Controlled Synthesis of 2D Prussian Blue Analog Nanosheets with Low Coordinated Water Content for High-Performance...

Prussian blue analogs (PBAs) with open and porous frameworks have attracted wide attention in alkali metal ion batteries due to their high theoretical specific capacities and fast ion insertion/extraction kinetics. However, abundant coordinated water usually exists in traditional PBAs synthesized in aqueous systems. Consequently, the competition between coordinated water and alkali ions easily causes the rapid structural collapse of PBAs during the repeated discharge/charge cycles, lowering the cycling stability, and rate performance of batteries. Besides, most reported PBAs adopt the cubic/particle-like morphologies with large sizes, which usually suffer from insufficient ion diffusion especially at high rates. Herein, a facile and general strategy for the synthesis of 2D CoCo, CuFe, CuCeFe, and CuCeCo-based PBA nanosheets is reported. As a proof-of-concept application, Co₃ [Co(CN)₆ ]₂ nanosheets are evaluated as anode materials for lithium-ion batteries. Thanks to the lower coordinated water content, smaller impedance and higher lithium-ion diffusion coefficient, Co₃ [Co(CN)₆ ]₂ nanosheets deliver a superior reversible capacity of 810.4 mAh g^-1 at 100 mA g^-1 , better rate performance, and higher cycling stability compared to common Co₃ [Co(CN)₆ ]₂ cubes. Further studies indicate that the capacitance-controlled electrochemical behaviors dominate in the Co₃ [Co(CN)₆ ]₂ nanosheets, giving rise to their excellent structural stability and superior lithium storage performance even at high rates.