PDF Publication Title:
Text from PDF Page: 009
Page 13 of 17 ACS Applied Materials & Interfaces cathode) comprising ZTC as the cathode are also shown.55 Comparatively, KFSI DIBs based on ZTC represent a signifi‐ cant improvement in both specific energy and power. This im‐ provement is also extended to volumetric energy and power densities, whose values depend significantly on the maximum packing density of the porous ZTC cathode. This stark im‐ provement over AlCl3‐based ABs is primarily a consequence of the high electrolyte concentrations accessible to KFSI in EC/DMC solvent (up to 4.8 M in this work) and the much higher operational voltage (3.0‐3.5 V vs. K/K+ in KFSI DIBs as compared to 1.05 V vs. Al/Al3+ in ABs). Furthermore, the range of estimated full‐cell energy and power densities in ABs is much larger since the precise mechanism of charge storage remains unknown, and enacts a significant difference to the amount of electrolyte required for operation. By contrast, the average operational voltage of ZTC‐based KFSI DIBs is slightly lower than that of analogous cells based on graphite as the cathode (4.7 V);64 this is consistent with the pattern already reported for ABs based on ZTC and graph‐ ite.14, 18, 55 Therefore, despite exhibiting a higher charge capac‐ ity, ZTC‐based DIBs and ABs garner lower overall energy den‐ sities (a factor that is indeed assisted by the subsequent re‐ quirement for less total electrolyte owing to a lower quantity of exchanged ions during cycling). However, ZTC‐based DIBs and ABs compensate for this lower energy density by exhibit‐ ing significantly higher rate capability and, therefore, power density, similarly to recently emerging devices commonly re‐ ferred to as hybrid capacitors.69 Overall, KFSI DIBs based on a ZTC cathode have comparable energy density (176 Wh kg‐1, 79.8 Wh L‐1) to analogous graphite cells and much higher power density (3945 W kg‐1 and 1095 W L‐1). A comparison of gravimetric energy and power densities of ZTC‐based KFSI DIBs to similar batteries comprising other porous materials such as MOFs and macroporous graphitic foam is shown in Figure 5. A hurdle facing all DIBs and ABs employing microporous, high surface area materials as the cathode is the sloping volt‐ age profile with no apparent plateaux, culminating in a vary‐ ing discharge potential of the prepared cell. Such a charge‐ storage mechanism is typical of capacitive electrode materi‐ als, even including highly ordered MOFs that contain crystal‐ lographically distinct redox‐active sites within their pores (e.g., at the open iron coordination centers in Fe2(dobpdc)). This seems to imply that improving the regularity of the ZTC framework will not likely lead to a dramatic change in the shape of the voltage profile for large anion storage; rather, a sensible choice of insertion anion could instead lead to a higher and flatter voltage profile. In several recent methodo‐ logical studies, for example, it has been reported that larger anions lead to higher average insertion/intercalation voltages in both porous DIB cathodes33 and graphite,70 although size‐ related effects in anion intercalation in graphite are also known to be complexly related to other electrolyte effects, such as ion‐pair formation and self‐aggregation.41 Future work remains to methodologically assess anion‐size effects in ZTC‐based DIBs and further establish electrolyte/solvent mixtures that will lead to higher energy and power densities yet. CONCLUSIONS Zeolite‐templated carbon, an exclusively microporous, or‐ dered carbon‐based framework material, was demonstrated to reversibly oxidize and reduce between 2.65‐4.7 V vs. K/K+ and concomitantly undergo insertion and de‐insertion of FSI‐ anions, respectively. This reaction permits ZTC to be em‐ ployed as the cathode material in high energy density KFSI dual‐ion battery (DIB) cells, which are found to be compara‐ ble to state‐of‐the‐art lithium‐ion batteries despite being comprised of only highly abundant elements (C, K, N, S, O, and F). Full‐cells based on a ZTC cathode and electroplating/strip‐ ping of potassium metal at the anode demonstrate high volu‐ metric and gravimetric capacities (up to 176 Wh kg‐1 and 79.8 Wh L‐1, respectively) after hundreds of cycles. The corre‐ sponding full‐cell power densities (up to 3945 W kg‐1 and 1095 W L‐1) remain much higher than those of equivalent cells based on graphite, where anion insertion/de‐insertion is sig‐ nificantly slower than within the ~1.2 nm micropores of ZTC. Furthermore, both the energy and power densities of KFSI DIBs are significantly improved over analogous aluminum batteries owing to a much higher stable average voltage of op‐ eration (3.0‐3.5 V vs. K/K+) and high‐concentration of electro‐ lyte employed. The insertion of both solvent and FSI‐ anions within the pores of ZTC was evidenced by solid‐state NMR spectroscopy studies. In future work, zeolite‐templated car‐ bon is also likely to be an excellent model material for eluci‐ dating the mechanism of conductance of ions (and the extent to which they remain solvated or unsolvated) in nanometer‐ scale pore spaces, a topic that remains poorly understood but which is crucial for the optimization of myriad electrochemi‐ cal energy storage devices, ranging from supercapacitors to dual‐ion batteries. EXPERIMENTAL SECTION Materials Synthesis. Pristine ZTC was prepared according to the established two‐step method62, 71 via liquid impregna‐ tion of zeolite NaY with furfuryl alcohol at room temperature and then chemical vapor deposition of propylene at 700 °C; the zeolite template was removed upon repeated dissolution in aqueous HF. For comparison, two mesoporous templated carbons with larger characteristic pore sizes (MTC21 and MTC31) were also prepared by similar methods from MSU‐H, an ordered mesoporous silica template. The synthesis meth‐ ods are described in detail in the Supporting Information. Materials Characterization. Powder X‐ray diffraction (XRD) measurements were performed on a Rigaku Ultima IV diffractometer using Cu Kα1 radiation (λ = 1.54 Å) in reflection geometry. Nitrogen adsorption/desorption isotherms were measured at 77 K between 10‐4‐100 kPa using an automated volumetric instrument (3Flex, Micromeritics Instrument Corp.). Specific surface areas were calculated by the Brunauer‐Emmett‐Teller (BET) method between P/P0 = 0.008‐0.12 and micropore volumes were calculated by the Dubinin‐Radushkevich (DR) method.72 Pore‐size distribu‐ tions were determined by non‐localized density functional theory (NLDFT) calculations using a dedicated software pack‐ age (MicroActive Share, Micromeritics Instrument Corp.), with a carbon slit‐pore model. Transmission electron micros‐ copy (TEM) was performed using a Jeol2200FS microscope operated at 200 kV equipped with an in‐column Omega‐type filter. In order to improve the image contrast, the TEM images 8 ACS Paragon Plus EnvironmentPDF Image | Zeolite-Templated Carbon as the Cathode
PDF Search Title:
Zeolite-Templated Carbon as the CathodeOriginal File Name Searched:
Stadie_ACSAMI_2019_FINAL.pdfDIY PDF Search: Google It | Yahoo | Bing
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
Heat Pumps CO2 ORC Heat Pump System Platform More Info
| CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com | RSS | AMP |