Zn-Ion Batteries: Boosting the Rate Capability and Low-temperature Performance by Combining Structure and Morphology Engineering

Prussian blue analogues (PBAs) have been considered as one kind of the most promising cathode materials for Zn-ion batteries (ZIBs) due to their low cost, high performance, high safety, and high abundance. However, owing to the low conductivity and single electron reaction, it is a great challenge to obtain a PBA cathode material with high reversible capacity, high rate capability, and good temperature adaptability. Here, a cathode material, K-1.14(VO)(3.33)[Fe(CN)(6)](2)center dot 6.8H(2)O (KVHCF), with a multielectron reaction and double conductive carbon framework (DCCF) is designed and synthesized by combining structure and morphology engineering. With the multielectron reaction and high electronic conductivity simultaneously, the KVHCF@DCCF cathode material delivers a high specific capacity (180 mAh.g(-1) @ 400 mA.g(-1)) and the best rate performance (116 mAhg(-1) @ 8000 mA.g(-1)) of the reported PBAs. Moreover, KVHCF@DCCF presents a high specific capacity of 132 mAh.g(-1) @ 400 mA.g(-1) at 0 degrees C. Even at -10 degrees C, it still delivers specific capacities of 127 mAh.g(-1) @ 40 mA.g(-1) and 80 mAh.g(-1) @ 400 mA.g(-1) with a retention of 86% after 700 cycles. In situ X-ray diffraction (XRD) and ex situ X-ray photoelectron spectroscopy (XPS) are carried out to investigate the charge-discharge electrochemical reaction mechanism.