Phosphate materials with high phosphoric acid content and their application in lithium batteries

Abstract

This invention relates to a phosphate material with a high content of phosphoric acid groups and its application in lithium batteries. The phosphate material with a high content of phosphoric acid groups comprises lithium, aluminum, titanium, phosphorus, oxygen, and doping elements; wherein the doping elements include one or more of magnesium, calcium, gallium, germanium, and silicon; the phosphate material contains, by mass ratio, 0.1%-1.8% lithium, 0.1%-21% aluminum, 16%-35% titanium, 20%-30% phosphorus, 41%-62% oxygen, and 0%-10% doping elements; the X-ray diffraction pattern of the phosphate material shows diffraction peaks at 14.7°, 20.9°, 21.8°, 22.5°, 24.5°, and 29.7°; the Raman spectrum of the phosphate material shows peaks at 316 cm⁻¹. ‑1 356cm ‑1 450cm ‑1 and 1010cm ‑1 The location exhibits characteristic vibration peaks.

Description

Technical Field

[0001] This invention relates to the field of lithium battery materials technology, and in particular to phosphate materials with high phosphate group content and their application in lithium batteries. Background Technology

[0002] With the widespread application and rapid development of lithium batteries, people have increasingly higher requirements for the performance of lithium-ion batteries. Not only are high capacity required, but also good capacity retention during repeated charge and discharge processes, good cycle performance, long service life, high safety, and long storage time are also required.

[0003] Improving battery storage time and reducing self-discharge rate are crucial. Aside from issues caused by physical micro-short circuits (dust and burrs) due to manufacturing defects and side reactions due to excessive internal moisture content, the composition and structural stability of the positive electrode, negative electrode, and separator materials also significantly impact long-term battery storage performance. Typically, impurities or unstable metals contained in the positive electrode, negative electrode, or separator can ionize during charging, depositing on the separator and creating micro-conductive circuits, leading to self-discharge. Therefore, improving battery storage performance is a pressing issue that needs to be addressed. Summary of the Invention

[0004] The purpose of this invention is to provide a phosphate material with a high content of phosphate groups and its application in lithium batteries. This phosphate material with a high content of phosphate groups can reduce the self-discharge rate of the battery, improve its storage performance, and extend its lifespan.

[0005] Therefore, in a first aspect, embodiments of the present invention provide a phosphate material having a high content of phosphate groups, the phosphate material having a high content of phosphate groups comprising: lithium, aluminum, titanium, phosphorus, oxygen, and doping elements; wherein the doping elements comprise one or more of magnesium, calcium, gallium, germanium, and silicon;

[0006] The phosphate material contains, by mass ratio, 0.1%-1.8% lithium, 0.1%-21% aluminum, 16%-35% titanium, 20%-30% phosphorus, 41%-62% oxygen, and 0%-10% doping elements.

[0007] The X-ray diffraction pattern of the phosphate material shows diffraction peaks at 14.7°, 20.9°, 21.8°, 22.5°, 24.5° and 29.7°.

[0008] The Raman spectrum of the phosphate material is at 316 cm⁻¹ -1 356cm-1 450cm -1 and 1010cm -1 The location exhibits characteristic vibration peaks.

[0009] Preferably, the phosphate material has a particle shape that is one or more of spherical, elliptical, square, or irregular.

[0010] Preferably, the particle size of the phosphate material is 50 nm-50 μm.

[0011] Preferably, the ionic conductivity of the phosphate material is 1.2 × 10⁻⁶. -5 S / cm-8.0×10 -3 S / cm.

[0012] Preferably, the melting point of the phosphate material is 1200℃-1450℃.

[0013] Preferably, the pH value of the phosphate material is between 4.0 and 7.5.

[0014] Preferably, the phosphate material is white or light yellow.

[0015] Secondly, embodiments of the present invention provide an application of the phosphate material described in the first aspect above, wherein the phosphate material is used in lithium-ion batteries.

[0016] Preferably, the phosphate material is used as any one of the following: positive electrode additive, positive electrode coating material, negative electrode additive, negative electrode coating material, separator coating material additive, or separator coating material.

