CN-121992579-A - Solid-solid phase change membrane material with in-situ thermal management and high-temperature conductivity enhancement functions and preparation method thereof

CN121992579ACN 121992579 ACN121992579 ACN 121992579ACN-121992579-A

Abstract

The invention discloses a solid-solid phase change membrane material with in-situ thermal management and high-temperature conductivity enhancement functions and a preparation method thereof, belonging to the technical field of new energy materials and devices. The invention takes polyurethane solid-solid phase change material as a functional matrix, takes polyacrylonitrile as a spinning aid, fully mixes the polyurethane solid-solid phase change material and the polyacrylonitrile in a solvent to form spinning solution, and then obtains the solid-solid phase change membrane material through electrostatic spinning. The diaphragm material not only can effectively maintain structural integrity at high temperature, but also can greatly improve lithium ion conductivity after high-temperature phase transition. The diaphragm material also has excellent electrolyte wettability, is used as a battery diaphragm, greatly improves the safety and energy density of a battery system, has simple preparation process and strong controllability, does not need expensive complex equipment, and has good large-scale production potential.

Inventors

ZOU RUQIANG
HAN HAIWEI
JIN YONGKANG
YAN HANG
HAN SHENGHUI
SHEN ZHENGHUI

Assignees

北京大学

Dates

Publication Date: 20260508
Application Date: 20260409

Claims (10)

1. A solid-solid phase change membrane material is characterized in that the solid-solid phase change membrane material is a composite nanofiber material obtained by uniformly blending polyurethane and polyacrylonitrile on a nanometer scale, wherein the polyurethane is a solid-solid phase change material formed by in-situ crosslinking of a polyether soft segment and a diisocyanate hard segment, the polyacrylonitrile is taken as a spinning aid, the polyurethane and the polyacrylonitrile are fully mixed in a solvent to form a spinning solution, and then the solid-solid phase change membrane material is obtained through electrostatic spinning.
2. The solid-solid phase change membrane material according to claim 1, wherein the polyurethane accounts for 30-70% of the total mass of the solid-solid phase change membrane material.
3. The solid-solid phase change separator material according to claim 1, wherein the soft segments of polyurethane are composed of polyethylene glycol and the hard segments are composed of one or more of hexamethylene diisocyanate, isophorone diisocyanate, and toluene diisocyanate.
4. A solid-solid phase change membrane material according to claim 3, wherein the soft segment of polyurethane is composed of polyethylene glycol 6000 and the hard segment is composed of hexamethylene diisocyanate, and the mass ratio of the two is 1:1.
5. The solid-solid phase change membrane material according to claim 1, wherein the solid-solid phase change membrane material is a three-dimensional porous network constructed by fibers with diameters distributed between 500 nm and 750 nm.
6. The method for preparing the solid-solid phase change membrane material according to any one of claims 1 to 5, which is characterized by comprising the following steps: 1) Polyether polyol and diisocyanate are polymerized into polyurethane with specific solid-solid phase transition temperature through in-situ crosslinking; 2) The polyurethane synthesized in the step 1) and polyacrylonitrile are dissolved in a solvent together according to a preset proportion, and stirred for a period of time at 60-80 ℃ to form uniform and transparent spinning solution; 3) And drawing the spinning solution into nanofibers by using a high-voltage electrostatic spinning technology, and depositing the nanofibers at a receiving end to obtain the solid-solid phase change membrane material.
7. The method of claim 6, wherein the solid-solid phase transition temperature of the polyurethane synthesized in step 1) is in the range of 40 ℃ to 60 ℃.
8. The method according to claim 6, wherein the solid content of the spinning solution in step 2) is 10-15 wt.% and the solvent is one or more of N, N-dimethylformamide and dimethylacetamide.
9. The method according to claim 6, wherein the parameters of the high-voltage electrostatic spinning in the step 3) are set as follows, positive high voltage applied to the nozzle is +15 to +17 kV, negative high voltage applied to the receiving device is-4 to-6 kV, and the distance from the tip of the nozzle to the receiver is fixed to 20-25 cm.
10. The use of the solid-solid phase change membrane material according to any one of claims 1 to 5 as a lithium ion battery membrane.

