Unraveling the mechanism of non-uniform lithium deposition in liquid electrolytes
Dongdong Qiao, Xuezhe Wei, Jiangong Zhu, Xueyuan Wang, Bo Jiang, Wenjun Fan, Gang Wei, Guangshuai Han, Xin Lai, Yuejiu Zheng, Haifeng Dai
Abstract
Understanding the mechanism of non-uniform deposition of lithium and dendrite growth is necessary for battery degradation and safety performance improvement. Here, we design a symmetric cell sealed in a glass capillary to observe in situ the morphological changes during the lithium deposition process. Based on the in situ observation results and ex situ battery postmortem scanning electron microscopy (SEM) results, it is found that uneven lithium deposition inevitably occurs under long-term electrodeposition. In addition, lithium deposition under high current density is loose and porous, which is accompanied by the growth of needle-like lithium dendrites. This study reveals that the surface morphology of the anode and the electric field form a feedback mechanism: uneven morphology forms an uneven electric field, leading to a “tip effect” on the electrode surface, causing further uneven lithium deposition and lithium dendrite growth. • “Dead lithium” is discovered during the lithium plating process • Uneven lithium deposition occurs at different current densities • A positive feedback mechanism leading to uneven lithium deposition is revealed • Improving the surface quality of electrodes can suppress the growth of dendrites Qiao et al. examine the lithium plating process, providing insights into the formation of dead lithium. Furthermore, the positive feedback mechanism of crystal nucleus growth, uneven deposition, and dendritic growth of lithium is revealed by studying the interaction between electrode morphology and distribution of electric field lines.