A ZIF-8 modified Prussian blue cathode material for sodium-ion batteries with long cycling life and excellent storage stability

Prussian blue analogues have been intensely investigated as promising cathode materials for sodium-ion batteries owing to their high capacities, easy synthesis and low cost. However, the poor cycling performance due to the presence of lattice defects and the structural deterioration when exposed to humid air hinder their practical application. Herein we report an effective surface modification method to tackle these issues. A Zinc-zeolitic imidazolate framework (ZIF-8) modified PB sample is prepared by in-situ growth via simple wet chemical reaction. The obtained PB@ZIF-8 composite with a ZIF-8 coating layer of ∼70 nm thickness on the 2–5 μm PB particle surface shows excellent cycling stability with reversible capacity of 106.5 mAh g−1 at 1C charge-discharge rate and a remarkable capacity retention of 96.7 % after 500 cycles. Furthermore, the PB@ZIF-8 composite shows excellent storage stability owing to its moisture-proof property. After exposure to high humidity air (RH=70 %) for 24 h or storage for 180 days in a bottle filled with air of relative humidity RH=40 %, the PB@ZIF-8 sample still maintains excellent cycling performance. ZIF-8 coating layer not only acts as a shield for PB particles against the electrolyte corrosion, but also resists the H2O attacking in humid environment.