A lithium lanthanum zirconium composite oxide solid electrolyte doped with grain boundaries and surfaces, and a preparation method and application thereof

Abstract

The present application relates to a kind of lithium lanthanum zirconium composite oxide solid electrolyte of grain boundary and surface doping and its preparation method and application.By the method of step-by-step doping, part of the doping elements are located at the grain boundary and surface of lithium lanthanum zirconium composite oxide solid electrolyte, the distribution state of doping elements at the grain boundary is improved, the number of grain boundary is reduced, the grain boundary resistance of lithium lanthanum zirconium composite oxide is reduced, and high ionic conductivity is obtained.The doping method used has the advantages of simple process, low cost and strong universality, and can meet the needs of different solid electrolytes for doping elements, and is suitable for large-scale application.The solid electrolyte obtained by the technical scheme of the present application can be used in the field of all-solid-state lithium metal or lithium ion battery, semi-solid lithium ion battery, lithium-air battery, etc.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a solid electrolyte of lithium lanthanum zirconium composite oxide with grain boundary and surface doping, its preparation method and application. This solid electrolyte can be used in all-solid-state lithium metal or lithium-ion batteries, semi-solid-state lithium-ion batteries, lithium-air batteries and other fields. Background Technology

[0002] Lithium-ion batteries, with their advantages of high operating voltage, high energy density, long cycle life, and low self-discharge rate, have become the most promising energy storage devices. However, their problems are also becoming increasingly prominent: the energy density of commercial lithium-ion batteries (liquid electrolyte) reached 260Wh / kg in 2019. -1 Liquid electrolytes are nearing their limits; they are often organic solvents, posing a risk of leakage; furthermore, they are prone to fires and other safety accidents in extreme environments, presenting significant safety hazards. Therefore, replacing liquid electrolytes with highly safe solid electrolytes is an effective strategy to address these issues. An ideal solid electrolyte should possess high ionic conductivity, stable interfacial compatibility, and good mechanical properties.

[0003] Since its successful initial preparation in 2007, lithium lanthanum zirconium oxide (LNO) has gradually become a typical representative of solid-state electrolytes, but its ionic conductivity is still two orders of magnitude lower than that of liquid electrolytes. Studies have shown that elemental doping is an effective strategy to improve the ionic conductivity of LNO. Currently, solid-state reaction methods, sol-gel methods, and chemical precipitation methods are all used to prepare LNO materials. In particular, the solid-state method has become the preferred method due to its simple preparation process and large-scale production capability. As is well known, LNO is a polycrystalline structure; therefore, the influence of grain boundaries on its ionic conductivity cannot be ignored. Existing research results show that grain boundary resistance has a negative effect on the ionic conductivity of LNO (Seungho Yu, Donald J. Siegel. Chem. Mater. 2017, 29, 9639-9647). Therefore, reducing grain boundary resistance is of great significance for improving the ionic conductivity of LNO composite oxides. David et al. hot-pressed lithium lanthanum zirconium composite oxide at 1100℃, thereby obtaining lithium lanthanum zirconium composite oxide samples with higher density (99% of theoretical density) and larger grain size, thus reducing the contribution of grain boundary resistivity to the total resistivity (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. Summary of the Invention

[0004] Based on the above-mentioned situation of the prior art, the purpose of the present invention is to provide a lithium lanthanum zirconium composite oxide solid electrolyte with grain boundary and surface doping, a preparation method and application. By grain boundary doping, the doping element can be located at the grain boundary and surface of the lithium lanthanum zirconium composite oxide solid electrolyte, which can also reduce the grain boundary resistance of the lithium lanthanum zirconium composite oxide, while having the advantages of high ionic conductivity and low cost.

[0005] To achieve the above objectives, a first aspect of the present invention provides a lithium lanthanum zirconium composite oxide solid electrolyte with grain boundary and surface doping, 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 Where M is one or more cation dopants and D is one or more anion dopants; and 0≤x≤1, 0≤y≤1.5, 0≤z≤1, 0<α<2, 0≤β≤0.5, 0≤δ≤0.5.

[0006] Furthermore, the solid electrolyte contains oxides of Li and M at its grain boundaries and surface, or one or more of the following: fluorides, sulfides, nitrogen-containing compounds, phosphates and their complexes formed by the oxides of Li and M with Li, M and D.

[0007] Furthermore, the dopant element M is one or more of the following: cations 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 rare earth elements other than La.

[0008] Preferably, the dopant element M is one or more of the following 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.

[0009] More preferably, the dopant element M is one or more of the following cations: Mn, Fe, Co, Ni, Al, Ga, Nb, Ta, Ce, Pr, Nd, Sm, Gd, Yb, and Y.

[0010] The dopant element D is one or more of the anions N, F, P, and S.

[0011] Furthermore, based on molar numbers, the molar content of dopant element M does not exceed 15% of the molar amount of the solid electrolyte;

[0012] The molar content of dopant element D does not exceed 5% of the molar amount of the solid electrolyte.

[0013] Furthermore, Li and M, or Li, M and D, exist at the grain boundaries and surface of the solid electrolyte in one or more of the forms of oxides, fluorides, sulfides, nitrogen-containing compounds, phosphates and their complexes.

[0014] Furthermore, the lithium lanthanum zirconium composite oxide has a garnet-type structure.

[0015] A second aspect of the present invention provides a method for preparing a grain boundary and surface-doped lithium lanthanum zirconium composite oxide solid electrolyte as described in the first aspect of the present invention, comprising the following steps:

[0016] S1. Mix the aqueous solutions of lanthanum and zirconium compounds in the required stoichiometric ratio to obtain a mixed solution; add the mixed solution and an alkaline substance to a reactor to carry out a precipitation reaction; filter, wash, dry and calcine the obtained precipitate to obtain lanthanum zirconium oxide;

[0017] S2. The lanthanum zirconium oxide is mixed with liquid salts of doping elements M and Li under stirring conditions, dried, and then subjected to one or two heat treatments, followed by one or two calcinations to obtain a solid electrolyte of lithium lanthanum zirconium composite oxide with grain boundaries and surface doping.

