Environmentally phase-controlled stratagem for open framework pyrophosphate anode materials in battery energy storage

Abstract

Conventional pyrophosphate anode electrochemical performance is restrained by its phase impurity, and the inevitable phase impurity is attributed to the traditional pyrophosphate material being obtained through high temperature (∼1000 °C). Herein, we report a novel phase-control stratagem that can obtain pure phase Mn₂P₂O₇ at 300 °C. The obtained pure phase Mn₂P₂O₇ presents 428.5 mA h g⁻¹ after long cycles with superior stability in lithium ion battery systems. Moreover, it delivers promising electrochemical performance in the Na/K ion battery system. Furthermore, we applied the phase-control stratagem to the synthesis of a few pyrophosphate anodes, and successfully obtained the Co₂P₂O₇, Ni₂P₂O₇, TiP₂O₇, and Fe₂Fe(P₂O₇)₂ anodes, revealing that phase-control chemosynthesis is of great potential to the wide application of pyrophosphate fabrication. The phase controlled stratagem breaks the high temperature and phase impurity limitation of the traditional pyrophosphate anode synthesis, allowing for the stable and promising electrochemical cycling of pyrophosphate materials, and expands the further application and fabrication of pyrophosphate research studies on energy storage materials.