Lithium zirconium phosphate oligomer and preparation method thereof, composite solid electrolyte and solid battery
By molecular-level compositing lithium zirconium phosphate oligomers with PEGx-COOH, the problems of discontinuous ion transport and low conductivity in composite solid electrolytes were solved, achieving efficient lithium-ion migration and large-area thin film preparation, while reducing preparation costs.
Patent Information
- Application Number
- CN202511043646.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-28
- Publication Date
- 2025-12-12
Smart Images
Figure CN121107974A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of batteries, in particular to a lithium zirconium phosphate oligomer, a preparation method thereof, a composite solid electrolyte and a solid-state battery. BACKGROUND
[0002] As the core material of the next generation of high safety lithium batteries, the solid electrolyte needs to have high ionic conductivity (>10 - 4 S / cm), low interfacial impedance and excellent mechanical strength. Although the traditional solid electrolyte (such as LLZO and LATP) has high ionic conductivity, the interface contact is not sufficient due to the rigid crystal structure, resulting in high interface impedance, dendrite growth and other problems. In order to solve the problems of the traditional solid electrolyte, composite solid electrolytes appear. The existing composite solid electrolytes are mostly blended with inorganic fillers (such as SiO2 and Al2O3) and polymers (PEO and PVDF). The following problems exist: 1) the inorganic fillers and the polymer matrix are physically mixed, the interface compatibility is poor, there are micron-sized voids, and the ion transport path is discontinuous; 2) the inorganic fillers have low dielectric constant (dielectric constant <10), which makes it difficult to effectively dissociate the ion pairs of lithium salt, resulting in low concentration of free lithium ions in the system, limiting the improvement of lithium ion mobility, and the ionic conductivity of the composite solid electrolyte is generally lower than 10 -4 S / cm; 3) the uniform dispersion of inorganic fillers needs to rely on high-temperature sintering or high-pressure forming, which is difficult to realize the preparation of large-area and uniform thin films. SUMMARY
[0003] In view of the problems of the existing composite solid electrolyte, such as discontinuous ion transport path, low ionic conductivity and difficulty in realizing the preparation of large-area and uniform thin films, the present application provides a lithium zirconium phosphate oligomer, a preparation method thereof, a composite solid electrolyte and a solid-state battery.
[0004] In the first aspect, the present application provides a lithium zirconium phosphate oligomer, the structural general formula of the lithium zirconium phosphate oligomer is a compound shown in formula 1, [LiZr2(PO4)3] m [PEG x COO] n Formula 1, wherein m is 1, n is 0.5-8, x is 1-10.
[0005] Preferably, the D50 particle size of the lithium zirconium phosphate oligomer is 2-1000 nm.
[0006] In the second aspect, the present application provides a preparation method of the above-mentioned lithium zirconium phosphate oligomer, comprising the following steps: mixing the lithium source, the zirconium source and the first solvent to obtain a first mixed system, adding a first compound to the first mixed system to form a gel, adding a phosphorus source to the gel, and performing a first post-treatment to obtain zirconium lithium phosphate oligomer particles; mixing the zirconium lithium phosphate oligomer particles with a second solvent, adding PEG x -COOH, stirring at 25-35°C for 1-5h, and performing a second post-treatment after the stirring to obtain the zirconium lithium phosphate oligomer; the first compound is a compound shown in formula 2, , formula 2 wherein R1, R2, R3 are each independently selected from at least one of alkyl groups with carbon atom number 1-2; PEG x -COOH is a compound shown in formula 3, and x is 1-10; formula 3.
[0007] Preferably, adding the first compound to the first mixed system to form a gel comprises the following steps: adding the first compound to the first mixed system to obtain a second mixed system with pH value of 5-9 at 10-30°C, and stirring the second mixed system to form a gel, the stirring time being 12-24h.
[0008] Preferably, adding the phosphorus source to the gel and performing the first post-treatment to obtain the zirconium lithium phosphate oligomer particles comprises the following steps: adding the phosphorus source to the gel to obtain a third mixed system, and sequentially performing aging, drying and grinding on the third mixed system to obtain the zirconium lithium phosphate oligomer particles; the aging temperature is 10-30°C, the aging time is 48-72h, and the drying temperature is 60-80°C; the polymerization degree of the zirconium lithium phosphate oligomer particles is 5-10.
[0009] Preferably, the molar ratio of the lithium source, the zirconium source and the phosphorus source is (0.5-1):(1-2):(1-3); the molar ratio of the first compound and the phosphorus source is (500-1):1.
[0010] Preferably, the molar ratio of the zirconium lithium phosphate oligomer particles and the PEG x -COOH is 1:(0.5-8).
