Nitrogen-sodium co-doping improves cycle performance of lithium titanate anode materials at high rate

Abstract

Li4Ti5O12 is a lithium-ion battery cathode material with great potential for development because of its “zero-strain” characteristics, but its low lithium ion diffusion and conductivity rate lead to poor rate and cycling performance. NaN-LTO, a nanorod-like material with oxygen vacancies on the surface, was prepared by calcination after hydrothermal reaction using sodium molybdate as the sodium source and L-cysteine as the nitrogen source and structural guiding agen, while achieving co-doping of N and Na at the O and Li positions in situ respectively. The effects of N and Na co-doping on the crystal and electronic structures were revealed. The electrochemical test results show that rate and cycle performance of NaN-LTO are greatly improved, which can reach 126.0 mAh/g at 20C (1C = 175 mAh/g), 126.9 mAh/g after 1000 cycles with a capacity retention rate of 100.7% and the capacity retention rate is 74.0% after 3000 cycles. The co-doping strategy of Li-site and O-site provides a new modification idea to enhance the electrochemical performance of lithium titanate. Meanwhile, the preparation cost of lithium titanate can be reduced by the partial replacement of Li by inexpensive Na.