[0017] Thirdly, embodiments of the present invention provide a lithium-ion battery comprising the phosphate material described in the first aspect.

[0018] The phosphate material with a high content of phosphate groups provided in this invention contains lithium, aluminum, titanium, phosphorus, oxygen, and doping elements. It can be used as a positive electrode additive, positive electrode coating material, negative electrode additive, negative electrode coating material, separator coating material additive, and separator coating material for lithium-ion batteries. Because the material contains a high content of negatively charged phosphate groups and has a stable structure, it can attract, restrict, and regulate the deposition and ionization of positively charged metal particles during battery storage, preventing the formation of micro-conductive circuits inside the battery. This reduces the battery's self-discharge rate and improves its storage performance and lifespan. Attached Figure Description

[0019] Figure 1 The X-ray diffraction (XRD) pattern of the phosphate material with high phosphate group content provided in Example 1 of the present invention;

[0020] Figure 2 The Raman spectrum of the phosphate material provided in Example 1 of this invention;

[0021] Figure 3 The volume particle size distribution curve of the phosphate material provided in Example 1 of the present invention;

[0022] Figure 4 The image shows the XRD pattern of the phosphate material provided in Example 4 of this invention. Detailed Implementation

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0024] This invention provides a phosphate material with a high content of phosphate groups, comprising: lithium, aluminum, titanium, phosphorus, oxygen, and doping elements; wherein the doping elements include one or more of magnesium, calcium, gallium, germanium, and silicon;

[0025] In the phosphate material of the present invention, the lithium content is 0.1%-1.8%, the aluminum content is 0.1%-21%, the titanium content is 16%-35%, the phosphorus content is 20%-30%, the oxygen content is 41%-62%, and the dopant content is 0%-10% by mass ratio.

[0026] The X-ray diffraction pattern of the phosphate material shows diffraction peaks at 14.7°, 20.9°, 21.8°, 22.5°, 24.5° and 29.7°.

[0027] The Raman spectrum of phosphate materials at 316 cm⁻¹ -1 356cm -1 450cm -1 and 1010cm -1 The location exhibits characteristic vibration peaks.

[0028] The phosphate material of this invention is white or light yellow, with particle shapes including spherical, elliptical, square, or irregular shapes (one or more); particle size is 50 nm-50 μm; melting point is 1200℃-1450℃; pH value is between 4.0 and 7.5. Ionic conductivity is 1.2 × 10⁻⁶. -5 S / cm-8.0×10 -3 S / cm.

[0029] The phosphate material of the present invention can be used as any one of the following in lithium-ion batteries: positive electrode additive, positive electrode coating material, negative electrode additive, negative electrode coating material, separator coating material additive, or separator coating material.

[0030] The phosphate material with high phosphate group content proposed in this invention has been described above. The following detailed description is provided through some specific embodiments, but the scope of protection of this invention is not limited thereto.

[0031] Example 1

[0032] This embodiment provides a phosphate material and its application method in lithium-ion batteries. The content of each element in the phosphate material is as follows: lithium content is 0.13%, aluminum content is 0.51%, titanium content is 24.52%, germanium content is 2.76%, phosphorus content is 23.51%, and oxygen content is 48.57%.

[0033] The XRD diffraction pattern of the material is as follows: Figure 1 As shown, from Figure 1 It can be seen that there are strong characteristic diffraction peaks at 2θ diffraction angles of 14.7°, 20.9°, 21.8°, 22.5°, 24.5°, and 29.7°.

[0034] The Raman spectrum of the material is as follows: Figure 2 As shown, from Figure 2 It can be seen from 316cm -1 356cm -1 450cm -1 and 1010cm -1 There are strong characteristic vibration peaks near the location.

[0035] The volumetric particle size distribution curve of the material is as follows: Figure 3 As shown in the figure, the particle size D50 is 4.1 μm.

