新型多功能Solvent-in-Salt电解质与高比能锂硫电池研究

Li-S battery based on a two-electron transfer reaction mechanism has become a worldwide hot research topic because its energy density is 3-5 times higher than those of current-state-of-art lithium ion batteries. However, there are still two big challenges which limit the practical application: the dissolution of polysulfides produced upon discharge into liquid electrolyte and the formation of lithium dendrite during cycling. In this project, we propose a new class of Solvent-in-Salt (SIS) electrolyte and optimize the composition to realize the multi-functions in Li-S battery: inhibition of the dissolution of polysulfides, inhibition of the growth of lithium dendrite, non-flammability, etc. We will investigate the physico-chemical properties of SIS electrolyte and the Li+ ion conduction mechanism. Then the interface property and structure between SIS electrolyte and lithium anode will be studied in detail by various in situ techniques. Furthermore, the electrochemical properties of the prepared C/S composite cathode material with mixed conducting network will be investigated thoroughly in SIS electrolyte and its lithium storage mechanism will also be studied by many in situ techniques. On the basis of above work, finally we will make soft package of Li-S batteries and evaluate their discharge capacity, energy density, cycling behavior, rate performance to verify the effectiveness of this new class of SIS electrolyte in real battery. We believe that the expected results will pave the way for the practical application of Li-S battery.

基于两电子反应的锂硫二次电池的能量密度是现有锂离子电池体系的三到五倍，成为目前全世界研究热点。制约锂硫电池实际应用的两个核心技术难题为：在充放电过程中如何抑制中间产物多硫离子的溶解和如何稳定金属锂负极避免产生锂枝晶。本项目提出一种新型多功能"Solvent-in-Salt" (SIS)电解质，通过优化其组成，实现其能抑制多硫离子溶解、防止锂枝晶生长和难燃等功能，并深入研究其物理化学性能和离子导电传输机制及其影响因素；原位研究SIS电解质与金属锂基负极的界面特性包括SEI膜组成、结构、锂负极循环效率和锂枝晶生长影响因素；具有混合导电网络的高容量C/S复合正极材料与SIS电解质兼容性研究及其储锂机制原位研究；在此基础上，研制软包锂硫电池，系统评价各项性能包括放电容量、能量密度、循环性能、倍率性能等，验证提出的多功能SIS电解质的实效性。预期研究成果将为锂硫电池走向实际应用奠定基础。

基于两电子反应的锂硫二次电池的能量密度是现有锂离子电池体系的三到五倍，成为目前全世界研究热点。本项目提出一种新型多功能“Solvent-in-Salt”(SIS)电解质，通过优化其组成，实现其能抑制多硫离子溶解、防止锂枝晶生长和难燃等功能，并深入研究其物理化学性能和离子导电传输机制及其影响因素，筛除出综合性能较好的组成：1M LiTFSI+ 2M LFSI in DOL：DME（1：1 in volume）；研究了SIS电解质与金属锂基负极的界面特性包括SEI膜组成、结构、锂负极循环效率和锂枝晶生长影响因素；具有混合导电网络的高容量C/S 复合正极材料与SIS电解质兼容性研究及其储锂机制原位研究，C/S复合正极比容量可达1000mAh/g且具有优异的循环性能；在此基础上，研制锂硫软包电池和三元NCA-金属锂软包电池，系统评价各项性能包括放电容量、能量密度、循环性能、倍率性能、安全性能等，能量密度可以达到300-350Wh/kg，循环寿命100周以上，证明多功能SIS电解质在软包电池中性能良好。研究成果将为金属锂电池走向实际应用奠定基础。