[0011] Preferably, the PEG x-COOH, stirring at 25-35 DEG C for 1-5 h, and performing second post-treatment after the stirring is completed to obtain the lithium zirconium phosphate oligomer, including the following steps: adding PEG x -COOH, stirring at 25-35 DEG C for 1-5 h, and performing second post-treatment after the stirring is completed to obtain the lithium zirconium phosphate oligomer, including the following steps: adding PEG The aging temperature is 10-30 DEG C, the aging time is 48-72 h, and the drying temperature is 60-80 DEG C.
[0012] In a third aspect, the present application provides a composite solid electrolyte comprising the lithium zirconium phosphate oligomer described above or the lithium zirconium phosphate oligomer prepared by the preparation method of the lithium zirconium phosphate oligomer described above.
[0013] In a fourth aspect, the present application provides a solid-state battery comprising the composite solid electrolyte described above.
[0014] The lithium zirconium phosphate oligomer provided by the present application has the following effects: 1) the chemical compounding method is used to realize the molecular-level compounding between PEG x -COOH and lithium zirconium phosphate, the PEG x -COOH and lithium zirconium phosphate do not have micron-level gaps, and can form a continuous ion transmission path. 2) The lithium zirconium phosphate oligomer has a high dielectric constant, can effectively dissociate lithium salt ion pairs, increase the concentration of free lithium ions in the battery system, and improve the lithium ion migration rate, so that lithium ions can be effectively conducted, and the ionic conductivity of the composite solid electrolyte is improved. 3) The lithium zirconium phosphate oligomer has good crystal integrity and narrow particle size distribution, and will not agglomerate, so it does not need to rely on high-temperature sintering or high-pressure forming, and can realize the preparation of large-area and uniform thin films. BRIEF DESCRIPTION OF DRAWINGS
[0015] Figure 1 The SEM test result graph (4k magnification) of the lithium zirconium phosphate oligomer prepared for Example 1 is shown in the following figure: Figure 2 The SEM test result graph (100k magnification) of the lithium zirconium phosphate oligomer prepared for Example 1 is shown in the following figure: Figure 3 The dynamic light scattering graphs of different molar ratios of triethylamine (TEA) and phosphoric acid (H3PO4) are shown in the following figures. DETAILED DESCRIPTION
[0016] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application.
[0017] To illustrate the technical solution of the present invention, specific embodiments are described below.
[0018] In one embodiment of the present invention, this application provides a lithium zirconium phosphate oligomer, wherein the general structural formula of the lithium zirconium phosphate oligomer is the compound shown in Formula 1. [LiZr2(PO4)3] m [(PEG) x COO] n Equation 1, where m is 1, n is 0.5~8, and x is 1~10.
[0019] Specifically, PEG x The structure of -COOH is One of the components is a polyethylene glycol with a carboxyl group at one end and x repeating -CH2-CH2-O- units. PEG in lithium zirconium phosphate oligomers x -COO - With zirconium ions (Zr 4+ A stable complex is formed to obtain lithium zirconium phosphate oligomers with the general structure shown in Formula 1.
[0020] Compared to existing solid electrolytes, the lithium zirconium phosphate oligomer provided in this application has the following advantages: 1) PEG is achieved through chemical composite method. x Molecular-level composite between -COOH and lithium zirconium phosphate, PEG x 1) There are no micron-sized gaps between -COOH and lithium zirconium phosphate, enabling the formation of continuous ion transport pathways. 2) The lithium zirconium phosphate oligomers contain high dielectric constants, which can effectively dissociate lithium salt ion pairs, increase the concentration of free lithium ions in the battery system, improve lithium ion mobility, effectively conduct lithium ions, and improve the ionic conductivity of the composite solid electrolyte. 3) The lithium zirconium phosphate oligomers have good crystal integrity, narrow particle size distribution, and do not agglomerate. They do not require high-temperature sintering or high-pressure molding, and can achieve the preparation of large-area, uniform thin films.
[0021] In some embodiments, the D50 particle size range of the lithium zirconium phosphate oligomer is 2~1000 nm.
[0022] Specifically, lithium zirconium phosphate oligomers have a narrow particle size distribution range, with ultrafine nanoclusters whose particle size is controllable and does not agglomerate, enabling the preparation of large-area, uniform thin films. The D50 particle size range of lithium zirconium phosphate oligomers can be 2~100nm, 100~200nm, 200~300nm, 300~400nm, 400~500nm, 500~600nm, 600~800nm, 800~900nm, or 900~1000nm.