[0036] The material was tested and found to have a pH value of 7.08, a melting point of approximately 1425℃, and an ionic conductivity of 3.7 × 10⁻⁶. -4 The material has a density of S / cm and is white and irregular in shape. ICP elemental analysis was performed after complete digestion of the material, revealing the following results: lithium content 25954 ppm, aluminum content 31654 ppm, and titanium content 172792 ppm, which are basically consistent with the theoretical elemental contents of the material.

[0037] The improvement of battery performance by testing materials: NCM523 (positive electrode material), polyvinylidene fluoride (PVDF), conductive carbon black, and the aforementioned phosphate materials were mixed with N-methylpyrrolidone (NMP) in a mass ratio of 95.0%:2.5%:1.3%:1.2% to form a slurry. This slurry was then coated onto an aluminum foil current collector to form the positive electrode. A graphite electrode was used as the negative electrode, and an alumina-coated polypropylene (PP) separator was added. A 1M LiPF6 electrolyte was injected, and the cells were assembled into coin cells in an argon-filled glove box. The cells were charged at 0.5C to 4.4V, then constant-voltage charged until the current decreased to 0.05C. The self-discharge performance (K-value) was then tested at 25°C for 3, 7, and 15 days. Simultaneously, the capacity retention after 50 cycles at 0.5C and 2.75-4.4V was tested.

[0038] Example 2

[0039] The positive electrode material NCM523, PVDF, and conductive carbon black were uniformly mixed with NMP in a mass ratio of 96.2%:2.5%:1.3% to form a slurry. This slurry was coated onto an aluminum foil current collector to form an electrode sheet. A 1 μm thick layer of the phosphate material described in Example 1 was then coated onto the surface of the electrode sheet to prepare a positive electrode sheet. This positive electrode sheet was then assembled with a graphite electrode sheet, an alumina PP separator, and a 1M LiPF6 electrolyte in an argon-filled glove box to form a coin cell. The self-discharge performance and cycle performance of the battery were tested according to the method described in Example 1.

[0040] Example 3

[0041] A slurry was prepared by uniformly mixing NCM523, PVDF, and conductive carbon black in a mass ratio of 96.2%:2.5%:1.3% with NMP. This slurry was then coated onto an aluminum foil current collector to form a positive electrode sheet. A 1 μm thick layer of the phosphate material described in Example 1 was coated onto the surface of a graphite negative electrode sheet to form a negative electrode sheet. The negative electrode sheet was then assembled with an alumina PP separator and a 1M LiPF6 electrolyte in an argon-filled glove box to form a coin cell. The self-discharge performance and cycle performance of the battery were tested according to the method described in Example 1.

[0042] Example 4

[0043] This embodiment provides a phosphate material in which the content of each element is as follows: lithium 0.27%, aluminum 1.58%, magnesium 0.24%, titanium 20.35%, silicon 3.30%, phosphorus 24.22%, and oxygen 50.04%. The XRD diffraction pattern of this material is shown below. Figure 4 As shown, from Figure 4It can be seen that there are strong characteristic diffraction peaks at 2θ diffraction angles of 14.7°, 20.9°, 21.8°, 22.5°, 24.5°, and 29.7°.

[0044] The material appears as a white powder. Tests showed a pH of 6.17, a melting point of 1450℃ at room temperature, and an ionic conductivity of 4.3 × 10⁻⁶. -4 S / cm. After complete digestion of the material, ICP analysis of the content of each element showed that the lithium content was 18034 ppm, the aluminum content was 114187 ppm, the magnesium content was 14431 ppm, the titanium content was 122376 ppm, and the silicon content was 19889 ppm.

[0045] The improvement of battery performance by testing materials: A slurry was prepared by uniformly mixing LiCoO2, PVDF, and conductive carbon black with NMP in a mass ratio of 95.0%:2.0%:3.0%. This slurry was coated onto an aluminum foil current collector to form a positive electrode. A 2μm thick layer of the aforementioned phosphate material was coated onto a graphite negative electrode to form a negative electrode. These negative electrodes were then assembled into a coin cell using an alumina PE separator and a 1M LiPF6 electrolyte in an argon-filled glove box. The battery was charged at 0.2C to 4.45V, then constant-voltage charged until the current decreased to 0.02C. The self-discharge performance (K-value) was then tested at 40℃ for 1 day, 3 days, and 7 days. Simultaneously, the capacity retention was measured after 50 cycles at 0.2C and 2.75-4.45V at room temperature.

