Composite oxide, method for producing the same, positive electrode additive, positive electrode, and lithium ion battery
By preparing the composite oxide Li7La3Zr2-1.25xNbxO12·nLi2ZrO3 as a positive electrode additive for lithium-ion batteries, the problem of instability of lithium lanthanum zirconium oxide in air was solved, the capacity retention rate of the battery was improved, and it is suitable for lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YIBIN NANMU NANO TECH CO LTD
- Filing Date
- 2022-12-29
- Publication Date
- 2026-05-29
AI Technical Summary
The low capacity retention rate of existing lithium-ion batteries hinders their widespread application.
By using the composite oxide Li7La3Zr2-1.25xNbxO12·nLi2ZrO3 as the positive electrode additive, and chemically combining it with lithium zirconate material, the problem of increased resistance caused by the surface instability of lithium lanthanum zirconium oxide in air was solved, thus improving the electrochemical performance.
It improves the capacity retention of lithium-ion batteries, making them suitable for a wide range of applications.
Smart Images
Figure CN116031378B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a composite oxide and its preparation method, a cathode additive, a cathode, and a lithium-ion battery. Background Technology
[0002] Lithium-ion batteries are green rechargeable batteries with high energy density, high output voltage, and excellent cycle performance. They are mainly composed of positive electrode materials, negative electrode materials, separators, and electrolytes. Among these, the positive electrode material has the highest content and proportion, and has the greatest impact on the electrochemical performance of lithium-ion batteries. Therefore, improving the electrochemical performance of the positive electrode material is one of the important methods to improve the energy density and specific capacity of lithium-ion batteries.
[0003] Lithium zirconate is a fast lithium-ion conductor with high ionic conductivity and has been used to improve the electrochemical performance of battery cathode materials. Lithium zirconate is typically coated with transition metal oxides to prepare cathode materials for lithium-ion batteries; however, the capacity retention of lithium-ion batteries obtained using this method is still not high, hindering its widespread application. Summary of the Invention
[0004] Therefore, it is necessary to provide a composite oxide and its preparation method, a cathode additive, a cathode, and a lithium-ion battery to address the issue of how to improve the capacity retention of lithium-ion batteries.
[0005] A composite oxide, the chemical formula of which is Li7La3Zr 2-1.25x Nb x O 12 ·nLi₂ZrO₃, where 0.1≤x≤0.4, 2%≤n≤6%.
[0006] The composite oxide of the present invention, while maintaining the excellent properties of lithium lanthanum zirconium oxide, achieves superior electrochemical performance by chemically combining it with lithium zirconate. Furthermore, it solves the problem of the unstable surface layer of lithium lanthanum zirconium oxide in air, which leads to the formation of a lithium carbonate layer with increased resistivity. Experimental verification shows that when used as a cathode additive in lithium-ion batteries, the above-mentioned composite oxide can improve the capacity retention rate of lithium-ion batteries, which is beneficial for its widespread application.
[0007] In one feasible implementation, the pH of the composite oxide is 10 to 12.
[0008] A method for preparing the above-mentioned composite oxide includes the following steps:
[0009] Used to prepare Li7La3Zr 2-1.25x Nb x O 12The lithium source, zirconium source, lanthanum source and niobium source are mixed evenly and then sintered to obtain lithium lanthanum zirconium oxygen powder;
[0010] The lithium lanthanum zirconium oxide powder was mixed uniformly with a zirconium source and a lithium source used to prepare Li₂ZrO₃ to obtain a mixture; and
[0011] The mixture is subjected to solid-state sintering at a temperature of 900℃~1000℃, and after sufficient reaction, a composite oxide is obtained.
[0012] The preparation method of the composite oxide in the above-mentioned technical solution of the present invention is simple and conducive to mass production. The chemical reaction of zirconium and lithium sources generates lithium zirconate combined with lithium lanthanum zirconium oxide, making the combination more stable and preventing the formation of other phases. This better preserves the chemical properties of both components, achieving a synergistic optimization effect. Experimental verification shows that the composite oxide obtained by the above preparation method, when used as a cathode additive in lithium-ion batteries, can improve the capacity retention rate of lithium-ion batteries, which is beneficial for widespread application.
