A method for preparing a lithium ion battery safety additive

Abstract

The application provides a preparation method of a lithium ion battery safety additive. The lithium ion battery safety additive is prepared by coating heat-meltable lithium ion battery safety particles with citric acid. When the temperature of the lithium ion battery suddenly increases due to overcharging, overdischarging, short circuit, mechanical collision or the like, the lithium ion battery safety particles melt and release the internal citric acid, the citric acid couples with Li + and passivates the electrolyte, thereby blocking the thermal runaway risk of the lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery safety additives, and more specifically, to a method for preparing a lithium-ion battery safety additive. Background Technology

[0002] Lithium-ion batteries are widely used due to their high operating voltage, small size, light weight, lack of memory effect, no pollution, low self-discharge, and long cycle life. At low temperatures, the viscosity of the electrolyte in lithium-ion batteries decreases, conductivity declines, and the activity of the active materials decreases. Simultaneously, the concentration gradient of the electrolyte increases, polarization intensifies, and charging terminates prematurely. This results in a decrease in both the discharge capacity and operating voltage of lithium-ion batteries at low temperatures.

[0003] A lithium-ion battery consists of at least an anode, a cathode, and a separator separating the anode and cathode. The separator is impregnated with an electrolyte, and the battery primarily functions by the movement of lithium ions between the positive and negative electrodes. Lithium-ion batteries are characterized by long cycle life, high specific energy, and no memory effect, and are widely used in rechargeable batteries for portable electronic products such as mobile phones, laptops, and camcorders, as well as in power sources for new energy vehicles. However, during use, lithium-ion batteries have gradually revealed inherent safety issues. Improper use, such as overcharging, over-discharging, short circuits, and mechanical impacts, can lead to a sudden increase in temperature, potentially resulting in thermal runaway, explosion, and fire.

[0004] In existing technologies, phosphate esters, phosphites, and organohalogenated flame-retardant electrolytes are mainly used to solve the problem of thermal runaway in lithium-ion batteries. However, the above methods mainly produce a certain flame-retardant effect after an explosion and fire, and the flame-retardant effect is not good. In particular, organohalogenated flame-retardant electrolytes will also produce highly toxic combustion exhaust gases, which is of little practical significance for improving the safety of lithium-ion batteries. Summary of the Invention

[0005] This invention provides a method for preparing a lithium-ion battery safety additive. By preparing heat-fusible lithium-ion battery safety particles coated with citric acid, when the temperature of the lithium-ion battery rises sharply due to overcharging, over-discharging, short circuits, mechanical impacts, etc., the lithium-ion battery safety particles melt and release the internal citric acid. This release is achieved through the coupling of citric acid with Li... + Passivating the electrolyte helps to prevent the risk of thermal runaway in lithium-ion batteries.

[0006] A method for preparing a safety additive for lithium-ion batteries, the method being as follows:

[0007] (1) Heat anhydrous ethanol to 50-60℃, add 5%-10% citric acid by mass of anhydrous ethanol, dissolve completely and cool to room temperature to obtain citric acid ethanol solution.

[0008] (2) After heating and melting the hot-melt wax, a citric acid ethanol solution is added dropwise to obtain hot-melt wax microspheres A with citric acid uniformly distributed on the surface;

[0009] (3) Reheat and melt the hot-melt wax microspheres A, while maintaining a vacuum for 30-60 minutes to completely remove ethanol;

[0010] (4) Spray granulation of the above molten liquid to obtain hot-melt wax microspheres B;

[0011] (5) Clean the hot-melt wax microspheres B with anhydrous ethanol to remove the citric acid on the surface, and then dry them to obtain lithium-ion battery safety particles.

[0012] Furthermore, the hot-melt wax is one or more of PEG 20000, PEG 30000, palm wax, PE wax, and PP wax.

[0013] Furthermore, in step (2), the mass ratio of hot-melt wax to citric acid ethanol solution is 3-5:1.

[0014] Furthermore, in step (4), the nozzle temperature is maintained at 155-160°C.

[0015] Furthermore, the particle size of the lithium-ion battery safety particles is 50-200 μm.

[0016] Furthermore, the amount of lithium-ion battery safety particles added to the electrolyte is 0.5%-3% of the electrolyte mass.

[0017] The technical effects and advantages of this invention are as follows:

[0018] 1. This invention involves preparing heat-fusible lithium-ion battery safety particles coated with citric acid. When the temperature of the lithium-ion battery rises sharply due to overcharging, over-discharging, short circuits, or mechanical impacts, the lithium-ion battery safety particles melt and release the internal citric acid. This citric acid then couples with Li... + Passivating the electrolyte can help prevent the risk of thermal runaway in lithium-ion batteries.

