Design of Lamellar Mo₂C Nanosheets Assembled by Mo₂C Nanoparticles as an Anode Material toward Excellent Sodium-Ion Capacitors

Abstract

Sodium-ion capacitors (SICs) have attracted growing attention since they can combine the advantages of sodium-ion batteries (SIBs) and electrochemical capacitors simultaneously. The key point of constructing SICs focuses on developing high electron conductive anode materials and overcoming huge volume variation during the sodiation/desodiation process to improve excellent cycling stability and rate performance. Here, lamellar Mo2C nanosheets assembled by Mo2C nanoparticles (NPs) were successfully synthesized via a facile hydrolysis method with a calcination process, demonstrating an outstanding rate capability with superior cycle stability at 0.5 A g–1 after 1200 cycles (0.097% decay per cycle from the second to the 1200th cycle) in the half cell. After coupling with a commercial activated carbon cathode, SICs demonstrates a high energy and power density of 76.1 Wh kg–1 at 112 W kg–1 and an excellent cycle life with 83% of the capacity retained after 4000 cycles. The research shows that the lamellar Mo2C nanosheets assembled by Mo2C nanoparticles as a competitive anode material for sodium-ion hybrid devices can accommodate the volume change during the sodiation/desodiation and shorten the Na+ diffusion path because of its interconnected lamellar structure.