[0046] Example 5

[0047] The positive electrode material LiCoO2, PVDF, and conductive carbon black were mixed with NMP in a mass ratio of 95.0%:2.0%:3.0% to form a slurry, which was then coated onto an aluminum foil current collector to form the positive electrode sheet. A graphite electrode sheet was used as the negative electrode. Alumina was mixed with the phosphate material from Example 4 in a 6:4 ratio to form a slurry, which was then coated onto both sides of a PE base film to form a separator. A 1M LiPF6 electrolyte was used, and the cells were assembled into a coin cell in an argon-filled glove box. The self-discharge performance and cycle performance of the battery were tested according to the method described in Example 4.

[0048] Example 6

[0049] The positive electrode material LiCoO2, PVDF, and conductive carbon black were uniformly mixed with NMP in a mass ratio of 95.0%:2.0%:3.0% to form a slurry. This slurry was then coated onto an aluminum foil current collector to form the positive electrode sheet. A graphite electrode sheet was used as the negative electrode. The phosphate material from Example 4 was uniformly coated on one side of an alumina-based PE film, while the other side was coated with alumina. This film was used as the separator for assembling the battery. A 1M LiPF6 electrolyte was used, and the batteries were assembled into coin cells in an argon-filled glove box. The self-discharge performance and cycle performance of the batteries were tested according to the method described in the example.

[0050] Comparative Example 1

[0051] The positive electrode material NCM523, PVDF, and conductive carbon black were mixed with NMP in a mass ratio of 96.2%:2.5%:1.3% to form a slurry. This slurry was then coated onto an aluminum foil current collector to form the positive electrode. A graphite electrode was used as the negative electrode, and an alumina-coated PP separator was added. A 1M LiPF6 electrolyte was injected, and the cells were assembled into coin cells in an argon-filled glove box. The cells were charged at a 0.5C rate to 4.4V, then charged at a constant voltage until the current decreased to 0.05C. The self-discharge performance (K-value) of the cells was then tested at a constant temperature of 25℃ for 3, 7, and 15 days. Simultaneously, the capacity retention rate after 50 cycles at 0.5C and 2.75-4.4V was tested.

[0052] Comparative Example 2

[0053] This comparative example provides a lithium aluminum titanium phosphate (LATP) material, in which the content of each element is as follows: lithium content is 2.74%, aluminum content is 3.54%, titanium content is 18.87%, phosphorus content is 24.41%, and oxygen content is 50.44%.

[0054] The effect of the lithium titanium aluminum phosphate material on battery performance was tested as follows: The positive electrode material NCM523, PVDF, and conductive carbon black were mixed with the aforementioned lithium titanium aluminum phosphate material at a mass ratio of 95.0%:2.5%:1.3%:1.2%, and uniformly mixed with NMP to form a slurry. This slurry was then coated onto an aluminum foil current collector to form the positive electrode. A graphite electrode was used as the negative electrode, and an alumina-coated PP separator was added. A 1M LiPF6 electrolyte was then injected, and the cells were assembled into a coin cell in an argon-filled glove box. Tests were conducted according to the conditions described in Example 1.

[0055] Calculations show that the molar percentage of phosphate groups in the phosphate material in Example 1 is 56.34%, while the molar percentage of phosphate groups in the lithium titanium aluminum phosphate material in Comparative Example 2 is 46.15%. The comparison of their self-discharge performance and cycle performance is shown in Table 1.

[0056] Table 1 summarizes the experimental results of Examples 1-3 and Comparative Examples 1 and 2.

