Lithium supplement agent with core-shell structure, preparation method of lithium supplement agent and all-solid-state battery

Abstract

The invention discloses a lithium supplement agent with a core-shell structure, a preparation method of the lithium supplement agent and an all-solid-state battery, and relates to the technical field of lithium batteries. According to the invention, Li5FeO4 is taken as a core layer, Li3SbS4 is coated on the core layer to serve as a shell layer, the shell layer of the lithium supplement agent can form an Sb-S-P co-doped interface phase with sulfide electrolyte (such as Li6PS5Cl), and interface side reaction can be inhibited by forming a stable interface, so that the capacity exertion, rate and cycle performance are improved; the compatibility with a positive electrode material and sulfide solid electrolyte is improved; and during deep circulation, the Li3SbS4 shell layer is gradually dissolved to release the Li5FeO4 lithium supplement agent, so that the cycle stability of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a core-shell structure lithium supplement, a preparation method thereof, and an all-solid-state battery. Background Art

[0002] Currently, lithium replenishment technology is mostly used in liquid and semi-solid batteries. For example, Li5FeO4, Li2NiO2, and lithium-rich manganese-based materials are added as positive electrode lithium replenishers to energy storage or power battery systems to improve cycle stability. However, there is little research on positive electrode lithium replenishers in the field of all-solid-state batteries. Sulfide solid electrolytes have serious side reactions at the interface with high-voltage positive electrode materials (such as NCM and lithium-rich manganese-based materials), and existing lithium replenishers (such as Li5FeO4, Li2NiO2, and lithium-rich manganese-based materials) have the following defects in sulfide systems:

[0003] (1) High reactivity, easily reacting with air or sulfide solid electrolyte, leading to failure or production of harmful byproducts;

[0004] (2) Poor compatibility with existing cathode materials and sulfide solid electrolytes, affecting battery performance;

[0005] (3) Poor cycle stability, easy decomposition and gas production, increased interface impedance, resulting in a decrease in cycle life.

[0006] Therefore, there is an urgent need to provide lithium supplements for all-solid-state batteries to improve the compatibility of lithium supplements in sulfide systems and improve the cycle stability of batteries.

[0007] In view of this, the present invention is proposed. Summary of the Invention

[0008] The purpose of the present invention is to provide a core-shell structure lithium supplement agent, a preparation method thereof and an all-solid-state battery, aiming to improve the compatibility of the lithium supplement agent in the sulfide system and improve the cycle stability of the battery.

[0009] The present invention is achieved in that:

[0010] In a first aspect, the present invention provides a core-shell structure lithium supplement, comprising a core layer and a shell layer coated on the core layer, wherein the core layer is Li5FeO4 and the shell layer is Li3SbS4.

[0011] In an optional embodiment, the mass ratio of Li5FeO4 to Li3SbS4 is 1:(0.001-0.05);

[0012] And / or, the particle size of the core-shell structure lithium supplement agent is 200 nm-1 μm.

[0013] In a second aspect, the present invention provides a method for preparing the core-shell structure lithium supplement agent of the aforementioned embodiment, comprising:

[0014] Provide Li5FeO4 and Li3SbS4 precursor solutions;

[0015] Mixing and dispersing Li5FeO4 and an organic solvent to obtain a dispersion;

[0016] The Li3SbS4 precursor solution is mixed with the dispersion to react and form a gel;

[0017] The gel is dried and then heat treated.

[0018] In an optional embodiment, the process of forming the gel includes: mixing the Li3SbS4 precursor solution and the dispersion liquid, and reacting them at 40°C-60°C for 2h-4h.

[0019] In an optional embodiment, the heat treatment temperature is controlled to be 300° C.-500° C., and the heat treatment time is 2 h-4 h;

[0020] and / or, heat treatment is performed under an inert atmosphere.

[0021] In an optional embodiment, the gel is washed before being dried;

[0022] And / or, the drying temperature is controlled to be 60° C.-80° C., and the drying time is controlled to be 6 h-12 h.

