Preparation method of lithium lanthanum zirconium oxide solid electrolyte doped with aluminum element

Abstract

The invention relates to a preparation method of an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte, and belongs to the technical field of solid electrolyte materials. Adding lithium carbonate, lanthanum oxide, zirconium oxide, aluminum nitrate and absolute ethyl alcohol into a ball milling tank for ball milling, drying, adding the modified aluminum ion chelating agent, mixing, grinding, sieving, putting into an aluminum oxide crucible, and pre-sintering to obtain an LLZO precursor; grinding and sieving the LLZO precursor, adding a polyvinyl alcohol solution, mixing, and pressing into a wafer; and placing the wafer in an alumina crucible, and carrying out high-temperature sintering to obtain the lithium lanthanum zirconium oxide solid electrolyte doped with the aluminum element. The modified aluminum ion chelating agent is prepared from (11-mercaptoundecyl)-trimethyl ammonium bromide, methylbenzene, biphenyl-4, 4 '-dithiol, triethylamine, lanthanum nitrate and stannous octoate; the lithium lanthanum zirconium oxide solid electrolyte prepared by the invention has relatively high room-temperature ionic conductivity and excellent chemical stability and interface stability.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of solid electrolyte materials, in particular to a preparation method of lithium lanthanum zirconium oxide solid electrolyte doped with aluminum elements. BACKGROUND

[0002] Solid electrolyte is the core material of the next generation of high safety lithium ion batteries. Compared with the traditional liquid electrolyte, the solid electrolyte has the advantages of no leakage, high pressure resistance and good thermal stability, and can fundamentally solve the safety hazards of lithium ion batteries. Lithium lanthanum zirconium oxide has high ionic conductivity, a wide electrochemical window and excellent chemical stability, and has become one of the most promising solid electrolyte materials.

[0003] Chinese patent CN119920954A: applicable to the field of solid electrolyte and solid lithium ion battery, provides a preparation method of cubic phase lithium lanthanum zirconium oxide solid electrolyte, which comprises the control of phase, grain size and element doping, including the following steps: first, synthesizing metal oxide precursor by co-precipitation method; the metal oxide precursor is surface modified by rotary evaporation process, and drying treatment is simultaneously completed; the modified precursor powder is calcined under certain temperature and atmosphere conditions to obtain the corresponding metal oxide; lithium source and dopant are added to the metal oxide, and sintering is carried out under certain temperature, atmosphere and pressure environment to obtain LLZO solid electrolyte material with cubic phase structure.

[0004] Chinese patent CN120057983B: provides an Al-Nb co-doped lithium lanthanum zirconium oxide and a preparation method thereof and a lithium ion battery. The preparation method comprises the following steps: first mixing lanthanum source, zirconium source, niobium source and aluminum source according to the stoichiometric ratio, pre-sintering to obtain pre-sintered material; the pre-sintered material and excess lithium source are secondly mixed and solid-phase reacted to prepare the Al-Nb co-doped lithium lanthanum zirconium oxide.

[0005] The existing preparation methods mainly include solid phase method, sol-gel method and co-precipitation method. Although the sol-gel method and the co-precipitation method can realize uniform mixing of raw materials, there are problems of complex preparation process, high cost and easy introduction of impurities; the solid phase method has defects of uneven mixing of raw materials, too high pre-sintering temperature and too long sintering time, resulting in low product purity and low ionic conductivity. SUMMARY

[0006] In order to solve the above problems, the application provides a preparation method of lithium lanthanum zirconium oxide solid electrolyte doped with aluminum elements, and the operation steps are as follows: S1 ball milling mixing: 20-30 parts of lithium carbonate, 48-58 parts of lanthanum oxide, 20-28 parts of zirconium oxide and 2-5 parts of aluminum nitrate are added into a ball mill tank, 100-140 parts of anhydrous ethanol are added as a dispersant, and a mixed slurry is obtained by ball milling; S2 drying and pre-sintering: the mixed slurry is dried at 60-80℃ under vacuum for 4-6h, 0.5-0.8 parts of modified aluminum ion chelating agent is added, mixed and ground, and then sieved through a 100-200 mesh sieve, and then placed in an alumina crucible and pre-sintered in an air atmosphere to obtain an LLZO precursor; S3 tabletting and forming: the LLZO precursor is ground through a 200-300 mesh sieve, 1-3 parts of polyvinyl alcohol solution is added as a binder, and then mixed uniformly and pressed into a round sheet under a pressure of 10-20 MPa; S4 high-temperature sintering: the round sheet is placed in an alumina crucible and high-temperature sintered in an air atmosphere; and then cooled to room temperature to obtain an aluminum-doped lithium lanthanum zirconium oxide solid-state electrolyte.

