A novel garnet-type solid electrolyte with microcrystalline glass grain boundaries and its preparation method

Abstract

This invention relates to the field of solid electrolyte preparation technology, specifically to a novel garnet-type solid electrolyte with microcrystalline glass grain boundaries and its preparation method, comprising microcrystalline glass and a garnet-type cubic phase Li7La3Zr2O. 12 Solid electrolyte. The novel garnet-type solid electrolyte of this invention, with microcrystalline glass grain boundaries, possesses both high room-temperature ionic conductivity and low electronic conductivity, along with superior electrochemical stability and good wettability with lithium anodes. It exhibits three-dimensional continuity, enabling better suppression of electrons and promotion of ion transport, thus achieving a better suppression effect on lithium dendrites. The preparation method of this invention is simple and suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of solid electrolyte preparation technology, specifically to a novel garnet-type solid electrolyte with microcrystalline glass grain boundaries and its preparation method. Background Technology

[0002] As a crucial component of new energy vehicles, batteries play a decisive role in vehicle performance. Among various battery types, lithium-ion batteries are widely used due to their advantages such as high energy density, low self-discharge, and long cycle life. However, lithium-ion batteries suffer from problems such as the flammability of their liquid electrolyte, limited pressure window, and poor compatibility with high-capacity electrode materials, making it difficult to meet the development requirements of new lithium batteries with higher safety and higher energy density.

[0003] In contrast, all-solid-state lithium batteries use solid electrolytes instead of organic electrolytes, which is expected to fundamentally solve the safety hazards of lithium-ion batteries, further improve energy density, and simplify battery assembly. Among many solid lithium-ion electrolytes, Li7La3Zr2O with a garnet structure is particularly promising. 12 (LLZO) has a high room temperature ionic conductivity (>10). -4 LLZO is considered one of the most promising solid electrolytes due to its advantages such as high S / cm, a wide electrochemical window (≥5.5V / Li), and stability in contact with metallic lithium. However, LLZO has a high electronic conductivity (10 S / cm). -8 610 -7 The low ionic conductivity (F. Han, ASWestover, J. Yue, et al., Nature Energy, 2019, 4: 187-196) and the Li2CO3 formed on its surface in air atmosphere (low room temperature ionic conductivity, narrow voltage window, and insufficient contact with the lithium anode) (H. Huo, J. Luo, V. Thangadurai, et al., ACS Energy Letters, 2020, 5: 252-262) will lead to lithium dendrite growth, thus affecting battery performance and resulting in a low critical current density (61 mA / cm). 2 This falls far short of the national standard GB / T-31467.2-2015 (≥4mA / cm) for lithium-ion power batteries used in electric vehicles. 2 This severely limits the commercial use of LLZO.

[0004] In recent years, researchers have made many attempts to improve the critical current density of LLZO, for example, by incorporating elements with higher ionic conductivity (610). -6 (S / cm) and low electronic conductivity (≤10) -12LiPON (S / cm) is deposited on the surface of LLZO to reduce electron transport capacity and cover lithium carbonate to improve the interfacial contact between LLZO and lithium anode (EMHitz, H.Xie, Y.Lin, et al., Small Structures, 2021, 2(8): 2100014); a certain amount of SiO2 is added and mixed with LLZO powder, and then shaped and sintered to form LixSiOy crystal phase boundaries to eliminate lithium carbonate and reduce electronic conductivity (J.Zhang, R.Yu, J.Li, Energy & Environmental Materials, 2021, 0, 1-7). However, the above methods have limited effect on suppressing lithium dendrites because either the lithium carbonate is only covered but not eliminated, and electrons may still combine with lithium ions inside LLZO to form lithium dendrites after passing through the modified interface (Yongli Song, Luyi Yang, Wenguang Zhao, Advanced Energy Materials, 2019, 9(21): 900671); or the electronic conductivity of the modified solid electrolyte is still high. Summary of the Invention

[0005] One of the objectives of this invention is to provide a novel garnet-type solid electrolyte with microcrystalline glass grain boundaries, which has significantly reduced electronic conductivity at room temperature, improved lithium-ion conductivity, and good interfacial wettability with the lithium anode.

[0006] The second objective of this invention is to provide a novel garnet-type solid electrolyte with microcrystalline glass grain boundaries and its preparation method, which is simple and easy to adjust.

[0007] One of the solutions adopted to achieve the objective of this invention is: a novel garnet-type solid electrolyte with microcrystalline glass grain boundaries, comprising microcrystalline glass and a garnet-type cubic phase Li7La3Zr2O. 12 Solid electrolyte.

[0008] Preferably, the microcrystalline glass accounts for 0.1 wt.% to 10 wt.% of the garnet-type solid electrolyte.

[0009] Preferably, the microcrystalline glass is Li3BO3-Li2SO4-Li2CO3, Li3BO3-Li2CO3, or Li2SO4-Li2CO3.

[0010] One or more of Li2SO4-Li2CO3-LiBr, Li2O-B2O3, Li2O-P2O5, Li2O-SiO2, and Li2O-GeO2 in any proportion.

[0011] Preferably, the cubic phase Li7La3Zr2O12 The solid electrolyte is also doped with other elements, and the doping element is at least one of Ga, Al, Fe, Bi, Y, In, Si, Ge, Sn, V, W, Te, Nb, Ta, and Mg.

[0012] The second objective of this invention is achieved through a method for preparing a novel garnet-type solid electrolyte with microcrystalline glass grain boundaries, comprising the following preparation steps:

[0013] A. Preparation of cubic phase Li7La3Zr2O 12 Solid electrolytes:

[0014] A1. Take lithium source, lanthanum source and zirconium source according to stoichiometric ratio, ball mill and dry them, and calcine them at 600-1200℃ for 0.5-12 hours to obtain the initial phase. Ball mill and dry the obtained initial phase and then pre-calcine it into powder.

