Porous graphene-like MoS/carbon hierarchies for high-performance pseudocapacitive sodium storage

Layered MoS 2 has been considered as a promising anode material for sodium-ion batteries (SIBs), but it suffers from low electric/ionic conductivity as well as severe volume variation upon ion insertion/extraction, which leads to poor electrochemical performance. To address this issue, we demonstrate a facile synthesis of graphene-like MoS 2 /carbon (denoted as MoS 2 /C) with porous hierarchical nanostructures, in which few-layered MoS 2 with expanded (002) planes is successfully hybridized/doped with N,S-codoped carbon species, via a template-assisted nanocasting method. The simultaneous thermal decomposition of the Mo/S source ( i.e. , (NH 4 ) 2 MoS 4 ) and the N/C source ( i.e. , polyvinyl pyrrolidone, PVP) within the confined spaces constructed by the removable template ( i.e. , CaCO 3 ) leads to the straightforward hybridization/doping of MoS 2 /C, and the carbon content can be readily controlled by adjusting the amount of PVP introduced, which greatly affects the sodium storage performance of the electrodes. After template removal, the as-prepared porous MoS 2 /C hierarchies constructed by graphene-like nanosheets display a large pore volume and highly exposed active surface, which efficiently enhance the electrical conductivity and the ion diffusivity. When evaluated as an anode material for SIBs, the optimized MoS 2 /C electrode demonstrates predominantly pseudocapacitive sodium storage behavior (with a high contribution of 89.9% at 1.2 mV s −1 ), delivering high reversible capacities of 397 mA h g −1 at 0.5 A g −1 after 300 cycles and 370 mA h g −1 at 1 A g −1 after 1000 cycles. Few-layered graphene-like MoS 2 /carbon composite with porous hierarchical nanostructures was prepared via a template-assisted pyrolysis method, which demonstrated excellent sodium storage performance with high pseudocapacitance contribution.