Lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and surfaces, its manufacturing method and applications

Abstract

The present invention relates to a lithium-lanthanum zirconium composite oxide solid electrolyte doped on the grain boundary and surface, and its preparation method and application. By using a stepwise doping method, some doping elements are located on the grain boundary and surface of the lithium-lanthanum zirconium composite oxide solid electrolyte, improving the distribution state of the doping elements on the grain boundary, reducing the number of grain boundaries, reducing the grain boundary resistance of the lithium-lanthanum zirconium composite oxide, and making it obtain high ionic conductivity. The doping method used has the advantages of simple process, low cost and high versatility, can meet the demand for doping elements of different solid electrolytes, and is suitable for large-scale application. The solid electrolyte obtained by adopting the technical solution of the present invention can be used in the fields of all-solid-state lithium metal or lithium ion batteries, semi-solid lithium ion batteries, lithium air batteries, etc.

Description

[Technical Field] 【0001】 <Cross-reference of related applications> This application is filed based on a Chinese patent application with application number 202210149801.9, filed on 14 February 2022, and claims priority from said Chinese patent application, the entire said Chinese patent application is incorporated into this application by reference. 【0002】 The present invention relates to the technical field of lithium-ion batteries, and more particularly to a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface, a method for manufacturing it, and its applications. This solid electrolyte can be used in fields such as all-solid-state lithium metal or lithium-ion batteries, semi-solid-state lithium-ion batteries, and lithium-air batteries. [Background technology] 【0003】 Lithium-ion batteries are currently the most promising energy storage device due to their advantages such as high operating voltage, high energy density, relatively long cycle stability life, and low self-discharge rate. However, the energy density of commercial lithium-ion batteries (liquid electrolyte) was already 260 Wh / kg in 2019. -1 As the system reaches its limits, and soon to be fully utilized, the problems of liquid electrolytes always being organic solvents, the risk of leakage, and the increased likelihood of security incidents such as fires in certain extreme environments are becoming increasingly apparent. Therefore, using a solid electrolyte with superior safety features instead of a liquid electrolyte is an effective solution to the above problems. An ideal solid electrolyte should meet the requirements of high ionic conductivity, stable interfacial compatibility, and good mechanical properties. 【0004】 Lithium lanthanum zirconium oxygen, after its first successful production in 2007, has become a typical representative of solid electrolytes, although its ionic conductivity remains two orders of magnitude lower than that of liquid electrolytes. Research has revealed that elemental doping is an effective way to increase the ionic conductivity of lithium lanthanum zirconium oxygen. Currently, solid-phase reaction methods, sol-gel methods, and chemical precipitation methods are all used to produce lithium lanthanum zirconium oxygen materials. In particular, the solid-phase method is preferred due to its advantages such as a simple manufacturing process and the ability to mass-produce. As is well known, lithium lanthanum zirconium oxygen has a polycrystalline structure, and therefore, the influence of grain boundaries on its ionic conductivity cannot be ignored. Existing research has shown that grain boundary resistance has a negative effect on the ionic conductivity of lithium lanthanum zirconium oxygen (Seungho Yu, Donald J. Siegel. Chem. Mater. 2017, 29, 9639-9647). Therefore, reducing grain boundary resistance is crucial for increasing the ionic conductivity of lithium lanthanum zirconium composite oxides. David et al. hot-pressed lithium lanthanum zirconium composite oxides at 1100°C, thereby obtaining higher density lithium lanthanum zirconium composite oxide samples (99% of theoretical density) and larger grain sizes, thereby reducing the contribution of grain boundary resistance to the total resistance (David, IN; Thompson, T.; Wolfenstine, J.; Allen, JL; Sakamoto, JJAm.Ceram.Soc.2015, 98, 1209-1214). However, high-temperature hot-pressing requires specialized equipment and is inefficient, making it unsuitable for large-scale production. [Overview of the Initiative] [Problems that the invention aims to solve] 【0005】 Based on the above-mentioned conditions of the prior art, the present invention aims to provide a lithium lanthanum zirconium composite oxide solid electrolyte, a manufacturing method, and applications that dope the grain boundaries and surface of the lithium lanthanum zirconium composite oxide solid electrolyte by grain boundary doping, thereby enabling the doping element to be positioned at the grain boundaries and surface of the lithium lanthanum zirconium composite oxide solid electrolyte, reducing the grain boundary resistance of the lithium lanthanum zirconium composite oxide, and combining the advantages of high ionic conductivity and low cost. [Means for solving the problem] 【0006】 To achieve the above objective, a first aspect of the present invention provides a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface, wherein the chemical formula of the lithium lanthanum zirconium composite oxide solid electrolyte is Li 7-x La 3-y Zr 2-z M α O 12-β D δ Here, M contains one or more cation-doping elements, D contains one or more anion-doping elements, and 0≦x≦3, 0≦y≦1.5, 0≦z≦1, 0<α<3, 0≦β≦1.5, 0≦δ≦1. 【0007】 Furthermore, the grain boundaries and surface of the solid electrolyte contain one or more of the following: oxides of Li and M, or fluorides, sulfides, nitrogen-containing compounds, phosphates, and composites thereof formed from oxides of Li and M and Li, M, and D. 【0008】 Furthermore, the doping element M includes one or more combinations of rare earth elements other than the cations Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, B, Al, Ga, In, Si, Ge, Sn, Sb, Bi, Se, Te, Nb, Mo, Hf, Ta, W, and La. Preferably, the doping element M includes one or more combinations of the cations Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, In, Ge, Sn, Sb, Te, Nb, Mo, Ta, Ce, Pr, Nd, Sm, Eu, Gd, Yb, Sc, and Y. More preferably, the doping element M includes one or more combinations of the cations Mn, Fe, Co, Ni, Al, Ga, Nb, Ta, Ce, Pr, Nd, Sm, Gd, Yb, and Y. Doping element D contains one or more of the anions N, F, P, and S. 【0009】 Furthermore, in terms of moles, the molar content of doping element M is 12% or less of the molar amount of the solid electrolyte. The molar content of doping element D is 5% or less of the molar amount of the solid electrolyte. 【0010】 Furthermore, Li and M, or Li, M and D, exist at the grain boundaries and on the surface of the solid electrolyte in the form of one or more of oxides, fluorides, sulfides, nitrogen-containing compounds, phosphates, and composites thereof. 【0011】 Furthermore, the lithium lanthanum zirconium composite oxide includes a garnet-type structure. 【0012】 A second aspect of the present invention provides a method for producing a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface as described in the first aspect of the present invention, Step S1 involves mixing aqueous solutions of lanthanum and zirconium compounds in stoichiometric ratios required for the product to obtain a mixed solution, adding the mixed solution and a basic substance to a reactor to carry out a precipitation reaction, and then subjecting the resulting precipitate to suction filtration, washing, drying, and roasting to obtain lanthanum zirconium oxide. Step S2 includes mixing the lanthanum zirconium oxide with a liquid salt of doping elements M and Li in one or more steps under stirring conditions, performing one or two heat treatments after drying, and further performing one or two calcinations to obtain a lithium lanthanum zirconium composite oxide solid electrolyte doped at the grain boundaries and surface. 