Gallium and zinc doped lithium lanthanum zirconium oxide

Abstract

The invention relates to a gallium and zinc doped lithium lanthanum zirconium oxide, which is formed by the following steps of: mixing lithium carbonate powder, lanthanum oxide powder, zirconium dioxide powder, gallium oxide powder and zinc oxide powder in an emulsifying machine to form mixed powder; putting the mixed powder into a wet grinding machine for grinding to obtain a plurality of mixture powder; placing the plurality of mixture powders in an oven for drying, and placing the mixture powders in a grinding bowl for grinding to form a plurality of mixture fine powders; then placing the plurality of mixture fine powders into a sintering furnace for sintering treatment of two-stage gas injection, in the first stage, raising the sintering temperature from room temperature to 800-900 DEG C, and injecting oxygen-enriched gas into the sintering furnace; in the second stage, replacing the originally injected dilute oxygen gas with pure oxygen, injecting the pure oxygen into the sintering furnace, and completing the sintering process in the environment of 800-900 DEG C to obtain the gallium and zinc doped lithium lanthanum zirconium oxide; wherein the dilute oxygen system means that the proportion of oxygen in the whole gas is less than 30%.

Description

Technical Field

[0001] This invention relates to solid electrolytes, particularly a gallium- and zinc-doped lithium lanthanum zirconium oxide. Background Technology

[0002] In battery manufacturing, lithium lanthanum zirconium oxide (LLZO) is a novel solid electrolyte with excellent ionic conductivity and stability, making it an ideal material for solid-state lithium batteries.

[0003] Traditionally, the method of manufacturing solid electrolytes for lithium batteries using compounds such as zirconium dioxide (ZrO2), lanthanum oxide (La2O3), and lithium carbonate (Li2CO3) involves mixing and grinding a slurry of the three initial compounds in a certain proportion in a ball mill, and then sintering it once with oxygen during the reaction to generate lithium lanthanum zirconium oxide.

[0004] However, existing lithium lanthanum zirconium oxides (LLZOs) still require improvement in terms of ionic conductivity, mechanical properties, interfacial impedance, and other aspects. Some researchers have modified LLZOs, for example by adding gallium to improve overall battery performance. However, this doping still cannot achieve optimal battery efficiency. Therefore, the inventors aim to propose a gallium- and zinc-doped LLZO. Zinc oxide offers several advantages for modifying LLZO, including improved ionic conductivity, enhanced mechanical properties, reduced interfacial impedance, suppression of side reactions, and cost reduction.

[0005] Therefore, the present invention aims to provide a novel single-mixing and single-sintering process for gallium- and zinc-doped lithium lanthanum zirconium oxide, and the physical objects produced by this process, in order to overcome the aforementioned deficiencies in the prior art. Summary of the Invention

[0006] The purpose of this invention is to solve the problems mentioned above in the prior art. This invention proposes a gallium- and zinc-doped lithium lanthanum zirconium oxide. The addition of zinc oxide to LLZO has several advantages in modifying it, including improved ionic conductivity, enhanced mechanical properties, reduced interfacial impedance, suppression of side reactions, and reduced cost. These advantages make LLZO-ZnO composite materials promising for applications in solid-state batteries. The advantages of ZnO doping in LLZO are mainly reflected in the following aspects: improved mechanical properties: enhancing the strength and toughness of the material; improved interfacial compatibility: reducing interfacial impedance and improving battery performance.

[0007] To achieve the above objectives, this invention proposes a gallium- and zinc-doped lithium lanthanum zirconium oxide, which is formed as follows: lithium carbonate powder, lanthanum oxide powder, zirconium dioxide powder, gallium oxide powder, and zinc oxide powder are placed in an emulsifier and mixed to form a uniform mixed powder; then the mixed powder is placed in a wet grinder and ground to obtain multiple mixed powders; then the multiple mixed powders are placed in an oven for drying to remove moisture, resulting in multiple blocky mixtures; then the multiple blocky mixtures are placed in a grinding bowl for grinding to form multiple fine mixed powders; then the multiple fine mixed powders are placed in a kiln... A two-stage gas-injection sintering process is performed in a sintering furnace. In the first stage, the sintering temperature is raised from room temperature to 800℃~900℃, and dilute oxygen gas is injected into the sintering furnace. In the second stage, the originally injected dilute oxygen gas is replaced with pure oxygen and the sintering process is completed at 800℃~900℃ to obtain gallium and zinc-doped lithium lanthanum zirconium oxide. During the sintering process, gallium and zinc in the gallium oxide and zinc oxide will enter the original lithium lanthanum zirconium oxide, partially replacing the lithium and zirconium therein, thus forming the gallium and zinc-doped lithium lanthanum zirconium oxide. The dilute oxygen system refers to the total gas volume in which the proportion of oxygen is less than 30%.

