Expanded-graphite embedded in lithium metal as dendrite-free anode of lithium metal batteries

Abstract

Lithium (Li) metal batteries present huge challenges in their practical application, including dendrite growth and infinite volume changes of the Li metal anode during cycling. Lightweight and porous carbon materials can effectively accommodate Li metal and suppress Li dendrite growth. Herein, we report a composite anode prepared by pressing the mixture of expanded-graphite (EG) with Li powder, followed by heating at 200 °C (Li–EG). The porous and well-conducting EG was uniformly embedded in Li metal, which provided sufficient surface and space for accommodating and attracting the Li metal. The in situ lithiation reaction between EG and Li metal formed LiC₆ that exhibited excellent lithiophilicity and ionic conductivity, which provided abundant nucleation sites and reduced the Li nucleation barrier as well as the overpotential, thereby effectively inhibiting the nucleation and growth of Li dendrites. In addition, the EG embedded in Li metal composite anode presented preferable thermal stability. Consequently, the EG/Li half-cell exhibited a life span of 1000 h at a current density of 1 mA cm⁻² and could be stably cycled for 1500 cycles at an ultra-high current of 10 mA cm⁻². As a result, the LiFePO₄‖Li–EG full-cell presented capacity retention as high as 93.5% after 500 cycles. The facile preparation method and excellent electrochemical performance render the composite anode a promising option in the practical use of Li metal batteries.