[0023] In an optional embodiment, during the preparation of the dispersion, the organic solvent used is selected from at least one of acetonitrile and tetrahydrofuran;

[0024] and / or, mixing Li5FeO4 and an organic solvent and then subjecting the mixture to ultrasonic treatment for 10 min to 20 min;

[0025] And / or, in the dispersion, the mass fraction of Li5FeO4 is 30%-70%.

[0026] In an optional embodiment, the preparation process of the Li3SbS4 precursor solution includes: weighing Li2S, Sb2S3 and elemental sulfur according to a stoichiometric ratio, mixing and dissolving Li2S and an organic solvent to obtain a Li2S solution, mixing Sb2S3, elemental sulfur and the Li2S solution at 50°C-70°C and reacting for 4h-6h until Sb2S3 and elemental sulfur are dissolved;

[0027] And / or, the concentration of the Li3SbS4 precursor solution is 0.01M-0.2M based on Li3SbS4.

[0028] In an optional embodiment, the preparation process of Li5FeO4 includes: mixing LiOH and Fe2O3 in a stoichiometric ratio, followed by calcination;

[0029] Among them, LiOH and Fe2O3 were mixed by ball milling;

[0030] And / or, the calcination temperature is controlled to be 700° C.-900° C., and the calcination time is controlled to be 1 hour-5 hours.

[0031] In a third aspect, the present invention provides an all-solid-state battery, comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active layer loaded on the positive electrode current collector, the positive electrode active layer containing the core-shell structure lithium replenisher of any one of the aforementioned embodiments or the core-shell structure lithium replenisher prepared by the preparation method of any one of the aforementioned embodiments.

[0032] The present invention has the following beneficial effects: the present invention uses Li5FeO4 as a core layer and coats Li3SbS4 on the core layer as a shell layer. The shell layer of the lithium replenisher can form an Sb-SP co-doped interface phase with a sulfide electrolyte (such as Li6PS5Cl). By forming a stable interface, the interface side reactions can be suppressed, thereby improving the capacity, rate and cycle performance; improving the compatibility with the positive electrode material and the sulfide solid electrolyte; during deep cycling, the Li3SbS4 shell layer gradually dissolves to release the Li5FeO4 lithium replenisher, which is beneficial to improving the cycle stability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] 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.

[0034] Figure 1 The first cycle charge and discharge test comparison curves of Example 1, Comparative Example 1 and Comparative Example 2 are shown;

[0035] Figure 2 The first cycle charge and discharge test comparison curves of Example 1, Example 2 and Example 5 are shown;

[0036] Figure 3 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] The present invention improves the lithium supplement for all-solid-state batteries by coating Li3SbS4 on the surface of the lithium supplement Li5FeO4 to form a Li5FeO4@Li3SbS4 core-shell lithium supplement, thereby improving the compatibility with the positive electrode material and the sulfide solid electrolyte, and at the same time improving the cycle stability of the battery.

[0039] An embodiment of the present invention also provides a core-shell structure lithium supplement agent, including a core layer and a shell layer coated on the core layer, the core layer is Li5FeO4, and the shell layer is Li3SbS4. The shell layer of the lithium supplement agent can form an Sb-SP co-doped interface phase with the sulfide electrolyte (such as Li6PS5Cl), thereby improving the compatibility with the positive electrode material and the sulfide solid electrolyte; during deep cycling, the Li3SbS4 shell layer gradually dissolves and releases the Li5FeO4 lithium supplement agent (above 4.3V), which is beneficial to improving the cycle stability of the battery.

[0040] In some embodiments, the mass ratio of Li5FeO4 to Li3SbS4 is 1:(0.001-0.05). Within this range, the lithium supplement can be used in all-solid-state batteries to better improve the battery's cycling stability. The core-shell structure lithium supplement has a particle size of 200nm-1μm, such as 200nm, 500nm, 800nm, 1000nm, etc.

[0041] The present invention provides a method for preparing a core-shell structure lithium supplement, comprising the following steps:

[0042] S1, provide Li5FeO4

[0043] Li5FeO4 can be synthesized independently using conventional methods, such as high-temperature solid-phase reaction or sol-gel method.

