Garnet type solid electrolyte as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of solid electrolyte materials, and particularly relates to a garnet type solid electrolyte and a preparation method and application thereof. The D50 of the garnet type solid electrolyte is less than 300nm, and the specific surface area of the garnet type solid electrolyte is 2-30m < 2 > / g. The garnet type solid electrolyte has the beneficial effects that the garnet type solid electrolyte has irregular spherical morphology, good particle dispersity, uniform granularity and relatively small particle size, and has a wide application prospect, especially in the field of lithium ion solid-state battery manufacturing; the preparation method of the garnet type solid electrolyte is high in controllability, simple and convenient to operate and low in manufacturing cost, and the whole preparation reaction process is carried out under low-temperature and normal-pressure conditions, so that the preparation method is energy-saving and environment-friendly.

Description

Technical Field

[0001] This application belongs to the field of solid electrolyte materials technology, specifically relating to a garnet-type solid electrolyte, its preparation method, and its application. Background Technology

[0002] With the widespread application of lithium-ion batteries, the requirements for their safety and stability are becoming increasingly stringent. Traditional liquid electrolytes, as the core component for lithium-ion battery transfer between electrodes, largely determine the performance of lithium-ion batteries. However, liquid organic electrolytes are currently widely used, which pose safety issues such as leakage, flammability, and explosion. Replacing liquid electrolytes with solid-state electrolytes can effectively avoid these safety problems, making solid-state batteries a crucial future development trend for lithium batteries. Lithium lanthanum zirconium oxide (LLZO) has become a key material of interest for many solid-state electrolyte researchers due to its excellent electrochemical performance. Cubic LLZO exhibits high ionic conductivity and good stability at room temperature. However, the abnormally large grain size and poor grain structure of LLZO electrolytes obtained by solid-state methods are a major obstacle to its widespread application in lithium-ion batteries. Furthermore, the high operating costs of current related materials cannot meet the requirements for large-scale applications. The preparation and structural control of high-quality, highly conductive, pure crystalline phase, small-particle-size, uniformly doped lithium lanthanum zirconium oxide (LLZO) solid-state electrolyte materials are key technical challenges determining the application of solid-state electrolytes. Summary of the Invention

[0003] This application provides a garnet-type solid electrolyte, its preparation method, and its application, aiming to solve the problems of large grains, poor quality structure, and high manufacturing cost of existing solid electrolytes.

[0004] The first aspect of this application provides a garnet-type solid electrolyte, wherein the garnet-type solid electrolyte has a D50 < 300 nm and a specific surface area of ​​2-30 m². 2 / g.

[0005] The garnet-type solid electrolyte described in this application has an irregular spherical morphology, good particle dispersion, uniform particle size, and small particle size, and has broad application prospects, especially in the field of lithium-ion solid battery manufacturing.

[0006] The second aspect of this application provides a composition for preparing the garnet-type solid electrolyte described in the first aspect of this application, comprising zirconium salt, lanthanum salt, lithium salt, alkaline substance, dopant element salt, and hydroxycarboxylic acid.

[0007] According to some embodiments of the composition for preparing garnet-type solid electrolytes described in this application, the zirconium salt includes one or more of zirconium oxynitrate, zirconium oxychloride, zirconium nitrate, and zirconium oxysulfate.

[0008] According to some embodiments of the compositions for preparing garnet-type solid electrolytes described in this application, the lanthanum salt includes lanthanum nitrate and / or lanthanum chloride.

[0009] According to some embodiments of the composition for preparing garnet-type solid electrolytes described in this application, the lithium salt includes lithium carbonate.

[0010] According to some embodiments of the composition for preparing garnet-type solid electrolytes described in this application, the alkaline substance includes ammonia and / or sodium hydroxide.

[0011] According to some embodiments of the composition for preparing garnet-type solid electrolytes described in this application, the doping element salt includes one or more rare earth salts, aluminum salts, and gallium salts that are adapted to the lithium lanthanum zirconium oxide crystal phase structure.

