Patent Application
20240421300
The present disclosure relates to the field of lithium ion batteries, and particularly to a lithium iron phosphate positive electrode active material, a preparation method thereof, and a lithium ion battery.
Lithium iron phosphate material has wide use due to the better safety, low cost, environmental friendliness and other advantages. However, the lithium iron phosphate material also has defects. The maximum compaction density of the lithium iron phosphate material is low (2.1-2.5 g/cm3), which leads to the low energy density of batteries prepared with the lithium iron phosphate material, so the demand for batteries with long battery life may not be met. To improve the energy density of the battery, a lithium iron phosphate material having a high compaction density has become a popular trend of development in the industry. However, for the lithium iron phosphate material having a high compaction density, when the compaction density of the lithium is increased, the electrochemical performance of the battery is often reduced.
To solve the above technical problems, the present disclosure provides a lithium iron phosphate positive electrode active material, a preparation method thereof, and a lithium ion battery. By adjusting the particle size parameters of two constituent lithium iron phosphate materials, the positive electrode active material obtained by mixing the two materials at a ratio is allowed to have a high compaction density, and a battery prepared therewith has an excellent electrochemical performance.
In a first aspect, the present disclosure provides a lithium iron phosphate positive electrode active material. The lithium iron phosphate positive electrode active material includes a first lithium iron phosphate material and a second lithium iron phosphate material. D1mo is a first particle size of first particles that have a largest volume distribution value of the first lithium iron phosphate material, and 0.3≤D1mo≤3.2. D2mo is a second particle size of second particles that have a largest volume distribution value of the second lithium iron phosphate material, 1≤D2mo≤5, and D1mo<D2mo. A distribution discreteness of the first particle size of the first lithium iron phosphate material is A1, and a distribution discreteness of the second particle size of the second lithium iron phosphate material is A2, where 1≤A1≤3, and 2≤A2≤4. D1mo and A1 meet: 4.07<A1×(2.31+D1mo) <16, and D2mo and A2 meet: −0.4<A2×(D2mo−1.15)<14.
The maximum compaction density of a positive electrode sheet containing the positive electrode active material can be 2.6 g/cm3 or higher, and a battery prepared therewith has an excellent electrochemical performance.
According to the lithium iron phosphate positive electrode active material provided in the embodiment of the present disclosure, by configuring the range of the particle size Dmo, the range of the distribution discreteness A of the particle size, and the relation formula of Dmo and A of the two lithium iron phosphate materials, a positive electrode sheet prepared with the positive electrode active material formed by mixing the two lithium iron phosphate materials at a ratio may have a high compaction density, and the compaction density is up to 2.6 g/cm3 or higher, which improves the energy density of a battery prepared with the positive electrode active material. In addition, the battery prepared with the positive electrode active material has an excellent electrochemical performance, and particularly, a good cycle performance.
In some embodiments, D1mo meets: 0.31≤D1mo≤2.5.
In some embodiments, D1mo meets: 0.35≤D1mo≤2.46.
In some embodiments, D2mo meets: 1.2≤D2mo≤4.5.
In some embodiments, D2mo meets: 1.25≤D2mo≤4.48.
In some embodiments, the weight ratio of the first lithium iron phosphate material and the second lithium iron phosphate material is in the range of 1:(0.4-4).
In some embodiments, the weight ratio of the first lithium iron phosphate material and the second lithium iron phosphate material is in the range of 1:(0.6-2.5).
In some embodiments, the weight ratio of the first lithium iron phosphate material and the second lithium iron phosphate material is in the range of 1:(1-2.5).
In some embodiments, a carbon coating layer is disposed on a surface of the first lithium iron phosphate material, and a carbon coating layer is disposed on a surface of the second lithium iron phosphate material.
In some embodiments, D1mo and A1 meet: 4.08≤A1×(2.31+D1mo)≤15.9.
In some embodiments, D1mo and A1 meets: 4.11≤A1×(2.31+D1mo)≤15.86.
In some embodiments, D2mo and A2 meet: −0.38≤A2×(D2mo−1.15)≤13.95.
According to the lithium iron phosphate positive electrode active material provided in the first aspect of the present disclosure, the positive electrode active material is formed by mixing two lithium iron phosphate materials meeting the requirements of the particle size parameters at a ratio, the compaction density of a positive electrode sheet prepared with the positive electrode active material is high, and a battery prepared therewith has good cycle performance and rate performance.
