Tailored charging protocol for densified lithium deposition and stable initially anode-free lithium metal pouch cells

The low mechanical strength and insufficient lithium-ion conductivity of solid-electrolyte interphase will incur inhomogeneous lithium deposition and eventually cause battery failure, hindering practical application of lithium metal batteries. Combining multiple characterization techniques and COMSOL simulation, here we report that the commonly-adopted constant current charge protocol would result in formation of highly porous lithium metal negative electrode, leading to severe parasitic reactions. To ameliorate this problem, we propose a middle peak current charge protocol with a peak current in the middle of charging step, which could guide the nucleation and growth of densified lithium deposition with the derived solid-electrolyte interphase possessing significantly improved mechanical strength and Li+ ion conductivity. Therefore, coin-type initially anode-free lithium metal batteries could be stably cycled for 80 cycles (with 3 hours of charging and state-of-charge of ~70%). A 1.5 Ah initially anode-free Li metal pouch cell which delivers a specific energy of 400 Wh kg-1 at 225 mA and with a capacity retention of 80% for 298 cycles (with 3 hours of charging and state-of-charge of 80%) is also demonstrated. The low mechanical strength and insufficient lithium-ion conductivity of the solid-electrolyte interphase result in inhomogeneous lithium deposition. Here, the authors propose a new middle peak current charging protocol, guiding the nucleation and growth of densified lithium deposition and a solid-electrolyte interphase with improved mechanical strength and Li+ ion conductivity.