A Mn-based ternary NASICON-type Na3.5MnTi0.5Cr0.5(PO4)3/C cathode for high-performance sodium-ion batteries

The Mn-based Natrium superionic conductor (NASICON)-type materials are promising cathode materials for sodium-ion batteries (SIBs) due to their environmental friendliness and cost-effectiveness. However, the practical application of Mn-based materials is hindered by their poor cycle performance, arising from intrinsic kinetic limitation and negative structural degradation caused byMn. Herein, a Mn-based ternary NASICON-type Na3.5MnTi0.5Cr0.5(PO4)3/C (NMTCP-50) is designed featuring multi-metal synergy with enhanced effect from each component, which contributes to breaking through the bottleneck of inferior cycle performance for Mn-based NASICON-type materials. The results of ex-situ X-ray diffraction corroborate that both solid-solution and bi-phase electrochemical reactions are involved in the sodiation/desodiation processes, and the volume variation is only 2.55 %. Galvanostatic intermittent titration technique tests and density functional theory calculations further demonstrate the fast reaction kinetics of the NMTCP-50 electrode. NMTCP-50 can deliver an excellent cycling durability of 75 % after 5000 cycles at 2 A g−1 and a high reversible capacity of 137.6 mAh g−1. The availability of NMTCP-50 has been evaluated by a full cell assembled with hard carbon. This work offers theoretical support for understanding the multi-metal synergistic effect in NASICON materials and provides a blueprint for designing low-cost NASICON cathodes.