[0023] In some preferred embodiments, the D50 particle size range of the lithium zirconium phosphate oligomer is 2~200 nm.
[0024] The D50 particle size range of lithium zirconium phosphate oligomers can be 2~50nm, 50~80nm, 80~100nm, 100~130nm, 130~150nm, 150~180nm or 180~200nm.
[0025] Secondly, this application provides a method for preparing the above-mentioned lithium zirconium phosphate oligomer, comprising the following steps: A first mixed system is obtained by uniformly mixing a lithium source, a zirconium source, and a first solvent. A first compound is added to the first mixed system to form a gel. A phosphorus source is added to the gel, and a first post-treatment is performed to obtain lithium zirconium phosphate oligomer particles. The lithium zirconium phosphate oligomer particles were mixed evenly with the second solvent, and PEG was added. x -COOH, stirred at 25℃~35℃ for 1~5h, and after stirring, a second post-treatment was performed to obtain the lithium zirconium phosphate oligomer; The first compound is the compound shown in Formula 2. , Formula 2 R1, R2, and R3 are each independently selected from at least one of H and alkyl groups having 1 to 2 carbon atoms; PEG x -COOH is the compound shown in Formula 3, where x is 1~10; Formula 3.
[0026] Among them, PEG x The -COOH group represents polyethylene glycol with a carboxyl group at one end and x repeating -CH2-CH2-O- units. Specifically, the first compound exhibits coordination-induced oligomerization, meaning it can react with zirconium ions (Zr). 4 + This forms a stable Zr(OH)4 complex, inhibiting the continuous growth of Zr(OH)4 cluster size. After adding a phosphorus source to the gel, HPO4... 2- It binds more readily to triethylamine, promoting the directional growth of Zr-OPO-Zr chain oligomer structures, thereby allowing control over the size of lithium zirconium phosphate particles. Adding PEG... x -COOH, where -COOH replaces the first compound position in the lithium zirconium phosphate oligomer, making PEG x -COO - With zirconium ions (Zr 4+ A stable complex is formed, thereby preparing lithium zirconium phosphate oligomers.
[0027] Add PEG x -COOH, stirred at 25℃~35℃ for 1~5h, PEG x -COOH is mixed evenly with lithium zirconium phosphate oligomer to facilitate PEG x -COOH replaces the first compound position in lithium zirconium phosphate oligomers, making PEG x -COO - With zirconium ions (Zr 4+ A stable complex was formed, and lithium zirconium phosphate oligomers were prepared.
[0028] The preparation method of lithium zirconium phosphate oligomers provided in this application has the following advantages: 1) It is prepared by sol-gel method, which does not require high-temperature sintering or high-pressure molding, and the preparation process is simple and low-cost; 2) The preparation method provided in this application can realize molecular-level composite between inorganic and organic materials, and can form a continuous ion transport path. The resulting lithium zirconium phosphate oligomers have good crystal integrity, narrow particle size distribution, and form ultrafine nanoclusters without agglomeration, which can realize the preparation of large-area and uniform films; 3) The lithium zirconium phosphate oligomers contain high dielectric constant, which can effectively dissociate lithium salt ion pairs, increase the concentration of free lithium ions in the battery system, increase lithium ion mobility, effectively conduct lithium ions, and improve the ionic conductivity of composite solid electrolyte.
[0029] In some preferred embodiments, R1, R2, and R3 are each independently selected from ethyl groups.
[0030] In some embodiments, the lithium source, zirconium source and first solvent are mixed uniformly to obtain a first mixed system, including the following steps: dissolving the lithium source and zirconium source in the first solvent, stirring at 10~30°C for 2~4 hours, and mixing uniformly to obtain the first mixed system.
[0031] Specifically, the zirconium source dissolves in the first solvent to form zirconium ions. After the addition of the first compound, the first compound complexes with the zirconium ions, inhibiting the continued growth of Zr(OH)₄ clusters, resulting in a first mixed system containing zirconium ions. Stirring for 2-4 hours promotes the dissolution of the zirconium source, allowing Zr… 4+ Disperse evenly.
[0032] The first solvent includes alcohol solvents. Alcohol solvents include ethanol solvents.
[0033] In some embodiments, adding a first compound to the first mixture to form a gel includes the following steps: At 10~30℃, the first compound is added to the first mixture to obtain a second mixture with a pH of 5~9. The second mixture is stirred to form a gel for 12~24h.
[0034] Specifically, a first compound is added to the first mixed system. The first compound can form a stable complex with tetravalent zirconium ions, thereby inhibiting the continuous growth of Zr(OH)4 cluster size.