[0008] Furthermore, the chemical formula of this gallium- and zinc-doped lithium lanthanum zirconium oxide is:

[0009] Li 7-a La3Zr 1.7-x Ga y Zn z O 12 ;

[0010] 2x + 3y + 2z = a

[0011] a>0, x>0, y>0, z>0.

[0012] Furthermore, the lithium carbonate powder contains between 20% and 25% by weight; the lanthanum oxide powder contains between 40% and 45% by weight; the zirconium dioxide powder contains between 20% and 25% by weight; the gallium oxide powder contains between 3% and 5% by weight; and the zinc oxide powder contains between 3% and 5% by weight.

[0013] Furthermore, the grinding is carried out in a wet grinding mill for 2 hours, and the size of the ground powder is less than 1 micrometer; the wet grinding mill also includes pure water as a medium; the weight ratio of the pure water to the mixed powder is 8:2.

[0014] Furthermore, during the drying process in the oven, the oven temperature is 80±5℃, and the drying time is 3 to 4 hours.

[0015] Furthermore, in the first stage, the temperature is increased at a rate of 2°C / minute.

[0016] Furthermore, the rare oxygen gas is air. Attached Figure Description

[0017] Figure 1 This is a flowchart of the process for forming the gallium- and zinc-doped lithium lanthanum zirconium oxide of the present invention.

[0018] Figure 2 This is a flowchart of steps A and B of the present invention.

[0019] Figure 3 This is a flowchart of step C of the present invention.

[0020] Figure 4 This is a flowchart of steps D and E of the present invention.

[0021] in,

[0022] 200. Emulsifier; 210. Wet grinder; 220. Oven; 230. Grinding bowl; 240. Sintering furnace. Detailed Implementation

[0023] The features and advantages of the invention will be further understood from the following description, and please refer to the accompanying drawings while reading.

[0024] The present invention will now be described in detail with reference to the accompanying drawings, along with a preferred embodiment of the invention.

[0025] I. Process for gallium- and zinc-doped lithium lanthanum zirconium oxide

[0026] Please refer to Figures 1 to 4 The diagram illustrates a single-mixing and single-sintering process for gallium and zinc-doped lithium lanthanum zirconium oxide (Ga&Zn dope-LLZO) of the present invention. Lithium carbonate (Li₂CO₃) powder, lanthanum oxide (La₂O₃) powder, zirconium dioxide (ZrO₂) powder, gallium oxide (Ga₂O₃) powder, and zinc oxide (ZnO) powder are mixed and sintered in a single process to obtain gallium and zinc-doped lithium lanthanum zirconium oxide (Ga&Zn dope-LLZO). In the single-sintering process, two stages of gas injection are performed. The first stage involves the injection of dilute oxygen gas, and the second stage involves the injection of pure oxygen gas.

[0027] The process includes the following steps:

[0028] Step A:

[0029] Take lithium carbonate powder,

[0030] Lanthanum oxide powder,

[0031] Zirconium dioxide powder,

[0032] Gallium oxide powder,

[0033] and zinc oxide powder,

[0034] The lithium carbonate powder, lanthanum oxide powder, zirconium dioxide powder, gallium oxide powder, and zinc oxide powder are placed into an emulsifier 200 and mixed to form a uniform mixed powder.

[0035] The lithium carbonate powder contains 20% to 25% by weight; the lanthanum oxide powder contains 40% to 45% by weight; the zirconium dioxide powder contains 20% to 25% by weight; the gallium oxide powder contains 3% to 5% by weight; and the zinc oxide powder contains 3% to 5% by weight.