In a second aspect, the present disclosure provides a method for preparing a lithium iron phosphate positive electrode active material. The method includes the following steps: A first lithium iron phosphate material and a second lithium iron phosphate material are provided. D1mo is a first particle size of first particles that have a largest volume distribution value of the first lithium iron phosphate material, and 0.3≤D1mo≤3.2. D2mo is a second particle size of second particles that have a largest volume distribution value of the second lithium iron phosphate material, 1≤D2mo≤5, and D1mo<D2mo. The distribution discreteness of the first particle size of the first lithium iron phosphate material is A1, and a distribution discreteness of the second particle size of the second lithium iron phosphate material is A2, where 1≤A1≤3, and 2≤A2≤4. D1mo and A1 meet: 4.07<A1×(2.31+D1mo)<16. D2mo and A2 meet: −0.4<A2×(D2mo−1.15)<14. The first lithium iron phosphate material and the second lithium iron phosphate material are mixed, to obtain the lithium iron phosphate positive electrode active material.
In the method for preparing a lithium iron phosphate positive electrode active material, two lithium iron phosphate materials meeting the requirements of the particle size parameters are mixed at a ratio, so that the obtained positive electrode active material has a high compaction density, and a battery prepared with the positive electrode active material has good cycle performance and rate performance. The preparation method is a simple process, and is easy to operate, thus being suitable for use in large-scale production.
In a third aspect, the present disclosure provides a lithium ion battery. The lithium ion battery includes a positive electrode sheet. The positive electrode sheet includes a lithium iron phosphate positive electrode active material according to the first aspect of the present disclosure, or a lithium iron phosphate positive electrode active material prepared according to the method as described in the second aspect of the present disclosure.
In some embodiments, the lithium ion battery further includes a negative electrode sheet, an electrolyte solution, and a separator located between the positive electrode sheet and the negative electrode sheet.
In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on a surface of the positive electrode current collector.
In some embodiments, the positive electrode active material layer includes the lithium iron phosphate positive electrode active material, a binder, and a conductive agent.
In some embodiments, the positive electrode current collector includes any one of an aluminum foil, a carbon coated aluminum foil, or a perforated aluminum foil.
In some embodiments, the conductive agent includes at least one of carbon nanotubes, graphene, carbon black, or carbon fiber.
In some embodiments, the maximum compaction density of the positive electrode sheet is larger than 2.6 g/cm3.
The lithium ion battery using the positive electrode sheet has a high energy density and excellent cycle performance.
The present disclosure provides a lithium iron phosphate positive electrode active material, a preparation method thereof, and a lithium ion battery. By adjusting the particle size parameters of two constituent lithium iron phosphate materials, the positive electrode active material obtained by mixing the two materials at a ratio is allowed to have a high compaction density, and a battery prepared therewith has an excellent electrochemical performance.
In a first aspect, the present disclosure provides a lithium iron phosphate positive electrode active material. The lithium iron phosphate positive electrode active material is formed by mixing a first lithium iron phosphate material and a second lithium iron phosphate material. The first lithium iron phosphate material includes particles having different particle sizes. A total volume of particles having a particle size D1 is V1, where V1=unit particle volume×the number of the particles having the particle size D1. Since the first lithium iron phosphate material has different particle sizes, the particles of the first lithium iron phosphate material have a volume distribution with respect to the particle sizes. D1mo μm is a particle size of first particles that have the largest volume distribution value of the first lithium iron phosphate material, 0.3≤D1mo≤3.2. The second lithium iron phosphate material includes particles having different particle sizes. A total volume of particles having a particle size D2 is V2, where V2=unit particle volume×the number of the particles having the particle size D2. Since the second lithium iron phosphate material has different particle sizes, the particles of the second lithium iron phosphate material have a volume distribution with respect to the particle sizes. D2mo μm is a particle size of second particles that have the largest volume distribution value of the second lithium iron phosphate material, 1≤D2mo≤5, and D1mo<D2mo. The distribution discreteness in particle size of the first lithium iron phosphate material is A1, and the distribution discreteness in particle size of the second lithium iron phosphate material is A2, where 1≤A1≤3, and 2≤A2≤4. D1mo and A1 meet a relation formula of: 4.07<A1×(2.31+D1mo)<16. D2mo and A2 meet a relation formula of: −0.4<A2×(D2mo−1.15)<14.