[0015] A2. Press the obtained pre-fired powder into sheets and sinter at 800-1300℃ for 0.5-24 hours to obtain LLZO ceramic sheets;

[0016] A3. After crushing the LLZO ceramic sheets, ball mill and dry them to obtain LLZO powder;

[0017] B. Preparation of glass solid electrolyte:

[0018] Weigh each raw material for preparing glass solid electrolyte according to the stoichiometric ratio, and calcine at 600-1000℃ for 0.1-6 hours to obtain glass solid electrolyte;

[0019] C. Preparation of garnet-type solid electrolytes with microcrystalline glass grain boundaries:

[0020] Take the LLZO powder prepared in step A3 and the glass powder prepared in step B in proportion, ball mill and dry them, and then press them into sheets; then sinter them at 900-1300℃ for 0.5-12 hours to allow the glass to react in situ with the lithium carbonate on the surface of the LLZO powder, and anneal them at 200-600℃ for 0.5-6 hours to allow the glass phase to precipitate microcrystals, thereby obtaining a garnet-type solid electrolyte with microcrystalline glass grain boundaries.

[0021] Preferably, in step A1, the lithium source is at least one of lithium oxide, lithium nitrate, or lithium hydroxide.

[0022] Preferably, in step A1, the lanthanum source is at least one of lanthanum carbonate, lanthanum nitrate, and lanthanum hydroxide.

[0023] Preferably, in step A1, the zirconium source is at least one of zirconium carbonate, zirconium nitrate, or zirconium hydroxide.

[0024] Preferably, step A1 further includes a dopant source, wherein the dopant source is at least one of an oxide, nitrate, or hydroxide of a dopant element.

[0025] Preferably, in step C, the glass powder accounts for 0.1 wt.% to 10 wt.% of the LLZO powder.

[0026] To eliminate lithium carbonate on the surface of LLZO and effectively suppress electron conduction, this invention involves adding a small amount of glass LLZO solid electrolyte powder, mixing, molding, and sintering. Using the harmful lithium carbonate formed on the surface of LLZO powder in an air atmosphere as raw material, a three-dimensional continuous microcrystalline glass grain boundary with high ionic conductivity, low electronic conductivity, and a wide voltage window is constructed through in-situ reaction. This not only eliminates the adverse effects of lithium carbonate but also promotes lithium ion generation and inhibits electron generation through the grain boundary, resulting in better suppression of lithium dendrites.

[0027] The present invention has the following advantages and beneficial effects:

[0028] (1) Compared with existing garnet-type solid electrolytes, the novel garnet-type solid electrolyte of the present invention with microcrystalline glass grain boundaries has both high room temperature ionic conductivity and low electronic conductivity.

[0029] (2) The novel garnet-type solid electrolyte with microcrystalline glass grain boundaries of the present invention has higher electrochemical stability and good wettability with lithium anode.

[0030] (3) The novel garnet-type solid electrolyte with microcrystalline glass boundaries of the present invention has three-dimensional continuity in its microcrystalline glass boundaries, which can better suppress electrons and promote ion transport, so as to achieve a better suppression effect on lithium dendrites.

[0031] (4) The preparation method of the present invention is simple and suitable for industrial production. Attached Figure Description

[0032] Figure 1 The novel garnet-type solid electrolyte material Li prepared for this invention 6.4 Ga 0.2 La3Zr2O 12 -1wt.% LCBSO physical sample image;

[0033] Figure 2 The novel garnet-type solid electrolyte material Li prepared for this invention 6.4 Ga 0.2 La3Zr2O 12 Comparison of wettability of -1wt.% LCBSO and conventional garnet-type solid electrolyte with molten lithium metal;

[0034] Figure 3 X-ray diffraction patterns of novel garnet-type solid electrolytes prepared in this invention with different contents of microcrystalline glass (1-10 wt.%);

[0035] Figure 4 The novel garnet-type solid electrolyte material Li prepared for this invention 6.4 Ga 0.2 La3Zr2O 12 SEM and EDS spectra of -5wt.% LCBSO;

[0036] Figure 5 The novel garnet-type solid electrolyte Li prepared by this invention under different sintering processes 6.4 Ga 0.2 La3Zr2O 12 -1 wt.% room temperature ionic conductivity and electronic conductivity of LCBSO;

[0037] Figure 6 The room temperature ionic conductivity and electronic conductivity of novel garnet-type electrolytes with different contents of microcrystalline glass prepared in this invention are shown.

[0038] Figure 7 This is a local laser confocal Raman spectrum analysis of the novel garnet-type solid electrolyte material prepared in this invention. Detailed Implementation

[0039] To better understand the present invention, the following embodiments are further illustrations of the present invention, but the content of the present invention is not limited to the following embodiments.

