High Areal Capacity and Lithium Utilization in Anodes Made of Covalently Connected Graphite Microtubes

Lithium metal is an attractive anode material for rechargeable batteries because of its high theoretical specific capacity of 3860 mA h g^-1 and the lowest negative electrochemical potential of -3.040 V versus standard hydrogen electrode. Despite extensive research efforts on tackling the safety concern raised by Li dendrites, inhibited Li dendrite growth is accompanied with decreased areal capacity and Li utilization, which are still lower than expectation for practical use. A scaffold made of covalently connected graphite microtubes is reported, which provides a firm and conductive framework with moderate specific surface area to accommodate Li metal for anodes of Li batteries. The anode presents an areal capacity of 10 mA h cm^-2 (practical gravimetric capacity of 913 mA h g^-1 ) at a current density of 10 mA cm^-2 , with Li utilization of 91%, Coulombic efficiencies of ≈97%, and long lifespan of up to 3000 h. The analysis of structure evolution during charge/discharge shows inhibited lithium dendrite growth and a reversible electrode volume change of ≈9%. It is suggested that an optimized microstructure with moderate electrode/electrolyte interface area is critical to accommodate volume change and inhibit the risks of irreversible Li consumption by side reactions and Li dendrite growth for high-performance Li-metal anodes.