Positive electrode material, preparation method thereof and sulfide solid-state battery

Abstract

The invention discloses a positive electrode material, a preparation method thereof and a sulfide solid-state battery, and relates to the technical field of sulfide solid-state batteries. The positive electrode material provided by the invention comprises the ternary positive electrode material matrix and the Li2O-Li3PS4 composite layer coated on the ternary positive electrode material matrix, an interface-stable lithium compensation structure can be formed, and the coating layer can prevent the ternary positive electrode material from directly contacting with sulfide solid electrolyte (such as Li6PS5Cl); and the coating layer is stable for the ternary positive electrode material and the sulfide solid electrolyte at the same time, can inhibit the formation of interface side reaction and high-impedance by-products, is beneficial to exerting the battery capacity, and improves the rate and the cycle performance.

Description

Technical Field

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

[0002] The interface of high voltage cathode materials (such as NCM, lithium-rich manganese-based, etc.) is relatively unstable under high voltage, and it is easy to form high-valent Ni 4+ Sulfide solid electrolytes easily react with the positive electrode and release free oxygen, causing structural damage and failure, and there are serious problems with interfacial side reactions. Due to the difference in the interface characteristics of the positive electrode and the lithium supplement, the sulfide solid electrolyte is not compatible with them at the same time, and the battery has difficulty in achieving ideal electrical performance. Currently, the problem of low first cycle efficiency (<80%) of solid-state batteries has not been effectively solved.

[0003] Therefore, there is an urgent need to optimize the structure of high-voltage positive electrode materials to reduce the problem of interfacial side reactions and improve the cycle performance of batteries.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a positive electrode material and a preparation method thereof and a sulfide solid-state battery, aiming to improve the stability of the interface between the positive electrode and the sulfide solid electrolyte and enhance the electrochemical performance of the battery.

[0006] The present invention is achieved in that:

[0007] In a first aspect, the present invention provides a positive electrode material, comprising a ternary positive electrode material matrix and a coating layer coated on the ternary positive electrode material matrix, wherein the coating layer is a Li2O-Li3PS4 composite layer.

[0008] In an optional embodiment, the general formula of the ternary cathode material matrix is ​​LiNi 1-x-y Co x Mn y O2, 0.01≤x≤0.3, 0.01≤y≤0.3;

[0009] Preferably, the ternary cathode material matrix is ​​NCM811;

[0010] Preferably, in the coating layer, the molar ratio of Li2O and Li3PS4 is (2.5-3.5):1;

[0011] Preferably, the particle size D50 of the ternary positive electrode material matrix is ​​3 μm-15 μm, and the thickness of the coating layer is 50 nm-200 nm.

[0012] In a second aspect, the present invention provides a method for preparing the positive electrode material of the aforementioned embodiment, comprising: alternately depositing LiOH and P2S5 on the surface of a ternary positive electrode material by an atomic layer deposition method to obtain a precursor material;

[0013] The precursor material is heat-treated to form a coating layer.

[0014] In an optional embodiment, the process of preparing the precursor material includes: dissolving LiOH and a solvent, and atomizing the obtained LiOH solution through a carrier gas and delivering it as a LiOH pulse source;

[0015] P2S5 is heated and sublimated in an ALD reaction chamber to supply P2S5 gas;

[0016] Using the ternary cathode material as the substrate, it is heated to 150-200°C, and a LiOH pulse source is introduced to form nucleation sites, followed by alternating LiOH pulse sources and P2S5 gas.

[0017] Preferably, the pulse time is adjusted to control the molar ratio of Li2O and P2S5 to be (2.5-3.5):1.

[0018] In an optional embodiment, during the preparation of the LiOH pulse source, the solvent used is selected from at least one of methanol, ethanol, ethylene glycol, isopropanol and tetrahydrofuran, and the concentration of the LiOH solution is 0.005 mol / L-0.05 mol / L.

[0019] In an optional embodiment, the preparation process of P2S5 gas includes: heating P2S5 to 155° C.-170° C. in an ALD reaction chamber, and adjusting the pressure of the reaction chamber to 0.1 Torr-0.5 Torr.

[0020] In an optional embodiment, the ternary cathode material is dried and plasma cleaned before depositing LiOH and P2S5;

[0021] Preferably, the drying temperature is controlled to be 110°C-130°C, and the drying time is 10h-15h;

[0022] Preferably, argon plasma is used during the plasma cleaning process.