[0013] In one feasible implementation, Li7La3Zr is used to prepare... 2-1.25x Nb x O 12 The molar ratios of lithium in the lithium source, lanthanum in the lanthanum source, zirconium in the zirconium source, and niobium in the niobium source are 7:3:(1.5–1.875):(0.1–0.4); and / or
[0014] Used to prepare Li7La3Zr 2-1.25x Nb x O 12 In the process of sintering after uniformly mixing lithium, zirconium, lanthanum and niobium sources, the sintering temperature is 1000℃~1200℃, and cubic phase lithium lanthanum zirconium oxide powder is obtained after sintering.
[0015] In one feasible implementation, the molar ratio of zirconium in the zirconium source to lithium in the lithium source used to prepare Li₂ZrO₃ is 1:(1-2); and / or
[0016] In the process of uniformly mixing the lithium lanthanum zirconium oxide powder with the zirconium source and lithium source used to prepare Li2ZrO3: ball milling is performed using a ball mill with a rotation speed of 150 rpm to 275 rpm and a ball milling time of 2 h to 20 h.
[0017] In one feasible implementation, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium nitrate and lithium acetate;
[0018] The lanthanum source is selected from at least one of lanthanum oxide, lanthanum hydroxide, and lanthanum nitrate.
[0019] The zirconium source is zirconium oxide;
[0020] The niobium source is niobium oxide.
[0021] In one feasible implementation, the mixture is subjected to solid-state sintering for 5 to 20 hours, and the solid-state sintering is followed by a step of crushing the sintered product.
[0022] A positive electrode additive comprising the aforementioned composite oxide.
[0023] When the cathode additive of the present invention is used in the cathode of a lithium-ion battery, it can improve the capacity retention rate of the lithium-ion battery, which is beneficial for its widespread application.
[0024] A positive electrode, comprising the aforementioned positive electrode additive.
[0025] The positive electrode of this invention can improve the capacity retention rate of lithium-ion batteries, which is beneficial for their widespread application.
[0026] A lithium-ion battery comprising the aforementioned positive electrode.
[0027] The lithium-ion battery of this invention has a high capacity retention rate, which is beneficial for its widespread application. Attached Figure Description
[0028] Figure 1 This is a flowchart of a method for preparing a composite oxide according to an embodiment of the present invention;
[0029] Figure 2 The images show the XRD patterns of the composite oxides from Examples 1 to 4.
[0030] Figure 3 The image shows the XRD pattern of the composite oxide from Example 1.
[0031] Figure 4 The charge-discharge specific capacity test charts show the composite oxides prepared in Examples 1-4 and the lithium lanthanum zirconium oxide material prepared in Comparative Example 1 as positive electrode additives. Detailed Implementation
[0032] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.
[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0034] The chemical formula of the composite oxide in one embodiment is Li7La3Zr. 2-1.25x Nb x O 12 ·nLi₂ZrO₃, where 0.1≤x≤0.4, 2%≤n≤6%. Here, n refers to the ratio of Li₂ZrO₃ to Li₇La₃Zr. 2-1.25x Nb x O 12 The mass ratio.
[0035] Based on the aforementioned embodiments, the pH of the composite oxide is 10-12. Specifically, the pH of the composite oxide is obtained by dissolving 1 part by mass of the composite oxide in 10 parts by mass of pure water and testing the pH value of the solution.
[0036] Tests have shown that the composite oxides of any of the above embodiments conform to standard card numbers PDF80-1251 and PDF75-2157.
[0037] The composite oxide of the present invention, while maintaining the excellent properties of lithium lanthanum zirconium oxide, achieves superior electrochemical performance by chemically combining it with lithium zirconate. Furthermore, it solves the problem of the unstable surface layer of lithium lanthanum zirconium oxide in air, which leads to the formation of a lithium carbonate layer with increased resistivity. Experimental verification shows that when used as a cathode additive in lithium-ion batteries, the above-mentioned composite oxide can improve the capacity retention rate of lithium-ion batteries, which is beneficial for its widespread application.
[0038] Please see Figure 1 One embodiment of the method for preparing a composite oxide includes the following steps:
[0039] S10, to be used in the preparation of Li7La3Zr 2-1.25x Nb x O 12 The lithium source, zirconium source, lanthanum source and niobium source are mixed evenly and then sintered to obtain lithium lanthanum zirconium oxide powder.
[0040] In one feasible implementation, Li7La3Zr is used to prepare... 2-1.25x Nb x O 12The molar ratio of lithium in the lithium source, lanthanum in the lanthanum source, zirconium in the zirconium source, and niobium in the niobium source is 7:3:(1.5~1.875):(0.1~0.4).
