Facile fabrication of a high performance TiNb2O7 anode for large-scale electrical energy storage

The titanium niobium oxide (TiNb2O7) material is synthesized by a facile two-step solid-state calcination (denoted as 2ndTNO). The 2ndTNO delivers a high reversible discharge capacity of 288 mA h g(-1) at 0.1C, good rate performances at 1C-5C, and an excellent capacity retention of 85.4% after 500 cycles at 1C/1C (with a discharge capacity of 195.5 mA h g(-1) after 500 cycles). Large-size 40 Ah LFP/TNO pouch type batteries are also assembled and exhibit excellent cycling stabilities. The enhancement in electrochemical properties of 2ndTNO is mainly attributed to the generation of oxygen vacancies during the second calcination, which increases the electronic conductivity via charge redistribution and atom reduction to lower valence states (Nb4+ and Ti3+). The two-step calcination is a promising method for mass production of high-performance oxide electrode materials.