[0023] In an optional embodiment, the process of alternately introducing a LiOH pulse source and P2S5 gas comprises:

[0024] A LiOH pulse source is introduced, with a flow rate of 40 sccm-60 sccm and a pulse time of 0.05 s-0.15 s. After the LiOH pulse source is introduced, an inert gas is used for purge, with a gas flow rate of 80 sccm-120 sccm and a purge time of 20 s-40 s.

[0025] P2S5 gas is introduced, and the gas flow rate is controlled to be 40sccm-60sccm, and the pulse time is 0.1s-0.3s. After the P2S5 gas is introduced, it is purged with inert gas, and the gas flow rate is controlled to be 80sccm-120sccm, and the purge time is 40s-80s.

[0026] The process is repeated 50 to 200 times to make the thickness of the coating layer reach 50 nm to 200 nm.

[0027] In an optional embodiment, the heat treatment process includes: heat treating the precursor material at 280° C.-320° C. for 1 h-3 h;

[0028] Preferably, the heating rate is controlled to be 4°C / min-6°C / min;

[0029] Preferably, the heat treatment is performed under an inert atmosphere.

[0030] In a third aspect, the present invention provides a sulfide solid-state battery, comprising the positive electrode material of any one of the aforementioned embodiments or the positive electrode material prepared by any one of the preparation methods of the aforementioned embodiments.

[0031] The present invention has the following beneficial effects: the positive electrode material provided by the present invention includes a ternary positive electrode material matrix and a Li2O-Li3PS4 composite layer coated on the ternary positive electrode material matrix, which can form an interface-stabilized lithium compensation structure. The coating layer can prevent direct contact between the ternary positive electrode material and the sulfide solid electrolyte (such as Li6PS5Cl), and the coating layer can stabilize the ternary positive electrode material and the sulfide solid electrolyte at the same time, and can inhibit the formation of interfacial side reactions and high-impedance by-products, which is beneficial to the battery capacity and improves the rate and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 A diagram illustrating the preparation process of the composite positive electrode provided in an embodiment of the present invention.

[0034] Figure 2 This is the X-ray diffraction pattern of the composite positive electrode provided by an embodiment of the present invention.

[0035] Figure 3The first cycle charge and discharge test comparison curves of Example 1, Comparative Examples 1 and 2 are shown.

[0036] Figure 4 The graph is a comparison curve of the cycle capacity retention rate test between Example 1, Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0037] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, all are conventional products that can be purchased commercially.

[0038] An embodiment of the present invention provides a positive electrode material, including a ternary positive electrode material matrix and a coating layer coated on the ternary positive electrode material matrix, wherein the coating layer is a Li2O-Li3PS4 composite layer, which can form an interface-stable lithium compensation structure, which is beneficial to suppressing interface side reactions.

[0039] In some embodiments, the general formula of the ternary cathode material matrix is ​​LiNi 1-x-y Co x Mn y O2, 0.01≤x≤0.3, 0.01≤y≤0.3. Ternary cathode materials that satisfy the above general formula are suitable for forming an interfacially stable lithium compensation structure by introducing a Li2O-Li3PS4 composite layer. In a preferred embodiment, the ternary cathode material matrix is ​​NCM811, which is readily available and has excellent performance.

[0040] In some embodiments, the coating layer has a thickness of 50 nm to 200 nm, such as 50 nm, 80 nm, 100 nm, 130 nm, 150 nm, 180 nm, 200 nm, etc.

[0041] The present invention provides a method for preparing a positive electrode material, wherein a Li2O-Li3PS4 composite layer is prepared by atomic layer deposition, and the steps are as follows:

[0042] S1. Prepare materials

[0043] Prepare ternary cathode materials and a pulse source for atomic layer deposition: the ternary cathode material can be a commercially available material, such as NCM811, and the particle size D50 of the ternary cathode material is 3μm-15μm, single crystal or polycrystalline; the pulse source for atomic layer deposition includes a LiOH pulse source and P2S5 gas, which are used to pass into the atomic layer deposition reaction chamber for deposition.

[0044] In some embodiments, LiOH and a solvent are dissolved, and the resulting LiOH solution is atomized and delivered via a carrier gas to serve as a LiOH pulse source. The type of solvent is not limited, and the solvent used can be selected from at least one of methanol, ethanol, ethylene glycol, isopropanol, and tetrahydrofuran, or any one or more of the above. The concentration of the LiOH solution is 0.005 mol / L to 0.05 mol / L, such as 0.005 mol / L, 0.01 mol / L, 0.025 mol / L, 0.035 mol / L, 0.05 mol / L, and the like.

