锂-硫二次电池界面反应的特殊性与对策分析

Simple Analysis and Possible Solutions of the Unusual Interfacial Reactions in Li-S Batteries

锂-硫电池是在现有锂离子电池基础上最可能实现储能密度大幅提升的实用二次电池体系.然而,这一电池体系的电化学利用率与循环稳定性仍然难以满足应用要求.造成锂-硫电池性能不稳定的原因在于硫正极和锂负极的材料结构和反应环境始终处于变化之中,如在充放电过程中,硫/碳反应界面的电化学阻塞、中间产物的溶解流失、正负极之间的物质穿梭效应等副反应导致正极与负极均难以形成稳定的电化学反应界面.针对这些特殊问题,本文简要分析了影响能量利用率和循环稳定性的化学与电化学机制,并提出了构建稳定锂负极与高效硫正极的若干可行性技术.

Rechargeable Li-S batteries are a promising power source with realizable energy densities several times higher than current Li-ion batteries. However, the capacity utilization and cycling stability of the existing Li- S technologies are still insufficient for battery applications. The causes for the electrochemical instability of this redox system arise probably from the changes in the surface structures and electrochemical microenvironments of the Li anode and sulfur cathode during charge-discharge reactions ,which includes the frustrated electron transfer in the sulfur-carbon interface, the dissoluble diffusion of the polysulfide intermediates, and the shuttle reaction in- between the sulfur and Li electrodes. To deal with these problems, this paper tries to reveal the underlying chem- istry affecting the charge-discharge stability of Li-S system and describe possible Strategies to construct electro- chemically stable Li anode and sulfur cathode, so as to achieve high efficiency Li-S batteries.