[0012] According to some embodiments of the composition for preparing garnet-type solid electrolytes described in this application, the doping element salt includes one or more of yttrium nitrate, cerium nitrate, gadolinium nitrate, neodymium nitrate, aluminum nitrate, and gallium nitrate; more preferably, the doping element salt includes aluminum nitrate and / or gallium nitrate.

[0013] According to some embodiments of the composition for preparing garnet-type solid electrolytes described in this application, the hydroxycarboxylic acid includes hydroxycarboxylic acids having 2-5 carbon atoms.

[0014] According to some embodiments of the composition for preparing garnet-type solid electrolytes described in this application, the hydroxycarboxylic acid includes one or more of oxalic acid, citric acid, lactic acid, malic acid, and tartaric acid, and more preferably, the hydroxycarboxylic acid includes citric acid and / or tartaric acid.

[0015] According to some embodiments of the composition for preparing garnet-type solid electrolytes described in this application, the molar ratio of the zirconium salt to the lanthanum salt is 2:(3-5).

[0016] According to some embodiments of the composition for preparing garnet-type solid electrolytes described in this application, the molar ratio of the zirconium salt to the lithium salt is 1:(5-10).

[0017] According to some embodiments of the composition for preparing garnet-type solid electrolytes described in this application, the molar ratio of the zirconium salt to the alkaline substance is 1:(1.5-2).

[0018] According to some embodiments of the composition for preparing garnet-type solid electrolytes described in this application, the molar ratio of the zirconium salt to the dopant element salt is 1:(0.02-0.3).

[0019] According to some embodiments of the composition for preparing garnet-type solid electrolytes described in this application, the molar ratio of the zirconium salt to the hydroxycarboxylic acid is 1:(1-3).

[0020] The third aspect of this application provides a method for preparing the garnet-type solid electrolyte described in the first aspect of this application, using the composition described in the second aspect of this application.

[0021] According to some embodiments of the preparation method of the garnet-type solid electrolyte described in this application, the method includes the following steps: (1) A white precipitate was obtained by mixing zirconium salt, lanthanum salt, alkaline substance and solvent; (2) The white precipitate, the doped element salt, the hydroxycarboxylic acid and the solvent are mixed to obtain a precipitate mixture solution; the precipitate mixture solution is centrifuged, washed, dried and calcined to obtain a solid powder; (3) The solid powder and lithium salt are mixed and ball-milled, and the ball-milled material is calcined to obtain the garnet-type solid electrolyte.

[0022] The method for preparing the garnet-type solid electrolyte described in this application involves a precipitation-precursor substitution-organic acid coordination-precipitation process. In this reaction system, alkaline substances are initially selected to obtain precursor zirconium salt and lanthanum salt hydroxides. Then, under the coordination of organic hydroxy acids, these hydroxides react synchronously with dopant ions to generate a mixed sol precipitate of organic acid zirconium lanthanum containing dopant ions. Subsequently, gas-state pulverization effectively removes particle agglomeration in the product and controls the particle size distribution. Ball milling is then used to achieve thorough mixing of small-diameter solid particles with lithium salts. Finally, high-temperature treatment yields a highly conductive, pure crystalline phase, small-diameter, uniformly doped lithium lanthanum zirconium oxide (LLZO) solid electrolyte material.

[0023] According to some embodiments of the method for preparing garnet-type solid electrolytes described in this application, the solvents in steps (1) and (2) each independently include one or more of water, methanol, and ethanol.

[0024] According to some embodiments of the preparation method of garnet-type solid electrolyte described in this application, in step (1), the mixing temperature is 25-40°C and the mixing time is 8-12h.

[0025] According to some embodiments of the preparation method of garnet-type solid electrolyte described in this application, in step (2), the mixing temperature is 60-80℃ and the mixing time is 4-10h.

[0026] According to some embodiments of the preparation method of garnet-type solid electrolyte described in this application, in step (2), the washing includes washing with an organic alcohol; preferably, the organic alcohol includes one or more of ethanol, propanol, isopropanol and n-butanol.

[0027] According to some embodiments of the preparation method of garnet-type solid electrolyte described in this application, in step (2), the drying temperature is 50-150℃ and the drying time is 6-12h.