The maximum compaction density of a positive electrode sheet containing the positive electrode active material can be 2.6 g/cm3 or higher, and a battery prepared therewith has an excellent electrochemical performance.
According to the lithium iron phosphate positive electrode active material provided in the present disclosure, by configuring the range of the particle size Dmo, the range of the distribution discreteness A in particle size, and the range of the relevant relation formula of Dmo and A of the two constituent lithium iron phosphate materials, a positive electrode sheet prepared with the positive electrode active material formed by mixing the two lithium iron phosphate materials at a ratio is allowed to have a high compaction density that is 2.6 g/cm3 or higher, which improves of the energy density of a battery prepared with the positive electrode active material. In addition, the battery prepared with the positive electrode active material has an excellent electrochemical performance, particularly cycle performance. In some embodiments, 4.08≤A1×(2.31+D1mo)≤15.9. In some embodiments, A1×(2.31+D1mo) is in the range of 4.11-15.86.
In some embodiments, −0.38≤A2×(D2mo−1.15)≤13.95.
In some embodiments, the D1mo value of the first lithium iron phosphate material and the D2mo value of the second lithium iron phosphate material can be obtained from their respective laser particle size distribution diagrams. In some embodiments, the test instrument is a laser particle size analyzer (such as Malvern 3000). The test method can be found in GB/T 19077-2016/ISO 13320:2009 Particle size analysis-Laser diffraction methods.
In some embodiments, the distribution discreteness in particle size of the first lithium iron phosphate material is A1=(D190-D110)/D150, and the distribution discreteness in particle size of the second lithium iron phosphate material is: A2=(D290-D210)/D250, D190 represents the corresponding particle size when the cumulative volume percentage of the first lithium iron phosphate material is 90% in the laser particle size distribution diagram of the first lithium iron phosphate material; D110 represents the corresponding particle size when the cumulative volume percentage of the first lithium iron phosphate material is 10%; and D150 represents the corresponding particle size when the cumulative volume percentage of the first lithium iron phosphate material is 50%. A smaller A1 represents a smaller distribution discreteness in particle size (or a narrower width of the range of particle size distribution) of the first lithium iron phosphate material and a higher concentration in the particle size distribution. Similarly, D290, D210, and D250 respectively represent the corresponding particle sizes when the cumulative volume percentages of the second lithium iron phosphate material reach 90%, 10%, and 50% respectively in the laser particle size distribution diagram of the second lithium iron phosphate material. The D190, D110, and D150 values of the first lithium iron phosphate material and the D290, D210, and D250 values of the second lithium iron phosphate material can also be obtained from their laser particle size distribution diagrams. The test method can be found in GB/T 19077-2016/ISO 13320:2009 Particle size analysis-Laser diffraction methods.
In some embodiments, D1mo<D2mo. When D1mo of the lithium iron phosphate material is small, the lithium ion diffusion path is shorter, and the prepared battery has a good electrical performance. When D2mo of the lithium iron phosphate material is large, the compaction density of the positive electrode active material can be increased. Given a particle size Dmo that is in the above range, in combination with the ranges of A1 and A2, and relation formulas there between, the two lithium iron phosphate materials can be allowed to form a dense packing when they are mixed uniformly at a ratio, so that the compaction density of a positive electrode sheet prepared with the positive electrode active material prepared therewith can be increased, without compromising the cycle performance of the battery.
In some embodiments, the value of D1mo is in the range of: 0.31≤D1mo≤2.5. Further, the value of D1mo is in the range of: 0.35≤D1mo≤2.46.
In some embodiments, the value of D2mo is in the range of: 1.2≤D2mo≤5. Further, the value of D2mo is in the range of: 1.2≤D2mo≤4.5. Furthermore, the value of D2mo is in the range of: 1.25≤D2mo≤4.48.
When the D1mo and D2mo values are in the above ranges and meet D1mo<D2mo, the two lithium iron phosphate materials can allow the high compaction density of the positive electrode sheet and the good electrochemical performance of the battery.
