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- ItemMXene as a novel intercalation-type pseudocapacitive cathode and anode for capacitive deionization(London [u.a.] : RSC, 2016) Srimuk, Pattarachai; Kaasik, Friedrich; Krüner, Benjamin; Tolosa, Aura; Fleischmann, Simon; Jäckel, Nicolas; Tekeli, Mehmet C.; Aslan, Mesut; Suss, Matthew E.; Presser, VolkerIn this proof-of-concept study, we introduce and demonstrate MXene as a novel type of intercalation electrode for desalination via capacitive deionization (CDI). Traditional CDI cells employ nanoporous carbon electrodes with significant pore volume to achieve a large desalination capacity via ion electrosorption. By contrast, MXene stores charge by ion intercalation between the sheets of its two-dimensional nanolamellar structure. By this virtue, it behaves as an ideal pseudocapacitor, that is, showing capacitive electric response while intercalating both anions and cations. We synthesized Ti3C2-MXene by the conventional process of etching ternary titanium aluminum carbide i.e., the MAX phase (Ti3AlC2) with hydrofluoric acid. The MXene material was cast directly onto the porous separator of the CDI cell without added binder, and exhibited very stable performance over 30 CDI cycles with an average salt adsorption capacity of 13 ± 2 mg g−1.
- ItemHow to speed up ion transport in nanopores([London] : Nature Publishing Group UK, 2020) Breitsprecher, Konrad; Janssen, Mathijs; Srimuk, Pattarachai; Mehdi, B. Layla; Presser, Volker; Holm, Christian; Kondrat, SvyatoslavElectrolyte-filled subnanometre pores exhibit exciting physics and play an increasingly important role in science and technology. In supercapacitors, for instance, ultranarrow pores provide excellent capacitive characteristics. However, ions experience difficulties in entering and leaving such pores, which slows down charging and discharging processes. In an earlier work we showed for a simple model that a slow voltage sweep charges ultranarrow pores quicker than an abrupt voltage step. A slowly applied voltage avoids ionic clogging and co-ion trapping—a problem known to occur when the applied potential is varied too quickly—causing sluggish dynamics. Herein, we verify this finding experimentally. Guided by theoretical considerations, we also develop a non-linear voltage sweep and demonstrate, with molecular dynamics simulations, that it can charge a nanopore even faster than the corresponding optimized linear sweep. For discharging we find, with simulations and in experiments, that if we reverse the applied potential and then sweep it to zero, the pores lose their charge much quicker than they do for a short-circuited discharge over their internal resistance. Our findings open up opportunities to greatly accelerate charging and discharging of subnanometre pores without compromising the capacitive characteristics, improving their importance for energy storage, capacitive deionization, and electrochemical heat harvesting.
- ItemHybrid Anodes of Lithium Titanium Oxide and Carbon Onions for Lithium‐Ion and Sodium‐Ion Energy Storage(Hoboken, NJ : Wiley, 2020) Shim, Hwirim; Arnold, Stefanie; Budak, Öznil; Ulbricht, Maike; Srimuk, Pattarachai; Presser, VolkerThis study demonstrates the hybridization of Li4Ti5O12 (LTO) with different types of carbon onions synthesized from nanodiamonds. The carbon onions mixed with a Li4Ti5Ox precursor for sol–gel synthesis. These hybrid materials are tested as anodes for both lithium‐ion battery (LIB) and sodium‐ion battery (SIB). Electrochemical characterization for LIB application is carried out using 1 m LiPF6 in a 1:1 (by volume) ethylene carbonate and dimethyl carbonate as the electrolyte. For lithium‐ion intercalation, LTO hybridized with carbon onions from the inert‐gas route achieves an excellent electrochemical performance of 188 mAh g−1 at 10 mA g−1, which maintains 100 mAh g−1 at 1 A g−1 and has a cycling stability of 96% of initial capacity after 400 cycles, thereby outperforming both neat LTO and LTO with onions obtained via vacuum treatment. The performance of the best‐performing hybrid material (LTO with carbon onions from argon annealing) in an SIB is tested, using 1 m NaClO4 in ethylene/dimethyl/fluoroethylene carbonate (19:19:2 by mass) as the electrolyte. A maximum capacity of 102 mAh g−1 for the SIB system is obtained, with a capacity retention of 96% after 500 cycles.
