Oxygen Vacancy Modulated TiP <sub>2</sub> O <sub>7‐y</sub> with Enhanced High‐rate Capabilities and Long‐term Cyclability used as Anode Material for Lithium‐ion Batteries
Ning Zhang, Yanjun Cai, Xiang Yao, Hualing Tian, Zhi Su
Abstract
Abstract Oxygen‐deficient TiP 2 O 7‐y is synthesized by solvothermal and high‐temperature solid‐phase methods. X‐ray powder diffraction (XRD) test data analyses reveal that the solvothermal reaction time can affect the density of oxygen defects in the TiP 2 O 7‐y . Fourier transform infrared spectra (FT‐IR) shows that there is a blue shift in the P−O bond because of the presence of oxygen vacancies. It is strongly demonstrated that oxygen vacancies exist in TiP 2 O 7‐y because electron paramagnetic resonance (EPR) shows sharp peaks at g=2.003. Oxygen vacancy modulated TiP 2 O 7‐y with exposed (541) face shows long cycling stability and super high‐rate capabilities. The initial discharge capacity of TiP 2 O 7‐y , which was prepared after solvothermal reaction for 18 h, reached 828.4 mAh g −1 . It can still maintain 246.9 mAh g −1 , at 0.5 A g −1 , after 500 cycles. Even cycled at 5 A g −1 , the reversible rate capacity was maintained at 209.7 mAh g −1 . Oxygen vacancies can not only improve the electronic conductivity of TiP 2 O 7‐y but also increase the lithium‐ion diffusion rate.