[0028] According to some embodiments of the preparation method of garnet-type solid electrolyte described in this application, in step (2), the calcination temperature is 800-1000℃ and the calcination time is 6-10h.

[0029] According to some embodiments of the preparation method of garnet-type solid electrolyte described in this application, in step (3), the calcination temperature is 1000-1200℃ and the calcination time is 4-10h.

[0030] The fourth aspect of this application provides the application of the garnet-type solid electrolyte described in the first aspect of this application or the garnet-type solid electrolyte obtained by the preparation method described in the third aspect of this application in lithium-ion batteries.

[0031] The beneficial effects of this application include: the garnet-type solid electrolyte described in this application has an irregular spherical morphology, good particle dispersion, uniform particle size, and small particle size, and has broad application prospects, especially in the field of lithium-ion solid battery manufacturing.

[0032] The preparation method of the garnet-type solid electrolyte described in this application is highly controllable, simple and convenient to operate, and has low production cost. Moreover, the entire preparation reaction process is carried out under low temperature and normal pressure conditions, which is energy-saving and environmentally friendly. Attached Figure Description

[0033] Figure 1 This is a SEM image of the garnet-type solid electrolyte described in Example 1 of this application; Figure 2 This is an X-ray spectrum of the garnet-type solid electrolyte described in Example 1 of this application. Detailed Implementation

[0034] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0035] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0036] This application provides a garnet-type solid electrolyte with a D50 < 300 nm and a specific surface area of ​​2-30 m². 2 / g.

[0037] The garnet-type solid electrolyte described in this application has an irregular spherical morphology, good particle dispersion, uniform particle size, and small particle size, and has broad application prospects, especially in the field of lithium-ion solid battery manufacturing.

[0038] The garnet-type solid electrolyte described in this application is an irregularly shaped pure cubic phase garnet-type crystal structure uniformly doped lithium lanthanum zirconium oxide (LLZO) solid electrolyte material with a particle size of 50-300 nm. After drying and pulverizing, the particle size (D50) is less than 300 nm.

[0039] This application also provides a composition for preparing the garnet-type solid electrolyte described in the first aspect of this application, comprising zirconium salt, lanthanum salt, lithium salt, alkaline substance, dopant element salt, and hydroxycarboxylic acid. The dopant ions in the composition of this application can generate more lattice mismatches and defects in the solid electrolyte, which is beneficial to improving the conductivity of the electrolyte and providing more insertion sites for lithium ions. The hydroxycarboxylic acid used in the preparation process has a certain coordination ability and can coordinate with various metal ions, effectively contributing to the preparation of a pure crystal phase and uniform elemental distribution.

[0040] In some embodiments of this application, the zirconium salt includes one or more of zirconium oxynitrate, zirconium oxychloride, zirconium nitrate, and zirconium oxysulfate; the zirconium salt selected in the embodiments of this application is any compound that can provide zirconium ions or zirconium oxide ions after dissolving in water.

[0041] In some embodiments of this application, the lanthanum salt includes lanthanum nitrate and / or lanthanum chloride; the lanthanum salt selected in the embodiments of this application is any compound that can provide lanthanum ions after dissolving in water.

[0042] In some embodiments of this application, the lithium salt includes lithium carbonate; the lithium carbonate selected in the embodiments of this application is a lithium carbonate chemical with a certain mass content and purity, and the purity is above industrial grade.

[0043] In some embodiments of this application, the alkaline substance includes ammonia and / or sodium hydroxide. The addition of the alkaline substance converts the zirconium salt and lanthanum salt into hydroxides.

[0044] In some embodiments of this application, the doping element salt includes one or more of rare earth salts, aluminum salts, and gallium salts that are compatible with the lithium lanthanum zirconium oxide crystal phase structure. By introducing doping ions, more lattice mismatches and defects can be generated in the solid electrolyte, which is beneficial to improving the conductivity of the solid electrolyte and providing more insertion sites for lithium ions.

[0045] In some embodiments of this application, the doped element salt includes one or more of yttrium nitrate, cerium nitrate, gadolinium nitrate, neodymium nitrate, aluminum nitrate, and gallium nitrate.

