Proton-Induced Dysfunction Mechanism of Cathodes in an Aqueous Lithium Ion Battery

The proton-induced dysfunction mechanism of cathodes in aqueous lithium ion batteries is investigated by combining both experimental and theoretical research. We have found the electrochemical stability of the cathodes in a Li+-containing aqueous electrolyte solution is critically dependent on the pH value of the solution. The cyclic voltammograms of the cathodes show that the cathodes become dysfunctional when the pH of the solution decreases right below a certain value. We find that the competition reactions to the cathodes of the H+ and Li+ in the solution dominate whether Li+ or H+ would be intercalated. Thermodynamic analysis proves that the critical pH, which divide the normal and dysfunctional behaviors, is determined by both the difference of the binding energies of Li+ and H+ cations to the cathodes and the chemical potentials of the Li+ and H+ in the solution.