A Low-Fermi-Level Current Collector Enables Anode-Free Lithium Metal Batteries with Long Cycle Life

Anode-free Li-metal batteries (LMBs) (i.e., assembled directly with current collector) hold great prospect for boosting energy density, but they suffer from very poor cycle life due to rapid consumption of limited Li source and electrolyte. In this work, a Zn-N-CNF current collector with a low-Fermi-level was designed to enable long cycling anode-free LMBs, where 1) the electron transfer between the electrolyte and low-Fermi-level current collector is restricted to controls the over decomposition of the electrolyte; 2) its strong affinity to the TFSI− anion leads to the preferential reduction of the TFSI− anion, forming a thin and conductive inorganic-rich solid electrolyte interphase (SEI), 3) the electronic structure of the Zn-Nx surface disfavors the clustering of Li-adatoms that leads to the planar growth of Li, resulting in a dense and smooth Li deposition morphology. Hence, this Zn-N-CNF current collector demonstrates highly reversible Li plating/stripping over 6000 h at practically high current densities of 5 mA/cm2. Remarkably, the anode-free LMB assembled with a Zn-N-CNF current collector exhibits a high capacity retention of 91% after 120 cycles, which is the best cycling performance reported to date for LMBs with zero excess Li.