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CN-121054629-B - Thick electrode and preparation method and application thereof

CN121054629BCN 121054629 BCN121054629 BCN 121054629BCN-121054629-B

Abstract

The invention discloses a thick electrode, a preparation method and application thereof, and relates to the technical field of secondary batteries. The thick electrode comprises a three-dimensional network structure formed by binder long fibers, active material particles and conductive agent particles filled in the three-dimensional network structure, wherein the thickness of the thick electrode is more than or equal to 300 mu m, the electrode loading of the thick electrode is more than or equal to 20mg/cm 2 , and the mass ratio of the active material particles is more than or equal to 85%. The thick electrode is prepared by simultaneously carrying out electrostatic spinning and electrostatic spraying. The invention prepares the thick electrode by combining electrostatic spinning and electrostatic spraying technology, the thickness of the prepared thick electrode is obviously improved compared with that of the thick electrode prepared by the conventional coating method, and the thick electrode is not cracked. Meanwhile, the rate capability of the electrode can be improved on the basis of no crack.

Inventors

  • ZHU CHANGBAO
  • OUYANG XUAN
  • FANG TAO

Assignees

  • 广东工业大学

Dates

Publication Date
20260508
Application Date
20251103

Claims (5)

  1. 1. A thick electrode characterized by a three-dimensional network structure formed of binder long fibers, and active material particles and conductive agent particles filled in the three-dimensional network structure; the thickness of the thick electrode is more than or equal to 300 mu m; The electrode load of the thick electrode is more than or equal to 20mg/cm 2 ; the mass ratio of the active material particles is more than or equal to 85%; the binder long fibers have an average length >100 μm; The preparation steps of the thick electrode comprise: Depositing binder filaments on a current collector by electrospinning while simultaneously depositing active material particles and conductive agent particles on the current collector by electrostatic spraying, or depositing binder filaments and conductive agent particles on a current collector by electrospinning while simultaneously electrostatic spinning while simultaneously depositing active material particles on the current collector by electrostatic spraying; The method for depositing binder long fibers on a current collector through electrostatic spinning and simultaneously depositing active material particles and conductive agent particles on the current collector through electrostatic spraying comprises the steps of dispersing active material and conductive agent in a solvent 1 to obtain a spray solution, dissolving the binder in the solvent 2 to obtain a spinning solution, placing the current collector on a collecting roller, simultaneously carrying out electrostatic spinning and electrostatic spraying to simultaneously deposit binder long fibers, active material particles and conductive agent particles on the current collector, and drying after deposition is finished to obtain the thick electrode; The method for depositing binder long fibers and conductive agent particles on a current collector through electrostatic spinning and simultaneously depositing active material particles on the current collector through electrostatic spraying comprises the steps of dispersing active materials in a solvent 1 to obtain a spray solution, dissolving a binder and a conductive agent in a solvent 2 to obtain a spinning solution, placing the current collector on a collecting roller, simultaneously carrying out electrostatic spinning and electrostatic spraying to simultaneously deposit binder long fibers, active material particles and conductive agent particles on the current collector, and drying after deposition is finished to obtain the thick electrode; The binder comprises polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polystyrene, polyurethane or cellulose acetate; The solvent 1 is a solvent which does not dissolve the binder and can disperse the active material and the conductive agent, and the solvent 2 is a solvent which can dissolve the binder.
  2. 2. The thick electrode of claim 1, wherein the binder long fibers have a diameter of 50 to 1000nm.
  3. 3. The thick electrode of claim 1, wherein the ratio of the average length of the binder long fibers to the average particle size of the active material particles is >100.
  4. 4. Use of a thick electrode according to any one of claims 1-3 in the manufacture of a secondary battery.
  5. 5. A secondary battery comprising the thick electrode according to any one of claims 1 to 3 as a working electrode.

Description

Thick electrode and preparation method and application thereof Technical Field The invention relates to the technical field of secondary batteries, in particular to a thick electrode, a preparation method and application thereof. Background In order to increase the energy density of secondary batteries, it is a common and effective strategy to prepare thick electrodes. Reducing the inert ingredient ratio by increasing the active material loading (e.g., >10mg/cm 2) is an effective way to increase the energy density of the battery. The thick electrode technology also significantly reduces the production cost of the battery, and thus becomes a research hotspot in the industry. However, there are difficulties in preparing thick electrodes by conventional casting methods. For example, electrodes using polyvinylidene fluoride (PVDF) as a binder are prone to cracking due to capillary forces when dried, and maximum crack-free thickness is about 127 μm beyond which the electrode is extremely prone to cracking, and PVDF is prone to migration and agglomeration after dissolution, disrupting the conductive network. In current commercial lithium ion batteries, the thickness of the electrodes, including the cathode and anode, is limited to between 50-100 μm. Therefore, development of novel thick electrode preparation technology is urgently needed. In addition, the increase in electrode thickness causes a significant decrease in the rate capability of the thick electrode, which constitutes an obstacle to its commercial application, and therefore development of a thick electrode that ensures ion/electron transport and a new technique for preparing the same are required. Disclosure of Invention The invention aims to provide a thick electrode, a preparation method and application thereof, so as to solve the problems in the prior art. The conventional tape casting method has the problems that (1) the mechanical stability of the electrode is poor, the conductive agent and the binder are diffused to the surface of the electrode under the action of capillary stress in the drying process to form an aggregate, the mechanical property is damaged, and the electrode is easy to crack along with the increase of the thickness, and (2) the electrochemical property of the electrode is poor, namely the high-load electrode can increase the thickness of an electrode film, so that the diffusion distance of charges in the electrode is increased. In the electrochemical process, the longer the charge diffusion distance, the lower the mass transfer efficiency, resulting in poor electrochemical performance. Based on the above problems, the invention aims to (1) improve the mechanical stability of the electrode, namely, increase the thickness of the electrode and ensure that the electrode is not cracked, and (2) enhance the electrochemical performance of the electrode, namely, improve the multiplying power performance of the electrode on the basis of no crack. In order to achieve the above object, the present invention provides the following solutions: One of the technical solutions of the present invention is a thick electrode comprising a three-dimensional network structure formed of binder long fibers (continuous filaments having high continuity), and active material particles and conductive agent particles filled in the three-dimensional network structure (the structure of the thick electrode is schematically shown in fig. 1); the thickness of the thick electrode is more than or equal to 300 mu m; The electrode load (i.e. the mass of active substances loaded on the electrode in unit area) of the thick electrode is more than or equal to 20mg/cm 2; The mass ratio of the active material particles is more than or equal to 85 percent (namely, the mass of the active material particles/(the mass of the binder long fibers+the mass of the active material particles+the mass of the conductive agent particles). Times.100 percent is more than or equal to 85 percent), namely, the mass of the active material/(the mass of the binder+the mass of the active material+the mass of the conductive agent). Times.100 percent is more than or equal to 85 percent) in the raw materials. The binder long fibers form a three-dimensional network structure, active substance particles and conductive agent particles are uniformly filled (i.e. uniformly distributed) in the three-dimensional network structure of the binder long fibers, and the special structure can effectively improve the mechanical strength of the thick electrode and ensure that the thick electrode sheet is not cracked, similar to the situation that the root system of a plant tightly grabs soil. Meanwhile, the structure can ensure that the active substances, the conductive agent and the binder long fibers are in point/line contact, so that ion transmission pores are not blocked, and the improvement of rate performance is facilitated. Preferably, the thickness of the thick electrode is 300-1000 μm. Preferably, the e