Search for: All records

Abstract The electrochemical stability window of water is known to vary with the type and concentration of dissolved salts. However, the underlying influence of ions on the thermodynamic stability of aqueous solutions has not been fully understood. Here, we investigated the electrolytic behaviors of aqueous electrolytes as a function of different ions. Our findings indicate that ions with high ionic potentials, i.e., charge density, promote the formation of their respective hydration structures, enhancing electrolytic reactions via an inductive effect, particularly for small cations. Conversely, ions with lower ionic potentials increase the proportion of free water molecules—those not engaged in hydration shells or hydrogen‐bonding networks—leading to greater electrolytic stability. Furthermore, we observe that the chemical environment created by bulky ions with lower ionic potentials impedes electrolytic reactions by frustrating the solvation of protons and hydroxide ions, the products of oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. We found that the solvation of protons plays a more substantial role than that of hydroxide, which explains a greater shift for OER than for HER, a puzzle that cannot be rationalized by the notion of varying O−H bond strengths of water. These insights will help the design of aqueous systems. 

Abstract Li₂MnO₃has been contemplated as a high‐capacity cathode candidate for Li‐ion batteries; however, it evolves oxygen during battery charging under ambient conditions, which hinders a reversible reaction. However, it is unclear if this irreversible process still holds under subambient conditions. Here, the low‐temperature electrochemical properties of Li₂MnO₃in an aqueous LiCl electrolyte are evaluated and a reversible discharge capacity of 302 mAh g⁻¹at a potential of 1.0 V versus Ag/AgCl at −78 °C with good rate capability and stable cycling performance, in sharp contrast to the findings in a typical Li₂MnO₃cell cycled at room temperature, is observed. However, the results reveal that the capacity does not originate from the reversible oxygen oxidation in Li₂MnO₃but the reversible Cl₂(l)/Cl⁻(aq.) redox from the electrolyte. The results demonstrate the good catalytic properties of Li₂MnO₃to promote the Cl₂/Cl⁻redox at low temperatures. 

There is a growing interest in anionic redox chemistry to improve the energy densities of rechargeable batteries, and the reversible chlorine/chloride reactions are a promising option for low-temperature applications. As such, understanding Cl adsorption on the cathode surfaces is important in revealing the intimate connection between catalysis and charge storage via the reversible surface Cl2/Cl− redox chemistry. In this work, we investigate the adsorption of Cl on various SrBO3 perovskites, with B being 3d transition metals, by using density functional theory calculations and interpretable machine learning. We identify the electronic structure descriptors crucial for Cl adsorption. Our findings reveal that SrCoO3 exhibits optimal Cl adsorption at the top of the volcano curve for Cl2 evolution, suggesting its potential as a catalyst to enable a low-temperature, liquid Cl2 electrode. 

In the Mn₃O₄electrode, chloride ions are reversibly converted into atomic chlorine species. Trapped Zn²⁺cations aid in stabilizing these chlorine atoms in polychloride species.