Redistributing Li-ion flux and homogenizing Li-metal growth by N-doped hierarchically porous membranes for dendrite-free Lithium metal batteries

Abstract

Safety hazards caused by lithium dendrites significantly impedes the practical applications of Li metal batteries. However, the previously reported materials with low porosity can be easily filled up by the deposition of Li and loss of regulating effect for lithium dendrites as a Li metal protecting interlayer. Herein, scalable N-doped hierarchically porous membranes (NHPM) with significant porosity of about 90% are reported. The interconnecting porous networks with carbon nanotubes (CNTs) as the cores and N-doped carbon coating as the crosslinked shells allow the uniform distribution of Li+ ions. It also facilitates the rapid diffusion of Li ions and promotes the reversible Li plating and stripping processes. The first-principle calculations reveal that the N active sites that promote Li adsorption can greatly reduce the energy barrier for Li-ion transfer and diffusion on the carbon-coated surface. The protected Li anode exhibits a high Coulombic efficiency of ~99% and presents dendrite free morphology even when repeated Li plating/stripping processes are conducted over 500 h under condition of high current density (8 mA cm−2). A full cell battery with LiFePO4 as the cathode and protected Li as the anode exhibits high cycling stability (up to 600 cycles). The capacity decay rate is as low as 0.03% per cycle.