In some embodiments, the of the first lithium iron phosphate material and the second lithium iron phosphate material can be mixed at a weight ratio, the maximum compaction density of a positive electrode sheet prepared with the lithium iron phosphate positive electrode active material is high, and the cycle performance of a battery prepared therewith is good. In some embodiments, the mixing weight ratio of the first lithium iron phosphate material and the second lithium iron phosphate material is in the range of 1:(0.4-4), and further in the range of 1:(0.6-2.5), for example, in the range of 1:(1-2.5). In this case, the positive electrode active material formed by mixing the two lithium iron phosphate materials can allow the high compaction density of the electrode sheet and the good cycle performance of the battery.
In some embodiments, the first lithium iron phosphate material and the second lithium iron phosphate material may have a carbon coating layer on the surface, which can be obtained by sequentially sanding, spray drying, and sintering a mixed slurry of a phosphorus source, an iron source, a lithium source, and a carbon source. In the present disclosure, the preparation method of the two lithium iron phosphate materials is not limited. The presence of the carbon coating layer allows the first and the second lithium iron phosphate material to have a good electrical conductivity, and less side reactions with the electrolyte solution. The positive electrode active material obtained by mixing the two has a good electrical conductivity, and the cycle performance of the battery is good.
According to the lithium iron phosphate positive electrode active material provided in the first aspect of the present disclosure, the positive electrode active material is formed by mixing two lithium iron phosphate materials meeting the requirements of particle size parameters at a ratio, the compaction density of a positive electrode sheet prepared with the positive electrode active material is high, and a battery prepared therewith has good cycle performance and rate performance.
In a second aspect, the present disclosure provides a method for preparing a lithium iron phosphate positive electrode active material. As shown in
In the method for preparing a lithium iron phosphate positive electrode active material, two lithium iron phosphate materials meeting the requirements of particle size parameters are mixed at a ratio, to allow that the obtained positive electrode active material has a high compaction density, and a battery prepared with the positive electrode active material has good cycle performance and rate performance. The preparation method has a simple process, and is easy to operate, thus being suitable for use in large-scale production.
A positive electrode sheet is provided. The positive electrode sheet includes a lithium iron phosphate positive electrode active material according to the first aspect of the present disclosure, or a lithium iron phosphate positive electrode active material prepared according to the method as described in the second aspect of the present disclosure.
In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer arranged on a surface of the positive electrode current collector. The positive electrode active material layer includes the lithium iron phosphate positive electrode active material, a binder, and a conductive agent.
In some embodiments, the maximum compaction density of the positive electrode sheet is 2.6 g/cm3 or higher. In some embodiments, the maximum compaction density is 2.62-2.8 g/cm3, and further 2.65-2.75 g/cm3. It is to be understood that the maximum compaction density of the positive electrode sheet refers to the corresponding compaction density of the electrode sheet when the active material particles in the positive electrode sheet are crushed under a certain pressure.
The positive electrode material layer can be formed by coating a positive electrode paste including the lithium iron phosphate positive electrode active material, the conductive agent, the binder and a solvent on the positive electrode current collector. The solvent can be one or more of N-methylpyrrolidone (NMP), acetone, and dimethyl acetamide (DMAC). The positive electrode current collector includes any one of an aluminum foil, a carbon-coated aluminum foil, and a perforated aluminum foil. The conductive agent includes, but is not limited to, one or more of carbon nanotubes, graphene, carbon black, carbon fiber, and the like. The binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polyacrylate, polyacrylonitrile (PAN), sodium carboxymethyl cellulose (CMC), and sodium alginate.
In a third aspect, the present disclosure provides a lithium ion battery. The lithium ion battery includes a positive electrode sheet according to the third aspect of the present disclosure.
In some embodiments, the lithium ion battery further includes a negative electrode sheet, an electrolyte solution, and a separator located between the positive electrode sheet and the negative electrode sheet.
The lithium ion battery using the positive electrode sheet has a high energy density and excellent cycle performance.
The following descriptions are some implementations of the present disclosure. It should be noted that several improvements and modifications can be made by those of ordinary skill in the art without departing from the principle of the present disclosure, which shall fall within the protection scope of the present disclosure.
In the following, the technical solution of the present disclosure will be described in combination with embodiments.
A method for preparing a lithium iron phosphate positive electrode active material (referred to as positive electrode active material hereinafter) includes the following steps.