[0040] Example 1:

[0041] According to the stoichiometric ratio of LLZO and with a 10% lithium source excess, lithium carbonate (Li₂CO₃), lanthanum oxide (La₂O₃), zirconium oxide (ZrO₂), and gallium oxide (Ga₂O₃) powders were mixed evenly to obtain a mixed powder. Approximately 10g of the mixed powder was weighed and placed in a ball mill jar. 30g (300% by mass) of isopropanol and an appropriate amount of zirconium oxide balls were added, and the mixture was ball-milled at 300 rpm for 12 hours. After ball milling, the mixture was placed in a drying oven and dried at 80℃ for 6 hours. Then, it was pre-calcined at 900℃ for 6 hours, followed by ball milling and drying. 3.0g of the dried mixture was weighed and placed in a mortar, and 0.3g (10%) of a 10% PVA aqueous solution was added. The mixture was ground for 15 minutes, and then placed in a steel mold and pressed at 300MPa for 5 minutes to obtain a green body. The billet was heated to 1200℃ at a heating rate of 5℃ / min, held at that temperature for 9 hours, and then cooled in the furnace to obtain the garnet-type solid electrolyte Li. 6.4 Ga 0.2 La3Zr2O 12Solid electrolyte flakes were crushed in an agate mortar and then ball-milled and dried to obtain LLZO powder. Lithium borate (Li3BO3) and lithium sulfate (Li2SO4) were mixed uniformly at a molar ratio of 9:1 and calcined at 800℃ for 1 hour to obtain Li3BO3-Li2SO4 powder. The LLZO powder was then mixed with the Li3BO3-Li2SO4 powder, with microcrystalline glass comprising 1 wt.% of the LLZO powder, and pressed at 250 MPa to form a green body. The green body was heated to 1200℃ at a heating rate of 5℃ / min, causing the Li3BO3-Li2SO4 to react in situ with lithium carbonate on the surface of the LLZO powder to form LCBSO glass. This was held at this temperature for 2 hours and then annealed at 300℃ for 4 hours to precipitate microcrystals of the glass phase, resulting in a garnet-type solid electrolyte with microcrystalline glass grain boundaries.

[0042] The novel garnet-type solid electrolyte Li prepared in Example 1 6.4 Ga 0.2 La3Zr2O 12 The physical image and X-ray diffraction pattern of the -1wt.% LCBSO sample are shown below. Figure 1 and Figure 3 The 1wt.% labeling curve is shown in the figure. From... Figure 1 It can be observed that the electrolyte surface is smooth and dense, and its color is brown. From Figure 3 As can be seen, the X-ray diffraction peaks of the novel garnet-type solid electrolyte match well with the PDF card (45-0109) of cubic LLZO, indicating that LCBSO does not affect the phase of LLZO and it remains cubic LLZO. The novel garnet-type solid electrolyte prepared in Example 1 was subjected to AC impedance and DC polarization tests using an electrochemical workstation. The test results are as follows: Figure 5 (a) and Figure 5 (b) shows the identification curves of LLZO-1wt.%LCBSO at 1200℃ for 9 hours and 11200℃ for 2 hours. Calculations based on the test results indicate that the ionic conductivity of the novel garnet-type solid electrolyte sample prepared in Example 1 can reach 1.5 × 10⁻⁶ at room temperature. -3 The S / cm value is high, while the electronic conductivity is only 1.0 × 10⁻⁶. -9 S / cm. The novel garnet-type solid electrolyte prepared in Example 1 has a contact angle of only 75° with molten lithium metal, while the traditional garnet-type solid electrolyte has a contact angle of 143° with molten lithium metal (e.g., S / cm). Figure 2 As shown in the figure, the novel garnet-type solid electrolyte prepared by the present invention has significantly improved wettability with lithium metal compared with traditional garnet solid electrolytes.

[0043] Example 2:

[0044] According to the stoichiometric ratio of LLZO and with a 10% lithium source excess, lithium carbonate (Li₂CO₃), lanthanum oxide (La₂O₃), zirconium oxide (ZrO₂), and gallium oxide (Ga₂O₃) powders were mixed evenly to obtain a mixed powder. Approximately 10g of the mixed powder was weighed and placed in a ball mill jar. 30g (300% by mass) of isopropanol and an appropriate amount of zirconium oxide balls were added, and the mixture was ball-milled at 300 rpm for 12 hours. After ball milling, the mixture was placed in a drying oven and dried at 80℃ for 6 hours. Then, it was pre-calcined at 900℃ for 6 hours, followed by ball milling and drying. 3.0g of the dried mixture was weighed and placed in a mortar, and 0.3g (10%) of a 10% PVA aqueous solution was added. The mixture was ground for 15 minutes, and then placed in a steel mold and pressed at 300MPa for 5 minutes to obtain a green body. The billet was heated to 1200℃ at a heating rate of 5℃ / min, held at that temperature for 9 hours, and then cooled in the furnace to obtain the garnet-type solid electrolyte Li. 6.4 Ga 0.2 La3Zr2O 12 Solid electrolyte flakes were crushed in an agate mortar and then ball-milled and dried to obtain LLZO powder. Lithium borate (Li3BO3) and lithium sulfate (Li2SO4) were mixed uniformly at a molar ratio of 9:1 and calcined at 800℃ for 1 hour to obtain Li3BO3-Li2SO4 powder. The LLZO powder was then mixed with the Li3BO3-Li2SO4 powder, with microcrystalline glass comprising 0.1 wt.% of the LLZO powder, and pressed at 250 MPa to form a green body. The green body was heated to 1200℃ at a heating rate of 5℃ / min, causing the Li3BO3-Li2SO4 to react in situ with lithium carbonate on the surface of the LLZO powder to form LCBSO glass. This was held at this temperature for 2 hours and then annealed at 300℃ for 4 hours to precipitate microcrystals of the glass phase, resulting in a garnet-type solid electrolyte with microcrystalline glass grain boundaries.

[0045] The novel garnet-type solid electrolyte Li prepared in Example 2 6.4 Ga 0.2 La3Zr2O 12 The X-ray diffraction pattern of the 0.1 wt.% LCBSO sample is shown below. Figure 3 As shown in the 0.1 wt.% identification curve, a comparison with the standard PDF card 45-0109 reveals that this sample is a cubic phase LLZO.

