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Diaphragm for secondary battery, preparation method of diaphragm and secondary battery

A secondary battery and diaphragm technology, applied in the field of secondary battery diaphragm and its preparation, can solve the problems of inability to carry out the combustion process of the electrolyte solution, reduce the ionic conductivity of the electrolyte solution, decrease the electrochemical performance, etc. Good cycle performance, preventing thermal runaway and explosion effects

Pending Publication Date: 2022-05-13
惠州锂威电子科技有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

At present, researchers can effectively suppress the spread of fire in lithium-ion batteries by adding flame retardants to the electrolyte, because the flame retardants capture combustion radicals in the gas phase when heated And then block the chain reaction of free radicals, so that the combustion process of the electrolyte cannot or is difficult to carry out
However, adding a large amount of flame retardants will reduce the ionic conductivity of the electrolyte, leading to a decrease in electrochemical performance, especially the cycle life and rate performance.

Method used

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  • Diaphragm for secondary battery, preparation method of diaphragm and secondary battery
  • Diaphragm for secondary battery, preparation method of diaphragm and secondary battery
  • Diaphragm for secondary battery, preparation method of diaphragm and secondary battery

Examples

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preparation example Construction

[0038] The second object of the present invention is to provide a method for preparing the above-mentioned secondary battery separator, comprising the following steps:

[0039] S1. Mix methyl methacrylate, cross-linking agent, surfactant, solvent, initiator and flame retardant to form a homogeneous solution, and remove the active oxygen in it, then heat to 40-50°C and operate at 200-300rpm / Carry out the polymerization reaction at min speed for 5-6 hours; after the reaction, take out the synthesized flame-retardant capsules, wash and dry them for more than 24 hours;

[0040] S2. Dissolve the polyvinylidene fluoride-hexafluoropropylene binder in a volatile solvent, then add the flame-retardant capsule obtained in step S1 into it and stir, then immerse the base film 1 in it, take out the base film 1, and dry Finally, a secondary battery separator containing the flame-retardant layer 2 is obtained.

[0041]In step S1, methyl methacrylate (MMA) is mixed and dispersed with crossli...

Embodiment 1

[0053] A separator for a secondary battery, such as figure 1 As shown, it includes a PE base film 1 and a flame retardant layer 2 coated on at least one surface of the PE base film 1; the flame retardant layer 2 is made of polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) binder and a Composed of a flame-retardant capsule, the flame-retardant capsule is a core-shell structure with trimethyl phosphate as the core and polymethyl methacrylate (PMMA) as the shell.

[0054] The preparation method of this membrane can be as Figure 2-4 shown, including the following steps:

[0055] S1. Preparation of flame retardant capsules: In a three-necked flask, add 30ml methyl methacrylate (MMA, monomer) and 0.3ml ethylene glycol dimethacrylate (EGDMA, crosslinking agent) to 500ml deionized water And in 2.5g triton X-100 (surfactant), pass into N 2 Remove the active oxygen in the three-necked flask, and stir at 800rpm / min for 30min to form a homogeneous mixed solution; then take 30mL t...

Embodiment 2

[0058] The difference from Example 1 is the preparation method of the flame retardant capsule.

[0059] S1. Preparation of flame retardant capsules: In a three-necked flask, add 30ml methyl methacrylate (MMA, monomer) and 0.3ml ethylene glycol dimethacrylate (EGDMA, crosslinking agent) to 500ml deionized water And in 2.5g triton X-100 (surfactant), pass into N 2 Remove the active oxygen in the three-necked flask, and stir at 800rpm / min for 30min to form a homogeneous mixed solution; then take 30mL trimethyl phosphate, 0.3g 2,2-azobis(2,4-dimethylvaleronitrile) (ADVN, initiator) was added, stirred at 1800-2000rpm / min for 20-30min to form a uniform solution; then heated to 45°C and polymerized at 1800-2000rpm / min for 5h; after the reaction was completed, add Excessive NaCl precipitated the synthesized flame-retardant capsules, filtered them, washed them with water and ethanol three times, and dried them at room temperature for 1 day to obtain flame-retardant capsules.

[0060]...

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Abstract

The invention provides a diaphragm for a secondary battery, a preparation method of the diaphragm and the secondary battery. The diaphragm comprises a base film and a flame-retardant layer coated on at least one surface of the base film, the flame-retardant layer is composed of a polyvinylidene fluoride-hexafluoropropylene binder and a flame-retardant capsule, and the flame-retardant capsule is of a core-shell structure with a flame retardant as an inner core and polymethyl methacrylate as an outer shell. Compared with the prior art, according to the diaphragm provided by the invention, when the battery is subjected to thermal runaway, the PMMA shell is broken and can release the flame retardant, the flame retardant can capture combustion free radicals and can effectively prevent thermal runaway and explosion of the battery, and the PMMA shell is adopted, so that better bonding force can be provided for the diaphragm and a pole piece; the problem that the cycle life of the battery is difficult to guarantee while the thermal runaway of the secondary battery is blocked at present is solved.

Description

technical field [0001] The invention relates to the field of secondary batteries, in particular to a diaphragm for a secondary battery, a preparation method thereof, and a secondary battery. Background technique [0002] Lithium-ion batteries are considered to be the most promising power source for electric vehicles (EVs) due to their high specific energy density, lack of memory effect, and excellent cycling performance. However, due to the sharp increase in the energy density of lithium-ion batteries or the possibility of battery fire and explosion after a car collision, ensuring sufficient safety of lithium-ion batteries has become one of the most important issues at present. Studies have shown that the safety of lithium-ion batteries is closely related to the flammable components in the electrolyte and pole pieces. Once the inside / outside of the lithium-ion battery is on fire due to a short circuit, the flammable components (especially the cathode and flammable oxides of ...

Claims

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Application Information

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IPC IPC(8): H01M50/409H01M50/403H01M50/489H01M10/0525
CPCH01M50/409H01M50/403H01M50/489H01M10/0525Y02E60/10
Inventor 赖旭伦
Owner 惠州锂威电子科技有限公司
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