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

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 degrees 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.

Automated summary

In this study, ordered arrays of potassium mediated Co-Fe based hollow multivoid nanocuboids were used as cathodes for aqueous potassium-ion batteries (AKIBs). The ordered arrangement, hollow structure, and crystal framework of the cathode material facilitated fast kinetics and stable cycling performance. The AKIBs built with this cathode material achieved excellent energy density, power density, and capacity retention even after long-term cycling. Moreover, the pouch-type AKIB showed superior adaptability to temperature changes, operating smoothly at high rates in a wide temperature range.