Modification grading process of lithium ion battery positive electrode material
By using cyclone grading and modification treatment of lithium iron phosphate materials, the problem of uneven particle size distribution was solved, improving the compaction density and rate performance of lithium iron phosphate batteries, making them suitable for high energy density and high power lithium-ion batteries.
Patent Information
- Application Number
- CN202511191646.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-25
- Publication Date
- 2025-11-21
AI Technical Summary
The existing lithium iron phosphate battery manufacturing process is complex, and the uneven particle size distribution leads to high internal resistance and low energy density, making it difficult to meet the requirements of high-performance lithium-ion batteries.
Lithium iron phosphate materials are separated into large, medium and small particles by cyclone grading. The large and medium particles are then modified to optimize the gradation ratio, form a dense packing structure, reduce internal resistance and improve energy density.
It significantly improves the compaction density and rate performance of lithium iron phosphate materials, enhances the energy density and consistency of batteries, and is suitable for large-scale stable production.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of lithium ion batteries, and particularly relates to a modification grading process of a lithium ion battery positive electrode material. BACKGROUND
[0002] With the increasing depletion of fossil energy such as oil, coal and natural gas, the technology of rechargeable lithium ion batteries (LIBs) has attracted extensive attention from global researchers as a key solution for clean energy storage. Among a large number of positive electrode materials, lithium iron phosphate (LiFePO4) has become the mainstream choice for electric vehicles and energy storage systems due to its excellent cycle stability, excellent safety performance and green environmental protection characteristics. However, with the continuous improvement of the performance requirements of the battery by the new energy industry, the development of lithium iron phosphate materials with higher energy density has become an important direction for the research and development of the next generation of lithium ion batteries.
[0003] In this process of technological upgrading, researchers mainly improve the material performance by optimizing the raw material preparation process and improving the material formula. Although these innovations have significantly improved the electrochemical performance of lithium iron phosphate, they have inevitably increased the complexity of the production process and significantly raised the technical threshold. In particular, in the process of industrialized production, these complex process control requirements introduce many uncertainties, bringing severe challenges to the large-scale stable production of products. SUMMARY
[0004] Among the many key performance indicators of lithium iron phosphate materials, the uniformity of the particle size distribution has a crucial influence on the battery performance. Research has found that in the particle size distribution of lithium iron phosphate, large particles have greater internal resistance and lower capacity than small particles, thus exhibiting greater internal resistance and poorer kinetic performance at the battery end. This phenomenon directly affects the energy density and rate performance of the battery and has become one of the key factors restricting the development of high-performance lithium iron phosphate batteries. The process route of the present application, which involves grading, screening out large particles or medium particles, modifying them and then re-grading, can significantly improve the compaction of the material, reduce the internal resistance and improve the specific capacity. The specific scheme is as follows: A modification grading process of a lithium ion battery positive electrode material, comprising the following steps: (1) mixing iron phosphate, lithium source, carbon source, titanium source and water, grinding, spray drying, and calcining at 700-850°C in an inert atmosphere for 7-15 hours to obtain lithium iron phosphate A; (2) classifying the lithium iron phosphate A into three kinds of particles by cyclone classification: large particles A1 with a D50 of 1.3-2.0 μm, medium particles A2 with a D50 of 0.9-1.3 μm, and small particles A3 with a D50 of 0.6-0.9 μm; (3), the large particle A1, the medium particle A2 are mixed with the modified additive respectively, and after calcination in inert atmosphere, the particle size is crushed to 0.8-1.3 μm, and the modified large particle A1 and the modified medium particle A2 are obtained respectively; (4), the modified large particle A1, the modified medium particle A2 and the small particle A3 are mixed in the weight ratio of modified large particle A1: modified medium particle A2: small particle A3=x:y:z, and the lithium iron phosphate product is obtained; Wherein, x+y+z=100%, 20%≤x≤70%, 0%≤y≤60%, 20%≤z≤70%.
[0005] Moreover, in step (1), the mass ratio of iron phosphate: lithium source: carbon source: titanium source: water is 1:0.20-0.30:0.10-0.20:0.001-0.005:1.5-2.5.