【0013】 A third aspect of the present invention provides a method for producing a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface as described in the first aspect of the present invention, Step S1 involves mixing lanthanum, zirconium, and an aqueous solution of M or a compound of M in stoichiometric ratios required for the product to obtain a mixed solution, adding the mixed solution and a basic substance to a reactor to carry out a precipitation reaction, and then subjecting the resulting precipitate to suction filtration, washing, drying, and roasting to obtain lanthanum zirconium oxide containing M. Step S2 includes mixing a lanthanum zirconium oxide containing the aforementioned M with a liquid salt of Li or a mixed liquid salt of the remaining doping element M and Li in one or more steps under stirring conditions, drying, followed by one or two heat treatments, and then one or two calcinations to obtain a lithium lanthanum zirconium composite oxide solid electrolyte doped at the grain boundaries and surface. 【0014】 Furthermore, all or part of Li is added to the lanthanum zirconium oxide containing M in the form of a solid salt. 【0015】 Furthermore, the zirconium source in the mixed solution described in step S1 includes one or more of the following: zirconium oxychloride, zirconium oxynitrate, zirconium sulfate, zirconium acetate, and zirconium citrate; and the lanthanum source includes one or more of the following: lanthanum chloride, lanthanum nitrate, lanthanum sulfate, lanthanum acetate, and lanthanum citrate. 【0016】 Furthermore, the basic substance comprises magnesium bicarbonate, urea, and at least one hydroxide, carbonate, or bicarbonate of at least one element from among ammonium, sodium, and potassium, and preferably at least one from among sodium hydroxide, urea, aqueous ammonia, and ammonium bicarbonate. 【0017】 Furthermore, in step S1, the mixed liquid and the basic substance are added to the reactor and a precipitation reaction is carried out, the pH value during the precipitation process is controlled to be within the range of 4.5 to 14, preferably 5 to 10, the pH value at the precipitation endpoint is controlled to be 8 to 13, preferably 9 to 11, and the temperature is controlled to be 0 to 120°C, preferably 10 to 80°C. 【0018】 Furthermore, the liquid salts of the doping elements M and Li include one or more of the following: nitrates, acetates, sulfates, citrates, and amino acid salt molten salts or aqueous solutions. The molar ratio of Li and M at the grain boundaries and on the surface is 10% to 70%. The morphology and proportion of Li and M at the grain boundaries and on the surface are adjusted and controlled by controlling precipitation parameters, heat treatment and calcination temperatures and times of the product, and the atmosphere. 【0019】 Furthermore, doping element D is added in one or more steps in steps S1 and S2, and doping element D is derived from one or more combinations of nitrates, fluorides, phosphates, sulfates, or sulfides. The molar ratio of D at the grain boundaries and on the surface is 10% to 70%. The morphology and proportion of Li and M at the grain boundaries and on the surface are adjusted and controlled by controlling precipitation parameters, heat treatment and calcination temperatures and times of the product, and atmosphere. 【0020】 Furthermore, the roasting temperature in step S1 is 600 to 1000°C, preferably 700 to 900°C, and the roasting time is 1 to 24 hours, preferably 3 to 15 hours. 【0021】 Furthermore, the heat treatment temperature in step S2 is 200 to 750°C, preferably 400 to 600°C, the heat treatment time is 1 to 24 hours, preferably 3 to 15 hours, the drying temperature is 50 to 200°C, and the drying time is 1 to 24 hours. 【0022】 Furthermore, the firing temperature in step S2 is 700 to 1100°C, preferably 800 to 950°C, and the firing time is 1 to 24 hours, preferably 3 to 15 hours. 【0023】 A fourth aspect of the present invention provides applications for the lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and surfaces according to the first aspect of the present invention in all-solid-state lithium metal or lithium-ion batteries, semi-solid-state lithium-ion batteries, and lithium-air batteries. [Effects of the Invention] 【0024】 As described above, the present invention provides a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface, a method for producing the same, and its applications. By a stepwise doping method, some of the doping elements are positioned at the grain boundaries and on the surface of the lithium lanthanum zirconium composite oxide solid electrolyte, improving the distribution of doping elements at the grain boundaries, reducing the number of grain boundaries, lowering the grain boundary resistance of the lithium lanthanum zirconium composite oxide, and improving the ionic conductivity of the lithium lanthanum zirconium composite oxide solid electrolyte. Compared to elemental doping by the ball mill method, doping at grain boundaries and on the surface does not destroy the structure, morphology, crystal grains, and particles of the lithium lanthanum zirconium composite oxide, does not generate phase separation or surface defects, and the distribution of doped elements is more uniform. Doping elements in the ball mill method are less likely to penetrate into particle grain boundaries. The grain boundary and surface doping method provided by the technical solution of the present invention is versatile, achieving a highly efficient and low-cost reduction of the grain boundary resistance of lithium lanthanum zirconium composite oxide, thereby improving ionic conductivity and meeting the demand for doping elements for different solid electrolytes. [Brief explanation of the drawing] 【0025】 [Figure 1] This is a flowchart of a method for manufacturing a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and surfaces according to the present invention. 【Embodiments for Carrying Out the Invention】 【0026】 In order to more clearly define the object, technical solution and advantages of the present invention, the present invention will be further described in detail below in connection with specific embodiments with reference to the drawings. It should be understood that these descriptions are illustrative and do not limit the scope of the present invention. Also, in the following description, descriptions of well-known structures and technologies are omitted in order to avoid unnecessary confusion of the concept of the present invention. 【0027】 The first aspect of the present invention provides a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and surfaces, and the chemical formula of the lithium lanthanum zirconium composite oxide solid electrolyte is Li 7-x La 3-y Zr 2-z M α O 12-β D δ where M contains one or more cation doping elements, D contains one or more anion doping elements, and 0≦x≦3, 0≦y≦1.5, 0≦z≦1, 0<α<3, 0≦β≦1.5, 0≦δ≦1. Here, at the grain boundaries and surfaces of the solid electrolyte, it contains one or more of oxides of Li and M, or fluorides, sulfides, nitrogen-containing compounds, phosphates and their composites formed by oxides of Li and M and Li, M and D, effectively reducing the grain boundary resistance of the lithium lanthanum zirconium composite oxide, thereby effectively improving its ionic conductivity. 【0028】 The doping element M may include one or more combinations of rare earth elements other than the cations Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, B, Al, Ga, In, Si, Ge, Sn, Sb, Bi, Se, Te, Nb, Mo, Hf, Ta, W, and La. Preferably, the doping element M includes one or more combinations of Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, In, Ge, Sn, Sb, Te, Nb, Mo, Ta, Ce, Pr, Nd, Sm, Eu, Gd, Yb, Sc, and Y. More preferably, the doping element M includes one or more combinations of Mn, Fe, Co, Ni, Al, Ga, Nb, Ta, Ce, Pr, Nd, Sm, Gd, Yb, and Y. The doping element D may contain one or more of the anions N, F, P, and S. 【0029】 In terms of moles, the molar content of doping element M is 12% or less of the molar amount of the solid electrolyte, and the molar content of doping element D is 5% or less of the molar amount of the solid electrolyte. 【0030】 Furthermore, Li and M, or Li, M and D, exist at the grain boundaries and on the surface of the solid electrolyte in the form of one or more of oxides, fluorides, sulfides, nitrogen-containing compounds, phosphates, and composites thereof. 【0031】 Furthermore, the lithium lanthanum zirconium composite oxide includes a garnet-type structure. 