A first lithium iron phosphate material LFP-1 was used. When a particle size of particles of LFP-1 that have the largest volume distribution value of LFP-1, the corresponding particle size was 0.31 μm, and the distribution discreteness in particle size was 2.22. That is, D1mo was 0.31, A1 was 2.22, and A1×(2.31+D1mo)=5.82. A second lithium iron phosphate material LFP-2 was used. When a particle size of particles of LFP-2 that have the largest volume distribution value of LFP-2, the corresponding particle size was 1.28 μm, and the distribution discreteness in particle size was 2.24. That is, D2mo was 1.28, A2 was 2.24, and A2×(D2mo−1.15)=0.29.
The LFP-1 material and the LFP-2 material were mixed at a weight ratio of 2:8, to obtain a lithium iron phosphate positive electrode active material LFP-3.
The lithium iron phosphate positive electrode active material LFP-3 was prepared into a positive electrode sheet as follows. The LFP-3 material was mixed with a conductive agent-carbon nanotubes, a binder (e.g., polyvinylidene fluoride (PVDF)) and a solvent N-methylpyrrolidone (NMP) at a weight ratio of 100:3:2:60, and mixed uniformly, to obtain a positive electrode paste. The positive electrode paste was coated on two sides of a carbon-coated aluminum foil, and dried, to obtain a two-sided positive electrode sheet having an areal density of 360 g/m2. The maximum compaction density of the positive electrode sheet without particle breakage was determined. The maximum compaction density of the positive electrode sheet was 2.70 g/cm3.
Preparation of pouch lithium ion battery: A negative electrode plate was provided, which was prepared by coating a mixed paste, that contains graphite: conductive agent (carbon black): binder (e.g., SBR): water at a weight ratio of 100:2:5:120 on a copper foil, and drying. A positive electrode sheet prepared with the positive electrode active material LFP-3 in Example 1 was used as a positive electrode. A polypropylene film was used as a separator. A solution containing 1.0 mol/L LiPF6 in ethylene carbonate (EC): dimethyl carbonate (DMC) at a volume ratio of 1:1 was used as an electrolyte solution. After assembly, a pouch lithium ion battery was obtained.
A method for preparing a lithium iron phosphate positive electrode active material was different from the method in Example 1 in that the LFP-1 material and the LFP-2 material were mixed at a weight ratio of 4:6. The other steps were the same as those in Example 1. A lithium iron phosphate positive electrode active material LFP-3 was obtained.
Following the method described in Example 1, the lithium iron phosphate positive electrode active material LFP-3 obtained in Example 2 was prepared into a positive electrode sheet, and assembled into a pouch lithium ion battery. The maximum compaction density of the positive electrode sheet in Example 2 was determined to be 2.68 g/cm3.
A method for preparing a lithium iron phosphate positive electrode active material includes the following steps.
A first lithium iron phosphate material LFP-1 was used. When a particle size of particles of LFP-1 that have the largest volume distribution value of LFP-1, the corresponding particle size was 3.12 μm, and the distribution discreteness in particle size was 2.92. That is, D1mo was 3.12, A1 was 2.92, and A1×(2.31+D1mo)=15.86. A second lithium iron phosphate material LFP-2 was used. When a particle size of particles of LFP-2 that have the largest volume distribution value of LFP-2, the corresponding particle size was 4.93 μm, and the distribution discreteness in particle size was 3.69. That is, D2mo was 4.93, A2 was 3.69, and A2×(D2mo−1.15)=13.95.
The LFP-1 material and the LFP-2 material were mixed at a weight ratio of 5:5. A lithium iron phosphate positive electrode active material LFP-3 was obtained.
Following the method described in Example 1, the lithium iron phosphate positive electrode active material LFP-3 obtained in Example 3 was prepared into a positive electrode sheet, and assembled into a pouch lithium ion battery. The maximum compaction density of the positive electrode sheet in Example 3 was determined to be 2.73 g/cm3.
A method for preparing a lithium iron phosphate positive electrode active material includes the following steps.
A first lithium iron phosphate material LFP-1 was used. When a particle size of particles of LFP-1 that have the largest volume distribution value of LFP-1, the corresponding particle size was 1.41 μm, and the distribution discreteness in particle size was 2.32. That is, D1mo was 1.41, A1 was 2.32, and A1×(2.31+D1mo)=8.63. A second lithium iron phosphate material LFP-2 was used. When a particle size of particles of LFP-2 that have the largest volume distribution value of LFP-2, the corresponding particle size was 3.36 μm, and the distribution discreteness in particle size was 2.58. That is, D2mo was 3.36, A2 was 2.58, and A2×(D2mo−1.15)=5.70.
