High-Entropy Layer Grown on Mn-Based Prussian Blue Analog for Na-Ion Storage

Mn-based Prussian blue analogs (MnPBAs) are used as cathodes for Na-ion batteries because of their specific capacity. However, their practical application is limited by low electron/ionic conductivity and the Jahn–Teller effect, which lead to poor rate performance and cycle stability. Herein, we propose a core–shell MnPBA cathode with a high-entropy coating layer through an epitaxial growth strategy to address the above issues. Owing to the synergistic cocktail effect and the buffering function, the high-entropy PBA (HEPBA) serves as a conductive and protective layer to promote ionic conductivity and inhibit the Jahn–Teller distortion from inner MnPBA. Therefore, the obtained MnPBA@HEPBA (M@H-PBA) cathode inherits the capacity contribution of the core and the structural stability of the shell. Specifically, M@H-PBA delivers 81.8% capacity retention after 1000 cycles at 1 A g–1. Combined with glucose-derived hard carbon (GHC), the specific capacity of the GHC∥M@H-PBA full cell retains about 80.0% after 400 cycles at 0.1 A g–1.