Core-shell structure composite solid electrolyte tolerant to lithium negative electrode as well as preparation method and application of core-shell structure composite solid electrolyte

Abstract

The invention provides a lithium-negative-electrode-tolerant core-shell structure composite solid electrolyte and a preparation method and application thereof.The preparation method comprises the following steps that A, a lithium source, an aluminum source, a titanium source and a phosphorus source are mixed and then sintered through Joule heating, and a porous LATP material is obtained; the lithium source, the aluminum source, the titanium source and the phosphorus source in the step A) comprise at least one raw material capable of generating gas in the sintering process; b) dissolving LATP and a soluble LAGP raw material in water, and performing centrifugal spray drying to obtain LAGP coated LATP precursor powder; and C) pressing the dried powder. The LATP material with the multi-gradient core-shell composite structure, designed based on the invention, has the characteristics of high ionic conductivity, stable material structure, lithium negative electrode tolerance and the like; the method can be applied to an all-solid-state lithium negative electrode battery and is used for improving the performance and stability of the battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-solid-state lithium batteries, and in particular relates to a core-shell composite solid electrolyte resistant to lithium negative electrodes, a preparation method thereof, and applications thereof. Background Art

[0002] In modern society, batteries are crucial for powering many devices, including 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 the way we live and work, from achieving sustainable energy to reducing dependence on fossil fuels. Unfortunately, lithium-ion batteries face safety issues and challenges in further improving their energy density. Therefore, intensified research in battery technology is imperative. Oxide inorganic solid electrolytes have high ionic conductivity, providing a stable and efficient transport medium for ion flow between the anode and cathode in batteries. Furthermore, solid electrolytes prevent side reactions between the electrodes and the electrolyte, thereby avoiding the formation of dendrites and improving the overall energy density of the battery. For example, LATPs possess favorable properties such as high ionic conductivity, chemical stability, and low reactivity with lithium metal anodes. They hold great potential for advancing the energy storage field 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 the highly reducing lithium negative electrode, the valence of titanium will change, causing the entire crystal structure to change, which can easily cause battery stability problems. Summary of the Invention

[0004] The present invention provides a core-shell structure composite solid electrolyte that is resistant to lithium negative electrodes, as well as a preparation method and application thereof. The core-shell structure composite solid electrolyte in the present invention has high ionic conductivity, is resistant to lithium negative electrodes, and has good material stability, and can improve the stability of all-solid-state lithium batteries.

[0005] A method for preparing a core-shell structure composite solid electrolyte resistant to lithium negative electrodes comprises the following steps:

[0006] 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;

[0007] The lithium source, aluminum source, titanium source and phosphorus source in step A) include at least one raw material capable of generating gas during the sintering process;

[0008] B) dissolving LATP and soluble LAGP preparation raw materials in water, and centrifugally spray-drying to obtain LAGP@LATP precursor powder;

[0009] The soluble LAGP preparation raw materials include a soluble lithium source, a soluble aluminum source, a soluble germanium source and a soluble phosphorus source;

[0010] C) pressing the dried powder to obtain a LAGP@LATP precursor ceramic sheet, and then sintering it using Joule heating to obtain a core-shell structure composite solid electrolyte that is resistant to lithium negative electrodes.

[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 diammonium hydrogen phosphate.

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

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

[0014] Preferably, in step B), the air inlet temperature of the centrifugal spray drying is 220-280° C., the air 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 to 15 MPa, and the holding time is 10 to 20 minutes.

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

[0017] The present invention provides a core-shell structure composite solid electrolyte resistant to lithium negative electrode, which is prepared according to the preparation method described above;

[0018] The core-shell structure composite solid electrolyte tolerant to lithium negative electrodes comprises 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 gradually from 75-85% to 45-55% from the inside to the outside.

[0020] The present 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 composite solid electrolyte that is resistant to lithium negative electrodes as described above.