The LFP-1 material and the LFP-2 material were mixed at a weight ratio of 3:7. A lithium iron phosphate positive electrode active material LFP-3 was obtained.
Following the method described in Example 1, the lithium iron phosphate positive electrode active material LFP-3 obtained in Example 4 was prepared into a positive electrode sheet, and assembled into a pouch lithium ion battery. The maximum compaction density of the positive electrode sheet in Example 4 was determined to be 2.68 g/cm3.
A method for preparing a lithium iron phosphate positive electrode active material includes the following steps.
A first lithium iron phosphate material LFP-1 was used. When a particle size of particles of LFP-1 that have the largest volume distribution value of LFP-1, the corresponding particle size was 2.46 μm, and the distribution discreteness in particle size was 2.16. That is, D1mo was 2.46, A1 was 2.16, and A1×(2.31+D1mo)=10.30. A second lithium iron phosphate material LFP-2 was used. When a particle size of particles of LFP-2 that have the largest volume distribution value of LFP-2, the corresponding particle size was 4.48 μm, and the distribution discreteness in particle size was 3.92. That is, D2mo was 4.48 μm, A2 was 3.92, and A2×(D2mo−1.15)=13.05.
The LFP-1 material and the LFP-2 material were mixed at a weight ratio of 7:3. A lithium iron phosphate positive electrode active material LFP-3 was obtained.
Following the method described in Example 1, the lithium iron phosphate positive electrode active material LFP-3 obtained in Example 5 was prepared into a positive electrode sheet, and assembled into a pouch lithium ion battery. The maximum compaction density of the positive electrode sheet in Example 5 was determined to be 2.65 g/cm3.
A method for preparing a lithium iron phosphate positive electrode active material includes the following steps.
A first lithium iron phosphate material LFP-1 was used. When a particle size of particles of LFP-1 that have the largest volume distribution value of LFP-1, the corresponding particle size was 0.8 μm, and the distribution discreteness in particle size was 1.32. That is, D1mo was 0.8, A1 was 1.32, and A1×(2.31+D1mo)=4.11. A second lithium iron phosphate material LFP-2 was used. When a particle size of particles of LFP-2 that have the largest volume distribution value of LFP-2, the corresponding particle size was 1.65 μm, and the distribution discreteness in particle size was 3.6. That is, D2mo was 1.65, A2 was 3.6, and A2×(D2mo−1.15)=1.8.
The LFP-1 material and the LFP-2 material were mixed at a weight ratio of 3:7. A lithium iron phosphate positive electrode active material LFP-3 was obtained.
Following the method described in Example 1, the lithium iron phosphate positive electrode active material LFP-3 obtained in Example 6 was prepared into a positive electrode sheet, and assembled into a pouch lithium ion battery. The maximum compaction density of the positive electrode sheet in Example 6 was determined to be 2.66 g/cm3.
A method for preparing a lithium iron phosphate positive electrode active material includes the following steps.
A first lithium iron phosphate material LFP-1 was used. When a particle size of particles of LFP-1 that have the largest volume distribution value of LFP-1, the corresponding particle size was 0.64 μm, and the distribution discreteness in particle size was 2.8. That is, D1mo was 0.64, A1 was 2.8, and A1×(2.31+D1mo)=8.26. A second lithium iron phosphate material LFP-2 was used. When a particle size of particles of LFP-2 that have the largest volume distribution value of LFP-2, the corresponding particle size was 1.02 μm, and the distribution discreteness in particle size was 2.94. That is, D2mo was 1.02, A2 was 2.94, and A2×(D2mo−1.15)=−0.38;
The LFP-1 material and the LFP-2 material were mixed at a weight ratio of 6:4. A lithium iron phosphate positive electrode active material LFP-3 was obtained.
Following the method described in Example 1, the lithium iron phosphate positive electrode active material LFP-3 obtained in Example 7 was prepared into a positive electrode sheet, and assembled into a pouch lithium ion battery. The maximum compaction density of the positive electrode sheet in Example 7 was determined to be 2.65 g/cm3.
To highlight the beneficial effects of the present disclosure, the following Comparative Examples 1-6 are provided.