[0007] As a preferred scheme of the present application, the lanthanum oxide is calcined at 1000-1100℃ for 2-3h before use to remove impurities.

[0008] As a preferred scheme of the present application, the grinding medium for the S1 ball milling is zirconium oxide balls, and the ball-to-material ratio is 3-5:1.

[0009] As a preferred scheme of the present application, the S1 ball milling is performed at a rotation speed of 200-300r / min for 8-12h.

[0010] As a preferred scheme of the present application, the S2 pre-sintering is performed at a heating rate of 5-10℃ / min, heated to 800-900℃, and pre-sintered for 4-6h.

[0011] As a preferred scheme of the present application, the mass percentage of the polyvinyl alcohol solution is 5-10%.

[0012] As a preferred scheme of the present application, a layer of LLZO precursor powder is laid on the bottom of the alumina crucible during the S4 high-temperature sintering to prevent the round sheet from sticking to the crucible.

[0013] As a preferred scheme of the present application, the S4 high-temperature sintering is performed at a heating rate of 2-5℃ / min, heated to 1100-1200℃, and high-temperature sintered for 8-12h.

[0014] As a preferred scheme of the present application, the preparation method of the modified aluminum ion chelating agent is as follows: A1: 2-5 parts of (11-mercapto-undecyl)-trimethylammonium bromide, 100-120 parts of toluene, 2-8 parts of biphenyl-4,4''-dithiol, and 3-5 parts of triethylamine are added to a reaction kettle, stirred, heated to 45-55℃ under a nitrogen atmosphere, and reacted for 1-4h; A2: Continue to add 1-3 parts of lanthanum nitrate and 0.3-0.6 parts of stannous octoate, heat to 65-75℃, and react for 3-7 hours; after the reaction is completed, cool to room temperature, filter to remove insoluble matter, evaporate the filtrate by rotary evaporation, add 60-80 parts of petroleum ether, heat to 60-90℃, precipitate solid, filter and collect, vacuum dry to obtain modified aluminum ion chelating agent.

[0015] As a preferred embodiment of the present invention, the modified aluminum ion chelating agent is prepared by vacuum drying at a temperature of 50-60°C for a time of 6-8 hours.

[0016] I. Reaction Mechanism The mercapto group in (11-mercaptoundecyl)-trimethylammonium bromide works synergistically with the sulfur atom in biphenyl-4,4''-dithiol to form a multidentate chelate structure. Through sulfur-aluminum coordination bonds, it can strongly fix excess aluminum ions in the system, avoiding interference with the ordered arrangement of lithium lanthanum zirconium oxide (LLZO) lattice. At the same time, the lanthanum ions in lanthanum nitrate can form stable coordination with oxygen ions in the electrolyte matrix, effectively enhancing the interfacial bonding force between the modified aluminum ion chelator and the LLZO precursor, reducing the detachment of the chelate from the precursor surface during pre-sintering, and ensuring the stability of subsequent preparation processes.

[0017] Technical effect Significantly improves room temperature ionic conductivity: The modified aluminum ion chelating agent prepared in this invention can precisely control the distribution state of aluminum ions in the LLZO system, avoid lattice distortion caused by uneven aluminum ion distribution, thereby reducing the obstruction in the ion conduction process and effectively improving the room temperature ionic conductivity of lithium lanthanum zirconium oxide solid electrolyte.

[0018] Optimized chemical stability: After adding a modified aluminum ion chelating agent, the hygroscopic resistance of lithium lanthanum zirconium oxygen solid electrolyte is significantly improved. It is not easy to absorb moisture and deteriorate after being placed in the air. It can maintain the structural integrity and chemical properties of the material itself for a long time and reduce the impact of environmental factors on the material performance.