【0032】 A second aspect of the present invention provides a method for producing a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface as described in the first aspect of the present invention, the flowchart of which is shown in Figure 1, and the method includes a coprecipitation method and a grain boundary doping method. Step S1 involves mixing aqueous solutions of lanthanum and zirconium compounds in stoichiometric ratios required for the product to obtain a mixed solution, adding the mixed solution and a basic substance to a reactor to carry out a precipitation reaction, and performing suction filtration, washing, drying, and roasting of the obtained precipitate to obtain lanthanum zirconium oxide, wherein step S1 includes removing impurity ions in the precipitate by washing, Step S2 includes mixing the lanthanum zirconium oxide with a liquid salt of doping elements M and Li in one or more steps under stirring conditions, performing one or two heat treatments after drying, and further performing one or two calcinations to obtain a lithium lanthanum zirconium composite oxide solid electrolyte doped at the grain boundaries and surface. 【0033】 A third aspect of the present invention provides a method for producing a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface as described in the first aspect of the present invention, Step S1 involves mixing lanthanum, zirconium, and an aqueous solution of M or a compound of M in stoichiometric ratios required for the product to obtain a mixed solution, adding the mixed solution and a basic substance to a reactor to carry out a precipitation reaction, and then subjecting the resulting precipitate to suction filtration, washing, drying, and roasting to obtain lanthanum zirconium oxide containing M. Step S2 can be adopted, in which a lanthanum zirconium oxide containing the aforementioned M is mixed with a liquid salt of Li or a mixed liquid salt of the remaining doping element M and Li in one or more steps under stirring conditions, then subjected to one or two heat treatments after drying, and further subjected to one or two calcinations to obtain a lithium lanthanum zirconium composite oxide solid electrolyte doped at the grain boundaries and surface. 【0034】 In the manufacturing methods provided in the second and third embodiments described above, all or part of Li may be added to the lanthanum zirconium oxide containing M in the form of a solid salt. 【0035】 In the above manufacturing method, step S1 mainly relates to a coprecipitation method, and step S2 mainly relates to a grain boundary doping method. By coprecipitation and grain boundary doping, a lithium lanthanum zirconium composite oxide solid electrolyte is produced, the doping elements are positioned at the grain boundaries and surface of the lithium lanthanum zirconium composite oxide solid electrolyte, improving the distribution of doping elements at the grain boundaries, reducing the number of grain boundaries, lowering the grain boundary resistance of the lithium lanthanum zirconium composite oxide, and improving the ionic conductivity of the lithium lanthanum zirconium composite oxide solid electrolyte. This method is versatile and can meet the demand for doping elements for different solid electrolytes. 【0036】 Here, the zirconium source in the mixed solution described in step S1 includes one or more of the following: zirconium oxychloride, zirconium oxynitrate, zirconium sulfate, zirconium acetate, and zirconium citrate; the lanthanum source includes one or more of the following: lanthanum chloride, lanthanum nitrate, lanthanum sulfate, lanthanum acetate, and lanthanum citrate; and the basic substance includes at least one of the following: magnesium bicarbonate, urea, and hydroxide, carbonate, or bicarbonate of at least one element from among ammonium, sodium, and potassium, preferably at least one of sodium hydroxide, urea, aqueous ammonia, and ammonium bicarbonate. 【0037】 In step S1, the mixed liquid and the basic substance are added to the reactor and a precipitation reaction is carried out. The pH value during the precipitation process is controlled to be within the range of 4.5 to 14, preferably 5 to 10. The pH value at the precipitation endpoint is controlled to be 8 to 13, preferably 9 to 11. The temperature is controlled to be 0 to 120°C, preferably 10 to 80°C. 【0038】 The liquid salts of doping elements M and Li include one or more of the following: nitrates, acetates, sulfates, citrates, and amino acid salt molten salts or aqueous solutions. 【0039】 Doping element D may be added in one or more steps in steps S1 and S2, and doping element D includes one or more combinations of nitrates, fluorides, phosphates, sulfates, or sulfides. 【0040】 In step S1, the roasting temperature is 600 to 1000°C, preferably 700 to 900°C, and the roasting time is 1 to 24 hours, preferably 3 to 15 hours. 【0041】 The heat treatment temperature in step S2 may be 200 to 750°C, preferably 400 to 600°C, the heat treatment time is 1 to 24 hours, preferably 3 to 15 hours, the drying temperature is 50 to 200°C, the drying time is 1 to 24 hours, and the calcination temperature is 700 to 1100°C, preferably 800 to 950°C. The calcination time is 1 to 24 hours, preferably 3 to 15 hours. The morphology and proportion of Li and M at the grain boundaries and on the surface are adjusted and controlled by controlling the precipitation parameters, the heat treatment and calcination temperatures, times, and atmosphere of the product. In order to meet the specific requirements for electrolyte performance in different applications, it is necessary to adjust or change the type of doping element and the microstructure of the electrolyte, thereby requiring the adoption of different heat treatment methods. For example, the heat treatment may be performed in stages to allow more doping elements to be stably and uniformly incorporated into the grain boundaries and on the surface, and treatments such as water washing and water quenching may be performed between the two heat treatment stages. The lithium lanthanum zirconium composite oxide obtained as described above may undergo two firings to effectively control its particle size and dispersibility. After the first firing, ball milling and surface treatment can be used to avoid a second sintering and agglomeration. 【0042】 A fourth aspect of the present invention provides applications for the lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and surfaces as described in the first aspect of the present invention in all-solid-state lithium metal or lithium-ion batteries, semi-solid-state lithium-ion batteries, and lithium-air batteries. By employing the lithium lanthanum zirconium composite oxide solid electrolyte of the embodiment of the present invention and applying it to fields such as solid lithium metal or lithium-ion batteries, semi-solid-state lithium-ion batteries, and lithium-air batteries, higher energy density and better safety performance can be achieved. 【0043】 The lithium lanthanum zirconium composite oxide solid electrolyte powder doped at the grain boundaries and surface can be manufactured into ceramics by methods such as curtain coating or hot coating. Furthermore, by mixing it with a polymer or through structural design, a layered composite solid electrolyte with a higher degree of matching with the electrode material can be manufactured. 【0044】 The present invention will be further described below with reference to specific examples. 【0045】 (Comparative Example 1) La(NO3)3, ZrO(NO3)2, and Mn(NO3)2 in stoichiometric ratios were mixed with water to form a 1.5 M total cation solution. Under stirring conditions, the mixture and a 3.0 M aqueous ammonia solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to 7 ± 0.2, and the final pH value was 11. The temperature was controlled to 50°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium manganese oxide. Li2CO3 was uniformly mixed with the lanthanum zirconium manganese oxide using a ball mill and calcined at 900°C for 9 hours to obtain a lithium lanthanum zirconium composite oxide solid electrolyte (Li7La3Zr) with Mn doped into the body phase. 1.8 Mn 0.2 O 12 We obtained a sample and measured its ionic conductivity, which was 1.89 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0046】 (Comparative Example 2) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed with water to form a 1.5 M total cation solution. Under stirring conditions, the mixture and a 3.0 M aqueous ammonia solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to 7 ± 0.2, and the final pH value was 11. The temperature was controlled to 50°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. MnO2 and Li2CO3 were uniformly mixed with the lanthanum zirconium oxide using a ball mill and calcined at 900°C for 9 hours to obtain a lithium lanthanum zirconium composite oxide solid electrolyte (Li7La3Zr) with Mn doped into the body phase. 