[0046] Example 3:

[0047] According to the stoichiometric ratio of LLZO and with a 10% lithium source excess, lithium carbonate (Li₂CO₃), lanthanum oxide (La₂O₃), zirconium oxide (ZrO₂), and gallium oxide (Ga₂O₃) powders were mixed evenly to obtain a mixed powder. Approximately 10g of the mixed powder was weighed and placed in a ball mill jar. 30g (300% by mass) of isopropanol and an appropriate amount of zirconium oxide balls were added, and the mixture was ball-milled at 300 rpm for 12 hours. After ball milling, the mixture was placed in a drying oven and dried at 80℃ for 6 hours. Then, it was pre-calcined at 900℃ for 6 hours, followed by ball milling and drying. 3.0g of the dried mixture was weighed and placed in a mortar, and 0.3g (10%) of a 10% PVA aqueous solution was added. The mixture was ground for 15 minutes, and then placed in a steel mold and pressed at 300MPa for 5 minutes to obtain a green body. The billet was heated to 1200℃ at a heating rate of 5℃ / min, held at that temperature for 9 hours, and then cooled in the furnace to obtain the garnet-type solid electrolyte Li. 6.4 Ga 0.2 La3Zr2O 12 Solid electrolyte flakes were crushed in an agate mortar and then ball-milled and dried to obtain LLZO powder. Lithium borate (Li3BO3) and lithium sulfate (Li2SO4) were mixed uniformly at a molar ratio of 9:1 and calcined at 800℃ for 1 hour to obtain Li3BO3-Li2SO4 powder. The LLZO powder was then mixed with the Li3BO3-Li2SO4 powder, with microcrystalline glass comprising 5 wt.% of the LLZO powder, and pressed at 250 MPa to form a green body. The green body was heated to 1200℃ at a heating rate of 5℃ / min, causing the Li3BO3-Li2SO4 to react in situ with lithium carbonate on the surface of the LLZO powder to form LCBSO glass. This was held at this temperature for 2 hours and then annealed at 300℃ for 4 hours to precipitate microcrystals of the glass phase, resulting in a garnet-type solid electrolyte with microcrystalline glass grain boundaries.

[0048] The X-ray diffraction pattern of the garnet-type solid electrolyte sample prepared in Example 3 is shown below. Figure 3 The 5wt.% identification curve shows that, compared with the standard PDF card 45-0109, this sample is a cubic LLZO phase. The SEM and EDS images of the garnet-type solid electrolyte sample prepared in Example 3 are shown below. Figure 4 As shown. From Figure 4 As can be seen, the fracture mode of the sintered solid electrolyte is intergranular fracture, with a dense microstructure and uniform distribution of La, Zr, S, and B elements. The novel garnet-type solid electrolyte prepared in Example 3 was subjected to AC impedance and DC polarization tests using an electrochemical workstation. The test results are as follows: Figure 6 The 5wt.% identification curves are shown in (a) and (b). Based on the test results, the ionic conductivity at room temperature of the novel garnet-type solid electrolyte sample prepared in Example 3 is 1.03 × 10⁻⁶.-4 S / cm, electronic conductivity 8.34×10 -10 S / cm.

[0049] Example 4:

[0050] According to the stoichiometric ratio of LLZO and with a 10% lithium source excess, lithium carbonate (Li₂CO₃), lanthanum oxide (La₂O₃), zirconium oxide (ZrO₂), and gallium oxide (Ga₂O₃) powders were mixed evenly to obtain a mixed powder. Approximately 10g of the mixed powder was weighed and placed in a ball mill jar. 30g (300% by mass) of isopropanol and an appropriate amount of zirconium oxide balls were added, and the mixture was ball-milled at 300 rpm for 12 hours. After ball milling, the mixture was placed in a drying oven and dried at 80℃ for 6 hours. Then, it was pre-calcined at 900℃ for 6 hours, followed by ball milling and drying. 3.0g of the dried mixture was weighed and placed in a mortar, and 0.3g (10%) of a 10% PVA aqueous solution was added. The mixture was ground for 15 minutes, and then placed in a steel mold and pressed at 300MPa for 5 minutes to obtain a green body. The billet was heated to 1200℃ at a heating rate of 5℃ / min, held at that temperature for 9 hours, and then cooled in the furnace to obtain the garnet-type solid electrolyte Li. 6.4 Ga 0.2 La3Zr2O 12 Solid electrolyte flakes were crushed in an agate mortar and then ball-milled and dried to obtain LLZO powder. Lithium borate (Li3BO3) and lithium sulfate (Li2SO4) were mixed uniformly at a molar ratio of 9:1 and calcined at 800℃ for 1 hour to obtain Li3BO3-Li2SO4 powder. The LLZO powder was then mixed with the Li3BO3-Li2SO4 powder, with microcrystalline glass comprising 10 wt.% of the LLZO powder, and pressed at 250 MPa to form a green body. The green body was heated to 1200℃ at a heating rate of 5℃ / min and held for 2 hours to allow the Li3BO3-Li2SO4 to react in situ with lithium carbonate on the surface of the LLZO powder to form LCBSO glass. The green body was then annealed at 300℃ for 4 hours to precipitate microcrystals of the glass phase, resulting in a garnet-type solid electrolyte with microcrystalline glass grain boundaries.

