CN-122025999-A - High-temperature-resistant high-safety modification method for lithium battery diaphragm

CN122025999ACN 122025999 ACN122025999 ACN 122025999ACN-122025999-A

Abstract

The invention discloses a high-temperature-resistant high-safety modification method of a lithium battery diaphragm, which belongs to the technical field of lithium battery diaphragms and comprises the steps of S1, pretreatment and surface functionalization of a base film, namely, selective activation and grafting are carried out on a single-side surface of a polyolefin-based film to construct an activated substrate, S2, preparation of functional coating slurry, namely, preparation of high-viscosity capturing-side functional slurry and low-viscosity slow-release-side intelligent response slurry containing a thermal trigger release material respectively, S3, gradient coating and structure locking, namely, the capturing-side functional slurry and the slow-release-side intelligent response slurry are sequentially coated on the activated substrate, and a functional coating is formed through a wet film infiltration and phase transformation process, and S4, post-treatment, namely, the functional coating is subjected to thermal treatment to obtain a lithium battery diaphragm product.

Inventors

LIANG XING
Wen Pushan
ZHAO GUANGLIAN
HE LIN
ZHANG SUYING
FEI FEI

Assignees

遵义师范学院

Dates

Publication Date: 20260512
Application Date: 20260203

Claims (10)

1. The high-temperature-resistant high-safety modification method for the lithium battery diaphragm is characterized by comprising the following steps of: s1, pretreatment and surface functionalization of a base film, namely, selectively activating and grafting the surface of one side of a polyolefin base film to construct an activated substrate; S2, preparing functional coating slurry, namely preparing high-viscosity capturing side functional slurry and low-viscosity slow-release side intelligent response slurry containing a thermal trigger release material; The capturing side functional slurry comprises high-temperature resistant resin, metal organic framework capturing materials, reinforcing fibers and a conductive agent; the slow-release side intelligent response slurry comprises high-temperature resistant resin, heat trigger release type composite functional powder and thixotropic agent, wherein the heat trigger release type composite functional powder is formed by physically mixing low-melting-point polymer microspheres with melting points of 60-75 ℃ with a composite lithium salt repairing agent; s3, gradient coating and structure locking, namely sequentially coating capturing side functional slurry and slow-release side intelligent response slurry on the activated substrate, and forming a functional coating through a wet film infiltration and phase conversion process; and S4, post-treatment, namely carrying out high-temperature heat treatment on the functional coating to obtain a lithium battery diaphragm product.
2. The modification process according to claim 1, wherein in S1, the selective activation and grafting specifically comprises treating the surface of one side of the polyolefin-based film with a low temperature oxygen plasma, followed by immersing in a vinyl silane coupling agent solution for grafting reaction.
3. The modification method according to claim 2, wherein the low-temperature oxygen plasma treatment condition is 80-120W, the oxygen flow is 20-50 sccm, the chamber pressure is 20-40 Pa, and the treatment is 60-90 s, the vinyl silane coupling agent solution is an ethanol solution of vinyl triethoxysilane with the mass concentration of 1% -3%, and the grafting temperature is 80-100 ℃ and the time is 15-30 min.
4. The modification method according to claim 1, wherein in S2, the preparation process of the high temperature resistant resin comprises the steps of adding 12-15 parts of polyether-ether-ketone or polyether-ketone powder into 85-88 parts of mixed solvent of concentrated sulfuric acid and methane sulfonic acid, and continuously stirring for 6-12 hours at 0-5 ℃ and 500-700 r/min until the polymer is completely dissolved, so as to obtain the high temperature resistant resin, wherein the volume ratio of the concentrated sulfuric acid to the methane sulfonic acid is 9:1.
5. The method according to claim 1, wherein in S2, the metal organic framework powder is any one of ZIF-8, ZIF-9 and ZIF-10, the mass ratio of the high temperature resistant resin, the metal organic framework powder, the reinforcing fiber and the conductive agent is 100 (80-120): (1-3): (3-5), and the viscosity of the capturing side functional slurry at 25 ℃ is 4070 mPa.s-5975 mPa.s.
6. The modification method according to claim 1, wherein in the S2, the mass ratio of the high-temperature resistant resin, the thermal trigger release type composite functional powder and the thixotropic agent in the slow-release side intelligent response slurry is 100 (30-50) (0.5-1.0), and the viscosity of the slow-release side intelligent response slurry at 25 ℃ is 1080 mPas-1980 mPas.
7. The modification method according to claim 1, wherein in the S2, the low-melting polymer microspheres are low-density polyethylene with an average particle size of 2-5 μm and a melting point of 60-75 ℃, the composite lithium salt repairing agent is a mixture of LiNO 3 , liFSI and lithium difluorooxalato borate in a mass ratio of 2:1:1, and the mass ratio of the low-melting polymer microspheres to the composite lithium salt repairing agent is 1 (0.8-1.2).
8. The modification method according to claim 1, wherein the specific step of S3 includes the steps of coating the capturing side functional slurry on the activated substrate, forming a porous skeleton through preliminary shaping, coating the slow-release side intelligent response slurry on the porous skeleton, standing for 10-30S in an environment with humidity of 80% or more, allowing components at the interface of the two layers of wet films to mutually infiltrate, immersing in a non-solvent coagulation bath for phase inversion, and locking to form the functional coating.
9. The modification method according to claim 8, wherein the preliminary shaping is to treat 1 to 2 minutes under a circulating hot air at 60 to 80 ℃ and the non-solvent coagulation bath is a mixed solution of deionized water and N-methylpyrrolidone at 20 to 25 ℃.
10. The modification method according to claim 1, wherein the specific step of S4 comprises heat-treating for 10min to 20min under an inert atmosphere at 200 ℃ to 240 ℃.