- ItemTitanium Niobium Oxide Ti2 Nb10 O29 /Carbon Hybrid Electrodes Derived by Mechanochemically Synthesized Carbide for High-Performance Lithium-Ion Batteries(Weinheim : Wiley-VCH, 2021) Budak, Öznil; Srimuk, Pattarachai; Aslan, Mesut; Shim, Hwirim; Borchardt, Lars; Presser, VolkerThis work introduces the facile and scalable two-step synthesis of Ti2 Nb10 O29 (TNO)/carbon hybrid material as a promising anode for lithium-ion batteries (LIBs). The first step consisted of a mechanically induced self-sustaining reaction via ball-milling at room temperature to produce titanium niobium carbide with a Ti and Nb stoichiometric ratio of 1 to 5. The second step involved the oxidation of as-synthesized titanium niobium carbide to produce TNO. Synthetic air yielded fully oxidized TNO, while annealing in CO2 resulted in TNO/carbon hybrids. The electrochemical performance for the hybrid and non-hybrid electrodes was surveyed in a narrow potential window (1.0-2.5 V vs. Li/Li+ ) and a large potential window (0.05-2.5 V vs. Li/Li+ ). The best hybrid material displayed a specific capacity of 350 mAh g-1 at a rate of 0.01 A g-1 (144 mAh g-1 at 1 A g-1 ) in the large potential window regime. The electrochemical performance of hybrid materials was superior compared to non-hybrid materials for operation within the large potential window. Due to the advantage of carbon in hybrid material, the rate handling was faster than that of the non-hybrid one. The hybrid materials displayed robust cycling stability and maintained ca. 70 % of their initial capacities after 500 cycles. In contrast, only ca. 26 % of the initial capacity was maintained after the first 40 cycles for non-hybrid materials. We also applied our hybrid material as an anode in a full-cell lithium-ion battery by coupling it with commercial LiMn2 O4 .
- ItemHigh performance stability of titania decorated carbon for desalination with capacitive deionization in oxygenated water(London : RSC Publishing, 2016) Srimuk, Pattarachai; Ries, Lucie; Zeiger, Marco; Fleischmann, Simon; Jäckel, Nicolas; Tolosa, Aura; Krüner, Benjamin; Aslan, Mesut; Presser, VolkerPerformance stability in capacitive deionization (CDI) is particularly challenging in systems with a high amount of dissolved oxygen due to rapid oxidation of the carbon anode and peroxide formation. For example, carbon electrodes show a fast performance decay, leading to just 15% of the initial performance after 50 CDI cycles in oxygenated saline solution (5 mM NaCl). We present a novel strategy to overcome this severe limitation by employing nanocarbon particles hybridized with sol–gel-derived titania. In our proof-of-concept study, we demonstrate very stable performance in low molar saline electrolyte (5 mM NaCl) with saturated oxygen for the carbon/metal oxide hybrid (90% of the initial salt adsorption capacity after 100 cycles). The electrochemical analysis using a rotating disk electrode (RDE) confirms the oxygen reduction reaction (ORR) catalytic effect of FW200/TiO2, preventing local peroxide formation by locally modifying the oxygen reduction reaction.
- ItemCarbon onion / sulfur hybrid cathodes via inverse vulcanization for lithium sulfur batteries(Cambridge : Royal Society of Chemistry, 2017) Choudhury, Soumyadip; Srimuk, Pattarachai; Raju, Kumar; Tolosa, Aura; Fleischmann, Simon; Zeiger, Marco; Ozoemena, Kenneth I.; Borchardt, Lars; Presser, VolkerA sulfur–1,3-diisopropenylbenzene copolymer was synthesized by ring-opening radical polymerization and hybridized with carbon onions at different loading levels. The carbon onion mixing was assisted by shear in a two-roll mill to capitalize on the softened state of the copolymer. The sulfur copolymer and the hybrids were thoroughly characterized in structure and chemical composition, and finally tested by electrochemical benchmarking. An enhancement of specific capacity was observed over 140 cycles at higher content of carbon onions in the hybrid electrodes. The copolymer hybrids demonstrate a maximum initial specific capacity of 1150 mA h gsulfur−1 (850 mA h gelectrode−1) and a low decay of capacity to reach 790 mA h gsulfur−1 (585 mA h gelectrode−1) after 140 charge/discharge cycles. All carbon onion/sulfur copolymer hybrid electrodes yielded high chemical stability, stable electrochemical performance superior to conventional melt-infiltrated reference samples having similar sulfur and carbon onion content. The amount of carbon onions embedded in the sulfur copolymer has a strong influence on the specific capacity, as they effectively stabilize the sulfur copolymer and sterically hinder the recombination of sulfur species to the S8 configuration.