Search

CN-121663099-B - Self-supporting composite diaphragm with high heat conduction and preparation method and application thereof

CN121663099BCN 121663099 BCN121663099 BCN 121663099BCN-121663099-B

Abstract

The invention belongs to the technical field of secondary batteries, and particularly discloses a self-supporting composite diaphragm with high heat conduction and a preparation method and application thereof. The diaphragm comprises a polymer matrix with interpenetrating pores and high heat conduction filler distributed in the polymer matrix, wherein the internally formed interpenetrating pores form a three-dimensional porous framework, the high heat conduction filler is distributed in the pores of the three-dimensional porous framework of the polymer matrix and is in contact with the inside and/or the surface of the three-dimensional porous framework along the in-plane direction, and a continuously distributed heat conduction network is formed through surface-to-surface stacking and/or edge-to-surface lap joint, so that the diaphragm forms an interpenetrating two-dimensional heat conduction path in the in-plane direction. The structure obviously reduces the interface thermal resistance in the heat conduction process, endows the diaphragm with excellent active heat dissipation capability, and can rapidly and uniformly disperse local heat accumulation generated in the battery charging and discharging process along the plane direction, thereby effectively preventing local failure generated by heat induction and greatly improving the thermal safety of the high specific energy battery.

Inventors

  • WANG TAO
  • Yao Huchong
  • WU YUPING
  • Yuan Wenlu
  • TAN XU

Assignees

  • 东南大学

Dates

Publication Date
20260512
Application Date
20260206

Claims (10)

  1. 1. A self-supporting composite separator with high thermal conductivity, comprising: a polymer matrix having an inter-penetrating pore structure formed therein, thereby forming a three-dimensional porous skeleton; The high-heat-conductivity filler is distributed in the pores of the three-dimensional porous framework of the polymer matrix and is in contact with the three-dimensional porous framework; The high-heat-conductivity filler is a filler with a sheet-shaped or lamellar structure, the high-heat-conductivity filler is in contact with each other in the in-plane direction inside and/or on the surface of the three-dimensional porous framework, and a continuously distributed heat-conducting network is formed through surface-to-surface stacking and/or edge-to-surface lap joint, so that the self-supporting composite diaphragm forms a through two-dimensional heat-conducting passage in the in-plane direction; the porosity of the self-supporting composite membrane is 30% -60%, and the average pore diameter is 200 nm-1 mu m; the in-plane heat conduction coefficient of the self-supporting composite diaphragm is more than or equal to 85W/(m.K) under the environment of 60 ℃; The two-dimensional heat conduction path enables the dimension change rate of the self-supporting composite diaphragm to be less than 5% after the self-supporting composite diaphragm is placed for 30min in a 220 ℃ environment; the high-heat-conductivity filler is h-BN nano-sheets; The polymer matrix is selected from one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyimide, polyether sulfone, polyacrylonitrile and polyethylene oxide; The self-supporting composite diaphragm contains 50-70% of high-heat-conductivity filler by mass.
  2. 2. The self-supporting composite membrane of claim 1, wherein the mass of the highly thermally conductive material is 5% -60% of the total mass of the self-supporting composite membrane.
  3. 3. The self-supporting composite membrane of claim 1, wherein the self-supporting composite membrane has an overall thickness of 10-100 μm.
  4. 4. The self-supporting composite membrane of any one of claims 1-3, wherein the h-BN nanoplatelets have a lateral dimension of 100nm to 2 μιη.
  5. 5. The self-supporting composite membrane of claim 4, wherein the h-BN nanoplatelets have a thickness of 1nm to 100nm.
  6. 6. A method of making a self-supporting composite separator according to any one of claims 1-5, comprising: Preparing slurry, namely dispersing a polymer and/or h-BN nano-sheets in an organic solvent to form slurry; film forming, namely forming the obtained slurry into a film according to a tape casting-phase separation mode: Coating the slurry on a substrate, and then immersing the substrate in a non-solvent of the organic solvent for phase separation and solidification to form a porous membrane, wherein the h-BN nano sheet accounts for 50-70% of the mass of the porous membrane; and (3) post-treatment, namely drying the obtained film, and rolling and forming to obtain the self-supporting composite diaphragm.
  7. 7. The method according to claim 6, wherein the organic solvent is selected from any one or more of acetone, acetonitrile, N-methylpyrrolidone, N-dimethylformamide, N-dimethylacetamide, and tetrahydrofuran.
  8. 8. The method according to claim 6, wherein the phase separation curing time is 1 to 15min.
  9. 9. A secondary battery employing the self-supporting composite separator according to any one of claims 1 to 5 as an electronic insulation and thermal management component between a positive electrode and a negative electrode.
  10. 10. The secondary battery according to claim 9, wherein the secondary battery comprises a lithium ion battery, a lithium metal battery, a sodium ion battery, a sodium metal battery, or a lithium sulfur battery.