[0051] The novel garnet-type solid electrolyte Li prepared in Example 4 6.4 Ga 0.2 La3Zr2O 12 The X-ray diffraction pattern of the -10wt.%LCBSO sample is shown below. Figure 3The 10 wt.% identification curve is shown in the figure. Besides the characteristic peaks of cubic LLZO, this sample also showed diffuse peaks and peak broadening, as well as diffraction peaks from other crystals, indicating the precipitation of microcrystalline phases at the LCBSO glass grain boundaries after low-temperature annealing. The novel garnet-type solid electrolyte prepared in Example 4 was subjected to AC impedance and DC polarization tests using an electrochemical workstation. The test results are shown in the figure. Figure 6 The 10wt.% identification curves are shown in (a) and (b). Calculations based on the test results show that the novel garnet-type solid electrolyte sample prepared in Example 4 exhibits a maximum ionic conductivity of 5.75 × 10⁻⁶ at room temperature. -5 The S / cm value is high, while the electronic conductivity is only 8.22 × 10⁻⁶. -10 S / cm.

[0052] Example 5:

[0053] According to the stoichiometric ratio of LLZO and with a 10% lithium source excess, lithium carbonate (Li₂CO₃), lanthanum oxide (La₂O₃), zirconium oxide (ZrO₂), and gallium oxide (Ga₂O₃) powders were mixed evenly to obtain a mixed powder. Approximately 10g of the mixed powder was weighed and placed in a ball mill jar. 30g (300% by mass) of isopropanol and an appropriate amount of zirconium oxide balls were added, and the mixture was ball-milled at 300 rpm for 12 hours. After ball milling, the mixture was placed in a drying oven and dried at 80℃ for 6 hours. Then, it was pre-calcined at 900℃ for 6 hours, followed by ball milling and drying. 3.0g of the dried mixture was weighed and placed in a mortar, and 0.3g (10%) of a 10% PVA aqueous solution was added. The mixture was ground for 15 minutes, and then placed in a steel mold and pressed at 300MPa for 5 minutes to obtain a green body. The billet was heated to 800℃ at a heating rate of 5℃ / min, held at that temperature for 24 hours, and then cooled in the furnace to obtain the garnet-type solid electrolyte Li. 6.4 Ga 0.2 La3Zr2O 12 Solid electrolyte flakes were crushed in an agate mortar and then ball-milled and dried to obtain LLZO powder. Lithium borate (Li3BO3) and lithium sulfate (Li2SO4) were mixed uniformly at a molar ratio of 9:1 and calcined at 800℃ for 1 hour to obtain Li3BO3-Li2SO4 powder. The LLZO powder was then mixed with the Li3BO3-Li2SO4 powder, with microcrystalline glass comprising 1 wt.% of the LLZO powder, and pressed at 250 MPa to form a green body. The green body was heated to 900℃ at a heating rate of 5℃ / min and held for 12 hours to allow the Li3BO3-Li2SO4 to react in situ with lithium carbonate on the surface of the LLZO powder to form LCBSO glass. The green body was then annealed at 300℃ for 4 hours to precipitate microcrystals of the glass phase, resulting in a garnet-type solid electrolyte with microcrystalline glass grain boundaries.

[0054] The novel garnet-type solid electrolyte prepared in Example 5 was subjected to AC impedance and DC polarization tests using an electrochemical workstation. The test results are as follows: Figure 5 The marking curve is shown in the figure (LLZO-1wt.% LCBSO 800℃ 24h 1900℃ 12h). Based on the test results, the ionic conductivity at room temperature of the novel garnet-type solid electrolyte sample prepared in Example 5 is 1.67 × 10⁻⁶. -6 S / cm, electronic conductivity 2.56×10 -8 S / cm.

[0055] Example 6:

[0056] According to the stoichiometric ratio of LLZO and with a 10% lithium source excess, lithium carbonate (Li₂CO₃), lanthanum oxide (La₂O₃), zirconium oxide (ZrO₂), and gallium oxide (Ga₂O₃) powders were mixed evenly to obtain a mixed powder. Approximately 10g of the mixed powder was weighed and placed in a ball mill jar. 30g (300% by mass) of isopropanol and an appropriate amount of zirconium oxide balls were added, and the mixture was ball-milled at 300 rpm for 12 hours. After ball milling, the mixture was placed in a drying oven and dried at 80℃ for 6 hours. Then, it was pre-calcined at 900℃ for 6 hours, followed by ball milling and drying. 3.0g of the dried mixture was weighed and placed in a mortar, and 0.3g (10%) of a 10% PVA aqueous solution was added. The mixture was ground for 15 minutes, and then placed in a steel mold and pressed at 300MPa for 5 minutes to obtain a green body. The billet was heated to 1000℃ at a heating rate of 5℃ / min, held at that temperature for 16 hours, and then cooled in the furnace to obtain the garnet-type solid electrolyte Li. 6.4 Ga 0.2 La3Zr2O 12 Solid electrolyte flakes were crushed in an agate mortar and then ball-milled and dried to obtain LLZO powder. Lithium borate (Li3BO3) and lithium sulfate (Li2SO4) were mixed uniformly at a molar ratio of 9:1 and calcined at 800℃ for 1 hour to obtain Li3BO3-Li2SO4 powder. The LLZO powder was then mixed with the Li3BO3-Li2SO4 powder, with microcrystalline glass comprising 1 wt.% of the LLZO powder, and pressed at 250 MPa to form a green body. The green body was heated to 1100℃ at a heating rate of 5℃ / min and held for 6 hours to allow the Li3BO3-Li2SO4 to react in situ with lithium carbonate on the surface of the LLZO powder to form LCBSO glass. The green body was then annealed at 300℃ for 4 hours to precipitate microcrystals of the glass phase, resulting in a garnet-type solid electrolyte with microcrystalline glass grain boundaries.