[0019] Enhanced interface stability: Modified aluminum ion chelating agents improve the interfacial bonding state between the electrolyte and the lithium metal sheet, reduce possible side reactions during the contact process, and enable the electrolyte and lithium metal sheet to maintain stable interfacial performance even after long-term contact, avoid abnormal increase in interfacial impedance, and ensure the long-term reliability of the battery system. Attached Figure Description

[0020] Figure 1 The image shows an electron microscope image of the lithium lanthanum zirconium oxide solid electrolyte prepared in Example 2. Detailed Implementation

[0021] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description is provided in conjunction with embodiments and comparative examples: 1. Ionic conductivity: Ionic conductivity was measured using electrochemical impedance spectroscopy (EIS) with an electrochemical workstation (model CHI660E, Shanghai Chenhua). The ionic conductivity was calculated based on the Nyquist curve in the impedance spectrum using the formula σ=L / (R×S) (σ is the ionic conductivity, L is the electrolyte thickness, R is the total impedance, and S is the electrolyte cross-sectional area).

[0022] 2. Chemical stability: The solid electrolyte was placed in air at room temperature and 60% relative humidity for 30 days, and the moisture absorption was determined by XRD and weight change.

[0023] 3. Interface stability: Solid electrolyte and lithium metal sheet were assembled into Li / electrolyte / Li symmetric battery, placed at room temperature for 100h, and the AC impedance before and after placement was tested to determine the interface reaction. Example 1

[0024] A method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte, comprising the following steps: S1 Ball Milling Mixing: Add 20g lithium carbonate, 48g lanthanum oxide, 20g zirconium oxide, and 2g aluminum nitrate to a ball mill jar, add 100g anhydrous ethanol as a dispersant, and ball mill to obtain a mixed slurry; S2 Drying and Pre-calcination: The mixed slurry was vacuum dried at 60℃ for 4 hours, 0.5g of modified aluminum ion chelating agent was added, mixed and ground, passed through a 200-mesh sieve, and placed in an alumina crucible for pre-calcination in an air atmosphere to obtain the LLZO precursor. S3 tableting: The LLZO precursor is ground through a 300-mesh sieve, 1g of polyvinyl alcohol solution is added as a binder, and after being mixed evenly, it is pressed into a disc under a pressure of 10MPa. S4 High-Temperature Sintering: The disc is placed in an alumina crucible and sintered at high temperature in an air atmosphere; then cooled to room temperature to obtain an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte.

[0025] The lanthanum oxide is calcined at 1000℃ for 2 hours before use to remove impurities.

[0026] The grinding media of the S1 ball mill is zirconia balls, and the ball-to-material ratio is 3:1.

[0027] The S1 ball milling speed is 200 r / min, and the ball milling time is 8 h.

[0028] The heating rate of the S2 pre-firing is 5℃ / min, the temperature is raised to 800℃, and the pre-firing time is 4h.

[0029] The polyvinyl alcohol solution has a mass percentage of 5%.

[0030] During the S4 high-temperature sintering process, a layer of LLZO precursor powder is laid at the bottom of the alumina crucible to prevent the discs from sticking to the crucible.

[0031] The heating rate of the S4 high-temperature sintering is 2℃ / min, the temperature is raised to 1100℃, and the high-temperature sintering time is 8h.

[0032] The preparation method of the modified aluminum ion chelating agent is as follows: A1: Add 2g (11-mercaptoundecyl)-trimethylammonium bromide, 100g toluene, 2g biphenyl-4,4''-dithiol, and 3g triethylamine to a reaction vessel, stir and heat to 45°C under a nitrogen atmosphere, and react for 1 hour; A2: Continue to add 1g of lanthanum nitrate and 0.3g of stannous octoate, heat to 65℃, and react for 3h; after the reaction is completed, cool to room temperature, filter to remove insoluble matter, evaporate the filtrate by rotary evaporation, add 60g of petroleum ether, heat to 60℃, precipitate solid, filter and collect, vacuum dry to obtain modified aluminum ion chelating agent.

