Irreversible Electrochemical Reaction at High Voltage Induced by Distortion of Mn and V Structural Environments in Na₄MnV(PO₄)₃

As the importance of developing low-cost and high-capacity materials is emerging, Mn-based Na4MnV(PO4)3 positive electrode that allow multiredox reactions are in spotlight for Na-ion batteries. The structure gives highly reversible electrochemical reactions, when two Na+ (out four) de-inserted, deteriorates rapidly third extracted at high voltage, resulting poor cyclability. In this work, using synchrotron-based operando techniques, we perform long-range local structural analyses to determine origins rapid decay extracted. Operando XRD shows a significant change crystal (c parameter increases rapidly) as occupancy Na (1) site decreases voltage. environments Mn V, monitored by XAS, remain rather symmetrical up extraction Na+, while both V show drastic distortions These degradations found further progress cycling This study presents important aspects how modifications can affect performance NASICON materials.