A core-shell structure composite solid electrolyte resistant to lithium negative electrode, a preparation method and application thereof

Abstract

The application provides a core-shell structure composite solid electrolyte resistant to lithium negative electrode, a preparation method and application thereof, and comprises the following steps: A) mixing a lithium source, an aluminum source, a titanium source and a phosphorus source, and then sintering by using joule heating to obtain a porous LATP material; in the lithium source, the aluminum source, the titanium source and the phosphorus source in the step A), at least one raw material capable of generating gas in the sintering process is contained; B) dissolving the LATP and soluble LAGP raw materials in water, centrifugal spray drying to obtain a LAGP@LATP precursor powder; C) pressing the dry powder; the LATP material with a multi-gradient core-shell composite structure designed based on the application has the characteristics of high ionic conductivity, stable material structure, resistance to lithium negative electrode and the like; and can be applied to a full-solid-state lithium negative electrode battery, and is used for improving the battery performance and stability.

Description

Technical Field

[0001] This invention belongs to the field of all-solid-state lithium battery technology, and particularly relates to a core-shell structure composite solid electrolyte that is resistant to lithium anodes, its preparation method and application. Background Technology

[0002] In modern society, batteries are crucial for powering numerous devices such as smartphones, laptops, electric vehicles, and renewable energy grids. With the increasing demand for portable electronics and electric vehicles (EVs), the need for high-performance, long-life, and safe batteries is becoming increasingly urgent. Advances in battery technology can significantly impact how we live and work, from achieving sustainable energy to reducing dependence on fossil fuels. Unfortunately, lithium-ion batteries face safety concerns and challenges in further improving energy density. Therefore, strengthening research into battery technology is imperative. Oxide inorganic solid electrolytes (OTEs) possess high ionic conductivity, thus providing a stable and efficient transport medium for ion flow between the anode and cathode in batteries. Furthermore, solid electrolytes can prevent side reactions between electrodes and electrolytes, thus avoiding the formation of dendritic crystals and improving the overall energy density of the battery. For example, LATP (Lithium Aluminum Hydroxide) possesses advantageous properties such as high ionic conductivity, chemical stability, and low reactivity with lithium metal anodes. They hold immense potential in driving the development of energy storage and paving the way for safer, more efficient, and more environmentally friendly batteries.

[0003] However, because LATP contains Ti ions, when it comes into contact with a highly reducing lithium anode, the valence of titanium changes, which alters the entire crystal structure and can easily lead to battery stability issues. Summary of the Invention

[0004] This invention provides a core-shell composite solid electrolyte that is resistant to lithium anodes, its preparation method and application. The core-shell composite solid electrolyte of this invention has high ionic conductivity, is resistant to lithium anodes and has good material stability, which can improve the stability of all-solid-state lithium batteries.

[0005] A method for preparing a core-shell composite solid electrolyte resistant to lithium anodes includes the following steps:

[0006] A) A porous LATP material is obtained by mixing lithium, aluminum, titanium and phosphorus sources and then sintering them using Joule heating.

[0007] The lithium source, aluminum source, titanium source and phosphorus source in step A) contain at least one raw material that can generate gas during sintering.

[0008] B) Dissolve LATP and soluble LAGP preparation raw materials in water, centrifuge and spray dry to obtain LAGP@LATP precursor powder;

[0009] The raw materials for preparing the soluble LAGP include soluble lithium source, soluble aluminum source, soluble germanium source and soluble phosphorus source;

[0010] C) The dried powder is pressed to obtain LAGP@LATP precursor ceramic sheets, and then sintered using Joule heating to obtain a core-shell composite solid electrolyte with lithium anode tolerance.

[0011] Preferably, in step A), the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium bicarbonate, and lithium oxide; the aluminum source is aluminum oxide and / or aluminum hydroxide; the titanium source is titanium trioxide and / or titanium dioxide; and the phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, and diamine hydrogen phosphate.

[0012] Preferably, the Joule heating temperature in step A) is 800–1000°C; and the sintering time in step A) is 30–120 s.

