Electrolyte-concentration dependent formation of artificial interface for prolonging the cycle life of Li-based anion storage batteries

The cycle life of anion-storing carbon cathodes suffers from parasitic side reactions on the electrode surface during high-voltage cycling. As a precautionary measure, the surface is protected by the artificial interface formed via electrochemical techniques using different concentrations of electrolytes. The chemical nature of the interfaces varies depending on the concentration of electrolyte, so the electrochemical performances. The interface formed in 0.3 M electrolyte is driven by the electrolyte solvent, rich in organic components (carbonates and phosphates), and undergoes dynamic changes during cycling, thereby yielding poor electrochemical performance. The percentages of inorganic components increase slightly in 1 M electrolyte and the cycling efficiencies improve to some extent. In contrast, the interface of 3 M electrolyte is dominated by the electrolyte salt (LiPF6)-derived inorganic products (LixPOy, POxFy, and CFx) and endows high-voltage protection to the greatest extent. The mechanochemically robust layer enhances interfacial stability, reduces side reactions, minimizes the growth of resistance, and safeguards the bulk of the material from premature failure. The modified electrode in 3 M electrolyte retains 85 % capacity after 500 cycles, while the unmodified electrode fails drastically within 50 cycles. The approach is equally applicable to LiNi0.5Mn1.5O4 cathode that stores Li+ at high voltage.