Controllable Richen Oxygen Vacancies through Polymer Assistance in Titanium Pyrophosphate as Super Anode of Na/K-Ion Batteries.

Although sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) show golden promising prospects as next energy storage devices, the low capacity and inferior rate capability hindered their further application. Among various phosphate-based polyanion materials, titanium pyrophosphate (TiP2O7) possesses outstanding ion transferability and electrochemical stability. However, it still has rarely been adopted as anode of SIBs/PIBs due to the poor electronic conductivity and nonreversible phase transitions. Herein, an ultra-stable TiP2O7 with enriched oxygen vacancies is prepared as SIBs/PIBs anode through P-containing polymer mediation carbonization, which avoids harsh reduction atmospheres or expensive facilities. The introduction of oxygen vacancies effectively increase pseudocapacitance, diffusivity coefficient and lower the Na insertion energy barrier. As a result, the TiP2O7 anode with enriched oxygen vacancies exhibits ultra-stable Na/K ion storage and superior rate capability. The synthetic protocol proposed here may offer a simple trail to explore advanced oxygen vacancy-type anode materials for SIBs/PIBs.