[0057] The novel garnet-type solid electrolyte prepared in Example 6 was subjected to AC impedance and DC polarization tests using an electrochemical workstation. The test results are as follows: Figure 5The characteristic curves are shown in the figure for 1 wt.% LCBSO at 1000℃ for 16 h and 1100℃ for 6 h. Based on the test results, the ionic conductivity of the novel garnet-type solid electrolyte sample prepared in Example 6 at room temperature is 1.25 × 10⁻⁶. -5 S / cm, electronic conductivity 2.22×10 -8 S / cm.

[0058] Example 7:

[0059] According to the stoichiometric ratio of LLZO and with a 10% lithium source excess, lithium carbonate (Li₂CO₃), lanthanum oxide (La₂O₃), zirconium oxide (ZrO₂), and gallium oxide (Ga₂O₃) powders were mixed evenly to obtain a mixed powder. Approximately 10g of the mixed powder was weighed and placed in a ball mill jar. 30g (300% by mass) of isopropanol and an appropriate amount of zirconium oxide balls were added, and the mixture was ball-milled at 300 rpm for 12 hours. After ball milling, the mixture was placed in a drying oven and dried at 80℃ for 6 hours. Then, it was pre-calcined at 900℃ for 6 hours, followed by ball milling and drying. 3.0g of the dried mixture was weighed and placed in a mortar, and 0.3g (10%) of a 10% PVA aqueous solution was added. The mixture was ground for 15 minutes, and then placed in a steel mold and pressed at 300MPa for 5 minutes to obtain a green body. The billet was heated to 1300℃ at a heating rate of 5℃ / min, held at that temperature for 0.5 hours, and then cooled in the furnace to obtain the garnet-type solid electrolyte Li. 6.4 Ga 0.2 La3Zr2O 12 Solid electrolyte flakes were crushed in an agate mortar and then ball-milled and dried to obtain LLZO powder. Lithium borate (Li3BO3) and lithium sulfate (Li2SO4) were mixed uniformly at a molar ratio of 9:1 and calcined at 800℃ for 1 hour to obtain Li3BO3-Li2SO4 powder. The LLZO powder was then mixed with the Li3BO3-Li2SO4 powder, with microcrystalline glass comprising 1 wt.% of the LLZO powder, and pressed at 250 MPa to form a green body. The green body was heated to 1300℃ at a heating rate of 5℃ / min and held for 0.5 hours to allow the Li3BO3-Li2SO4 to react in situ with lithium carbonate on the surface of the LLZO powder to form LCBSO glass. The mixture was then annealed at 300℃ for 4 hours to precipitate microcrystals of the glass phase, resulting in a garnet-type solid electrolyte with microcrystalline glass grain boundaries.

[0060] The novel garnet-type solid electrolyte prepared in Example 7 was subjected to AC impedance and DC polarization tests using an electrochemical workstation. The test results are as follows: Figure 5The indicative curves are shown for 1 wt.% LCBSO at 1300℃ for 0.5 h and 1 wt.% LCBSO at 1300℃ for 0.5 h. Based on the test results, the ionic conductivity at room temperature of the novel garnet-type solid electrolyte sample prepared in Example 7 is 8.67 × 10⁻⁶. -4 S / cm, electronic conductivity 1.78×10 -9 S / cm.

[0061] Example 8:

[0062] According to the stoichiometric ratio of LLZO and with a 10% lithium source excess, lithium carbonate (Li₂CO₃), lanthanum oxide (La₂O₃), zirconium oxide (ZrO₂), and gallium oxide (Ga₂O₃) powders were mixed evenly to obtain a mixed powder. Approximately 10g of the mixed powder was weighed and placed in a ball mill jar. 30g (300% by mass) of isopropanol and an appropriate amount of zirconium oxide balls were added, and the mixture was ball-milled at 300 rpm for 12 hours. After ball milling, the mixture was placed in a drying oven and dried at 80℃ for 6 hours. Then, it was pre-calcined at 900℃ for 6 hours, followed by ball milling and drying. 3.0g of the dried mixture was weighed and placed in a mortar, and 0.3g (10%) of a 10% PVA aqueous solution was added. The mixture was ground for 15 minutes, and then placed in a steel mold and pressed at 300MPa for 5 minutes to obtain a green body. The billet was heated to 1200℃ at a heating rate of 5℃ / min, held at that temperature for 9 hours, and then cooled in the furnace to obtain the garnet-type solid electrolyte Li. 6.4 Ga 0.2 La3Zr2O 12 Solid electrolyte flakes were crushed in an agate mortar and then ball-milled and dried to obtain LLZO powder. Lithium borate (Li3BO3) and lithium sulfate (Li2SO4) were mixed uniformly at a molar ratio of 9:1 and calcined at 800℃ for 1 hour to obtain Li3BO3-Li2SO4 powder. The LLZO powder was then mixed with the Li3BO3-Li2SO4 powder, with microcrystalline glass comprising 1 wt.% of the LLZO powder, and pressed at 250 MPa to form a green body. The green body was heated to 1200℃ at a heating rate of 5℃ / min and held for 2 hours to allow the Li3BO3-Li2SO4 to react in situ with lithium carbonate on the surface of the LLZO powder to form LCBSO glass. The green body was then annealed at 600℃ for 0.5 hours to precipitate microcrystals of the glass phase, resulting in a garnet-type solid electrolyte with microcrystalline glass grain boundaries.

