How to improve the conductivity of lithium-sulfur batteries?

In recent years, with the rapid development of mobile electronic equipment, electric vehicles and smart grids, the demand for high-energy-density battery systems has continued to increase. Lithium-sulfur batteries use elemental sulfur or sulfur-containing compounds as the positive electrode, and metal lithium as the negative electrode. The energy storage is based on the multi-electron conversion reaction between sulfur and lithium. Its theoretical energy density is as high as 2600Whkg-1, which is currently commercial lithium cobalt oxide The theoretical energy density of graphite batteries is more than 6 times (387Whkg-1). At the same time, sulfur is rich in natural resources, low in price and environmentally friendly, which is expected to further reduce battery costs and meet the requirements for batteries in the field of electric vehicles and large-scale energy storage. Therefore, the lithium-sulfur battery is considered to be a promising next-generation battery system, and has become a frontier research hotspot in the field of high-specific energy storage devices. Due to the low conductivity of sulfur, the polysulfide, which is the intermediate product of charge and discharge, is easily soluble in the electrolyte, and the volume changes greatly during charge and discharge, lithium-sulfur battery cathodes usually face low active material utilization, poor cycle stability, and low coulombic efficiency. The problem has severely restricted its large-scale commercial application. Improving the conductivity of the sulfur anode How to effectively improve the conductivity of the sulfur anode, inhibit the dissolution of polysulfides and buffer the volume change of the active material, is one of the keys to the development of high-performance lithium-sulfur batteries and ultimately their practical applications. Li Feng, a researcher at the Institute of Metal Research of the Chinese Academy of Sciences, explained to the my country Science Journal: Because carbon materials have the advantages of high conductivity, large surface area, rich pore structure, and diversified structures, they can build an efficient and stable conductive network for sulfur electrodes, and It plays a good role in adsorption and anchoring of polysulfides, and at the same time provides buffer space for the volume expansion of sulfur, thereby effectively improving the utilization rate of active materials, electrochemical reaction kinetics and electrode cycle stability. To this end, based on carbon materials, they focused on the key problems of sulfur cathodes, and proceeded from the construction of carbon material conduction/restriction network, interface regulation and integrated electrode structure design, and optimized the sulfur cathode structure to improve sulfur. Its electrochemical activity inhibits the dissolution and diffusion of polysulfide ions in the electrolyte, and buffers the volume change of sulfur during charging and discharging, providing scientific basis for the design of high energy density and long cycle life lithium-sulfur batteries. In addition to the development of the positive electrode material and electrolyte in the integrated electrode structure design, recent studies have shown that the structure design and improvement of lithium-sulfur batteries can also effectively suppress or eliminate the shuttle effect. Since the battery structure is mainly composed of positive electrode, negative electrode, and separator, the design of adding interlayer between the positive and negative electrodes and the modification of the separator can effectively inhibit the diffusion of polysulfides and the growth of lithium dendrites in the negative electrode, thereby improving the utilization of active materials And new battery cycle life. Using high pore volume graphene as the sulfur carrier, partial graphene oxide as the spacer layer, and highly conductive graphene as the current collector, an all-graphene-based positive electrode structure design was proposed. High pore volume graphene achieves a sulfur content of 80wt% of the electrode material and a sulfur loading of 5mgcm-2 in the electrode. The proper amount of oxygen-containing groups on the surface of partial graphene oxide can effectively adsorb polysulfides and improve the cycle performance of the electrode. The highly conductive graphene current collector can improve the adhesion between the electrode active material and the current collector. At the same time, its light weight helps to increase the overall energy density of the battery. Through the synergistic use of the three graphenes, the all-graphene sulfur cathode can achieve up to 90% of the active material utilization rate and excellent cycle stability. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous post: What are the ways to repair lead-acid batteries?