Revealing the Intrinsic Uneven Electrochemical Reactions of Li Metal Anode in Ah-Level Laminated Pouch Cells

The uneven electrochemical reactions of lithium (Li) metal anode is one of the main reasons that hinder its application in rechargeable high energy density batteries. Great progress has been achieved in homogenizing electrochemical reactions of Li metal anode in lab-scale coin cells, however, it cannot be directly applied to pouch cells, where undesirable defects or side reactions are significantly aggravated. With carbonate electrolyte, multi-layered negative and positive electrodes (8 x 11 cm), 1.2 Ah sulfurized polyacrylonitrile (SPAN)||Li pouch cell lost all its capacity after 40 cycles under a current of 600 mA, although its counterpart with coin cell configuration showed much higher capacity retention of 94% under the same test condition. Severe corrosion with uneven, porous, dendritic Li deposits is observed for pristine Li electrode in a pouch cell, especially in the near-tap and the central regions with close connection with the current collector due to the locally amplified current densities. In contrast, Li/Li-Sn alloy composite electrode displays uniform and dense Li plating behavior over the entire test area with significantly suppressed parasitic reactions and gas evolution. As such, a 1.2 Ah SPAN||Li/Li-Sn cell displays much higher capacity retention than SPAN||Li cell (87% for 100 cycles vs. 0 for 40 cycles).