[0013] Preferably, the mass of the soluble LAGP preparation raw material accounts for 5-10% of the total mass of the LATP and the soluble LAGP preparation raw material.

[0014] Preferably, in step B), the inlet temperature of the centrifugal spray dryer is 220-280°C, the outlet temperature is 85-100°C, and the centrifugal nozzle speed is 500-800 rpm.

[0015] Preferably, the pressing pressure in step C) is 5-15 MPa, and the holding time is 10-20 min.

[0016] Preferably, the Joule heating temperature in step C) is 800–1000°C; and the sintering time in step C) is 30–90 s.

[0017] This invention provides a core-shell structured composite solid electrolyte that is resistant to lithium anodes, which is prepared according to the preparation method described above;

[0018] The core-shell composite solid electrolyte with lithium-resistant anode has a porous LATP core and a dense LAGP shell layer. The porosity of the LATP core is 25-40%, and the porosity of the LAGP shell layer is ≤5%.

[0019] Preferably, in the LATP core, the volume fraction of LATP decreases from 75-85% to 45-55% from the inside out.

[0020] This invention provides an all-solid-state lithium battery, comprising a positive electrode, a solid electrolyte, and a lithium negative electrode;

[0021] The solid electrolyte is the core-shell structured composite solid electrolyte with lithium anode tolerance described above.

[0022] This invention provides a method for preparing a core-shell composite solid electrolyte resistant to lithium anodes, comprising the following steps: A) mixing a lithium source, an aluminum source, a titanium source, and a phosphorus source and sintering them using Joule heating to obtain a porous LATP material; wherein the lithium source, aluminum source, titanium source, and phosphorus source in step A) contain at least one raw material capable of generating gas during sintering; B) dissolving LATP and a soluble LAGP raw material in water, centrifuging and spray drying to obtain LAGP@LATP precursor powder; wherein the soluble LAGP raw material includes a soluble lithium source, a soluble aluminum source, a soluble germanium source, and a soluble phosphorus source; C) pressing the dried powder to obtain LAGP@LATP precursor ceramic sheets, and then sintering them using Joule heating to obtain a core-shell composite solid electrolyte resistant to lithium anodes. This invention utilizes an in-situ synthesis method on the surface of LATP (Lithium-Ion Hydrogen Electrolyte) using various nanoscale raw materials to prepare a multi-gradient core-shell composite LATP. Subsequently, through Joule heating (UFS), a solid-state electrolyte layer without variable valence elements is directly and rapidly synthesized in situ on the LATP surface. This layer exhibits relatively stable chemical properties, reduced solid-solid reaction interface impedance, and the ability to withstand the high reducing properties of lithium anodes. Furthermore, both the core and outer shell possess a certain degree of ionic conductivity, reducing the content of non-ionic conductive materials in all-solid-state batteries and improving their energy density. In summary, the LATP material with a multi-gradient core-shell composite structure designed based on this invention possesses high ionic conductivity, stable material structure, and tolerance to lithium anodes; it can be applied in all-solid-state lithium anode batteries to improve battery performance and stability. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the structure of the LAGP@LATP composite electrolyte material in this invention.

[0025] Figure 1 In the diagram, 1 represents a porous LATP material, 2 represents a LAGP@LATP precursor, and 3 represents a LAGP@LATP composite electrolyte material.

[0026] Figure 2 These are scanning electron microscope images of the LAGP@LATP composite electrolyte material in Example 2 of this invention at different magnifications;

[0027] Figure 3 The XRD pattern of the LAGP@LATP composite electrolyte material of Example 2 of the present invention is shown below.

[0028] Figure 4 The charging and discharging test curves of the batteries in Examples 1-4 and the comparative examples are shown. Detailed Implementation

[0029] This invention provides a method for preparing a core-shell composite solid electrolyte resistant to lithium anodes, comprising the following steps:

[0030] A) A porous LATP material is obtained by mixing lithium, aluminum, titanium and phosphorus sources and then sintering them using Joule heating.

[0031] The lithium source, aluminum source, titanium source and phosphorus source in step A) contain at least one raw material that can generate gas during sintering.