[0018] A third aspect of the present invention provides a method for preparing a grain boundary and surface-doped lithium lanthanum zirconium composite oxide solid electrolyte as described in the first aspect of the present invention, comprising the following steps:

[0019] S1. Mix lanthanum, zirconium, and an aqueous solution of M or a portion of M in the required stoichiometric ratio to obtain a mixed solution; add the mixed solution and an alkaline substance to a reactor to carry out a precipitation reaction; filter, wash, dry, and calcine the obtained precipitate to obtain lanthanum zirconium oxide containing M.

[0020] S2. The lanthanum zirconium oxide containing M is mixed with a liquid salt of Li or a mixed liquid salt of the remaining dopant element M and Li under stirring conditions, dried, and then subjected to one or two heat treatments, followed by one or two calcinations to obtain a solid electrolyte of lithium lanthanum zirconium composite oxide with grain boundaries and surface doping.

[0021] Furthermore, all or part of the Li is added to the M-containing lanthanum zirconium oxide in the form of a solid salt.

[0022] Furthermore, the zirconium source in the mixture in step S1 is one or more of zirconium oxychloride, zirconium oxynitrate, zirconium sulfate, zirconium acetate, and zirconium citrate; the lanthanum source is one or more of lanthanum chloride, lanthanum nitrate, lanthanum sulfate, lanthanum acetate, and lanthanum citrate.

[0023] Furthermore, the alkaline substance is at least one of magnesium bicarbonate, urea, and hydroxides, carbonates, or bicarbonates of at least one element selected from ammonium, sodium, and potassium; preferably, at least one of sodium hydroxide, urea, ammonia, and ammonium bicarbonate.

[0024] Furthermore, in step S1, the mixed liquid and alkaline substance are added to the reactor to carry out a precipitation reaction. The pH value during the precipitation process is controlled in the range of 4.5-14, preferably 5-10, and the pH value at the precipitation endpoint is controlled in the range of 8-13, preferably 9-11. The temperature is controlled in the range of 0-120℃, preferably 10-80℃.

[0025] Furthermore, the liquid salts of the doping elements M and Li are one or more combinations of nitrates, acetates, sulfates, citrates, and amino acid salts in molten salt or aqueous solution. The molar proportions of Li and M at the grain boundaries and surfaces are 10%-70%. The morphology and proportion of Li and M at the grain boundaries and surfaces are controlled by adjusting precipitation parameters, heat treatment of the product, and calcination temperature, time, and atmosphere.

[0026] Furthermore, dopant element D is added in one or more steps of steps S1 and S2; dopant element D comes from one or more combinations of nitrates, fluorides, phosphates, sulfates, or sulfides. The molar proportion of D at grain boundaries and surfaces is 10%-70%. The morphology and ratio of Li and M at grain boundaries and surfaces are controlled by adjusting precipitation parameters, heat treatment of the product, and calcination temperature, time, and atmosphere.

[0027] Furthermore, the calcination temperature in step S1 is 600-1000℃, preferably 700-900℃, and the calcination time is 1-24h, preferably 3-15h.

[0028] Furthermore, in step S2, the heat treatment temperature is 200-750℃, preferably 400-600℃, and the heat treatment time is 1-24h, preferably 3-15h; the drying temperature is 50-200℃, and the drying time is 1-24h.

[0029] Furthermore, the calcination temperature in step S2 is 700-1100℃, preferably 800-950℃, and the calcination time is 1-24h, preferably 3-15h.

[0030] A fourth aspect of the present invention provides the application of the grain boundary and surface doped lithium lanthanum zirconium composite oxide solid electrolyte 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.

[0031] In summary, this invention provides a grain boundary and surface-doped lithium lanthanum zirconium composite oxide solid electrolyte, its preparation method, and its applications. By employing a stepwise doping method, some dopant elements are located at the grain boundaries and surface of the lithium lanthanum zirconium composite oxide solid electrolyte, improving the distribution of dopant elements at the grain boundaries, reducing the number of grain boundaries, lowering the grain boundary resistance of the lithium lanthanum zirconium composite oxide, and increasing the ionic conductivity of the lithium lanthanum zirconium composite oxide solid electrolyte. The grain boundary and surface doping method provided by this invention is universal, achieving efficient and low-cost reduction of the grain boundary resistance of lithium lanthanum zirconium composite oxide, thereby improving the ionic conductivity, and can meet the doping element requirements of different solid electrolytes. Attached Figure Description

[0032] Figure 1 This is a flowchart of the preparation method of the lithium lanthanum zirconium composite oxide solid electrolyte with grain boundary and surface doping according to the present invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and the accompanying drawings. It should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0034] In a first aspect, the present invention provides a grain boundary and surface-doped lithium lanthanum zirconium composite oxide solid electrolyte, 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 Wherein, M is one or more cation dopants, and D is one or more anion dopants; and 0≤x≤1, 0≤y≤1.5, 0≤z≤1, 0<α<2, 0≤β≤0.5, 0≤δ≤0.5. The solid electrolyte contains oxides of Li and M at its grain boundaries and surface, or one or more of the following: fluorides, sulfides, nitrogen-containing compounds, phosphates, and their complexes formed by the oxides of Li and M with Li, M, and D. This effectively reduces the grain boundary resistance of the lithium lanthanum zirconium composite oxide, thereby effectively improving its ionic conductivity.

[0035] The dopant element M can be one or more of the following: cations 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 rare earth elements other than La; preferably, the dopant element M is one or more of the following: 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 dopant element M is one or more of the following: Mn, Fe, Co, Ni, Al, Ga, Nb, Ta, Ce, Pr, Nd, Sm, Gd, Yb, and Y.

[0036] The dopant element D can be one or a combination of more than one of the anions N, F, P, and S.

[0037] Based on molar numbers, the molar content of dopant element M does not exceed 15% of the molar amount of the solid electrolyte; the molar content of dopant element D does not exceed 5% of the molar amount of the solid electrolyte.

