The influence of pyrolysis temperature on the electrochemical behavior of porous carbon-rich SiCN polymer-derived ceramics

Within this study we report on the impact of the pyrolysis temperature on the structural and electrochemical properties of porous carbon-rich polymer-derived silicon carbonitride (SiCN) ceramics. Microstructural features of the synthesized materials were characterized in detail and discussed with respect to the lithium storage properties. X-ray diffraction study reveals the amorphous nature of the pyrolysed ceramics up to 1100 °C, while a crystalline SiC-phase is formed at 1400 °C. Micro-Raman spectroscopy shows that pyrolysed samples contain a free disordered carbon phase which tends to order with increasing pyrolysis temperature. Galvanostatic cycling with potential limitation enables to monitor the lithiation and delithiation performance. High irreversible losses are identified during the first cycle lithiation due to formation of SEI. Nevertheless the highest electrode capacities are recorded for the sample pyrolysed at 900 °C reaching a first cycle reversible capacity of 447 mAh·g− 1 and a 100th cycle reversible capacity of 534 mAh·g− 1 at a current of 72 mA·g− 1. Further it is found that the prepared materials offer improved high current lithium storage ability compared to dense SiCN ceramics reported in literature so far.