Honeycomb-like N-Doped Carbon Matrix-Encapsulated Co1−xS/Co(PO3)2 Heterostructures for Advanced Lithium-Ion Capacitors

Lithium-ion capacitors (LICs) are emerging as promising hybrid energy storage devices that combine the high energy densities of lithium-ion batteries (LIBs) with high power densities of supercapacitors (SCs). Nevertheless, the development of LICs is hindered by the kinetic imbalances between battery-type anodes and capacitor-type cathodes. To address this issue, honeycomb-like N-doped carbon matrices encapsulating Co1−xS/Co(PO3)2 heterostructures were prepared using a simple chemical blowing-vulcanization process followed by phosphorylation treatment (Co1−xS/Co(PO3)2@NC). The Co1−xS/Co(PO3)2@NC features a unique heterostructure engineered within carbon honeycomb structures, which efficiently promotes charge transfer at the interfaces, alleviates the volume expansion of Co-based materials, and accelerates reaction kinetics. The optimal Co1−xS/Co(PO3)2@NC composite demonstrates a stable reversible capacity of 371.8 mAh g−1 after 800 cycles at 1 A g−1, and exhibits an excellent rate performance of 242.9 mAh g−1 even at 8 A g−1, alongside enhanced pseudocapacitive behavior. The assembled Co1−xS/Co(PO3)2@NC//AC LIC delivers a high energy density of 90.47 Wh kg−1 (at 26.28 W kg−1), a high power density of 504.94 W kg−1 (at 38.31 Wh kg−1), and a remarkable cyclic stablitiy of 86.3% retention after 5000 cycles. This research is expected to provide valuable insights into the design of conversion-type electrode materials for future energy storage applications.