Low‐strain TiP₂O₇ with three‐dimensional ion channels as long‐life and high‐rate anode material for Mg‐ion batteries

Abstract

Abstract Rechargeable magnesium batteries are identified as a promising next‐generation energy storage system, but their development is hindered by the anode−electrolyte−cathode incompatibilities and passivation of magnesium metal anode. To avoid or alleviate these problems, the exploitation of alternative anode materials is a promising choice. Herein, we present titanium pyrophosphate (TiP 2 O 7 ) as anode materials for magnesium‐ion batteries (MIBs) and investigate the effect of the crystal phase on its magnesium storage performance. Compared with the metastable layered TiP 2 O 7 , the thermodynamically stable cubic TiP 2 O 7 displays a better rate capability of 72 mAh g −1 at 5000 mA g −1 . Moreover, cubic TiP 2 O 7 exhibits excellent cycling stability with the capacity of 60 mAh g −1 after 5000 cycles at 1000 mA g −1 , which are better than previously reported Ti‐based anode materials for MIBs. In situ X‐ray diffraction technology confirms the single‐phase magnesium‐ion intercalation/deintercalation reaction mechanism of cubic TiP 2 O 7 with a low volume change of 3.2%. In addition, the density functional theory calculation results demonstrate that three‐dimensional magnesium‐ion diffusion can be allowed in cubic TiP 2 O 7 with a low migration energy barrier of 0.62 eV. Our work demonstrates the promise of TiP 2 O 7 as high‐rate and long‐life anode materials for MIBs and may pave the way for further development of MIBs.