[0022] The present invention provides a method for preparing a core-shell structure composite solid electrolyte resistant to lithium negative electrodes, comprising the following steps: A) mixing a lithium source, an aluminum source, a titanium source, and a phosphorus source, and sintering the mixture using Joule heating to obtain a porous LATP material; wherein the lithium source, the aluminum source, the titanium source, and the phosphorus source in step A) include at least one raw material capable of generating gas during the sintering process; B) dissolving LATP and a soluble LAGP raw material in water, and centrifugally spray drying the mixture to obtain an 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; and C) pressing the dried powder to obtain an LAGP@LATP precursor ceramic sheet, and then sintering the sheet using Joule heating to obtain a core-shell structure composite solid electrolyte resistant to lithium negative electrodes. The present invention prepares LATP with a multi-gradient core-shell composite structure by a method of in-situ synthesis of various nanoscale raw materials on the surface of LATP, and then directly and rapidly synthesizes an oxide solid electrolyte layer without a variable valence element on the surface of LATP through Joule heating (UFS). Its chemical properties are relatively stable, the solid-solid reaction interface impedance becomes smaller, and it can tolerate the high reducibility of the lithium negative electrode, and the core and the outer shell have a certain ionic conductivity, which reduces the content of non-ionic conductivity substances in the all-solid-state battery and improves its energy density. Taken together, the LATP material with a multi-gradient core-shell composite structure designed based on the present invention has the characteristics of high ionic conductivity, stable material structure, and tolerance to lithium negative electrode; it can be applied to all-solid-state lithium negative electrode batteries to improve battery performance and stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0024] Figure 1 Schematic diagram of the structure of the LAGP@LATP composite electrolyte material in the present invention,

[0025] Figure 1 In the figure, 1 is the porous LATP material, 2 is the LAGP@LATP precursor, and 3 is the LAGP@LATP composite electrolyte material;

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

[0027] Figure 3 This is the XRD pattern of the LAGP@LATP composite electrolyte material of Example 2 of the present invention;

[0028] Figure 4 These are the charge and discharge test curves of the batteries in Examples 1 to 4 and the comparative example. DETAILED DESCRIPTION

[0029] The present invention provides a method for preparing a core-shell structure composite solid electrolyte resistant to lithium negative electrodes, comprising the following steps:

[0030] 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;

[0031] The lithium source, aluminum source, titanium source and phosphorus source in step A) include at least one raw material capable of generating gas during the sintering process;

[0032] B) dissolving LATP and soluble LAGP raw materials in water and centrifugally spray-drying to obtain LAGP@LATP precursor powder;

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

[0034] C) pressing the dried powder to obtain a LAGP@LATP precursor ceramic sheet, and then sintering it using Joule heating to obtain a core-shell structure composite solid electrolyte that is resistant to lithium negative electrodes.

[0035] In the present 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 raw material that can generate volatile gases (such as CO2, NH3, etc.) during the sintering process is included, 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 aluminum oxide and / or aluminum hydroxide; the titanium source is preferably titanium trioxide and / or titanium dioxide; the phosphorus source is one or more of phosphoric acid, ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

[0036] In the present invention, the lithium source, aluminum source, titanium source and phosphorus source are mixed according to the stoichiometric ratio of LATP (lithium aluminum titanium phosphate). The present invention preferably grinds and mixes the lithium source, aluminum source, titanium source and phosphorus source. Specifically, the present invention disperses the lithium source, aluminum source, titanium source and phosphorus source in a solvent, adds grinding media, and uses grinding balls for grinding.

[0037] In the present 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 (grinding ball mass: powder mass) in the grinding is preferably 5-20.

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

[0039] In the present invention, the slurry is preferably dried at a temperature of 80 to 120°C, more preferably 100 to 110°C, and after drying, is passed through an 80 to 400 mesh sieve to obtain a core precursor powder. The present invention sinters the LATP material by Joule heating and selects raw materials that can generate gas during the sintering process, thereby obtaining a multi-gradient porous LATP material as the core of the solid electrolyte and reducing lithium loss.