[0045] In some embodiments, P2S5 is independently heated and sublimated in an ALD reaction chamber to supply P2S5 gas. In actual operation, the preparation process of P2S5 gas includes: heating P2S5 in an ALD reaction chamber to 155°C-170°C (e.g., 155°C, 160°C, 165°C, 170°C, etc.), adjusting the reaction chamber pressure to 0.1 Torr-0.5 Torr (e.g., 0.1 Torr, 0.2 Torr, 0.3 Torr, 0.4 Torr, 0.5 Torr, etc.), and ensuring gaseous sublimation under low pressure conditions to ensure a stable supply of P2S5.

[0046] In some embodiments, before depositing LiOH and P2S5, the ternary cathode material is first dried and plasma cleaned. By drying and plasma cleaning, surface impurities can be fully removed and the coating effect can be improved. During drying, the drying temperature is controlled to be 110°C-130°C, such as 110°C, 115°C, 120°C, 125°C, 130°C, etc.; the drying time is 10h-15h, such as 10h, 11h, 12h, 13h, 14h, 15h, etc. During the plasma cleaning process, argon plasma is used, and the operating parameters are not limited, such as the power can be about 50W and the cleaning time can be about 5min.

[0047] S2. Preparation of precursor materials by atomic layer deposition

[0048] LiOH and P2S5 are alternately deposited on the surface of the ternary cathode material to obtain a precursor material, and a uniform coating layer is formed by atomic layer deposition.

[0049] In some embodiments, a ternary cathode material is used as a substrate and heated to 150°C-200°C (e.g., 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, etc.), and a LiOH pulse source is introduced once to form nucleation sites. Subsequently, LiOH pulses and P2S5 gas are introduced alternately. By first using the LiOH pulse source to form nucleation sites, uniformly distributed nucleation sites can be pre-formed on the material surface, guiding the subsequent coating material precursor to preferentially deposit and grow at these sites, thereby improving the uniformity and density of the coating layer.

[0050] Furthermore, the process of alternately introducing a LiOH pulse source and a P2S5 gas includes: (a) introducing an atomized LiOH pulse source, controlling the flow rate to be 40sccm-60sccm, and the pulse time to be 0.05s-0.15s; (b) purging with an inert gas, controlling the gas flow rate to be 80sccm-120sccm, and the purge time to be 20s-40s; (c) introducing P2S5 gas, controlling the gas flow rate to be 40sccm-60sccm, and the pulse time to be 0.1s-0.3s; (d) after the introduction of the P2S5 gas, purging with an inert gas, controlling the gas flow rate to be 80sccm-120sccm, and the purge time to be 40s-80s. Steps (a)-(d) are one cycle, which is repeated 50-200 times to make the coating layer have a thickness of 50nm-200nm.

[0051] Specifically, when the atomized LiOH pulse source is introduced in step (a), the controlled gas flow rate can be 40 sccm, 50 sccm, 60 sccm, etc.; the pulse time can be 0.05 s, 0.10 s, 0.15 s, etc. When the inert gas is used for purging in step (b), the controlled gas flow rate can be 80 sccm, 90 sccm, 100 sccm, 110 sccm, 120 sccm, etc., and the purge time can be 20 s, 30 s, 40 s, etc. When the P2S5 gas is introduced in step (c), the controlled gas flow rate can be 40 sccm, 50 sccm, 60 sccm, etc.; the pulse time can be 0.1 s, 0.2 s, 0.3 s, etc. When the inert gas is used for purging in step (d), the controlled gas flow rate can be 80 sccm, 90 sccm, 100 sccm, 110 sccm, 120 sccm, etc., and the purge time can be 40 s, 60 s, 80 s, etc. The number of cycles can be 50, 80, 100, 120, 150, 180, 200, etc., and the thickness of the coating layer can be 50 nm, 80 nm, 100 nm, 130 nm, 150 nm, 180 nm, 200 nm, etc. After the cycle is completed, it is cooled to room temperature to obtain a precursor material (such as NCM811 coated with LiOH-P2S5).