[0036] Step B: The mixed powder is placed in a wet grinder 210 for grinding for 2 hours to obtain multiple mixed powders with a particle size of less than 1 micrometer (D50 < 1 μm, where D50 refers to the median of the particle distribution). The wet grinder 210 also includes pure water as a medium. The weight ratio of the pure water to the mixed powder is 8:2.

[0037] Step C: Place the multiple mixture powders into an oven 220 for drying to remove moisture. The temperature of the oven 220 is approximately 80±5℃, and the drying process lasts for 3 to 4 hours, resulting in multiple block mixtures. Then, place the multiple block mixtures into a grinding bowl 230 for grinding to form multiple fine powders.

[0038] Step D: The multiple fine powder mixtures are placed into a sintering furnace 240 for sintering. The sintering temperature is increased from room temperature to 800℃~900℃ at a rate of 2℃ / min. During the process of heating to 800℃~900℃, rare oxygen gas is injected into the sintering furnace 240.

[0039] The rarefied oxygen system refers to a gas in which the proportion of oxygen is less than 30% in the total gas composition, such as air. Because of its low oxygen content, the oxygen in this rarefied oxygen gas does not react effectively with other molecules during this stage of combustion, thus yielding high-purity cubic-phase lithium lanthanum zirconium oxide doped with gallium and zinc.

[0040] Step E: When the temperature reaches 800℃~900℃, the previously injected dilute oxygen gas is replaced with pure oxygen and injected into the sintering furnace 240. The injection method involves injecting liquid oxygen into the sintering furnace 240 and vaporizing it to replace the original air inside the furnace. The temperature is then held at 800℃~900℃ for 10 hours to complete the sintering process and obtain the sintered product, namely the gallium and zinc-doped lithium lanthanum zirconium oxide of this invention. A preferred holding temperature is 800℃.

[0041] During the sintering process, gallium and zinc from the gallium oxide and zinc oxide will enter the original lithium lanthanum zirconium oxide, partially replacing the lithium and zirconium within it, thus forming the gallium- and zinc-doped lithium lanthanum zirconium oxide. Its chemical formula is:

[0042] Li 7-a La3Zr 1.7-x Ga y Zn z O 12 ;

[0043] 2x + 3y + 2z = a

[0044] a>0, x>0, y>0, z>0.

[0045] Step F: High-purity gallium- and zinc-doped lithium lanthanum zirconium oxide can be extracted by filtration.

[0046] II. Physical specimens of gallium- and zinc-doped lithium lanthanum zirconium oxide

[0047] The present invention also includes gallium- and zinc-doped lithium lanthanum zirconium oxide produced by the above steps.

[0048] The gallium- and zinc-doped lithium lanthanum zirconium oxide is prepared by mixing lithium carbonate powder, lanthanum oxide powder, zirconium dioxide powder, gallium oxide powder, and zinc oxide powder in an emulsifier 200 to form a homogeneous powder mixture. This mixture is then ground in a wet mill 210 to obtain multiple powder mixtures. These powder mixtures are then dried in an oven 220 to remove moisture, resulting in multiple block-shaped mixtures. These block-shaped mixtures are then ground in a grinding bowl 230 to form multiple fine powder mixtures. Finally, these fine powder mixtures are placed in a sintering furnace 240 for a two-stage gas-injection sintering process. In the first stage, the sintering temperature is raised from room temperature to 800℃–900℃, and rarefied oxygen gas is injected into the furnace. In the second stage, the rarefied oxygen gas is replaced with pure oxygen, and the sintering process is completed at 800℃–900℃ to obtain the gallium- and zinc-doped lithium lanthanum zirconium oxide. During the sintering process, gallium and zinc from the gallium oxide and zinc oxide will enter the original lithium lanthanum zirconium oxide, partially replacing the lithium and zirconium therein. This forms the gallium and zinc-doped lithium lanthanum zirconium oxide of the present invention.

[0049] The chemical formula of the gallium- and zinc-doped lithium lanthanum zirconium oxide is:

[0050] Li 7-a La3Zr 1.7-x Ga y Zn z O 12 ;

[0051] 2x + 3y + 2z = a

[0052] a>0, x>0, y>0, z>0.

[0053] The lithium carbonate powder contains 20% to 25% by weight; the lanthanum oxide powder contains 40% to 45% by weight; the zirconium dioxide powder contains 20% to 25% by weight; the gallium oxide powder contains 3% to 5% by weight; and the zinc oxide powder contains 3% to 5% by weight.

