# Novel Q-Carbon Anodes for Sodium-Ion Batteries
## 2 Materials and Methods  
Q1 and Q2 are mixtures of Q-carbon (nanoscale) and graphite (microscale) powders, one formed by pulsed laser deposition (PLD) and another by cathodic arc deposition. The pulsed laser deposition for Q1 uses a graphite sputtering target and vacuum are discharge; Q2 uses a graphite electrode. In the PLD system, the target was a graphite target formed from fine graphite powders. There was a slow and constant flow of argon gas. A Krf excimer laser (248 nm, 25 ns pulse duration) was focused to a laser density of 3.5 J\(\cdot\)cm\({}^{-2}\) on the carbon target. After ablation, carbon atoms were generated by ablation and were gathered on a metal collector at a water-cooled metal surface in the end of a tube. In the cathodic arc deposition system, the carbon plasma with carbon liquid droplets was generated by a vacuum arc discharge on a carbon cathode with an arc current of 200 A, arc duration of 5 ms, and arc repetition of 1 Hz. The ion current density on the substrate was 10-50 mA\(\cdot\)cm\({}^{-2}\). The substrate was biased to negative 2.5 kV with a pulse duration of about one microsecond. The nanoscale liquid droplets resulted in the formation of Q-carbon powder of 10-20 nm, whereas microscale liquid droplets led to the formation of graphite on the substrate. This nanoscale Q-carbon on graphite sheets was ground to produce a mixture of nanoscale Q-carbon and microscale graphite. The composite powders were vacuum dried at 110 \({}^{\circ}\)C overnight before being used. Powder X-ray diffraction (XRD) patterns were collected on a Rigaku SmartLab X-ray diffractometer (Tokyo, Japan) with Cu-K\(\alpha\) radiation and a wavelength of 1.54 A at an operation voltage of 40 kV and a current of 25 mA. The N\({}_{2}\) adsorption isotherms were measured at 77 K with a Micromerities 3 Flex instrument (Norcross, GA, USA). The samples were degassed at 120 \({}^{\circ}\)C for 10 h before the measurements. The Brunauer-Emmett-Teller (BET) surface area, t-plot pore volume, and Barrett-Joyner-Halenda (BJH) desorption mesopore volume were calculated using MicroActive V6.00 software. Dynamic light scattering measurements were performed using a Zetasizer Ultra by Malvern Panalytical Ltd. (Malvern, United Kingdom) with a 633 nm He-Ne laser operating at 10 mW. Raman spectra were collected with a WITec confocal Raman microscope (Ulm, Germany) system using an excitation wavelength of 532 nm and an 1800 I\(\cdot\)mm\({}^{-1}\) grating. A FEI Verios 460L scanning electron microscope (SEM) (Hillsboro, OR, USA) operated at 3 kV was used to characterize the surface morphologies of the samples. XPS data were collected with a Thermo-Fisher K-alpha XPS (Waltham, MA, USA) with a monochromatic Al-K\({}_{\alpha}\), a 1486.6 eV source, 400 mm spot, and an argon ion flood gun. Precautions were taken to avoid any air and moisture exposure to the samples. An XPS vacuum chamber in an argon atmosphere was used to handle all samples. All samples were washed with anhydrous DMC bath and dried overnight under vacuum (in the antechamber of a glovebox) before being placed in the XPS vacuum chamber. Q-carbon powder was mixed with C45 (carbon black: CB) and PVdF in NMP in a weight ratio of 80:10:10 (Q-carbon: CB: PVdF) to form a homogenized slurry, followed by casting onto an Al foil using a doctor blade. The electrode sheet was first dried under UV light until the solvent (NMP) evaporated, followed by drying in a vacuum oven at 110 \({}^{\circ}\)C overnight. The electrode sheet was punched into circular discs with an area of 1.27 cm\({}^{2}\). The electrodes had an active material loading of approximately 2 mg\(\cdot\)cm\({}^{-2}\). Half-cell coin cells were assembled in an argon-filled glovebox with Na metal foil as the negative electrode, a Q-carbon disc as the positive electrode, and a Celgard 2320 as the separator. The electrolyte used is 1.2 M NaPF6 dissolved in a 3:7 weight ratio of ethylene carbonate (EC) and ethyl methyl carbonate (EMC).