[0035] The first compound is alkaline and its pH can be adjusted to obtain a second mixture with a pH of 5-9. The second mixture is then stirred, causing it to gel. Adjusting the pH to the range of 5-9 facilitates the complexation of the first compound with zirconium ions, forming a colloid containing lithium zirconium hydroxide. Some of the colloid particles dissolve in ethanol to form a gel.
[0036] The stirring time can be 12h, 13h, 14h, 15h, 16h, 18h, 19h, 20h, 22h, 23h, 24h, etc.
[0037] In some preferred embodiments, the pH of the second mixing system is 7.5 to 8.5, and the D50 particle size range of the prepared lithium zirconium phosphate oligomer is 2 to 200 nm.
[0038] In some embodiments, adding a phosphorus source to the gel and performing a first post-treatment to obtain lithium zirconium phosphate oligomers includes the following steps: adding a phosphorus source to the gel to obtain a third mixed system, and sequentially aging, drying, and grinding to obtain the lithium zirconium phosphate oligomer particles; The aging temperature is 10~30℃, and the aging time is 48~72h; The drying temperature is 60~80℃; the degree of polymerization of the lithium zirconium phosphate oligomer particles is 5~10.
[0039] Specifically, after adding a phosphorus source to the gel, the gel partially dissolves, resulting in a third mixed system. Aging this third mixed system promotes the directional growth of Zr-OPO-Zr chain oligomer structures, forming lithium zirconium phosphate oligomers (LZP). Aging times can be 48h, 50h, 52h, 55h, 57h, 59h, 60h, 62h, 65h, 68h, 70h, and 72h. Drying temperatures can be 60℃, 62℃, 65℃, 67℃, 68℃, 69℃, 70℃, 72℃, 75℃, 79℃, and 80℃.
[0040] The preparation method provided in this application yields lithium zirconium phosphate oligomer particles with a degree of polymerization of 5-10, which is low and mainly occurs through Zr. 4+ and PO4 3- A chain-like oligomeric structure is formed, consisting of a Zr-OPO-Zr structure.
[0041] In some embodiments, the molar ratio of the lithium source, zirconium source, and phosphorus source is (0.5~1):(1~2):(1~3). The molar ratio of the first compound to the phosphorus source is (500~1):1.
[0042] Specifically, the particle size of the lithium zirconium phosphate oligomer particles can be controlled by adjusting the molar ratio of the first compound and the phosphorus source. When the molar ratio of the first compound to the phosphorus source is in the range of (500~1):1, the D50 particle size distribution of the resulting lithium zirconium phosphate oligomer particles ranges from 2 to 1000 nm. Specifically, the molar ratio of the first compound to the phosphorus source can be in the following ranges: (500~400): 1, (400~300):1, (300~200):1, (200~100):1, (100~50):1, or (50~1):1.
[0043] In some embodiments, the lithium zirconium phosphate oligomer particles and the PEG x The molar ratio of -COOH is 1:(0.5~8).
[0044] Specifically, controlling the interaction between lithium zirconium phosphate oligomers and PEG x The molar ratio of -COOH is in the range of 1:(0.5~8), which reduces costs while also making PEG... x -COOH forms molecular-level composites with lithium zirconium phosphate oligomers, creating non-aggregating nanoclusters. Specifically, lithium zirconium phosphate oligomers and PEG... x The molar ratio of -COOH can be 1:(0.5~1), 1:(1~2.5), 1:(2.5~4), 1:(4~6) or 1:(6~8).
[0045] If lithium zirconium phosphate oligomer particles and PEG x The molar ratio of -COOH is less than 1:(0.5~8), containing PEG. x Excessive -COOH can lead to PEG x The aggregation of -COOH groups increases the glass transition temperature and blocks the lithium-ion migration pathway. When used as a composite solid electrolyte in batteries, this increases battery impedance and deteriorates cycle performance. Furthermore, the combination of lithium zirconium phosphate oligomer particles and PEG... x When the molar ratio of -COOH is higher than 1:(0.5~8), there are too many lithium zirconium phosphate oligomer particles, the size of lithium zirconium phosphate clusters increases, and they cannot form a complete lithium-ion pathway. When used in batteries, the battery impedance increases and the cycle performance deteriorates.
[0046] In some preferred embodiments, lithium zirconium phosphate oligomers are combined with PEG. x The molar ratio of -COOH is 1:(1~4).
[0047] In some embodiments, PEG is added. x-COOH, stirred at 25℃~35℃ for 1~5h, after stirring, a second post-treatment is performed to obtain the lithium zirconium phosphate oligomer, including the following steps: adding PEG. x -COOH, stirred at 25℃~35℃ for 1~5h, after stirring, a fourth mixed system is obtained. The fourth mixed system is then aged, dried and ground to obtain the lithium zirconium phosphate oligomer particles. The aging temperature is 10~30℃ and the aging time is 48~72h. The drying temperature is 60~80℃.
