Adjustable SiC interfacial layers toward reliable Si-based anode applications.

The incorporation of a SiC interfacial layer has been recognized as an effective strategy to tackle the interface contact issue between Si and carbon, ensuring the structural integrity of Si-based anodes and thereby enhancing their cycling stability. However, its inherent low activity and poor conductivity pose a persistent challenge for maximizing capacity and facilitating ion and electron transport. Here, we present a thickness/content adjustable SiC interfacial layer in the Si-SiC-C heterostructure using a modified spark plasma sintering technique. The SiC layer, with a content of ∼10%, is discretely coated on the surface of the Si core, exerting minimal influence on capacity and ion/electron kinetics, while ensuring high electrode structural stability. Consequently, the Si-based anode exhibits a stable capacity of 582 mAh g (0.1 A g) and good rate capability (324 mAh g at 2 A g), while maintaining 80% capacity retention over 500 cycles with a low electrode swelling of 12.6%. More importantly, its capacity presents a continuous rising trend with the increase of the cycle number, suggesting a mechanism where the SiC interfacial layer gradually transforms into a Li-ion-rich phase. This transformation facilitates ion transport and reaction with Si, resulting in gradual capacity enhancement. Therefore, the reasonably thickness-regulated SiC interfacial layer holds promise for providing inspiration for the design of commercial Si-based anodes.