[0041] In one feasible implementation, it will be used to prepare Li7La3Zr 2-1.25x Nb x O 12 In the process of sintering after uniformly mixing lithium, zirconium, lanthanum and niobium sources, the sintering temperature is 1000℃~1200℃, and cubic phase lithium lanthanum zirconium oxide powder is obtained after sintering.
[0042] In one feasible implementation, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate.
[0043] In one feasible implementation, the lanthanum source is selected from at least one of lanthanum oxide, lanthanum hydroxide, and lanthanum nitrate.
[0044] In one feasible implementation, the zirconium source is zirconium oxide.
[0045] In one feasible implementation, the niobium source is niobium oxide.
[0046] In step S10, the lithium lanthanum zirconium oxide material obtained after sintering can be further pulverized by a disc air jet mill to obtain lithium lanthanum zirconium oxide powder with an average particle size of 3 to 5 micrometers.
[0047] S20. The lithium lanthanum zirconium oxide powder obtained in step S10 is mixed evenly with the zirconium source and lithium source used to prepare Li2ZrO3 to obtain a mixture.
[0048] In one feasible implementation, the molar ratio of zirconium in the zirconium source to lithium in the lithium source used to prepare Li2ZrO3 is 1:(1-2).
[0049] In one feasible implementation, the lithium source used to prepare Li₂ZrO₃ is in excess by 2wt% to 5wt%. This prevents the volatilization of the lithium source at high temperatures from causing an imbalance in the chemical composition and the generation of other impurities, thereby avoiding any impact on the electrochemical performance of the resulting material.
[0050] In one feasible implementation, the process of uniformly mixing lithium lanthanum zirconium oxide powder with zirconium and lithium sources used to prepare Li2ZrO3 involves ball milling the powder using a ball mill at a speed of 150 rpm to 275 rpm for 2 h to 20 h.
[0051] In one feasible implementation, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate.
[0052] In one feasible implementation, the zirconium source is zirconium oxide.
[0053] S30. The mixture obtained in step S20 is subjected to solid-state sintering at a temperature of 900℃~1000℃. After the reaction is complete, a composite oxide is obtained.
[0054] In step S30, after solid-state sintering of the lithium mixture, the zirconium and lithium sources used to prepare Li2ZrO3 react on the surface of the lithium lanthanum zirconium oxide powder to obtain Li2ZrO3, and simultaneously form a composite oxide with the lithium lanthanum zirconium oxide powder. The chemical formula of the composite oxide is Li7La3Zr. 2-1.25x Nb x O 12 •nLi₂ZrO₃, where 0.1≤x≤0.4, 2%≤n≤6%. Lithium zirconate is generated by crystallizing the lithium lanthanum zirconium oxide surface, making the combination of the two more stable and the distribution more uniform.
[0055] In one feasible implementation, the mixture is sintered in the solid state for 5 to 20 hours, followed by a step of crushing the sintered product. The sintered composite is crushed, specifically by primary crushing using a jaw crusher and a roller mill, and then by nano-pulverization using a disc air jet mill to obtain a composite oxide with a particle size of 567 nm.
[0056] The preparation method of the composite oxide in the above-mentioned technical solution of the present invention is simple and conducive to mass production. The chemical reaction of zirconium and lithium sources generates lithium zirconate combined with lithium lanthanum zirconium oxide, making the combination more stable and preventing the formation of other phases. This better preserves the chemical properties of both components, achieving a synergistic optimization effect. Experimental verification shows that the composite oxide obtained by the above preparation method, when used as a cathode additive in lithium-ion batteries, can improve the capacity retention rate of lithium-ion batteries, which is beneficial for widespread application.
[0057] One embodiment of the positive electrode additive includes the aforementioned composite oxide.
[0058] When the cathode additive of the present invention is used in the cathode of a lithium-ion battery, it can improve the capacity retention rate of the lithium-ion battery, which is beneficial for its widespread application.
[0059] One embodiment of the positive electrode includes the above-described positive electrode additive.
[0060] The positive electrode of this invention can improve the capacity retention rate of lithium-ion batteries, which is beneficial for their widespread application.
[0061] One embodiment of the lithium-ion battery includes the above-described positive electrode.
[0062] The lithium-ion battery of this invention has a high capacity retention rate, which is beneficial for its widespread application.