[0033] The vacuum drying temperature is 50℃ and the time is 6 hours. Example 2

[0034] A method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte, comprising the following steps: S1 Ball Milling Mixing: Add 23g lithium carbonate, 52g lanthanum oxide, 22g zirconium oxide, and 3g aluminum nitrate to a ball mill jar, add 110g anhydrous ethanol as a dispersant, and ball mill to obtain a mixed slurry; S2 Drying and Pre-calcination: The mixed slurry was vacuum dried at 65°C for 5 hours, 0.6g of modified aluminum ion chelating agent was added, mixed and ground, passed through a 200-mesh sieve, and placed in an alumina crucible for pre-calcination in an air atmosphere to obtain the LLZO precursor. S3 tableting: The LLZO precursor is ground through a 300-mesh sieve, 2g of polyvinyl alcohol solution is added as a binder, and after being mixed evenly, it is pressed into a disc under a pressure of 15MPa. S4 High-Temperature Sintering: The disc is placed in an alumina crucible and sintered at high temperature in an air atmosphere; then cooled to room temperature to obtain an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte.

[0035] The lanthanum oxide is calcined at 1040℃ for 2.5h before use to remove impurities.

[0036] The grinding media of the S1 ball mill is zirconia balls, and the ball-to-material ratio is 4:1.

[0037] The S1 ball milling speed is 250 r / min, and the ball milling time is 9 h.

[0038] The heating rate of the S2 pre-firing is 6℃ / min, the temperature is raised to 840℃, and the pre-firing time is 5h.

[0039] The polyvinyl alcohol solution has a mass percentage of 6%.

[0040] During the S4 high-temperature sintering process, a layer of LLZO precursor powder is laid at the bottom of the alumina crucible to prevent the discs from sticking to the crucible.

[0041] The heating rate of the S4 high-temperature sintering is 3℃ / min, the temperature is raised to 1140℃, and the high-temperature sintering time is 9h.

[0042] The preparation method of the modified aluminum ion chelating agent is as follows: A1: Add 3g of (11-mercaptoundecyl)-trimethylammonium bromide, 105g of toluene, 4g of biphenyl-4,4''-dithiol, and 4g of triethylamine to a reaction vessel, stir and heat to 50°C under a nitrogen atmosphere, and react for 2 hours; A2: Continue to add 2g of lanthanum nitrate and 0.4g of stannous octoate, heat to 70℃, and react for 4h; after the reaction is completed, cool to room temperature, filter to remove insoluble matter, evaporate the filtrate by rotary evaporation, add 65g of petroleum ether, heat to 70℃, precipitate solid, filter and collect, vacuum dry to obtain modified aluminum ion chelating agent.

[0043] The vacuum drying temperature is 55℃ and the time is 7 hours. Example 3

[0044] A method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte, comprising the following steps: S1 Ball Milling Mixing: Add 28g lithium carbonate, 55g lanthanum oxide, 26g zirconium oxide, and 4g aluminum nitrate to a ball mill jar, add 130g anhydrous ethanol as a dispersant, and ball mill to obtain a mixed slurry; S2 Drying and Pre-calcination: The mixed slurry was vacuum dried at 75°C for 5 hours, 0.7g of modified aluminum ion chelating agent was added, mixed and ground, passed through a 100-mesh sieve, and placed in an alumina crucible for pre-calcination in an air atmosphere to obtain the LLZO precursor. S3 tableting: The LLZO precursor is ground through a 200-mesh sieve, 2g of polyvinyl alcohol solution is added as a binder, and after being mixed evenly, it is pressed into a disc under a pressure of 15MPa. S4 High-Temperature Sintering: The disc is placed in an alumina crucible and sintered at high temperature in an air atmosphere; then cooled to room temperature to obtain an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte.

[0045] The lanthanum oxide is calcined at 1080℃ for 2.5h before use to remove impurities.

[0046] The grinding media of the S1 ball mill is zirconia balls, and the ball-to-material ratio is 4:1.

[0047] The S1 ball milling speed is 250 r / min, and the ball milling time is 11 h.

[0048] The heating rate of the S2 pre-firing is 8℃ / min, the temperature is raised to 880℃, and the pre-firing time is 5h.

