β-cyclodextrin as Lithium-ion Diffusion Channel with Enhanced Kinetics for Stable Silicon Anode

Silicon (Si) is regarded as a promising anode material for next-generation lithium-ion batteries due to its ultrahigh theoretical capacity. However, the drastic volume change and the continuous solid electrolyte interphase (SEI) formation during the lithiation/delithiation process seriously hinder its practical application as commercial anodes. Herein, macrocyclic beta-cyclodextrin (β-CD) has been designed as the diffusion channel for lithium ions at the molecular scale. The diameter of molecular channel is approximately comparable with the solvated lithium ions, which enables the transport of lithium ions and prevents the penetration of solvent molecules. Moreover, the addition of β-CD changes the formation behavior of SEI layer and stabilizes the Si nanoparticles. The enhanced electrochemical performances in terms of fast kinetics and improved stability have been achieved. The Si anode with the particularly selected lithium-ion diffusion channel and stabilized SEI layer exhibits a high reversible capability of 2 562 mAh g⁻¹ after 50 cycles at the current density of 500 mA g⁻¹, 1 944 mAh g⁻¹ after 200 cycles at the current density of 1 A g⁻¹, and high rate performance. The novel strategy of molecular channel for lithium-ion diffusion offers new insights into the design of alloy-typed anode electrodes with high capacity for lithium-ion batteries.