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    Mechanistic insights into cathode-driven capacity degradation of NMC111/ graphite pouch cells under long-term cycling
    (Pergamon-Elsevier Science Ltd, 2025) Ates, Mehmet Nurullah; Zengin, Feyza; Whba, Rawdah; Tunaboylu, Bahadir; Aydemir, Umut; Peighambardoust, Naeimeh Sadat; Karslioglu, Nergiz Gurbuz
    To investigate long-term degradation, 2000 mAh NMC111/graphite (Gr) pouch cells were cycled 5500 times at a 1C rate. After cycling, the resulting degradation mechanisms were systematically analyzed. Structurally, X-ray diffraction (XRD) peak shifts (003, 108, 110) revealed Jahn-Teller (JT) distortion, evidenced by an increase in the c-lattice parameter. This led to the rise in internal resistance, consistent with scanning electron microscopy (SEM) images that revealed pronounced grain deformation on the cathode. Chemically, ex-situ X-ray absorption near-edge structure (XANES) spectroscopy revealed an increase in the valence states of Mn, Ni, and Co ions, indicating significant bulk changes that could potentially destabilize the oxygen lattice. X-ray absorption fine structure (XAFS) analysis further underscored the key role of weakening transition metal-oxygen (TM-O) bonds in driving this structural deformation. At the surface, X-ray photoelectron spectroscopy (XPS) confirmed the formation of a cathode-electrolyte interphase (CEI) comprising lithium fluoride (LiF), LixPFy, and organic carbonates. The progression of these surface reactions is a key contributor to impedance growth and capacity fade over long-term cycling.
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    Modification of tetrahedrite Cu12Sb4S13 thermoelectric performance via the combined treatment of mechanochemistry and composite formation
    (Elsevier, 2024) Balaz, Peter; Burcak, Arda Baran; Aydemir, Umut; Mikula, Andrzej; Nieroda, Pawel; Balaz, Matej; Findorakova, Lenka
    Tetrahedrite Cu12Sb4S13 with its low thermal conductivity represents a flagship in sulphide thermoelectrics. However, to achieve a reasonable figure-of-merit ZT (measure of thermoelectric efficiency), adequate doping or special sample processing is needed. In this work, a different approach (without doping) is illustrated for the two tetrahedrite-containing systems. In the First approach binary composite tetrahedrite Cu12Sb4S13/chalcopyrite CuFeS2 was prepared by mechanochemical leaching with the aim to obtain partly decomposed tetrahedrite. In this approach, the alkaline leaching medium (Na2S + NaOH) was applied to extract Sb from tetrahedrite thus changing its composition. The obtained composite (formed from its own phases in an intrinsic mode) shows low values of ZT = 0.0022@673 K in comparison with the non-treated tetrahedrite where ZT was 0.0090@673 K. In this case the extremely high electric resistivity (6-20 m Omega cm-1) was documented. In the second approach binary composite tetrahedrite Cu12Sb4S13/muscovite KAl2(AlSi3O10)(OH)2 (formed from its own and foreign phases in an extrinsic mode) was prepared by two-step mechanical activation in which combined treatment of industrial vibratory milling and subsequent laboratory planetary milling was applied. The addition of a foreign phase, muscovite, did not give extraordinary thermoelectric performance results. However, the two-step milling process (without the addition of foreign phase) gives the value of ZT = 0.752@673 K which belongs to the highest in the tetrahedrite thermoelectric community. In this case, the two-times increase in specific surface area and the increased amount of tetrahedrite in comparison to famatinite are suspectable for this effect. Both applied nontraditional approaches to synthesize tetrahedrite composites form a platform for potential modification of its thermoelectric performance.
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    Novel Electrochemical Approaches for Anticancer Drug Monitoring: Application of CoS@Nitrogen-Doped Amorphous Porous Carbon Composite in Nilotinib Detection
    (Amer Chemical Soc, 2024) Yildir, Merve; Genc, Asena Ayse; Bugday, Nesrin; Erk, Nevin; Peighambardoust, Naeimeh Sadat; Aydemir, Umut; Yasar, Sedat
    A novel composite containing CoS and nitrogen-doped amorphous porous carbon (NAPC), denoted as CoS@NAPC, was successfully synthesized from a mixture of cobalt-based ZIF-12 and sulfur through one-pot pyrolysis. The morphology and microstructure of the composites are evaluated with appropriate spectroscopic techniques. CoS@NAPC was used to modify the glassy carbon electrode (GCE) to detect Nilotinib. Under optimized conditions, the GCE electrode modified with CoS@NAPC showed a low limit of detection (LOD) of 11.8 ng/mL and two wide linear concentration ranges of 59.7-1570 and 1570-11200 ng/mL for the determination of Nilotinib. GCE electrode modified with CoS@NAPC has excellent recoveries ranging from 98.41 to 102.03% for real samples, demonstrating its superior analytical performance. The enhanced performance of CoS@NAPC as an electrochemical sensor may stem from the combined action of two key components: CoS, known for its potent reactivity toward Nilotinib, and NAPC, which offers a consistent conductive carbon matrix. CoS contributes to its reactivity, while NAPC facilitates electron transfer during Nilotinib detection. This synergistic effect likely underlies the superior sensor performance observed.