[0006] Moreover, in step (1), the lithium source is one or more combinations of lithium carbonate, lithium hydroxide, lithium phosphate, lithium dihydrogen phosphate.
[0007] Moreover, in step (1), the carbon source is one or more combinations of glucose, polyethylene glycol, sucrose, starch, maltose.
[0008] Moreover, in step (1), the titanium source is one or more combinations of titanium dioxide, titanyl sulfate, titanium tetrachloride, tetrabutyl titanate, tetraethyl titanate.
[0009] Moreover, in step (1), the particle size D50 of the ground material is 0.35-0.45 μm.
[0010] Moreover, in step (3), the modified additive is one or more combinations of titanium compounds, magnesium compounds, vanadium compounds, aluminum compounds, glucose, polyethylene glycol, sucrose, starch, maltose.
[0011] Moreover, in step (3), the weight ratio of large particle A1 to modified additive is 1:0.002-0.05, and the weight ratio of medium particle A2 to modified additive is 1:0.002-0.05.
[0012] Moreover, in step (3), the calcination temperature is 600-800℃, and the calcination time is 4-12 hours.
[0013] On the other hand, the present application provides a lithium ion battery positive electrode material prepared by the modification and grading process of the lithium ion battery positive electrode material, and the compaction density of the lithium ion battery positive electrode material is 2.55-2.65 g / cm³, and the 0.5C discharge specific capacity is ≥145 mAh / g.
[0014] Compared with the prior art, the present application has the following advantages: 1、The present application divides the lithium iron phosphate material into large particles A1, medium particles A2 and small particles A3 by cyclone grading, and modifies the large and medium particles, optimizes the grading ratio, and makes the particles of different sizes form a more compact packing structure, thereby significantly improving the compaction density of the material (2.55-2.65 g / cm³) and improving the energy density of the electrode.
[0015] 2、In the traditional lithium iron phosphate material, the large particles have high internal resistance due to long lithium ion diffusion path and poor conductivity. The present application modifies the surface of the large and medium particles to enhance their conductivity and shorten the lithium ion transmission path, thereby reducing the overall internal resistance and improving the rate performance.
[0016] 3、The present application precisely controls the particle grading ratio: large particles 20-70%, medium particles 0-60%, and small particles 20-70%, and combines modification treatment, so that the specific capacity of the material is ≥145 mAh / g under 0.5C discharge conditions, which is better than the conventional ungraded or single particle size distribution lithium iron phosphate material.
[0017] 4、In the traditional process, uneven particle distribution easily leads to batch performance fluctuations. The process route of grading + modification + grading in the present application can accurately control the particle distribution, reduce batch differences, improve product consistency, and is more suitable for large-scale stable production.
[0018] 5、The present application can flexibly adapt to different application scenarios such as high energy density power batteries or high power energy storage batteries by adjusting the grading ratio and modification process, thereby improving the market competitiveness of lithium iron phosphate materials. BRIEF DESCRIPTION OF DRAWINGS
[0019] Figure 1 The particle size distribution graph of the lithium iron phosphate finished product in Example 1; Figure 2 The particle size distribution graph of the lithium iron phosphate finished product in Example 2; Figure 3 The particle size distribution graph of the lithium iron phosphate finished product in Example 3; Figure 4 The particle size distribution graph of the lithium iron phosphate finished product in Comparative Example 2. DETAILED DESCRIPTION
[0020] Example 1 A modification grading process for a lithium ion battery positive electrode material, comprising the following steps: (1) Mix iron phosphate, lithium source, carbon source, titanium source and water, grind, spray dry, and calcine at 800℃ in an inert atmosphere for 12 hours, and then crush to obtain lithium iron phosphate A; (2), the lithium iron phosphate A is divided into three kinds of particles by cyclone grading: large particles A1 with D50 of 1.4 μm, medium particles A2 with D50 of 1.1 μm, and small particles A3 with D50 of 0.8 μm; (3), the large particles A1 and the medium particles A2 are mixed with modified additives respectively, and after calcination in an inert atmosphere, they are crushed to D50 of 1.1 μm, to obtain modified large particles A1 and modified medium particles A2 respectively; (4), the modified large particles A1, the modified medium particles A2 and the small particles A3 are mixed in a weight ratio of modified large particles A1: modified medium particles A2: small particles A3 = x:y:z to obtain the finished lithium iron phosphate; Wherein, x+y+z=100%, x=30%, y=30%, z=40%.
