Method for Benchmarking Li Metal Anodes: A Mandatory Step toward Reliable Lithium Metal Batteries

All-solid-state batteries are known to be the new energy storage holy grail that will lead to safer batteries with higher energy density than current Li-ion batteries. The use of a solid electrolyte enables the use of lithium metal as the anode material. However, its composition, its thickness, and the quality/nature of its passivation layer can strongly affect the performance of the battery. For this reason, we propose a simple benchmarking method that evaluates and compares the quality and electrochemical performance of various Li anodes. This method can be easily reproduced, especially concerning the electrochemical evaluation that uses a commercial liquid electrolyte and the widely spread coin-cell format. In total, ~285 coin cells were assembled to benchmark our in-house lithium metal foil (Lithium HQ) with two commercial ones and the results showed the superior performance of our Li metal anode. The performance of the cells seems closely related to the quality and uniformity of the Li surface. In addition, we propose including in the benchmarking method the effect of Li aging in a dry room on the electrochemical performance. This effect is important to consider because the fabrication of all-solid-state batteries is conducted in such an environment.