Optimizing the cycling life and high-rate performance of Li 2 ZnTi 3 O 8 by forming thin uniform carbon coating derived from citric acid

The low electronic conductivity and moderate lithium-ion transfer capability of Li 2 ZnTi 3 O 8 restrict its application to some degree. In this work, in light of the high affinity of TiO 2 surface with carboxylic acids, citric acid was adopted as a carbon source to form uniform carbon coating layer on LZTO particles. When the mixture of LZTO and citric acid with a mass ratio of 1:0.2 was roasted at 700 °C for 5 h, the product demonstrated wonderful rate performance (revealing capacities of 232.6, 202.8, 184.8, 165.6 and 106.7 mAh g −1 at 0.1, 0.2, 0.4, 0.8 and 1.6 A g −1 , respectively) as well as outstanding long-term cycling stability (maintaining a capacity of 186.9 mAh g −1 for 1000 cycles at 0.5 A g −1 ). Combining structure and composition characterizations with electrochemical impedance spectra analysis, the amorphous carbon derived from citric acid was uniformly coated on the LZTO particles by virtue of the intense interaction between LZTO and carboxyl groups. Better particle dispersion and enhanced pseudocapacitive contribution were obtained resulted from the carbon coating, remarkably ameliorating the electronic and ionic conductivities of LZTO and alleviating polarization, thus beneficial to optimizing the electrochemical behavior of LZTO. Graphic abstract