[0048] Add PEG x -COOH, with the aging time controlled within the range of 48~72h, will replace the first compound position in the lithium zirconium phosphate oligomer, thus enabling PEG... x -COOH and zirconium ions (Zr) 4+ A stable complex is formed, thereby preparing lithium zirconium phosphate oligomers. The aging time can be 48h, 50h, 52h, 55h, 57h, 59h, 60h, 62h, 65h, 68h, 70h, 72h, etc. The drying temperature can be 60℃, 62℃, 65℃, 67℃, 68℃, 69℃, 70℃, 72℃, 75℃, 79℃, 80℃, etc.
[0049] In some embodiments, the lithium source includes one of lithium nitrate, lithium chloride, lithium sulfate, lithium carbonate, and lithium acetate.
[0050] In some embodiments, the zirconium source is selected from one of zirconium nitrate, zirconium sulfate, zirconium carbonate, zirconium acetate, zirconium chloride, and zirconium oxychloride.
[0051] In some embodiments, the phosphorus source is selected from phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.
[0052] In some embodiments, the second solvent includes an alcohol solvent.
[0053] Alcohol solvents include ethanol solvents.
[0054] Thirdly, this application provides a composite solid electrolyte comprising the lithium zirconium phosphate oligomer described above or the lithium zirconium phosphate oligomer prepared by the method described above.
[0055] The composite solid electrolyte provided in this application includes lithium zirconium phosphate oligomer. The prepared composite solid electrolyte is used in solid batteries to improve the ion migration rate of the battery, reduce the impedance of the solid battery, and improve the electrical performance of the solid battery.
[0056] Fourthly, this application provides a solid-state battery, including the composite solid-state electrolyte described above.
[0057] The solid-state battery provided in this application includes the aforementioned composite solid electrolyte, and the lithium zirconium phosphate oligomer contained therein reduces the impedance of the solid-state battery and improves its electrical performance.
[0058] The present invention will be further illustrated by the following examples.
[0059] Example 1 S1: Preparation of lithium zirconium phosphate oligomer particles S11: Obtain raw materials The lithium source is lithium nitrate, the zirconium source is zirconium oxychloride (ZrOCl2·8H2O), and the phosphorus source is phosphoric acid (H3PO4). Both the first and second solvents are ethanol (CH3CH2OH). The first compound is triethylamine (TEA); The molar ratio of lithium source:zirconium source:phosphorus source is 1:2:3.
[0060] S12: Dissolve the zirconium source and lithium source in the first solvent ethanol, and stir at room temperature (10~30℃) for 3 h to obtain the first mixed system.
[0061] S13: Triethylamine was added to the first mixture to adjust the pH to 5, resulting in a second mixture. The second mixture was stirred to form a gel for 18 hours. A phosphorus source was added to the gel, causing partial dissolution and resulting in a third mixture. This third mixture was aged at 10–30°C for 60 hours. After aging, it was dried at 70°C and then ground to obtain lithium zirconium phosphate oligomer particles. The degree of polymerization of the prepared lithium zirconium phosphate oligomer particles was 5–10. The molar ratio of phosphorus source to triethylamine was 1:1. The sol-gel conversion rate was tested to be 80%.
[0062] S2: Preparation of lithium zirconium phosphate oligomers S21: Dissolve the lithium zirconium phosphate oligomer particles prepared in step S13 in ethanol solvent and stir at room temperature (10~30℃) for 3 h to mix evenly.
[0063] S22: Add PEG4-COOH to step S21 and stir at 25℃~35℃ for 1~5h. After stirring, a fourth mixture is obtained. This fourth mixture is aged at room temperature (10~30℃) for 60h. After aging, it is dried at 70℃. After drying, it is ground to obtain lithium zirconium phosphate oligomer. The molar ratio of lithium zirconium phosphate oligomer to PEG4-COOH is 1:0.5. PEG4-COOH is obtained commercially.
[0064] The D50 particle size of the prepared lithium zirconium phosphate oligomer was 900 nm.
[0065] Example 2 Most of the steps in this embodiment are the same as those in Embodiment 1, except that step S13 is different, as detailed below.
