Sodium Ion Storage in Na_4MnV(PO_4)_3@C Free-Standing Electrode

摘要

To enhance the energy density of batteries and explore intrinsic chargestorage mechanism of the active materials, it is important to reduce oreliminate the use of non-active materials in electrodes, such as binderand conductive additives. Herein, free-standing Na4MnV(PO_4)_3@C(F-NMVP@C) fiber membrane is fabricated and directly used as a sodiumionbattery (SIB) cathode. In situ X-ray diffraction reveals that the V~(3+)/V~(4+)redox reaction occurs through a solid-solution reaction while a two-phaseMn~(2+)/Mn~(3+) redox reaction is identified, and both are highly reversible.Meanwhile, ex situ electrochemical impedance spectroscopy revealsthat both the ion diffusion coefficient and charge transfer resistance ofF-NMVP@C change reversibly during the Na~+ intercalation/de-intercalation.Battery full cells are assembled based on the free-standing F-NMVP@Ccathodes and F-Sb@C anodes, which manifests a high energy density(293 Wh kg~(?1)) and good cyclability (87.5 after 100 cycles at 1 C). Thehigh-performance free-standing cathodes and anodes shed light on thedevelopment of flexible SIBs.