Accelerating redox kinetics of sulfurized polyacrylonitrile nanosheets by trace doping of element

“Solid-solid” conversion mechanism of sulfurized polyacrylonitrile (SPAN) could eliminate the “shuttle effect” of polysulfides intermediate in Li[sbnd]S batteries, but it leads to poor redox reaction kinetics. Herein, traces of high conductivity elements Se and Te are doped in two-dimensional SPAN nanosheets (NS) by co-heating method. This synergistic effect enhances the conductivity of SPAN while affording a larger contact area with the electrolyte and shortening the electron/ion transport path. As a result, both the energy barrier for redox reaction and polarization for battery are decreased. At a high current density of 3 A g⁻¹, Te_0.052S_0.948PAN NS and Se_0.071S_0.929PAN NS exhibit significantly enhanced discharge capacities of 485 mA h g⁻¹_composite and 457 mA h g⁻¹_composite, respectively, while SPAN nanoparticles (NP) only delivers a capacity of 417 mA h g⁻¹_composite. At 0.2 A g⁻¹ current density, the capacity retention rates of Te_0.052S_0.948PAN NS and Se_0.071S_0.929PAN NS are 92.20 % and 56.10 % after 200 cycles, respectively, both higher than the 40.10 % of SPAN NP. When the loading amount is further increased, Te_0.052S_0.948PAN NS and Se_0.071S_0.929PAN NS still maintain excellent electrochemical performance. In-situ Raman and XPS analysis confirms the reversible breaking and formation of C[sbnd]S/S[sbnd]S bonds during the first cycle. Additionally, XPS and SEM analysis after 100 cycles demonstrate the stable nanostructure and molecular structure of Se_0.071S_0.929PAN NS and Te_0.052S_0.948PAN NS throughout the cycling process. These results herald a new approach to high redox kinetics of SPAN by the synergistic effect of elements doping and nanoscale modulation.