Stabilizing a High-Energy-Density Rechargeable Sodium Battery with a Solid Electrolyte

The cycling performance at 60°C of a Na₂MnFe(CN)₆/Na cell with a ceramic solid electrolyte is compared with that of a cell with an organic-liquid electrolyte operating at room temperature. Analysis of the electrode-electrolyte interfaces after charge-discharge cycling showed that a sodium-metal anode that wets the solid electrolyte can be plated and stripped reversibly dendrite free and that the dissolution of the cyano-perovskite Na₂MnFe(CN)₆ cathode that occurs with an organic-liquid electrolyte is eliminated with the utilization of the solid electrolyte. This demonstration indicates that a high-energy-density and low-cost sodium rechargeable battery can be competitive for large-scale electric energy storage where both the anode and cathode problems are solved in an all-solid-state battery. The dependence of modern society on the combustion of fossil fuels is not sustainable. Solar and wind energy can be harvested and converted to electric power that can be transported to stationary sites for storage. Storage of electric power in a rechargeable battery would be the best solution, and a battery with a metallic-sodium anode and a cyano-perovskite Na₂MnFe(CN)₆ cathode would offer low-cost storage of electric power provided that its cycle life can be greatly improved. We demonstrate that this improvement is possible if a solid Na⁺ electrolyte can replace the organic-liquid electrolyte into which the Na₂MnFe(CN)₆ cathode dissolves over repeated charge-discharge cycling, and dendrite-free plating of a sodium-metal anode provides low impedance. Dissolution of the Na₂MnFe(CN)₆ cathode and the growth of sodium dendrites are eliminated in an all-solid-state sodium battery with a ceramic solid electrolyte contacting the sodium-metal anode and the Na₂MnFe(CN)₆ cathode.