the chemical passivation core layer, and the mechanical buffer layer covers the ion conduction gradient layer; The chemical passivation core layer is amorphous lithium phosphate; The ion-conducting gradient layer transitions from lithium phosphate gradient to lithium thiophosphate along the direction from the chemically passivated core layer to the mechanical buffer layer; The mechanical buffer layer includes a sulfide solid electrolyte containing a sulfide-silver germanite structure.

2. The sulfide solid electrolyte according to claim 1, characterized in that, The thickness of the chemical passivation core layer is no greater than 5 nm.

3. The sulfide solid electrolyte according to claim 1, characterized in that, The material of the mechanical buffer layer includes a sulfosilver germanium phase Li6PS5Cl with a nanocrystal whisker structure.

4. The sulfide solid electrolyte according to claim 3, characterized in that, The nanocrystals have a diameter of 10-100 nm and a length of 0.5-2 μm.

5. A method for preparing the sulfide solid electrolyte according to claim 1, characterized in that, include: A chemical passivation core layer is formed on the surface of positive electrode active material particles by solution dip coating. An ion-conducting gradient layer is formed on the outer surface of the chemically passivated core layer by chemical vapor deposition. A mechanical buffer layer is formed on the outer surface of the ion-conducting gradient layer by self-assembly and cold pressing processes. The sulfide solid electrolyte is obtained by mixing particles having the chemical passivation core layer, the ion conduction gradient layer, and the mechanical buffer layer with an oxidation-triggered lithium source and a phosphorus-sulfur precursor.

6. The method for preparing the sulfide solid electrolyte according to claim 5, characterized in that, The preparation process of the chemical passivation core layer includes: immersing positive electrode active material particles in an alcohol solution containing phosphate source and lithium source, reacting at 60-90℃, and then centrifuging, washing and drying in sequence to form an amorphous lithium phosphate passivation core layer; The phosphate source includes diammonium hydrogen phosphate; the lithium source includes lithium hydroxide.

7. The method for preparing the sulfide solid electrolyte according to claim 5, characterized in that, The preparation process of the ion-conducting gradient layer includes: depositing particles with the chemical passivation core layer at 100-200°C in a mixed gas atmosphere; The mixed gas includes PH3, H2S and Ar; the concentration of PH3 increases linearly from 0% to 20-40% over time, forming a gradient layer with a composition that gradually changes from lithium phosphate to lithium thiophosphate.

8. The method for preparing the sulfide solid electrolyte according to claim 5, characterized in that, The preparation process of the mechanical buffer layer includes: immersing particles with the ion conduction gradient layer into a colloidal dispersion containing sulfur-silver-germanium mineral phase electrolyte nanocrystals, drying them, and then cold-pressing them under a pressure of 100-200 MPa.

9. The method for preparing the sulfide solid electrolyte according to claim 5, characterized in that, The oxidation-triggered lithium source includes Li2S2O4; the phosphorus-sulfur precursor includes P2S5 microcapsules.

10. An all-solid-state battery, characterized in that, The positive electrode active material includes the gradient heterogeneous interface structure as described in any one of claims 1-4.

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