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CN-121983519-A - Porous modification layer, preparation method thereof, positive plate and battery

CN121983519ACN 121983519 ACN121983519 ACN 121983519ACN-121983519-A

Abstract

The application provides a porous modification layer and a preparation method thereof, an anode plate and a battery, wherein the preparation method of the porous modification layer comprises the following steps of mixing a conductive agent, a binder, a pore-forming agent and a solvent to obtain a mixture; extruding and rolling the mixture to obtain a film layer, extracting the film layer by using an extracting agent to remove a pore-forming agent and a solvent in the film layer, and drying to remove the extracting agent in the film layer to obtain the porous modification layer, wherein the pore-forming agent comprises at least one of citric acid, sodium bicarbonate and sodium carbonate, the solvent comprises polyalcohol, and the extracting agent comprises water. According to the application, the pore-forming agent which can be dissolved in water and is insoluble in polyhydric alcohol and has high solubility is selected, the solvent which can be mutually dissolved with water in any proportion is selected, and water is selected as the extractant, so that the pore-forming agent can be quickly and maximally dissolved in the extractant water in the extraction process, the removal rate of the polyhydric alcohol solvent can reach more than 99%, and the porosity of the porous modification layer is improved.

Inventors

  • DENG HUIHUI
  • QIU LIDA
  • LI LE
  • CAO LANG

Assignees

  • 惠州亿纬锂能股份有限公司

Dates

Publication Date
20260505
Application Date
20251211

Claims (11)

  1. 1. The preparation method of the porous modification layer is characterized by comprising the following steps of: mixing a conductive agent, a binder, a pore-forming agent and a solvent to obtain a mixture; extruding and rolling the mixture to obtain a film layer; Extracting the membrane layer by using an extracting agent to remove the pore-forming agent and the solvent in the membrane layer, and drying to remove the extracting agent in the membrane layer to obtain a porous modification layer; Wherein the pore-forming agent comprises at least one of citric acid, sodium bicarbonate and sodium carbonate, the solvent comprises a polyol, and the extractant comprises water.
  2. 2. The method for producing a porous modified layer according to claim 1, wherein the mass ratio of the conductive agent, the binder, the pore-forming agent and the solvent in the mixture is 18 to 36:2 to 4:3 to 9:60 to 80, and/or, The conductive agent comprises at least one of acetylene black, carbon nano tube, carbon fiber, graphite and graphene, and/or, The binder includes at least one of polytetrafluoroethylene powder, polyvinylidene fluoride powder, polyethylene oxide powder and ultra-high molecular weight polyethylene powder, and/or, The polyol includes at least one of glycerol, 1, 3-propanediol, 1, 2-propanediol, and ethylene glycol.
  3. 3. The method for producing a porous modified layer according to claim 1 or 2, wherein the polyol has a viscosity of 0.01Pa at ordinary temperature S~1.50Pa S, the boiling point of the polyol is 180-300 ℃, and the polyol and the extractant can be mutually dissolved in any proportion.
  4. 4. A method for producing a porous modified layer according to any one of claims 1 to 3, wherein the pore-forming agent has a particle diameter of 5 μm to 15 μm and/or, The thickness of the porous modification layer is 50-100 mu m.
  5. 5. The method of producing a porous modified layer according to any one of claims 1 to 4, wherein the step of uniformly mixing the conductive agent, the binder, the pore-forming agent and the solvent to obtain a mixture comprises: mixing the conductive agent, the binder and the pore-forming agent, adding the solvent, mixing to obtain the mixture in a bulk form, and/or, The step of extruding and rolling the mixture to obtain a film layer comprises the following steps: extruding the mixture through an extruder to form a coarse film, and then rolling and forming the coarse film through a roller press to obtain the film layer, and/or, After the membrane layer is subjected to extraction and drying treatment, the preparation method of the porous modification layer further comprises cold press shaping of the membrane layer.
  6. 6. The porous modification layer is prepared by the preparation method of the porous modification layer according to any one of claims 1-5, and is characterized in that the porosity of the porous modification layer is 70% -80%.
  7. 7. The porous modifying layer of claim 6, wherein the porous modifying layer comprises 85 wt.% to 95 wt.% of the conductive agent and 5 wt.% to 15 wt.% of the binder, and/or, The porous modifying layer has a compacted density of 0.3g/cm 3 ~0.4g/cm 3 , and/or, The tensile strength of the porous modification layer is 45 kPa-70 kPa.
  8. 8. A positive electrode sheet comprising a positive electrode active material layer and a porous modified layer which are stacked, wherein the porous modified layer is prepared by the method for preparing a porous modified layer according to any one of claims 1 to 5 or the porous modified layer according to claim 6 or 7, and the porous modified layer is disposed so as to face a negative electrode sheet.
  9. 9. The positive electrode sheet according to claim 8, wherein the positive electrode active material layer in the positive electrode sheet contains manganese dioxide.
  10. 10. A battery comprising a negative electrode sheet and the positive electrode sheet of claim 9 or 10, wherein the porous finishing layer is disposed toward the negative electrode sheet.
  11. 11. The battery of claim 10, further comprising a separator disposed between the porous finish of the negative and positive plates and/or, The capacity of the battery is 220 mAh-250 mAh.