[0066] S13: Triethylamine was added to the first mixture to adjust the pH to 6, resulting in a second mixture. The second mixture was stirred to form a gel for 22 hours. A phosphorus source was added to the gel, causing partial dissolution and resulting in a third mixture. This third mixture was aged at 10–30°C for 70 hours. After aging, it was dried at 75°C and then ground to obtain lithium zirconium phosphate oligomer particles. The degree of polymerization of the prepared lithium zirconium phosphate oligomer particles was 5–10. The molar ratio of phosphorus source to triethylamine was 1:50. The sol-gel conversion rate was tested to be 86%.
[0067] In step S22 of Example 2, the molar ratio of the corresponding lithium zirconium phosphate oligomer to PEG4-COOH is 1:0.5. The D50 particle size of the prepared lithium zirconium phosphate oligomer is 500 nm.
[0068] Example 3 Most of the steps in this embodiment are the same as those in Embodiment 1, except that step S13 is different, as detailed below.
[0069] S13: Triethylamine was added to the first mixture to adjust the pH to 8, resulting in a second mixture. The second mixture was stirred to form a gel for 22 hours. A phosphorus source was added to the gel, causing partial dissolution and resulting in a third mixture. This third mixture was aged at 10–30°C for 50 hours. After aging, it was dried at 60°C and then ground to obtain lithium zirconium phosphate oligomer particles. The degree of polymerization of the prepared lithium zirconium phosphate oligomer particles was 5–10. The molar ratio of phosphorus source to triethylamine was 1:100. The sol-gel conversion rate was tested to be 96%.
[0070] In step S22 of Example 3, the molar ratio of the corresponding lithium zirconium phosphate oligomer to PEG4-COOH was 1:0.5. The D50 particle size of the prepared lithium zirconium phosphate oligomer was 80 nm.
[0071] Example 4 Most of the steps in this embodiment are the same as those in Embodiment 1. The difference is that step S13 is different, as detailed below.
[0072] S13: Triethylamine was added to the first mixture to adjust the pH to 9, resulting in a second mixture. The second mixture was stirred to form a gel for 22 hours. A phosphorus source was added to the gel, causing partial dissolution and resulting in a third mixture. This third mixture was aged at 10–30°C for 70 hours. After aging, it was dried at 75°C and then ground to obtain lithium zirconium phosphate oligomer particles. The degree of polymerization of the prepared lithium zirconium phosphate oligomer particles was 5–10. The molar ratio of phosphorus source to triethylamine was 1:200. The sol-gel conversion rate was tested to be 90%.
[0073] In step S22 of Example 4, the molar ratio of the corresponding lithium zirconium phosphate oligomer to PEG4-COOH was 1:0.5. The D50 particle size distribution of the prepared lithium zirconium phosphate oligomer was 370 nm.
[0074] Example 5 Most of the steps in this embodiment are the same as those in embodiment 3. The difference is that most of the steps in this embodiment are the same as those in embodiment 1. The difference is that step S13 is different, as detailed below.
[0075] S13: Triethylamine was added to the first mixture to adjust the pH to 8, resulting in a second mixture. The second mixture was stirred to form a gel for 22 hours. A phosphorus source was added to the gel, causing partial dissolution and resulting in a third mixture. This third mixture was aged at 10–30°C for 70 hours. After aging, it was dried at 75°C and then ground to obtain lithium zirconium phosphate oligomer particles. The degree of polymerization of the prepared lithium zirconium phosphate oligomer particles was 5–10. The molar ratio of triethylamine to phosphorus source was 100:1. The sol-gel conversion rate was tested to be 96%.
[0076] In step S22 of Example 5, the molar ratio of the corresponding lithium zirconium phosphate oligomer to PEG4-COOH is 1:1. The D50 particle size of the prepared lithium zirconium phosphate oligomer is 80 nm.
[0077] Example 6 Most steps in this embodiment are the same as in Example 3. The difference lies in the following: In step S11, the raw materials are different. In this embodiment, the lithium source is lithium chloride, the zirconium source is zirconium oxychloride, the phosphorus source is phosphoric acid, the first compound is trimethylamine, and the molar ratio of lithium source:zirconium source:phosphorus source is 1:2:3. In step S13, the molar ratio of triethylamine to phosphorus source is 100:1, and the sol-gel conversion rate is tested to be 96%. In step S22, the molar ratio of lithium zirconium phosphate oligomer to PEG4-COOH is 1:2. The remaining steps are the same as in Example 3. The D50 particle size of the lithium zirconium phosphate oligomer prepared in Example 6 is 80 nm.
[0078] Example 7 Most of the steps in this embodiment are the same as those in Example 3, except that the molar ratio of lithium zirconium phosphate oligomer to PEG4-COOH in step S22 is 1:4. The rest is the same as in Example 1.
