PNNL

Abstract

Externally applied pressure impacts the performances of batteries especially for those undergo large volume changes such as lithium metal batteries. Notably, eletroplating process of Li+ in the realistic pouch cells happens on a considerably enlarged dimension compared to those occur in lab-scale small cells. A fundamental linkage between external pressure and large-scale electroplating of Li+ is still lacking but urgently needed to understand the electrochemical behaviors of Li+ in realistic batteries. Herein, this work utilizes 350 Wh/kg lithium metal pouch cell as a model system to study the electroplating of Li+ ions impacted by the external pressure. The vertically applied pressure on the liquid batteries profoundly affects the electroplating process of Li+ which is well reflected by the self-generated pressures in the cell and correlated to battery cycling stability. Taking advantage of both constant gap and pressure, all Li metal pouch cells have demonstrated minimum swelling of 6-8% after ca. 300 cycles, comparable to that of Li-ion batteries. Along the horizontal directions, the pressure distributed across the surface of Li metal pouch cell reveals a unique phenomenon of Li+ detour during electroplating (charge) process driven by the uneven distribution of external pressure across the large electrode area, leading to the preferred Li plating in the center area of Li metal anode. This work provides fundamentally new insights on large-scale electrochemical plating of Li which will inspire more innovations to realize homogeneous deposition of Li to advance rechargeable lithium metal battery technology.