[0038] Furthermore, Li and M, or Li, M and D, exist at the grain boundaries and surface of the solid electrolyte in one or more of the forms of oxides, fluorides, sulfides, nitrogen-containing compounds, phosphates and their complexes.

[0039] Furthermore, the lithium lanthanum zirconium composite oxide has a garnet-type structure.

[0040] A second aspect of the present invention provides a method for preparing a grain boundary and surface-doped lithium lanthanum zirconium composite oxide solid electrolyte as described in the first aspect of the present invention, the flowchart of which is shown below. Figure 1 As shown, the preparation method is a co-precipitation method and a grain boundary doping method, including the following steps:

[0041] S1. Mix the aqueous solutions of lanthanum and zirconium compounds in the required stoichiometric ratio to obtain a mixed solution; add the mixed solution and an alkaline substance to a reactor to carry out a precipitation reaction; filter, wash, dry and calcine the obtained precipitate to obtain lanthanum zirconium oxide; in this step S1, remove impurity ions from the precipitate by washing.

[0042] S2. The lanthanum zirconium oxide is mixed with liquid salts of doping elements M and Li under stirring conditions, dried, and then subjected to one or two heat treatments, followed by one or two calcinations to obtain a solid electrolyte of lithium lanthanum zirconium composite oxide with grain boundaries and surface doping.

[0043] A third aspect of the present invention provides a method for preparing a grain boundary and surface-doped lithium lanthanum zirconium composite oxide solid electrolyte as described in the first aspect of the present invention, which can be achieved by the following steps:

[0044] S1. Mix the aqueous solutions of lanthanum, zirconium, and M or a portion of M in the required stoichiometric ratio to obtain a mixed solution; add the mixed solution and an alkaline substance to a reactor to carry out a precipitation reaction; filter, wash, dry, and calcine the obtained precipitate to obtain lanthanum zirconium oxide containing M.

[0045] S2. The lanthanum zirconium oxide containing M is mixed with a liquid salt of Li or a mixed liquid salt of the remaining dopant element M and Li under stirring conditions, dried, and then subjected to one or two heat treatments, followed by one or two calcinations to obtain a solid electrolyte of lithium lanthanum zirconium composite oxide with grain boundaries and surface doping.

[0046] In the preparation methods provided in the second and third aspects above, all or part of Li can be added to the lanthanum zirconium oxide containing M in the form of a solid salt.

[0047] In the above preparation method, step S1 mainly involves co-precipitation, and step S2 mainly involves grain boundary doping. Lithium lanthanum zirconium composite oxide solid electrolytes are prepared through co-precipitation and grain boundary doping, allowing the dopant elements to be located at the grain boundaries and surface of the lithium lanthanum zirconium composite oxide solid electrolyte. This improves the distribution of dopant elements at the grain boundaries, reduces the number of grain boundaries, lowers the grain boundary resistance of the lithium lanthanum zirconium composite oxide, and increases the ionic conductivity of the lithium lanthanum zirconium composite oxide solid electrolyte. This method is universal and can meet the dopant element requirements of different solid electrolytes.

[0048] In step S1, the zirconium source in the mixed liquid is one or a combination of zirconium oxychloride, zirconium oxynitrate, zirconium sulfate, zirconium acetate, and zirconium citrate; the lanthanum source is one or a combination of lanthanum chloride, lanthanum nitrate, lanthanum sulfate, lanthanum acetate, and lanthanum citrate; the alkaline substance is at least one of magnesium bicarbonate, urea, and hydroxides, carbonates, or bicarbonates of at least one of ammonium, sodium, and potassium; preferably, at least one of sodium hydroxide, urea, ammonia, and ammonium bicarbonate.

[0049] In step S1, the mixed liquid and alkaline substance are added to the reactor to carry out a precipitation reaction. The pH value during the precipitation process is controlled in the range of 4.5-14, preferably 5-10, and the pH value at the precipitation endpoint is controlled in the range of 8-13, preferably 9-11. The temperature is controlled in the range of 0-120℃, preferably 10-80℃.

[0050] The liquid salts of dopant element M and Li are one or more of the following: nitrate, acetate, sulfate, citrate, and amino acid salt molten salt or aqueous solution.

[0051] Dopant element D may be added in one or more steps of steps S1 and S2; dopant element D is one or more of nitrates, fluorides, phosphates, sulfates or sulfides.

[0052] The calcination temperature in step S1 can be 600-1000℃, preferably 700-900℃, and the calcination time is 1-24h, preferably 3-15h.

[0053] The heat treatment temperature in step S2 can be 200-750℃, preferably 400-600℃, and the heat treatment time is 1-24h, preferably 3-15h; the drying temperature is 50-200℃, and the drying time is 1-24h; the calcination temperature is 700-1100℃, preferably 800-950℃, and the calcination time is 1-24h, preferably 3-15h. The morphology and ratio of Li and M at the grain boundaries and surface are controlled by adjusting precipitation parameters, heat treatment and calcination temperature, time, and atmosphere. To meet the specific requirements of different applications for electrolyte performance, it is necessary to adjust or change the type of dopant elements and the microstructure of the electrolyte, thus requiring different heat treatment regimes, such as step-by-step heat treatment, to allow more, more uniform, and stable dopant elements to enter the grain boundaries and surface. Water washing and water quenching can also be performed between the two heat treatment steps. The lithium lanthanum zirconium composite oxide obtained above can also be calcined twice to effectively control its particle size and dispersibility. After one calcination, ball milling and surface treatment can be performed to prevent secondary sintering and agglomeration.

[0054] A fourth aspect of this invention provides the application of the lithium lanthanum-zirconium composite oxide solid electrolyte as described in the first aspect of this invention in the fields of all-solid-state lithium metal or lithium-ion batteries, semi-solid-state lithium-ion batteries, and lithium-air batteries. The lithium lanthanum-zirconium composite oxide solid electrolyte of this invention, when applied to solid-state lithium metal or lithium-ion batteries, semi-solid-state lithium-ion batteries, and lithium-air batteries, can achieve higher energy density and better safety performance.

