Mechanism of lithium electrodeposition in a magnetic field

Lithium metal anode is a promising anode for next-generation lithium-based batteries. However, the lithium dendrite growth due to uneven Li-ion deposition could cause safety problem, and the unceasing formation of solid electrolyte interphase layer leads to capacity fading of anode. Here, we report a mechanism of Li electrodeposition under a magnetic field with the direction perpendicular or parallel to electric field in the cell systematically. We for the first time observe that at the initial nuclei stage the deposited Li metal is needlelike; for the later growth stage, a very compact deposits with dendrite-free structure can be obtained. Compared with perpendicular magnetic field, the parallel one can facilitate more uniform and dense lithium growth. The Lorentz force and the electric field force during Li platting are calculated and compared. It also indicates that the magnetic field can contribute to a smooth Li deposits after cycling at various current densities and deposited capacities. The polarization of the Li symmetrical cells is reduced in the magnetic field resulting in more stable cycling performance. In addition, improved electrochemical performance of the Li|LiCoO2 half cells can be achieved by applying a magnetic field. The study demonstrates that the electromagnetic environment is critical to stabilizing Li-metal anode in high-energy-rechargeable batteries.