Structural Vulnerability Control by Encapsulation Strategy toward Durable Lithium Metal Reference Electrodes

Abstract As an effective decoupling and quantification tool, reference electrodes (REs) are increasingly utilized in the development of high‐performance and high‐safety lithium (Li) batteries. However, it is still challenging to construct durable REs in practical battery systems given the sophistication of multi‐field interactions. In this contribution, the two‐stage failure mechanism of Li metal REs set inside working batteries is determined, including the active material loss period due to spatial redistribution behavior and then accelerated failure period based on mixed potential theory, which greatly threatens the dynamic service lifespan of REs. Furthermore, the targeted encapsulation strategy is proposed to control the structural vulnerability issue of Li metal REs. Compared to the unmodified RE, the encapsulated RE is validated feasible to kinetically mitigate the redistribution current through it via designed model experiments. Benefited from the improved structural stability, the encapsulated RE achieved twofold lifetime prolongation in 1 Ah pouch full cells during cycling. This work reveals the neglected structural failure mechanism of Li metal REs in operation and provides fresh design implications toward more durable REs in working batteries, with which deeper insights into battery landscape will be acquired.