Data on high performance supercapacitors based on mesoporous activated carbon materials with ultrahigh mesopore volume and effective specific surface area

The data presented in this data article are related to the research article entitled “Mesoporous activated carbon materials with ultrahigh mesopore volume and effective specific surface area for high performance supercapacitors” (Lu et al., 2017) [1]. The detailed structure data of the prepared mesoporous activated carbon materials with ultrahigh mesopore volume and effective specific surface area and the electrochemical performance data of the corresponding supercapacitors are described.

entific analysis of the microstructure of carbon materials, and helpful for material design and optimization.
The calculation method for effective specific surface area and theoretical capacitance could be used to evaluate reliably the material's performance used for double layer electrochemical capacitor without fabricating real and industry standard devices.
Electrochemical performance data of other materials including the reference material than the optimal material can be used to compare together and used for the optimization of material design.

Data
In this data article, the detailed structure and electrochemical data of the prepared mesoporous activated carbon materials (AC-KOH) and the control samples are presented. The data include the surface element composition (Table 1), pore size distribution (PSD) curves (Fig. 1), the calculation method of the effective specific surface (E-SSA) ( Table 2), the electrochemical performance data in organic (TEABF 4 /AN), aqueous (KOH) and ion liquid (EMIMBF 4 ) electrolyte systems (Figs. [2][3][4][5]. The photograph and video for lighting a LED using the AC-KOH based supercapacitor are demonstrated (Fig. 6). In addition, the structure and electrochemical data of the optimal material AC-KOH and other reported materials are also summarized (Table 3).

Experimental design, materials and methods
AC-KOH and the control materials (AC-ZnCl 2 , AC-K 2 CO 3 , AC-Na 2 CO 3 , AC-KOH-2:1 and AC-KOH-5:1) were prepared through a hydrothermal carbonization and followed by an activation process using biomass straw as the raw material. A control carbon material, commercial activated carbon YP50, was obtained from Tianjin Plannano Energy Technologies Co., Ltd. The surface element composition of AC-KOH and YP50 was measured through XPS analysis using AXIS HIS 165 spectrometer (Kratos Analytical) with a monochromatized Al Kα X-ray source (1486.71 eV photons). As shown in Table 1, the contents of C and O elements in AC-KOH were estimated as 94.46% and 4.87% respectively, similar to that of commercial YP50. The PSD data of AC-KOH and the control carbon materials were obtained using the Brunauer-Emmett-Teller (BET) analysis and the density functional theory (DFT) method. Based on the PSD data, together with the cumulative DFT SSA and the electrolyte ion size, the E-SSA of electrode material was calculated. The electrochemical performance data, including cyclic voltammetry curves (CV), galvanostatic charge-discharge curves and cycling stability data, was obtained through assembled symmetrical coin-type supercapacitor.
Based on the PSD data of AC-KOH, together with the cumulative DFT SSA and the electrolyte ion size, the E-SSA of electrode material was calculated. The detailed data is shown in Table 2. The data of DFT SSA was obtained from the BET analysis directly. For TEABF 4 /AN electrolyte, the solvent free/bare TEA þ ion (diameter of 0.684 nm) and solvated TEA þ ion (diameter of 1.32 nm) were used for the E-SSA calculation [2,3]. When the pore width of the carbon material is larger than 0.684 nm but smaller than 1.32 nm, the size of bare TEA þ ion was used for the calculation. While when the pore width of the carbon material is larger than 1.32 nm, the size of solvated TEA þ ion was used for such calculation. These two parts were then added together as the total accessible SSA for the electrolyte ions and are regarded as the E-SSA, which is 1771 m 2 g -1 for AC-KOH electrode material as an example.       The capacitance performance of AC-KOH and YP50 was measured through two electrode system (coin-type supercapacitor). Fig. 2 shows the specific capacitance of the capacitors at different current density. In the TEABF 4 /AN electrolyte system, the specific capacitance of AC-KOH based capacitor is 206, 202 and 198 F g -1 at 0.5, 1 and 2 A g -1 , respectively. Accordingly, YP50 based capacitor shows 101, 100 and 100 F g -1 at 0.5, 1 and 2 A g -1 , respectively. The galvanostatic charge/discharge curves for AC-KOH based capacitor at current density of 5, 10, 15, 20 and 30 A g -1 are presented in Fig. 3.
The CV curves, galvanostatic charge/discharge curves, rate performances and Nyquist plots of AC-KOH electrode material in 6 M KOH electrolyte are shown in Fig. 4. The CVs (Fig. 4a) were measured in the voltage range of 0−1.0 V at the scan rates of 5, 10 and 20 mV s -1 . The galvanostatic charge/discharge curves at different current densities are presented in Fig. 4b. The capacitance of AC-KOH of YP50 at current density of 0.1 A g -1 is 260 and 132 F g -1 , respectively. The specific capacitance of AC-KOH is 216 F g -1 at current density of 2 A g -1 (Fig. 4c). The charge transfer resistance and ion diffusion performance were evaluated by the electrochemical impedance spectroscopy (EIS) measurements at a frequency range of 100 kHz to 10 mHz, as shown in Fig. 4d.
The galvanostatic charge/discharge curves for AC-KOH and YP50 based supercapacitors in EMIMBF 4 electrolyte system tested at current density of 1 A g -1 are presented in Fig. 5. According to these curves, the capacitance of AC-KOH and YP50 based supercapacitors was calculated, which is 188 and 120 F g -1 , respectively. The energy density of AC-KOH device, calculated using the formula E cell ¼ C p V 2 /8 (where C p (F g -1 ) is the specific capacitance of the device and V (V) is the voltage), is 80 W h kg -1 at power density of 870 W kg -1 , and the data of YP50 is 51 W h kg -1 at power density of 870 W kg -1 .
The power density, P (W kg -1 ), was calculated according to the formula P ¼ E/Δt (where E (W h kg -1 ) is the energy density of the device and Δt (s) is the discharge time).
The application of an AC-KOH based coin-type supercapacitor cell for lighting a LED is shown in Fig. 6 and the supplementary video. The coin-type supercapacitor was assembled using AC-KOH as the electrode material and ionic liquid (EMIMBF 4 ) as the electrolyte. The device firstly was charged at 1 A g -1 to 3.5 V and then used to light the LED with a working potential around 2.2 V and working power about 40 mW. The LED could maintain light for~30 minutes.
In addition, the structure and capacitive performance data of AC-KOH material in this work and the comparison data with the reported reports are summarized in Table 3, as shown in below.

Transparency document. Supporting information
Supplementary data associated with this article can be found in the online version at http://dx.doi. org/10.1016/j.dib.2018.04.057.  Total pore volume (cm 3 g -1 )