[0040] In the present invention, the temperature of the Joule heating 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, and preferably a range value with the above arbitrary numerical values ​​as the upper or lower limit; the holding time of the sintering is preferably 30-120s, more preferably 50-100s, such as 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s, 120s, and preferably a range value with the above arbitrary numerical values ​​as the upper or lower limit.

[0041] After obtaining the LATP powder, the present invention stirs and dissolves the LATP powder and a water-soluble LAGP preparation raw material in water, dries the powder into powder by centrifugal spraying, and then presses the powder to obtain a ceramic sheet of the LAGP@LATP precursor.

[0042] In the present 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; and the soluble phosphorus source is preferably one or more of phosphoric acid, ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

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

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

[0045] The obtained ceramic sheet of LAGP@LATP precursor was sintered using Joule heating to obtain a core-shell structure composite solid electrolyte that is resistant to lithium negative electrode.

[0046] In the present invention, the temperature of the Joule heating 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, and preferably a range value with any of the above numerical values ​​as the upper or lower limit; the holding time of the sintering is preferably 30-90s, more preferably 50-80s, such as 30s, 40s, 50s, 60s, 70s, 80s, 90s, and preferably a range value with any of the above numerical values ​​as the upper or lower limit.

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

[0048] The core-shell structure composite solid electrolyte tolerant to lithium negative electrodes comprises 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 the present invention, in the LATP core, the LATP volume fraction decreases gradually from 75% to 85% to 45% to 55% from the inside to the outside, and the gradient transition slope is 0.5 to 2% / μm; the porosity of the LATP core is preferably 25 to 40%, more preferably 30 to 35%; the pore diameter is preferably 200 to 800 nm, and the pore aspect ratio is preferably 3:1 to 8:1, more preferably 4:1 to 6:1.

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

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

[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 composite solid electrolyte that is resistant to lithium negative electrodes as described above.

[0054] In the present invention, the positive electrode preferably includes a positive electrode current collector and a positive electrode coating composited on the surface of the positive electrode 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, lithium nickel manganese 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 boasts a short sintering time, is free of non-conductive impurities, and exhibits high ionic conductivity, a stable material structure, and tolerance to lithium anodes. Its application in batteries can improve battery energy density, safety, and stability. The material utilizes readily available, inexpensive raw materials, resulting in low cost and a simple process, making it amenable to large-scale industrialization.

[0056] To further illustrate the present invention, the following detailed description of a core-shell composite solid electrolyte tolerant to lithium negative electrodes, its preparation method and application is provided by the present invention in combination with examples, but it should not be understood as limiting the scope of protection of the present invention.

[0057] Example 1

[0058] 1. Preparation of LATP materials

[0059] Weigh 54.31 g of lithium carbonate, 20.39 g of aluminum oxide, 127.79 g of titanium dioxide, and 333.58 g of ammonium dihydrogen phosphate. After the precursors are mixed, perform UFS sintering on the precursors. The sintering conditions are: 900° C., 45 seconds. After sintering, crush them into 1 μm powder.

[0060] 2. Preparation of LAGP@LATP materials

[0061] The above materials were crushed and added to a ball mill. 15.58 g of lithium dihydrogen phosphate, 8.52 g of aluminum nitrate, 38.50 g of germanium oxalate, and 17.60 g of ammonium dihydrogen phosphate were weighed and ball-milled with deionized water. The solid content was 10%, the ball milling speed was 500 rpm / h, and the process lasted for 3 h. The particle size was 200 nm.

[0062] The slurry was spray dried, and the spray setting parameters were: centrifugal nozzle speed of 500 rpm / min, air inlet temperature of 220°C, and air outlet temperature of 90°C.

[0063] The above powder was placed in a desktop powder tablet press and subjected to a pressure of 10 MPa. After maintaining the pressure for 15 minutes, the powder was demolded and subjected to UFS sintering. The sintering conditions were: 900°C, 30 seconds. After sintering, the LAGP-coated LATP material was obtained.