[0049] The polyvinyl alcohol solution has a mass percentage of 8%.

[0050] During the S4 high-temperature sintering process, a layer of LLZO precursor powder is laid at the bottom of the alumina crucible to prevent the discs from sticking to the crucible.

[0051] The heating rate of the S4 high-temperature sintering is 4℃ / min, the temperature is raised to 1180℃, and the high-temperature sintering time is 11h.

[0052] The preparation method of the modified aluminum ion chelating agent is as follows: A1: Add 4g of (11-mercaptoundecyl)-trimethylammonium bromide, 115g of toluene, 6g of biphenyl-4,4''-dithiol, and 4g of triethylamine to a reaction vessel, stir and heat to 50°C under a nitrogen atmosphere, and react for 3 hours; A2: Continue to add 2g of lanthanum nitrate and 0.5g of stannous octoate, heat to 70℃, and react for 6h; after the reaction is completed, cool to room temperature, filter to remove insoluble matter, evaporate the filtrate by rotary evaporation, add 75g of petroleum ether, heat to 80℃, precipitate solid, filter and collect, vacuum dry to obtain modified aluminum ion chelating agent.

[0053] The vacuum drying temperature is 55℃ and the time is 7 hours. Example 4

[0054] A method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte, comprising the following steps: S1 Ball Milling Mixing: Add 30g lithium carbonate, 58g lanthanum oxide, 28g zirconium oxide, and 5g aluminum nitrate to a ball mill jar, add 140g anhydrous ethanol as a dispersant, and ball mill to obtain a mixed slurry; S2 Drying and Pre-calcination: The mixed slurry was vacuum dried at 80℃ for 6 hours, 0.8g of modified aluminum ion chelating agent was added, mixed and ground, passed through a 100-mesh sieve, and placed in an alumina crucible for pre-calcination in an air atmosphere to obtain the LLZO precursor. S3 tableting: The LLZO precursor is ground through a 200-mesh sieve, 3g of polyvinyl alcohol solution is added as a binder, and after being mixed evenly, it is pressed into a disc under a pressure of 20MPa. S4 High-Temperature Sintering: The disc is placed in an alumina crucible and sintered at high temperature in an air atmosphere; then cooled to room temperature to obtain an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte.

[0055] The lanthanum oxide is calcined at 1100℃ for 3 hours before use to remove impurities.

[0056] The grinding media of the S1 ball mill is zirconia balls, and the ball-to-material ratio is 5:1.

[0057] The S1 ball milling speed is 300 r / min, and the ball milling time is 12 h.

[0058] The heating rate of the S2 pre-firing is 10℃ / min, the temperature is raised to 900℃, and the pre-firing time is 6h.

[0059] The polyvinyl alcohol solution has a mass percentage of 10%.

[0060] During the S4 high-temperature sintering process, a layer of LLZO precursor powder is laid at the bottom of the alumina crucible to prevent the discs from sticking to the crucible.

[0061] The heating rate of the S4 high-temperature sintering is 5℃ / min, the temperature is raised to 1200℃, and the high-temperature sintering time is 12h.

[0062] The preparation method of the modified aluminum ion chelating agent is as follows: A1: Add 5g of (11-mercaptoundecyl)-trimethylammonium bromide, 120g of toluene, 8g of biphenyl-4,4''-dithiol, and 5g of triethylamine to a reaction vessel, stir and heat to 55°C under a nitrogen atmosphere, and react for 4 hours; A2: Continue to add 3g lanthanum nitrate and 0.6g stannous octoate, heat to 75℃, and react for 7h; after the reaction is completed, cool to room temperature, filter to remove insoluble matter, evaporate the filtrate by rotary evaporation, add 80g petroleum ether, heat to 90℃, precipitate solid, filter and collect, vacuum dry to obtain modified aluminum ion chelating agent.

[0063] The vacuum drying temperature is 60℃ and the time is 8 hours.