[0055] The lithium lanthanum zirconium composite oxide solid electrolyte powder doped at grain boundaries and surfaces can be prepared into ceramics by methods such as casting or thermal methods. It can also be mixed with polymers or, through structural design, prepared into a layered composite solid electrolyte with higher matching degree with electrode materials.

[0056] The present invention will be further described below through specific embodiments.

[0057] Comparative Example 1

[0058] A mixed solution with a total cation concentration of 1.5 M was prepared by mixing La(NO3)3, ZrO(NO3)2, and Mn(NO3)2 with water according to the stoichiometric ratio. Under stirring conditions, the mixed solution and a 3.0 M ammonia solution were added to the reactor at a uniform rate. The pH value during the precipitation process was controlled at 7 ± 0.2, with a final pH value of 13, and the temperature was controlled at 50℃. The resulting precipitate was filtered, washed, and dried. The dried product was calcined at 800℃ for 9 h to obtain lanthanum zirconium oxide. Li2CO3 was ball-milled and mixed uniformly with the lanthanum zirconium oxide, and then calcined at 900℃ for 9 h to obtain a solid electrolyte of lithium lanthanum zirconium composite oxide with bulk Mn doped, Li7La3Zr. 1.8 Mn 0.2 O 12 Its ionic conductivity was measured to be 1.89 × 10⁻⁶. -4 S / cm (25℃).

[0059] Example 1

[0060] A mixed solution with a total cation concentration of 1.5 M was prepared by dissolving La(NO3)3 and ZrO(NO3)2 in water according to a stoichiometric ratio. Under stirring conditions, the mixed solution and a 3.0 M ammonia solution were added to the reactor at a uniform rate. The pH value during the precipitation process was controlled at 7 ± 0.2, with a final pH value of 13, and the temperature was controlled at 50 °C for the precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was calcined at 800 °C for 9 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of Mn(NO3)2 and LiNO3 in a stoichiometric ratio (doped with Mn and Li), dried at 100 °C for 12 h, then heat-treated at 450 °C for 10 h, and finally calcined at 900 °C for 9 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La3Zr, doped with Mn and Li oxides at grain boundaries and surfaces. 1.8 Mn 0.2 O 12 Its ionic conductivity was measured to be 5.03 × 10⁻⁶. -4 S / cm (25℃).

[0061] Example 2

[0062] A mixed solution with a total cation concentration of 0.5 M was prepared by stoichiometrically using La2(SO4)3 and Zr(SO4)2. Under stirring, the mixed solution and a 3.0 M ammonia solution were added to the reactor at a uniform rate. The pH value during precipitation was controlled at 9 ± 0.2, with a final pH value of 10, and the temperature was controlled at 50 °C. The precipitate was filtered, washed, and dried. The dried product was calcined at 850 °C for 8.5 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Al(NO3)3 and LiNO3 liquid salts doped with Al and Li, dried at 100 °C for 12 h, then heat-treated at 420 °C for 12 h, and finally calcined at 820 °C for 10 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li, Al oxides, and sulfides at grain boundaries and surfaces. 6.25 La3Zr2Al 0.25 O 11.9 S 0.1 Its ionic conductivity was measured to be 6.01 × 10⁻⁶. -4 S / cm (25℃).

[0063] Example 3

[0064] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and a 3.0 M ammonia solution were added to the reactor at a uniform rate. The precipitation process was carried out at pH 5-9, with a final pH of 11, and the temperature was controlled at 50℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 800℃ for 9 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Fe(NO3)3 and LiNO3 liquid salts doped with Fe and Li in stoichiometric ratios, dried at 100℃ for 12 h, then heat-treated at 200℃ for 12 h, followed by heat-treated at 500℃ for 5 h, and finally calcined at 860℃ for 9.5 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li, doped with Li and Fe oxides at grain boundaries and surfaces. 6.7 La3Zr2Fe 0.1 O 12 Its ionic conductivity was measured to be 6.25 × 10⁻⁶. -4 S / cm (25℃).

[0065] Example 4

[0066] A mixed solution with a total cation concentration of 1.0 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and a 3.0 M ammonia solution were added to the reactor at a uniform rate. The pH value during the precipitation process was controlled at 8 ± 0.2, with a final pH value of 9.5, and the temperature was controlled at 50℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 800℃ for 9 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of Co(NO3)2 and LiNO3 in a stoichiometric ratio (doped with Co and Li), dried at 80℃ for 18 h, then heat-treated at 550℃ for 8 h, calcined at 800℃ for 8 h, and finally calcined at 950℃ for 7 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte, Li7La3Zr, doped with Li and Co oxides at grain boundaries and surface. 1.5 Co 0.5 O 12 Its ionic conductivity was measured to be 5.86 × 10⁻⁶. -4 S / cm (25℃).

[0067] Example 5

[0068] A mixed solution with a total cation concentration of 1.0 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and a 4.0 M ammonia solution were added to the reactor at a uniform rate. The pH during the precipitation process was 9-12, the final pH was 9, and the temperature was controlled at 50℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 900℃ for 8 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Ni(CH3COO)2 and CH3COOLi liquid salts doped with Ni and Li, dried at 100℃ for 12 hours, then heat-treated at 680℃ for 6.5 hours, and finally calcined at 900℃ for 9 hours to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La3Zr, which is doped with Li and Ni oxides at the grain boundaries and surface. 1.8 Ni 0.4 O 12 Its ionic conductivity was measured to be 5.36 × 10⁻⁶. -4 S / cm (25℃).

[0069] Example 6

[0070] A mixed solution with a total cation concentration of 0.5 M was prepared by stoichiometrically using La(CH3COO)3 and Zr(CH3COO)4. Under stirring, the mixed solution and a 3.5 M ammonia solution were added to the reactor at a uniform rate. The pH value during precipitation was controlled at 8 ± 0.2, with a final pH value of 11, and the temperature was controlled at 50 °C. The precipitate was filtered, washed, and dried. The dried product was calcined at 800 °C for 9 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Ga(NO3)3 and LiNO3 liquid salts doped with Ga and Li in stoichiometric ratios, dried at 100 °C for 12 h, then heat-treated at 600 °C for 6 h, and finally calcined at 920 °C for 8.5 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte, Li, which is doped with Li and Ga oxides at the grain boundaries and surface. 6.4 La3Zr2Ga 0.2 O 12 Its ionic conductivity was measured to be 1.14 × 10⁻⁶. -3 S / cm (25℃).