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

[0065] Take 3g of the LAGP@LATP material. Lightly polish the surface of the ceramic sheet using 1000-grit sandpaper moistened with alcohol using a cross-section technique to remove surface impurities and ensure uniform electrolyte thickness across the board. Measure the thickness L1 of the ceramic sheet using a vernier caliper. Then, use an ion sputtering instrument to deposit a gold blocking electrode. The ionic conductivity of the LAGP@LATP is measured using an AC impedance test, denoted as σ1.

[0066] The electronic conductivity of LAGP@LATP was measured using the four-probe method. 10g of the LAGP@LATPF material was placed in a powder resistance tester. The sample was pressurized to 200 MPa and its electronic conductivity, recorded as ρ1, was measured.

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

[0068] The above materials were prepared into CR2032 button batteries, wherein 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 cell was subjected to constant current charge and discharge tests on the battery testing system, with a voltage range of 2.5 to 4.25 V and a rate of 0.05C.

[0070] Example 2

[0071] 1. Preparation of LATP materials

[0072] Weigh 54.31 g of lithium carbonate, 20.39 g of aluminum oxide, 127.79 g of titanium dioxide, and 333.58 g of ammonium dihydrogen phosphate. After the precursors are mixed, perform UFS sintering on the precursors. The sintering conditions are: 800° C., 45 seconds. After sintering, crush them into 1 μm powder.

[0073] 2. Preparation of LAGP@LATP materials

[0074] The above materials were crushed and added to a ball mill. 15.58 g of lithium dihydrogen phosphate, 8.52 g of aluminum nitrate, 38.50 g of germanium oxalate, and 17.60 g of ammonium dihydrogen phosphate were weighed and ball-milled with deionized water. The solid content was 10%, the ball milling speed was 500 rpm / h, and the process lasted for 3 h. The particle size was 200 nm.

[0075] The slurry was spray dried, and the spray setting parameters were: centrifugal nozzle speed of 500 rpm / min, air inlet temperature of 220°C, and air outlet temperature of 90°C.

[0076] The above powder was placed in a desktop powder tablet press and subjected to a pressure of 10 MPa. After maintaining the pressure for 15 minutes, the powder was demolded and subjected to UFS sintering. The sintering conditions were: 800°C, 30 seconds. After sintering, the LAGP-coated LATP material was obtained.

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

[0078] Take 3g of the LAGP@LATP material. Lightly polish the surface of the ceramic sheet using 1000-grit sandpaper moistened with alcohol using a cross-section technique to remove surface impurities and ensure uniform electrolyte thickness across the board. Measure the thickness L1 of the ceramic sheet using a vernier caliper. Then, use an ion sputtering instrument to deposit a gold blocking electrode. The ionic conductivity of the LAGP@LATP is measured using an AC impedance test, denoted as σ1.

[0079] The electronic conductivity of LAGP@LATP was measured using the four-probe method. 10g of the LAGP@LATPF material was placed in a powder resistance tester. The sample was pressurized to 200 MPa and its electronic conductivity, recorded as ρ1, was measured.

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

[0081] The above materials were prepared into CR2032 button batteries, wherein 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 cell was subjected to constant current charge and discharge tests on the battery testing system, with a voltage range of 2.5 to 4.25 V and a rate of 0.05C.

[0083] Example 3

[0084] 1. Preparation of LATP materials

[0085] Weigh 54.31 g of lithium carbonate, 20.39 g of aluminum oxide, 127.79 g of titanium dioxide, and 333.58 g of ammonium dihydrogen phosphate. After the precursors are mixed, perform UFS sintering on the precursors. The sintering conditions are: 1000° C., 45 seconds. After sintering, crush them into 1 μm powder.

[0086] 2. Preparation of LAGP@LATP materials

[0087] The above materials were crushed and added to a ball mill. 15.58 g of lithium dihydrogen phosphate, 8.52 g of aluminum nitrate, 38.50 g of germanium oxalate, and 17.60 g of ammonium dihydrogen phosphate were weighed and ball-milled with deionized water. The solid content was 10%, and the ball milling speed was 500 rpm / h for 3 h until a uniform solution was obtained.

