Layered Binder-Free C/Si Anodes for Li Ion Batteries

Abstract

Novel high-energy, binder-free, and solvent-free carbon–silicon layered composite anodes were manufactured using an industrially scalable Virtual Cathode Deposition (VCD) technique. The deposition process transforms commercial graphite target material into carbon polymorph (CALIB) layers, interposed with silicon layers deposited in situ from a silicon source, thereby forming high-capacity anodes for Li ion batteries. Composite CALIB-C/Si4 anodes with a layered architecture exhibited a first-cycle specific capacity of over 1550 mAh g−1 at 0.1 A g−1 and retained a capacity of ~1080 mAh g−1 at a 1 A g−1 rate after 200 cycles. Detailed structural characterisation revealed a disordered carbon matrix encompassing nanosized sp2-bonded carbon clusters (average size ~20 nm), cross-linked by a network of sp3-bonded atomic sites, with predominant mesoporosity and high surface area. The silicon layers were found to consist of an amorphous Si matrix with embedded nanocrystalline components, emulating the growth mode of the CALIB buffer. The presence of the mesoporous carbon matrix accommodated the stress caused by the alloying/de-alloying of silicon nanolayers, thereby alleviating the pulverisation effect and preserving the structural integrity of the composite. The initial performance and capacity decay of the anodes were found to depend on the thickness of the CALIB-C buffer interlayers.