Controlled Lithium Dendrite Growth by a Synergistic Effect of Multilayered Graphene Coating and an Electrolyte Additive

Lithium (Li) metal is the most ideal anode material in lithium ion batteries due to its large theoretical capacity (3860 mAh g^-1) and low redox potential (-3.04 V vs standard hydrogen potential, H₂/H⁺). Nevertheless, surface dendrite formation during repeated charge-discharge cycles limits the cycle life and thus its practical use. The research efforts engaging polymer/ceramic coating or electrolyte additives have made noticeable progress, but further improvement is still desirable. Here, we report significantly improved performance by a synergistic effect of multilayered graphene (MLG) coating and Cs⁺ additive in the electrolyte. MLG separates solid-electrolyte-interphase (SEI) formation from Li dendrites and thus stabilizes Coulombic efficiency in each cycle. Cs ions facilitate efficient interlayer diffusion of Li ions by enlarging the interlayer distance of MLG and also assists further for suppression of Li dendrite growth by electrostatic repulsion against Li ions. When paired with a stable sulfur-carbon composite electrode as a high capacity cathode, the Li-sulfur cell delivers an areal capacity of 4.0 mAh cm^-2, a value comparable to those of current commercial lithium ion batteries, with 81.0% capacity retention after 200 cycles.