A lithium supplement additive, Li5FeO4, and its preparation method

Abstract

This invention discloses a lithium supplement additive Li5FeO4 and its preparation method, belonging to the field of lithium-ion battery technology. The preparation method includes the following steps: (1) mixing hydrogen peroxide solution, iron oxide powder, and additive to obtain a mixed dispersion 1; (2) adding lithium hydroxide to the mixed dispersion 1 obtained in step (1) and heating and stirring to obtain a mixed dispersion 2; (3) performing solid-liquid separation on the mixed dispersion 2 obtained in step (2), and washing, milling, drying, low-temperature sintering, high-temperature sintering, and pulverizing the obtained solid to obtain D. 50 The lithium-replenishing additive Li5FeO4 is prepared in the 6-15 μm range. By replenishing missing lithium ions, the Li5FeO4 additive prepared in this invention can effectively improve the energy density of the battery, achieving a coin cell specific capacity of up to 800 mAh / g, an initial charge-discharge efficiency of 93.98%, and a capacity retention rate of over 90% after 50 cycles. This is of great significance for reducing battery replacement frequency and lowering usage costs.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and particularly relates to a lithium supplementation additive Li5FeO4 and its preparation method. Background Technology

[0002] During the initial charge and discharge cycle of a lithium-ion battery, a solid electrolyte interphase (SEI) film forms on the surface of the negative electrode. This process consumes the active lithium in the positive electrode, resulting in the initial loss of specific capacity. Therefore, lithium replenishment is typically used to compensate for this irreversible capacity loss and improve the battery's energy density.

[0003] Currently, common lithium replenishment methods include positive electrode lithium replenishment, negative electrode lithium replenishment, and electrochemical lithium replenishment. Among these, positive electrode lithium replenishment has become the most promising method for industrial production due to its high safety and ease of operation. Commonly used positive electrode lithium replenishment additives include Li5FeO4, Li2NiO2, Li6CoO4, Li6MnO4, and Li5ReO6, etc. Li5FeO4, in particular, can theoretically release five Li ions. + With a theoretical specific capacity of over 850 mAh / g, it is considered an ideal lithium supplement additive for cathode materials. By adding a certain amount of Li5FeO4 to traditional cathode materials, the initial efficiency and energy density of lithium-ion batteries can be significantly improved.

[0004] Existing technologies contain numerous studies on lithium-ion battery additives, such as patents CN 112028126 A and CN118507701 B. However, these all have room for improvement. For instance, CN 112028126 A exhibits a capacity retention rate of less than 90% after cycling, while CN 118507701 B shows a low coin cell specific capacity, less than 600 mAh / g. Therefore, researching, developing, preparing, and using a more advantageous lithium-ion battery additive, Li5FeO4, is of great significance for improving the electrical and rate performance of lithium-ion batteries. Summary of the Invention

[0005] Technical issues

[0006] The lithium supplement additive Li5FeO4 can significantly improve the initial efficiency and energy density of lithium-ion batteries. However, the existing Li5FeO4 lithium supplement additives studied still have room for improvement and optimization. Therefore, there is a need to develop a more advantageous Li5FeO4 lithium supplement additive.

[0007] Technical content

[0008] This invention provides a method for preparing a lithium-supplementing additive, Li5FeO4, comprising the following steps:

[0009] (1) Hydrogen peroxide solution, iron oxide powder and additives are mixed to obtain mixed dispersion 1;

[0010] (2) Add lithium hydroxide to the mixed dispersion 1 obtained in step (1) and heat and stir to obtain mixed dispersion 2;

[0011] (3) The mixed dispersion 2 obtained in step (2) is subjected to solid-liquid separation. The resulting solid is washed, milled, dried, sintered at low temperature, sintered at high temperature, and pulverized to obtain D. 50 Lithium supplementation additive Li5FeO4 in the 6-15μm range.

[0012] Furthermore, the concentration of the hydrogen peroxide solution in step (1) is 10-30 wt%.

[0013] Furthermore, the iron oxide powder in step (1) is at the nanoscale, with a particle size range of 50-100 nm.

[0014] Furthermore, the additives in step (1) include organic carbon sources and aluminum additives.

[0015] Furthermore, organic carbon sources include, but are not limited to, one or more of glucose, sucrose, starch, maltose, citric acid, etc.

[0016] Furthermore, aluminum additives include, but are not limited to, one or more of aluminum isopropoxide, nano aluminum oxide, aluminum hydroxide, and aluminum phosphate.

[0017] Preferably, the organic carbon source is glucose.

[0018] Preferably, the aluminum additive is nano-alumina.

[0019] Furthermore, in step (1), the additive consists of 20-30 wt% organic carbon source and 70-80 wt% aluminum additive.

