A 110 Wh kg−1 Ah-level anode-free sodium battery at −40°C

Summary

High-energy cryogenic batteries have been pursued throughout the past decades. Anode-free batteries offer a promising avenue to boost energy density because they comprise weightless anodes. However, their low-temperature operation is challenged by poor metal plating/stripping reversibility and unstable solid electrolyte interphase (SEI). Herein, the first low-temperature anode-free sodium battery is fabricated by simultaneous surface modification of the current collector and electrolyte design. The plasma-treated current collector (p-Al@C) possesses a sodiophilic N-doped carbon surface, enabling uniform sodium nucleation and growth; meanwhile, the optimized weak-solvation electrolyte facilitates Na⁺ desolvation and the formation of a B/F inorganic-contained SEI. Na||p-Al@C half cells exhibit an ultrahigh average Coulombic efficiency of 99.88%, and p-Al@C||Na₃V₂(PO₄)₃ batteries achieve an energy density of 250 Wh kg⁻¹_{cathode + anode} at −40°C. More interestingly, Ah-level anode-free pouch cells deliver a remarkable energy density of 110 Wh kg⁻¹_{entire cell} at −40°C. This work represents a critical step for low-temperature sodium batteries.