A salt-free aqueous battery system: Insights into proton dynamics and electrochemical mechanisms

초록

In this study, we developed a novel aqueous secondary battery system that utilizes a salt-free electrolyte composed solely of water, eliminating the need for conventional salts. Using copper hexacyanoferrate (CuHCF) as the electrode material, we conducted electrochemical tests that confirmed the effective operation of the battery, demonstrating typical charge/discharge behavior in the salt-free electrolyte. Solid-state nuclear magnetic resonance revealed changes in 1H chemical shifts during the charge/discharge processes, providing evidence of proton insertion and deinsertion within the CuHCF structure. These findings were further supported by cyclic voltammetry and X-ray photoelectron spectroscopy, which elucidated the role of protons in the electrolytes of electrochemical redox reactions. The protons generated by the self-ionization of water appeared to serve as charge carriers, enabling efficient battery operation without adding salt. The salt-free electrolyte system may offer significant cost advantages and potential environmental benefits, suggesting its potential as a next- generation energy storage solution.

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