[0044] In some embodiments, the preparation process of Li5FeO4 includes: mixing LiOH and Fe2O3 in a stoichiometric ratio (i.e., according to a Li:Fe molar ratio of 5:1), followed by calcination in an oxygen atmosphere. Li5FeO4 is prepared by a high-temperature solid-phase reaction. When the mixed powder is calcined, the calcination temperature is controlled to be 700°C-900°C, such as 700°C, 750°C, 800°C, 850°C, 900°C, etc.; the calcination time is 1 hour-5 hours, such as 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, etc.

[0045] In some embodiments, the materials may be mixed by ball milling. LiOH and Fe2O3 are added to a ball mill in a stoichiometric ratio and milled. The speed may be controlled to be 200 rpm-500 rpm, and the ball milling time may be 2 h-6 h.

[0046] S2. Provide Li3SbS4 precursor solution

[0047] By adjusting the raw material ratio, the types of elements such as Li and Sb in the precursor solution can meet the requirements. For example, Li2S and Sb2S3 can be used as raw materials, and the raw materials and organic solvent can be completely dissolved.

[0048] In some embodiments, the preparation process of the Li3SbS4 precursor solution includes: weighing Li2S, Sb2S3, and elemental sulfur in a stoichiometric ratio, first mixing and dissolving the Li2S with an organic solvent to obtain a Li2S solution, then mixing the Sb2S3, elemental sulfur, and Li2S solution at 50°C-70°C for 4-6 hours until the Sb2S3 and elemental sulfur are dissolved, and filtering to remove impurities to obtain a Li3SbS4 precursor solution. During the reaction, due to solubility limitations, elemental sulfur and Sb2S3 gradually dissolve and react with the Li2S.

[0049] Specifically, the reaction process can be carried out under an inert atmosphere, which can be nitrogen, argon, etc. The heating temperature can be 50° C., 55° C., 60° C., 65° C., 70° C., etc., and the reaction time can be 4 h, 5 h, 6 h, etc.

[0050] In some embodiments, the concentration of the Li3SbS4 precursor solution is 0.01M-0.2M, such as 0.01M, 0.05M, 0.10M, 0.15M, 0.20M, etc., based on Li3SbS4. The concentration of the Li3SbS4 precursor solution is adjusted to a suitable level to facilitate subsequent gel formation.

[0051] Furthermore, the type of the organic solvent is not limited and may be acetonitrile, tetrahydrofuran, or the like.

[0052] S3. Preparation of Li5FeO4@Li3SbS4 core-shell particles by sol-gel method

[0053] Li5FeO4 and an organic solvent are mixed and dispersed to obtain a dispersion; the Li3SbS4 precursor solution obtained in step S2 is mixed and reacted with the dispersion to form a gel; the gel is dried and then heat-treated. The Li3SbS4 precursor gradually hydrolyzes and condenses to form a gel, which is then dried to remove the organic solvent and form particles. The Li3SbS4 shell is then heat-treated to crystallize and tightly bond to the Li5FeO4 core.

[0054] In some embodiments, during the preparation of the dispersion, the organic solvent used is selected from at least one of acetonitrile and tetrahydrofuran, and the organic solvent can be any one or more of the above. By regulating the amount of the organic solvent, the mass fraction of Li5FeO4 in the dispersion is 30%-70% (e.g., 30%, 40%, 50%, 60%, 70%, etc.). The mixing method of Li5FeO4 and the organic solvent is not limited. For example, ultrasonic treatment can be used to improve the uniformity of dispersion. The ultrasonic treatment time can be 10 min-20 min, such as 10 min, 15 min, 20 min, etc.

[0055] In some embodiments, the gel formation process includes slowly adding a Li3SbS4 precursor solution to a Li5FeO4 dispersion, continuously stirring and mixing until uniformly mixed, and reacting the resulting mixed sol at 40°C-60°C for 2-4 hours to hydrolyze and condense the Li3SbS4 precursor to form a gel. Specifically, heating can be performed in a constant temperature water bath at 40°C, 45°C, 50°C, 55°C, 60°C, etc., and the reaction time can be 2 hours, 3 hours, 4 hours, etc.