1.8 Mn 0.2 O 12 We obtained a sample and measured its ionic conductivity, which was 1.56 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0047】 (Example 1) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed with water to form a 1.5 M total cation solution. Under stirring conditions, the mixture and a 3.0 M aqueous ammonia solution were added at a constant rate to the reactor. The pH value during the precipitation process was controlled to 7 ± 0.2, and the final pH value was 11. The temperature was controlled to 50°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with a liquid salt of Mn(NO3)2 and LiNO3 doped in stoichiometric ratios of Mn and Li, dried at 100°C for 12 hours, heat-treated at 450°C for 10 hours, and further calcined at 900°C for 9 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li7La3Zr, with Mn and Li oxide doped at the grain boundaries and surface. 1.8 Mn 0.2 O 12 We obtained a sample and measured its ionic conductivity, which was 6.03 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0048】 (Example 2) A stoichiometric ratio of La2(SO4)3 and Zr(SO4)2 was mixed into a 0.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3.0 M aqueous ammonia solution were added at a constant rate to the reactor. The pH value during the precipitation process was controlled to 9 ± 0.2, and the final pH value was 10. The temperature was controlled to 50°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 850°C for 8.5 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Al(NO3)3 and LiNO3 liquid salts doped in stoichiometric ratios of Al and Li, dried at 100°C for 12 hours, heat-treated at 450°C for 12 hours, and further calcined at 850°C for 10 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, doped with Li, Al oxide and sulfide at the grain boundaries and surface. 6.25 La3Zr2Al 0.25 O 11.4 S 0.6 We obtained a sample and measured its ionic conductivity, which was 7.01 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0049】 (Example 3) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3.0 M aqueous ammonia solution were added at a constant rate to the reactor. The precipitation reaction was carried out at a controlled temperature of 50°C, with a pH of 5-9 during the precipitation process and an endpoint pH of 11. The resulting precipitate was filtered, washed, and dried. The dried product was roasted at 600°C for 48 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Fe(NO3)3 and LiNO3 liquid salts doped in stoichiometric ratios of Fe and Li, dried at 100°C for 12 hours, heat-treated at 200°C for 12 hours, and further calcined at 860°C for 9.5 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, doped with Li and Fe oxides at the grain boundaries and on the surface. 6.7 La3Zr2Fe 0.1 O 12 We obtained a sample and measured its ionic conductivity, which was found to be 4.25 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0050】 (Example 4) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.0 M total cation concentration mixture. Under stirring conditions, the mixture and a 3.0 M aqueous ammonia solution were added at a constant rate to the reactor. The pH value during the precipitation process was controlled to 8 ± 0.2, and the final pH value was 9.5. The temperature was controlled to 50°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with a liquid salt of Co(NO3)2 and LiNO3 doped in stoichiometric ratios of Co and Li, dried at 80°C for 18 hours, heat-treated at 550°C for 8 hours, further calcined at 800°C for 8 hours, and finally calcined at 950°C for 7 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li7La3Zr, with Li and Co oxides doped at the grain boundaries and on the surface. 1.5 Co 0.5 O 12 We obtained a sample and measured its ionic conductivity, which was 6.86 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0051】 (Example 5) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios are mixed into a 1.0 M total cation concentration mixture. Under stirring conditions, the mixture and a 4.0 M aqueous ammonia solution are added at a constant rate to the reactor. The precipitation reaction is carried out under controlled conditions, with a pH of 9-12 during the precipitation process and a pH of 9 at the precipitation endpoint, at a controlled temperature of 50°C. The resulting precipitate is filtered, washed, and dried. The dried product is roasted at 900°C for 8 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide is mixed with Ni and Li-doped Ni(CH3COO)2,CH3COOLi liquid salt, dried at 100°C for 12 hours, heat-treated at 680°C for 6.5 hours, and further calcined at 900°C for 9 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li7La3Zr, with Li and Ni oxide doped at the grain boundaries and surface. 1.8 Ni 0.4 O 12 We obtained a sample and measured its ionic conductivity, which was 5.36 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0052】 (Example 6) La(CH3COO)3 and Zr(CH3COO)4 in stoichiometric ratios were mixed into a 0.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3.5 M aqueous ammonia solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to 8 ± 0.2, and the final pH value was 11. The temperature was controlled to 50°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Ga(NO3)3 and LiNO3 liquid salts doped in stoichiometric ratios of Ga and Li, dried at 100°C for 12 hours, heat-treated at 600°C for 6 hours, and further calcined at 920°C for 8.5 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, doped with Li and Ga oxides at the grain boundaries and surface. 6.4 La3Zr2Ga 0.2 O 12 We obtained a sample and measured its ionic conductivity, which was 1.14 × 10⁻⁶. -3 The temperature was S / cm (at 25°C). 【0053】 (Example 7) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios are mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M sodium hydroxide solution are added to the reactor at a constant rate. The precipitation reaction is carried out at a controlled temperature of 60°C, with a pH of 10-14 during the precipitation process and a final pH of 10. The resulting precipitate is filtered, washed, and dried. The dried product is roasted at 750°C for 10 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide is then mixed stepwise with NbO(NO3)3, LiNO3, and NH4F liquid salts doped in stoichiometric ratios of Nb and Li. After drying at 100°C for 12 hours, the mixture is heat-treated at 600°C for 6 hours, and then calcined at 940°C for 8 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li, Nb oxide and fluoride at the grain boundaries and on the surface. 6.3 La3Zr 1.4 Nb 0.7 O 11.75 F 0.5 We obtained a sample and measured its ionic conductivity, which was 9.65 × 10⁻⁶. -4The temperature was S / cm (at 25°C). 【0054】 (Example 8) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M sodium hydroxide solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to 8 ± 0.2, and the final pH value was 9.5. The temperature was controlled to 50°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 1000°C for 1 hour to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was then mixed stepwise with a liquid salt of Ce(NO3)3, LiNO3, (NH4)3PO4 doped in stoichiometric ratios of Ce and Li. After drying at 100°C for 5 hours, the mixture was heat-treated at 750°C for 1 hour, and then calcined at 900°C for 9 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li, Ce oxide and phosphate at the grain boundaries and on the surface. 6.8 La 2.8 Zr2Ce 0.2 O 10.5 P was obtained, and its ionic conductivity was measured, yielding 5.08 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0055】 (Example 9) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3.05 M sodium hydroxide solution were added at a constant rate to the reactor. The pH value during the precipitation process was controlled to 8 ± 0.2, and the final pH value was 13. The temperature was controlled to 0°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 750°C for 10 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Pr(NO3)3·6H2O and LiNO3 liquid salts doped in stoichiometric ratios of Pr and Li. After drying at 50°C for 24 hours, it was heat-treated at 200°C for 12 hours, then heat-treated at 500°C for 8.5 hours, and finally calcined at 900°C for 9 hours to produce a lithium lanthanum zirconium composite oxide solid electrolyte Li7La, doped with Li and Pr oxides at the grain boundaries and on the surface. 2.6 Zr2Pr 0.4 O12 We obtained a sample and measured its ionic conductivity, which was 5.56 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0056】 (Example 10) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M sodium hydroxide solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to 9 ± 0.2, and the pH value at the end of precipitation was 10. The temperature was controlled to 80°C to carry out the precipitation reaction. The resulting precipitate was filtered, washed, and dried. The dried product was roasted at 850°C for 8.5 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Nd(NO3)3 and LiNO3 liquid salts doped in stoichiometric ratios of Nd and Li, dried at 100°C for 12 hours, heat-treated at 530°C for 8 hours, and further calcined at 900°C for 9 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li7La, which is doped with Li and Nd oxides at the grain boundaries and on the surface. 