Realizing Three-Electron Redox Reactions in NASICON-Structured Na3MnTi(PO4)3 for Sodium-Ion Batteries

Developing multielectron reaction electrode materials is essential for achieving high specific capacity and high energy density in secondary batteries; however, it remains a great challenge. Herein, Na3MnTi(PO4)(3)/C hollow microspheres with an open and stable NASICON framework are synthesized by a spray-drying-assisted process. When applied as a cathode material for sodium-ion batteries, the resultant Na3MnTi(PO4)(3)/C microspheres demonstrate fully reversible three-electron redox reactions, corresponding to the Ti (3+/4+)(approximate to 2.1 V), Mn2+/ 3+ (approximate to 3.5 V), and Mn (3+/4+) (approximate to 4.0 V vs Na+/Na) redox couples. In situ X-ray diffraction results reveals that both solid-solution and two-phase electrochemical reactions are involved in the sodiation/desodiation processes. The high specific capacity (160 mAh g(-1) at 0.2 C), outstanding cyclability (approximate to 92% capacity retention after 500 cycles at 2 C), and the facile synthesis make the Na3MnTi(PO4)(3)/C a prospective cathode material for sodiumion batteries.