[0088] The slurry was spray dried, and the spray setting parameters were: centrifugal nozzle speed of 500 rpm / min, air inlet temperature of 220°C, and air outlet temperature of 90°C.

[0089] The above powder was placed in a desktop powder tablet press and subjected to a pressure of 10 MPa. After maintaining the pressure for 15 minutes, the powder was demolded and subjected to UFS sintering. The sintering conditions were: 1000°C, 30 seconds. After sintering, the LAGP-coated LATP material was obtained.

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

[0091] Take 3g of the LAGP@LATP material. Lightly polish the surface of the ceramic sheet using 1000-grit sandpaper moistened with alcohol using a cross-section technique to remove surface impurities and ensure uniform electrolyte thickness across the board. Measure the thickness L1 of the ceramic sheet using a vernier caliper. Then, use an ion sputtering instrument to deposit a gold blocking electrode. The ionic conductivity of the LAGP@LATP is measured using an AC impedance test, denoted as σ1.

[0092] The electronic conductivity of LAGP@LATP was measured using the four-probe method. 10g of the LAGP@LATPF material was placed in a powder resistance tester. The sample was pressurized to 200 MPa and its electronic conductivity, recorded as ρ1, was measured.

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

[0094] The above materials were prepared into CR2032 button batteries, wherein 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 cell was subjected to constant current charge and discharge tests on the battery testing system, with a voltage range of 2.5 to 4.25 V and a rate of 0.05C.

[0096] Example 4

[0097] 1. Preparation of LATP materials

[0098] Weigh 54.31 g of lithium carbonate, 20.39 g of aluminum oxide, 127.79 g of titanium dioxide, and 333.58 g of ammonium dihydrogen phosphate. After the precursors are mixed, perform UFS sintering on the precursors. The sintering conditions are: 900° C., 60 s. After sintering, crush them into 1 μm powder.

[0099] 2. Preparation of LAGP@LATP materials

[0100] The above materials were crushed and added to a ball mill. 15.58 g of lithium dihydrogen phosphate, 8.52 g of aluminum nitrate, 38.50 g of germanium oxalate, and 17.60 g of ammonium dihydrogen phosphate were weighed and ball-milled with deionized water. The solid content was 10%, the ball milling speed was 500 rpm / h, and the process lasted for 3 h. The particle size was 200 nm.

[0101] The slurry was spray dried, and the spray setting parameters were: centrifugal nozzle speed of 500 rpm / min, air inlet temperature of 220°C, and air outlet temperature of 90°C.

[0102] The above powder was placed in a desktop powder tablet press and subjected to a pressure of 10 MPa. After maintaining the pressure for 15 minutes, the powder was demolded and subjected to UFS sintering. The sintering conditions were: 900°C, 45 seconds. After sintering, the LAGP-coated LATP material was obtained.

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

[0104] Take 3g of the LAGP@LATP material. Lightly polish the surface of the ceramic sheet using 1000-grit sandpaper moistened with alcohol using a cross-section technique to remove surface impurities and ensure uniform electrolyte thickness across the board. Measure the thickness L1 of the ceramic sheet using a vernier caliper. Then, use an ion sputtering instrument to deposit a gold blocking electrode. The ionic conductivity of the LAGP@LATP is measured using an AC impedance test, denoted as σ1.

[0105] The electronic conductivity of LAGP@LATP was measured using the four-probe method. 10g of the LAGP@LATPF material was placed in a powder resistance tester. The sample was pressurized to 200 MPa and its electronic conductivity, recorded as ρ1, was measured.

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

[0107] The above materials were prepared into CR2032 button batteries, wherein 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 cell was subjected to constant current charge and discharge tests on the battery testing system, with a voltage range of 2.5 to 4.25 V and a rate of 0.05C.