[0020] Preferably, the additive in step (1) consists of 25-30 wt% organic carbon source and 70-75 wt% aluminum additive.

[0021] Furthermore, in step (1), the mass ratio of iron oxide powder to additive is 30 to 50:1.

[0022] Preferably, the mass ratio of iron oxide powder to additive in step (1) is 35-50:1.

[0023] Furthermore, in step (1), the mass ratio of iron oxide powder to hydrogen peroxide solution is 30-50:450.

[0024] Furthermore, in step (2), the lithium hydroxide is either anhydrous lithium hydroxide or lithium hydroxide monohydrate, and its particle size is 10-20 μm.

[0025] Furthermore, the mass ratio of lithium hydroxide in step (2) to iron oxide powder in step (1) is 3 to 5:1.

[0026] Furthermore, in step (2), the heating temperature for heating and stirring is 55-85℃, and the stirring speed is 150-300r / min.

[0027] Furthermore, the total mass of the mixed dispersion 2 is calculated by adding the masses of iron oxide powder, additives, and lithium hydroxide, wherein the iron oxide powder accounts for 20-25 wt%, the additives account for 0.3-0.6 wt%, and the lithium hydroxide accounts for 75-80 wt%.

[0028] Furthermore, the solvent used for cleaning in step (3) is anhydrous ethanol or anhydrous isopropanol, and the number of cleaning cycles is 3-6.

[0029] Furthermore, in step (3), a solvent needs to be added during the sand milling process. The solvent includes one or more of tetrahydrofuran, N-methylpyrrolidone, anhydrous ethanol, and anhydrous isopropanol.

[0030] Furthermore, in step (3), the rotation speed of the sand mill is in the range of 2000-2800 r / min, and the sand milling time is in the range of 90-150 min.

[0031] Furthermore, the drying in step (3) can be natural air drying, heat drying, or spray drying.

[0032] Furthermore, the spray drying temperature range is 200-250℃, and the frequency is 50-60Hz.

[0033] Furthermore, in step (3), the sintering temperature of the low-temperature sintering is 450-650℃, and the sintering time is 4-10h.

[0034] Furthermore, in step (3), the sintering temperature of high-temperature sintering is 800-1000℃, and the sintering time is 10-20h.

[0035] The present invention provides a lithium supplementation additive Li5FeO4 prepared according to the above method.

[0036] The application of the lithium-supplementing additive Li5FeO4 provided by this invention in the field of lithium batteries.

[0037] Furthermore, the applications include the fabrication of coin cells and pouch cells.

[0038] Furthermore, the preparation method of the coin cell includes: weighing the above-mentioned lithium supplementation additive Li5FeO4, carbon black and PVDF in a mass ratio of 90 to 95:4:4, mixing them into a slurry, and then coating, baking, cold pressing, cutting and assembling the coin cell.

[0039] Furthermore, the preparation method of the soft-pack battery includes: mixing the above-mentioned lithium supplementation additive Li5FeO4 with the positive electrode material LiCoO2 at a weight ratio of 1:8 to 12; then mixing the mixture of Li5FeO4 and LiCoO2 (LCO-LFO): conductive carbon black (SP): polyvinylidene fluoride (PVDF) at a weight ratio of 85 to 95:5:5 to prepare the positive electrode material; the negative electrode material is artificial graphite; the electrolyte is a solvent of 1 to 1.5 mol / L LiPF6; the solvent is a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) at a volume ratio of 1:0.5 to 1.5; the separator is a polypropylene microporous film; and then the above-mentioned positive electrode material, negative electrode material, electrolyte and separator are prepared according to the following steps.

[0040] Beneficial effects

[0041] (1) Improve energy density and enhance battery performance: The lithium supplement additive prepared in this invention can effectively improve the energy density of the battery by supplementing the missing lithium ions. The coin cell specific capacity can reach up to 800mAh / g, and the first charge and discharge efficiency can reach up to 93.98%, thereby extending the battery's usage time and range.

[0042] (2) Reduce capacity decay and extend battery life: The lithium replenishment additive prepared in this invention can extend the cycle life of the battery. Charge-discharge test data shows that the capacity retention rate can reach more than 90% after 50 cycles, with a maximum of 91.02%. This is of great significance for reducing the frequency of battery replacement and reducing the cost of use. Attached Figure Description

[0043] Figure 1 XRD pattern of lithium supplement additive Li5FeO4.

[0044] Figure 2 SEM image of lithium supplementation additive Li5FeO4. Detailed Implementation

[0045] Source of raw materials

[0046] The iron oxide powder is at the nanoscale, with a particle size range of 50-100nm, and was purchased from Xingxing Electronic New Materials (Wuxi) Co., Ltd. Unless otherwise specified, all other raw materials used are commercially available products.

