Self-healing of manganese Prussian blue analogues via thermodynamically driven in situ engineered nickel cages in electrochemical processes

Abstract

Although manganese Prussian blue analogues (Mn-PBAs) offer advantages as cost-effective, high-energy-density cathode materials for sodium-ion batteries, their practical application is severely constrained by substantial capacity degradation during long-term cycling. This performance deterioration is closely associated with the structural instability of the material during the cycling process, which is mainly attributed to the gradual dissolution of the active material into the electrolyte and severe lattice distortion during Na⁺ intercalation/deintercalation. Fortunately, the aforementioned challenges can be effectively addressed by fabricating an in situ engineered nickel cage (ISE-NC) on Mn-PBAs (denoted as Mn-PBAs-NC). Experimental characterization combined with theoretical calculations reveals that this spontaneously formed nickel cage not only suppresses the diffusion of Mn-PBAs into the electrolyte but also acts as a structural stabilizer, significantly alleviating lattice distortion during cycling. This dual stabilization mechanism ensures remarkable cycling stability, with Mn-PBAs-NC delivering a retained capacity of 96.4 mA h g⁻¹ (80 % capacity retention) over 2,300 cycles at 2 C, elevating the cycle life of Mn-PBAs to unprecedented levels.