[0071] Example 7

[0072] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring, the mixed solution and 3 M sodium hydroxide solution were added to the reactor at a uniform rate. The pH during the precipitation process was 10-14, with a final pH of 10, and the temperature was controlled at 60℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 600℃ for 24 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with NbO(NO3)3, LiNO3, and NH4F liquid salt in a stoichiometric ratio of Nb and Li, dried at 100℃ for 12 h, then heat-treated at 750℃ for 1 h, and finally calcined at 940℃ for 8 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li, Nb oxides, and fluorides at the grain boundaries and surface. 6.3 La3Zr 1.4 Nb 0.7 O 11.75 F 0.5 Its ionic conductivity was measured to be 9.65 × 10⁻⁶. -4 S / cm (25℃).

[0073] Example 8

[0074] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M sodium hydroxide solution were added to the reactor at a uniform rate. The pH value during precipitation was controlled at 8 ± 0.2, with a final pH value of 9.5, and the temperature was controlled at 50℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 1000℃ for 1 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Ce(NO3)3, LiNO3, and (NH4)3PO4 liquid salts doped with Ce and Li in stoichiometric ratios, dried at 200℃ for 1 h, then heat-treated at 300℃ for 20 h, and finally calcined at 900℃ for 9 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li, Ce oxides, and phosphates at the grain boundaries and surface. 6.8 La 2.8 Zr2Ce 0.2 O 11.7 P 0.2 Its ionic conductivity was measured to be 7.08 × 10⁻⁶. -4 S / cm (25℃).

[0075] Example 9

[0076] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3.05 M sodium hydroxide solution were added to the reactor at a uniform rate. The pH value during precipitation was controlled at 8 ± 0.2, the final pH value at precipitation endpoint was 12, and the temperature was controlled at 0℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 750℃ for 10 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Pr(NO3)3·6H2O and LiNO3 liquid salt in a stoichiometric ratio of Pr and Li, dried at 50℃ for 24 h, then heat-treated at 200℃ for 24 h, and finally calcined at 900℃ for 9 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La, which is doped with Li and Pr oxides at grain boundaries and surfaces. 2.6 Zr2Pr 0.4 O 12 Its ionic conductivity was measured to be 5.56 × 10⁻⁶. -4 S / cm (25℃).

[0077] Example 10

[0078] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring, the mixed solution and 3 M sodium hydroxide solution were added to the reactor at a uniform rate. The pH value during precipitation was controlled at 9 ± 0.2, with a final pH of 10, and the temperature was controlled at 80℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 850℃ for 8.5 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Nd(NO3)3 and LiNO3 liquid salts doped with Nd and Li in a stoichiometric ratio, dried at 100℃ for 12 h, then heat-treated at 530℃ for 8 h, and finally calcined at 900℃ for 9 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La, which is doped with Li and Nd oxides at grain boundaries and surfaces. 2.2 Zr2Nd 0.8 O 12 Its ionic conductivity was measured to be 5.89 × 10⁻⁶. -4 S / cm (25℃).

[0079] Example 11

[0080] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M sodium hydroxide solution were added to the reactor at a uniform rate. The pH value during precipitation was controlled at 9 ± 0.2, the final pH value at precipitation endpoint was 10, and the temperature was controlled at 10℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 650℃ for 3 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Sm(NO3)3·6H2O and LiNO3 liquid salt in a stoichiometric ratio of Sm and Li, dried at 100℃ for 12 h, then heat-treated at 500℃ for 8.5 h, and finally calcined at 800℃ for 15 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La, which is doped with Li and Sm oxides at grain boundaries and surfaces. 2.5 Zr2Sm 0.5 O 12 Its ionic conductivity was measured to be 6.03 × 10⁻⁶. -4 S / cm (25℃).

[0081] Example 12

[0082] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring, the mixed solution and 3 M sodium hydroxide solution were added to the reactor at a uniform rate. The pH during precipitation was 6-10, the final pH was 11, and the temperature was controlled at 50℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 750℃ for 10 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of Gd(NO3)3·6H2O and LiNO3 in a stoichiometric ratio (doped with Gd and Li), dried at 100℃ for 12 h, then heat-treated at 460℃ for 9 h, and finally calcined at 800℃ for 15 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La, which is doped with Li, Gd oxides, and nitrogen-containing compounds at grain boundaries and surfaces. 2.5 Zr2Gd 0.5 O 11.7 N 0.2 Its ionic conductivity was measured to be 8.42 × 10⁻⁶. -4 S / cm (25℃).

[0083] Example 13

[0084] A mixed solution with a total cation concentration of 1.0 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M urea solution were added to a reactor, and the reaction temperature was controlled at 120℃ to carry out a precipitation reaction. The obtained precipitate was filtered, washed, and dried. The dried product was calcined at 850℃ for 8.5 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of Yb(NO3)3 and LiNO3 in a stoichiometric ratio of doped Yb and Li, dried at 100℃ for 12 h, then heat-treated at 500℃ for 8.5 h, and finally calcined at 800℃ for 15 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte, Li7La2Zr2YbO, which is doped with Li and Yb oxides at grain boundaries and surfaces. 12 Its ionic conductivity was measured to be 6.89 × 10⁻⁶. -4 S / cm (25℃).

[0085] Example 14

[0086] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M ammonia solution were added to the reactor. The pH value during precipitation was controlled at 8 ± 0.2, the final pH value at precipitation endpoint was 10, and the temperature was controlled at 40℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 800℃ for 9 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of TaO(NO3)3 and LiNO3 in a stoichiometric ratio (doped with Ta and Li), dried at 100℃ for 12 h, then heat-treated at 550℃ for 8 h, and finally calcined at 700℃ for 24 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte, Li, which is doped with Li and Ta oxides at grain boundaries and surfaces. 6.5 La3Zr 1.5 Ta 0.5 O 12 Its ionic conductivity was measured to be 5.88 × 10⁻⁶. -4 S / cm (25℃).

