Surface engineering induced core-shell Prussian blue@polyaniline nanocubes as a high-rate and long-life sodium-ion battery cathode

Surface engineering is highly desirable but still challenging for developing high-rate and long-term life energy storage materials. Herein, Prussian blue@polyaniline nanocube is synthesized by an aqueous precipitation method and the following polymerization process of aniline. Benefiting from the coordinating role of polyvinyl pyrrolidone between Prussian blue and polyaniline, Prussian blue@polyaniline nanocube presents a core-shell structure with a diameter of about 600 nm and the uniform polyaniline coating layer is averagely 20 nm in thickness. The incorporation of polyaniline on Prussian blue is efficient to enhance the electrical conductivity and the kinetics of Na+ transmission during cycling, leading to the higher specific capacity and better rate performance. The sodium storage properties of the cathode are also investigated in different voltage ranges. Owing to the core-shell structure and the optimized voltage range, Prussian blue@polyaniline electrode delivers a specific capacity of 108.3 mAh g(-1) at 100 mA g(-1) with a capacity retention of 93.4% after 500 cycles and maintains a considerable specific capacity of 90.3 mAh g(-1) even at 2 A g(-1) in the voltage range of 2.0-3.6 V. The strategy of polyvinyl pyrrolidone assisted polymerization of polyaniline layer on Prussian blue nanoparticles can be extended to surface modification for other electrode materials.