Effect of pyrolysis temperature on the performance of 3D-printed silicon–carbon anodes derived from recycled photovoltaic silicon

Silicon has been proposed as a promising alternative to graphite in the anode of lithium-ion batteries as it offers a higher theoretical specific capacity. In this study, 3-D printed silicon–carbon composite anodes were fabricated from crystalline silicon solar photovoltaic cell waste to investigate the effect of pyrolysis temperature on their structural, electrical, and electrochemical properties. The aim was to suppress the formation of electrochemically inactive SiC observed at 1400 °C in previous work, while maintaining high electrical conductivity and stable structure. Printed anodes were pyrolyzed at 800 °C, 1100 °C, and 1200 °C. The results showed that pyrolysis temperature influences both the microstructure and electrochemical performance of the printed anodes. Pyrolysis at 1200 °C produced a highly conductive carbon matrix without formation of electrochemically inactive SiC. XRD analysis confirmed that at 1200 °C, no SiC peaks appeared. The enhanced graphitization observed in Raman spectra at this temperature, coupled with the reduced charge-transfer resistance in electrochemical impedance spectroscopy, indicates that the carbon network achieved high electronic conductivity while preserving the active silicon phase. As a result, the anode had an initial specific capacity of approximately 771 mAh g-1, with the Coulombic efficiency of 99.9%, and a capacity retention of 61% over 120 cycles. The performance achieved here demonstrates an improvement over the earlier SLA-printed PV-silicon anodes pyrolyzed at 1400 °C, which confirms that tuning pyrolysis temperature is a key strategy to obtain the optimal morphology.