[0087] Example 15

[0088] A mixed solution with a total cation concentration of 1.0 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M ammonia solution were added to the reactor. The pH value during precipitation was controlled at 7 ± 0.2, the final pH value at precipitation endpoint was 9.5, and the temperature was controlled at 40℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 800℃ for 9 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Y(NO3)3·6H2O and LiNO3 liquid salt in a Y / Li stoichiometric ratio, dried at 150℃ for 8 h, then heat-treated at 530℃ for 8 h, and finally calcined at 870℃ for 9.5 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La, doped with Li and Y oxides at grain boundaries and surface. 1.5 Zr2Y 1.5 O 12 Its ionic conductivity was measured to be 9.12 × 10⁻⁶. -4 S / cm (25℃).

[0089] Example 16

[0090] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M ammonia solution were added to the reactor at a uniform rate. The pH value during precipitation was controlled at 8 ± 0.2, the final pH value at precipitation endpoint was 10, and the temperature was controlled at 40℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 800℃ for 9 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of TaO(NO3)3 and LiNO3 in a stoichiometric ratio (doped with Ta and Li), dried at 100℃ for 12 h, then heat-treated at 550℃ for 8 h, and finally calcined at 800℃ for 15 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte, Li, which is doped with Li and Ta oxides at grain boundaries and surfaces. 6.4 La3Zr 1.6 Ta 0.6 O 12 Its ionic conductivity was measured to be 7.75 × 10⁻⁶. -4 S / cm (25℃).

[0091] Example 17

[0092] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M ammonia solution were added to the reactor at a uniform rate. The pH value during precipitation was controlled at 10 ± 0.2, the final pH value at precipitation endpoint was 10.5, and the temperature was controlled at 50℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 700℃ for 15 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with Cu(NO3)2 and LiNO3 liquid salts doped with Cu and Li in stoichiometric ratios, dried at 100℃ for 12 h, then heat-treated at 400℃ for 15 h, and finally calcined at 930℃ for 8.5 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La3Zr, doped with Li and Cu oxides at grain boundaries and surface. 1.2 Cu 1.6 O 12 Its ionic conductivity was measured to be 5.23 × 10⁻⁶. -4 S / cm (25℃).

[0093] Example 18

[0094] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M ammonia solution were added to the reactor at a uniform rate. The pH value during precipitation was controlled at 8 ± 0.2, the final pH value at precipitation endpoint was 10, and the temperature was controlled at 40℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 800℃ for 9 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of TaO(NO3)3 and LiNO3 in a stoichiometric ratio (doped with Ta and Li), dried at 100℃ for 12 h, then heat-treated at 550℃ for 9 h, and finally calcined at 950℃ for 8 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte, Li6La3ZrTaO, doped with Li and Ta oxides at grain boundaries and surfaces. 12 Its ionic conductivity was measured to be 8.35 × 10⁻⁶. -4 S / cm (25℃).

[0095] Example 19

[0096] A mixed solution with a total cation concentration of 0.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring, the mixed solution and 3 M ammonia solution were added to the reactor at a uniform rate. The precipitation process was carried out at pH 4.5-9, with a final pH of 11, and the temperature was controlled at 60℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 700℃ for 15 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of TaO(NO3)3, NbO(NO3)3, and LiNO3 in a stoichiometric ratio of Ta, Nb, and Li. The mixture was dried at 120℃ for 10 h, then heat-treated at 580℃ for 7.5 h, and finally calcined at 900℃ for 9 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte, Li, which is doped with Li, Nb, and Ta oxides at the grain boundaries and surface. 6.6 La3Zr 1.6 Ta 0.2 Nb 0.2 O 12 Its ionic conductivity was measured to be 9.89 × 10⁻⁶. -4 S / cm (25℃).

[0097] Example 20

[0098] La(NO3)3 and ZrO(NO3)2 were prepared according to stoichiometric ratios to form a La solution with a total cation concentration of 1.5 M. 3+ and Zr 4+A mixed solution was prepared by adding a 3M ammonia solution to a reactor under stirring conditions. The pH value was controlled at 8±0.2 during the precipitation process, with a final pH value of 10. The temperature was controlled at 40℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 800℃ for 9 hours to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of TaO(NO3)3 and LiNO3 in a stoichiometric ratio of Ta and Li. The mixture was dried at 100℃ for 12 hours, then heat-treated at 550℃ for 8 hours, and finally calcined at 1100℃ for 1 hour to obtain a lithium lanthanum zirconium composite oxide solid electrolyte, Li, which is doped with Li and Ta oxides at the grain boundaries and surface. 6.15 La3Zr 1.85 Ta 0.85 O 12 Its ionic conductivity was measured to be 7.09 × 10⁻⁶. -4 S / cm (25℃).

[0099] Example 21

[0100] A mixed solution with a total cation concentration of 0.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M ammonia solution were added to the reactor at a uniform rate. The pH value during precipitation was controlled at 7 ± 0.2, the final pH value at precipitation endpoint was 13, and the temperature was controlled at 40℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 950℃ for 5 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of Ga(NO3)3, Al(NO3)3, and LiNO3 in a stoichiometric ratio of Ga, Al, and Li. The mixture was dried at 100℃ for 12 h, then heat-treated at 700℃ for 6 h, and finally calcined at 750℃ for 18 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li, Al, and Ga oxides at grain boundaries and surfaces. 6.1 La3Zr2Al 0.1 Ga 0.2 O 12 Its ionic conductivity was measured to be 3.12 × 10⁻⁶. -3 S / cm (25℃).