Description

Solid-solid phase change membrane material with in-situ thermal management and high-temperature conductivity enhancement functions and preparation method thereof Technical Field The invention belongs to the technical field of new energy materials and devices, and particularly relates to a lithium ion battery diaphragm, in particular to a composite nanofiber diaphragm material with a solid-solid phase change temperature control function and conductivity enhancement characteristics at high temperature. Background With the increasing demands for fast charging and high energy density of electronic devices and electric vehicles, the thermal safety problem of lithium ion batteries becomes critical to the reliability and lifetime thereof. Phase Change Materials (PCMs) are considered ideal choices for battery thermal management due to their ability to absorb or release large amounts of latent heat at constant temperatures. Currently, researchers have attempted to apply a phase change material to a cooling system of a battery module or a battery pack, and to stabilize temperature fluctuation by using its heat storage capacity. However, the prior art has the following prominent problems and disadvantages: Conventional membranes lack in-situ temperature control capability current commercial polyolefin (PP/PE) membranes are thermally "inert" in thermal management. When the internal temperature of the battery is abnormally increased, the traditional diaphragm can only cut off an ion passage through a closed pore mechanism to perform passive defense, and cannot actively absorb the generated accumulated heat. In addition, such separators are less thermally stable (typically <160 ℃) and are extremely susceptible to severe thermal shrinkage at high temperatures, resulting in direct contact of the positive and negative electrodes to initiate internal shorts. Traditional heat management relies on external components, and the currently mainstream battery heat management scheme is mainly focused on the battery pack level, namely a liquid cooling plate and an air cooling system are adopted or a large number of phase change capsules are filled in a battery cell gap. The external temperature control mode has long path and delayed response, introduces a large number of inactive components, remarkably increases the volume and weight of the battery system, and seriously reduces the grouping efficiency and the overall energy density of the battery pack. The application bottleneck of the phase change material is that the prior research tries to introduce the phase change material into the battery to absorb heat and cool, however, most of PCMs (such as paraffin wax) have extremely poor ion conducting capacity, and the lithium ion transmission efficiency is obviously reduced after the phase change material is added. More seriously, the conventional PCM generally causes the internal resistance of the battery to rise sharply at high temperature, limiting the output capacity of the battery under high power conditions. The prior art lacks an intelligent diaphragm material which can not only absorb heat actively and cool down but also improve ion transmission efficiency at high temperature (near a phase change point) without lowering and raising by utilizing the phase change material during battery thermal management. Therefore, there is an urgent need in the art for a phase change separator material that can simultaneously achieve thermal management and weight reduction of a battery, and can assist in improving high rate performance of the battery. Disclosure of Invention The invention aims to solve the problem that the conventional phase-change diaphragm is limited in battery quick charge performance due to poor ion conductivity and the pain point that the conventional diaphragm cannot actively control temperature, and provides a solid-solid phase-change diaphragm material of polyurethane/polyacrylonitrile composite nanofiber, which can improve the transmission efficiency by utilizing waste heat while guaranteeing the internal heat safety of a battery. The core of the invention is that polyurethane solid-solid phase change material is used as the basis of multifunctional realization, when electrostatic spinning solution is prepared, polyurethane phase change material crosslinked in situ is stirred and dispersed into polyacrylonitrile spinning aid at high temperature, so that the phase change material and the spinning aid are fully mixed, and then solid-solid phase change membrane is obtained through electrostatic spinning. The spinning aid ensures that the phase change material still maintains solid-solid phase change characteristics when the phase change material is higher than the phase change temperature, thereby preventing the phase change material from leaking to cause short circuit of the battery, promoting stable lamination between the phase change diaphragm and the positive electrode and between the phase change diaphragm and the ne