A method for preparing a lithium iron phosphate positive electrode active material includes the following steps:
A first lithium iron phosphate material LFP-1 was used. When a particle size of particles of LFP-1 that have the largest volume distribution value of LFP-1, the corresponding particle size was 0.35 μm (that is, D1mo was 0.35), the distribution discreteness A1 in particle size was 1.27, but A1×(2.31+D1mo)=3.38, which fell outside the range of (4.07, 16) configured in the present disclosure. A second lithium iron phosphate material LFP-2 was used. When a particle size of particles of LFP-2 that have the largest volume distribution value of LFP-2, the corresponding particle size was 1.03 μm (that is, D2mo was 1.03), the distribution discreteness A2 in particle size was 3.87, but A2×(D2mo−1.15)=−0.46, which fell outside the range of (−0.4, 14) configured in the present disclosure.
The LFP-1 material and the LFP-2 material were mixed at a weight ratio of 1:1. A lithium iron phosphate positive electrode active material LFP-3 was obtained.
Following the method described in Example 1, the lithium iron phosphate positive electrode active material LFP-3 obtained in Comparative Example 1 was prepared into a positive electrode sheet, and assembled into a pouch lithium ion battery. The maximum compaction density of the positive electrode sheet in Comparative Example 1 was determined to be 2.58 g/cm3.
A lithium iron phosphate positive electrode material was provided, in which one lithium iron phosphate material was used as the positive electrode active material. When the volume of particles having a particle size of the lithium iron phosphate material is the largest volume among all the particles having different sizes, the corresponding particle size was 0.31 μm, and the distribution discreteness A in particle size was 1.92.
Following the method described in Example 1, the lithium iron phosphate positive electrode material obtained in Comparative Example 2 was prepared into a positive electrode sheet, and assembled into a pouch lithium ion battery. The maximum compaction density of the pouch battery was 2.55 g/cm3.
A method for preparing a lithium iron phosphate positive electrode active material includes the following steps.
A first lithium iron phosphate material LFP-1 was used. When a particle size of particles of LFP-1 that have the largest volume distribution value of LFP-1-, the corresponding particle size was 0.35 μm (that is, D1mo was 0.35), the distribution discreteness A1 in particle size was 1.24, but A1×(2.31+D1mo)=3.30, which fell outside the range of (4.07, 16) configured in the present disclosure. A second lithium iron phosphate material LFP-2 was used. When a particle size of particles of LFP-2 that have the largest volume distribution value of LFP-2, the corresponding particle size was 5.11 μm (that is, D2mo was 5.11) which fell outside the range of (1,5) configured in the present disclosure, the distribution discreteness A2 in particle size was 3.78, and A2×(D2mo−1.15)=14.97, which fell outside the range of (−0.4, 14) configured in the present disclosure.
The LFP-1 material and the LFP-2 material were mixed at a weight ratio of 2:8. A lithium iron phosphate positive electrode active material LFP-3 was obtained.
Following the method described in Example 1, the positive electrode active material LFP-3 obtained in Comparative Example 3 was prepared into a positive electrode sheet, and assembled into a pouch battery. The maximum compaction density of the positive electrode sheet in Comparative Example 3 was determined to be 2.63 g/cm3. Although the maximum compaction density of the positive electrode sheet in Comparative Example 3 reached 2.6 g/cm3 or higher, the charge-discharge cycle stability of the battery was poor. As shown in Table 1 below, the first-cycle coulombic efficiency, the first-cycle discharge specific capacity, and the capacity retention rate after 1000 cycles of a battery having the positive electrode sheet in Comparative Example 3 were lower than those in Example 1.
A method for preparing a lithium iron phosphate positive electrode active material includes the following steps:
A first lithium iron phosphate material LFP-1 was used. When a particle size of particles of LFP-1 that have the largest volume distribution value of LFP-1, the corresponding particle size was 0.46 μm (that is, D1mo was 0.46), the distribution discreteness A1 in particle size was 1.22, but A1×(2.31+D1mo)=3.38, which fell outside the range of (4.07, 16) configured in the present disclosure. A second lithium iron phosphate material LFP-2 was used. When a particle size of particles of LFP-2 that have the largest volume distribution value of LFP-2, the corresponding particle size was 1.47 μm (that is, D2mo was 1.47), the distribution discreteness A2 in particle size was 2.66, and A2×(D2mo−1.15)=0.85, which fell outside the range of (−0.4,14) configured in the present disclosure.
The LFP-1 material and the LFP-2 material were mixed at a weight ratio of 3:7. A lithium iron phosphate positive electrode active material LFP-3 was obtained.
