Encapsulating Metallic Lithium into Carbon Nanocages Which Enables a Low-Volume Effect and a Dendrite-Free Lithium Metal Anode.

Abstract

Metallic lithium (Li), with its high capacity and low redox potential, shows significant development potential for high-energy-density Li batteries. Unfortunately, huge volumetric changes, uncontrollable Li dendrites, and interfacial parasitic reactions limit its commercial application. Herein, we demonstrate a rational strategy of encapsulating metallic Li into the interior spaces of hollow carbon (C) nanocages for dendrite-free Li metal anodes. We find that the poly(vinylidene difluoride)-binder-modified thin-layer C walls on the C nanocages can guide Li deposition into the interior spaces of these hollow C nanocages and simultaneously reduce the interfacial parasitic reactions between deposited Li metal and an electrolyte. In addition, because of the high specific surface area and huge interior spaces of the C nanocages, the local current density can be reduced and large volume changes are mitigated. Specifically, this electrode exhibits negligible volume changes at 1.0 mAh/cm2 and a 14.9% volume change at 3.0 mAh/cm2. The copper (Cu) foil electrode exhibits 87.9% and 234.3% volume changes at the corresponding deposition capacities. Consequently, a C-nanocage-modified electrode exhibits an outstanding Coulombic efficiency of 99.7% for nearly 150 cycles at a current density of 1.0 mA/cm2, while a Cu foil electrode exhibits less than a 70.0% Coulombic efficiency after only 43 cycles. When paired with a sulfur cathode, the C-nanocage-modified electrode exhibits better cycling and rate performances than the pristine Cu foil electrode.