[0032] B) Dissolve LATP and soluble LAGP raw materials in water, centrifuge and spray dry to obtain LAGP@LATP precursor powder;

[0033] The soluble LAGP raw materials include soluble lithium sources, soluble aluminum sources, soluble germanium sources, and soluble phosphorus sources;

[0034] C) The dried powder is pressed to obtain LAGP@LATP precursor ceramic sheets, and then sintered using Joule heating to obtain a core-shell composite solid electrolyte with lithium anode tolerance.

[0035] In this invention, the raw materials for preparing the LATP core include a lithium source, an aluminum source, a titanium source, and a phosphorus source, wherein at least one of the raw materials is capable of generating volatile gases (such as CO2, NH3, etc.) during sintering, such as lithium carbonate, lithium oxalate, lithium bicarbonate, ammonium dihydrogen phosphate, diammonium phosphate, etc. Specifically, the lithium source is preferably one or more of lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium bicarbonate, and lithium oxide; the aluminum source is preferably alumina and / or aluminum hydroxide; the titanium source is preferably titanium trioxide and / or titanium dioxide; and the phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, and diamine hydrogen phosphate.

[0036] In this invention, the lithium source, aluminum source, titanium source and phosphorus source are mixed in proportion according to the stoichiometric ratio of LATP (lithium aluminum titanium phosphate). Preferably, the lithium source, aluminum source, titanium source and phosphorus source are ground and mixed. Specifically, the lithium source, aluminum source, titanium source and phosphorus source are dispersed in a solvent, a grinding medium is added, and grinding is performed using grinding balls.

[0037] In this invention, the solvent is preferably deionized water; the grinding medium is preferably one or more of deionized water, anhydrous ethanol, isopropanol, and N-methylpyrrolidone, and the mass ratio of the grinding medium to the powder is preferably (2-10):1, more preferably (5-6):1; the grinding balls are preferably one or more of zirconia balls, alumina balls, and agate balls, and the diameter of the grinding balls is preferably 0.3-5 mm, more preferably 1-3 mm; the ball-to-powder ratio (mass of grinding balls: mass of powder) in the grinding process is preferably 5-20.

[0038] The present invention dries, grinds and sieves the slurry obtained by grinding to obtain core precursor powder, and sintersulates the core precursor powder using Joule heating to obtain LATP material.

[0039] In this invention, the drying temperature of the slurry is preferably 80–120°C, more preferably 100–110°C. After drying, the slurry is passed through an 80–400 mesh sieve to obtain the core precursor powder. This invention achieves multi-gradient porous LATP material as the core of a solid electrolyte by Joule heating sintering of LATP material and selecting raw materials capable of generating gas during the sintering process, thereby reducing lithium loss.

[0040] In this invention, the Joule heating temperature is preferably 800–1000°C, more preferably 850–950°C, such as 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, preferably within the range of any of the above values ​​as the upper or lower limit; the sintering holding time is preferably 30–120 s, more preferably 50–100 s, such as 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, 100 s, 110 s, 120 s, preferably within the range of any of the above values ​​as the upper or lower limit.

[0041] After obtaining LATP powder, the present invention stirs and dissolves LATP powder and water-soluble LAGP preparation raw materials in water, then dries them into powder by centrifugal spray drying, and then presses the powder to obtain ceramic sheets of LAGP@LATP precursor.

[0042] In this invention, the water-soluble raw materials for preparing LAGP include a soluble lithium source, a soluble aluminum source, a soluble germanium source, and a soluble phosphorus source. The soluble lithium source is preferably one or more of lithium hydroxide, lithium nitrate, lithium oxalate, and lithium bicarbonate. The soluble aluminum source is preferably one or more of aluminum nitrate and aluminum sulfate. The soluble germanium source is preferably germanium oxalate and / or germanium nitrate. The soluble phosphorus source is preferably one or more of phosphoric acid, ammonium dihydrogen phosphate, and diamine hydrogen phosphate.

