Atomic-interface strategy and N,O co-doping enable WS2 electrodes with ultrafast ion transport rate in sodium-ion batteries

The high theoretical capacity and graphene-like structure enable WS2 to be a promising anode material for fast-charging sodium-ion batteries. However, poor intrinsic electrical conductivity and large Na+-diffusion energy barrier limit its practical applications. Here, an atomic-interface strategy and N,O co-doping were first introduced for WS2 electrodes to obtain a unique WS2/C nanocomposite. The atomic-interface strategy that allowed the construction of a unilamellar interoverlapped superstructure maximized the contact area of WS2 and C, thus significantly improving the electrical conductivity and decreasing the Na+-diffusion energy barrier of WS2 electrodes during cycling. More importantly, the atomic-interface strategy suppressed the growth of superparamagnetic W metallic nanoparticles during conversion reactions, resulting in a strong surface-capacitance effect to boost the Na+ transport. Besides, N,O co-doping changed the electronic structure of WS2 to decrease the bandgap from 1.6 to 0 eV and enlarged the interlayer spacing between WS2 and C, thus boosting the electron and ion transport. Consequently, WS2/C exhibited an ultrafast Na+-storage capability (450.8 mA h g(-1) at 13 A g(-1)), with an ultrahigh capacity of 669.2 mA h g(-1) at 0.065 A g(-1) and an ultralong lifetime of over 3000 cycles at 6.5 A g(-1) in half-cells. Further, the full-cells showed superior fast-charging capability with an 80.6% capacity retention at 1.95 A g(-1).