4. Conclusion
SCNTs and SNCNTs have been successfully synthesized by calcination of CNTs and NCNTs in SO2-containing atmosphere. Recycling of S species has been realized with the design of SO2generator and absorber, where SO2 is generated by CaSO3 pyrolysis and absorbed by CaO, respectively. A delayed SO2 release at a temperature slop from 715 to 800 ÂșC is selected to match with the gaseous S doping reaction. Whether in the organic system or aqueous system, the LFP cathode with the SCNT-S as conductive additive exhibits higher capacity and better rate performance as compared to the electrode with the pristine CNTs. Our results provide a novel method to synthesize high quality SCNTs at large scale and low cost.