[0043] In this invention, the inlet temperature of the centrifugal spray dryer is preferably 220-280°C, more preferably 230-270°C, and most preferably 240-250°C; the outlet temperature is preferably 85-100°C, more preferably 90-95°C; and the centrifugal nozzle speed is preferably 500-800 rpm, more preferably 600-700 rpm.

[0044] In this invention, the pressing pressure is preferably 5-15 MPa, more preferably 8-12 MPa, and the pressing holding time is preferably 10-20 min, more preferably 12-18 min.

[0045] The ceramic sheets of the obtained LAGP@LATP precursor were sintered using Joule heating to obtain a core-shell composite solid electrolyte with a lithium anode tolerance.

[0046] In this invention, the Joule heating temperature is preferably 800–1000°C, more preferably 850–950°C, such as 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, preferably within the range of any of the above values ​​as the upper or lower limit; the sintering holding time is preferably 30–90 s, more preferably 50–80 s, such as 30 s, 40 s, 50 s, 60 s, 70 s, 80 s, 90 s, preferably within the range of any of the above values ​​as the upper or lower limit.

[0047] The present invention also provides a core-shell structured composite solid electrolyte that is resistant to lithium anodes, which is prepared according to the preparation method described above;

[0048] The core-shell composite solid electrolyte with lithium-resistant anode has a porous LATP core and a dense LAGP shell layer. The porosity of the LATP core is 25-40%, and the porosity of the LAGP shell layer is ≤5%.

[0049] In this invention, the LATP core has a gradient from 75-85% to 45-55% in volume fraction from the inside out, with a gradient transition slope of 0.5-2% / μm; the porosity of the LATP core is preferably 25-40%, more preferably 30-35%; the pore size is preferably 200-800 nm, and the pore aspect ratio is preferably 3:1-8:1, more preferably 4:1-6:1.

[0050] In this invention, the "LATP volume fraction" in the core refers to the percentage of LATP volume in a certain area of ​​space due to the porous structure of the LATP core. In the LATP core of this invention, the porosity gradient increases from the inside to the outside, resulting in a decrease in the LATP volume fraction gradient. The porosity increases from the inside to the outside by 15-25% to 45-55%. In the radial direction of the LATP core, the decrease rate of LATP volume fraction from the inside to the outside is 0.5-2% / μm, that is, in the radial direction of the LATP core, the increase rate of porosity from the inside to the outside is 0.5-2% / μm.

[0051] In this invention, the pore structure in the LATP core is radially oriented with the LATP core center as the starting point and the core surface as the midpoint, forming an angle of 15° to 45° with the normal to the core surface; Al3 + The concentration of LATP increases by 0.5–1.2 at.% (atomic percentage) from the core to the surface.

[0052] The present invention also provides an all-solid-state lithium battery, comprising a positive electrode, a solid electrolyte and a lithium negative electrode;

[0053] The solid electrolyte is the core-shell structured composite solid electrolyte with lithium anode tolerance described above.

[0054] In this invention, the positive electrode preferably includes a positive current collector and a positive electrode coating composited on the surface of the positive current collector. The positive electrode coating includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material is preferably one or more of lithium cobalt oxide, lithium manganese oxide, ternary nickel-cobalt-manganese lithium, nickel-manganese lithium oxide, lithium iron phosphate, lithium manganese iron phosphate, and lithium-rich manganese-based positive electrode materials. The conductive agent is preferably one or more of conductive carbon black, carbon nanotubes, and graphene. The binder is preferably one or more of polyvinylidene fluoride, polytetrafluoroethylene, polymethyl methacrylate, and hexafluoropropylene copolymer.

[0055] The LAGP@LATP composite solid electrolyte material of this invention has a short sintering time, is free of non-conductive impurities, and possesses high ionic conductivity, stable material structure, and tolerance to lithium anodes. When applied to batteries, it can improve battery energy density and safety stability. The raw materials used are inexpensive and readily available, resulting in low cost, simple processing, and ease of large-scale industrialization.

[0056] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, describes a core-shell composite solid electrolyte with lithium anode tolerance, its preparation method, and its application, but this should not be construed as limiting the scope of protection of the present invention.

