Prussian blue analogs derived bimetallic sulfide heterostructure in dual-skeleton network of MXene and carbon enabling ultrafast K-ion storage

Transition metal dichalcogenides (TMDs) emerge as advanced anode materials of potassium-ion batteries (PIBs), owing to the impressive capacities, strong redox reversibility, and advantageous conversion reactions with relatively weak metal-sulfur bonds. However, TMDs face inherent drawbacks that contribute to suboptimal rate performance and limited cycling stability such as low electrical conductivity , sluggish reaction kinetics, and unsatisfactory structural stability . To overcome these challenges, ultrafine heterojunction (between CoS 2 and FeS 2 ) wrapped in two-dimensional transition metal carbides (MXene) and nitrogen-sulfur co-doped carbon network (MXene@CoS 2 /FeS 2 @NSC) is synthesized as anodes for PIBs. The built-in electric field generated by heterojunction and high specific surface area network of MXene and carbon both contribute to excellent electrochemical performance . Consequently, the synthesized MXene@CoS 2 /FeS 2 @NSC anode exhibits impressive reversible capacity (605/175 mA h g −1 at 0.05/10 A g −1 ) and outstanding cycling stability (304 mA h g −1 at 0.5 A g −1 after 2000 cycles). The assembled potassium ion capacitors (PICs) with MXene@CoS 2 /FeS 2 @NSC anode exhibit outstanding cycling performance, maintaining nearly 100 % coulombic efficiency and over 10,000 cycles with 96 % capacity retention at 10 A g −1 . This work introduces a versatile synthetic method for preparing bimetallic sulfide heterojunction, providing useful points for the further study of advanced electrode materials for PIBs. This work presents ultrafine CoS 2 /FeS 2 heterojunctions integrated with MXene nanosheets and a nitrogen-sulfur co-doped carbon network (MXene@CoS 2 /FeS 2 @NSC), synthesized through a thermally induced in situ conversion process followed by vulcanization. As anode for potassium ion batteries (PIBs), MXene@CoS 2 /FeS 2 @NSC exhibits impressive electrochemical performance and cycling stability. • A dual-skeleton network of MXene and carbon is utilized to enhance ion transport. • Heterogeneous interface of CoS 2 /FeS 2 improves the reaction kinetics of K + . • The K-ion capacitor presents a high capacity retention of 96 % after 10,000 cycles.