Thermally reduced graphene paper with fast Li ion diffusion for stable Li metal anode

The increasing demand for high-specific-energy batteries drives researchers to revisit Li metal anode. However, the formation and growth of Li-dendrite possibly leads to short-circuit of the battery, causing safety hazard of Li metal batteries. Therefore, it is quite necessary to regulate the plating/stripping behaviors of Li metal anodes to address this long-standing issue. Herein, we report the regulation of Li plating/striping behavior via manipulating the ratio of oxygen containing groups on reduced graphene oxide papers. It has been revealed that the electrochemical properties are highly dependent on the amount of carbonyl C[dbnd]O groups, which could associate Li⁺ and serve as a uniform nucleation site to guide Li plating. Furthermore, a high lithium ion diffusion coefficient of ∼2.09 × 10⁻¹⁴ m² s⁻¹ was enabled, around one magnitude higher than that of the Li lattice self-diffusivity (∼2 × 10⁻¹⁵ m² s⁻¹). As a result, stable dendrite-free Li metal anode is realized on the reduced graphene oxide paper with high C[dbnd]O group content (8.4%), which exhibits a low and stable overpotential of 50 mV for a long lifetime of 400 h. Our studies provide a fresh insight into the Li ion diffusion and its critical role in the regulation of the Li plating/stripping behaviors.