Electron-Extraction Engineering Induced 1T''-1T' Phase Transition of Re 0.75 V 0.25 Se 2 for Ultrafast Sodium Ion Storage.

Inducing new phases of transition metal dichalcogenides by controlling the d-electron-count has attracted much interest due to their novel structures and physicochemical properties. 1T'' ReSe 2 is a promising candidate for sodium storage, but the low electronic conductivity and limited active sites hinder its electrochemical capacity. Herein, new-phase 1T' Re 0.75 V 0.25 Se 2 crystals (P2/m) with zig-zag chains are successfully synthesized. The 1T''-1T' phase transition results from the electronic reorganization of 5d orbitals via electron extraction after V-atom doping. The electrical conductivity of 1T' Re 0.75 V 0.25 Se 2 is 2.7 × 10 5 times higher than that of 1T'' ReSe 2 . Moreover, density functional theory (DFT) calculations reveal that 1T' Re 0.75 V 0.25 Se 2 has a larger interlayer spacing, lower bonding energy, and migration energy barrier for Na + ions than 1T'' ReSe 2 . As a result, 1T' Re 0.75 V 0.25 Se 2 electrode shows an excellent rate capability of 203 mAh g -1 at 50 C with no capacity fading over 5000 cycles for sodium storage, which is superior to most reported sodium-ion anode materials. This 1T' Re 0.75 V 0.25 Se 2 provides a new platform for various applications such as electronics, catalysis, and energy storage.