石榴石陶瓷电解质全固态锂硫电池中电解质-电极界面稳定性调控机制

In garnet type ceramic electrolyte base solid state lithium sulfur battery, the lithium ion transportation and electrochemical reaction mainly occurs at the interface of “electrolyte (solid)-electrode (solid)”, thus the interface stability affect the battery cycling stability significantly. To ensure the performance stability of battery, the interface stability need to be improved through eliminating interfacial gaps and reducing the interfacial resistant. This project systematically investigates the stability regulation of electrolyte-electrode interface by experiment and simulation method to explore the key factors affecting the interfacial stability. Fabrication regulation of garnet electrolyte is conducted to improve the conductivity and density, providing a solid foundation for interfacial modification. Different interfacial coating materials (lithated and not lithiated materials) and organic-inorganic compound film is explored as interfacial modification materials to improve the interfacial stability, including the interfacial resistant, transportation and diffusion of lithium ion, volume variation and electric field distribution at interface, thus investigating the mechanism of interfacial modification. In-situ measurement is conducted to demonstrate the sulfur micro structure evolution during electrochemical cycling in different composite structure of solid electrolyte and sulfur, thus demonstrating the sulfur fixing mechanism and searching the optimal strategy. Electrochemical measurement of battery after modification is conducted to verify the effect of interfacial stability regulation.

在石榴石陶瓷电解质全固态锂硫电池中，“电解质（固）-电极（固）”组成的界面是锂离子输运和发生电化学反应的重要场所，界面稳定性直接影响着电池的循环稳定性。为了保证电池稳定运行，需要消除界面缝隙和降低界面阻抗以提高其稳定性。本项目采用实验和仿真相结合的方法系统研究电解质-电极界面的稳定性调控，探索影响界面稳定的关键因素；研究石榴石陶瓷电解质的制备工艺以提高其电导率和致密度，为界面改性提供保障；采用不同的界面涂层材料（锂化和不可锂化两种材料）和有机复合电解质层作为改性材料研究电解质-锂负极界面稳定性，包括界面电阻、锂离子在界面处的输运和扩散、界面处体积变化和电场分布等，解析界面改性的作用机制；采用原位测量手段表征电解质与硫的不同兼容性结构在电化学循环过程中硫的微观结构演变，阐明不同复合结构中的固硫机制，寻找最优复合策略；对改性后的电池进行电化学测试，验证界面稳定性的调控作用。

在石榴石陶瓷电解质全固态锂硫电池中，电化学反应发生在由“电解质（固）-电极（固）”组成的界面处，界面稳定性直接影响着电池的循环稳定性。为了保证电池稳定运行，需要消除界面缝隙和降低界面阻抗以提高界面稳定性。按照预期研究目标，本项目系统研究电解质-电极界面处的稳定性调控，包括石榴石陶瓷电解质工艺和性能调控，电解质-硫正极界面调控和电解质-锂负极界面调控。主要开展了以下三方面研究工作：首先，开展了LLZO电解质制备工艺对晶粒、电导率和致密度等性能影响研究，探索出一条适合大批量生产高性能固态电解质的的工艺，实现了高致密度、高电导率的异形件烧结成型，已经可以稳定生产烧结后质量约100g时，致密度达98.6%的陶瓷管，性能指标在行业内处领先地位；其次，在不同界面涂层特性对LLZO/Li界面处锂离子输运机理影响研究方面，提出了一种在高于380ºC温度下，使LLZO由疏锂到亲锂转变的这种高温浸润机制，通过高温液锂润湿石榴石并通过快速冷却即可得到好的石榴石-锂“固-固”界面，实现界面面阻抗低达2.5Ω cm2；最后，开展了固态电解质锂硫电池性能调控研究，利用“液-固-液”电池结构提高了界面稳定性和固硫效果，开发了固态电解质熔融锂硫电池，电池在30mA/cm2电流密度下能量效率达85%以上，且能有效阻挡正负极物质穿梭，实现99.99%的库伦效率。以上研究成果为推动石榴石陶瓷电解质全固态锂硫电池的应用奠定坚实的理论与实验基础。