[0052] In a preferred embodiment, the pulse time is adjusted to control the molar ratio of Li2O and P2S5 to be (2.5-3.5):1, such as 2.5:1, 2.8:1, 3.0:1, 3.2:1, 3.5:1, etc. Excessive Li2O will increase Li2S impurities, and insufficient Li2O will result in unreacted P2S5 residues.

[0053] S3. Heat treatment

[0054] The precursor material is heat treated to form a coating layer. During the heat treatment, the following reactions occur:

[0055]

[0056] 3Li2O+P2S5→2Li3PS4;

[0057] It should be noted that the O in Li2O 2- Partially replaces the S in P2S5 2- , forming lithium thiophosphate, and then obtaining a Li2O-Li3PS4 coating layer.

[0058] In some embodiments, the heat treatment process includes: heat treating the precursor material at 280°C-320°C for 1h-3h to fully react P2S5. In actual operation, the temperature is raised to the heat treatment temperature at a heating rate of 4°C / min-6°C / min, and the heat treatment is carried out under an inert atmosphere (such as argon). Specifically, the heat treatment temperature can be 280°C, 290°C, 300°C, 310°C, 320°C, etc.; the heat treatment time can be 1h, 2h, 3h, etc., and then cooled to room temperature; when the temperature is raised to the heat treatment temperature, the heating rate can be controlled to be 4°C / min, 5°C / min, 6°C / min, etc.

[0059] The present invention also provides a sulfide solid-state battery, comprising a cathode material according to the present invention. This cathode material is used to prepare a cathode layer, which, in combination with an electrolyte layer and a cathode, forms a solid-state battery. Optimizing the cathode material facilitates forming a more stable interface with the electrolyte layer, thereby improving the battery's electrochemical performance.

[0060] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0061] Example 1

[0062] This embodiment provides a method for preparing a positive electrode material, the steps of which are as follows:

[0063] (1) Prepare ingredients

[0064] LiOH was dissolved in ethanol to prepare a 0.025 M solution, which was atomized and delivered by carrier gas argon as a pulse source.

[0065] P2S5 is independently heated to 160°C in the ALD reaction chamber, and the reaction chamber cavity pressure is adjusted to a low pressure of 0.5 Torr to ensure a stable supply of gaseous sublimated P2S5.

[0066] NCM811 (D50=4 μm, single crystal) was vacuum dried at 120° C. for 12 h, and then cleaned with argon plasma (power 50 W, 5 min) to remove surface impurities.

[0067] (2) Preparation of precursor materials by atomic layer deposition

[0068] NCM811 was used as a substrate and heated to 200 °C. A LiOH pulse source was pulsed once (gas flow rate 50 sccm, pulse 0.1 s) to form nucleation sites.

[0069] Alternating deposition cycles: (a) atomized LiOH pulse source, gas flow rate 50 sccm, pulse 0.2s; (b) argon purge, gas flow rate 100 sccm, purge 30s; (c) P2S5 gas, gas flow rate 50 sccm, pulse 0.1s; (d) argon purge, gas flow rate 100 sccm, purge 60s. Steps (a) to (d) constitute one cycle, and 100 cycles were repeated to achieve a coating thickness of 10nm.

[0070] Cooling gave LiOH-P2S5 coated NCM811.

[0071] In this embodiment, the molar ratio of Li2O and P2S5 is controlled to be 3:1 by adjusting the pulse time.

[0072] (3) Heat treatment

[0073] The LiOH-P2S5-coated NCM811 was placed in an argon environment, heated to 300°C at a rate of 5°C / min, and then maintained at 300°C for 2h; cooled to room temperature to obtain NCM811@Li2O-Li3PS4.

[0074] Example 2

[0075] The only difference from Example 1 is that the parameters of step (2) are different, as follows:

[0076] NCM811 was used as a substrate and heated to 200 °C. A LiOH pulse source was pulsed once (gas flow rate 50 sccm, pulse 0.1 s) to form nucleation sites.

[0077] Alternating deposition cycles: (a) atomized LiOH pulse source, gas flow rate 50 sccm, pulse 0.3s; (b) argon purge, gas flow rate 100 sccm, purge 30s; (c) P2S5 gas, gas flow rate 50 sccm, pulse 0.18s; (d) argon purge, gas flow rate 100 sccm, purge 60s. Steps (a) to (d) constitute one cycle, and 100 cycles were repeated to achieve a coating thickness of 10nm.