[0063] Referring to the above implementation details, in order to make the technical solution of this application more specific, clear and easy to understand, examples of the technical solution of this application are given below. However, it should be noted that the content to be protected by this application is not limited to the following embodiments 1 to 4.
[0064] Example 1
[0065] Example 1 provides a composite oxide and its preparation method, wherein the chemical formula of the composite oxide is Li7La3Zr. 2-1.25x Nb x O 12 ·nLi₂ZrO₃, where x=0.1, n=2%; the specific preparation method of this composite oxide is as follows:
[0066] Step 1: Based on the chemical formula Li7La3Zr 1.875 Nb 0.1 O 12 Weigh out the lithium source, zirconium source, lanthanum source and niobium source. The lithium source is lithium carbonate (753.6g), the zirconium source is zirconium oxide (277.2g), the lanthanum source is lanthanum oxide (586.0g), and the niobium source is niobium oxide (16.1g).
[0067] The weighed materials were mixed using a mixer, and after uniform mixing, pure cubic phase lithium lanthanum zirconium oxide powder was prepared by solid-state sintering. In this embodiment, the sintering temperature was 1000℃ and the sintering time was 15h. The sintered lithium lanthanum zirconium oxide material was pulverized by a disc air jet mill to obtain lithium lanthanum zirconium oxide powder with an average particle size of 3 to 5 micrometers. The pH of the prepared lithium lanthanum zirconium oxide powder was 11.5.
[0068] Step 2: Based on the chemical formula Li₂ZrO₃, calculate the proportions and weigh 16.1g of zirconium oxide and 9.7g of lithium carbonate, then grind and mix them with the lithium lanthanum zirconium oxide powder prepared in Step 1, with lithium carbonate in 2% excess. The mixing method is ball milling, which ensures that the lithium lanthanum zirconium oxide powder and the raw material for preparing lithium zirconate are thoroughly ground and mixed to obtain a homogeneous mixture. The rotation speed of the ball mill jar is 300 rpm (equivalent to a ball mill speed of 150 rpm), and the ball milling time is 2 hours.
[0069] Step 3: The well-mixed mixture is subjected to solid-state sintering at a temperature of 900℃ for 5 hours to obtain the sintered product.
[0070] Step 4: The obtained sintered product is crushed to obtain the composite oxide of lithium lanthanum zirconium oxide and lithium zirconate of Example 1.
[0071] XRD analysis was performed on the composite oxide of Example 1, such as... Figure 1 and Figure 2 As shown, the diffraction peaks of this composite oxide conform to those of lithium lanthanum zirconium oxide and lithium zirconate, with no other impurity phases present. The lithium lanthanum zirconium oxide diffraction peaks conform to standard card number PDF80-1251, indicating a cubic phase lithium lanthanum zirconium oxide material; the lithium zirconate diffraction peaks conform to standard card number PDF75-2157. This demonstrates that the product of Example 1 is a composite oxide of lithium lanthanum zirconium oxide and lithium zirconate.
[0072] Example 2
[0073] Example 2 provides a composite oxide and its preparation method, wherein the chemical formula of the composite oxide is Li7La3Zr. 2-1.25x Nb x O 12 ·nLi₂ZrO₃, where x=0.2, n=3%; the specific preparation method of this composite oxide is as follows:
[0074] Step 1: Based on the chemical formula Li7La3Zr 1.75 Nb 0.2 O 12 Weigh out the lithium source, zirconium source, lanthanum source and niobium source. The lithium source is lithium hydroxide (843.6g), the zirconium source is zirconium oxide (277.2g), the lanthanum source is lanthanum hydroxide (723.8g), and the niobium source is niobium oxide (17.3g).
[0075] The weighed materials were mixed using a mixer, and after uniform mixing, pure cubic phase lithium lanthanum zirconium oxide powder was prepared by solid-state sintering. In this embodiment, the sintering temperature was 1000℃ and the sintering time was 20h. The sintered lithium lanthanum zirconium oxide material was pulverized by a disc air jet mill to obtain lithium lanthanum zirconium oxide powder with an average particle size of 3 to 5 micrometers. The pH of the prepared lithium lanthanum zirconium oxide powder was 11.6.