[0046] In some embodiments of this application, the doping element salt is aluminum nitrate and / or gallium nitrate.

[0047] In some embodiments of this application, the hydroxycarboxylic acid includes hydroxycarboxylic acids with 2-5 carbon atoms. The hydroxycarboxylic acid used in the preparation process has a certain coordination ability and can coordinate with various metal ions, which effectively helps to prepare crystal phase purity and uniform element distribution.

[0048] In some embodiments of this application, the hydroxycarboxylic acid includes one or more of oxalic acid, citric acid, lactic acid, malic acid, and tartaric acid.

[0049] In some embodiments of this application, the hydroxycarboxylic acid includes citric acid and / or tartaric acid.

[0050] In some embodiments of this application, the molar ratio of the zirconium salt to the lanthanum salt is 2:(3-5); for example, 2:3, 2:4, 2:5, etc.

[0051] In some embodiments of this application, the molar ratio of the zirconium salt to the lithium salt is 1:(5-10); for example, 1:5, 1:8, 1:9, 1:10, etc.

[0052] In some embodiments of this application, the molar ratio of the zirconium salt to the alkaline substance is 1:(1.5-2); for example, 1:1.5, 1:1.8, 1:2, etc.

[0053] In some embodiments of this application, the molar ratio of the zirconium salt to the doped element salt is 1:(0.02-0.3); for example, 1:0.02, 1:0.05, 1:0.1, 1:0.15, 1:0.18, 1:0.2, 1:0.25, 1:0.3, etc.

[0054] In some embodiments of this application, the molar ratio of the zirconium salt to the hydroxycarboxylic acid is 1:(1-3); for example, 1:1, 1:2, 1:3, etc.

[0055] This application also provides a method for preparing the garnet-type solid electrolyte as described in the first aspect of this application, using the composition for preparing the garnet-type solid electrolyte as described in the second aspect of this application.

[0056] In some embodiments of this application, the following steps are included: (1) A white precipitate was obtained by mixing zirconium salt, lanthanum salt, alkaline substance and solvent; (2) The white precipitate, the doped element salt, the hydroxycarboxylic acid and the solvent are mixed to obtain a precipitate mixture solution; the precipitate mixture solution is centrifuged, washed, dried and calcined to obtain a solid powder; (3) The solid powder and lithium salt are mixed and ball-milled, and the ball-milled material is calcined to obtain the garnet-type solid electrolyte.

[0057] The method for preparing the garnet-type solid electrolyte described in this application involves a precipitation-precursor substitution-organic acid coordination-precipitation process. In this reaction system, alkaline substances are initially selected to obtain precursor zirconium salt and lanthanum salt hydroxides. Then, under the coordination of organic hydroxy acids, these hydroxides react synchronously with dopant ions to generate a mixed sol precipitate of organic acid zirconium lanthanum containing dopant ions. Subsequently, gas-state pulverization effectively removes particle agglomeration in the product and controls the particle size distribution. Ball milling is then used to achieve thorough mixing of small-diameter solid particles with lithium salts. Finally, high-temperature treatment yields a highly conductive, pure crystalline phase, small-diameter, uniformly doped lithium lanthanum zirconium oxide (LLZO) solid electrolyte material.

[0058] In some embodiments of this application, the solvents in steps (1) and (2) each independently include one or more of water, methanol and ethanol; the water used in the embodiments of this application is water obtained through water purification and ion removal treatment, wherein the heavy metal ions, copper, iron, cobalt and nickel ions are below 100 ppm.

[0059] In some embodiments of this application, in step (1), the mixing temperature is 25-40°C and the mixing time is 8-12h, such as 8h, 9h, 10h, 12h, etc.

[0060] In some embodiments of this application, in step (2), the mixing temperature is 60-80℃, such as 60℃, 65℃, 70℃, 78℃, 80℃, etc., and the mixing time is 4-10h, such as 4h, 5h, 6h, 8h, 10h, etc.

