Engineering 3D Well-Interconnected Na4MnV(PO4)3 Facilitates Ultrafast and Ultrastable Sodium Storage

Na4MnV(PO4)3 (denoted as NMVP) has drew increasing attention owing to the three-dimensional framework and high theoretical capacity. Nevertheless, the inherent low electronic conductivity of NMVP impedes the scale-up commercial applications. In this work, the feasibility to achieve ultrahigh-rate capability and long lifespan by in-situ embedding the intertwined carbon nanotube matrix into the bulk of Na4MnV(PO4)3@C composites through a facile wet-chemical approach is reported. The elaborately prepared Na4MnV(PO4)3@C@CNTs cathode delivers discharge capacity of 109.9 mA h g-1 at C/5 with impressive rate capability of 68.9 mA h g-1 at ultrahigh current rate of 90 C as well as fascinating cycling performance of 68.3% capacity retention at 40 C after 4000 cycles. The optimum design of the 3D well-interconnected NMVP permitting fast kinetics for transported Na+/e- is beneficial to the excellent electrochemical performance, which is further studied by GITT, CV and EIS measurements. The pseudocapacitance contributions are also investigated. The research demonstrates that the dual-nanocarbon synergistically modified NMVP composite is expected to facilitate the commercialization of sodium-ion batteries.