# CNT-Coated Quartz Woven Fabric Electrodes for Robust Lithium-ion Structural Batteries
## 3 Results and Discussion  
### Material Synthesis  
In case of using a quartz woven fabric, as a substrate, the important factors determining the energy efficiency of CNTs are to ensure uniformity of the distribution of CNTs grown on the fabric surface, mitigation of mutual interference through uniform vertical growth, and uniformity of height. CNTs, which were grown on the fabric substrate using the previous synthetic method, had inhomogeneous height because of the unevenness of the fabric surface, causing a problem of crossing with each other. In addition, as long-grown CNTs bend after growth, they become entangled or become a complex network structure. The morphology becomes an important factor affecting electrochemical performance when CNTs were used as an electrode material. Therefore, in this study, we studied a special method in which high-yield CNT can be grown vertically to an appropriate length that can minimize bending and deformation after growth via PECVD. Table 1 shows physical and mechanical properties of silica glass fibers in quartz woven fabric. By changing the deposition of Al and Fe nanoparticles as a metal catalyst layer before CNTs were grown, we tried to confirm the possibility of improving the distribution of CNT forest and increasing the growth yield compared to pristine QWF (P-QWF). For electrode synthesis, a nanostructured electrode was fabricated via e-beam evaporator and PECVD. The fabrication of CNT-coated QWF electrode (C-QWF), was carried out in two sequential steps, inside and outside the CVD chamber. First, to fabricate nanostructured electrodes on fabric substrates, metal nanoparticles were deposited as a catalyst on a fabric substrate through a pre-treatment process using an e-beam evaporator before the plasma CVD process. For effective carbon nanotube growth, Fe and Al nanoparticles were deposited with a diameter within 1-10 nm. In the process of growing CNT on the fabric electrode, the reason for considering the metal catalyst is to increase the in-plane electrical conductivity when CNTs were grown in a vertical direction on the surface of QWF. Furthermore, this CNT structure not only has a role to overcome the low electrical conductivity of QWF but also can store the considerable lithium ions because of their large surface area. In order to investigate the crystal structure of the QWF series, XRD was executed from 10 to 70\({}^{\circ}\) as shown in Figure 1a. The XRD peak of both QWF electrodes can be broadly indexed as amorphous silica, detected at 2\(\theta\) = 20.63\({}^{\circ}\), and as crystalline silica, which is detected at 2\(\theta\) = 22.82\({}^{\circ}\). The Raman spectra of the QWF electrodes confirm several shifts in the low wavenumber range from 100 to 700 cm\({}^{-1}\), related to amorphous silica. It was confirmed that the crystalline SiO\({}_{2}\) peak was observed in C-QWF \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Filament** & **Specific** & **Tensile** & **Tensile** & **CTE** & **Thermal** & **Thermal** \\
**Diameter** & **Gravity** & **Strength** & **Modulus** & **Stability** & **Conductivity** \\ \hline \(\mu\)m & g cc\({}^{-1}\) & GPa & GPa & m/(m\({}^{\circ}\)C) & \({}^{\circ}\)C & W/(m-K) \\ \hline
9.0 & 2.2 & 3.4 & 69 & 5.4 \({}^{*}\) 10\({}^{-7}\) & 1200 & 0.0033 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The material properties of silica glass fibers in quartz woven fabric. in XRD after heat treatment but disappeared in Raman spectra, as seen in Figure 1b. The change of Raman peak according to the heat treatment of SiO\({}_{2}\) is due to the difference in crystallinity according to the temperature of the silica, and it is also proof that the initial amorphous silica was crystallized by the heat treatment as CNTs grew.