[0047] Example 1

[0048] A lithium supplement additive, Li5FeO4, and its preparation method, comprising the following steps:

[0049] (1) First, add 450g of ultrapure water to the reactor, then add hydrogen peroxide powder to prepare a hydrogen peroxide solution with a concentration of 25wt%, and finally add 46g of iron oxide powder and 1.0g of additive and stir thoroughly to obtain mixed dispersion 1; wherein the additive is 0.28g of glucose and 0.72g of nano aluminum oxide.

[0050] (2) Slowly add 150g of lithium hydroxide powder to the mixed dispersion 1 obtained in step (1) and heat at 70°C while stirring at 250r / min for 60min to obtain mixed dispersion 2;

[0051] (3) The mixed dispersion 2 obtained in step (2) was subjected to solid-liquid separation to retain the solid. The solid was washed repeatedly with anhydrous ethanol 6 times, and then anhydrous ethanol was added. The solid was then milled at 2800 r / min for 120 min, and then spray-dried (spray drying temperature was 230℃, frequency was 55 Hz). The dried solid was then sintered at 550℃ for 6 h, and then sintered at 850℃ for 15 h. After sintering, the product was cooled and then crushed and sieved (350 mesh) to obtain D. 50 The lithium supplementation additive is approximately 10 μm in size, consisting of Li5FeO4.

[0052] Example 2

[0053] A lithium supplement additive, Li5FeO4, and its preparation method, comprising the following steps:

[0054] (1) First, add 450 mL of ultrapure water to the reactor, then add hydrogen peroxide powder to prepare a hydrogen peroxide solution with a concentration of 20 wt%, and finally add 40.0 g of iron oxide powder and 0.83 g of additives and stir thoroughly to obtain mixed dispersion 1; wherein the additives are 0.23 g of glucose and 0.6 g of nano aluminum oxide.

[0055] (2) Slowly add 150g of lithium hydroxide powder to the mixed dispersion 1 obtained in step (1) and heat at 70°C while stirring at 250r / min for 60min to obtain mixed dispersion 2;

[0056] (3) The mixed dispersion 2 obtained in step (2) was subjected to solid-liquid separation to retain the solid. The solid was washed repeatedly with anhydrous ethanol 6 times, and then anhydrous ethanol was added to grind it at a speed of 2800 r / min for 120 min. Then it was spray dried (the spray drying temperature was 230℃ and the frequency was 55 Hz). After that, the dried solid was sintered at 550℃ for 6 h, and then sintered at 850℃ for 15 h. After sintering, the product was cooled and then crushed and sieved (350 mesh) to obtain D. 50 The lithium supplementation additive is approximately 12 μm Li5FeO4.

[0057] Example 3

[0058] A lithium supplement additive, Li5FeO4, and its preparation method, comprising the following steps:

[0059] (1) First, add 450 mL of ultrapure water to the reactor, then add hydrogen peroxide powder to prepare a hydrogen peroxide solution with a concentration of 30 wt%, and finally add 40.0 g of iron oxide powder and 1.1 g of additives and stir thoroughly to obtain mixed dispersion 1; wherein the additives are 0.3 g of glucose and 0.8 g of nano aluminum oxide.

[0060] (2) Slowly add 150g of lithium hydroxide powder to the mixed dispersion 1 obtained in step (1) and heat at 70°C while stirring at 250r / min for 60min to obtain mixed dispersion 2;

[0061] (3) The mixed dispersion 2 obtained in step (2) was subjected to solid-liquid separation to retain the solid. The solid was washed repeatedly with anhydrous ethanol 6 times, and then anhydrous ethanol was added to grind it at a speed of 2800 r / min for 120 min. Then it was spray dried (the spray drying temperature was 230℃ and the frequency was 55 Hz). After that, the dried solid was sintered at 550℃ for 6 h, and then sintered at 850℃ for 15 h. After sintering, the product was cooled and then crushed and sieved (350 mesh) to obtain D. 50 The lithium supplementation additive is approximately 9 μm in size, namely Li5FeO4.

[0062] Comparative Example 1

[0063] The preparation method is the same as in Example 1, except that glucose is used instead of citric acid.

[0064] Comparative Example 2

[0065] The preparation method of Example 1 is used, except that nano-alumina replaces aluminum hydroxide.

[0066] Comparative Example 3

[0067] The preparation method of Example 1 is followed, except that only the material is removed by sintering at 850°C for 15 hours.

[0068] Comparative Example 4

[0069] The preparation method of Example 1 was followed, except that the composition of the additives was adjusted to 0.1g of glucose and 0.72g of nano-alumina.

[0070] Comparative Example 5

[0071] The preparation method of Example 1 was followed, except that the composition of the additives was adjusted to 0.4g of glucose and 0.72g of nano-alumina.