2.2 Zr2 Nd 0.8 O 12 We obtained a sample and measured its ionic conductivity, which was 6.59 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0057】 (Example 11) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M sodium hydroxide solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to 9 ± 0.2, and the pH value at the end of precipitation was 10. The temperature was controlled to 10°C to carry out the precipitation reaction. The resulting precipitate was filtered, washed, and dried. The dried product was roasted at 650°C for 3 hours. A lithium lanthanum zirconium composite oxide solid electrolyte (Li7La) is obtained by obtaining lanthanum zirconium oxide, mixing it with lanthanum zirconium oxide and Sm(NO3)3·6H2O, a liquid salt of LiNO3 doped in a stoichiometric ratio of Sm and Li, drying at 100°C for 6 hours, then heat-treating at 500°C for 8.5 hours, further calcining at 800°C for 8 hours, and then calcining at 950°C for 4 hours, thereby doping the grain boundaries and surface with Li and Sm oxides.2.5 Zr2Sm 0.5 O 12 We obtained a sample and measured its ionic conductivity, which was 5.03 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0058】 (Example 12) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios are mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M sodium hydroxide solution are added to the reactor at a constant rate. The precipitation reaction is carried out at a controlled temperature of 50°C, with a pH of 6-10 during the precipitation process and a final pH of 11 at the precipitation endpoint. The resulting precipitate is filtered, washed, and dried. The dried product is roasted at 750°C for 10 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide is mixed with Gd(NO3)3·6H2O and LiNO3 liquid salts doped in stoichiometric ratios of Gd and Li. After drying at 100°C for 12 hours, the mixture is heat-treated at 460°C for 9 hours, and then calcined at 800°C for 15 hours to produce a lithium lanthanum zirconium composite oxide solid electrolyte (Li7La) with Li, Gd oxides, and nitrogen-containing compounds doped at the grain boundaries and on the surface. 2.5 Zr2Gd 0.5 O 11.91 N 0.06 We obtained a sample and measured its ionic conductivity, which was 8.42 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0059】 (Example 13) A stoichiometric ratio of La(NO3)3 and ZrO(NO3)2 is mixed into a 1.0 M total cation solution. Under stirring conditions, the mixture and a 3 M urea solution are added to a reactor, and the reaction temperature is controlled to 120°C to carry out a precipitation reaction. The resulting precipitate is filtered, washed, and dried. The dried product is roasted at 850°C for 8.5 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide is mixed with a liquid salt of Yb(NO3)3 and LiNO3 doped in a stoichiometric ratio of Yb and Li, dried at 100°C for 12 hours, heat-treated at 500°C for 8.5 hours, and further calcined at 800°C for 15 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li7La2Zr2YbO, in which Li and Yb oxides are doped at the grain boundaries and on the surface.12 We obtained a sample and measured its ionic conductivity, which was 6.89 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0060】 (Example 14) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M aqueous ammonia solution were added to a reactor. The pH value during the precipitation process was controlled to 8 ± 0.2, and the pH value at the end of precipitation was 10. The temperature was controlled to 40°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with TaO(NO3)3 and LiNO3 liquid salts doped in stoichiometric ratios of Ta and Li, dried at 100°C for 12 hours, heat-treated at 550°C for 8 hours, and further calcined at 700°C for 24 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, with Li and Ta oxides doped at the grain boundaries and on the surface. 6.5 La3Zr 1.5 Ta 0.5 O 12 We obtained a sample and measured its ionic conductivity, which was 5.48 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0061】 (Example 15) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.0 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M aqueous ammonia solution were added to a reactor. The pH value during the precipitation process was controlled to 7 ± 0.2, and the pH value at the end of precipitation was 9.5. The temperature was controlled to 40°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Y(NO3)3·6H2O and LiNO3 liquid salts doped in stoichiometric ratios of Y and Li, dried at 150°C for 8 hours, heat-treated at 530°C for 8 hours, and further calcined at 870°C for 9.5 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li7La, which is doped with Li and Y oxides at the grain boundaries and on the surface. 1.5 Zr2Y1.5 O 12 was obtained, and its ionic conductivity was measured to be 9.12×10 -4 S / cm (25 °C). 【0062】 (Example 16) Lanthanum nitrate (La(NO3)3) and zirconium nitrate (ZrO(NO3)2) in stoichiometric ratio were blended into a mixed solution with a total cation concentration of 1.5 M. Under stirring conditions, the mixed solution and 3 M aqueous ammonia solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to be 8 ± 0.2, the pH value at the end point of precipitation was 10, the temperature was controlled at 40 °C, and the precipitation reaction was carried out. The obtained precipitate was filtered, washed, and dried. The dried product was calcined at 800 °C for 9 h to obtain lanthanum zirconium oxide. Lanthanum zirconium oxide was mixed with liquid salts of Ta(NO3)3 and LiNO3 doped in stoichiometric ratio with Ta and Li, dried at 100 °C for 12 h, then heat-treated at 550 °C for 8 h, and further fired at 800 °C for 15 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li 6.4 La3Zr 1.6 Ta 0.6 O 12 was obtained, and its ionic conductivity was measured to be 7.75×10 -4 S / cm (25 °C). 【0063】 (Example 17) Lanthanum nitrate (La(NO3)3) and zirconium nitrate (ZrO(NO3)2) in stoichiometric ratio were blended into a mixed solution with a total cation concentration of 1.5 M. Under stirring conditions, the mixed solution and 3 M aqueous ammonia solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to be 10 ± 0.2, the pH value at the end point of precipitation was 10.5, the temperature was controlled at 50 °C, and the precipitation reaction was carried out. The obtained precipitate was filtered, washed, and dried. The dried product was calcined at 700 °C for 15 h to obtain lanthanum zirconium oxide. Lanthanum zirconium oxide was mixed with liquid salts of Cu(NO3)2 and LiNO3 doped in stoichiometric ratio with Cu and Li, dried at 100 °C for 12 h, then heat-treated at 400 °C for 15 h, and further fired at 930 °C for 8.5 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La3Zr1.2 Cu 1.6 O 12 was obtained, and its ionic conductivity was measured to be 6.83×10 -4 S / cm (25°C). 【0064】 (Example 18) Stoichiometric ratios of La(NO3)3 and ZrO(NO3)2 were incorporated into a mixed solution with a total cation concentration of 1.5 M. Under stirring conditions, the mixed solution and 3 M aqueous ammonia solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled at 8 ± 0.2, the pH value at the end point of precipitation was 10, the temperature was controlled at 40°C, and the precipitation reaction was carried out. The obtained precipitate was filtered, washed, and dried. The dried product was calcined at 800°C for 9 h to obtain lanthanum zirconium oxide. Lanthanum zirconium oxide was mixed with TaO(NO3)3 and LiNO3 liquid salts doped in stoichiometric ratios of Ta and Li, dried at 100°C for 12 h, then heat-treated at 550°C for 9 h, and further fired at 950°C for 8 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li6La3ZrTaO 12 was obtained, and its ionic conductivity was measured to be 8.35×10 -4 S / cm (25°C). 