A facile wet-chemical method for synthesizing a nano-sized NiFe-PBA compound with excellent electrochemical performance.

Prussian blue and its analogues with three-dimensional frame structures have been shown to be of great importance in the research and development of sodium-ion batteries (SIBs). Herein, we develop a simple and convenient self-template method to prepare a hollow-structured Prussian blue analogue (CoFe-PBA). This structure is conducive to buffer the volume changes during ion extraction and insertion processes and shorten the ion diffusion path. When further building a thin polydopamine (PDA) coating, the synthesized CoFe-PBA@PDA exhibits a high discharge capacity of 123.1 mAh g −1 at 0.1 A g −1 with a capacity retention of 71.5% after 500 cycles. Moreover, the capacity retention of CoFe-PBA@PDA after 100 cycles is 14.3% higher than that of the two comparison samples. In addition, the reversible structure of CoFe-PBA@PDA without forming a new phase was verified by in situ X-ray diffraction. This work may provide another design idea or strategy for improving the stability of the PBA cathodes used in SIBs.

Solid-state batteries have attracted significant attention due to their safety, but most studies focus on room-temperature performance. Herein, the electrochemical performance of quasi-solid-state sodium-ion batteries (SIBs) based on the perfluorosulfonate-based polymer electrolyte (PFSA-Na) and Na 3 V 2 O 2 (PO 4) 2 F (NVOPF) cathode over a wide temperature range (from À25 to 65 C) is investigated. The quasi-solid-state half-cells (Na//PFSA-Na//NVOPF@rGO) exhibit a long-term cycle life (88.1% capacity retention at 4 C after 1000 cycles) at room temperature. A high discharge capacity can be maintained even at a low temperature of À25 C and it can be restored to the original value when the temperature increases again to 25 C. Meanwhile, full-cells (hard carbon//PFSA-Na//NVOPF@rGO) can also deliver stable cycling performance in a wide temperature range (À25, 25, and 65 C).