[0056] By adjusting the amount of Li3SbS4 precursor solution and Li5FeO4 dispersion, the mass ratio of Li5FeO4 to Li3SbS4 is 1:(0.001-0.05), such as 1:0.001, 1:0.010, 1:0.020, 1:0.030, 1:0.040, 1:0.050, etc. Within this range, it can better match the sulfide electrolyte, which is beneficial to improving the cycle performance of the battery.

[0057] In some embodiments, before drying the resulting gel, impurities such as surface solvents can be removed by centrifugation and washing. During the drying process, the drying temperature is controlled to be 60°C-80°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, etc., and the drying time is 6 hours-12 hours, such as 6 hours, 8 hours, 10 hours, 12 hours, etc.

[0058] Furthermore, after drying, solid particles are obtained, and heat treated under an inert atmosphere, with the heat treatment temperature controlled to be 300°C-500°C and the heat treatment time to be 2h-4h, so that the Li3SbS4 shell is fully crystallized and tightly bonded to the Li5FeO4 core. Specifically, the type of inert atmosphere is not limited, such as nitrogen, argon, etc. The heat treatment temperature is not limited, such as 300°C, 350°C, 400°C, 450°C, 500°C, etc., and the heat treatment time can be 2h, 3h, 4h, etc. After the heat treatment is completed, the mixture is naturally cooled to room temperature to obtain a Li5FeO4@Li3SbS4 core-shell structure material.

[0059] An embodiment of the present invention provides an all-solid-state battery, comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector and a positive electrode active layer supported on the positive electrode current collector, the positive electrode active layer containing a core-shell structure lithium supplement provided by an embodiment of the present invention. The core-shell structure lithium supplement provided by an embodiment of the present invention can better match sulfide electrolytes (such as Li6PS5Cl), forming an Sb-SP co-doped interface phase with the lithium supplement shell, thereby improving the battery's cycling stability.

[0060] It should be noted that the types of positive electrode active materials, binders, conductive agents, sulfide electrolytes, etc. in the positive electrode sheet are not limited, and the type of positive electrode current collector is not limited. The negative electrode of the all-solid-state battery can adopt existing negative electrode preparation methods, and the type of electrolyte layer is also not limited, such as Li6PS5Cl.

[0061] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0062] Example 1

[0063] This embodiment provides a method for preparing a core-shell structure lithium supplement, the steps are as follows:

[0064] (1) Provide Li5FeO4

[0065] LiOH and Fe2O3 were mixed in a stoichiometric ratio and milled in a ball mill at 400 rpm for 4 hours. The resulting mixed powder was calcined in an oxygen atmosphere at 800°C for 3 hours to produce Li5FeO4. The calcined material was then sieved through a 400-mesh screen.

[0066] (2) Provide Li3SbS4 precursor solution

[0067] 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.

[0068] In this embodiment, the concentration of the Li3SbS4 precursor solution is 0.1M based on Li3SbS4.

[0069] (3) Preparation of Li5FeO4@Li3SbS4 core-shell particles by sol-gel method

[0070] 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.

[0071] 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.

[0072] 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.

[0073] Example 2

[0074] The only difference from Example 1 is that in step (2), the concentration of Li3SbS4 is adjusted to 0.05M, thereby changing the mass ratio of Li5FeO4 to Li3SbS4 in the product. The specific steps are as follows:

[0075] The Li5FeO4 core material obtained in step (1) of Example 1 was dispersed in an organic solvent, acetonitrile, at a mass ratio of 1:1 and subjected to ultrasonic treatment for 15 minutes to obtain a 50% Li5FeO4 dispersion.

[0076] After the Li3SbS4 precursor solution obtained in step (2) of Example 1 was adjusted to 0.05M, it was slowly added to the Li5FeO4 dispersion, with a mass ratio of Li5FeO4 to Li3SbS4 of 1:0.005, 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.

[0077] 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.

