镁硫二次电池单核镁阳离子电解质的设计制备及其性能调控

Rechargeable magnesium-sulfur (Mg/S) batteries have attracted intense attention as the most promising potential technologies for next-generation energy storage due to the advantages of high theoretical energy density, good safety and low cost. However, the lack of effective electrolytes for Mg/S batteries with highly reversible magnesium deposition-dissolution, high conductivity, wide electrochemical window and good compatibility with sulfur leads to the Mg/S technology still quite far away from the theoretical capacity and poor cycle life with rapid capacity decay, which have hindered the development of Mg/S batteries. To solve this main bottleneck, we attemt to employ the control strategy of binding ligand for magnesium cation and central element and its binding groups of anion to construct high-performance mononuclear magnesium cation electrolytes, and further optimizate solvent and electrolyte additive to obtain the improved Mg/S battery electrolytes, utilize a combination of characterization methods such as optical spectroscopy, electron microscopy, and electrochemical analysis and theoretical calculation to address the relationship between the parameters of the electrolyte and the device performance and the electrochemical reaction mechanism of magnesium sulfur batteries. Through these investigations, we aim to obtain advanced Mg/S battry electrolyte for high performance of energy storage. This project not only pioneers a new avenue to develop new magnesium electrolyte materials, but also enrich the content of magnesium battery chemistry.

镁硫电池由于具有高理论储能密度、安全以及价格低廉等优点，因而被认为是下一代极具潜力的先进电池技术。但由于缺乏能够有效进行可逆沉积-溶出金属镁、电导率高、电化学窗口宽并与活性物质硫兼容性好的高效镁硫电池电解液，实际镁硫电池性能远远低于理论值，并且容量衰减快，循环寿命差，严重阻碍了镁硫电池的研发进程。本项目拟采用阳离子配位体和阴离子中心元素及其键合基团调控镁电解质盐结构和性质，进一步通过溶剂、添加剂优化电解液性能，结合电池器件制作和电化学表征，利用光谱、电子显微技术以及理论计算，厘清电解液参数与镁硫电池性能及其电化学反应微观机制之间的规律性关系，最终获得高效镁硫电池电解液，实现高性能镁硫储能体系。本项目既为镁电解质新材料的开发拓展新路，又丰富了镁电池化学的内容。

镁硫电池由于具有高理论储能密度、安全以及价格低廉等优点，因而被认为是下一代极具潜力的先进电池技术。但由于缺乏能够有效进行可逆沉积-溶出金属镁、电导率高、电化学窗口宽并与活性物质硫兼容性好的高效镁硫电池电解液，实际镁硫电池性能远远低于理论值，并且容量衰减快，循环寿命差，严重阻碍了镁硫电池的研发进程。本项目通过调控阳离子配位体和阴离子中心元素及其键合基团，获得了几种镁电解质盐结构，制备了基于镁电解质盐的新型镁电解液，研究了电解液添加剂和溶剂对新型镁电解液以及其电池器件电化学性能的影响规律，探讨了电极/电解液界面改善、极化电压降低、镁电化学沉积和溶解性能以及电池器件性能提升的机理，初步建立了镁电解液参数、电池宏观器件性能以及微观电化学反应机制之间的规律性关系，为高性能镁电解液的深入研究奠定了一些基础。该项目发展的[Mg·6THF][AlCl4]2/LiCl电解液新体系能够显著降低金属Mg电极的电化学过电位，组装的Mg/Mg对称电池在500 μA cm-2的电流密度下过电位仅为140 mV，以NG-NCNT@NCS@S为正极的Mg/S电池在0.4 C的倍率下循环寿命超过500次以上，仍然保持有300 mAh g-1的可逆比容量。