【0065】 (Example 19) Stoichiometric ratios of La(NO3)3 and ZrO(NO3)2 were incorporated into a mixed solution with a total cation concentration of 0.5 M. Under stirring conditions, the mixed solution and 3 M aqueous ammonia solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled at 4.5 - 9, the pH value at the end point of precipitation was 11, the temperature was controlled at 60°C, and the precipitation reaction was carried out. The obtained precipitate was filtered, washed, and dried. The dried product was calcined at 700°C for 15 h to obtain lanthanum zirconium oxide. Lanthanum zirconium oxide was mixed with TaO(NO3)3, NbO(NO3)3, and LiNO3 liquid salts doped in stoichiometric ratios of Ta, Nb, and Li, dried at 120°C for 10 h, then heat-treated at 580°C for 7.5 h, and further fired at 900°C for 9 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li 6.6La3Zr 1.6 Ta 0.2 Nb 0.2 O 12 We obtained a sample and measured its ionic conductivity, which was 9.89 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0066】 (Example 20) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios with a total cation concentration of 1.5M 3+ and Zr 4+ The mixture was combined with a 3M aqueous ammonia solution, and under stirring conditions, the mixture and a 3M aqueous ammonia solution were added to the reactor. The pH value during the precipitation process was controlled to 8±0.2, and the pH value at the end of precipitation was 10. The temperature was controlled to 40°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with TaO(NO3)3,LiNO3 liquid salt doped in a stoichiometric ratio of Ta and Li, dried at 100°C for 12 hours, then heat-treated at 550°C for 8 hours, and further calcined at 1100°C for 1 hour to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li and Ta oxides at the grain boundaries and on the surface. 6.6 La3Zr 1.8 Ta 0.85 O 12 We obtained a sample and measured its ionic conductivity, which was 5.09 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0067】 (Example 21) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios are mixed into a 0.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 4 M aqueous ammonia solution are added to the reactor at a constant rate. The pH value during the precipitation process is controlled to 6 ± 0.2, and the pH value at the end of precipitation is 10. The temperature is controlled to 40°C to carry out the precipitation reaction. The obtained precipitate is filtered, washed, and dried. The dried product is roasted at 850°C for 5 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide is mixed with a liquid salt of Ga(NO3)3, Al(NO3)3, and LiNO3 doped in stoichiometric ratios of Ga, Al, and Li. After drying at 100°C for 12 hours, the mixture is heat-treated at 600°C for 6 hours, and then calcined at 850°C for 10 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li, Al, and Ga oxides at the grain boundaries and on the surface. 6.1 La3Zr2Al 0.1 Ga 0.2 O 12 We obtained a sample and measured its ionic conductivity, which was 3.12 × 10⁻⁶. -3 The temperature was S / cm (at 25°C). 【0068】 (Example 22) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M aqueous ammonia solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to 6 ± 0.2, and the pH value at the end of precipitation was 12. The temperature was controlled to 40°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 750°C for 10 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with TaO(NO3)3, LiNO3, and NH4F liquid salts doped in stoichiometric ratios of Ta and Li, dried at 100°C for 12 hours, heat-treated at 550°C for 8 hours, and further calcined at 830°C for 13 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, doped with Li, Ta oxide and fluoride at the grain boundaries and surface. 6.5 La3Zr 1.5 Ta 0.5 O 11.75 F 0.5 We obtained a sample and measured its ionic conductivity, which was 8.40 × 10⁻⁶. -4The temperature was S / cm (at 25°C). 【0069】 (Example 23) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M aqueous ammonia solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to 5 ± 0.2, and the pH value at the end of precipitation was 10. The temperature was controlled to 40°C to carry out the precipitation reaction. The resulting precipitate was filtered, washed, and dried. The dried product was roasted at 750°C for 10 hours to obtain lanthanum zirconium. A lithium lanthanum zirconium composite oxide solid electrolyte is obtained by obtaining a lanthanum zirconium oxide, mixing it with lanthanum zirconium oxide and liquid salts of TaO(NO3)3, NbO(NO3)3, LiNO3, and NH4F doped in stoichiometric ratios of Ta, Nb, and Li. After drying at 100°C for 12 hours, the mixture is heat-treated at 500°C for 8.5 hours, and then calcined at 900°C for 9 hours to obtain a lithium lanthanum zirconium composite oxide solid electrolyte with Li, Ta, Nb oxides and fluorides doped at the grain boundaries and on the surface. 6.6 La3Zr 1.6 Ta 0.2 Nb 0.2 O 11.95 F 0.1 We obtained a sample and measured its ionic conductivity, which was 1.32 × 10⁻⁶. -3 The temperature was S / cm (at 25°C). 【0070】 (Example 24) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M aqueous ammonia solution were added to a reactor. The pH value during the precipitation process was controlled to 8 ± 0.2, and the pH value at the end of precipitation was 10. The temperature was controlled to 40°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with TaO(NO3)3 and LiNO3 liquid salts doped in stoichiometric ratios of Ta and Li, dried at 100°C for 12 hours, heat-treated at 550°C for 9 hours, and further calcined at 850°C for 11 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, doped with Li and Ta oxides at the grain boundaries and on the surface. 6.2 La3Zr1.8 Ta 0.8 O 12 We obtained a sample and measured its ionic conductivity, which was 8.89 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0071】 (Example 25) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.0 M total cation concentration mixture. Under stirring conditions, the mixture, along with a 3 M mixture of ammonium bicarbonate and aqueous ammonia, was added to a reactor. The pH value during the precipitation process was controlled to 8 ± 0.2, and the final pH value of the precipitate was 10. The temperature was controlled to 40°C to carry out the precipitation reaction. The resulting precipitate was filtered, washed, and dried. The dried product was roasted at 850°C for 8.5 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Eu(NO3)2 and LiNO3 liquid salts doped in stoichiometric ratios of Eu and Li, dried at 100°C for 12 hours, heat-treated at 570°C for 7.5 hours, and further calcined at 820°C for 13 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li7La3Zr, with Li and Eu oxides doped at the grain boundaries and on the surface. 1.1 EU 1.8 O 12 We obtained a sample and measured its ionic conductivity, which was 6.88 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0072】 (Example 26) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.0 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M aqueous ammonia solution were added to a reactor. The pH value during the precipitation process was controlled to 9.5 ± 0.2, and the pH value at the end of precipitation was 10. The temperature was controlled to 45°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Ti(NO3)4 and LiNO3 liquid salts doped in stoichiometric ratios of Ti and Li, dried at 100°C for 12 hours, heat-treated at 460°C for 9.5 hours, and further calcined at 860°C for 10.5 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li7La3Zr, with Li and Ti oxides doped at the grain boundaries and surface. 1.9 Ti 0.1 O 12 We obtained a sample and measured its ionic conductivity, which was 5.81 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0073】 (Example 27) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M aqueous ammonia solution were added at a constant rate to the reactor. The pH during the precipitation process was 5.5 to 11, and the pH value at the end of precipitation was 12. The temperature was controlled to 40°C to carry out the precipitation reaction. The resulting precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with a Ca(NO3)2, LiNO3 liquid salt doped in stoichiometric ratios of Ca and Li, dried at 100°C for 12 hours, heat-treated at 410°C for 13 hours, and further calcined at 840°C for 12 hours to produce a lithium lanthanum zirconium composite oxide solid electrolyte (Li7La), in which Li and Ca oxides were doped at the grain boundaries and on the surface. 1.8 Zr2Ca 1.8 O 12 We obtained a sample and measured its ionic conductivity, which was 6.12 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0074】 (Example 28) La2(SO4)3 and Zr(SO4)2 in stoichiometric ratios were mixed into a 0.5 M total cation solution. Under stirring conditions, the mixture and a 3 M aqueous ammonia solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to 7 ± 0.2, and the pH value at the end of precipitation was 11. The temperature was controlled to 40°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 850°C for 8.5 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with a liquid salt of Ga(NO3)3, Al(NO3)3, and LiNO3 doped in stoichiometric ratios of Ga, Al, and Li. After drying at 100°C for 12 hours, the mixture was heat-treated at 600°C for 6 hours, and then calcined at 850°C for 18 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li, Al, Ga oxides and sulfides at the grain boundaries and on the surface. 