Towards a Greener and Scalable Synthesis of Na2Ti6O13 Nanorods and Their Application as Anodes in Batteries for Grid-Level Energy Storage.

Grid applications require high power density (for frequency regulation, load leveling, and renewable energy integration), achievable by combining multiple batteries in a system without strict high capacity requirements. For these applications however, safety, cost efficiency, and the lifespan of electrode materials are crucial. Titanates, safe and longevous anode materials providing much lower energy density than graphite, are excellent candidates for this application. The innovative molten salt synthesis approach proposed in this work provides exceptionally pure Na2Ti6O13 nanorods generated at 900-1100 °C in a yield ≥80 wt%. It is fast, cost-efficient, and suitable for industrial upscaling. Electrochemical tests reveal stable performance providing capacities of ≈100 mA h g-1 (Li) and 40 mA h g-1 (Na). Increasing the synthesis temperature to 1100 °C leads to a capacity decrease, most likely resulting from 1) the morphology/volume change with the synthesis temperature and 2) distortion of the Na2Ti6O13 tunnel structure indicated by electron energy-loss and Raman spectroscopy. The suitability of pristine Na2Ti6O13 as the anode for grid-level energy storage systems has been proven a priori, without any performance-boosting treatment, indicating considerable application potential especially due to the high yield and low cost of the synthesis route.