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 CoS2 and FeS2) wrapped in two-dimensional transition metal carbides (MXene) and nitrogen-sulfur co-doped carbon network (MXene@CoS2/FeS2@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@CoS2/FeS2@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@CoS2/FeS2@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.