6.1 La3Zr2Al 0.1 Ga 0.2 O 11 S was obtained, and its ionic conductivity was measured, yielding 4.32 × 10⁻⁶. -3 The temperature was S / cm (at 25°C). 【0075】 (Example 29) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios are mixed into a 1.0 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M aqueous ammonia solution are added to a reactor. The pH value during the precipitation process is controlled to 9.5 ± 0.2, and the pH value at the end of precipitation is 10. The temperature is controlled to 45°C to carry out the precipitation reaction. The obtained precipitate is filtered, washed, and dried. The dried product is roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide is mixed with Ga(NO3)3, LiNO3, (NH4)3PO4 liquid salt doped in stoichiometric ratios of Ga and Li, dried at 100°C for 12 hours, heat-treated at 450°C for 12 hours, and further calcined at 800°C for 15 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li4La3Zr2GaO, in which Li, Ga oxide and phosphate are doped at the grain boundaries and on the surface. 10.5 P was obtained, and its ionic conductivity was measured, yielding 9.91 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0076】 (Example 30) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M aqueous ammonia solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to 8.5 ± 0.2, and the pH value at the end of precipitation was 12. The temperature was controlled to 40°C to carry out the precipitation reaction. The resulting precipitate was filtered, washed, and dried. The dried product was roasted at 750°C for 10 hours to obtain lanthanidyl. Li lanthanum zirconium composite oxide solid electrolyte is obtained by obtaining conium oxide, mixing it with lanthanum zirconium oxide and liquid salts of Ga(NO3)3, TaO(NO3)3, Ba(NO3)2, and LiNO3 doped in stoichiometric ratios of Ga, Ba, Ta, and Li, drying at 50°C for 24 hours, heat treating at 480°C for 12 hours, and then calcining at 900°C for 9 hours, thereby doping the grain boundaries and surface with Li, Ga, Ba, and Ta oxides. 6.4 Ga 0.1 La3Zr 1.55 Ta 0.4 Ba 0.05 O 12 We obtained a sample and measured its ionic conductivity, which was 8.36 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0077】 (Example 31) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3.05 M sodium hydroxide solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to 8 ± 0.2, and the pH value at the end of precipitation was 12. The temperature was controlled to 40°C to carry out the precipitation reaction. The resulting precipitate was filtered, washed, and dried. The dried product was roasted at 750°C for 10 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Al(NO3), RbNO3, and LiNO3 liquid salts doped in stoichiometric ratios of Al, Rb, and Li. After drying at 50°C for 24 hours, the mixture was heat-treated at 400°C for 15 hours, and then calcined at 900°C for 9 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li and Rb oxides at the grain boundaries and on the surface. 6.1 La 2.1 Zr2Al0.3 Rb 2.7 O 12 We obtained a sample and measured its ionic conductivity, which was 7.96 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0078】 (Example 32) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.5 M total cation concentration mixture. Under stirring conditions, the mixture and a 3.05 M sodium hydroxide solution were added to the reactor at a constant rate. The pH value during the precipitation process was controlled to 8.5 ± 0.2, and the final pH value of the precipitate was 12. The temperature was controlled to 45°C to carry out the precipitation reaction. The resulting precipitate was filtered, washed, and dried. The dried product was roasted at 750°C for 10 hours and lantanned. Lithium lanthanum zirconium oxide is obtained, and lanthanum zirconium oxide is mixed with Ge(NO3)4,LiNO3 liquid salt doped in a stoichiometric ratio of Ge and Li. After drying at 50°C for 24 hours, the mixture is heat-treated at 400°C for 14 hours, then calcined at 700°C for 16 hours, and finally calcined at 900°C for 9 hours, followed by calcination at 950°C for 8 hours to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La3Zr, which is doped with Li and Ge oxides at the grain boundaries and on the surface. 1.7 Ge 0.3 O 12 We obtained a sample and measured its ionic conductivity, which was 6.56 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0079】 (Example 33) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.0 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M aqueous ammonia solution were added to a reactor. The pH value during the precipitation process was controlled to 6.5 ± 0.2, and the pH value at the end of precipitation was 10. The temperature was controlled to 45°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Al(NO3)3, TaO(NO3)3, and LiNO3 liquid salts doped in stoichiometric ratios of Al, Ta, and Li. After drying at 100°C for 12 hours, the mixture was heat-treated at 600°C for 6 hours, and then calcined at 850°C for 11 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li, Al, and Ta oxides at the grain boundaries and on the surface. 6.2 Al 0.2 La3Zr 1.8 Ta 0.2 O 12 We obtained a sample and measured its ionic conductivity, which was 9.21 × 10⁻⁶. -4 The temperature was S / cm (at 25°C). 【0080】 (Example 34) La(NO3)3 and ZrO(NO3)2 in stoichiometric ratios were mixed into a 1.0 M total cation concentration mixture. Under stirring conditions, the mixture and a 3 M aqueous ammonia solution were added to a reactor. The pH value during the precipitation process was controlled to 9.5 ± 0.2, and the pH value at the end of precipitation was 10. The temperature was controlled to 40°C to carry out the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was roasted at 800°C for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Ga(NO3)3, RbNO3, and LiNO3 liquid salts doped in stoichiometric ratios of Ga, Rb, and Li. After drying at 100°C for 12 hours, the mixture was heat-treated at 550°C for 8.5 hours, and then calcined at 860°C for 10.5 hours to obtain lithium lanthanum zirconium composite oxide solid electrolyte Li, doped with Li, Ga, and Rb oxides at the grain boundaries and on the surface. 6.5 Ga 0.2 La 2.95 Rb 0.05 Zr2O 12 We obtained a sample and measured its ionic conductivity, which was 2.01 × 10⁻⁶.-3 The temperature was S / cm (at 25°C). 【0081】 As is clear from the above results, the lithium lanthanum zirconium composite oxide solid electrolyte obtained by employing the manufacturing method of the embodiment of the present invention exhibits significantly improved ionic conductivity compared to the oxide produced in the comparative example. 【0082】 As described above, the present invention relates to a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface, a method for producing it, and its applications. By a stepwise doping method, some doping elements are positioned at the grain boundaries and on the surface of the lithium lanthanum zirconium composite oxide solid electrolyte, improving the distribution of doping elements at the grain boundaries, reducing the number of grain boundaries, lowering the grain boundary resistance of the lithium lanthanum zirconium composite oxide, and improving the ionic conductivity of the lithium lanthanum zirconium composite oxide solid electrolyte. The grain boundary doping method provided by the technical solution of the present invention is versatile, achieving a highly efficient and low-cost reduction of the grain boundary resistance of lithium lanthanum zirconium composite oxide, thereby improving ionic conductivity, meeting the demand for doping elements for different solid electrolytes, and is suitable for large-scale applications. 【0083】 It should be understood that the above-described specific embodiments of the present invention are used merely to illustrate or interpret the principles of the present invention and do not limit the invention. Therefore, any modifications, equivalent substitutions, improvements, etc., made in circumstances that do not depart from the spirit and scope of the invention should be included within the scope of protection of the invention. Furthermore, the claims of the present invention are intended to include all variations and modifications within the scope and limitations of the claims, or in the form of equivalents of such scope and limitations.