[0072] The lithium supplementary additive Li5FeO4 prepared in the above examples and comparative examples was tested, and the testing process is as follows:

[0073] (1) The lithium supplementation additive Li5FeO4 prepared in Example 1 was subjected to XRD detection, and the detection results are as follows: Figure 1 .

[0074] (2) The lithium-supplementing additive Li5FeO4 prepared in Example 1 was analyzed by SEM, and the results are as follows: Figure 2 .

[0075] (3) The electrical performance of the CR2032 coin cell was tested. The test procedure was as follows: First, the lithium additive Li5FeO4:carbon black:PVDF were weighed according to a mass ratio of 92:4:4, and then homogenized, coated, baked, cold-pressed, cut and assembled into coin cells for testing. The coin cells were charged to 4.7V at a constant current and constant voltage of 0.1C. The specific capacity results are shown in Table 1.

[0076] Table 1. Coin cell capacity of each embodiment and comparative example.

[0077] Example 1 797.25 Example 2 800.38 Example 3 799.58 Comparative Example 1 734.25 Comparative Example 2 769.68 Comparative Example 3 665.47 Comparative Example 4 770.59 Comparative Example 5 775.68

[0078] (4) The lithium-supplementing additive Li5FeO4 prepared above is mixed with commercially available cathode material LiCoO2 at a weight ratio of 1:10. Then, a mixture of Li5FeO4 and LiCoO2 (LCO-LFO): conductive carbon black (SP): polyvinylidene fluoride (PVDF) at a weight ratio of 90:5:5 is mixed to prepare the cathode material. The anode active material is artificial graphite, the electrolyte is 1 mol / L LiPF6 / EC-DMC (1:1), and the separator is a polypropylene microporous film. The specific battery manufacturing process includes: slurry preparation, coating, rolling, cutting, stacking, tab welding, side and top sealing, baking, electrolyte injection, settling, formation, aging, and testing.

[0079] The assembled pouch cells were tested using the Xinwei Battery Testing System. The voltage window was 3.0-4.5V, and the cells were charged and discharged at 0.1C / 0.1C. The discharge specific capacity was recorded, and the initial charge and discharge efficiency and capacity retention rate after 50 cycles were calculated. The results are shown in Table 2.

[0080] Table 2 Charge-discharge test data for each embodiment and comparative example.

[0081]

[0082] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for preparing a lithium-supplementing additive, Li5FeO4, characterized in that, Includes the following steps: (1) Hydrogen peroxide solution, iron oxide powder and additives are mixed to obtain mixed dispersion 1; the additives are composed of 20-30 wt% organic carbon source and 70-80 wt% aluminum additive; the organic carbon source is glucose; the aluminum additive is nano aluminum oxide; (2) Add lithium hydroxide to the mixed dispersion 1 obtained in step (1) and heat and stir to obtain mixed dispersion 2; (3) The mixed dispersion 2 obtained in step (2) is subjected to solid-liquid separation. The resulting solid is washed, milled, dried, sintered at low temperature, sintered at high temperature, and pulverized to obtain D. 50 Lithium supplementation additive Li5FeO4 in the 6-15μm range.

2. The preparation method according to claim 1, characterized in that, In step (1), the concentration of hydrogen peroxide solution is 10-30 wt%; the iron oxide powder is at the nanoscale with a particle size range of 50-100 nm.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of iron oxide powder to additive is 30-50:1; the mass ratio of iron oxide powder to additive is 35-50:1; and the mass ratio of iron oxide powder to hydrogen peroxide solution is 30-50:

450.

4. The preparation method according to claim 1, characterized in that, In step (2), the lithium hydroxide is either anhydrous lithium hydroxide or lithium hydroxide monohydrate, and its particle size is 10-20 μm; the mass ratio of lithium hydroxide to iron oxide powder in step (1) is 3-5:

1.

5. The preparation method according to claim 1, characterized in that, The heating temperature for heating and stirring in step (2) is 55-85℃, and the stirring speed is 150-300r / min.

6. The preparation method according to claim 1, characterized in that, The solvent used for cleaning in step (3) is anhydrous ethanol or anhydrous isopropanol, and the number of cleaning cycles is 3-6.

7. The preparation method according to claim 1, characterized in that, In step (3), the sintering temperature of low-temperature sintering is 450-650℃ and the sintering time is 4-10h.

8. The preparation method according to claim 1, characterized in that, In step (3), the sintering temperature is 800-1000℃ and the sintering time is 10-20h.

9. A lithium supplementation additive, Li5FeO4, characterized in that, The lithium supplementation additive Li5FeO4 is prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the lithium-supplementing additive Li5FeO4 as described in claim 9 in the field of lithium batteries.

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