Antibonding orbital tailor and stress relief engineering for FeS2 complex toward superior sodium storage

The sluggish kinetics behaviors and vast volume variations of Na+ hosts to FeS2 anode involved intercalation, and conversion reactions plague its applicability of sodium-ion batteries (SIBs). Here, a significantly expedited kinetics via cation intercalation and considerably relieved stress accumulation by constructing the concave scaffold protector are approached for FeS2 complex. Upon Mn2+ intercalation into FeS2, a new stable Mn–FeS2 was generated with distorted coordination; elevated antibonding orbital occupancy and lowed d band center to the release of more free Na+ were achieved, which was further encapsulated by hollow bowl-like carbon spheres (BC). This cation intercalation and concave morphology strategies confer Mn–FeS2@BC significantly enhanced electron/ion transport kinetics via reversed electron transfer to FeS2, fast desolvation kinetics, and evidently depressed structural deformation during Na+ insertion and extraction. Consequently, Mn–FeS2@BC delivers the longevity and stable Na+ storage capacity in both half and full cell device. Moreover, Mn–FeS2@BC also displays excellent adaptability in a wider temperature range. This work proposes new views into the deep regulation of electrochemical performance of transition metal anodes via intercalation chemistry and concave engineering.