Effect of conductive agent ratio on the capacity and cycling performance of graphite/silicon anode

Abstract

Graphite/silicon composite electrodes can be important for high energy density lithium-ion batteries; however, repeated volume changes of silicon can cause electrode structural degradation, loss of electrical contact, and increased polarization. In this experiment, the effect of the CNT/Ketjenblack (KB) ratio on the electrochemical performance and transport characteristics of graphite/silicon composite electrodes was observed. Coin-type half cells with different CNT/Ketjenblack ratios were fabricated and evaluated through formation, rate capability, and cycle-life tests. Electrochemical impedance spectroscopy (EIS) was performed to explore resistance components and mass transport behavior within the electrodes. Electronic resistance, including composite and interfacial resistances, was measured to compare electrical contact, and porosity and tortuosity were examined to characterize ionic transport pathways. The electrode microstructure was observed using scanning electron microscopy (SEM), focusing on electrode cracking and volume expansion, and energy-dispersive X-ray spectroscopy (EDS) was used to examine the spatial distribution of electrode components. Overpotential behavior during rate capability and cycle-life tests was examined to observe polarization characteristics, and differential capacity analysis was subsequently performed to investigate changes in electrochemical reaction behavior during cycling. The results show that electrochemical performance varies with the CNT/Ketjenblack ratio, with higher Ketjenblack contents favoring improved transport behavior. This indicates that adjusting the conductive additive ratio can provide a practical method to regulate transport-related polarization, thereby improving rate capability and cycling stability.