Description

Self-supporting composite diaphragm with high heat conduction and preparation method and application thereof Technical Field The invention relates to the technical field of secondary batteries, in particular to a self-supporting composite diaphragm with high heat conduction, and a preparation method and application thereof. Background With the rapid development of new energy automobiles and large-scale energy storage markets, the demand for high-energy density batteries is becoming urgent. However, the increase in battery energy density is often accompanied by greater safety risks, with thermal runaway being the core of battery safety issues. The separator is used as a key component part between the anode and the cathode of the battery, and the performance of the separator directly influences the safety and the cycle life of the battery. Commercial polyolefin separators, such as Polyethylene (PE), polypropylene (PP), have relatively low melting points (PP about 165 ℃ and PE about 135 ℃) and poor thermal stability, although they have relatively good mechanical strength and electrochemical stability. Under the conditions of local overheating inside the battery or high temperature outside, the polyolefin separator can undergo serious melting shrinkage, so that positive and negative electrodes are in direct contact to cause short circuit, and thermal runaway and even fire explosion are caused. In addition, when the battery is charged rapidly or discharged at a high rate, uneven deposition of the negative electrode metal can cause excessive local current density, so that a large amount of heat can be generated at the local current density, and if the battery cannot be dredged or homogenized in time, dendrite growth, side reaction and diaphragm aging can be accelerated to form vicious circle. More serious, when the internal temperature of the battery reaches the melting point (135-165 ℃) of the polyolefin diaphragm, the diaphragm can be melted and greatly contracted, the electronic insulation is lost, the positive electrode and the negative electrode are directly caused to be in contact with a large area for short circuit, huge heat is instantaneously released, and the heat is suddenly caused to be out of control. This is a fundamental safety defect that current commercial diaphragms cannot address. In order to improve the thermal stability of the separator, researchers have tried various methods such as coating inorganic ceramic particles of alumina (Al 2O3), silica (SiO 2) or the like on the surface of a polyolefin separator. The coatings improve the high temperature resistance of the separator to a certain extent, but have the main functions of passively resisting high temperature, have limited effects of actively conducting and homogenizing heat in the battery and preventing the whole shrinkage of the separator matrix at high temperature, and have shrinkage risks if the coatings are not compact enough or are not firmly combined with the matrix. Also, some inorganic fillers have poor compatibility with the electrolyte, and may increase interface resistance. In addition, these coating methods focus on the idea of first making a base film and then coating it. The heat conducting material is directly and uniformly embedded into the bulk phase through a one-step wet process, and the angle of forming the independent self-supporting composite diaphragm is lack of innovation. Therefore, how to construct a high-efficiency heat conduction channel with low thermal resistance and endow the diaphragm with stable structure and stable chemical property at extreme temperature on the premise of maintaining the self-supporting mechanical strength and high porosity of the diaphragm becomes a technical problem to be solved in the field of secondary battery thermal management. Disclosure of Invention Aiming at the defects of the prior art, the invention provides a self-supporting composite membrane with high heat conduction, a preparation method and application thereof, and aims to overcome the fatal defects of blocking of ion transmission and short circuit of positive and negative electrodes caused by easy melting shrinkage due to pore closure of a commercial polyolefin membrane in the prior art. In order to achieve the above purpose, the present invention adopts the following technical scheme: a first aspect of the present invention is to provide a self-supporting composite separator having high thermal conductivity, comprising: a polymer matrix having a three-dimensional porous skeleton formed by non-solvent induced phase separation; A high thermal conductivity filler whose domains are distributed in the three-dimensional porous skeleton of the polymer matrix; the high-heat-conductivity filler is overlapped in a surface-to-surface stacking manner or an edge-to-surface manner in the three-dimensional porous framework, so that a two-dimensional heat conduction path penetrating through the self-supporting composite diaphragm in-p