[0061] In some embodiments of this application, in step (2), the washing includes washing with an organic alcohol; preferably, the organic alcohol includes liquid linear alkyl alcohols, including one or more of ethanol, propanol, isopropanol and n-butanol. Alcohols can effectively reduce the amount of water and hydroxyl groups adsorbed on the particle surface, which helps to prepare particle-dispersed solid electrolytes.

[0062] In some embodiments of this application, in step (2), the drying temperature is 50-150°C, such as 50°C, 60°C, 80°C, 90°C, 105°C, 120°C, 150°C, etc., and the drying time is 6-12 hours. In some embodiments of this application, in step (2), the roasting temperature is 800-1000℃, such as 800℃, 850℃, 880℃, 930℃, 960℃, 1000℃, etc., and the roasting time is 4-10h, such as 4h, 6h, 8h, 10h, etc.

[0063] In some embodiments of this application, in step (3), the roasting temperature is 1000-1200℃ and the roasting time is 4-10h.

[0064] In some embodiments of this application, zirconium salt and lanthanum salt are dissolved in water to obtain a clear and transparent solution, denoted as A. An alkaline substance is dissolved in water, denoted as B. B is slowly added to A using a peristaltic pump in parallel flow (the addition rate of B can be 10-500 ml / min). The resulting solutions are uniformly mixed under mechanical stirring. Stirring is continued for 8-12 hours to obtain a white mixed solution. After washing and centrifugation with deionized water multiple times, a white precipitate is obtained. The obtained white precipitate is completely and uniformly dispersed by ultrasonication with water to obtain a white suspension, denoted as C. The dopant salt is dissolved in water and denoted as D. Under mechanical stirring, solution D is slowly added to solution C using a peristaltic pump (the addition rate of D can be 10-1000 ml / min), and the temperature of this reaction process is controlled at 60-80℃. After the addition is complete, an aqueous solution of hydroxycarboxylic acid is slowly added to the above solution using a peristaltic pump (the addition rate of the aqueous solution of hydroxycarboxylic acid can be 10-800 ml / min). Then, mechanical stirring is continued for 4-10 hours to obtain a precipitate mixture. The temperature of this reaction process is controlled at 60-80℃. The precipitate is obtained by centrifugation at a speed of 3000-10000 rpm, washed with organic alcohol, dried, calcined, and finally the obtained solid powder sample is subjected to gas-state grinding. The solid powder sample can be subjected to gas-state pulverization or ball milling, and the selected equipment is an air jet mill or a ball mill. When using an air jet mill for pulverization, the power of the air jet mill can be 5KW. The powder product is collected by a cyclone separator, and the power of the air compressor can be 100KW to provide 10.0Mpa compressed air for pulverization.

[0065] The above-mentioned solid powder and lithium salt are added to a ball mill jar for ball milling. Zirconia or alumina grinding balls are used as the grinding media during the ball milling process. The ball milling is carried out in an intermittent manner, with a 20-minute break after each half-hour grinding, and then the next cycle is carried out. The cumulative time is 4-10 hours. The material obtained after ball milling is calcined at 1100℃ for 4-10 hours (calcination is carried out in an air atmosphere, and air needs to be introduced during the calcination process) to obtain a highly conductive pure crystalline phase small-particle-size doped uniform lithium lanthanum zirconium oxide (LLZO) solid electrolyte material.

[0066] In the embodiments of this application, the containers for storing A, B, C, and D are glass containers, Teflon containers, organic plastic containers, or ceramic enamel containers; including but not limited to one or more of the following: glass flasks, glass beakers, wide-mouth bottles, test tubes, plastic beakers, plastic flasks, Teflon containers, enamel-lined reactors, and centrifuge tubes.

[0067] This application also provides an application of the garnet-type solid electrolyte described in the first aspect of this application or the garnet-type solid electrolyte obtained by the preparation method described in the third aspect of this application in lithium-ion batteries. The solid electrolyte described in this application has excellent thermal stability and high-temperature weather resistance, and will not burn under high-temperature conditions, which has unparalleled advantages in improving the safety of lithium-ion batteries.

[0068] The technical solution of this application will be further described below with reference to specific embodiments.