[0078] Cooling gave LiOH-P2S5 coated NCM811.

[0079] In this embodiment, the molar ratio of Li2O and P2S5 is controlled to be 2.5:1 by adjusting the pulse time.

[0080] Example 3

[0081] The only difference from Example 1 is that the parameters of step (2) are different, as follows:

[0082] NCM811 was used as a substrate and heated to 200 °C. A LiOH pulse source was pulsed once (gas flow rate 50 sccm, pulse 0.1 s) to form nucleation sites.

[0083] Alternating deposition cycles: (a) atomized LiOH pulse source, gas flow rate 50 sccm, pulse 0.28 s; (b) argon purge, gas flow rate 100 sccm, purge 30 s; (c) P2S5 gas, gas flow rate 50 sccm, pulse 0.12 s; (d) argon purge, gas flow rate 100 sccm, purge 60 s. Steps (a) to (d) constitute one cycle, and 100 cycles were repeated to achieve a coating thickness of 10 nm.

[0084] Cooling gave LiOH-P2S5 coated NCM811.

[0085] In this embodiment, the molar ratio of Li2O and P2S5 is controlled to be 3.5:1 by adjusting the pulse time.

[0086] Example 4

[0087] The only difference from Example 1 is that the parameters of step (2) are different, as follows:

[0088] NCM811 was used as a substrate and heated to 200 °C. A LiOH pulse source was pulsed once (gas flow rate 50 sccm, pulse 0.1 s) to form nucleation sites.

[0089] Alternating deposition cycles: (a) atomized LiOH pulse source, gas flow rate 50 sccm, pulse 0.2s; (b) argon purge, gas flow rate 100 sccm, purge 30s; (c) P2S5 gas, gas flow rate 50 sccm, pulse 0.1s; (d) argon purge, gas flow rate 100 sccm, purge 60s. Steps (a)-(d) constitute one cycle, and 200 cycles were repeated to achieve a coating thickness of 20nm.

[0090] Cooling gave LiOH-P2S5 coated NCM811.

[0091] In this embodiment, the thickness of the coating layer is controlled to be 20 nm by adjusting the number of pulse cycles.

[0092] Example 5

[0093] The only difference from Example 1 is that the heat treatment temperature in step (3) is 280°C.

[0094] Example 6

[0095] The only difference from Example 1 is that the heat treatment temperature in step (3) is 320°C.

[0096] Comparative Example 1

[0097] The positive electrode material provided in this comparative example is the uncoated NCM811 in step (1) of Example 1.

[0098] Comparative Example 2

[0099] The positive electrode material provided in this comparative example is NCM811 coated with a commercial fast ion conductor (tungsten oxide).

[0100] Test Example 1

[0101] The XRD pattern of the positive electrode material prepared in Test Example 1 is as follows: Figure 2 shown.

[0102] It can be seen that the diffraction peak of the sample prepared by Example 1 corresponds to the PDF#87-1562 standard card, proving to be a layered crystal structure of α-NaFeO2 type with R-3m space group, and no obvious impurity diffraction peak can be observed, proving that the Li2O-Li3PS4 coating layer does not affect the intrinsic structure of the positive electrode raw material.

[0103] Test Example 2

[0104] The performance of the positive electrode materials provided in the examples and comparative examples was tested, and the results are shown in Table 1. Figure 3 、 Figure 4 .

[0105] Test method:

[0106] 1. Provide lithium supplements

[0107] Lithium supplement: Li5FeO4@Li3SbS4 core-shell particles were synthesized by sol-gel method.

[0108] (1) LiOH and Fe2O3 were mixed in a stoichiometric ratio and ball milled at 400 rpm for 4 h. The resulting mixed powder was calcined in an oxygen atmosphere at 800°C for 3 h to produce Li5FeO4. The calcined material was then sieved through a 400-mesh sieve.

[0109] (2) Provide Li3SbS4 precursor solution

[0110] Weigh 6.9g of Li2S, 17g of Sb2S3, and 3.2g of elemental sulfur in a stoichiometric ratio (control the Li:Sb:S ratio to 3:1:4). Add the Li2S to 100mL of acetonitrile and stir until completely dissolved to obtain a Li2S solution. Sb2S3 is slowly added to the Li2S solution with continuous stirring. Heat to 60°C under argon for 5h until the Sb2S3 is completely dissolved, then filter to remove impurities.

