Prussian Blue Analogues with Optimized Crystal Plane Orientation and Low Crystal Defects toward 450 Wh kg-1 Alkali-Ion Batteries

Prussian blue analogues (PBAs) have been regarded as promising cathode materials for alkali-ion batteries owing to their high theoretical energy density and low cost. However, the high water and vacancy content of PBAs lower their energy density and bring safety issues, impeding their large-scale application. Herein, a facile potassium-ions assisted strategy is proposed to synthesize highly crystallized PBAs. By manipulating the dominant crystal plane and suppressing vacancies, the as-prepared PBAs exhibit increased redox potential resulting in high energy density up to approximate to 450 Wh kg(-1), which is at the same level of the well-known LiFePO4 cathodes for lithium-ion batteries. Remarkably, unconventional highly-reversible phase evolution and redox-active pairs were identified by multiple in situ techniques for the first time. The preferred guest-ion storage sites and migration mechanism were systematically analysed through theoretical calculations. We believe these results could inspire the design of safe with high energy density.

Automated summary

Prussian blue analogues (PBAs) have high theoretical energy density and low cost, but their high water and vacancy content lower the energy density and pose safety issues. A potassium-ions assisted strategy is proposed to synthesize highly crystallized PBAs, which exhibit increased redox potential and high energy density of approximately 450 Wh kg(-1). In addition, unconventional highly-reversible phase evolution and redox-active pairs were identified for the first time, and the preferred guest-ion storage sites and migration mechanism were systematically analyzed through theoretical calculations.