Exploiting self-heat in a lithium metal battery for dendrite healing

Over the past few decades, lithium ion batteries (LIBs) have dominated the rechargeable battery landscape. These LIBs are based on the rocking chair concept, where Lithium (Li) - ions shuttle between electrodes that behave as hosts for the ions during charge and discharge. Lithium metal, with a theoretical specific capacity of 3860 mAh g−1 is the ideal choice for the anode in a Li battery. However, the utilization of Li metal as the anode has been plagued by the inevitable formation of dendrites on electrochemical cycling (i.e., plating/stripping of Li). These dendrites are associated with a number of problems including irreversible capacity loss, reduced columbic efficiency, drying and degradation of the electrolyte as well as electrical shorting and thermal runaway of the battery. Here, we show that Li dendrites can be healed in situ in a Li-metal battery with a lithium iron phosphate based cathode and a Li metal anode. The healing is triggered by current-controlled, self-heating of the battery, which causes migration of surface atoms away from the dendrite tips, thereby smoothening the dendritic surface. Computational thermal modelling in conjunction with first principles density functional theory calculations are used in this study to understand the diffusion characteristics of Li atoms on the dendrite surface. Such in situ healing of Li dendrites could eliminate the risk of short circuiting and enable the safe deployment of Li-metal batteries for the next generation of high performance energy storage devices.