[0064] Comparative Example 1 A method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte, comprising the following steps: S1 Ball Milling Mixing: Add 20g lithium carbonate, 48g lanthanum oxide, 20g zirconium oxide, and 2g aluminum nitrate to a ball mill jar, add 100g anhydrous ethanol as a dispersant, and ball mill to obtain a mixed slurry; S2 Drying and Pre-calcination: The mixed slurry was vacuum dried at 60°C for 4 hours, ground, passed through a 200-mesh sieve, placed in an alumina crucible, and pre-calcined in an air atmosphere to obtain the LLZO precursor. S3 tableting: The LLZO precursor is ground through a 300-mesh sieve, 1g of polyvinyl alcohol solution is added as a binder, and after being mixed evenly, it is pressed into a disc under a pressure of 10MPa. S4 High-Temperature Sintering: The disc is placed in an alumina crucible and sintered at high temperature in an air atmosphere; then cooled to room temperature to obtain an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte.

[0065] The lanthanum oxide is calcined at 1000℃ for 2 hours before use to remove impurities.

[0066] The grinding media of the S1 ball mill is zirconia balls, and the ball-to-material ratio is 3:1.

[0067] The S1 ball milling speed is 200 r / min, and the ball milling time is 8 h.

[0068] The heating rate of the S2 pre-firing is 5℃ / min, the temperature is raised to 800℃, and the pre-firing time is 4h.

[0069] The polyvinyl alcohol solution has a mass percentage of 5%.

[0070] During the S4 high-temperature sintering process, a layer of LLZO precursor powder is laid at the bottom of the alumina crucible to prevent the discs from sticking to the crucible.

[0071] The heating rate of the S4 high-temperature sintering is 2℃ / min, the temperature is raised to 1100℃, and the high-temperature sintering time is 8h.

[0072] Comparative Example 2 A method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte, comprising the following steps: S1 Ball Milling Mixing: Add 20g lithium carbonate, 48g lanthanum oxide, 20g zirconium oxide, and 2g aluminum nitrate to a ball mill jar, add 100g anhydrous ethanol as a dispersant, and ball mill to obtain a mixed slurry; S2 Drying and Pre-calcination: The mixed slurry was vacuum dried at 60℃ for 4 hours, 0.5g of modified aluminum ion chelating agent was added, mixed and ground, passed through a 200-mesh sieve, and placed in an alumina crucible for pre-calcination in an air atmosphere to obtain the LLZO precursor. S3 tableting: The LLZO precursor is ground through a 300-mesh sieve, 1g of polyvinyl alcohol solution is added as a binder, and after being mixed evenly, it is pressed into a disc under a pressure of 10MPa. S4 High-Temperature Sintering: The disc is placed in an alumina crucible and sintered at high temperature in an air atmosphere; then cooled to room temperature to obtain an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte.

[0073] The lanthanum oxide is calcined at 1000℃ for 2 hours before use to remove impurities.

[0074] The grinding media of the S1 ball mill is zirconia balls, and the ball-to-material ratio is 3:1.

[0075] The S1 ball milling speed is 200 r / min, and the ball milling time is 8 h.

[0076] The heating rate of the S2 pre-firing is 5℃ / min, the temperature is raised to 800℃, and the pre-firing time is 4h.

[0077] The polyvinyl alcohol solution has a mass percentage of 5%.

[0078] During the S4 high-temperature sintering process, a layer of LLZO precursor powder is laid at the bottom of the alumina crucible to prevent the discs from sticking to the crucible.

[0079] The heating rate of the S4 high-temperature sintering is 2℃ / min, the temperature is raised to 1100℃, and the high-temperature sintering time is 8h.

[0080] The preparation method of the modified aluminum ion chelating agent is as follows: A1: Add 2g of (11-mercaptoundecyl)-trimethylammonium bromide, 100g of toluene, and 3g of triethylamine to a reaction vessel, stir and heat to 45°C under a nitrogen atmosphere, and react for 1 hour; A2: Continue to add 1g of lanthanum nitrate and 0.3g of stannous octoate, heat to 65℃, and react for 3h; after the reaction is completed, cool to room temperature, filter to remove insoluble matter, evaporate the filtrate by rotary evaporation, add 60g of petroleum ether, heat to 60℃, precipitate solid, filter and collect, vacuum dry to obtain modified aluminum ion chelating agent.

[0081] The vacuum drying temperature is 50℃ and the time is 6 hours.