[0054] The grinding process is carried out in a wet grinder 210 for 2 hours, resulting in a powder size of less than 1 micrometer (D50 < 1 μm, where D50 refers to the median of the particle size distribution). The wet grinder 210 also includes pure water as a medium. The weight ratio of the pure water to the mixed powder is 8:2.

[0055] During the oven drying process, the temperature of the oven (220) is approximately 80±5℃, and the drying process lasts for 3 to 4 hours.

[0056] During the first stage of sintering, the temperature is increased at a rate of 2℃ / minute.

[0057] The rarefied oxygen system refers to a gas in which the proportion of oxygen is less than 30% in the total gas composition, such as air. Because of its low oxygen content, the oxygen in this rarefied oxygen gas does not react effectively with other molecules during this stage of combustion, thus yielding high-purity cubic gallium and zinc-doped lithium lanthanum zirconium oxide.

[0058] The addition of zinc oxide in this invention has several advantages, including: improving ionic conductivity and reducing the Li content in LLZO. + Diffusion barriers are eliminated, thereby increasing ionic conductivity. This helps improve the performance of solid-state electrolytes in lithium batteries. The addition of zinc oxide introduces specific defects into the LLZO lattice. These defects can act as hopping points for lithium ions, promoting their migration and thus improving ionic conductivity. Band structure: The introduction of zinc oxide may alter the band structure of LLZO, lowering the energy barrier for lithium ion migration and thus improving ionic conductivity. Furthermore, the presence of zinc oxide can reduce impedance at grain boundaries, which also significantly contributes to the overall improvement in conductivity.

[0059] Furthermore, Zn 2+ Ionic radius and Zr 4+ Similar, with Zn 2+ Ion-substituted Zr 4+ Afterward, oxygen vacancies can be generated, which can serve as fast channels for lithium-ion conduction.

[0060] The addition of zinc oxide can improve sintering properties: as a sintering aid, zinc oxide can lower the sintering temperature of LLZO and promote grain growth, thereby improving the material's density and mechanical strength. Phase diagram analysis of zinc oxide and LLZO can reveal their compatibility and phase stability at different temperatures. Under certain conditions, zinc oxide may form a liquid phase, promoting the sintering of LLZO, making the material denser, reducing resistance at grain boundaries, and facilitating ion conduction.

[0061] In addition, the addition of zinc oxide helps stabilize the cubic phase structure of LLZO, which typically has high lithium-ion conductivity.

[0062] Compared to other commonly used dopants such as gallium oxide and tantalum oxide, zinc oxide doping in LLZO offers several unique advantages: First, it provides higher chemical stability: Zinc oxide-doped LLZO typically exhibits better chemical stability when in contact with lithium metal. This is because zinc oxide forms fewer byproducts when reacting with lithium than Ga₂O₃ and Ta₂O₃, which helps reduce interfacial side reactions and thus extend battery life. Second, it improves interfacial compatibility: Zinc oxide better improves the interfacial compatibility between LLZO and lithium metal electrodes. Compared to Ga₂O₃ and Ta₂O₃, zinc oxide-doped LLZO more easily forms a stable interfacial layer after contacting lithium metal, which helps reduce interfacial impedance. Interfacial energy: The interfacial energy between zinc oxide and electrode materials (such as LiCoO₂) may be low, which is conducive to forming a stable interface and reducing interfacial impedance.

[0063] From a cost perspective, zinc oxide is cheaper and more readily available than gallium oxide and tantalum oxide. This gives zinc oxide an economic advantage in large-scale production and applications, especially when considering cost-effectiveness. On the other hand, zinc oxide is a relatively environmentally friendly material and produces fewer byproducts during processing, which helps reduce the environmental impact of production. In contrast, certain dopants (such as tantalum oxide) may impose a higher environmental burden during production.

[0064] Zinc oxide, as a second-phase particle, can strengthen the LLZO matrix, improving the material's strength and toughness. Zinc oxide particles can also inhibit crack propagation, enhancing the material's fracture toughness.

[0065] Charge compensation: The introduction of zinc oxide can provide additional positive charge to compensate for the charge imbalance caused by lithium ion desorption and stabilize the structure of the material.

