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CN-122000613-A - Preparation method of phase-change composite diaphragm with thermal closing function

CN122000613ACN 122000613 ACN122000613 ACN 122000613ACN-122000613-A

Abstract

The invention discloses a preparation method of a phase-change composite diaphragm with a thermal closing function, wherein the main components of the diaphragm are an electrostatic spinning fiber film and a phase-change microcapsule. The fibrous membrane in the diaphragm plays a role of supporting a framework as a base membrane, has the characteristic of difficult shrinkage at high temperature, can control the temperature to enable the battery to stably run, and when the temperature is continuously increased to a certain degree due to the abnormality of the battery, the microcapsule can be broken to block micropores of the base membrane, and the ion channel is cut off before the thermal runaway of the battery occurs, so that the safety of the battery is ensured.

Inventors

  • LIU HAIHUI
  • ZHANG YUN
  • ZHANG XINGXIANG

Assignees

  • 斯玛特西(沧州)新材料科技有限公司
  • 天津工业大学

Dates

Publication Date
20260508
Application Date
20241101

Claims (6)

  1. 1. The preparation method of the phase-change composite membrane with the thermal closing function is characterized by comprising a polymer base membrane and phase-change microcapsule slurry on the surface of the base membrane, wherein the phase-change microcapsule slurry comprises phase-change microcapsule particles, a binder and distilled water.
  2. 2. The method for preparing the phase-change composite membrane with the thermal shutdown function according to claim 1, wherein the core layer of the phase-change microcapsule is a phase-change material which is not mutually dissolved with electrolyte and has a melting temperature of 20-100 ℃, such as one or more of n-docosane, n-tetracosane, 1-tetradecanol, 1-hexadecanol, methyl stearate or ethyl stearate.
  3. 3. The method for preparing a phase-change composite membrane with a thermal shutdown function according to claim 1, wherein the sheath layer of the phase-change microcapsule is a polymer material which can be melted or converted into a viscous state at 50-150 ℃, such as a copolymer of one or two monomers of polymethyl methacrylate, polyethyl methacrylate, polystyrene and the like.
  4. 4. The method for preparing the phase-change composite membrane with the thermal shutdown function according to claim 1, wherein the polymer is one of polyvinylidene fluoride-co-hexafluoropropylene, polyethersulfone and poly-m-phenylene isophthalamide, and the excellent high-temperature stability provides a framework supporting function for the composite membrane.
  5. 5. The method for preparing the phase-change composite membrane with the thermal shutdown function according to any one of claims 1 to 4, wherein the thickness of the phase-change microcapsule coating is 5-20 μm, and the mass ratio is 10% -40%.
  6. 6. The method for preparing the phase change composite fiber membrane with the thermal shutdown function according to any one of claims 1 to 5, which is characterized by comprising the following steps: the preparation method comprises the steps of (1) preparing phase-change microcapsules, (2) preparing an electrostatic spinning base film, and (3) preparing a composite diaphragm.

Description

Preparation method of phase-change composite diaphragm with thermal closing function Technical Field The invention relates to the technical field related to battery diaphragms, in particular to a preparation method of a phase-change composite diaphragm with a thermal closing function. Background The safety and reliability of lithium batteries has been a problem that requires continued attention and improvement. The diaphragm is used as one of key components, and plays an important role in providing an ion migration channel, guaranteeing the safety of a battery, improving the performance of the battery and the like. At present, commercial polyolefin separators are easy to soften, deform and even melt at high temperature, so that a series of safety problems such as thermal runaway and fire can be caused, and the safety of a battery system is seriously threatened. Therefore, a new material or technology is urgently needed to solve the battery separator safety problem caused by temperature drastic changes. Chinese patent application 201920593724.X discloses a functional composite separator for secondary batteries, which is composed of a commercial polyolefin separator, an inorganic oxide coating, a conductive coating. The inorganic oxide coating does enhance the thermal stability of the separator, while the conductive coating helps to promote electron transfer efficiency between the interfaces. However, merely reinforcing the heat resistance of the separator is insufficient to effectively cope with the problems of heat accumulation and heat release inside the battery, and cannot fundamentally prevent the occurrence of thermal runaway. In contrast, the function of imparting thermal shutdown to the separator is particularly critical in coping with thermal runaway problems. The phase change material, which is a novel thermal response material, provides an effective solution for the modification of the diaphragm by virtue of the characteristic of absorbing or releasing heat in the phase change process. Disclosure of Invention Aiming at the improvement demand of the prior art, the invention provides a preparation method of a phase-change composite membrane with a thermal shutdown function, which is characterized in that the phase-change microcapsule is coated on a polymer membrane to obtain the thermal shutdown phase-change composite membrane, and the thermal shutdown phase-change composite membrane is applied to a lithium battery instead of a commercial polyolefin membrane. The phase change material can effectively capture heat generated in the battery, the microcapsule is broken at abnormal high temperature, and the inner core material leaks in a large amount to block the micropores of the diaphragm, so that lithium ion transmission is blocked. The electrolyte affinity of the polymer membrane can promote the penetration of electrolyte in the micropores, thereby improving the performance of the battery. In order to achieve the above object, according to one aspect of the present invention, there is provided a phase change composite separator having a thermal shutdown function, the thermal shutdown phase change composite separator being composed of phase change microcapsules and an electrospun fiber membrane. The phase-change microcapsule is a phase-change material with a heat storage function, the electrospun fiber membrane is a polymer membrane with electrolyte affinity, and the phase-change microcapsule is coated on the polymer membrane. Further preferably, the core layer of the phase-change microcapsule is a phase-change material which is not mutually soluble with electrolyte and has a melting temperature of 20-100 ℃, such as one or more of n-docosane, n-tetracosane, 1-tetradecanol, 1-hexadecanol, methyl stearate or ethyl stearate solution. Further preferably, the sheath layer of the phase-change microcapsule is a polymer material which can be melted or converted into a viscous state at 50-150 ℃, such as a copolymer of one or two monomers of polymethyl methacrylate, polyethyl methacrylate, polystyrene and the like. Further preferably, the polymer is one of polyvinylidene fluoride-co-hexafluoropropylene, polyethersulfone and poly m-phenylene isophthalamide, and the excellent high temperature stability provides skeleton supporting function for the composite membrane. Further preferably, the coating thickness of the phase-change microcapsule is 5-20 μm, and the mass ratio is 10% -40%. According to another aspect of the invention, the application of the phase-change composite fiber membrane with the thermal shutdown function in a battery is provided, wherein the membrane is arranged between a positive electrode and a negative electrode of the battery, and the phase-change material in the phase-change composite fiber membrane with the thermal shutdown function regulates heat in the battery and stops the battery when necessary. In summary, compared with the prior art, the above technical solution contemplated by the p