[0057] Example 1

[0058] 1. Preparation of LATP materials

[0059] Weigh 54.31g of lithium carbonate, 20.39g of aluminum oxide, 127.79g of titanium dioxide, and 333.58g of ammonium dihydrogen phosphate. After mixing the precursors, perform UFS sintering on the precursors under the following conditions: 900℃ for 45s. After sintering, pulverize the precursors into 1μm powder.

[0060] 2. Preparation of LAGP@LATP materials

[0061] After crushing the above materials, add them to a ball mill. Weigh out 15.58g of lithium dihydrogen phosphate, 8.52g of aluminum nitrate, 38.50g of germanium oxalate, and 17.60g of ammonium dihydrogen phosphate. Add deionized water and ball mill to achieve a solid content of 10%. The ball milling speed is 500rpm / h for 3 hours, and the particle size is 200nm.

[0062] The above slurry was spray-dried with the following parameters: centrifugal nozzle speed of 500 rpm / min, inlet air temperature of 220℃, and outlet air temperature of 90℃.

[0063] The powder was placed in a benchtop powder press and subjected to a pressure of 10 MPa. After holding the pressure for 15 minutes, it was demolded and subjected to UFS sintering. The sintering conditions were: 900℃, 30S. After sintering, LAGP-coated LATP material was obtained.

[0064] 3. Test the ionic and electronic conductivity of LAGP@LATP.

[0065] Take 3g of the above LAGP@LATP material. Gently polish the surface of the ceramic sheet using 1000-grit sandpaper moistened with alcohol, following a cross-hatching method, to remove surface impurities and ensure uniform electrolyte thickness throughout. Measure the thickness L1 of the ceramic sheet using calipers. Deposit a gold blocking electrode using an ion sputtering apparatus. Measure the ionic conductivity of LAGP@LATP using AC impedance spectroscopy and record it as σ1.

[0066] The electronic conductivity of LAGP@LATP was tested based on the principle of the four-probe method for testing powder electronic conductivity. 10g of the above LAGP@LATPF material was added to a powder resistance meter for testing. A pressure of 200MPa was applied, and the electronic conductivity of the sample was measured and recorded as ρ1.

[0067] 4. Test the electrochemical performance of the battery after mixing.

[0068] The above materials were used to prepare CR2032 coin cells. The negative electrode was a lithium sheet, the positive electrode was a high-nickel (811) system, and the electrolyte was a LAGP@LATP ceramic sheet.

[0069] The assembled button cells were subjected to constant current charge-discharge tests on the battery testing system, with a voltage range of 2.5 to 4.25V and a rate of 0.05C.

[0070] Example 2

[0071] 1. Preparation of LATP materials

[0072] Weigh 54.31g of lithium carbonate, 20.39g of aluminum oxide, 127.79g of titanium dioxide, and 333.58g of ammonium dihydrogen phosphate. After mixing the precursors, perform UFS sintering on the precursors under the following conditions: 800℃ for 45s. After sintering, pulverize the precursors into 1μm powder.

[0073] 2. Preparation of LAGP@LATP materials

[0074] After crushing the above materials, add them to a ball mill. Weigh out 15.58g of lithium dihydrogen phosphate, 8.52g of aluminum nitrate, 38.50g of germanium oxalate, and 17.60g of ammonium dihydrogen phosphate. Add deionized water and ball mill to achieve a solid content of 10%. The ball milling speed is 500rpm / h for 3 hours, and the particle size is 200nm.

[0075] The above slurry was spray-dried with the following parameters: centrifugal nozzle speed of 500 rpm / min, inlet air temperature of 220℃, and outlet air temperature of 90℃.

[0076] The powder was placed in a benchtop powder press and subjected to a pressure of 10 MPa. After holding the pressure for 15 minutes, it was demolded and subjected to UFS sintering. The sintering conditions were 800℃ and 30 seconds. After sintering, LAGP-coated LATP material was obtained.

[0077] 3. Test the ionic and electronic conductivity of LAGP@LATP.