[0078] Example 3

[0079] The only difference from Example 1 is that in step (2), the concentration of Li3SbS4 is adjusted to 0.15M, thereby changing the mass ratio of Li5FeO4 to Li3SbS4 in the product. The specific steps are as follows:

[0080] The Li5FeO4 core material obtained in step (1) of Example 1 was dispersed in an organic solvent, acetonitrile, at a mass ratio of 1:1 and subjected to ultrasonic treatment for 15 minutes to obtain a 50% Li5FeO4 dispersion.

[0081] After the Li3SbS4 precursor solution obtained in step (2) of Example 1 was adjusted to 0.15M, it was slowly added to the Li5FeO4 dispersion, with a mass ratio of Li5FeO4 to Li3SbS4 of 1:0.015, 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.

[0082] 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.

[0083] Example 4

[0084] The only difference from Example 1 is that in step (3), the concentration of Li3SbS4 is adjusted to 0.2M, thereby changing the mass ratio of Li5FeO4 to Li3SbS4 in the product. The specific steps are as follows:

[0085] The Li5FeO4 core material obtained in step (1) of Example 1 was dispersed in an organic solvent, acetonitrile, at a mass ratio of 1:1 and subjected to ultrasonic treatment for 15 minutes to obtain a 50% Li5FeO4 dispersion.

[0086] After the Li3SbS4 precursor solution obtained in step (2) of Example 1 was adjusted to 0.2M, it was slowly added to the Li5FeO4 dispersion, with a mass ratio of Li5FeO4 to Li3SbS4 of 1:0.02, 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.

[0087] 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.

[0088] Example 5

[0089] The only difference from Example 1 is that the heat treatment temperature in step (3) is 500° C. and the time is 2 h.

[0090] Example 6

[0091] The only difference from Example 1 is that the heat treatment temperature in step (3) is 300° C. and the time is 5 h.

[0092] Example 7

[0093] The only difference from Example 1 is that the heat treatment temperature in step (3) is 400° C. and the time is 2 h.

[0094] Comparative Example 1

[0095] The Li5FeO4 prepared in Example 1 is provided as a lithium supplement.

[0096] Comparative Example 2

[0097] Provide commercial carbon-coated Li5FeO4 as a lithium supplement.

[0098] Test Example 1

[0099] The lithium supplement agents prepared in the examples and comparative examples were applied to all-solid-state batteries, and their performance was tested. The results are shown in Table 1.

[0100] The all-solid-state battery assembly process is as follows:

[0101] (1) Provide positive electrode materials: commercial high nickel 9 series positive electrode materials.

[0102] (2) Preparation of a positive electrode sheet: The positive electrode material and the lithium supplement provided in the examples or comparative examples were mixed in a ratio of 97:3 as the active material. The active material, sulfide solid electrolyte (Li6PS5Cl), conductive agent (VGCF), and binder (PTFE) were uniformly mixed in a mass ratio of 68:30:1:1 (ball milling at 300 rpm for 0.5 h) to obtain a positive electrode powder. 20 mg of the positive electrode powder was placed in a mold with a diameter of 10 mm. A pressure of 250 MPa was applied and maintained for 10 minutes. The mold was then demolded to obtain a positive electrode sheet.

[0103] (3) Preparation of negative electrode sheet: 100 μm In foil and 300 μm Li foil were cold pressed together and punched into discs with a diameter of 10 mm.

[0104] (4) Providing the electrolyte layer: Li6PS5Cl is formed using a cold pressing process. 100 mg of electrolyte powder is placed in a mold with a diameter of 10 mm. A pressure of 500 MPa is applied and maintained for 10 minutes. The electrolyte layer is then removed from the mold.

[0105] (5) Assembly: Assemble the positive electrode sheet / electrolyte layer / negative electrode sheet in the order of the positive electrode sheet / electrolyte layer / negative electrode sheet in a pressure-maintaining battery mold with an inner diameter of 10 mm, and apply a fixed pressure of 50 MPa to obtain an all-solid-state battery.

[0106] Test conditions: Electrical performance test was conducted at room temperature (25°C). Cycle parameters were set as follows: 1) 0.1C constant current constant voltage charge to 3.65V, cut-off 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.

