CN-121394303-B - High-load composite sulfur positive electrode, preparation method thereof and lithium sulfur battery

Abstract

The invention discloses a high-load composite sulfur positive electrode, a preparation method thereof and a lithium sulfur battery, and belongs to the technical field of lithium batteries. The high-load composite sulfur positive electrode comprises a current collector, a carbon/sulfur positive electrode layer positioned on the current collector, wherein the carbon/sulfur positive electrode layer comprises a carbon-sulfur composite material, and a functional polymer layer positioned on the carbon/sulfur positive electrode layer, wherein the functional polymer layer is formed by a polymer containing electron-deficient groups. The invention adopts the polymer with strong electron-deficient groups as the positive electrode protective coating, and utilizes the inherent electron-deficient center of the polymer to adsorb anions and reject cations. The effect of adsorbing anions may prevent the active material from shuttling through the polymer layer toward the negative electrode, resulting in capacity loss. On the other hand, the rejection of cations can promote dissociation of lithium ions from anions in the polymer layer, facilitating lithium ion conduction. Compared with the prior art, the invention solves the problem of cracking of the high-load composite sulfur positive electrode and simultaneously still maintains better ion conductivity and battery capacity.

Inventors

• YANG HUI
• YUE PEIYU
• WANG YIDING
• CHEN DONGXU
• WANG MENG
• YU BO
• LIU GUOFENG

Assignees

• 中国铁塔股份有限公司

Dates

Publication Date

20260512

Application Date

20251225

Claims (9)

1. 1. A high load composite sulfur positive electrode, comprising: A current collector; A carbon/sulfur positive electrode layer on the current collector, the carbon/sulfur positive electrode layer comprising a carbon-sulfur composite material; And a functional polymer layer on the carbon/sulfur positive electrode layer, the functional polymer layer being formed of a polymer containing an electron-deficient group; The polymer containing electron-deficient groups is selected from one or more of poly (pentafluorostyrene), poly (ethylene-alt-maleic anhydride), poly (4-chlorostyrene) or poly (4-bromostyrene).
2. 2. The high load composite sulfur positive electrode according to claim 1, wherein the functional polymer layer has a thickness of 30 to 70 μm.
3. 3. The high load composite sulfur positive electrode according to claim 1 or 2, wherein the sulfur loading of the carbon/sulfur positive electrode layer is 6-12 mg/cm 2 .
4. 4. A method for producing the high-load composite sulfur positive electrode according to any one of claims 1 to 3, comprising the steps of: mixing the carbon-sulfur composite material, the conductive agent, the binder and the first solvent to prepare slurry; coating the slurry on a current collector, drying to form a carbon/sulfur positive electrode layer, and carrying out rolling treatment to obtain a carbon/sulfur positive electrode plate; Dissolving a polymer containing electron-deficient groups in a second solvent to prepare a polymer solution; And coating the polymer solution on the surface of the carbon/sulfur positive electrode plate, and drying to form a functional polymer layer to obtain the high-load composite sulfur positive electrode.
5. 5. The method for producing a high-load composite sulfur positive electrode according to claim 4, wherein the mass concentration of the polymer containing electron-deficient groups in the polymer solution is 25 to 50%; and/or the second solvent is selected from chlorobenzene and/or chloroform.
6. 6. The method for preparing a high-load composite sulfur positive electrode according to claim 4, wherein the pressure of the rolling treatment is 4-8 mpa; and/or the temperature of the drying treatment is 90-110 ℃ and the time is 6-24 hours.
7. 7. The method for preparing a high-load composite sulfur positive electrode according to claim 4, wherein the carbon-sulfur composite material is prepared by a method comprising the steps of: mixing elemental sulfur with a conductive carbon material, and performing first ball milling treatment; sintering the material subjected to the first ball milling treatment under a sealing condition; and carrying out second ball milling treatment on the sintered material to obtain the carbon-sulfur composite material.
8. 8. The method for preparing a high-load composite sulfur anode according to claim 7, wherein the mass ratio of elemental sulfur to conductive carbon material is 1:0.2-0.4; And/or the sintering treatment is carried out at a temperature of 155-180 ℃ for 15-20 hours.
9. 9. A lithium sulfur battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode employs the high-load composite sulfur positive electrode according to any one of claims 1 to 3.