[0078] Take 3g of the above LAGP@LATP material. Gently polish the surface of the ceramic sheet using 1000-grit sandpaper moistened with alcohol, following a cross-hatching method, to remove surface impurities and ensure uniform electrolyte thickness throughout. Measure the thickness L1 of the ceramic sheet using calipers. Deposit a gold blocking electrode using an ion sputtering apparatus. Measure the ionic conductivity of LAGP@LATP using AC impedance spectroscopy and record it as σ1.

[0079] The electronic conductivity of LAGP@LATP was tested based on the principle of the four-probe method for testing powder electronic conductivity. 10g of the above LAGP@LATPF material was added to a powder resistance meter for testing. A pressure of 200MPa was applied, and the electronic conductivity of the sample was measured and recorded as ρ1.

[0080] 4. Test the electrochemical performance of the battery after mixing.

[0081] The above materials were used to prepare CR2032 coin cells. The negative electrode was a lithium sheet, the positive electrode was a high-nickel (811) system, and the electrolyte was a LAGP@LATP ceramic sheet.

[0082] The assembled button cells were subjected to constant current charge-discharge tests on the battery testing system, with a voltage range of 2.5 to 4.25V and a rate of 0.05C.

[0083] Example 3

[0084] 1. Preparation of LATP materials

[0085] Weigh 54.31g of lithium carbonate, 20.39g of aluminum oxide, 127.79g of titanium dioxide, and 333.58g of ammonium dihydrogen phosphate. After mixing the precursors, perform UFS sintering on the precursors under the following conditions: 1000℃ for 45s. After sintering, pulverize the precursors into 1μm powder.

[0086] 2. Preparation of LAGP@LATP materials

[0087] After crushing the above materials, add them to a ball mill. Weigh out 15.58g of lithium dihydrogen phosphate, 8.52g of aluminum nitrate, 38.50g of germanium oxalate, and 17.60g of ammonium dihydrogen phosphate. Add deionized water and ball mill to achieve a solid content of 10%. The ball milling speed is 500 rpm / h for 3 hours until a homogeneous solution is obtained.

[0088] The above slurry was spray-dried with the following parameters: centrifugal nozzle speed of 500 rpm / min, inlet air temperature of 220℃, and outlet air temperature of 90℃.

[0089] The powder was placed in a benchtop powder press and subjected to a pressure of 10 MPa. After holding the pressure for 15 minutes, it was demolded and subjected to UFS sintering. The sintering conditions were: 1000℃, 30S. After sintering, LAGP-coated LATP material was obtained.

[0090] 3. Test the ionic and electronic conductivity of LAGP@LATP.

[0091] Take 3g of the above LAGP@LATP material. Gently polish the surface of the ceramic sheet using 1000-grit sandpaper moistened with alcohol, following a cross-hatching method, to remove surface impurities and ensure uniform electrolyte thickness throughout. Measure the thickness L1 of the ceramic sheet using calipers. Deposit a gold blocking electrode using an ion sputtering apparatus. Measure the ionic conductivity of LAGP@LATP using AC impedance spectroscopy and record it as σ1.

[0092] The electronic conductivity of LAGP@LATP was tested based on the principle of the four-probe method for testing powder electronic conductivity. 10g of the above LAGP@LATPF material was added to a powder resistance meter for testing. A pressure of 200MPa was applied, and the electronic conductivity of the sample was measured and recorded as ρ1.

[0093] 4. Test the electrochemical performance of the battery after mixing.

[0094] The above materials were used to prepare CR2032 coin cells. The negative electrode was a lithium sheet, the positive electrode was a high-nickel (811) system, and the electrolyte was a LAGP@LATP ceramic sheet.

[0095] The assembled button cells were subjected to constant current charge-discharge tests on the battery testing system, with a voltage range of 2.5 to 4.25V and a rate of 0.05C.

