Ordered assembly of potassium cobalt hexacyanoferrate hollow multivoid nanocuboid arrays for high-performance aqueous K-ion batteries towards all-climate energy storage

Abstract

Aqueous potassium-ion batteries (AKIBs) with high-safety, low-cost and environmental-friendliness are competitive candidates in the field of energy storage. However, concerns on their inferior durability, poor rate-capability as well as limited selection of suitable electrode materials greatly restrict their progress. Herein, ordered arrays which are assembled from potassium mediated Co–Fe based Prussian blue (KCoFe-PB) hollow multivoid nanocuboids (HMCs) are employed as cathodes for AKIBs. The ordered arrangement of the assembly, the hollow centered nature of the HMCs, and the 3D crystal framework of KCoFe-PB synergistically facilitate the electron/ion transport, which ensures fast kinetics and good stable cycling performance. Theoretical calculations disclose the facile potassium migration pathway with a low energy barrier, and the experimental results reveal the multiple-electron-transfer processes of KCoFe-PBA HMCs in the aqueous potassium-ion system. The full AKIB which is built from the high-performance KCoFe-PBA HMC cathode, organic (PTCDI) anode, and water-in-salt electrolyte (WiSE) achieves excellent energy density, high power density, and fabulous capacity retention after long-term cycling (79% after 3000 cycles). More impressively, the fabricated pouch-type AKIB is able to operate smoothly at high rates (0.5 to 6C) in a wide temperature range (−20 to 40 °C), which testifies its superior adaptability to temperature change. Therefore, this work not only gives a new clue to fabricate fast and durable electrodes for AKIBs, but also promotes the innovation of high-performance power sources for all-climate energy storage.