Synthesis of high-specific-capacity Prussian blue analogues for sodium-ion batteries boosted by grooved structure

To address the issues of low specific capacity and poor cycle performance of Prussian blue analogues as cathode materials for sodium-ion batteries, this work performed surface etching modification on the synthesized Fe_0.8Co_0.2HCF with a regular cubic structure and optimized its electrochemical performance. The resulting grooved structure further enhanced the electrode material significantly. The results show that the etched sample delivers a discharge capacity of 153.3 mAh/g at 0.5 C and retains 83.3% after 200 cycles at 2 C. When the rate returns from 16 C to 0.5 C, the discharge capacity can be maintained at about 90.7%. Based on experimental analysis and theoretical calculation, the improved electrochemical performance of the etched sample is mainly attributed to the following three aspects: (1) fast diffusion of Na⁺; (2) reduced water content; (3) large contact area between electrode and electrolyte.