Non-Consumable Gamma-Cyclodextrin Additive Constricting Anti-Solvation Interphase Realizing Dendrites Free and High-Performance Lithium Metal Batteries

Abstract

Relying on surpassing high theoretical capacity (3,865 mAh g-1) and the lowest relative electrode potential (0 V vs. metallic Li), lithium metal batteries (LMBs) have been regarded as the "holy grail" of next-generation energy storage technology. Whereases, the instability of pristine solid electrolyte interphase (SEI) layers and the disorderly growth of lithium dendrites are still significant challenges to the commercialization of LMBs. In this study, a novel approach is introduced to homogenize Li deposition by incorporating an environmentally friendly electrolyte additive, gamma-cyclodextrin (γ-CD), in ether-based electrolytes. Through host-guest interactions, γ-CD additives not only form inclusion complexes to improve Li+ transference number to 0.864 but also encapsulate TFSI- anions and other solvent molecules within the “cavity effect” to relieve unfavorable solvent effect. Electrochemical characterizations demonstrate that introducing 1 wt % γ-CD elevates the oxidation decomposition voltage of ether electrolytes to 4.15 V, thereby inhibiting the decomposition of ether electrolytes and reducing the fracture of SEI layers. According to reduce the nucleate potential, the Li//Cu half battery exhibits improved stability for 100 cycles, with an improved average Coulombic efficiency (CE) maintained above 98.1%. Even if applied at high current densities of 5 mA cm-2 for a capacity of 1 mAh cm-2, the Li//Li symmetric battery can cycle for over 800 hours, and the Li//Li4Ti5O12 (LTO) full battery retains 98.8% of the initial capacity after 1400 cycles.

Keywords: Gamma-cyclodextrin, Li metal battery, Electrolyte additive, Li dendrites, Solid electrolyte interphase, Anti-solvent effect