[0101] Example 22

[0102] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M ammonia solution were added to the reactor at a uniform rate. The pH value during precipitation was controlled at 6 ± 0.2, the final pH value at precipitation endpoint was 12, and the temperature was controlled at 40℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 750℃ for 10 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with TaO(NO3)3, LiNO3, and NH4F liquid salt in a stoichiometric ratio of Ta and Li, dried at 100℃ for 12 h, then heat-treated at 650℃ for 9 h, and finally calcined at 730℃ for 20 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li, Ta oxides, and fluorides at grain boundaries and surfaces. 6.5 La3Zr 1.5 Ta 0.5 O 11.75 F 0.5 Its ionic conductivity was measured to be 8.40 × 10⁻⁶. -4 S / cm (25℃).

[0103] Example 23

[0104] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M ammonia solution were added to the reactor at a uniform rate. The pH value during precipitation was controlled at 5 ± 0.2, the final pH value at precipitation endpoint was 10, and the temperature was controlled at 40℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 750℃ for 10 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of TaO(NO3)3, NbO(NO3)3, LiNO3, and NH4F in a stoichiometric ratio of Ta, Nb, and Li. The mixture was dried at 100℃ for 12 h, then heat-treated at 500℃ for 8.5 h, and finally calcined at 900℃ for 9 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li, which is doped with Li, Ta, Nb oxides, and fluorides at grain boundaries and surfaces. 6.6 La3Zr 1.6 Ta 0.2 Nb 0.2 O 11.95 F 0.1 Its ionic conductivity was measured to be 1.32 × 10⁻⁶. -3 S / cm (25℃).

[0105] Example 24

[0106] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M ammonia solution were added to the reactor. The pH value during precipitation was controlled at 8 ± 0.2, the final pH value at precipitation endpoint was 10, and the temperature was controlled at 40℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 800℃ for 9 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of TaO(NO3)3 and LiNO3 in a stoichiometric ratio (doped with Ta and Li), dried at 100℃ for 12 h, then heat-treated at 550℃ for 9 h, and finally calcined at 850℃ for 11 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte, Li, which is doped with Li and Ta oxides at grain boundaries and surfaces. 6.2 La3Zr 1.8 Ta 0.8 O 12 Its ionic conductivity was measured to be 8.89 × 10⁻⁶. -4 S / cm (25℃).

[0107] Example 25

[0108] A mixed solution with a total cation concentration of 1.0 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, a mixed solution of the mixture, 3 M ammonium bicarbonate, and ammonia was added to the reactor. The pH value during precipitation was controlled at 8 ± 0.2, the final pH value at precipitation endpoint was 10, and the temperature was controlled at 40℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 850℃ for 8.5 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of Eu(NO3)2 and LiNO3 in a stoichiometric ratio (doped with Eu and Li), dried at 100℃ for 12 h, then heat-treated at 570℃ for 7.5 h, and finally calcined at 820℃ for 13 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La3Zr, doped with Li and Eu oxides at grain boundaries and surface. 1.1 Eu 1.8 O 12 Its ionic conductivity was measured to be 4.88 × 10⁻⁶. -4 S / cm (25℃).

[0109] Example 26

[0110] A mixed solution with a total cation concentration of 1.0 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M ammonia solution were added to the reactor. The pH value during precipitation was controlled at 9.5 ± 0.2, the final pH value at precipitation endpoint was 10, and the temperature was controlled at 45℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 800℃ for 9 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of Ti(NO3)4 and LiNO3 in a stoichiometric ratio of Ti and Li, dried at 100℃ for 12 h, then heat-treated at 460℃ for 9.5 h, and finally calcined at 860℃ for 10.5 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La3Zr, doped with Li and Ti oxides at grain boundaries and surfaces. 1.9 Ti 0.1 O 12 Its ionic conductivity was measured to be 5.01 × 10⁻⁶. -4 S / cm (25℃).

[0111] Example 27

[0112] A mixed solution with a total cation concentration of 1.5 M was prepared by stoichiometric ratio of La(NO3)3 and ZrO(NO3)2. Under stirring conditions, the mixed solution and 3 M ammonia solution were added to the reactor at a uniform rate. The pH during precipitation was 5.5-11, the final pH was 12, and the temperature was controlled at 40℃. The precipitate was filtered, washed, and dried. The dried product was calcined at 800℃ for 9 h to obtain lanthanum zirconium oxide. The lanthanum zirconium oxide was mixed with liquid salts of Ca(NO3)2 and LiNO3 in a Ca / Li stoichiometric ratio, dried at 100℃ for 12 h, then heat-treated at 410℃ for 13 h, and finally calcined at 840℃ for 12 h to obtain a lithium lanthanum zirconium composite oxide solid electrolyte Li7La, which is doped with Li and Ca oxides at grain boundaries and surfaces. 1.8 Zr2Ca 1.8 O 12 Its ionic conductivity was measured to be 5.12 × 10⁻⁶. -4 S / cm (25℃).

[0113] As can be seen from the above results, the lithium lanthanum zirconium composite oxide solid electrolyte prepared by the method of the present invention has significantly improved ionic conductivity compared with the oxide prepared in the comparative example.

[0114] In summary, this invention relates to a grain boundary and surface-doped lithium lanthanum zirconium composite oxide solid electrolyte, its preparation method, and its applications. By employing a stepwise doping method, some dopant elements are located at the grain boundaries and surface of the lithium lanthanum zirconium composite oxide solid electrolyte, improving the distribution of dopant elements at the grain boundaries, reducing the number of grain boundaries, lowering the grain boundary resistance of the lithium lanthanum zirconium composite oxide, and increasing the ionic conductivity of the lithium lanthanum zirconium composite oxide solid electrolyte. The grain boundary doping method provided by this invention is universal, achieving efficient and low-cost reduction of the grain boundary resistance of lithium lanthanum zirconium composite oxide, thereby improving ionic conductivity. It can meet the doping element requirements of different solid electrolytes and is suitable for large-scale applications.