[0079] Example 8 Most of the steps in this embodiment are the same as those in Example 3, except that the molar ratio of lithium zirconium phosphate oligomer to PEG4-COOH in step S22 is 1:6. The rest is the same as in Example 1.
[0080] Example 9 Most of the steps in this embodiment are the same as those in Example 3, except that the molar ratio of lithium zirconium phosphate oligomer to PEG4-COOH in step S22 is 1:0.2. The rest is the same as in Example 1.
[0081] Example 10 Most of the steps in this embodiment are the same as those in Example 3, except that the molar ratio of lithium zirconium phosphate oligomer to PEG4-COOH in step S22 is 1:8.5. The rest is the same as in Example 1.
[0082] Comparative Example 1 Purchase existing lithium zirconium phosphate and polyethylene glycol (PEG), and grind and mix the PEG and lithium zirconium phosphate by physical means to obtain a mixture.
[0083] The general formulas of the lithium zirconium phosphate oligomers prepared in the above embodiments are recorded in Table 1, and the specific results are shown in Table 1.
[0084] SEM testing The lithium zirconium phosphate oligomers prepared in Example 3 were subjected to SEM testing. Specific test results are shown below. Figure 1 and Figure 2 .
[0085] DLS test The lithium zirconium phosphate oligomers prepared in step S13 of Examples 1-4 above were characterized by DLS. The test results are shown in [Figure 1]. Figure 3 Electrical performance testing The lithium zirconium phosphate oligomers prepared in the above embodiments, the mixture of lithium zirconium phosphate and polyethylene glycol in Comparative Example 1, and composite electrolyte membranes were prepared according to existing technology. A lithium metal sheet was used as the negative electrode, and the composite electrolyte membrane was assembled with the positive electrode and the positive electrode to form a solid-state battery. The positive electrode was prepared according to existing technology with a mass ratio of lithium iron phosphate: conductive carbon black: PVDF of 8:1:1. The proportion of lithium zirconium phosphate oligomers in the composite electrolyte membrane in the above embodiments and the proportion of lithium zirconium phosphate in the composite electrolyte membrane in Comparative Example 1 are the same.
[0086] 1) Ionic conductivity test The electrolyte film prepared above is subjected to ionic conductivity testing. The method includes: the ionic conductivity σ of the electrolyte film can be calculated by formula (1) from the bulk resistance R in the electrolyte AC impedance spectrum, the area A of the electrolyte film facing the contact electrode, and the thickness d of the electrolyte film.
[0087] σ(S·cm -1 )= Equation (1) The results of the above ionic conductivity tests are shown in Table 1.
[0088] 2) Cycle performance of solid-state batteries The battery's discharge capacity (mAh / g) was tested at 25°C and 0.1C / 0.1C for 50 cycles. The test results are shown in Table 1.
[0089] Table 1 As shown in Table 1, compared with Comparative Example 1, Examples 1-4 directly physically mixed lithium zirconium phosphate and polyethylene glycol (PEG), which failed to form PEG. x The molecular-level composite structure between -COOH and lithium zirconium phosphate, as shown in Comparative Example 1, resulted in electrolyte films with low ionic conductivity. In contrast, the lithium zirconium phosphate oligomers prepared in Examples 1-4 satisfied the properties of the compound shown in Formula 1, [LiZr2(PO4)3]. m [PEG x -COO] n Equation 1, where m is 1 and n is 0.5~8, uses a chemical compounding method to achieve PEG. x Molecular-level composite between -COOH and lithium zirconium phosphate, PEG x There are no micron-sized gaps between -COOH and lithium zirconium phosphate, which can form a continuous ion transport path. The resulting electrolyte film has high ionic conductivity and good battery cycle performance.
[0090] Comparing Examples 1-4, the composite solid electrolyte in Example 3 exhibits the highest ionic conductivity. This indicates that within the pH range of 7.5-8.5, the D50 particle size range of the obtained lithium zirconium phosphate oligomers is 2-200 nm. This demonstrates that within the pH range of 7.5-8.5, the lithium zirconium phosphate oligomers have a high dielectric constant, effectively dissociating lithium salt ion pairs, increasing the concentration of free lithium ions in the battery system, improving lithium ion mobility, and thus enhancing the ionic conductivity of the composite solid electrolyte. Comparing Examples 3 and 5-8, the composite solid electrolytes in Examples 5-7 all exhibit high ionic conductivity, corresponding to good battery cycle performance. This indicates that the lithium zirconium phosphate oligomer particles and the PEG... x When the molar ratio of -COOH is in the range of 1:(1~4), lithium zirconium phosphate oligomers are obtained, and composite solid electrolytes are prepared with high ionic conductivity, which improves the cycle performance of the battery.