[0107] Table 1 Comparison of the effects of lithium supplements prepared in Examples and Comparative Examples on all-solid-state batteries

[0108] Group 0.1C gram capacity (mAh / g) First effect (%) 0.1C cycle (circle) Example 1 220.6 81.6 54 Example 2 222.3 80.5 46 Example 3 219.0 81.5 52 Example 4 217.8 82.0 51 Example 5 219.3 79.7 44 Example 6 218.5 80.5 45 Example 7 219.0 79.9 47 Comparative Example 1 225.8 78.6 35 Comparative Example 2 201.6 75.7 22

[0109] From Table 1, Figure 1 、 Figure 2 and Figure 3 It can be seen that compared with Comparative Example 1 and Comparative Example 2, the Li5FeO4@Li3SbS4 lithium-supplementing material prepared by this scheme has a good effect in sulfide all-solid-state batteries and significantly improves the cycle performance of sulfide all-solid-state batteries.

[0110] 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 core-shell structure lithium supplement, characterized in that: It includes a core layer and a shell layer coated on the core layer, the core layer is Li5FeO4, and the shell layer is Li3SbS4.

2. The core-shell structure lithium supplement according to claim 1, characterized in that The mass ratio of Li5FeO4 to Li3SbS4 is 1:(0.001-0.05) And / or, the particle size of the core-shell structure lithium supplement agent is 200 nm-1 μm.

3. A method for preparing the core-shell structure lithium supplement agent according to claim 1 or 2, characterized in that: include: Provide Li5FeO4 and Li3SbS4 precursor solutions; Mixing and dispersing Li5FeO4 and an organic solvent to obtain a dispersion; Mixing the Li3SbS4 precursor solution with the dispersion to form a gel; The gel is dried and then heat treated.

4. The preparation method according to claim 3, characterized in that The process of forming the gel includes: mixing the Li3SbS4 precursor solution with the dispersion solution, and reacting them at 40°C-60°C for 2h-4h.

5. The preparation method according to claim 3, characterized in that Control the heat treatment temperature to 300℃-500℃ and the heat treatment time to 2h-4h; and / or, heat treatment is performed under an inert atmosphere.

6. The preparation method according to claim 3, characterized in that Before drying the gel, it is first washed; And / or, the drying temperature is controlled to be 60° C.-80° C., and the drying time is controlled to be 6 h-12 h.

7. The preparation method according to claim 3, characterized in that In the process of preparing the dispersion, the organic solvent used is selected from at least one of acetonitrile and tetrahydrofuran; and / or, mixing Li5FeO4 and the organic solvent and then subjecting the mixture to ultrasonic treatment for 10 min to 20 min; And / or, in the dispersion, the mass fraction of Li5FeO4 is 30%-70%.

8. The preparation method according to claim 3, characterized in that The preparation process of the Li3SbS4 precursor solution includes: weighing Li2S, Sb2S3 and elemental sulfur according to a stoichiometric ratio, mixing and dissolving Li2S with an organic solvent to obtain a Li2S solution, mixing Sb2S3, elemental sulfur and the Li2S solution at 50°C-70°C for 4h-6h to react until Sb2S3 and elemental sulfur are dissolved; And / or, based on Li3SbS4, the concentration of the Li3SbS4 precursor solution is 0.01M-0.2M.

9. The preparation method according to claim 3, characterized in that The preparation process of Li5FeO4 includes: mixing LiOH and Fe2O3 in a stoichiometric ratio and then calcining; Among them, LiOH and Fe2O3 were mixed by ball milling; And / or, the calcination temperature is controlled to be 700° C.-900° C., and the calcination time is controlled to be 1 hour-5 hours.

10. An all-solid-state battery, characterized in that: The invention comprises a positive electrode sheet, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active layer supported on the positive electrode current collector, wherein the positive electrode active layer contains the core-shell structure lithium supplement agent according to any one of claims 1 to 2 or the core-shell structure lithium supplement agent prepared by the preparation method according to any one of claims 3 to 9.

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