[0063] The laser confocal Raman spectrum analysis of the grain boundaries of the novel garnet-type solid electrolyte sample prepared in Example 8 is shown below. Figure 7 As shown in (a). From the figure, we can see that the stretching vibration peaks in the low and mid-frequency regions correspond to cubic LLZO, and the stretching vibration peak in the high-frequency region is at 950 cm⁻¹. -1 (BO3 3-), 1010cm -1 (SO4 2- ), 1090cm -1 (CO3 2- The corresponding microcrystalline glass LCBSO indicates the successful construction of microcrystalline glass grain boundaries in garnet-type solid electrolytes.

[0064] Example 9:

[0065] According to the stoichiometric ratio of LLZO and with a 10% lithium source excess, lithium carbonate (Li₂CO₃), lanthanum oxide (La₂O₃), zirconium oxide (ZrO₂), and gallium oxide (Ga₂O₃) powders were mixed evenly to obtain a mixed powder. Approximately 10g of the mixed powder was weighed and placed in a ball mill jar. 30g (300% by mass) of isopropanol and an appropriate amount of zirconium oxide balls were added, and the mixture was ball-milled at 300 rpm for 12 hours. After ball milling, the mixture was placed in a drying oven and dried at 80℃ for 6 hours. Then, it was pre-calcined at 900℃ for 6 hours, followed by ball milling and drying. 3.0g of the dried mixture was weighed and placed in a mortar, and 0.3g (10%) of a 10% PVA aqueous solution was added. The mixture was ground for 15 minutes, and then placed in a steel mold and pressed at 300MPa for 5 minutes to obtain a green body. The billet was heated to 1200℃ at a heating rate of 5℃ / min, held at that temperature for 9 hours, and then cooled in the furnace to obtain the garnet-type solid electrolyte Li. 6.4 Ga 0.2 La3Zr2O 12 Solid electrolyte flakes were crushed in an agate mortar and then ball-milled and dried to obtain LLZO powder. Lithium borate (Li3BO3) and lithium sulfate (Li2SO4) were mixed uniformly at a molar ratio of 9:1 and calcined at 800℃ for 1 hour to obtain Li3BO3-Li2SO4 powder. The LLZO powder was then mixed with the Li3BO3-Li2SO4 powder, with microcrystalline glass comprising 1 wt.% of the LLZO powder, and pressed at 250 MPa to form a green body. The green body was heated to 1200℃ at a heating rate of 5℃ / min and held for 2 hours to allow the Li3BO3-Li2SO4 to react in situ with lithium carbonate on the surface of the LLZO powder to form LCBSO glass. The green body was then annealed at 300℃ for 4 hours to precipitate microcrystals of the glass phase, resulting in a garnet-type solid electrolyte with microcrystalline glass grain boundaries.

[0066] Example 10:

[0067] According to the stoichiometric ratio of LLZO and with a 10% excess lithium source, lithium carbonate (Li₂CO₃), lanthanum oxide (La₂O₃), zirconium oxide (ZrO₂), and alumina (Al₂O₃) powders were mixed evenly to obtain a mixed powder. Approximately 10g of the mixed powder was weighed and placed in a ball mill jar. 30g (300% by mass) of isopropanol and an appropriate amount of zirconium oxide balls were added, and the mixture was ball-milled at 300 rpm for 12 hours. After ball milling, the mixture was placed in a drying oven and dried at 80℃ for 6 hours. Then, it was pre-calcined at 900℃ for 6 hours, followed by ball milling and drying. 3.0g of the dried mixture was weighed and placed in a mortar, and 0.3g (10%) of a 10% PVA aqueous solution was added. The mixture was ground for 15 minutes, and then placed in a steel mold and pressed at 300MPa for 5 minutes to obtain a green body. The billet was heated to 1150℃ at a heating rate of 5℃ / min, held at that temperature for 8 hours, and then cooled in the furnace to obtain the garnet-type solid electrolyte Li. 6.4 Ga 0.2 La3Zr2O 12 Solid electrolyte flakes were crushed in an agate mortar and then ball-milled and dried to obtain LLZO powder. Lithium borate (Li3BO3) and lithium sulfate (Li2SO4) were mixed uniformly at a molar ratio of 9:1 and calcined at 800℃ for 1 hour to obtain Li3BO3-Li2SO4 powder. The LLZO powder was then mixed with the Li3BO3-Li2SO4 powder, with microcrystalline glass comprising 1 wt.% of the LLZO powder, and pressed at 250 MPa to form a green body. The green body was heated to 1200℃ at a heating rate of 5℃ / min and held for 2 hours to allow the Li3BO3-Li2SO4 to react in situ with lithium carbonate on the surface of the LLZO powder to form LCBSO glass. The green body was then annealed at 300℃ for 4 hours to precipitate microcrystals of the glass phase, resulting in a garnet-type solid electrolyte with microcrystalline glass grain boundaries.

[0068] The novel garnet-type solid electrolyte prepared in Example 10 was subjected to AC impedance and DC polarization tests using an electrochemical workstation. The test results are as follows: Figure 6 The Al-LLZO identification curve is shown. Based on the test results, the ionic conductivity of the novel garnet-type solid electrolyte sample prepared in Example 6 at room temperature is 2.87 × 10⁻⁶. -4 S / cm, electronic conductivity 8.75×10 -10 S / cm.

