Berkeley Lab researcher Marca Doeff and colleagues have developed a new electrode material based on a layered sodium titanate compound that can be used to form electrodes for large electric grid storage and other rechargeable battery systems.
The researchers found that anodes can be fashioned from a parent compound consisting of Ti6O14 units connected into a corrugated layered structure with hydrated Na cations and protons in the interlayer spaces. Performance is improved after water is irreversibly removed during high heat treatment, forming a compact, layered sodium titanate that can reversibly intercalate either sodium or lithium. This electrochemical process makes the material a suitable electrode material for either sodium or lithium batteries.
Lithium- or sodium-based storage systems have the theoretical energy capacity needed for efficient grid storage systems, but the electrode materials available to date are too costly and have a short cycle life. The Berkeley Lab layered sodium titanate electrodes are comprised of lower cost, Earth-abundant materials and can potentially result in a higher energy density and rate capability for devices than those that use carbonaceous materials as anodes. The new electrode materials using titanium-based oxides also have the potential to be more durable than alloy anodes based on silicon or tin that undergo substantial volume changes during the charge/discharge cycle. Large sodium batteries theoretically have the energy densities and economies required for electric grids responding to fluctuations inherent to wind or sun power. Because the Berkeley Lab sodium titanate electrodes also intercalate lithium, they could also be developed as lower cost electrodes for the high capacity lithium-ion batteries used in electric vehicles.