A Facile Chemical Reduction Approach of Li–Sn Modified Li Anode for Dendrite Suppression

Abstract

Lithium dendrites are among the most significant threats associated with the practical application of lithium metal anode in lithium batteries. Lithium dendrites are caused by the slow Li-ion diffusivity in the bulk lithium, which results in a non-uniform electric field-cum-uneven Li plating/stripping at the electrode/electrolyte interface over prolonged cycling. Herein, a facile chemical reduction method is utilized to construct a Li-ion diffusive Li–Sn protective layer on the electrolyte-exposed surface of lithium metal to overcome the aforementioned challenge. A systematic study on the SnCl₄ precursor concentration variation demonstrated that 25 mM SnCl₄ concentration is the most effective and displays a cumulative areal capacity beyond 700 mAh cm⁻² at 1 mA cm⁻² for 1 h. Moreover, it exhibits superior cumulative capacities than bare Li metal at higher current densities of 2 and 3 mA cm⁻². In situ optical microscopy reveals more uniform lithium deposition on the Li–Sn-modified electrode, while mossy and dendritic lithium growth is observed on the bare lithium electrode. Full cells fabricated with Li–Sn modified anode and NMC532 cathode exhibited 83% capacity retention after 150 cycles, outperforming bare Li-containing cells, which shows a catastrophic decay post 100 cycles, illustrating the propensity for safer Li metal batteries with Li–Sn modified anode.