[0021] Further, in step (1), the mass ratio of iron phosphate: lithium source: carbon source: titanium source: water is 1:0.25:0.11:0.002:2.0.
[0022] Further, in step (1), the lithium source is lithium carbonate.
[0023] Further, in step (1), the carbon source is glucose.
[0024] Further, in step (1), the titanium source is titanium dioxide.
[0025] Further, in step (1), the particle size of the ground material is 0.42 μm.
[0026] Further, in step (3), the modified additive is titanium dioxide.
[0027] Further, in step (3), the weight ratio of large particles A1 to modified additive is 1:0.016, and the weight ratio of medium particles A2 to modified additive is 1:0.016.
[0028] Further, in step (3), the calcination temperature is 700°C, and the calcination time is 8 hours.
[0029] The particle size distribution of the finished lithium iron phosphate is shown in Figure 1 The peak types of large particles, medium particles, small particles and finished products are shown, and the left peak becomes higher as the particle size becomes smaller.
[0030] The compaction density of the finished lithium iron phosphate is 2.60 g / cm 3The lithium iron phosphate product is used as a positive electrode material to assemble a 2430 button cell for electrochemical performance test. The battery is tested at a discharge cut-off voltage of 2.5V and a charge cut-off voltage of 4.2V, and the 0.5C capacity is 147mAh / g. The battery is tested at a discharge cut-off voltage of 2.0V and a charge cut-off voltage of 3.75V, and the DCR value of 20% SOC is 28Ω.
[0031] Example 2 A modification grading process of a lithium ion battery positive electrode material, comprising the following steps: (1) mixing iron phosphate, lithium source, carbon source, titanium source and water, grinding, and then spray drying, and then calcining at 790℃ in an inert atmosphere for 13 hours, and then crushing to obtain lithium iron phosphate A; (2) classifying the lithium iron phosphate A into three kinds of particles by cyclone classification: large particles A1 with a D50 of 1.35μm, medium particles A2 with a D50 of 1.16μm, and small particles A3 with a D50 of 0.85μm; (3) mixing the large particles A1 and the medium particles A2 with a modification additive respectively, and then crushing to a D50 of 1.15μm after calcining in an inert atmosphere, to obtain modified large particles A1 and modified medium particles A2 respectively; (4) grading and mixing the modified large particles A1, the modified medium particles A2 and the small particles A3 in a weight ratio of modified large particles A1:modified medium particles A2:small particles A3=x:y:z to obtain a lithium iron phosphate product; wherein x+y+z=100%, x=20%, y=20%, and z=60%.
[0032] Further, in step (1), the iron phosphate, lithium source, carbon source, titanium source and water are mixed in a mass ratio of 1:0.26:0.13:0.002:2.4.
[0033] Further, in step (1), the lithium source is one or more combinations of lithium carbonate, lithium hydroxide, lithium phosphate, and lithium dihydrogen phosphate.
[0034] Further, in step (1), the carbon source is glucose, sucrose, or starch.
[0035] Further, in step (1), the titanium source is one or more combinations of titanium dioxide, titanyl sulfate, titanium tetrachloride, tetrabutyl titanate, and tetraethyl titanate.
[0036] Further, in step (1), the particle size of the material after grinding is 0.40μm.
[0037] Further, in step (3), the modification additive is one or more combinations of titanium compounds, magnesium compounds, vanadium compounds, aluminum compounds, glucose, polyethylene glycol, sucrose, starch, and maltose.
[0038] Further, in step (3), the weight ratio of large particles A1 to the modification additive is 1:0.020, and the weight ratio of medium particles A2 to the modification additive is 1:0.020.
