A Deep Eutectic Solvent Electrolyte Enables Planar Cu Deposition and High‐Temperature Cu–MnO2 Battery

Abstract Cu anodes exhibit a higher theoretical specific capacity (843 mAh g −1 or 7558 mAh cm −3 ) than Zn anodes (820 mAh g −1 or 5855 mAh cm −3 ), and have garnered widespread attention. However, aqueous Cu‐ion batteries suffer from severe Cu dendrite growth, limited cycle life, and poor high‐temperature performance. To the best of our knowledge, this is the first time that a deep eutectic solvent (DES) electrolyte is proposed to address these issues. Fourier transform infrared spectroscopy and molecular dynamics simulations confirm that the DES electrolyte coordinates with Cu 2+ , thereby modulating the Cu deposition behavior. Consequently, planar deposition and extended cycle life (6000 h versus 730 h) are achieved. Furthermore, the DES electrolyte exhibits the promising application potential under harsh conditions. A high‐temperature Cu─MnO 2 full cell retains a capacity of 174.8 mAh g −1 after 300 cycles at 2 A g −1 under 50 °C.