Claims

[Claim 1] In a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface, the chemical formula of the solid electrolyte is Li ７－ｘ La ３－ｙ Zr ２－ｚ MαO １２－β D δ A lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface, wherein M comprises one or more cation-doping elements, D comprises one or more anion-doping elements, and 0 ≤ x ≤ 3, 0 ≤ y ≤ 1.5, 0 ≤ z ≤ 1, 0 < α < 3, 0 ≤ β ≤ 1.5, and 0 ≤ δ ≤ 1. [Claim 2] The lithium lanthanum zirconium composite oxide solid electrolyte doped on the grain boundaries and surface according to claim 1, characterized in that the grain boundaries and surface of the solid electrolyte contain one or more of the following: Li and M oxides, or Li and M oxides and fluorides, sulfides, nitrogen-containing compounds, phosphates, and composites thereof formed from Li, M, and D. [Claim 3] The doping element M includes one or more combinations of rare earth elements other than the cations Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, B, Al, Ga, In, Si, Ge, Sn, Sb, Bi, Se, Te, Nb, Mo, Hf, Ta, W, and La. Preferably, the doping element M includes one or more combinations of the cations Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Al, Ga, In, Ge, Sn, Sb, Te, Nb, Mo, Ta, Ce, Pr, Nd, Sm, Eu, Gd, Yb, Sc, and Y. More preferably, the doping element M includes one or more combinations of the cations Mn, Fe, Co, Ni, Al, Ga, Nb, Ta, Ce, Pr, Nd, Sm, Gd, Yb, and Y. The lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and surfaces according to claim 1 or 2, characterized in that the doping element D includes one or a combination of one or more anions N, F, P, and S. [Claim 4] In terms of moles, the molar content of doping element M is 12% or less of the molar amount of the solid electrolyte. A lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface according to any one of claims 1 to 3, characterized in that the molar content of doping element D is 5% or less of the molar amount of the solid electrolyte. [Claim 5] The lithium lanthanum zirconium composite oxide solid electrolyte according to any one of claims 1 to 3, characterized in that the lithium lanthanum zirconium composite oxide includes a garnet-type structure, with doping applied to the grain boundaries and surface. [Claim 6] Step S1 involves mixing aqueous solutions of lanthanum and zirconium compounds in stoichiometric ratios required for the product to obtain a mixed solution, adding the mixed solution and a basic substance to a reactor to carry out a precipitation reaction, and then subjecting the resulting precipitate to suction filtration, washing, drying, and roasting to obtain lanthanum zirconium oxide. A method for producing a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface, according to any one of claims 1 to 5, comprising step S2, which involves mixing the lanthanum zirconium oxide with a liquid salt of doping element M and Li in one or more steps under stirring conditions, performing one or two heat treatments after drying, and further performing one or two calcinations to obtain a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface. [Claim 7] Step S1 involves mixing lanthanum, zirconium, and an aqueous solution of M or a part of M in stoichiometric ratios required for the product to obtain a mixed solution, adding the mixed solution and a basic substance to a reactor to carry out a precipitation reaction, and then subjecting the resulting precipitate to suction filtration, washing, drying, and roasting to obtain lanthanum zirconium oxide containing M. A method for producing a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface, according to any one of claims 1 to 5, comprising: step S2, mixing a lanthanum zirconium oxide containing the aforementioned M with a liquid salt of Li or a mixed liquid salt of the remaining doping element M and Li in one or more steps under stirring conditions; performing one or two heat treatments after drying; and further performing one or two calcinations to obtain a lithium lanthanum zirconium composite oxide solid electrolyte doped at grain boundaries and on the surface. [Claim 8] The method according to 6 or 7, characterized in that all or part of Li is added in the form of a solid salt to lanthanum zirconium oxide containing M. [Claim 9] The method according to 6 or 7, characterized in that the zirconium source in the mixed solution described in step S1 includes one or more of the following: zirconium oxychloride, zirconium oxynitrate, zirconium sulfate, zirconium acetate, and zirconium citrate, and the lanthanum source includes one or more of the following: lanthanum chloride, lanthanum nitrate, lanthanum sulfate, lanthanum acetate, and lanthanum citrate. [Claim 10] The method according to 6 or 7, characterized in that the basic substance comprises magnesium bicarbonate, urea, and at least one hydroxide, carbonate, or bicarbonate of at least one element from among ammonium, sodium, and potassium, and preferably comprises at least one from among sodium hydroxide, urea, aqueous ammonia, and ammonium bicarbonate. [Claim 11] The method according to 6 or 7, characterized in that in step S1, the mixed liquid and the basic substance are added to the reactor, a precipitation reaction is carried out, the pH value during the precipitation process is controlled to be within the range of 4.5 to 14, preferably 5 to 10, the pH value at the precipitation endpoint is controlled to be 8 to 13, preferably 9 to 11, and the temperature is controlled to be 0 to 120°C, preferably 10 to 80°C. [Claim 12] The method according to 6 or 7, characterized in that the liquid salt of the doping element M, Li includes one or more combinations of nitrates, acetates, sulfates, citrates, amino acid salt molten salts, or aqueous solutions. [Claim 13] The method according to 6 or 7, characterized in that the doping element D is added in one or more steps in steps S1 and S2, and the doping element D is derived from one or more combinations of nitrates, fluorides, phosphates, sulfates, and sulfides. [Claim 14] The method according to 6 or 7, characterized in that the roasting temperature in step S1 is 600 to 1000°C and the roasting time is 1 to 24 hours. [Claim 15] The method according to 6 or 7, characterized in that the heat treatment temperature in step S2 is 200 to 750°C and the heat treatment time is 1 to 24 hours. [Claim 16] The method according to 6 or 7, characterized in that the firing temperature in step S2 is 700 to 1100°C and the firing time is 1 to 24 hours. [Claim 17] Use of a lithium lanthanum zirconium composite oxide solid electrolyte doped with grain boundaries and surfaces according to any one of claims 1 to 5 in an all-solid lithium metal or lithium-ion battery, a semi-solid lithium-ion battery, or a lithium-air battery.

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