[0066] In summary, the addition of zinc oxide to modify LLZO offers numerous advantages, including increased ionic conductivity, improved mechanical properties, reduced interfacial impedance, suppression of side reactions, and reduced costs. These advantages make LLZO-ZnO composites promising for applications in solid-state batteries. The advantages of zinc oxide doping in LLZO are mainly reflected in the following aspects: improved mechanical properties: enhancing the strength and toughness of the material; improved interfacial compatibility: reducing interfacial impedance and improving battery performance.

[0067] The advantage of this invention lies in the addition of zinc oxide and gallium oxide to the lithium lanthanum zirconium oxide. Zinc oxide offers numerous advantages for modifying LLZO, including increased ionic conductivity, improved mechanical properties, reduced interfacial impedance, suppression of side reactions, and lower costs. These advantages make LLZO-ZnO composite materials promising for applications in solid-state batteries.

[0068] In summary, the human-centered and considerate design of this invention is highly suitable for practical needs. Its specific improvements over existing technologies demonstrate a significant breakthrough and superior performance compared to existing technologies, resulting in substantial efficiency gains that are not easily achieved. The above detailed description pertains to a specific embodiment of this invention; however, this embodiment is not intended to limit the scope of the invention. All equivalent implementations or modifications that do not depart from the technical features of this invention should be included within the scope of protection of this invention.

Claims

1. A lithium lanthanum zirconium oxide doped with gallium and zinc, characterized in that, The forming method is: putting lithium carbonate powder, lanthanum oxide powder, zirconium dioxide powder, gallium oxide powder, and zinc oxide powder into an emulsifier for mixing to make uniform mixed powder; then putting the mixed powder into a wet grinder for grinding to obtain a plurality of mixed powder; then putting the plurality of mixed powder into an oven for drying to remove moisture to obtain a plurality of block-shaped mixture, then putting the plurality of block-shaped mixture into a grinding bowl for grinding treatment to form a plurality of mixed powder; then putting the plurality of mixed powder into a sintering furnace for two-stage gas injection sintering treatment, in the first stage, the sintering temperature is raised from room temperature to 800-900°C, and the sintering furnace is injected with dilute oxygen gas; in the second stage, the original injected dilute oxygen gas is replaced with pure oxygen injected into the sintering furnace, and the sintering process is completed at 800-900°C to obtain the gallium and zinc doped lithium lanthanum zirconium oxide; during the sintering process, gallium and zinc in the gallium oxide and the zinc oxide enter the original lithium lanthanum zirconium oxide to partially replace lithium and zirconium therein; and the gallium and zinc doped lithium lanthanum zirconium oxide is formed; wherein the dilute oxygen gas refers to the proportion of oxygen in the entire gas being less than 30%.

2. The gallium and zinc doped lithium lanthanum zirconium oxide of claim 1, wherein, The chemical formula of the gallium and zinc doped lithium lanthanum zirconium oxide is: Li 7-a La3Zr 1.7-x Ga y Zn z O 12 ; 2x+3y+2z=a, a>0, x>0, y>0, z>0.

3. The gallium and zinc doped lithium lanthanum zirconium oxide of claim 1, wherein, The weight percentage of the lithium carbonate powder is between 20%-25%; the weight percentage of the lanthanum oxide powder is between 40%-45%; the weight percentage of the zirconium dioxide powder is between 20%-25%; the weight percentage of the gallium oxide powder is between 3%-5%; and the weight percentage of the zinc oxide powder is between 3%-5%.

4. The gallium and zinc doped lithium lanthanum zirconium oxide of claim 1, wherein, The grinding time in the wet grinder is 2 hours, and the size of the ground powder is less than 1 micron; wherein the wet grinder also includes pure water as a medium; the weight ratio of the pure water to the mixed powder is 8:

2.

5. The gallium and zinc doped lithium lanthanum zirconium oxide of claim 1, wherein, When the oven is drying, the temperature of the oven is 80±5°C, and the drying time is 3-4 hours.

6. The gallium and zinc doped lithium lanthanum zirconium oxide of claim 1, wherein, In the first stage, the temperature is raised at a rate of 2°C / min.

7. The gallium and zinc doped lithium lanthanum zirconium oxide of claim 1, wherein, The dilute oxygen gas is air.

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