(491f) Silicon/Carbon Nanofiber/Nanoparticle Composite Anodes for Li-Ion Batteries

Particle/polymer electrospinning is a cost-effective and robust technique for fabricating high performance nanofiber mat battery and fuel cell electrodes. For Li-ion battery electrode applications, the advantages of fiber mats over conventional slurry cast electrode designs include: (i) a large electrode/electrolyte interfacial area to enhance electrochemical reaction kinetics, (ii) a controllable interfiber void volume to ensure good electrolyte infiltration into the electrode, and (iii) sub-micron diameter fibers with high nanoparticle content and short Li⁺ transport pathways in the radial fiber direction. Recently, silicon has emerged as a promising next-generation anode material for Li-ion batteries due to its high lithiation capacity, but it suffers from poor cycle stability due to its high volumetric expansion/contraction during charging and discharging. To overcome this problem, a new nanofiber mat electrode design was investigated, where Si nanoparticles were electrospun into fibers with poly(acrylic acid) binder while carbon was simultaneously electrosprayed as nanodroplets with either polyvinylidene fluoride or polyamide-imide binder. Such an anode design separates Si and carbon and provides interfiber free volume to prevent carbon particle pulverization during Si expansion. This talk will describe the method of fabricating this new nanofiber/nanoparticle composite anode and its performance in half-cell cycling experiments. As an example, an anode made with 45% silicon, 20% carbon, and 35% polymeric binder (an areal loading of 1.27 mg cm^-2) achieved a high gravimetric capacity of 900 mAh g^-1 after 100 cycles, 500 mAh g^-1 after 600 cycles, and 300 mAh g^-1 after 1,000 cycles at 1C.