Modulating the electrical conductivity of a graphene oxide-coated 3D framework for guiding bottom-up lithium growth

Abstract

Realizing Li-metal batteries requires overcoming several hurdles, such as volume changes, a thickening solid electrolyte interphase, and safety issues associated with uncontrollable Li growth. Introducing a 3D conductive framework that improves Li reversibility by decreasing the local current density and alleviating volume changes can mitigate these issues, but inevitable Li growth on the top surface remains problematic. To address this, herein, we report an electrical conductivity-controlled 3D host consisting of a glass fiber (GF) framework, size-/conductivity-controlled partially reduced graphene oxide (PrGO), and a Cu substrate (PrGO–GF/Cu). Due to the synergistic interplay between the 3D GF alleviating volume fluctuation and PrGO with desirable conductivity, the PrGO–GF/Cu host mitigates the Li top plating and guides preferential Li deposition/dissolution at the bottom of the structure. As a result, the PrGO–GF/Cu exhibits substantially improved electrochemical performance in coulombic efficiency, symmetric cell, and LiFePO4 full cell tests. Experimental and theoretical studies reveal that modulating the electrical conductivity of the framework within an optimal range is an easy and effective way of suppressing Li top plating and facilitating Li bottom plating/stripping. This work demonstrates the importance of controlling the electrical conductivity to enable reversible behavior of Li in the Li-metal host anode, and a facile method to fabricate a 3D host that prevents Li top plating.