An Interphase-enhanced Liquid Na-K Anode for Dendrite-free Alkali Metal Batteries Enabled by SiCl₄ Electrolyte Additive

Thanks to the high theoretical capacity and low redox potential, alkali metals (Li, Na, K) show great superiority as anodes for high-energy-density rechargeable batteries. However, practical application of alkali metal battery (AMB) is limited due to its formidable dendrite growth. Liquid Na-K alloy is a promising choice to fulfill long-term cyclability of AMB due to its liquid characteristics. Nevertheless, the instability of electrolyte/liquid Na-K interface is still a challenge for the dendrite-free deposition/stripping. In this work, a stable organic/inorganic hybrid interface beneficial to improving the charge-transfer kinetics is formed on the liquid alloy with the assistance of SiCl₄ electrolyte additive. The symmetric cell using interface-modified Na-K alloy electrode maintains an overpotential below 200 mV over 2000 h at 1mA cm⁻² with 1mAh cm⁻² for each cycle. The Na₃V₂(PO₄)₃ cathode coupled with interface-modified Na-K alloy shows a capacity of 91.5 mAh g⁻¹ at 30 C, and remains 103.6 mAhg⁻¹ after 1000 cycles at 2 C with nearly no capacity loss per-cycle. This work presents a facile approach for developing dendrite-free liquid alloy anodes and possesses potential application in liquid metal (LM)-related battery system with high energy density.