[0096] Example 4

[0097] 1. Preparation of LATP materials

[0098] Weigh 54.31g of lithium carbonate, 20.39g of aluminum oxide, 127.79g of titanium dioxide, and 333.58g of ammonium dihydrogen phosphate. After mixing the precursors, perform UFS sintering on the precursors under the following conditions: 900℃ for 60s. After sintering, pulverize the precursors into 1μm powder.

[0099] 2. Preparation of LAGP@LATP materials

[0100] After crushing the above materials, add them to a ball mill. Weigh out 15.58g of lithium dihydrogen phosphate, 8.52g of aluminum nitrate, 38.50g of germanium oxalate, and 17.60g of ammonium dihydrogen phosphate. Add deionized water and ball mill to achieve a solid content of 10%. The ball milling speed is 500rpm / h for 3 hours, and the particle size is 200nm.

[0101] The above slurry was spray-dried with the following parameters: centrifugal nozzle speed of 500 rpm / min, inlet air temperature of 220℃, and outlet air temperature of 90℃.

[0102] The powder was placed in a benchtop powder press and subjected to a pressure of 10 MPa. After holding the pressure for 15 minutes, it was demolded and subjected to UFS sintering. The sintering conditions were: 900℃, 45S. After sintering, LAGP-coated LATP material was obtained.

[0103] 3. Test the ionic and electronic conductivity of LAGP@LATP.

[0104] Take 3g of the above LAGP@LATP material. Gently polish the surface of the ceramic sheet using 1000-grit sandpaper moistened with alcohol, following a cross-hatching method, to remove surface impurities and ensure uniform electrolyte thickness throughout. Measure the thickness L1 of the ceramic sheet using calipers. Deposit a gold blocking electrode using an ion sputtering apparatus. Measure the ionic conductivity of LAGP@LATP using AC impedance spectroscopy and record it as σ1.

[0105] The electronic conductivity of LAGP@LATP was tested based on the principle of the four-probe method for testing powder electronic conductivity. 10g of the above LAGP@LATPF material was added to a powder resistance meter for testing. A pressure of 200MPa was applied, and the electronic conductivity of the sample was measured and recorded as ρ1.

[0106] 4. Test the electrochemical performance of the battery after mixing.

[0107] The above materials were used to prepare CR2032 coin cells. The negative electrode was a lithium sheet, the positive electrode was a high-nickel (811) system, and the electrolyte was a LAGP@LATP ceramic sheet.

[0108] The assembled button cells were subjected to constant current charge-discharge tests on the battery testing system, with a voltage range of 2.5 to 4.25V and a rate of 0.05C.

[0109] Comparative Example

[0110] 1. Preparation of LATP materials

[0111] Weigh 54.31g of lithium carbonate, 20.39g of alumina, 127.79g of titanium dioxide, and 333.58g of ammonium dihydrogen phosphate. After mixing the precursors, sinter them in a muffle furnace under the following conditions: 900℃ for 20h. After sintering, pulverize the sintered precursors into 1μm powder.

[0112] 2. Preparation of LAGP@LATP materials

[0113] After crushing the above materials, add them to a ball mill. Weigh out 15.58g of lithium dihydrogen phosphate, 8.52g of aluminum nitrate, 38.50g of germanium oxalate, and 17.60g of ammonium dihydrogen phosphate. The solid content is 10%. The ball milling speed is 500rpm / h for 3 hours, and the particle size is 200nm.

[0114] The above slurry was spray-dried with the following parameters: centrifugal nozzle speed of 500 rpm / min, inlet air temperature of 220℃, and outlet air temperature of 90℃.

[0115] The above powder was placed in a benchtop powder press and subjected to a pressure of 10 MPa. After holding the pressure for 15 minutes, it was demolded and sintered in a muffle furnace under the following conditions: 900℃ for 20 hours. After sintering, LAGP-coated LATP material was obtained.

[0116] 3. Test the ionic and electronic conductivity of LAGP@LATP.

[0117] Take 3g of the above LAGP@LATP material. Gently polish the surface of the ceramic sheet using 1000-grit sandpaper moistened with alcohol, following a cross-hatching method, to remove surface impurities and ensure uniform electrolyte thickness throughout. Measure the thickness L1 of the ceramic sheet using calipers. Deposit a gold blocking electrode using an ion sputtering apparatus. Measure the ionic conductivity of LAGP@LATP using AC impedance spectroscopy and record it as σ1.

