Silicon-thermally modified polyimide with optimized charge transfer complex structure for enhanced Li-ion storage

Thermally modified polyimide (PI) is investigated as an efficient binder to enhance the Li-ion storage performance of silicon nanoparticles . Heat-treatment of Si@PI electrodes results in an optimized charge transfer complex (CTC) structure, which improves the electrochemical performance of the electrode by forming a compact structure that reduces the charge transfer impedance, significantly enhancing the cycling performance of the silicon anode . Electrodes subjected to the heat-treatment at 350 °C (Si@PI-350) exhibit a charge transfer impedance of 37.67 Ω combined with a reversible Li + storage capacity of 2334 mAh g −1 recorded after 30 cycles at 200 mA g −1 , in comparison to the original Si@PI electrodes showing an enhanced impedance value of 130.4 Ω and reduced capacity of 737 mAh g −1 . At a high current density of 2000 mA g −1 , the capacity of Si@PI-350 (1001 mAh g −1 ) is significantly greater than Si@PI (455 mAh g −1 ) highlighting the efficiency of the CTC structures formed during the thermal treatment. We suggest that the thermal treatment of Si@PI electrodes at optimal conditions can significantly affect the Li-ion insertion/extraction cycling performance of silicon nanoparticles.