Addressing the Challenges of 3C-SiC—Synergetic Effect of Conductive Additives on the Performance of SiC as Anode Material for Lithium-Ion Batteries

Abstract

This study investigates the electrochemical contribution of silicon carbide (SiC) in SiC/carbon black (CB) composites for the use in lithium-ion battery anodes. High-purity, nitrogen-doped 3C-SiC is synthesized via an environmentally friendly sol–gel method, producing silicon dioxide (SiO2)-free microsized crystals. Due to the low interparticle conductivity, conductive carbon additives are therefore necessary to enable lithiation. However, the electrochemical activity of these conductive carbon additives is often overlooked, with the measured capacity typically attributed solely to SiC. Here, the contributions of SiC and CB to the overall electrode capacity are clearly differentiated. The findings support the hypothesis that charge storage involves both CB and SiC, whereas CB still remains the main contributor. For a typical SiC electrode with 20% CB, a reversible capacity of 72 mAh g−1 is achieved at 1C in the 10th cycle, with SiC contributing 47% to the total capacity. Kinetic analysis reveals that lithium (Li) storage in SiC/CB is predominantly surface-controlled, with SiC contributing partially through Li+ diffusion. This provides direct evidence that SiC actively participates in lithium storage, with lithiation occurring primarily through a surface-controlled process within the first few SiC layers, complemented by limited bulk diffusion. This explains the relatively low capacity of SiC compared to the theoretical capacity.