Description

Porous modification layer, preparation method thereof, positive plate and battery Technical Field The application relates to the technical field of batteries, in particular to a porous modification layer, a preparation method thereof, a positive plate and a battery. Background Lithium-manganese batteries are widely used in electronic devices by virtue of high energy density, wide operating temperature range, good long-term storage stability, low self-discharge rate, and the like. In the positive electrode of the lithium-manganese battery, due to the crystal structure and high compaction density of the positive material, the electrolyte wettability of the positive electrode is poor, and in order to improve the electrolyte wettability of the positive electrode, a porous membrane is usually arranged on the positive electrode side of the battery. However, the pore-forming agent used for preparing the porous membrane in the related art is generally a high molecular polymer, and the solubility of the high molecular polymer is relatively poor, so that the high molecular polymer is difficult to remove in the pore-forming process, and the porosity of the obtained porous membrane is low. Disclosure of Invention The application provides a porous modification layer, a preparation method thereof, a positive plate and a battery, and aims to solve the problem that the porosity of the porous modification layer obtained by adopting a high molecular polymer as a pore-forming agent is low. In a first aspect, an embodiment of the present application provides a method for preparing a porous modification layer, including the steps of: mixing a conductive agent, a binder, a pore-forming agent and a solvent to obtain a mixture; Extruding and rolling the mixture to obtain a film layer; extracting the membrane layer by using an extracting agent to remove a pore-forming agent and a solvent in the membrane layer, and drying to remove the extracting agent in the membrane layer to obtain a porous modification layer; wherein the pore-forming agent comprises at least one of citric acid, sodium bicarbonate and sodium carbonate, the solvent comprises polyalcohol, and the extractant comprises water. The preparation method comprises the steps of firstly mixing a conductive agent, a binder, a pore-forming agent and a solvent to obtain a mixture, then extruding the mixture to obtain a coarse film, rolling the coarse film further to optimize the structure of the coarse film to obtain a film layer, extracting the obtained film layer by an extractant to enable the pore-forming agent and the solvent in the film layer to be maximally dissolved in the extractant for removal, and drying to remove the extractant in the film layer to obtain the porous modified layer with excellent microstructure and good performance. According to the application, small molecules which can be dissolved in water and are insoluble in polyol, high-solubility citric acid, sodium bicarbonate and sodium carbonate are selected as pore formers, polyol which can be mutually dissolved with water in any proportion is selected as a solvent, water is selected as an extractant, in the extraction process, the pore formers can be quickly and furthest dissolved in the extractant water, the removal rate of the polyol solvent can reach more than 99%, and the porosity of the porous modification layer is improved. In an embodiment, the mass ratio of the conductive agent, the binder, the pore-forming agent and the solvent is 18-36:2-4:3-9:60-80, and/or the conductive agent comprises at least one of acetylene black, carbon nanotubes, carbon fibers, graphite and graphene, and/or the binder comprises at least one of polytetrafluoroethylene powder, polyvinylidene fluoride powder, polyethylene oxide powder and ultra-high molecular weight polyethylene powder, and/or the polyol comprises at least one of glycerol, 1, 3-propanediol, 1, 2-propanediol and ethylene glycol. According to the application, the porous modification layer with high conductivity, high mechanical property, high porosity and high compaction density is obtained by reasonably controlling the mass ratio of the conductive agent, the binder, the pore-forming agent and the solvent in the mixture, the conductivity of the porous modification layer can be improved by selecting the carbon material with high conductivity as the conductive agent, the conductive agent is firmly adhered to the bonding fibers by selecting the binder easy to be fibrillated, the mechanical strength of the porous modification layer is improved, the bonding fibers formed in the fibrillation process of the binder are protected and wetted by selecting the polyol with certain viscosity, the further fibrosis of the binder is promoted, and the performance of the porous modification layer is improved under the mutual cooperation of the solvent and the binder. In one embodiment, the polyol has a viscosity of 0.01Pa at ambient temperatureS~1.50PaS, the boiling point of the