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

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.