[0039] Further, in step (3), the calcination temperature is 750°C, and the calcination time is 5 hours.
[0040] The particle size distribution of the finished lithium iron phosphate product is shown in Figure 2 The peak types of large particles, medium particles, small particles, and finished products are shown, and the left peak becomes higher as the particles become smaller.
[0041] The finished lithium iron phosphate product has a tap density of 2.58 g / cm 3 The finished lithium iron phosphate product is used as a positive electrode material to assemble 2430 button cells for electrochemical performance testing. The battery is tested at a discharge cutoff voltage of 2.5V and a charge cutoff voltage of 4.2V, and the 0.5C capacity is 146 mAh / g. The battery is tested at a discharge cutoff voltage of 2.0V and a charge cutoff voltage of 3.75V, and the 20% SOC DCR value is 33Ω.
[0042] Example 3 A modification grading process for a lithium ion battery positive electrode material includes the following steps: (1) Mix iron phosphate, lithium source, carbon source, titanium source, and water, grind, and spray dry, then calcine at 840°C in an inert atmosphere for 14 hours, and crush to obtain lithium iron phosphate A; (2) Divide the lithium iron phosphate A into three types of particles by cyclone classification: large particles A1 with a D50 of 1.5μm, medium particles A2 with a D50 of 1.0μm, and small particles A3 with a D50 of 0.8μm; (3) Mix the large particles A1 and the medium particles A2 with a modification additive, calcine in an inert atmosphere, and crush to a D50 of 1.0μm to obtain modified large particles A1 and modified medium particles A2, respectively; (4) Grading mix the modified large particles A1, the modified medium particles A2, and the small particles A3 in a weight ratio of modified large particles A1:modified medium particles A2:small particles A3=x:y:z to obtain a finished lithium iron phosphate product; Wherein, x+y+z=100%, x=30%, y=40%, and z=30%.
[0043] Further, in step (1), the iron phosphate, lithium source, carbon source, titanium source and water are mixed in a mass ratio of 1:0.30:0.20:0.005:2.5.
[0044] Further, in step (1), the lithium source is lithium carbonate, lithium hydroxide, lithium phosphate, lithium dihydrogen phosphate.
[0045] Further, in step (1), the carbon source is glucose, polyethylene glycol.
[0046] Further, in step (1), the titanium source is titanium dioxide, titanyl sulfate, titanium tetrachloride.
[0047] Further, in step (1), the particle size of the ground material is 0.40 μm.
[0048] Further, in step (3), the modification additive is a titanium compound, a vanadium compound, glucose.
[0049] Further, in step (3), the weight ratio of large particles A1 to modification additive is 1:0.05, and the weight ratio of medium particles A2 to modification additive is 1:0.05.
[0050] Further, in step (3), the calcination temperature is 800°C, and the calcination time is 12 hours.
[0051] The particle size distribution of the finished lithium iron phosphate product is shown in Figure 3 The peak types of large particles, medium particles, small particles and finished product are shown, and the left peak becomes higher as the particle size becomes smaller.
[0052] The compaction density of the finished lithium iron phosphate product is 2.62 g / cm 3 The finished lithium iron phosphate product is used as a positive electrode material to assemble 2430 button cells for electrochemical performance testing. The battery is tested at a discharge cutoff voltage of 2.5V and a charge cutoff voltage of 4.2V, and the 0.5C capacity is 145 mAh / g. The battery is tested at a discharge cutoff voltage of 2.0V and a charge cutoff voltage of 3.75V, and the 20% SOC DCR value is 30Ω.
[0053] Comparative Example 1 The difference between this comparative example and Example 1 is that no grading is performed, as follows: Iron phosphate, lithium carbonate, glucose, titanium dioxide and water are weighed and mixed in a weight ratio of 1:0.25:0.11:0.002:2.0, ground to a slurry particle size of 0.42 μm, and after spray drying, calcined at 800°C under a nitrogen atmosphere for 12 hours and crushed to obtain a finished lithium iron phosphate product.