Description

High-load composite sulfur positive electrode, preparation method thereof and lithium sulfur battery Technical Field The invention belongs to the technical field of lithium batteries, and particularly relates to a high-load composite sulfur positive electrode, a preparation method thereof and a lithium sulfur battery. Background The lithium sulfur battery has a theoretical energy density of 2600Wh/kg and is considered as one of the high energy density batteries with great application prospect. However, the sulfur positive electrode used in the current research field has a low load, and the total weight of the battery has a high proportion of inactive substances, resulting in a low actual energy density. In order to promote the transition of the lithium-sulfur battery technology from laboratory basic research to practical application, the sulfur load per unit area on the surface of a single current collector needs to be improved, the ratio of active substances in the battery is improved, the inactive weight is reduced, and the battery energy density is released. The proportion of conductive carbon to be added in the sulfur anode is generally higher than that of a traditional lithium ion battery due to the insulating property of elemental sulfur, and the situation that the dried electrode is easy to crack in the process of improving the anode load, namely the anode coating thickness is improved due to the characteristics of high specific surface area and uneasy compaction of the conductive carbon, so that the uniformity and stability of the battery are not facilitated, and the structural integrity is poor. To cope with this problem, it is generally adopted to add more binder, but because of the insulating property of the binder, coating the carbon-sulfur composite particles with excessive binder causes electron conduction between particles, thereby resulting in failure of the conductive network of the whole thick electrode. And partial areas, especially areas far away from the current collector in the thick sulfur anode, active substances cannot gain and lose electrons through a network formed by the conductive agent, so that the utilization rate of the active materials is low, the capacity cannot be released, and the energy density of the battery cannot be improved. In the prior art, researchers have proposed a scheme of self-supporting porous current collectors, which adopts self-supporting porous current collectors (such as carbonized porous fiber membranes), and then forms a composite self-supporting positive electrode by means of sulfur melting load, thereby realizing high load without using a binder. However, the scheme has the advantages of small synthesis area, incompatibility with the existing commercial battery assembly equipment, complex preparation process, incapability of large scale, low compaction density of a loose porous structure, and overlarge battery volume. In addition, a polymer coating containing inorganic filler is added on the surface of the positive electrode, and the existing polymer coating has limited blocking effect on the shuttle effect of active substances, so that polysulfide can be adsorbed only by adding the inorganic filler as Lewis acid sites, and the process difficulty and the cost are increased. In addition, the existing polymer coating may cause the blocking of lithium ion transmission, so that the conventional scheme selects to add lithium salt into the polymer precursor, thereby improving ion conductivity, however, the lithium salt is easy to absorb water and is expensive, and is not beneficial to actual production, processing and application. Therefore, there is an urgent need in the art to develop a technical solution that not only ensures the structural integrity of the high-load sulfur positive electrode, but also promotes ion transport, effectively inhibits the shuttle effect, and is compatible with the existing commercial battery production process. Disclosure of Invention In order to overcome the defects in the prior art, the main purpose of the invention is to provide a high-load composite sulfur positive electrode, a preparation method thereof and a lithium sulfur battery. In order to achieve the above object, the present invention provides a high-load composite sulfur cathode comprising: A current collector; A carbon/sulfur positive electrode layer on the current collector, the carbon/sulfur positive electrode layer comprising a carbon-sulfur composite material; and a functional polymer layer on the carbon/sulfur positive electrode layer, the functional polymer layer being formed of a polymer containing an electron-deficient group. Further, the polymer containing electron-deficient groups is selected from one or more of poly (pentafluorostyrene), poly (ethylene-alt-maleic anhydride), poly (4-chlorostyrene) or poly (4-bromostyrene). Further, the thickness of the functional polymer layer is 30-70 μm. Further, the sulfur loading of the carbon/sulfur anode layer