[0111] In this embodiment, the concentration of the Li3SbS4 precursor solution is 0.1M based on Li3SbS4.

[0112] (3) Preparation of Li5FeO4@Li3SbS4 core-shell particles by sol-gel method

[0113] The Li5FeO4 core material obtained in step (1) was dispersed in an organic solvent, acetonitrile, at a mass ratio of 1:1, and ultrasonically treated for 15 minutes to obtain a 50% Li5FeO4 dispersion.

[0114] The Li3SbS4 precursor solution obtained in step (2) was slowly added to the Li5FeO4 dispersion, with a mass ratio of Li5FeO4 to Li3SbS4 of 1:0.01, while continuously stirring. The mixed sol was heated to 50°C in a constant temperature water bath and continuously stirred for 3 hours to allow the Li3SbS4 precursor to gradually hydrolyze and condense to form a gel.

[0115] The gel mixture was centrifuged, washed, and dried at 70°C for 10 hours. The dried particles were heat-treated at 400°C for 3 hours under argon. After cooling naturally to room temperature, the Li5FeO4@Li3SbS4 core-shell structure material was obtained.

[0116] 2. Provide positive electrode layer, electrolyte layer and negative electrode

[0117] Positive electrode layer: Figure 1As shown, the positive electrode is premixed into a positive electrode mixture (positive electrode: sulfide solid electrolyte 1 = 70:30, mass ratio), and the lithium supplement is premixed into a lithium supplement mixture (lithium supplement coated on the surface of step (1): sulfide solid electrolyte 2 = 85:15, mass ratio). Subsequently, the positive electrode mixture, lithium supplement mixture, conductive agent and binder are blended into a composite positive electrode. Sulfide solid electrolyte 1 comes from Ruigu (Quzhou) New Materials Technology Co., Ltd., model LiPSI; sulfide solid electrolyte 2 comes from Ruigu (Quzhou) New Materials Technology Co., Ltd., model Li6PS5Cl; conductive agent is VGCF, and binder is PTFE. Based on 100 parts, the mass proportion of NCM811@Li2O-Li3PS4 in the positive electrode mixture is 65 parts. The mass proportion of the surface-coated lithium supplement in the lithium supplement mixture is 3 parts, the conductive agent accounts for 1 part, and the binder accounts for 1 part. Both premixing and blending were performed using a ball milling process. The two mixtures were first ball milled separately (dual planetary milling, 150 rpm, 1 hour), followed by the composite cathode ball milling (dual planetary milling, 100 rpm, 0.5 hour). 20 mg of the composite cathode powder was placed in a 10 mm diameter mold, and a pressure of 250 MPa was applied and maintained for 10 minutes. The mold was then demolded to obtain the cathode sheet.

[0118] Electrolyte layer: LiPSI is produced using a cold-pressing process. 100mg of electrolyte powder is placed in a 10mm diameter mold, and a pressure of 500MPa is applied and maintained for 10 minutes. The electrolyte layer is then released from the mold.

[0119] Negative electrode: 100um In foil and 300um Li foil were cold pressed together and punched into discs with a diameter of 10mm.

[0120] 3. All-solid-state battery assembly:

[0121] The positive electrode sheet / electrolyte layer / negative electrode sheet are assembled in the order of positive electrode sheet / electrolyte layer / negative electrode sheet in a pressure-maintaining battery mold with an inner diameter of 10 mm, and a fixed pressure of 50 MPa is applied to obtain an all-solid-state battery.

[0122] Test conditions: Perform a 0.1C electrical performance test at room temperature (25°C). The cycle parameters are as follows: 1) 0.1C constant current and constant voltage charge to 3.65V, cutoff current 0.05C; 2) 5 min standby; 3) 0.1C constant current discharge to 1.9V; 4) 5 min standby; 5) repeat steps 1) to 4) until the cycle capacity retention rate is less than 80% of the third cycle.

[0123] At room temperature (25°C), a 1C electrical performance test was conducted with the following parameters: 1) 0.1C constant current and constant voltage charging to 3.65V, with a cut-off current of 0.05C; 2) 5 minutes of waiting; 3) 1C constant current discharge to 1.9V; 4) 5 minutes of waiting.

