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Effects of pH on Preparation and Properties of CaTi2O4(OH)2 by Hydrothermal Method

A novel CaTi2O4(OH)2 nanosheet was synthesized using anhydrous calcium chloride, lithium chloride and butyl titanate as the basic raw material by a template-free and surfactant-free hydrothermal method. The crystal structure, morphology and element synthesis were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) equipped with an EDS system. Effects of pH on the structure, morphology and electrochemical properties were investigated. The results showed that when pH was 6.7, CaTi2O5 phase was obtained. When pH was 8.3, pure CaTi2O4(OH)2 nanosheets were obtained. Further increasing pH to 8.6, CaTi2O4(OH)2 was obtained, however, and CaTiO3 phase also appeared. When pH was 8.3, the rate capacity of CaTi2O4(OH)2 nanosheets was further higher than those of the samples prepared for pH=6.7 and pH=8.6. It indicated that CaTi2O4(OH)2 nanosheets were helpful for lithium insertion and de-intercalation. The sample synthesized at pH=8.3 showed the best electrochemical performances, with first discharge specific capacity of 177.9 mAh/g at 0.1C rate. The CaTi2O4(OH)2 nanosheets might represent an opportunity for the applications in lithium ion battery.