Electronic Structure Engineered Heteroatom Doped All Transition Metal Sulfide Carbon Confined Heterostructure for Extrinsic Pseudocapacitor

Ultra-high energy density battery-type materials are promising candidates for supercapacitors (SCs); however, slow ion kinetics and significant volume expansion remain major barriers to their practical applications. To address these issues, hierarchical lattice distorted α-/γ-MnS@Co_xS_y core-shell heterostructure constrained in the sulphur (S), nitrogen (N) co-doped carbon (C) metal-organic frameworks (MOFs) derived nanosheets (α-/γ-MnS@Co_xS_y@N, S-C) have been developed. The coordination bonding among Co_xS_y, and α-/γ-MnS nanoparticles at the interfaces and the π–π stacking interactions developed across α-/γ-MnS@Co_xS_y and N, S-C restrict volume expansion during cycling. Furthermore, the porous lattice distorted heteroatom-enriched nanosheets contain a sufficient number of active sites to allow for efficient electron transportation. Density functional theory (DFT) confirms the significant change in electronic states caused by heteroatom doping and the formation of core-shell structures, which provide more accessible species with excellent interlayer and interparticle conductivity, resulting in increased electrical conductivity. The α-/γ-MnS@Co_xS_y@N, S-C electrode exhibits an excellent specific capacity of 277 mA hg⁻¹ and cycling stability over 23 600 cycles. A quasi-solid-state flexible extrinsic pseudocapacitor (QFEPs) assembled using layer-by-layer deposited multi-walled carbon nanotube/Ti₃C₂T_X nanocomposite negative electrode. QFEPs deliver specific energy of 64.8 Wh kg⁻¹ (1.62 mWh cm⁻³) at a power of 933 W kg⁻¹ and 92% capacitance retention over 5000 cycles.