[0076] Step 2: Based on the chemical formula Li₂ZrO₃, calculate the proportions and weigh out 23.5g of zirconium oxide and 16.3g of lithium hydroxide, with a 3% excess of lithium hydroxide. Grind and mix these with the lithium lanthanum zirconium oxide powder prepared in Step 1. The mixing method is ball milling. Ball milling ensures thorough grinding and mixing of the lithium lanthanum zirconium oxide powder with the raw material for preparing lithium zirconate, resulting in a homogeneous mixture. The ball mill jar rotates at 400 rpm (equivalent to a ball mill speed of 200 rpm), and the milling time is 10 hours.
[0077] Step 3: The well-mixed mixture is subjected to solid-state sintering at a temperature of 900℃ for 20 hours to obtain the sintered product.
[0078] Step 4: The obtained sintered product is crushed to obtain the composite oxide of lithium lanthanum zirconium oxide and lithium zirconate of Example 2. The particle size of the composite oxide is 532 nm.
[0079] XRD analysis was performed on the composite oxide of Example 2, such as... Figure 1 As shown, the diffraction peaks of the composite oxide match those of lithium lanthanum zirconium oxide and lithium zirconate, and no other impurity phases are generated, indicating that the product of Example 2 is a composite oxide of lithium lanthanum zirconium oxide and lithium zirconate.
[0080] Example 3
[0081] Example 2 provides a composite oxide and its preparation method, wherein the chemical formula of the composite oxide is Li7La3Zr. 2-1.25x Nb x O 12 ·nLi₂ZrO₃, where x=0.3, n=4%; the specific preparation method of this composite oxide is as follows:
[0082] Step 1: Based on the chemical formula Li7La3Zr 1.625 Nb 0.3 O 12 Weigh out the lithium source, zirconium source, lanthanum source and niobium source. The lithium source is lithium nitrate (648.6g), the zirconium source is zirconium oxide (167.2g), the lanthanum source is lanthanum nitrate (863.5g) and the niobium source is niobium oxide (23.8g).
[0083] The weighed materials were mixed using a mixer, and after uniform mixing, pure cubic phase lithium lanthanum zirconium oxide powder was prepared by solid-state sintering. In this embodiment, the sintering temperature was 1100℃ and the sintering time was 20h. The sintered lithium lanthanum zirconium oxide material was pulverized by a disc air jet mill to obtain lithium lanthanum zirconium oxide powder with an average particle size of 3 to 5 micrometers. The pH of the prepared lithium lanthanum zirconium oxide powder was 11.8.
[0084] Step 2: Based on the chemical formula Li₂ZrO₃, calculate the proportions and weigh out 35.6g of zirconium oxide and 21.4g of lithium nitrate, with a 3% excess of lithium nitrate. Grind and mix these with the lithium lanthanum zirconium oxide powder prepared in Step 1. The mixing method is ball milling. Ball milling ensures thorough grinding and mixing of the lithium lanthanum zirconium oxide powder with the raw material for preparing lithium zirconate, resulting in a homogeneous mixture. The ball mill jar rotates at 500 rpm (equivalent to a ball mill speed of 250 rpm), and the milling time is 15 hours.
[0085] Step 3: The well-mixed mixture is subjected to solid-state sintering at a temperature of 1000℃ for 5 hours to obtain the sintered product.
[0086] Step 4: The obtained sintered product is crushed to obtain the composite oxide of lithium lanthanum zirconium oxide and lithium zirconate of Example 3. The particle size of the obtained composite oxide is 436 nm.
[0087] XRD analysis was performed on the composite oxide of Example 3, such as... Figure 1 As shown, the diffraction peaks of the composite oxide match those of lithium lanthanum zirconium oxide and lithium zirconate, and no other impurity phases are generated, indicating that the product of Example 3 is a composite oxide of lithium lanthanum zirconium oxide and lithium zirconate.
[0088] Example 4
[0089] Example 2 provides a composite oxide and its preparation method, wherein the chemical formula of the composite oxide is Li7La3Zr. 2-1.25x Nb x O 12 ·nLi₂ZrO₃, where x=0.4, n=6%; the specific preparation method of this composite oxide is as follows:
[0090] Step 1: Based on the chemical formula Li7La3Zr 1.5 Nb 0.4 O 12 Weigh out the lithium source, zirconium source, lanthanum source and niobium source. The lithium source is lithium carbonate (763.5g), the zirconium source is zirconium oxide (253.4g), the lanthanum source is lanthanum oxide (863.4g), and the niobium source is niobium oxide (42.1g).