[0069] Example 1 A method for preparing a garnet-type solid electrolyte includes the following steps: (1) Dissolve 16g zirconium oxychloride and 18g lanthanum nitrate in 300ml of water under mechanical stirring. After stirring for 2h, a clear solution is obtained. Add 16ml of ammonia solution containing 25wt% to the solution through a peristaltic pump. After the addition is complete, continue stirring at 25℃ for 6h. Then, centrifuge at 9000rpm for 3 minutes to separate the white precipitate. Wash the white precipitate with water and centrifuge three times. Add the white precipitate to 200ml of water and disperse evenly. (2) Add 0.9g of aluminum nitrate to 20ml of water and stir to dissolve. Add the solution to the aqueous dispersion of the white precipitate product using a peristaltic pump and continue stirring at 65℃ for 1h. Weigh 8.5g of citric acid and add it to 200ml of water to dissolve. Add the solution to the reaction solution using a peristaltic pump and place it in an 80℃ water bath for 6h of mechanical stirring. After cooling, wash twice with ethanol by centrifugation, dry at 80℃ for 6h, calcine at 900℃ for 6h, and then process with a gas pulverizer at a gas pressure of 10.0MPa. Collect the solid powder sample using a cyclone separator. (3) Weigh 4.2g of lithium carbonate and the above solid powder together and put them into a ball mill jar. Add zirconium oxide ball milling beads and ball mill for 6 h. Then put the resulting mixed solid powder into a crucible and heat treat it at 1100℃ for 4 h to obtain a garnet-type solid electrolyte with (D50) of 275nm, high conductivity, pure crystalline phase, small particle size, and uniform doping.

[0070] Example 2 The only difference between the preparation method of the garnet-type solid electrolyte in Example 2 and that in Example 1 is that the doping element salt used in the preparation process of the garnet-type solid electrolyte in Example 2 is gallium nitrate.

[0071] Example 3 The only difference between the preparation method of the garnet-type solid electrolyte in Example 3 and that in Example 1 is that the doping element salt used in the preparation process of the garnet-type solid electrolyte in Example 3 is yttrium nitrate.

[0072] Example 4 The only difference between the preparation method of the garnet-type solid electrolyte in Example 4 and that in Example 1 is that the doping element salt used in the preparation process of the garnet-type solid electrolyte in Example 4 is cerium nitrate.

[0073] Example 5 The only difference between the preparation method of the garnet-type solid electrolyte in Example 5 and that in Example 1 is that the hydroxycarboxylic acid used in the preparation process of the garnet-type solid electrolyte in Example 5 is lactic acid.

[0074] Example 6 The only difference between the preparation method of the garnet-type solid electrolyte in Example 6 and that in Example 1 is that the hydroxycarboxylic acid used in the preparation process of the garnet-type solid electrolyte in Example 6 is malic acid.

[0075] Example 7 The only difference between the preparation method of the garnet-type solid electrolyte in Example 7 and that in Example 1 is that the hydroxycarboxylic acid used in the preparation process of the garnet-type solid electrolyte in Example 7 is tartaric acid.

[0076] Example 8 The only difference between the preparation method of the garnet-type solid electrolyte in Example 8 and Example 1 is that the amount of dopant salt added during the preparation of the garnet-type solid electrolyte in Example 8 is different from that in Example 1.

[0077] The specific operating steps include: adding 0.3g of aluminum nitrate to 20ml of water and stirring thoroughly to dissolve it, then adding it to the aqueous dispersion of the white precipitate product using a peristaltic pump. Other operating procedures are the same as in Example 1.

[0078] Example 9 The only difference between the preparation method of the garnet-type solid electrolyte in Example 9 and Example 1 is that the amount of dopant salt added during the preparation of the garnet-type solid electrolyte in Example 9 is different from that in Example 1.

[0079] The specific operating steps include: adding 6g of aluminum nitrate to 20ml of water and stirring to dissolve it, then adding it to the aqueous dispersion of the white precipitate product using a peristaltic pump. Other operating procedures are the same as in Example 1.

[0080] Example 10 The only difference between the preparation method of the garnet-type solid electrolyte in Example 10 and Example 2 is that the amount of dopant salt added during the preparation of the garnet-type solid electrolyte in Example 10 is different from that in Example 2.

