Improving the cycling stability of lithium metal anodes using Cu3N-modified Cu foil as a current collector

Abstract

Lithium (Li) metal anodes have the potential to stimulate the development of secondary batteries due to their high theoretical specific capacities and low redox potentials among all possible solid secondary anode compounds. However, the growth of Li dendrites during repeated Li stripping/plating processes leads to low coulombic efficiencies (CEs) and safety hazards, which significantly hinders their practical application. In this work, commercial Cu foil was modified in situ by Cu3N nanowires (Cu3N NWs/Cu) and used as the current collector for a Li anode. In addition to decreasing the true current density of the anode and alleviating the volume change during the cycles, Cu3N reacted with Li during the initial cycle (3Li + Cu3N → Li3N + 3Cu), which enabled the formation of a Li3N-rich solid electrolyte interphase (SEI). This Li3N-rich SEI with a high ionic conductivity not only boosted Li ion transport but also promoted the homogeneous deposition of Li via increased Li nucleation sites. The improvements in both mass transport and deposition dynamics restrained dendrite growth. As a result, the Cu3N NWs/Cu anode had stable Li plating/stripping over 270 cycles with a high average CE of 98.6% at 1 mA cm−2, with Li capacities of 1 mA h cm−2. A long cycling lifespan of 430 cycles was achieved using a full cell with a high-load LiFePO4 cathode (mass loading: 10 mg cm−2) and a Cu3N NWs/Cu-Li anode (N/P = 2.35), demonstrating the effectiveness and practicality of the Cu3N NWs/Cu current collector in stabilizing the Li anode.