Lawrence Berkeley National Laboratory

Highlights: Further performance improvements of sodium-ion batteries require better-performing electrode materials, particularly anodes. The layered lepidocrocite-type sodium titanate (Na0.74Ti1.815□0.185O4·1.27H2O), showing a high Na+ storage capacity of 229 mAh g−1 at relatively low average voltage of ca. 0.6 V vs. Na+/Na, is a promising candidate anode material. Abstract: A lepidocrocite-structured sodium titanate prepared by ion-exchange of a Cs-containing precursor shows promise as an anode material for sodium ion batteries, with a discharge capacity of up to 229 mAh g−1 at an average potential of about 0.6 V vs. Na+/Na. Titanium vacancies in the metal oxide layers provide additional sites for sodium intercalation in addition to interlayer sites, which accounts for the higher capacity compared to other previously reported lepidocrocite-structured titanates. By screening a series of electrolyte formulations and binders, we were able to improve the first-cycle coulombic efficiency to 81.8% and 94.7% respectively using CMC/SBR-based and binder-free electrodes in ether electrolytes. The electrochemical consequences of short-term air-exposure on the electrodes are also discussed. Graphic abstract: [Figure not available: see fulltext.]