[0081] The specific operating steps include: adding 5.6g of nitric acid to 20ml of water and stirring thoroughly to dissolve it, then adding it to the aqueous dispersion of the white precipitate product using a peristaltic pump. Other operating procedures are the same as in Example 2.

[0082] Example 11 The only difference between the preparation method of the garnet-type solid electrolyte in Example 11 and Example 1 is that the amount of hydroxycarboxylic acid added during the preparation of the garnet-type solid electrolyte in Example 11 is different from that in Example 1.

[0083] The specific operating steps include: weighing 12.5 citric acid and dissolving it fully in 200 ml of water, then adding it to the above reaction solution using a peristaltic pump. Other operating procedures are the same as in Example 1.

[0084] Comparative Example 1 The preparation method of the garnet-type solid electrolyte described in Comparative Example 1 includes the following steps: 16g zirconium oxychloride, 18g lanthanum nitrate, 0.9g aluminum nitrate, and 1.0g PEG 10000 were dissolved in 500ml of water and stirred for 30min. Then, 400ml of an aqueous solution containing 10g ammonium oxalate was added to the solution via a peristaltic pump. After stirring at 25℃ for 12h, the resulting gel solution was centrifuged at 11000rpm for 5min to obtain a white gel. The gel was then washed twice with water and twice with ethanol, dried in air at 60℃ for 12h, calcined at 1000℃ for 4h, and then processed using a gas pulverizer at 1.0MPa. The resulting solid powder sample was collected by a cyclone separator. This solid powder was mixed with 4.2g of lithium carbonate solid powder, and the mixture was placed in a ball mill jar with milling beads added. The mixture was ball milled for 6h, and then the resulting solid powder was placed in a crucible and heat-treated at 1100℃ for 4h. A solid material with a (D50) of 175 nm can be obtained. XRD analysis shows that it does not match the cubic phase and LLZO.

[0085] This application presents performance studies on the garnet-type solid electrolytes described in Examples 1-13 and Comparative Example 1.

[0086] Research Methods: The garnet-type solid electrolytes described in Examples 1-13 and Comparative Example 1 of this application were placed into molds and pressed into shape using a press. The pressure was set at 200 MPa for each sample, resulting in green circular samples with a thickness of 1 mm and a diameter of 2 cm. The samples were then sintered at 1250 °C under normal pressure to obtain sintered LLZO solid electrolyte discs.

[0087] The DC resistivity of each sample was measured using the double probe method at 25℃. Before the test, the top and bottom of the sample were coated with silver to reduce measurement error. The DC conductivity of each sample was measured using a high resistance meter. The results are shown in Table 1.

[0088] Table 1

[0089] As can be seen from Table 1, the conductivity of the obtained solid electrolyte can be effectively improved by selecting appropriate doping elements and doping amounts.

[0090] Comparing Examples 1-4, it can be seen that when the doping element salt used in the preparation process of garnet-type solid electrolyte is aluminum nitrate or gallium nitrate, the resulting garnet-type solid electrolyte has better conductivity.

[0091] Comparing Examples 1 and 5-7, it can be seen that when citric acid and tartaric acid are used as hydroxycarboxylic acids in the preparation process of garnet-type solid electrolytes, the resulting garnet-type solid electrolytes have better conductivity.

[0092] Comparing Examples 1 and 8-9, it can be seen that when the molar ratio of zirconium salt to the doped element salt is 1:(0.02-0.05) during the preparation of garnet-type solid electrolyte, the obtained garnet-type solid electrolyte has better conductivity.

[0093] SEM image of the garnet-type solid electrolyte described in Example 1 of this application, as shown below. Figure 1 As shown.

[0094] from Figure 1 As can be seen, the obtained solid electrolyte has high dispersibility, with particle size in the range of 100-300 nm, which is relatively small.

[0095] The X-ray spectrum of the garnet-type solid electrolyte described in Example 1 of this application is as follows: Figure 2 As shown.

[0096] from Figure 2 As can be seen, the obtained solid electrolyte has a relatively pure garnet-type crystal phase structure.