[0091] The weighed materials were mixed using a mixer, and after uniform mixing, pure cubic phase lithium lanthanum zirconium oxide powder was prepared by solid-state sintering. In this embodiment, the sintering temperature was 1200℃ and the sintering time was 24h. The sintered lithium lanthanum zirconium oxide material was pulverized by a disc air jet mill to obtain lithium lanthanum zirconium oxide powder with an average particle size of 3 to 5 micrometers. The pH of the prepared lithium lanthanum zirconium oxide powder was 12.1.
[0092] Step 2: Based on the chemical formula Li₂ZrO₃, calculate the proportions and weigh out 35.6g of zirconium oxide and 21.4g of lithium carbonate, with a 3% excess of lithium carbonate. Grind and mix these with the lithium lanthanum zirconium oxide powder prepared in Step 1. The mixing method is ball milling. Ball milling ensures thorough grinding and mixing of the lithium lanthanum zirconium oxide powder with the raw material for preparing lithium zirconate, resulting in a homogeneous mixture. The ball mill jar rotates at 550 rpm (equivalent to a ball mill speed of 275 rpm), and the milling time is 20 hours.
[0093] Step 3: The well-mixed mixture is subjected to solid-state sintering at a temperature of 1000℃ for 20 hours to obtain the sintered product.
[0094] Step 4: The obtained sintered product is crushed to obtain the composite oxide of lithium lanthanum zirconium oxide and lithium zirconate of Example 4. The particle size of the composite oxide is 438 nm.
[0095] XRD analysis was performed on the composite oxide of Example 4, such as... Figure 1 As shown, the diffraction peaks of the composite oxide match those of lithium lanthanum zirconium oxide and lithium zirconate, and no other impurity phases are generated, indicating that the product of Example 4 is a composite oxide of lithium lanthanum zirconium oxide and lithium zirconate.
[0096] Comparative Example 1
[0097] Comparative Example 1 provides a lithium lanthanum zirconium oxide material and its preparation method, with the chemical formula: Li7La3Zr 1.5 Nb 0.4 O 12 The specific preparation method is as follows:
[0098] Step 1: Based on the chemical formula Li7La3Zr 1.5 Nb 0.4 O 12 Weigh out the lithium source, zirconium source, lanthanum source and niobium source. The lithium source is lithium carbonate (763.5g), the zirconium source is zirconium oxide (253.4g), the lanthanum source is lanthanum oxide (863.4g), and the niobium source is niobium oxide (42.1g).
[0099] The weighed materials are mixed using a mixer, which can be a double mixer; the mixing speed is selected as 2000 rpm.
[0100] Step 2: The uniformly mixed materials are sintered in a solid state to obtain a pure cubic phase lithium lanthanum zirconium oxide material; in this comparative example, the sintering temperature is 1200℃ and the sintering time is 30h.
[0101] Step 3: The sintered lithium lanthanum zirconium oxide material is pulverized by a disc air jet mill to obtain lithium lanthanum zirconium oxide powder material with an average particle size of 3 to 5 micrometers.
[0102] Performance testing:
[0103] The composite oxides prepared in Examples 1-4 and the lithium lanthanum zirconium oxide material prepared in Comparative Example 1 were used as positive electrode additives to test their charge-discharge specific capacity and cycle performance. The specific experimental procedure included: using the composite oxides prepared in Examples 1-4 and the lithium lanthanum zirconium oxide material prepared in Comparative Example 1 as battery additives; mixing carbon black and PVDF in a mass ratio of 8:1:1; coating the mixture onto an aluminum foil current collector to form the positive electrode, with a lithium sheet as the negative electrode. At a rate of 1C, the initial discharge specific capacity and capacity retention rate after 100 charge-discharge cycles were tested with a cutoff voltage of 2.5V-4.5V. Figure 4The data shown.
[0104] Depend on Figure 4 It can be seen that the specific capacity of the lithium lanthanum zirconium oxide material without lithium zirconate (i.e., Comparative Example 1) gradually decreases with the increase of charge-discharge cycles; and the decrease is more pronounced with more cycles. However, the specific capacity of the composite oxides prepared in Examples 1-4, after incorporating lithium zirconate, decreases slowly and maintains a high specific capacity. When lithium zirconate accounts for 3% of the lithium lanthanum zirconium oxide, the capacity retention reaches a maximum of 94%. As the lithium zirconate content continues to increase, the specific capacity decreases. Its high capacity retention may be mainly attributed to the electrolyte resistance of lithium zirconate, preventing the lithium lanthanum zirconium oxide from being eroded by the electrolyte and maintaining its high chemical properties; on the other hand, due to… Figure 1 and Figure 2 The XRD pattern also shows that no lithium carbonate phase was formed, indicating that lithium zirconate can prevent the formation of lithium carbonate and affect the high conductivity of lithium lanthanum zirconium oxide.