[0091] Examples 3, 5-8, and 9-10 illustrate the interaction between lithium zirconium phosphate oligomer particles and the PEG. x When the molar ratio of -COOH is within the range of 1:(0.5~8), the resulting lithium zirconium phosphate oligomer has a high dielectric constant, which can effectively dissociate lithium salt ion pairs, increase the concentration of free lithium ions in the battery system, improve lithium ion mobility, effectively conduct lithium ions, improve the ionic conductivity of the composite solid electrolyte, and improve the cycle performance of the battery. The composite solid electrolytes obtained in Examples 4 and 8 have the same ionic conductivity, but the battery in Example 8 has a low discharge capacity after 50 cycles at 0.1C / 0.1C. This is because the lithium zirconium phosphate oligomer in Example 8 contains PEG. x This is due to a high content of -COOH.
[0092] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.
Claims
1. A lithium zirconium phosphate oligomer, characterized in that, The general structural formula of the lithium zirconium phosphate oligomer is shown in Formula 1. [LiZr2(PO4)3] m [PEG x -COO] n Equation 1, where m is 1, n is 0.5~8, and x is 1~10.
2. The lithium zirconium phosphate oligomer according to claim 1, characterized in that, The D50 particle size range of the lithium zirconium phosphate oligomer is 2~1000 nm.
3. The method for preparing lithium zirconium phosphate oligomers as described in claim 1 or 2, characterized in that, Includes the following steps: A first mixed system is obtained by uniformly mixing a lithium source, a zirconium source, and a first solvent. A first compound is added to the first mixed system to form a gel. A phosphorus source is added to the gel, and a first post-treatment is performed to obtain lithium zirconium phosphate oligomer particles. The lithium zirconium phosphate oligomer particles were mixed evenly with the second solvent, and PEG was added. x -COOH, stirred at 25℃~35℃ for 1~5h, and after stirring, a second post-treatment was performed to obtain the lithium zirconium phosphate oligomer; The first compound is the compound shown in Formula 2. ， Formula 2 R1, R2, and R3 are each independently selected from at least one alkyl group having 1 to 2 carbon atoms; PEG x -COOH is the compound shown in Formula 3, where x is 1~10; Formula 3.
4. The method for preparing lithium zirconium phosphate oligomers according to claim 3, characterized in that, Adding the first compound to the first mixture to form a gel includes the following steps: At 10~30℃, the first compound is added to the first mixture to obtain a second mixture with a pH of 5~9. The second mixture is stirred to form a gel for 12~24h.
5. The method for preparing lithium zirconium phosphate oligomers according to claim 3, characterized in that, Adding a phosphorus source to the gel and performing a first post-treatment to obtain lithium zirconium phosphate oligomer particles includes the following steps: A phosphorus source was added to the gel to obtain a third mixing system. The third mixing system was then aged, dried, and ground sequentially to obtain the lithium zirconium phosphate oligomer particles. The aging temperature is 10~30℃, and the aging time is 48~72 h; The drying temperature is 60~80℃; The degree of polymerization of the lithium zirconium phosphate oligomer particles is 5 to 10.
6. The method for preparing lithium zirconium phosphate oligomers according to claim 3, characterized in that, The molar ratio of the lithium source, zirconium source, and phosphorus source is (0.5~1):(1~2):(1~3). The molar ratio of the first compound to the phosphorus source is (500~1):
1.
7. The method for preparing lithium zirconium phosphate oligomers according to claim 3, characterized in that, The lithium zirconium phosphate oligomer particles and the PEG x The molar ratio of -COOH is 1:(0.5~8).
8. The method for preparing lithium zirconium phosphate oligomers according to claim 3, characterized in that, Add PEG x -COOH, stirred at 25℃~35℃ for 1~5h, after stirring, a second post-treatment is performed to obtain the lithium zirconium phosphate oligomer, including the following steps: Add PEG x -COOH, stirred at 25℃~35℃ for 1~5h, after stirring, a fourth mixed system is obtained, and the fourth mixed system is successively aged, dried and ground to obtain the lithium zirconium phosphate oligomer particles; The aging temperature is 10~30℃, and the aging time is 48~72 h; The drying temperature is 60~80℃.
9. A composite solid electrolyte, characterized in that, Lithium zirconium phosphate oligomers include those prepared by the method of preparing lithium zirconium phosphate oligomers according to any one of claims 1 or 2, or according to any one of claims 3-8.
10. A solid-state battery, characterized in that, Includes the composite solid electrolyte as described in claim 9.