[0019] 2. The preparation method of the present invention can improve the content and uniform distribution of citric acid in lithium-ion battery safety particles, and at the same time effectively improve the utilization rate of citric acid; the nozzle temperature is maintained at 155-160℃ during spray granulation, which can make the hot melt wax and citric acid melted at the moment of spraying, which is conducive to the uniform distribution of citric acid and improves the utilization rate of citric acid. Detailed Implementation

[0020] Example 1

[0021] A method for preparing a safety additive for lithium-ion batteries, the method being as follows:

[0022] (1) Heat anhydrous ethanol to 60°C, add 9% citric acid by mass of anhydrous ethanol, dissolve completely and then cool to room temperature to obtain citric acid ethanol solution.

[0023] (2) After heating and melting the hot-melt wax PEG 20000, add the citric acid ethanol solution dropwise according to the mass ratio of hot-melt wax to citric acid ethanol solution of 4:1 to obtain hot-melt wax microspheres A with citric acid uniformly distributed on the surface.

[0024] (3) Reheat and melt the hot-melt wax microspheres A, while maintaining a vacuum for 40 minutes to completely remove ethanol;

[0025] (4) Spray the above molten liquid into granules, keeping the nozzle temperature at 155°C, to obtain hot-melt wax microspheres B;

[0026] (5) Clean the hot-melt wax microspheres B with anhydrous ethanol to remove the citric acid on the surface, and then dry them to obtain lithium-ion battery safety particles.

[0027] Example 2

[0028] In step (4), the nozzle temperature is maintained at 150°C, and the rest is the same as in Example 1.

[0029] Comparative Example 1

[0030] Take an equal amount of citric acid and PEG 20000 as in Example 1, grind the citric acid to 800 mesh, then heat the PEG 20000 to melt and mix it with the citric acid powder and disperse it evenly. Spray granulation is then carried out, followed by washing with anhydrous ethanol to obtain lithium-ion battery safety particles.

[0031] Comparative Example 2

[0032] The same amount of citric acid and PEG 20000 as in Example 1 were directly mixed and heated until both PEG 20000 and citric acid were melted and evenly dispersed. The mixture was then spray-granulated and washed with anhydrous ethanol to obtain lithium-ion battery safety particles.

[0033] Performance testing:

[0034] 1. During spray granulation, a 100μm nozzle was used in all examples and comparative examples to test the citric acid content (%) of the lithium-ion battery safety particles in each example and comparative example; at the same time, the utilization rate (%) of citric acid was calculated based on this.

[0035] Citric acid utilization rate (%) = Citric acid in lithium-ion battery safety particles / Citric acid feed amount * 100%

[0036] 2. A blank electrolyte was prepared using lithium hexafluorophosphate, lithium difluorobis(oxalato)phosphate, and lithium bis(trifluoromethanesulfonyl)imide as lithium salts and ethylene carbonate, propylene carbonate, and diethyl carbonate as solvents.

[0037] Lithium-ion battery safety particles (1.5% by mass) were added to a blank electrolyte to prepare a thermal runaway-blocking electrolyte. The blank electrolyte and each thermal runaway-blocking electrolyte were charged to 3.60V at a constant current and constant voltage of 0.5C, heated to 65℃, and then discharged to 2.5V at a current of 0.5C. The discharge capacity percentage (%) was recorded based on the blank electrolyte.

[0038] Then remove the electrolyte and observe its appearance.

[0039]

[0040] The above embodiments and comparative examples are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above embodiments and comparative examples, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a safety additive for lithium-ion batteries, characterized in that: The preparation method is as follows: (1) Heat anhydrous ethanol to 50-60℃, add 5%-10% citric acid by mass of anhydrous ethanol, dissolve completely and cool to room temperature to obtain citric acid ethanol solution. (2) After heating and melting the hot-melt wax, a citric acid ethanol solution is added dropwise to obtain hot-melt wax microspheres A with citric acid uniformly distributed on the surface; (3) Reheat and melt the hot-melt wax microspheres A, while maintaining a vacuum for 30-60 minutes to completely remove ethanol; (4) Spray granulation of the above molten liquid to obtain hot-melt wax microspheres B; (5) Clean the hot-melt wax microspheres B with anhydrous ethanol to remove the citric acid on the surface, and then dry them to obtain lithium-ion battery safety particles.

2. The method for preparing the lithium-ion battery safety additive according to claim 1, characterized in that: The hot-melt wax is one or more of PEG 20000, PEG 30000, palm wax, PE wax, and PP wax.

3. The method for preparing the lithium-ion battery safety additive according to claim 1, characterized in that: In step (2), the mass ratio of hot-melt wax to citric acid ethanol solution is 3-5:

1.

4. The method for preparing the lithium-ion battery safety additive according to claim 1, characterized in that: In step (4), the nozzle temperature is maintained at 155-160℃.

5. Lithium-ion battery safety particles prepared by the method for preparing lithium-ion battery safety additives according to any one of claims 1-4.

6. The lithium-ion battery safety particle according to claim 5, characterized in that: The particle size of the lithium-ion battery safety particles is 50-200 μm.

7. The lithium-ion battery safety particle according to claim 5, characterized in that: The amount of lithium-ion battery safety particles added to the electrolyte is 0.5%-3% of the electrolyte mass.

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