Description

High-temperature-resistant high-safety modification method for lithium battery diaphragm Technical Field The invention relates to the technical field of lithium battery diaphragms, in particular to a high-temperature-resistant high-safety modification method for a lithium battery diaphragm. Background With the rapid development of the fields of electric automobiles, large-scale energy storage and the like, the market has put forward severe requirements on the energy density, the safety and the cycle life of lithium ion batteries. The separator is used as a key inner component of the battery, has the core functions of isolating the anode and the cathode to prevent short circuit and providing a lithium ion transmission channel, and the performance of the separator directly determines the safety boundary and the electrochemical performance of the battery. Therefore, developing a high performance separator with high thermal stability, excellent interface compatibility and active safety protection capability has become an important direction to break through the current battery technology bottleneck. To improve the performance of the separator, a common improvement method is to coat the surface of the base film with a ceramic or high temperature resistant polymer coating. However, such conventional coating techniques have significant limitations. Firstly, the coating and the base film are combined mainly through physical adsorption, the interface binding force is weak, and the coating and the base film are easy to peel in long-term use. Second, the introduced functional filler tends to block the ion transport channels, resulting in a decrease in the ionic conductivity of the separator. More importantly, the existing coating is only passively protected, active intervention cannot be performed when the internal temperature of the battery is abnormal, and occurrence of thermal runaway is difficult to be fundamentally prevented. Therefore, development of a novel membrane design and preparation method is needed. The method needs to be capable of realizing firm combination of the coating and the base film, constructing a gradient functional structure with high ionic conductivity and excellent thermal stability, and introducing an intelligent safety mechanism capable of dynamically responding to the internal state change of the battery, thereby providing key material support for the development of the next-generation high-safety and long-service-life lithium battery. Disclosure of Invention The invention aims to provide a high-temperature-resistant high-safety modification method for a lithium battery diaphragm, which aims to solve the key problems of poor thermal stability, weak interface combination, lack of an active safety mechanism and the like of the traditional coated diaphragm. By constructing the gradient functional coating and introducing the intelligent response unit, the interface combination and the ion transmission are enhanced, and meanwhile, the active heat protection capability of the diaphragm is endowed, and finally, the controllable preparation of the high-performance diaphragm with excellent heat stability, high safety and long cycle life is realized, and the severe requirement of the high-energy density lithium battery on the key material performance is met. In order to achieve the above object, the present invention provides the following solutions: the high-temperature-resistant high-safety modification method of the lithium battery diaphragm is characterized by comprising the following steps of: s1, pretreatment and surface functionalization of a base film, namely, selectively activating and grafting the surface of one side of a polyolefin base film to construct an activated substrate; S2, preparing functional coating slurry, namely preparing high-viscosity capturing side functional slurry and low-viscosity slow-release side intelligent response slurry containing a thermal trigger release material; the capturing side functional slurry comprises high-temperature resistant resin, a metal organic framework capturing material, reinforcing fibers and a conductive agent; the intelligent response slurry at the slow release side comprises high-temperature resistant resin, heat trigger release type composite functional powder and thixotropic agent, wherein the heat trigger release type composite functional powder is formed by physically mixing low-melting-point polymer microspheres with melting points of 60-75 ℃ with a composite lithium salt repairing agent; S3, gradient coating and structure locking, namely sequentially coating functional slurry on a capturing side and intelligent response slurry on a slow release side on the activated substrate, and forming a functional coating through a wet film infiltration and phase conversion process; and S4, post-treatment, namely carrying out high-temperature heat treatment on the functional coating to obtain a lithium battery diaphragm product. Further, in S1,