锂硫电池循环过程中变形演化的直接观测

Direct View for the Deformation Evolution of Sulfur Electrode during Li-S Battery Cycling

实验设计了一种可实时原位观测锂硫电池电极变形及电化学反应过程的实验装置。实验中观测到充放电过程中的硫电极的弯曲形变,发现放电过程中硫正极形变增大,曲率增大,静置和充电过程中形变逐步还原,曲率随之减小。同时还发现随着电化学反应的进行,由于放电产物多硫化物的溶解,正极附近的电解液呈黄色且不断加深。结合扫描电子显微镜(SEM)观察充放电前后的电极断面和表面的形貌,验证硫正极在充放电过程中出现明显的形变,从而导致电极曲率的变化。

An experimental set-up was developed which can observe electrode deformation and electrochemical reaction in-situ during the charge-discharge cycling of lithium-sulfur battery. The positive bending deformation during charge and discharge was monitored at real time. It was found that the positive curvature increased during discharge and reduced during open circuit. The curvature would recover the original state during charge period. As electrochemical reaction proceeds, the electrolyte near positive electrode gradually become yellow and deepened due to polysulfide dissolution of discharge products. Results of surface and section morphology observation on sulfur electrode before and after cycle using scanning electron microscope （SEM） were consistent with curvature changes during cycling and verified the volumetric expansion of sulfur electrode.