[0097] Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made to the above embodiments by those skilled in the art are within the protection scope of the present invention.

Claims

1. A garnet-type solid electrolyte, characterized in that, The garnet-type solid electrolyte has a D50 < 300 nm and a specific surface area of ​​2-30 m². 2 / g.

2. A composition for preparing the garnet-type solid electrolyte of claim 1, characterized in that, This includes zirconium salts, lanthanum salts, lithium salts, alkaline substances, doped element salts, and hydroxycarboxylic acids.

3. The composition for preparing garnet-type solid electrolytes according to claim 2, characterized in that, The zirconium salt includes one or more of zirconium oxynitrate, zirconium oxychloride, zirconium nitrate, and zirconium oxysulfate; And / or, the lanthanum salt includes lanthanum nitrate and / or lanthanum chloride; And / or, the lithium salt includes lithium carbonate; And / or, the alkaline substance includes ammonia and / or sodium hydroxide; And / or, the doping element salt includes one or more of rare earth salts, aluminum salts, and gallium salts that are compatible with the lithium lanthanum zirconium oxide crystalline phase structure; preferably, the doping element salt includes one or more of yttrium nitrate, cerium nitrate, gadolinium nitrate, neodymium nitrate, aluminum nitrate, and gallium nitrate; more preferably, the doping element salt includes aluminum nitrate and / or gallium nitrate. And / or, the hydroxycarboxylic acid includes hydroxycarboxylic acids having 2-5 carbon atoms, preferably, the hydroxycarboxylic acid includes one or more of oxalic acid, citric acid, lactic acid, malic acid and tartaric acid, more preferably, the hydroxycarboxylic acid includes citric acid and / or tartaric acid.

4. The composition for preparing garnet-type solid electrolytes according to claim 2, characterized in that, The molar ratio of the zirconium salt to the lanthanum salt is 2:(3-5); And / or, the molar ratio of the zirconium salt to the lithium salt is 1:(5-10); And / or, the molar ratio of the zirconium salt to the alkaline substance is 1:(1.5-2). And / or, the molar ratio of the zirconium salt to the doped element salt is 1:(0.02-0.3). And / or, the molar ratio of the zirconium salt to the hydroxycarboxylic acid is 1:(1-3).

5. The method for preparing the garnet-type solid electrolyte according to claim 1, characterized in that, The composition for preparing garnet-type solid electrolytes according to any one of claims 2-4 is used.

6. The method for preparing the garnet-type solid electrolyte according to claim 5, characterized in that, Includes the following steps: (1) A white precipitate was obtained by mixing zirconium salt, lanthanum salt, alkaline substance and solvent; (2) The white precipitate, the doped element salt, the hydroxycarboxylic acid and the solvent are mixed to obtain a precipitate mixture solution; the precipitate mixture solution is centrifuged, washed, dried and calcined to obtain a solid powder; (3) The solid powder and lithium salt are mixed and ball-milled, and the ball-milled material is calcined to obtain the garnet-type solid electrolyte.

7. The method for preparing the garnet-type solid electrolyte according to claim 6, characterized in that, The solvents in steps (1) and (2) each independently include one or more of water, methanol, and ethanol; And / or, in step (1), the mixing temperature is 25-40°C and the mixing time is 8-12h.

8. The method for preparing the garnet-type solid electrolyte according to claim 6, characterized in that, In step (2), the mixing temperature is 60-80℃ and the mixing time is 4-10h; And / or, in step (2), the washing includes washing with an organic alcohol; preferably, the organic alcohol includes one or more of ethanol, propanol, isopropanol and n-butanol; And / or, in step (2), the drying temperature is 50-150°C and the drying time is 6-12h; And / or, in step (2), the roasting temperature is 800-1000℃ and the roasting time is 6-10h.

9. The method for preparing the garnet-type solid electrolyte according to claim 6, characterized in that, In step (3), the roasting temperature is 1000-1200℃ and the roasting time is 4-10h.

10. The application of the garnet-type solid electrolyte of claim 1 or the garnet-type solid electrolyte obtained by any one of claims 5-9 in lithium-ion batteries.

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