[0118] The electronic conductivity of LAGP@LATP was tested based on the principle of the four-probe method for testing powder electronic conductivity. 10g of the above LAGP@LATPF material was added to a powder resistance meter for testing. A pressure of 200MPa was applied, and the electronic conductivity of the sample was measured and recorded as ρ1.

[0119] 4. Test the electrochemical performance of the battery after mixing.

[0120] The above materials were used to prepare CR2032 coin cells. The negative electrode was a lithium sheet, the positive electrode was a high-nickel (811) system, and the electrolyte was a LAGP@LATP ceramic sheet.

[0121] The assembled button cells were subjected to constant current charge-discharge tests, with a voltage range of 2.5–4.25V and a rate of 0.05C. The test results are as follows: Figure 4 As shown, from Figure 4 It can be seen that the comparative charging curve shows a rapid initial voltage increase followed by a slow increase after 3.6V, indicating insufficient internal stability of the battery. The examples show more consistent performance, and their discharge capacity is generally higher than that of the comparative.

[0122] The results of the ionic conductivity test are shown in Table 1.

[0123] Table 1 Ionic Conductivity

[0124]

[0125]

[0126] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a core-shell composite solid electrolyte resistant to lithium anodes, comprising the following steps: A) A porous LATP material is obtained by mixing lithium, aluminum, titanium and phosphorus sources and then sintering them using Joule heating. The lithium source, aluminum source, titanium source and phosphorus source in step A) contain at least one raw material that can generate gas during sintering. B) Dissolve LATP and soluble LAGP preparation raw materials in water, centrifuge and spray dry to obtain LAGP@LATP precursor powder; The raw materials for preparing the soluble LAGP include soluble lithium source, soluble aluminum source, soluble germanium source and soluble phosphorus source; C) The dried powder is pressed to obtain LAGP@LATP precursor ceramic sheets, and then sintered using Joule heating to obtain a core-shell composite solid electrolyte with lithium anode tolerance.

2. The preparation method according to claim 1, characterized in that, In step A), the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium bicarbonate, and lithium oxide; the aluminum source is aluminum oxide and / or aluminum hydroxide; the titanium source is titanium trioxide and / or titanium dioxide; and the phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

3. The preparation method according to claim 1, characterized in that, The Joule heating temperature in step A) is 800–1000°C; the sintering time in step A) is 30–120 s.

4. The preparation method according to claim 1, characterized in that, The mass of the soluble LAGP preparation raw material accounts for 5-10% of the total mass of LATP and the soluble LAGP preparation raw material.

5. The preparation method according to claim 1, characterized in that, In step B), the inlet temperature of the centrifugal spray dryer is 220-280°C, the outlet temperature is 85-100°C, and the centrifugal nozzle speed is 500-800 rpm.

6. The preparation method according to claim 1, characterized in that, The pressing pressure in step C) is 5-15 MPa, and the holding time is 10-20 min.

7. The preparation method according to claim 1, characterized in that, The Joule heating temperature in step C) is 800–1000°C; the sintering time in step C) is 30–90 seconds.

8. A core-shell composite solid electrolyte resistant to lithium anodes, prepared according to the preparation method described in any one of claims 1 to 7; The core-shell composite solid electrolyte with lithium-resistant anode has a porous LATP core and a dense LAGP shell layer. The porosity of the LATP core is 25-40%, and the porosity of the LAGP shell layer is ≤5%.

9. The core-shell composite solid electrolyte with lithium anode tolerance according to claim 8, characterized in that, In the LATP core, the volume fraction of LATP decreases from 75-85% to 45-55% from the inside out.

10. A fully solid-state lithium battery, characterized in that, Includes positive electrode, solid electrolyte and lithium negative electrode; The solid electrolyte is the core-shell structured composite solid electrolyte with lithium-resistant anode as described in claim 8 or 9.

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