[0105] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0106] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.
Claims
1. A composite oxide, characterized in that, The chemical formula of the composite oxide is Li7La3Zr. 2-1.25x Nb x O 12 ·nLi₂ZrO₃, where 0.1≤x≤0.4, 2%≤n≤6%; The pH of the composite oxide is 10-12. The pH of the composite oxide is obtained by dissolving 1 part by mass of the composite oxide in 10 parts by mass of pure water and testing the pH value of the solution. The composite oxide was prepared using the following method: Used to prepare Li7La3Zr 2-1.25x Nb x O 12 The lithium source, zirconium source, lanthanum source and niobium source are mixed evenly and then sintered to obtain lithium lanthanum zirconium oxygen powder; The lithium lanthanum zirconium oxide powder was mixed uniformly with a zirconium source and a lithium source used to prepare Li₂ZrO₃ to obtain a mixture; and The mixture was subjected to solid-state sintering at a temperature of 900℃~1000℃, which caused Li2ZrO3 to be generated in situ and chemically bonded on the surface of the lithium lanthanum zirconium oxide powder. After the reaction was complete, a composite oxide was obtained without the formation of lithium carbonate phase.
2. A method for preparing the composite oxide according to claim 1, characterized in that, Includes the following steps: Used to prepare Li7La3Zr 2-1.25x Nb x O 12 The lithium source, zirconium source, lanthanum source and niobium source are mixed evenly and then sintered to obtain lithium lanthanum zirconium oxygen powder; The lithium lanthanum zirconium oxide powder was mixed uniformly with a zirconium source and a lithium source used to prepare Li₂ZrO₃ to obtain a mixture; and The mixture was subjected to solid-state sintering at a temperature of 900℃~1000℃, which caused Li2ZrO3 to be generated in situ and chemically bonded on the surface of the lithium lanthanum zirconium oxide powder. After the reaction was complete, a composite oxide was obtained without the formation of lithium carbonate phase.
3. The method for preparing the composite oxide according to claim 2, characterized in that, Used to prepare Li7La3Zr 2- 1.25x Nb x O 12 The molar ratios of lithium in the lithium source, lanthanum in the lanthanum source, zirconium in the zirconium source, and niobium in the niobium source are 7:3:(1.5~1.875):(0.1~0.4); and / or Used to prepare Li7La3Zr 2-1.25x Nb x O 12 In the process of sintering after uniformly mixing lithium, zirconium, lanthanum and niobium sources, the sintering temperature is 1000℃~1200℃, and cubic phase lithium lanthanum zirconium oxide powder is obtained after sintering.
4. The method for preparing the composite oxide according to claim 2, characterized in that, The molar ratio of zirconium in the zirconium source to lithium in the lithium source used to prepare Li₂ZrO₃ is 1:(1~2); and / or In the process of uniformly mixing the lithium lanthanum zirconium oxide powder with the zirconium source and lithium source used to prepare Li2ZrO3: ball milling is performed using a ball mill with a rotation speed of 150 rpm to 275 rpm and a ball milling time of 2 h to 20 h.
5. The method for preparing the composite oxide according to claim 2, characterized in that, The lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium nitrate and lithium acetate; The lanthanum source is selected from at least one of lanthanum oxide, lanthanum hydroxide, and lanthanum nitrate. The zirconium source is zirconium oxide; The niobium source is niobium oxide.
6. The method for preparing the composite oxide according to claim 2, characterized in that, The mixture is subjected to solid-state sintering for 5 to 20 hours. After solid-state sintering, the product obtained by sintering is further subjected to crushing.
7. A positive electrode additive, characterized in that, The composite oxide described in claim 1 is used to improve the capacity retention of lithium-ion batteries.
8. A positive electrode, characterized in that, Includes the positive electrode additive as described in claim 7.
9. A lithium-ion battery, characterized in that, Includes the positive electrode as described in claim 8.