[0054] The tap density of the lithium iron phosphate product was tested using the Think Laterally equipment and was 2.53 g / cm3 3 The lithium iron phosphate product was simultaneously used as a positive electrode material to assemble 2430 button cells for electrochemical performance testing. The battery was tested at a discharge cut-off voltage of 2.5 V and a charge cut-off voltage of 4.2 V, and the 0.5C capacity was 141 mAh / g. The battery was tested at a discharge cut-off voltage of 2.0 V and a charge cut-off voltage of 3.75 V, and the DCR value at 20% SOC was 35 Ω.
[0055] Comparative Example 2 The main difference between this comparative example and Example 1 is that the initial particles are larger (large particles D50 = 2.3 pm, medium particles 1.8 pm, and small particles 1.3 pm), as follows: Phosphorus iron, lithium carbonate, glucose, titanium dioxide, and water were weighed according to the weight ratio of 1:0.25:0.11:0.002:2.0 and mixed in water, and the slurry particle size was controlled at 0.50 pm after grinding. After spray drying, crushing was performed after calcination at 840 °C under a nitrogen atmosphere for 12 hours, and lithium iron phosphate C with a certain particle size distribution was obtained. Using cyclone classification, large particles C1 with a particle size D50 of 2.3 pm, medium particles C2 with a particle size D50 of 1.8 pm, and small particles C3 with a particle size D50 of 1.3 pm were obtained, and the weight proportions were 35%, 35%, and 30%, respectively. The large particles C1 and the titanium compound (titanium dioxide) were mixed according to a weight ratio of 1:0.016, and crushing was performed after calcination at 750 °C under an inert atmosphere for 8 hours. The medium particles C2 and the titanium compound (titanium dioxide) were mixed according to a weight ratio of 1:0.016, and crushing was performed after calcination at 750 °C under an inert atmosphere for 8 hours. The modified large particles, the modified medium particles, and the small particles were mixed according to a weight proportion of 35%, 35%, and 30%, respectively, to obtain a lithium iron phosphate product, and the particle size distribution is shown in Figure 4 The peak types of the large particles, the medium particles, the small particles, and the product are shown, and the left peak becomes higher as the particles become smaller.
[0056] The tap density of the lithium iron phosphate product was tested using the Think Laterally equipment and was 2.63 g / cm3, and the lithium iron phosphate product was simultaneously used as a positive electrode material to assemble 2430 button cells for electrochemical performance testing. The battery was tested at a discharge cut-off voltage of 2.5 V and a charge cut-off voltage of 4.2 V, and the 0.5C capacity was 142 mAh / g. The battery was tested at a discharge cut-off voltage of 2.0 V and a charge cut-off voltage of 3.75 V, and the DCR value at 20% SOC was 38 Ω.
[0057] Comparative Example 3 The comparative example is prepared by the same method as example 1, the main difference being that in step (3) the modified large particles, modified medium particles and modified small particles are mixed in a weight ratio of 10%, 10% and 80% to obtain the finished product.
[0058] The test method is the same as example 1, the compaction density is 2.54, the 0.5C capacity is 147mAh / g, and the DCR value at 20% SOC is 34Ω.
[0059] Comparative example 4 The comparative example is prepared by the same method as example 1, the main difference being that in step (3) the modified large particles, modified medium particles and modified small particles are mixed in a weight ratio of 5%, 45% and 50% to obtain the finished product.
[0060] The test method is the same as example 1, the compaction density is 2.54, the 0.5C capacity is 145mAh / g, and the DCR value at 20% SOC is 35Ω.
[0061] Comparative example 5 The comparative example is prepared by the same method as example 1, the main difference being that in step (3) the medium particles and the titanium compound (titanium dioxide) are mixed in a weight ratio of 1:0.001 to obtain the finished product.
[0062] The test method is the same as example 1, the compaction density is 2.57, the 0.5C capacity is 144mAh / g, and the DCR value at 20% SOC is 36Ω.
