Robust lithium storage of block copolymer-templated mesoporous TiNb2O7 and TiNb2O7@C anodes evaluated in half-cell and full-battery configurations

Abstract

We report a facile Pluronic F127-mediated evaporation-induced self-assembly (EISA) process for the scalable preparation of mesoporous TiNb2O7 (m-TNO) with an uniform grain size of ~12 nm. The elaborated m-TNO are demonstrated as an excellent anode material for lithium-ion batteries (LIBs) able to deliver a high discharge specific capacity of 235.7 mAh/g at 1 C and 109.2 mAh/g even at 20 C, with high capacity retention rate up to 94.6% after 100 cycles at 1 C in half cell. In addition, the m-TNO electrode delivers a specific capacity of 257.1 mAh/g at a current density of 0.5 C in the m-TNO/LiFePO4 full cell, and a high discharge capacity of 185.1 mAh/g can be achieved with a capacity retention rate of 78.7% even at 1 C after 800 cycles. To further improve the electrochemical performances, carbon-coated m-TNO (m-TNO@C) is also synthesized by calcining the mixture of m-TNO and glucose. The initial discharge specific capacity of m-TNO@C is 248.4 mAh/g, and the capacity retention after 100 cycles at 1 C is 90.1%. The conductive carbon layer on m-TNO significantly improves the electronic conductivity of m-TNO. Cyclic voltammetry (CV) and electrical impedance spectroscopy (EIS) analyses show that coating the carbon layer by grinding will reduce the Li+ ion diffusion rate and lower its rate performance under the high current density, compared with the uncoated counterpart. Both of m-TNO and m-TNO@C deliver long-term cyclic stability with the large capacity of ~160 mAh/g even at 5 C after 800 cycle, accompanied by the capacity retention rate of ~70%, exhibiting excellent electrochemical performances in LIBs.