Solvation-mediated electrostatic shielding of Li anodes by Na⁺ for durable lithium-oxygen batteries

Aprotic lithium-oxygen (Li-O₂) batteries represent a promising next-generation energy storage technology due to their high theoretical energy density. However, their practical application is severely hampered by lithium dendrite growth and anode failure. Here, we establish a solvation-mediated electrostatic-shielding strategy that enables uniform Li deposition through electrostatic shielding by Na⁺ at a high Na⁺/Li⁺ molar ratio. We found that solvation energy plays a decisive role in determining deposition potentials and thus achieved the use of high relative fraction of Na⁺ shielding ions to stabilize Li deposition by electrostatic shielding in a 1-n-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([Py₁₄][TFSI])-based electrolyte. Spectral and simulation results reveal an all-anion solvation sheath where TFSI^- coordinates both Li⁺ and Na⁺, narrowing their solvation energy gap and thermodynamically favoring Li⁺ deposition at high Na⁺ ratio. The optimized electrolyte (0.2 M LiTFSI/0.1 M NaTFSI in [Py₁₄][TFSI]) extends the cycle life of Li‖Li symmetric cells to over 1400 h at 0.2 mA cm^-2 and enables stable Li-O₂ battery operation for 124 cycles without capacity decay under 500 mA g^-1. This work highlights the critical role of solvation structure in regulating deposition behavior and provides an effective approach for durable Li-O₂ batteries.