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CN-115863902-B - Separator, preparation method thereof, secondary battery and electric equipment

CN115863902BCN 115863902 BCN115863902 BCN 115863902BCN-115863902-B

Abstract

The invention provides a diaphragm and a preparation method thereof, a secondary battery and electric equipment, wherein the diaphragm comprises a base film and a ceramic coating arranged on at least one surface of the base film, the ceramic coating comprises a binder and inorganic particles, the swelling degree of the diaphragm soaked in an organic solvent for 24 hours is 0.1% -6%, the organic solvent is a mixed solvent of ethylene carbonate, dimethyl carbonate and diethyl carbonate, and the mass ratio of the ethylene carbonate, the dimethyl carbonate and the diethyl carbonate in the mixed solvent is 2:2:1. The diaphragm has the characteristics of good thermal stability, low impedance and difficult falling of a ceramic coating, and has wide application prospect.

Inventors

  • LIN FENG
  • LI YANLING
  • LI CHAORONG
  • CHEN JIQIN
  • CHENG ZHONG

Assignees

  • 欣旺达电动汽车电池有限公司

Dates

Publication Date
20260508
Application Date
20221130

Claims (9)

  1. 1. The diaphragm is characterized by comprising a base film and a ceramic coating layer arranged on at least one surface of the base film, wherein the ceramic coating layer comprises a binder with a cross-linked network structure and inorganic particles dispersed in the cross-linked network structure, the swelling degree of the diaphragm soaked in an organic solvent for 24 hours is 0.1% -6%, the organic solvent is a mixed solvent of ethylene carbonate, dimethyl carbonate and diethyl carbonate, and the mass ratio of the ethylene carbonate, the dimethyl carbonate and the diethyl carbonate in the mixed solvent is 2:2:1; The adhesive comprises one or more of acrylic polymers, styrene-butadiene polymers, polyurethane modified acrylic polymers, epoxy polymers or acrylamide modified acrylic polymers containing hydrophilic groups, wherein the hydrophilic groups comprise at least one of -COO - NH 4 + 、-COO - Na + 、-COO - Li + 、-COO - K + 、-SO 3 - NH 4 + 、-SO 3 - Na + 、-SO 3 - Li + and-SO 3 - K + ; The glass transition temperature of the binder is 40-180 ℃; The binder is formed from a binder prepolymer that can undergo a self-crosslinking reaction.
  2. 2. The membrane of claim 1, wherein the binder has a swelling degree of 5% -200% when immersed in an organic solvent for 24 hours.
  3. 3. The diaphragm of claim 1 wherein the diaphragm meets at least one of the following conditions: (1) The peeling strength of the ceramic coating is 15N/m-35N/m; (2) The diaphragm is kept stand for 1h at 100 ℃ and the heat shrinkage rate in the longitudinal direction is T1%, wherein T1 is more than or equal to 0 and less than or equal to 0.7; (3) The diaphragm is kept stand for 1h at 100 ℃ and the heat shrinkage rate in the transverse direction is T2%, wherein T2 is more than or equal to 0 and less than or equal to 0.6; (4) The membrane impedance is less than or equal to 0.9 ohm; (5) The conductivity of the diaphragm is 1 ms/cm-1.6 ms/cm.
  4. 4. The separator of claim 1, wherein the inorganic particles comprise at least one of silica, aluminum oxide, boehmite, zirconia, titania, barium sulfate, calcium sulfate.
  5. 5. A method for preparing a diaphragm, which is used for preparing the diaphragm according to any one of claims 1-4, and is characterized by comprising the following steps of coating at least one surface of a base film with slurry comprising inorganic particles and a binder prepolymer, and obtaining the diaphragm after crosslinking and curing.
  6. 6. The method of producing a separator according to claim 5, wherein the binder prepolymer includes a crosslinking functional group including at least one of a carbon-carbon unsaturated bond, a siloxane group, and an isocyanate group.
  7. 7. The method for producing a separator according to claim 5, wherein the number average molecular weight of the binder prepolymer is 1000 to 20000.
  8. 8. A secondary battery comprising the separator according to any one of claims 1 to 4 or the separator produced by the production method according to any one of claims 5 to 7.
  9. 9. A powered device comprising the secondary battery of claim 8.