[0069] Example 11:

[0070] According to the stoichiometric ratio of LLZO and with a 10% lithium source excess, lithium carbonate (Li₂CO₃), lanthanum oxide (La₂O₃), zirconium oxide (ZrO₂), and gallium oxide (Ga₂O₃) powders were mixed evenly to obtain a mixed powder. Approximately 10g of the mixed powder was weighed and placed in a ball mill jar. 30g (300% by mass) of isopropanol and an appropriate amount of zirconium oxide balls were added, and the mixture was ball-milled at 300 rpm for 12 hours. After ball milling, the mixture was placed in a drying oven and dried at 80℃ for 6 hours. Then, it was pre-calcined at 900℃ for 6 hours, followed by ball milling and drying. 3.0g of the dried mixture was weighed and placed in a mortar, and 0.3g (10%) of a 10% PVA aqueous solution was added. The mixture was ground for 15 minutes, and then placed in a steel mold and pressed at 300MPa for 5 minutes to obtain a green body. The billet was heated to 1200℃ at a heating rate of 5℃ / min, held at that temperature for 9 hours, and then cooled in the furnace to obtain the garnet-type solid electrolyte Li. 6.4 Ga 0.2 La3Zr2O 12 The solid electrolyte flakes were crushed in an agate mortar and then ball-milled and dried to obtain LLZO powder. The LLZO powder was then mixed with Li₂SO₄ powder (1 wt.% of the LLZO powder) and pressed at 250 MPa to form a green body. The green body was heated to 1200 °C at a heating rate of 5 °C / min, causing the Li₂SO₄ to react in situ with lithium carbonate on the surface of the LLZO powder to form Li₂SO₄-Li₂CO₃. The mixture was held at this temperature for 2 hours and then annealed at 300 °C for 4 hours to precipitate microcrystals of the glassy phase, resulting in a garnet-type solid electrolyte with microcrystalline glass boundaries.

[0071] The laser confocal Raman spectrum analysis of the grain boundaries of the novel garnet-type solid electrolyte sample prepared in Example 11 is shown below. Figure 7 As shown in (b). From the figure, we can see that the stretching vibration peaks in the low and mid-frequency regions correspond to cubic LLZO, and the stretching vibration peak in the high-frequency region is 10¹⁰ cm⁻¹. -1 (SO4 2- ), 1090cm -1 (CO3 2- The corresponding microcrystalline glass is Li2SO4-Li2CO3, which indicates the successful construction of microcrystalline glass grain boundaries in garnet-type solid electrolytes.

[0072] The above description is merely a preferred embodiment of the present invention, and should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing a new type of garnet solid electrolyte having a glass-ceramic grain boundary, characterized by: The preparation steps include: A. Preparation of cubic phase Li7La3Zr2O 12 Solid electrolyte: A1, according to the stoichiometric ratio of LLZO and 10% excess of lithium source, lithium carbonate, lanthanum source and zirconium source are ball milled and dried, and then calcined at 600-1200℃ for 0.5-12 hours to obtain a primary phase, and the obtained primary phase is ball milled and dried to obtain a pre-fired powder; A2, the pre-fired powder is pressed into a sheet and sintered at 800-1300℃ for 0.5-24 hours to obtain an LLZO ceramic sheet; A3, the LLZO ceramic sheet is crushed, ball milled and dried to obtain an LLZO powder; B, preparation of glass solid electrolyte: According to the metering ratio, each raw material for preparing the glass solid electrolyte is weighed, and after calcination at 600-1000℃ for 0.1-6 hours, the glass solid electrolyte is obtained; C, preparation of garnet-type solid electrolyte with glass-ceramic grain boundary: The LLZO powder prepared in step A3 and the glass powder prepared in step B are taken in proportion, ball milled and dried, and then pressed into a sheet; then sintered at 900-1300℃ for 0.5-12 hours to make the glass react with the surface lithium carbonate of the LLZO powder in situ, and annealed at 200-600℃ for 0.5-6 hours to make the glass phase precipitate microcrystals, thereby obtaining a garnet-type solid electrolyte with glass-ceramic grain boundary; The new garnet-type solid electrolyte with glass-ceramic grain boundaries includes glass-ceramics and a garnet-type cubic phase Li7La3Zr2O 12 Solid electrolyte; The glass-ceramic accounts for 0.1 wt.%-10 wt.% of the garnet-type solid electrolyte.

2. The preparation method of the new garnet-type solid electrolyte having a glass-ceramic grain boundary according to claim 1, characterized by: The glass-ceramic is one or any proportion of multiple of Li3BO3-Li2SO4-Li2CO3, Li3BO3-Li2CO3, Li2SO4-Li2CO3, Li2SO4-Li2CO3-LiBr, Li2O-B2O3, Li2O-P2O5, Li2O-SiO2, Li2O-GeO2.

3. The preparation method of a new garnet-type solid electrolyte having a glass-ceramic grain boundary according to claim 1, characterized by: The cubic phase Li7La3Zr2O 12 The solid electrolyte is further doped with at least one of Ga, Al, Fe, Bi, Y, In, Si, Ge, Sn, V, W, Te, Nb, Ta, Mg.

4. The preparation method of a new garnet-type solid electrolyte having a glass-ceramic grain boundary according to claim 1, characterized by: In step A1, the lanthanum source is at least one of lanthanum carbonate, lanthanum nitrate and lanthanum hydroxide.

5. The method of producing a new garnet-type solid electrolyte having a glass-ceramic grain boundary according to claim 1, characterized by: In step A1, the zirconium source is at least one of zirconium carbonate, zirconium nitrate or zirconium hydroxide.

6. The method of producing a new garnet-type solid electrolyte having a glass-ceramic grain boundary according to claim 1, characterized by: In step A1, the doping element source is at least one of an oxide, a nitrate or a hydroxide of the doping element.

7. The preparation method of a new garnet-type solid electrolyte having a glass-ceramic grain boundary according to claim 1, characterized by: In step C, the glass powder accounts for 0.1 wt.%-10 wt.% of the LLZO powder.

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