[0082] Comparative Example 3 A method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte, comprising the following steps: S1 Ball Milling Mixing: Add 20g lithium carbonate, 48g lanthanum oxide, 20g zirconium oxide, and 2g aluminum nitrate to a ball mill jar, add 100g anhydrous ethanol as a dispersant, and ball mill to obtain a mixed slurry; S2 Drying and Pre-calcination: The mixed slurry was vacuum dried at 60℃ for 4 hours, 0.5g of modified aluminum ion chelating agent was added, mixed and ground, passed through a 200-mesh sieve, and placed in an alumina crucible for pre-calcination in an air atmosphere to obtain the LLZO precursor. S3 tableting: The LLZO precursor is ground through a 300-mesh sieve, 1g of polyvinyl alcohol solution is added as a binder, and after being mixed evenly, it is pressed into a disc under a pressure of 10MPa. S4 High-Temperature Sintering: The disc is placed in an alumina crucible and sintered at high temperature in an air atmosphere; then cooled to room temperature to obtain an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte.

[0083] The lanthanum oxide is calcined at 1000℃ for 2 hours before use to remove impurities.

[0084] The grinding media of the S1 ball mill is zirconia balls, and the ball-to-material ratio is 3:1.

[0085] The S1 ball milling speed is 200 r / min, and the ball milling time is 8 h.

[0086] The heating rate of the S2 pre-firing is 5℃ / min, the temperature is raised to 800℃, and the pre-firing time is 4h.

[0087] The polyvinyl alcohol solution has a mass percentage of 5%.

[0088] During the S4 high-temperature sintering process, a layer of LLZO precursor powder is laid at the bottom of the alumina crucible to prevent the discs from sticking to the crucible.

[0089] The heating rate of the S4 high-temperature sintering is 2℃ / min, the temperature is raised to 1100℃, and the high-temperature sintering time is 8h.

[0090] The preparation method of the modified aluminum ion chelating agent is as follows: A1: Add 2g (11-mercaptoundecyl)-trimethylammonium bromide, 100g toluene, 2g biphenyl-4,4''-dithiol, and 3g triethylamine to a reaction vessel, stir and heat to 45°C under a nitrogen atmosphere, and react for 1 hour; A2: After the reaction is complete, cool to room temperature, filter to remove insoluble matter, evaporate the filtrate by rotary evaporation, add 60g of petroleum ether, heat to 60℃, precipitate solid, filter and collect, vacuum dry to obtain modified aluminum ion chelating agent.

[0091] The vacuum drying temperature is 50℃ and the time is 6 hours.

[0092] The test results of the examples and comparative examples are shown in Table 1.

[0093] Table 1 Ionic conductivity (S / cm) 30-day air standing weight change (%) 100 h Li interface impedance change (%) Example 1 1.79 x 10 -3 ]] 0.18 4.4 Example 2 1.83 x 10 -3 ]]> 0.15 4.2 Example 3 1.91 x 10 -3 ]] 0.10 3.6 Example 4 1.96 x 10 -3 ]] 0.08 3.3 Comparative Example 1 0.43 x 10 -3 ]] 1.57 25.5 Comparative Example 2 1.38 x 10 -3 ]]> 0.65 9.5 Comparative Example 3 1.45 x 10 -3 ]]> 0.52 8.3 As can be seen from the data comparison in Table 1, the preparation method proposed in this invention (Examples 1-4) shows significant advantages over the control scheme (Comparative Examples 1-3) in terms of core performance indicators: Regarding ionic conductivity: the room temperature ionic conductivity of the product in the example was much higher than that of Comparative Example 1 (without modified aluminum ion chelating agent), and also better than that of Comparative Example 2 (modified aluminum ion chelating agent lacking biphenyl-4,4''-dithiol) and Comparative Example 3 (modified aluminum ion chelating agent lacking lanthanum nitrate and stannous octoate), indicating that the modified aluminum ion chelating agent in the complete formulation is crucial for improving ion conduction efficiency. Regarding chemical stability: the weight change of the product in the example after being placed in air for 30 days was much smaller than that of the comparative examples, indicating that the electrolyte prepared by the method of the present invention has stronger moisture resistance and better chemical stability; Regarding interface stability: the change in interface impedance of the product in the example after 100 hours of contact with lithium metal was significantly lower than that of the comparative examples, proving that the modified aluminum ion chelating agent can effectively improve the interfacial compatibility between the electrolyte and lithium metal, reduce interfacial side reactions, and improve the long-term stability of the interface.

