Study On Preparation And Performance Of Gel Coating For Lithium Sulfur Battery

Lithium-sulfur?Li-S?batteries,using abundant element sulfur in natural reserves as active materials,have become one kind of rechargeable lithium secondary batteries with high energy density and great promising prospects due to their low cost and environmental friendliness.However,the commercialization of Li-S batteries still faces severe challenges,which can be basically included in the following aspects:?1?The intermediate polysulfides produced during discharge process dissolves in the electrolyte and easily diffuses to anode to form the shuttle effect,which results in a series of negative impacts,including loss of active materials,severe degradation of Li metal,internal self-discharge,and deposition of insulating products;?2?Both S and Li₂S are electronic and ionic insulators at room temperature,which makes the material conversion difficult and the utilization rate low;?3?The considerable volume change during lithiation/delithiation may destroy the stability and even failure of the electrode structure.To address the above problems,based on the recent reviews of lithium sulfur batteries,we designed and prepared a unique gel coating sulfur cathode,which selects gel electrolyte according to the actual requirements of Li-S batteries and combines gel electrolyte with sulfur cathode as an extra coating The prepared coating cathode with gel electrolyte significantly improves the electrochemical performance of Li-S battery.Also,we studied the physical and chemical properties of the gel coating,and the impact on the electrochemical performance of the sulfur cathode and the reaction mechanism through different test methods.In this paper,PAM/PAA gel was prepared by blending.The gel material was mixed with S/C material to prepare an electrode.The prepared gel material can absorb the electrolyte to gel on the surface of S electrode and improve the structure stability of the electrode.Also,the gel material is electrochemically stable within the operating voltage range of the Li-S battery without decomposition.Moreover,the gelation reduces the charge transfer resistance R_ct of the electrode,which is beneficial to improve the electrochemical performance of Li-S batteries.The gel electrolyte prepared by copolymerization material P?AM-co-AA?,working as coating cathode in Li-S batteries,shows excellent electrochemical performance.At a current density of 0.2 C,the initial specific capacity reached 1101 mAh·g^-1.After 100 cycles,the reversible capacity still remains at 822 mAh·g^-1,and the cycle retention rate is 75.19%.Studies have shown that this improvement is mainly due to the porous network structure and polar functional groups of the electrolyte membrane,which can fix polysulfide via the physical-chemical action and inhibit the shuttle effect,thus significantly improving the performance of Li-S battery.A novel PEO/P?AM-co-AA?/PEDOT:PSS multifunctional gel electrolyte was prepared by a blending method.The gel membrane owns enough electronic and ionic conductivity,uniform membrane-forming,and good mechanical properties.The Li-S batteries using electrode with this conductive gel electrolyte coating exhibit excellent electrochemical performance.At a current density of 0.2 C,with a high-load S/C composite material,the cycle retention rate is 80%during the first 90 cycles,which is much higher than uncoated cell.The retention rate is 59.53%after 300 cycles.Studies have shown that PEO/P?AM-co-AA?/PEDOT:PSS blended functional gel electrolyte can significantly improve the electrode surface.It is mainly due to the combination of sulfur-fixing ability and catalytic function of the coating,which can also improve the reaction kinetics of the battery while anchoring the polysulfide.