This study proposes a conformal surface coating of conducting polymer for protecting 1D nanostructured electrode material, thereby enabling a free‐standing electrode without binder for sodium ion batteries. Here, polypyrrole (PPy), which is one of the representative conducting polymers, encapsulated cobalt phosphide (CoP) nanowires (NWs) grown on carbon paper (CP), finally realizes 1D core–shell CoP@PPy NWs/CP. The CoP core is connected to the PPy shell via strong chemical bonding, which can maintain a Co–PPy framework during charge/discharge. It also possesses bifunctional features that enhances the charge transfer and buffers the volume expansion. Consequently, 1D core–shell CoP@PPy NWs/CP demonstrates superb electrochemical performance, delivering a high areal capacity of 0.521 mA h cm−2 at 0.15 mA cm−2 after 100 cycles, and 0.443 mA h cm−2 at 1.5 mA cm−2 even after 1000 cycles. Even at a high current density of 3 mA cm−2, a significant areal discharge capacity reaching 0.285 mA h cm−2 is still maintained. The outstanding performance of the CoP@PPy NWs/CP free‐standing anode provides not only a novel insight into the modulated volume expansion of anode materials but also one of the most effective strategies for binder‐free and free‐standing electrodes with decent mechanical endurance for future secondary batteries.
Considering that the high capacity,l ong-term cycle life,and high-rate capability of anode materials for sodium-ion batteries (SIBs) is abottleneckcurrently,aseries of Co-doped FeS 2 solid solutions with different Co contents were prepared by afacile solvothermal method, and for the first time their Nastorage properties were investigated. The optimized Co 0.5 Fe 0.5 S 2 (Fe0.5) has discharge capacities of 0.220 Ah g À1 after 5000 cycles at 2Ag À1 and 0.172 Ah g À1 even at 20 Ag À1 with compatible ether-based electrolyte in av oltage windowo f 0.8-2.9 V. The Fe0.5 sample transforms to layered Na x Co 0.5 Fe 0.5 S 2 by initial activation, and the layered structure is maintained during following cycles.T he redoxr eactions of Na x Co 0.5 Fe 0.5 S 2 are dominated by pseudocapacitive behavior, leading to fast Na + insertion/extraction and durable cycle life. AN a 3 V 2 (PO 4 ) 3 /Fe0.5 full cell was assembled, delivering an initial capacity of 0.340 Ah g À1 .
Fast lithium ion and electron transport inside electrode materials are essential to realize its superb electrochemical performances for lithium rechargeable batteries. Herein, a distinctive structure of cathode material is proposed, which can simultaneously satisfy these requirements. Nanosized Li3V2(PO4)3 (LVP) particles can be successfully grown up on the carbon nanofiber via electrospinning method followed by a controlled heat‐treatment. Herein, LVP particles are anchored onto the surface of carbon nanofiber, and with this growing process, the size of LVP particles as well as the thickness of carbon nanofiber can be regulated together. The morphological features of this composite structure enable not only direct contact between electrolytes and LVP particles that can enhance lithium ion diffusivity, but also fast electron transport through 1D carbon network along nanofibers simultaneously. Finally, it is demonstrated that this unique structure is an ideal one to realize high electron transport and ion diffusivity together, which are essential for enhancing the electrochemical performances of electrode materials.
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