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KFSI DIBs based on ZTC as the cathode were found herein to exhibit a high reversible specific gravimetric capacity (up to 141 mAh g‐1) even at high current rates, over hundreds of cy‐ cles. Importantly, the average voltage was found to be 3.0‐3.5 V vs. K/K+ (depending on the current rate), leading to very high specific energy densities (up to 485 Wh kg‐1) and power densities (up to 5785 W kg‐1) for the ZTC itself as a bare cath‐ ode. In full‐cells, DIBs employing ZTC as the cathode are esti‐ mated to achieve values of 176 Wh kg‐1 and 3945 W kg‐1 under the conditions investigated herein, which compare favorably to state‐of‐the‐art LIBs. As in previous work exploring both microporous carbons55 and other carbon‐based materials16, 29, 59‐61 as electrodes in aluminum batteries (ABs) , the irreversi‐ ble capacity loss associated with formation of SEI in the first several charge/discharge cycles was greatly mitigated. Unlike past work, on the other hand, significantly higher energy and power densities could be achieved in ZTC‐based KFSI DIBs, owing to a much higher operating voltage and a higher con‐ centration of electrolyte in the cell. This work lays a founda‐ tion for further pursuits of electrode/electrolyte combina‐ tions that provide stable, high‐voltage operation by anion in‐ sertion within the microporous networks of high surface area carbonaceous materials such as ZTC. RESULTS AND DISCUSSION Synthesis of ZTC. The faujasite variant of zeolite‐templated carbon (FAU‐ZTC) was synthesized by the well‐established two‐step method, comprising the liquid‐phase impregnation of a Y‐type zeolite with furfuryl alcohol and gas‐phase impreg‐ nation of propylene. The chemical vapor deposition (CVD) (high surface area and pore‐to‐pore regularity and minimal graphitic content) based on previous results.55 Heat treat‐ ment at 900 °C to anneal the underlying carbon framework was followed by cooling and dissolution in aqueous HF to free the final ZTC product. Detailed synthetic methods are given in the Supporting Information. Materials Characterization. The high template‐fidelity na‐ ture of the FAU‐ZTC structure (and hence high surface area and pore regularity) was evidenced by X‐ray powder diffrac‐ tion (XRD), nitrogen adsorption, and electron microscopy (see Figure 2). The intense XRD reflection centered at 2θ = 6.5° (d‐spacing = 1.36 nm) indicates the high pore‐to‐pore regularity of FAU‐ZTC inherited from the zeolite NaY tem‐ plate, while the absence of higher order peaks is indicative of its generally amorphous local atomic structure (Figure 2a).62 Pore‐to‐pore regularity was also clearly observed in trans‐ mission electron microscopy (TEM) investigations, with peri‐ odic contrast patterns parallel to the ZTC particle edges exhib‐ iting an average spacing of ~1.4 nm (Figures 2c‐2d, Figures S2‐S3). Scanning electron microscopy (SEM) studies at lower magnification confirm that the size and shape of the ZTC par‐ ticles are identical to the microcrystalline zeolite NaY tem‐ plate (see Figure S1). Nitrogen adsorption/desorption isotherms at 77 K confirm the exclusively microporous structure and high surface area of ZTC (Figure 2b). The isotherms exhibit a pronounced knee at P/P0 = ~0.12, a relatively flat adsorption uptake plateau be‐ tween 780‐920 mLSTP g‐1, and no apparent adsorption/ de‐ sorption hysteresis, all indicative of exclusively microporous structure. conditions employed for propylene insertion and pyrolysis within the zeolite were optimized for high template fidelity ACS Applied Materials & Interfaces Page 8 of 17 Figure 2. Structure of Zeolite‐Templated Carbon (ZTC). (a) X‐ray diffraction (XRD) pattern of ZTC (black) compared to that of the native zeolite template (red) and the calculated FAU zeolite crystal structure (purple). (b) Equilibrium N2 adsorption/desorption isotherms at 77 K of ZTC (black) compared to its template (red) and corresponding non‐local density functional theory (NLDFT) pore‐size distributions compared to the theoretical diameter of the theoretical FAU 12‐ring pore openings (purple dashed). (c) Zero‐ loss filtered transmission electron micrograph of a ZTC particle revealing the long‐range pore ordering. The pores are aligned per‐ pendicular to the image plane and oriented perpendicular to the particle edge as confirmed by (d) the corresponding Fourier trans‐ form image. 3 ACS Paragon Plus EnvironmentPDF Image | Zeolite-Templated Carbon as the Cathode
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