Multiscale Buffering Engineering in Silicon-Carbon Anode for Ultrastable Li-Ion Storage

Abstract

Silicon-carbon (Si-C) hybrids have been proven to be the most promising anodes for the next-generation lithium-ion batteries (LIBs) due to their superior theoretical capacity (?4200 mAh g-1). However, it is still a critical challenge to apply this material for commercial LIB anodes because of the large volume expansion of Si, unstable solid-state interphase (SEI) layers, and huge internal stresses upon lithiation/delithiation. Here, we propose an engineering concept of multiscale buffering, taking advantage of a nanosized Si-C nanowire architecture through fabricating specific microsized wool-ball frameworks to solve all the above-mentioned problems. These wool-ball-like frameworks, prepared at high yields, nearly matching industrial scales (they can be routinely produced at a rate of 300 g/h), are composed of Si/C nanowire building blocks. As anodes, the Si-C wool-ball frameworks show ultrastable Li+ storage (2000 mAh g-1 for 1000 cycles), high initial Coulombic efficiency of 90%, and volumetric capacity of 1338 mAh cm-3. In situ TEM proves that the multiscale buffering design enables a small volume variation, only 19.5%, reduces the inner stresses, and creates a very thin SEI. The perfect multiscale elastic buffering makes this material more stable compared to common Si nanoparticle-assembled counterpart electrodes.