[0115] It should be understood that the specific embodiments described above are merely illustrative or explanatory of the principles of the invention and do not constitute a limitation thereof. Therefore, any modifications, equivalent substitutions, improvements, etc., made without departing from the spirit and scope of the invention should be included within the protection scope of the invention. Furthermore, the appended claims are intended to cover all variations and modifications falling within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A solid-state electrolyte of lithium lanthanum zirconium composite oxide doped at grain boundaries and on the surface, characterized in that, The chemical formula of the solid electrolyte is Li 7-x La 3-y Zr 2-z M α O 12-β D δ Wherein, M is one or more cation doping elements, and D is one or more anion doping elements; the grain boundaries and surface of the solid electrolyte contain oxides of Li and M, or one or more of the following: fluorides, sulfides, nitrogen-containing compounds, phosphates and their complexes formed by oxides of Li and M with Li, M and D. And 0≤x≤1, 0≤y≤1.5, 0≤z≤1, 0<α<2, 0≤β≤0.5, 0<δ≤0.5; the preparation method of the lithium lanthanum zirconium composite oxide solid electrolyte with grain boundary and surface doping includes the following steps: S1. Mix the aqueous solutions of lanthanum and zirconium compounds in the required stoichiometric ratio to obtain a mixed solution; add the mixed solution and an alkaline substance to a reactor to carry out a precipitation reaction; filter, wash, dry and calcine the obtained precipitate to obtain lanthanum zirconium oxide; S2. The lanthanum zirconium oxide is mixed with liquid salts of doping elements M and Li under stirring conditions, dried, and then subjected to one or two heat treatments, followed by one or two calcinations to obtain a solid electrolyte of lithium lanthanum zirconium composite oxide with grain boundaries and surface doping.

2. The lithium lanthanum zirconium composite oxide solid electrolyte with grain boundary and surface doping according to claim 1, characterized in that, The dopant element M is one or more of the following: cations 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 rare earth elements other than La; The dopant element D is one or more of the anions N, F, P and S.

3. The lithium lanthanum zirconium composite oxide solid electrolyte with grain boundary and surface doping according to claim 2, characterized in that, The dopant element M is one or more of the following 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.

4. The lithium lanthanum zirconium composite oxide solid electrolyte with grain boundary and surface doping according to claim 3, characterized in that, The dopant element M is one or more of the following cations: Mn, Fe, Co, Ni, Al, Ga, Nb, Ta, Ce, Pr, Nd, Sm, Gd, Yb, and Y.

5. The lithium lanthanum zirconium composite oxide solid electrolyte with grain boundary and surface doping according to claim 1 or 2, characterized in that, The molar content of dopant element M, measured by molar number, does not exceed 15% of the molar amount of the solid electrolyte. The molar content of dopant element D does not exceed 5% of the molar amount of the solid electrolyte.

6. The lithium lanthanum zirconium composite oxide solid electrolyte with grain boundary and surface doping according to claim 1 or 2, characterized in that, The lithium lanthanum zirconium composite oxide has a garnet-type structure.

7. A method for preparing a grain boundary and surface-doped lithium lanthanum zirconium composite oxide solid electrolyte as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. Mix lanthanum, zirconium, and part of the aqueous solution of compound M in the required stoichiometric ratio to obtain a mixed solution; add the mixed solution and an alkaline substance to a reactor to carry out a precipitation reaction; filter, wash, dry, and calcine the obtained precipitate to obtain lanthanum zirconium oxide containing M. S2. The lanthanum zirconium oxide containing M is mixed with a mixed liquid salt of the remaining dopant elements M and Li under stirring conditions, dried, and then subjected to one or two heat treatments, followed by one or two calcinations to obtain a solid electrolyte of lithium lanthanum zirconium composite oxide with grain boundaries and surface doping.

8. The method according to claim 7, characterized in that, The zirconium source in the mixture in step S1 is one or a combination of zirconium oxychloride, zirconium oxynitrate, zirconium sulfate, zirconium acetate, and zirconium citrate; the lanthanum source is one or a combination of lanthanum chloride, lanthanum nitrate, lanthanum sulfate, lanthanum acetate, and lanthanum citrate.

9. The method according to claim 7, characterized in that, The alkaline substance is at least one of magnesium bicarbonate, urea, and hydroxides, carbonates, or bicarbonates of at least one of the elements selected from ammonium, sodium, and potassium.

10. The method according to claim 9, characterized in that, The alkaline substance is at least one of sodium hydroxide, urea, ammonia, and ammonium bicarbonate.

11. The method according to claim 7, characterized in that, In step S1, the mixed liquid and alkaline substance are added to the reactor to carry out a precipitation reaction. The pH value during the precipitation process is controlled within the range of 4.5-14; the pH value at the precipitation endpoint is controlled within the range of 8-13; and the temperature is controlled within the range of 0-120℃.

12. The method according to claim 11, characterized in that, The pH value during the precipitation process is controlled within the range of 5-10; the pH value at the precipitation endpoint is controlled within the range of 9-11; and the temperature is controlled within the range of 10-80℃.

13. The method according to claim 7, characterized in that, The liquid salts of the doping elements M and Li are one or more combinations of nitrates, acetates, sulfates, citrates, and amino acid salts in molten salt or aqueous solution.

14. The method according to claim 7, characterized in that, Dopant element D is added in one or more steps of steps S1 and S2; dopant element D comes from one or more combinations of nitrates, fluorides, phosphates, sulfates and sulfides.

15. The method according to claim 7, characterized in that, The roasting temperature in step S1 is 600-1000℃, and the roasting time is 1-24 h.

16. The method according to claim 15, characterized in that, The roasting temperature in step S1 is 700-900℃, and the roasting time is 3-15 h.

17. The method according to claim 7, characterized in that, The heat treatment temperature in step S2 is 200-750℃, and the heat treatment time is 1-24 h.

18. The method according to claim 17, characterized in that, The heat treatment temperature in step S2 is 400-600℃, and the heat treatment time is 3-15 h.

19. The method according to claim 7, characterized in that, The calcination temperature in step S2 is 700-1100℃, and the calcination time is 1-24 h.

20. The method according to claim 19, characterized in that, The calcination temperature in step S2 is 800-950℃, and the calcination time is 3-15 h.

21. The application of the grain boundary and surface doped lithium lanthanum zirconium composite oxide solid electrolyte as described in any one of claims 1-6 in all-solid-state lithium metal or lithium-ion batteries, semi-solid-state lithium-ion batteries, and lithium-air batteries.

Images