Effect of in situ pyrolysis of acetylene (C2H2) gas as a carbon source on the electrochemical performance of LiFePO4 for rechargeable lithium-ion batteries

The intention of this work is to study the effect of in situ pyrolysis of acetylene (C2H2) gas used as a carbon source on the physicochemical and electrochemical performance of pristine LiFePO4 (LFP). Acetylene gas, which decomposed to carbon and methane along with some side products when exposed to high temperature (> 625 degrees C), is used as a carbon source for coating over the surface of LFP particles. Thermogravimetric ( TGA) measurements were performed in an air atmosphere, primarily to estimate the exact amount of carbon deposited on the surface of the olivine cathode material due to the decomposition of C2H2 gas. Raman and TGA results confirm the presence of carbon as coated on the surface of the prepared compositions. Among all the synthesized samples, LFP with 10 min C2H2 treatment (LFPC10) shows the highest discharge capacity at all C-rates and exhibits excellent rate performance. LFPC10 delivers a specific discharge capacity of 144 (+/- 5) mAh g(-1) (similar to 85% of the theoretical capacity of 170 mAh g(-1)) at 0.1C rate. LFPC10 demonstrates the best cycling performance as it offers an initial discharge capacity of about 117 (+/- 5) mAh g(-1) (similar to 69% of the theoretical capacity) at 1C-rate and has 97% capacity retention even after 100 charge/discharge cycles.