File Name : figure s01.tiff Caption : schematic setup for magnesiothermic reduction of silicanq using (a) an alumina boat and (b) a cylindrical graphite crucible. File Name : figure s02.tiff Caption : gas physisorption measurements of nano-quill materials in this study; (a), (c), and (e) show adsorption-desorption isotherms, and (b), (d), and (f) illustrate pore size distributions. the bet method was used to estimate the specific surface area of materials. the total pore volume and pore size distribution of materials were evaluated by the bjh method. File Name : figure s03.tiff Caption : (a) ftir and (b) raman spectra of sinq-g and c-si materials. characteristic peaks show the presence of surface functional groups for sinq-g, which are absent for c-si. (c) zeta potential results of as-sonicated sinq-g and c-si powders in di water. dispersion of sinq-g and c-si in di water using magnetic stirring and probe ultrasonication methods shows that (d) c-si cannot be dispersed by stirring, while (e) sinq-g is easily dispersed after stirring for a short period. probe sonication of (f) c-si results in a partial dispersion (remaining c-si float on top of the water), but (g) sinq-g is uniformly dispersed in water after a few seconds of probe sonication. after one week, (h) as-sonicated c-si gets separated entirely, and (i) sinq-g suspension remains stable. File Name : figure s04.tiff Caption : s-tem elemental mapping of nano-quill materials in this study. the elemental maps related to si, o, and c are illustrated here. the carbon maps are from the lacey carbon structure from the tem grid. File Name : figure s05.tiff Caption : atomic concentration of different si-containing species in sinq-a and sinq-g materials as a function of xps etch time. File Name : figure s06.tiff Caption : (a) s-tem micrograph of hf-etched sinq-a, and (b) corresponding elemental maps for si (yellow) and c (red). the o-containing species are removed from the structure by acid treatment of the as-reduced product using hf. (c) electrochemical cycling results of anodes prepared using sinq-a (hcl etched) vs. sinq-a-hf (hcl and hf etched) active material. the electrodes were prepared by casting a slurry of each active material onto a conductive bucky paper current collector. half cells were assembled and cycled between 1.0 v and 0.01 v at 0.1c (1c = 4200 ma g-1). the delivered capacity was normalized by the mass of active material. (d) s-tem micrograph and corresponding elemental maps of sinq-a anode after 150 cycles, and (e) s-tem micrograph and corresponding elemental maps of sinq-a-hf anode after 150 cycles. it is evident that hcl-treated sinq maintained its 1d morphology after cycling. File Name : figure s07.tiff Caption : cyclic voltammetry of 17% c-si/mcmb and 17% sinq-g/mcmb anodes. the anodic scan at 0.1 mv s-1 is characterized by graphite delithiation peak at around 2.5-3.0 v and silicon delithiation peak at around 0.5 v. these two peaks are evolving at higher scan rates, with different behaviors for c-si and sinq-g. File Name : figure s08.tiff Caption : schematic representation of (a) sinq-g, (b) mcmb, and (c) c-si particles. particle sizes are not to scale. File Name : figure s09.tiff Caption : charge-discharge profile of anode half cells with an active material comprising (a) 17% sinq-g/mcmb, (b) 17% sinq-a/mcmb, (c) pure mcmb graphite, (d) 17% c-si/mcmb, and (d) their corresponding coulombic efficiency for the first 20 cycles. File Name : figure s10.tiff Caption : differential capacity plots corresponding to the formation, 1st, 2nd, 3rd, 100th, and 200th cycles for all studied anodes. the characteristic peaks and their shift over cycling are marked in anodic and cathodic curves. File Name : figure s11.tiff Caption : electrochemical impedance spectroscopy results; nyquist plots of (a) 17% c-si/mcmb and (b) 17% sinq-g/mcmb electrodes after cycles 5 and 25. the equivalent randles circuit used for modeling the eis spectra is presented in (c) as an example of an experimental and simulated nyquist plot. impedance values derived from fitting models are plotted in (d). File Name : figure s12.tiff Caption : electrochemical cycling of 17% sinq-g/mcmb electrodes at high current densities. (a) discharging at 0.1c and charging at 2c, and (b) discharging at 2c and charging at 0.1c. half cells were cycled between 1.5 v and 0.005 v (1c = 900 ma g-1). the formation cycle was performed at 0.05c. File Name : figure s13.tiff Caption : initial charge-discharge profiles for 17% sinq-g/mcmb anodes pre-lithiated for different durations.