Breaking low-strain and rapid-kinetics trade-off in heterostructured prussian blue cathode toward robust sodium storage.

Manganese-based hexacyanoferrate has garnered unprecedented attention for sodium-ion batteries due to their high theoretical capacity. However, the structural strain associated with Jahn-Teller distortion incurs fast capacity decline and poor rate capability. Effectively reconciling the trade-off between low-strain and rapid-kinetics in manganese-based hexacyanoferrate cathode poses a considerable challenge. Herein, an elegant strategy based on the stress engineering of heterointerface on nickle-doped manganese hexacyanoferrate@nickle hexacyanoferrate core@shell cathode is proposed to balance the volume strain and charge transfer kinetics during charge/discharge process. As evidenced by the operando X-ray diffraction experiments, differential electrochemical mass spectrometry, and theoretical calculations, the interfacial stress can be regulated by precisely tailoring the shell thickness to stabilize the built-in electric field, which ensures the good structural stability and fast charge diffusion kinetics. Consequently, the as-developed cathode delivers a reversible capacity of 81.0 mAh g, excellent cycling stability (81.9 % of capacity retention after 800 cycles), and superior rate performance (55.1 mAh g at 10 C). Our work heralds a promising strategy of heterointerface strain engineering for exploring advanced MnHCFs cathode materials toward high-performance sodium storage.