[0094] In summary, by adding a modified aluminum ion chelating agent with a complete formula, this invention successfully achieved a synergistic improvement in the ionic conductivity, chemical stability, and interfacial stability of lithium lanthanum zirconium oxide solid electrolyte, demonstrating significant performance advantages.

[0095] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte, comprising the following steps, in parts by mass: S1 Ball Milling Mixing: Add 20-30 parts lithium carbonate, 48-58 parts lanthanum oxide, 20-28 parts zirconium oxide, and 2-5 parts aluminum nitrate to a ball mill jar, add 100-140 parts anhydrous ethanol as a dispersant, and ball mill to obtain a mixed slurry; S2 Drying and Pre-calcination: The mixed slurry is vacuum dried at 60-80℃ for 4-6 hours, 0.5-0.8 parts of modified aluminum ion chelating agent are added, mixed and ground, and after passing through a 100-200 mesh sieve, it is placed in an alumina crucible and pre-calcined in an air atmosphere to obtain the LLZO precursor. S3 tableting: Grind the LLZO precursor through a 200-300 mesh sieve, add 1-3 parts of polyvinyl alcohol solution as a binder, mix evenly, and then press into round tablets under a pressure of 10-20MPa. S4 High-Temperature Sintering: The disc is placed in an alumina crucible and sintered at high temperature in an air atmosphere; then cooled to room temperature to obtain an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte. The modified aluminum ion chelating agent is prepared by reacting (11-mercaptoundecyl)-trimethylammonium bromide, biphenyl-4,4''-dithiol, triethylamine, lanthanum nitrate, and stannous octoate.

2. The method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte according to claim 1, characterized in that: The lanthanum oxide is calcined at 1000-1100℃ for 2-3 hours before use to remove impurities.

3. The method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte according to claim 1, characterized in that: The grinding media of the S1 ball mill is zirconia balls, and the ball-to-material ratio is 3-5:

1.

4. The method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte according to claim 1, characterized in that: The S1 ball mill operates at a speed of 200-300 r / min and a milling time of 8-12 h.

5. The method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte according to claim 1, characterized in that: The heating rate of the S2 pre-firing is 5-10℃ / min, the temperature is raised to 800-900℃, and the pre-firing time is 4-6h.

6. The method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte according to claim 1, characterized in that: The polyvinyl alcohol solution has a mass percentage of 5-10%.

7. The method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte according to claim 1, characterized in that: During the S4 high-temperature sintering process, a layer of LLZO precursor powder is laid at the bottom of the alumina crucible to prevent the discs from sticking to the crucible.

8. The method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte according to claim 1, characterized in that: The heating rate of the S4 high-temperature sintering is 2-5℃ / min, the temperature is raised to 1100-1200℃, and the high-temperature sintering time is 8-12h.

9. The method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte according to claim 1, characterized in that: The preparation method of the modified aluminum ion chelating agent is as follows: A1: According to the mass fractions, add 2-5 parts of (11-mercaptoundecyl)-trimethylammonium bromide, 100-120 parts of toluene, 2-8 parts of biphenyl-4,4''-dithiol, and 3-5 parts of triethylamine to the reaction vessel, stir and heat to 45-55℃ under a nitrogen atmosphere, and react for 1-4 hours; A2: Continue to add 1-3 parts of lanthanum nitrate and 0.3-0.6 parts of stannous octoate, heat to 65-75℃, and react for 3-7 hours; after the reaction is completed, cool to room temperature, filter to remove insoluble matter, evaporate the filtrate by rotary evaporation, add 60-80 parts of petroleum ether, heat to 60-90℃, precipitate solid, filter and collect, vacuum dry to obtain modified aluminum ion chelating agent.

10. The method for preparing an aluminum-doped lithium lanthanum zirconium oxide solid electrolyte according to claim 9, characterized in that: The vacuum drying temperature is 50-60℃, and the time is 6-8 hours.

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