[0057]

[0058] Table 1

[0059] As can be seen, the battery prepared in this embodiment with phosphate material has a slightly higher capacity retention rate after 50 cycles than the battery without this material. Furthermore, the battery prepared by this invention with phosphate material containing a high content of phosphate groups has a lower self-discharge K value than the battery without phosphate groups and the battery with ordinary phosphate group content of existing LATP material. This indicates that the material is effective in reducing the self-discharge performance K value of the battery, that is, it can improve the battery's storage performance and also has a certain effect on improving cycle life.

[0060] Comparative Example 3

[0061] The positive electrode material LiCoO2, PVDF, and conductive carbon black were mixed with NMP in a mass ratio of 95.0%:2.0%:3.0% to form a slurry. This slurry was then coated onto an aluminum foil current collector to form an electrode sheet. This electrode sheet was then assembled with a graphite electrode sheet, an alumina-coated PE separator, and a 1M LiPF6 electrolyte in an argon-filled glove box to form a coin cell. The self-discharge performance and cycle performance of the battery were tested according to the method described in Example 4.

[0062] Table 2 summarizes the experimental results of Examples 4-6 and Comparative Example 3. It can be seen that the capacity retention rate of the battery containing phosphate material after 50 cycles is slightly higher than that of the battery without the material, and the self-discharge K value of the battery containing phosphate material is lower than that of the battery without the material. This indicates that the material is effective in reducing the self-discharge performance K value of the battery, that is, it can improve the storage performance of the battery and at the same time improve the cycle life to a certain extent.

[0063]

[0064] Table 2

[0065] The phosphate material with a high content of phosphate groups provided in this embodiment contains lithium, aluminum, titanium, phosphorus, oxygen, and doping elements. It can be used as a positive electrode additive, positive electrode coating material, negative electrode additive, negative electrode coating material, separator coating material additive, and separator coating material for lithium-ion batteries. Because the material contains a high content of negatively charged phosphate groups and has a stable structure, it can attract, restrict, and regulate the deposition and ionization of positively charged metal particles during battery storage, preventing the formation of micro-conductive circuits inside the battery. This reduces the battery's self-discharge rate and improves its storage performance and lifespan.

[0066] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A phosphate material with a high content of phosphate groups, characterized in that, The phosphate material with a high content of phosphate groups includes: lithium, aluminum, titanium, phosphorus, oxygen, and doping elements; wherein the doping elements include one or more of magnesium, calcium, gallium, germanium, and silicon. The phosphate material contains, by mass ratio, 0.1%-1.8% lithium, 0.1%-21% aluminum, 16%-35% titanium, 20%-30% phosphorus, 41%-62% oxygen, and 0%-10% doping elements. The X-ray diffraction pattern of the phosphate material shows diffraction peaks at 14.7°, 20.9°, 21.8°, 22.5°, 24.5° and 29.7°. The Raman spectrum of the phosphate material is at 316 cm⁻¹ -1 356cm -1 450cm -1 and 1010cm -1 The location exhibits characteristic vibration peaks.

2. The phosphate material according to claim 1, characterized in that, The phosphate material has one or more of the following particle shapes: spherical, elliptical, square, or irregular.

3. The phosphate material according to claim 1, characterized in that, The particle size of the phosphate material is 50nm-50um.

4. The phosphate material according to claim 1, characterized in that, The ionic conductivity of the phosphate material is 1.2 × 10⁻⁶. -5 S / cm-8.0×10 -3 S / cm.

5. The phosphate material according to claim 1, characterized in that, The melting point of the phosphate material is 1200℃-1450℃.

6. The phosphate material according to claim 1, characterized in that, The pH value of the phosphate material is between 4.0 and 7.

5.

7. The phosphate material according to claim 1, characterized in that, The phosphate material is white or light yellow.

8. The use of the phosphate material according to any one of claims 1-7, characterized in that, The phosphate material is used in lithium-ion batteries.

9. The use of the phosphate material according to claim 8, characterized in that, The phosphate material is used as any one of the following: positive electrode additive, positive electrode coating material, negative electrode additive, negative electrode coating material additive, diaphragm coating material additive, or diaphragm coating material.

10. A lithium-ion battery, characterized in that, The lithium-ion battery comprises the phosphate material described in any one of claims 1-7.

Images