Bond Structure Engineering Induced the Mn Redox Stabilization Toward High‐Energy Mn‐Based Phosphate Cathode

Abstract

AbstractManganese (Mn) ‐based phosphate is poised for commercial applications driven by its cost‐effectiveness, robust NASICON framework, and multi‐dimensional Na+ pathways. However, it encounters insufficient redox reactions and rapid structural collapse with severe lattice distortion as the culprit. Herein, one meticulously engineered substitutional solid solution cathode (integrating Na4MnCr(PO4)3 and Na3MnTi(PO4)3, denoted NMCTP) is proposed to regulate the local crystal structure of Mn─O bond to stabilize and promote the Mn redox reaction for optimizing the electrochemical performance. It is uncovered that the bulk framework with structural stability is constructed by strongly symmetric Mn─O bond lengths of MnO6 octahedrons and strengthened Mn─O covalency. In addition, the sufficient utilization of Mn redox is tightly correlated with redistributed Na2 occupancy and enhanced diffusion kinetics with accelerated electron transportation. By virtue of the above merits, The NMCTP performs ultra‐high capacity (150.3 mAh g−1 at 0.1 C) and appealing cycling stability (84.7% retention over 1000 cycles). Sodium storage mechanisms and potential factors at high potentials are unveiled in NMCTP materials. This work sheds light on fire‐new solid solution strengthening in view of the Mn─O bond structure for high‐performance Mn‐based phosphate cathodes.