Description

Separator, preparation method thereof, secondary battery and electric equipment Technical Field The invention relates to the field of secondary battery diaphragms, in particular to a diaphragm, a preparation method thereof, a secondary battery and electric equipment. Background The diaphragm has the functions of providing an ion transmission channel and isolating the anode and the cathode from physical contact short circuit. The ceramic diaphragm used in the current market has larger size shrinkage under the high-temperature condition, and serious ignition and explosion failure easily occur in overcharge, short circuit or heating of the battery, so that the safety of the battery cannot meet the requirements. In addition, the ceramic layer is easy to fall off when the battery is wound, laminated or soaked in electrolyte, so that the safety risk is high, and the resistance of the adhesive component in the ceramic layer is high after the adhesive component is swelled by the electrolyte, so that the power requirement of the battery cannot be met. Accordingly, it is necessary to provide a separator to meet the safety and power requirements of the battery. Disclosure of Invention Therefore, the technical problem to be solved by the invention is to overcome the defect of poor reliability of the diaphragm in the prior art, thereby providing a diaphragm, a preparation method thereof, a secondary battery and electric equipment. The first aspect of the invention provides a diaphragm, which comprises a base film and a ceramic coating arranged on at least one surface of the base film, wherein the ceramic coating comprises a binder and inorganic particles, the swelling degree of the diaphragm after being soaked in an organic solvent for 24 hours is 0.1% -6%, the organic solvent is a mixed solvent of ethylene carbonate, dimethyl carbonate and diethyl carbonate, and the mass ratio of the ethylene carbonate, the dimethyl carbonate and the diethyl carbonate in the mixed solvent is 2:2:1. Optionally, the swelling degree of the binder after soaking in an organic solvent for 24 hours is 5% -200%. Optionally, the glass transition temperature of the binder is 40 ℃ to 180 ℃. Optionally, the peel strength of the ceramic coating is 15N/m-35N/m. Alternatively, the diaphragm has a heat shrinkage rate T1% in the longitudinal direction of 0≤T1≤0.7 when left standing at 100℃for 1 h. Alternatively, the diaphragm has a heat shrinkage rate T2% in the transverse direction of 0≤T2≤0.6 when left standing at 100 ℃ for 1 h. Optionally, the membrane impedance is less than or equal to 0.9 ohm. Optionally, the membrane conductivity is 1 ms/cm-1.6 ms/cm. Optionally, the binder includes one or more of an acrylic polymer, a styrene-butadiene polymer, a polyurethane modified acrylic polymer, an epoxy polymer, or an acrylamide modified acrylic polymer that includes a hydrophilic group, the hydrophilic group including at least one of -COO-NH4+、-COO-Na+、-COO-Li+、-COO-K+、-SO3-NH4+、-SO3-Na+、-SO3-Li+ and-SO 3-K+. Optionally, the inorganic particles comprise at least one of silica, alumina, boehmite, zirconia, titania, barium sulfate, and calcium sulfate. In a second aspect, the invention provides a method for preparing a separator, which is used for preparing the separator, and comprises the following steps of coating slurry comprising inorganic particles and a binder prepolymer on at least one surface of a base film, and obtaining the separator after crosslinking and curing. Optionally, the binder pre-polymer comprises cross-linking functionality comprising at least one of carbon-carbon unsaturation, siloxane groups, isocyanate groups. Optionally, the number average molecular weight of the binder prepolymer is 1000-20000. A third aspect of the present invention provides a secondary battery comprising the foregoing separator or a separator manufactured by the foregoing manufacturing method. A fourth aspect of the present invention provides an electric device comprising the aforementioned secondary battery. The technical scheme of the invention has the following beneficial effects: The diaphragm comprises the base film and the ceramic coating arranged on the base film, wherein the ceramic coating comprises the binder and the inorganic particles, the ceramic coating has strong supporting effect on the base film when the diaphragm is heated, the change of the heated size of the diaphragm is small, the thermal safety performance of the diaphragm is improved, meanwhile, the diaphragm has small swelling degree in an organic solvent, the structure is not easy to collapse when the diaphragm is corroded by the organic solvent, and the integral impedance of the diaphragm is small. Drawings In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings of the embodiments will be briefly described below, and it is apparent that the drawings in the following description relate only to some embodiments of the present