Liquid metal alloys as self-healing negative electrodes for lithium ion batteries

Improving the capacity and durability of electrode materials is one of the critical challenges lithium-ion battery technology is facing presently. Several promising anode materials, such as Si, Ge, and Sn, have theoretical capacities several times larger than that of the commercially used graphite negative electrode. However, their applications are limited because of the short cycle life due to fracture caused by diffusion-induced stresses (DISs) and the large volume change during electrochemical cycling. Here we present a strategy to achieve high capacity and improved durability of electrode materials using low-melting point metallic alloys. With gallium as an example, we show that at a temperature above the melting point of Ga, a reversible solid-liquid transition occurs upon lithiation (lithium insertion) and delithiation (lithium extraction) of Ga. As a result, cracks formed in the lithiated solid state can be healed once the electrode returns to liquid Ga after delithiation. This work suggests that cracking as a failure mode can be remedied by using liquid metal electrodes.