[0124] It should be noted that the cathode materials and special lithium supplements used in the above preparation process have the following in-situ lithium compensation mechanism: during the first charge, the Li3PS4 coating layer preferentially decomposes and releases Li + During deep cycling, the Li3SbS4 shell gradually dissolves, releasing the Li5FeO4 lithium supplement (above 4.3V). The sulfide electrolyte (Li6PS5Cl) and the lithium supplement shell form a Sb-SP co-doped interface phase. Through these optimizations, a composite structure is employed in the preparation of the positive electrode, achieving differentiated matching to achieve a synergistic effect.

[0125] Table 1 provides the test results of positive electrode material performance for the examples and comparative examples.

[0126]

[0127] It can be seen from Table 1 that the positive electrode material prepared in the embodiment of the present invention can significantly improve the electrochemical performance of the battery compared with the comparative example.

[0128] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A positive electrode material, characterized in that It comprises a ternary positive electrode material matrix and a coating layer coated on the ternary positive electrode material matrix, wherein the coating layer is a Li2O-Li3PS4 composite layer.

2. The positive electrode material according to claim 1, characterized in that The general formula of the ternary cathode material matrix is ​​LiNi 1-x-y Co x Mn y O2, 0.01≤x≤0.3, 0.01≤y≤0.3; Preferably, the ternary cathode material matrix is ​​NCM811; Preferably, the particle size D50 of the ternary cathode material matrix is ​​3 μm-15 μm, and the thickness of the coating layer is 50 nm-200 nm.

3. A method for preparing the positive electrode material according to claim 1 or 2, characterized in that: include: By atomic layer deposition, LiOH and P2S5 are alternately deposited on the surface of the ternary cathode material to obtain a precursor material; The precursor material is heat-treated to form the coating layer.

4. The preparation method according to claim 3, characterized in that The process of preparing the precursor material includes: dissolving LiOH and a solvent, and atomizing the obtained LiOH solution through a carrier gas and then delivering it as a LiOH pulse source; P2S5 is heated and sublimated in an ALD reaction chamber to supply P2S5 gas; The ternary cathode material is used as a substrate, heated to 150°C-200°C, a LiOH pulse source is introduced to form nucleation sites, and then a LiOH pulse source and P2S5 gas are alternately introduced; Preferably, the pulse time is adjusted to control the molar ratio of Li2O and P2S5 to be (2.5-3.5):

1.

5. The preparation method according to claim 4, characterized in that In the preparation process of the LiOH pulse source, the solvent used is selected from at least one of methanol, ethanol, ethylene glycol, isopropanol and tetrahydrofuran, and the concentration of the LiOH solution is 0.005 mol / L-0.05 mol / L.

6. The preparation method according to claim 4, characterized in that The preparation process of the P2S5 gas includes: heating the P2S5 to 155° C.-170° C. in an ALD reaction chamber and adjusting the pressure of the reaction chamber to 0.1 Torr-0.5 Torr.

7. The preparation method according to claim 3, characterized in that Before depositing LiOH and P2S5, the ternary cathode material is dried and plasma cleaned; Preferably, the drying temperature is controlled to be 110°C-130°C, and the drying time is 10h-15h; Preferably, argon plasma is used in the plasma cleaning process.

8. The preparation method according to claim 4, characterized in that The process of alternately introducing LiOH pulse source and P2S5 gas includes: The LiOH pulse source is introduced, the flow rate is controlled to be 40 sccm-60 sccm, and the pulse time is 0.05 s-0.15 s; after the LiOH pulse source is introduced, an inert gas is used for purging, the gas flow rate is controlled to be 80 sccm-120 sccm, and the purge time is 20 s-40 s; The P2S5 gas is introduced, and the gas flow rate is controlled to be 40sccm-60sccm, and the pulse time is 0.1s-0.3s; after the P2S5 gas is introduced, it is purged with an inert gas, and the gas flow rate is controlled to be 80sccm-120sccm, and the purge time is 40s-80s; The process is repeated 50 to 200 times to make the thickness of the coating layer reach 50 nm to 200 nm.

9. The preparation method according to claim 3, characterized in that The heat treatment process includes: heat treating the precursor material at 280° C.-320° C. for 1 h-3 h; Preferably, the heating rate is controlled to be 4°C / min-6°C / min; Preferably, the heat treatment is performed under an inert atmosphere.

10. A sulfide solid-state battery, characterized in that: The invention comprises the positive electrode material according to any one of claims 1 to 2 or the positive electrode material prepared by the preparation method according to any one of claims 3 to 9.

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