[0063] Comparative example 6 The comparative example is prepared by the same method as example 1, the main difference being that in step (3) the medium particles and the titanium compound (titanium dioxide) are mixed in a weight ratio of 1:0.06 to obtain the finished product.
[0064] The test method is the same as example 1, the compaction density is 2.53, the 0.5C capacity is 148mAh / g, and the DCR value at 20% SOC is 32Ω.
[0065] Table 1 Performance comparison
[0066] The compaction density in the comparative examples = 2.55-2.65g / cm 3 and the 0.5C capacity ≥145mAh / g cannot be met at the same time, and the DCR at 20% SOC of comparative examples 1-5 is higher than that of the examples.
Claims
1. A process for modifying the grading of a lithium-ion battery cathode material, characterized in that, The method comprises the following steps: (1) mixing iron phosphate, a lithium source, a carbon source, a titanium source and water, grinding, spray drying, calcining at 700-850 DEG C in an inert atmosphere for 7-15 hours, and crushing to obtain lithium iron phosphate A; (2) classifying lithium iron phosphate A into three kinds of particles by cyclone classification: large particles A1 with D50 of 1.3-2.0 μm, medium particles A2 with D50 of 0.9-1.3 μm, and small particles A3 with D50 of 0.6-0.9 μm; (3) mixing large particles A1 and medium particles A2 with modified additives respectively, calcining in an inert atmosphere, and crushing to D50 of 0.8-1.3 μm to obtain modified large particles A1 and modified medium particles A2 respectively; (4) grading and mixing modified large particles A1, modified medium particles A2 and small particles A3 according to the weight ratio of modified large particles A1: modified medium particles A2: small particles A3 = x: y: z to obtain finished lithium iron phosphate; Wherein, x + y + z = 100%, 20% ≤ x ≤ 70%, 0% ≤ y ≤ 60%, 20% ≤ z ≤ 70%.
2. The process for modifying the grading of lithium-ion battery cathode materials as claimed in claim 1, wherein, In step (1), the mass ratio of iron phosphate: lithium source: carbon source: titanium source: water is 1: 0.20-0.30: 0.10-0.20: 0.001-0.005: 1.5-2.
5.
3. The process for modifying the grading of lithium-ion battery cathode materials as claimed in claim 1, wherein, In step (1), the lithium source is one or more combinations of lithium carbonate, lithium hydroxide, lithium phosphate, and lithium dihydrogen phosphate.
4. The process for modifying the grading of lithium-ion battery cathode materials of claim 1, wherein, In step (1), the carbon source is one or more combinations of glucose, polyethylene glycol, sucrose, starch, and maltose.
5. The process for modifying the grading of lithium-ion battery cathode materials as claimed in claim 1, wherein, In step (1), the titanium source is one or more combinations of titanium dioxide, titanium sulfate, titanium tetrachloride, tetrabutyl titanate, and tetraethyl titanate.
6. The process for modifying the grading of lithium-ion battery cathode materials of claim 1, wherein, In step (1), the particle size D50 of the material after grinding is 0.35-0.45 μm.
7. The process for modifying the grading of lithium-ion battery cathode materials as claimed in claim 1, wherein, In step (3), the modified additive is one or more combinations of titanium compounds, magnesium compounds, vanadium compounds, aluminum compounds, glucose, polyethylene glycol, sucrose, starch, and maltose.
8. The process for modifying the grading of lithium-ion battery cathode materials as claimed in claim 1, wherein, In step (3), the weight ratio of large particles A1 to modified additives is 1: 0.002-0.05, and the weight ratio of medium particles A2 to modified additives is 1: 0.002-0.
05.
9. The process for modifying the grading of lithium-ion battery cathode materials as claimed in claim 1, wherein, In step (3), the calcination temperature is 600-800 DEG C, and the calcination time is 4-12 hours.
10. A lithium-ion battery cathode material prepared by a modified gradation process according to any one of claims 1-9, characterized in that, The compaction density of the lithium ion battery positive electrode material is 2.55-2.65 g / cm3, and the 0.5C discharge specific capacity is ≥145 mAh / g.