Metal current collector-free freestanding silicon–carbon 1D nanocomposites for ultralight anodes in lithium ion batteries

Abstract

Although current collectors take up more weight than active materials in most lithium ion battery cells, so far research has been focused mainly on improving gravimetric capacities of active materials. To address this issue of improving gravimetric capacities based on overall cell components, we develop freestanding nanocomposites made of carbon nanofibers (CNFs) and silicon nanowires (SiNWs) as metal current collector-free anode platforms. Intrinsically large capacities of SiNWs as active materials in conjunction with the light nature of freestanding CNF films allow the nanocomposites to achieve 3 ~5 times improved gravimetric capacities compared to what have been reported in the literature. Moreover, three dimensional porous structures in the CNF films facilitate increased mass loadings of SiNWs when compared to flat substrates and result in good cycle lives over 40 cycles. This type of nanocomposite cell suggests that 3D porous platforms consisting of light nanomaterials can provide for higher gravimetric and areal capacities when compared to conventional battery cells based on flat, heavy metal substrates.

Facile synthesis of freestanding Si nanowire arrays by one-step template-free electro-deoxidation of SiO2 in a molten salt

“…The reliance on the substrate of Si NWAs not only limits the variety of preparation, but also hampers the performance in applications. For example, both well-designed Si substrate films 5,6 and freestanding nanostructured Si 7,8 produce better anode performance than Si NWAs in Li-ion batteries because of the features of a lightweight substrate or freestanding structure. The dense substrate could also hinder the mass transfer in the fluid phase when the Si NWAs serve as antibacterial materials or sensors.…”

Hybrid silicon-carbon nanostructured composites as superior anodes for lithium ion batteries

“…Li/Li + [12][13][14][15][16][17][18][19][20]. For instance, Chan et al reported Si nanowires as anode materials and successfully demonstrated an excellent specific capacity of 3124 mA·h/g during the first discharge process [12].…”

Lithium-ion battery anodes of highly dispersed carbon nanotubes, graphene nanoplatelets, and carbon nanofibers

“…The drastic volume change (larger than 300 %) upon lithium alloying/de-alloying reactions with Si commonly causes rapid decrease inreversible capacity and a continuous formation of these-called solidelectrolyte interphase (SEI) as a result of silicon pulverization. Although various advances employing porous silicon, silicon nanoparticles, and silicon coated carbon nanofibers have been investigated, they have shown limited improvements in cycling stability and capacity [13][14][15][16][17][18][19][20][21]. In these materials, a highly conductive porous carbon framework provides a mechanical support for Si nanoparticles and an electrical conducting pathway during the intercalation process of lithium ions.…”