Following the method described in Example 1, the lithium iron phosphate positive electrode active material LFP-3 obtained in Comparative Example 4 was prepared into a positive electrode sheet, and assembled into a pouch lithium ion battery. The maximum compaction density of the positive electrode sheet in Comparative Example 4 was determined to be merely 2.57 g/cm3.
A method for preparing a lithium iron phosphate positive electrode active material includes the following steps.
A first lithium iron phosphate material LFP-1 was used. When a particle size of particles of LFP-1 that have the largest volume distribution value of LFP-1, the corresponding particle size was 3.1 μm (that is, D1mo was 3.1) which fell outside the range of 0.3-3.2 μm configured in the present disclosure, the distribution discreteness A1 in particle size was 2.58, and A1×(2.31+D1mo)=13.96. A second lithium iron phosphate material LFP-2 was used. When a particle size of particles of LFP-2 that have the largest volume distribution value of LFP-2, the corresponding particle size was 5.23 μm (that is, D2mo was 5.23) which fell outside the range of (1,5) configured in the present disclosure, the distribution discreteness A2 in particle size was 3.29, and A2×(D2mo−1.15)=13.42, which fell outside the range of (−0.4,14) configured in the present disclosure.
The LFP-1 material and the LFP-2 material were mixed at a weight ratio of 5:5. A lithium iron phosphate positive electrode active material LFP-3 was obtained.
Following the method described in Example 1, the lithium iron phosphate positive electrode active material LFP-3 obtained in Comparative Example 5 was prepared into a positive electrode sheet, and assembled into a pouch lithium ion battery. The maximum compaction density of the positive electrode sheet in Comparative Example 5 was determined to be 2.62 g/cm3. Although the maximum compaction density of the positive electrode sheet in Comparative Example 5 reached 2.6 g/cm3 or higher, the charge-discharge cycle stability of the battery was poor. As shown in Table 1 below, the first-cycle coulombic efficiency, the first-cycle discharge specific capacity, and the capacity retention rate after 1000 cycles of a battery having the positive electrode sheet in Comparative Example 5 were lower than those in Example 1.
A method for preparing a lithium iron phosphate positive electrode active material includes the following steps.
A first lithium iron phosphate material LFP-1 was used. When a particle size of particles of LFP-1 that have the largest volume distribution value of LFP-1, the corresponding particle size was 0.54 μm (that is, D1mo was 0.54), the distribution discreteness A1 in particle size was 1.87, and A1×(2.31+D1mo)=5.33. A second lithium iron phosphate material LFP-2 was used. When a particle size of particles of LFP-2 that have the largest volume distribution value of LFP-2, the corresponding particle size was 1.12 μm (that is, D2mo was 1.12), the distribution discreteness A2 in particle size was 1.61 which fell outside the range of 2-4 configured in the present disclosure, and A2×(D2mo−1.15)=−0.05.
The LFP-1 material and the LFP-2 material were mixed at a weight ratio of 6:4. A lithium iron phosphate positive electrode active material LFP-3 was obtained.
Following the method described in Example 1, the lithium iron phosphate positive electrode active material LFP-3 obtained in Comparative Example 6 was prepared into a positive electrode sheet, and assembled into a pouch lithium ion battery. The maximum compaction density of the positive electrode sheet in Comparative Example 6 was determined to be 2.54 g/cm3.
To provide powerful support for the beneficial effects of the present disclosure, the cycle performance of the pouch battery of each example and comparative example was tested. Each pouch battery was subjected to charge-discharge cycle test at 0.5 C/0.5 C at 25° C. The voltage range was 2.0-3.8 V.
As can be seen from
The foregoing embodiments show several implementations of the present disclosure and are described in detail, which, however, do not limit the scope of the present disclosure. It is to be understood that for a person of ordinary skill in the art, several variations and improvements can be made by those of ordinary skill in the art without departing from the idea of the present disclosure, which are all contemplated in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202210228274.0 | Mar 2022 | CN | national |
This application is a continuation application of International Patent Application No. PCT/CN2023/077668, filed on Feb. 22, 2023, which is based on and claims the priority to and benefits of Chinese Patent Application No. 202210228274.0 filed on Mar. 7, 2022. The entire content of all of the above-referenced applications is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2023/077668 | Feb 2023 | WO |
| Child | 18815154 | US |