[0109] Comparative Example

[0110] 1. Preparation of LATP materials

[0111] Weigh 54.31 g of lithium carbonate, 20.39 g of aluminum oxide, 127.79 g of titanium dioxide, and 333.58 g of ammonium dihydrogen phosphate. After the precursors are mixed, they are sintered in a muffle furnace under the sintering conditions of 900° C. for 20 h. After sintering, the precursors are crushed into 1 μm powder.

[0112] 2. Preparation of LAGP@LATP materials

[0113] The above materials were crushed and added to a ball mill. 15.58 g of lithium dihydrogen phosphate, 8.52 g of aluminum nitrate, 38.50 g of germanium oxalate, and 17.60 g of ammonium dihydrogen phosphate were weighed. The solid content was 10%. The ball milling speed was 500 rpm / h for 3 hours. The particle size was 200 nm.

[0114] The slurry was spray dried, and the spray setting parameters were: centrifugal nozzle speed of 500 rpm / min, air inlet temperature of 220°C, and air outlet temperature of 90°C.

[0115] The above powder was placed in a desktop powder tablet press and subjected to a pressure of 10 MPa. After maintaining the pressure for 15 minutes, the powder was demoulded and sintered in a muffle furnace. The sintering conditions were: 900°C, 20 hours. After sintering, the LAGP-coated LATP material was obtained.

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

[0117] Take 3g of the LAGP@LATP material. Lightly polish the surface of the ceramic sheet using 1000-grit sandpaper moistened with alcohol using a cross-section technique to remove surface impurities and ensure uniform electrolyte thickness across the board. Measure the thickness L1 of the ceramic sheet using a vernier caliper. Then, use an ion sputtering instrument to deposit a gold blocking electrode. The ionic conductivity of the LAGP@LATP is measured using an AC impedance test, denoted as σ1.

[0118] The electronic conductivity of LAGP@LATP was measured using the four-probe method. 10g of the LAGP@LATPF material was placed in a powder resistance tester. The sample was pressurized to 200 MPa and its electronic conductivity, recorded as ρ1, was measured.

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

[0120] The above materials were prepared into CR2032 button batteries, wherein 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 cell was tested for constant current charge and discharge with a voltage range of 2.5 to 4.25 V and a rate of 0.05 C. The test results are as follows: Figure 4 As shown, from Figure 4 It can be seen that the charge curve of the comparative example shows a rapid increase in voltage after 3.6V, followed by a slow increase, which indicates that the battery is not stable. The performance of the examples is relatively consistent, and the discharge capacity is generally higher than that of the comparative example.

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

[0123] Table 1 Ionic conductivity

[0124]

[0125]

[0126] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a core-shell structure composite solid electrolyte resistant to lithium negative electrode, 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; The lithium source, aluminum source, titanium source and phosphorus source in step A) include at least one raw material capable of generating gas during the sintering process; B) dissolving LATP and soluble LAGP preparation raw materials in water, and centrifugally spray-drying to obtain LAGP@LATP precursor powder; The soluble LAGP preparation raw materials include a soluble lithium source, a soluble aluminum source, a soluble germanium source and a soluble phosphorus source; C) pressing the dried powder to obtain a LAGP@LATP precursor ceramic sheet, and then sintering it using Joule heating to obtain a core-shell structure composite solid electrolyte that is resistant to lithium negative electrodes.

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 temperature of Joule heating in step A) is 800-1000° C.; and the time of sintering in step A) is 30-120 seconds.

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

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

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

8. A core-shell composite solid electrolyte resistant to lithium negative electrodes, prepared according to the preparation method according to any one of claims 1 to 7; The core-shell structure composite solid electrolyte tolerant to lithium negative electrodes comprises 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 structure composite solid electrolyte resistant to lithium negative electrode according to claim 8, characterized in that: In the LATP core, the volume fraction of LATP decreases gradually from 75-85% to 45-55% from the inside to the outside.

10. An all-solid-state lithium battery, characterized in that: Including positive electrode, solid electrolyte and lithium negative electrode; The solid electrolyte is the core-shell structure composite solid electrolyte that tolerates lithium negative electrode according to claim 8 or 9.

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