Li dendrite suppression enables a highly reversible Li-metal battery. However the strategy to smooth Li surface, especially under long-term cycling and high current density, is still a big challenge. Here, we propose a facile additive strategy to reinforce Li dendrite inhibition in a range of ether and carbonate electrolytes. Dissoluble Mg(TFSI)2 is employed as a degradable electrolyte additive, leading to in situ plating of porous Mg network when contacting reductive Li atoms. Mg adatoms with extremely low diffusion energy barrier as lithiophilic sites enable a smooth or flaky morphology of Li surface even under a high current density of 2 mA/cm2 and high capacity of 6 mAh/cm2. Mg-salt additive significantly extends the cycling life of Li||Cu asymmetric cells up to 240 and 200 cycles for carbonate and ether electrolytes, respectively. Under a current density as high as 5 mA/cm2, the Li||Cu cell based on ether system can still survive up to 140 cycles with a small voltage hysteresis close to 60 mV. The hysteresis can be reduced to below 25 mV for lasting 200 cycles at 1 mA/cm2. This additive strategy provides a facile solution to in situ construction of conductive anode-electrolyte interface with low interface resistance for alleviating uneven Li nucleation.
Keywords: Li-metal batteries; Mg(TFSI)2; anode modification; dendrite suppression; electrolyte additive.