A functional separator for lithium-sulfur batteries, its preparation method and application in lithium-sulfur batteries

Abstract

The invention relates to a functional diaphragm for a lithium-sulfur battery, a preparation method and application thereof, belonging to the technical field of electrochemistry. The functional diaphragm of the present invention is composed of a polymer diaphragm substrate and a functional modification layer coated on one side of the polymer diaphragm substrate; wherein: the functional modification layer includes a binder, a conductive carbon material and a dendrite branched macromolecules. The binder of the present invention has good bonding ability and high stability; the conductive carbon material has a high electron conduction rate, which can improve the utilization rate of active materials and greatly reduce the internal impedance of the battery; the dendritic branching Macromolecules contain more organic functional groups, which can chemically adsorb polysulfides generated in the sulfur cathode region during cycling, and carbon materials can physically adsorb dissolved polysulfides, thus effectively inhibiting the "shuttle effect" in lithium-sulfur batteries. ". Therefore, lithium-sulfur batteries prepared using the functional separator described in the present invention exhibit excellent cycle performance and rate capability.

Description

technical field [0001] The invention relates to the technical field of electrochemistry, in particular to a functional diaphragm for a lithium-sulfur battery, a preparation method thereof, and a lithium-sulfur battery assembled from the functional diaphragm for a lithium-sulfur battery. Background technique [0002] With the rapid economic growth, people's demand for energy is increasing day by day. At present, the problem of environmental pollution caused by non-renewable energy consumption is imminent. Therefore, the effective conversion and storage of renewable energy has become a current research hotspot. [0003] Secondary batteries are one of the most convenient and feasible ways to store electrical energy. Lithium-sulfur battery is a secondary energy storage power source composed of sulfur as the positive electrode and metallic lithium as the negative electrode. Lithium-sulfur batteries use the oxidation-reduction process between metal lithium and sulfur to achieve...

AI Technical Summary

Problems solved by technology

The "shuttle effect" is a special feature of lithium-sulfur batteries. It is one of the main reasons for the capacity fading of lithium-sulfur batteries. The application value of sulfur batteries is greatly reduced

[0005] In order to solve the above problems, research work at home and abroad in recent years has mainly focused on three aspects: optimizing the electrolyte system, protecting the negative electrode and modifying the positive electrode material: (1) Optimizing the electrolyte system, such as adding additives such as lithium nitrate to the ether electrolyte It can well inhibit the occurrence of "shuttle effect", thereby improving the coulombic efficiency of the battery; (2) protect the lithium metal negative electrode, and isolate lithium from polysulfides by coating a protective film on the lithium surface of the negative electrode, and inhibit sulfur And the self-discharge consumption of polysulfide and metal lithium, thereby improving the cycle stability of the battery, but later found that as the charge and discharge progress, the structure of the protective film is gradually destroyed, the Coulombic efficiency of the battery gradually decreases, and the capacity decays seriously; (3 ) to modify the positive electrode material, such as preparing a composite material of sulfur and other substances as the positive electrode material, but the preparation process of the complex porous carbon structure is complicated, the pore size is difficult to control, and the porous structure of the carbon material has limited adsorption capacity for polysulfides. Preparation of composite cathode materials with high sulfur loading

In summary, these technologies can improve the utilization rate of sulfur to a certain extent, and have limited effect on improving battery performance, but they have not fundamentally solved the problem of polysulfide dissolution and shuttling, and battery performance still needs to be improved.

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