Micro-sized Si-C Composite with Interconnected Nanoscale Building Blocks as High-Performance Anodes for Practical Application in Lithium-Ion Batteries

TLDR: In this paper, a Si-C nanocomposites (e.g., nanowires, nanotubes, or nanoparticles) has been used to improve the capacity and cycling stability of high-energy-density lithium-ion batteries.

Abstract: The emerging markets of electric vehicles (EV) and plug-in hybrid electric vehicles (PHEV) generate a tremendous demand for low-cost lithium-ion batteries (LIBs) with high energy and power densities and long cycling life. [ 1–4 ] The development of such LIBs requires development of low cost, high energy-density cathode and anode materials. Conventional anode materials in commercial LIBs are primarily synthetic graphite-based materials with a capacity of ∼ 370 mAh/g. [ 5 ] Improvements in anode performance, particularly in anode capacity, are essential to achieving high energy densities in LIBs for EV and PHEV applications. Silicon has been intensively pursued as the most promising anode material for high-energy-density LIBs because of its high specifi c capacity ( > 3500 mAh/g) and abundance. [ 6 ] Despite its high capacity, Si suffers from fast capacity fading caused by its large volume change ( > 300%) during lithiation/delithiation and the serious issues stemming from this volume change, e.g., unstable solid electrolyte interphase (SEI) and disintegration (cracking and crumbling) of the electrode structure. [ 7 , 8 ] The development of Si-C nanocomposites (e.g., nanowires, nanotubes, or nanoparticles) has been widely studied. [ 9–18 ] These nanocomposites proved to be an effective method of improving capacity and cycling stability, since nano-sized Si can alleviate fracture during volume changes and the contact between Si and carbon can maintain electrical contact and improve conductivity of the nanocomposites. However, practical application of nano-sized Si materials in LIBs is diffi cult. First, achieving a high tap density is important for fabrication of high-energy LIBs for EVs and PHEVs, because it offers a high volumetric energy density. Unfortunately, the tap density of nano-sized materials is generally low, which in turn holds down their volumetric capacity. [ 19 ] Furthermore, preparation of nano-sized Si either requires chemical/physical vapor deposition or involves complicated processes, leading to costly, low-yield synthesis that is diffi cult to scale up to practical levels. [ 20–22 ] To date, the abundance of Si has not been fully capitalized upon due to lack