TY - JOUR A1 - Hwang, Jinyeon A1 - Zhang, Wuyong A1 - Youk, Sol A1 - Schutjajew, Konstantin A1 - Oschatz, Martin T1 - Understanding structure-property relationships under experimental conditions for the optimization of lithium-ion capacitor anodes based on all-carbon-composite materials JF - Energy technology : generation, conversion, storage, distribution N2 - The nanoscale combination of a conductive carbon and a carbon-based material with abundant heteroatoms for battery electrodes is a method to overcome the limitation that the latter has high affinity to alkali metal ions but low electronic conductivity. The synthetic protocol and the individual ratios and structures are important aspects influencing the properties of such multifunctional compounds. Their interplay is, herein, investigated by infiltration of a porous ZnO-templated carbon (ZTC) with nitrogen-rich carbon obtained by condensation of hexaazatriphenylene-hexacarbonitrile (HAT-CN) at 550-1000 degrees C. The density of lithiophilic sites can be controlled by HAT-CN content and condensation temperature. Lithium storage properties are significantly improved in comparison with those of the individual compounds and their physical mixtures. Depending on the uniformity of the formed composite, loading ratio and condensation temperature have different influence. Most stable operation at high capacity per used monomer is achieved with a slowly dried composite with an HAT-CN:ZTC mass ratio of 4:1, condensed at 550 degrees C, providing more than 400 mAh g(-1) discharge capacity at 0.1 A g(-1) and a capacity retention of 72% after 100 cycles of operation at 0.5 A g(-1) due to the homogeneity of the composite and high content of lithiophilic sites. KW - anodes KW - hybrid materials KW - nitrogen-doped carbon KW - porous carbon KW - lithium-ion capacitors Y1 - 2021 U6 - https://doi.org/10.1002/ente.202001054 SN - 2194-4296 VL - 9 IS - 3 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Ilic, Ivan A1 - Schutjajew, Konstantin A1 - Zhang, Wuyong A1 - Oschatz, Martin T1 - Changes of porosity of hard carbons during mechanical treatment and the relevance for sodium-ion anodes JF - Carbon : an international journal sponsored by the American Carbon Society N2 - Lithium-ion batteries have revolutionized battery technology. However, the scarcity of lithium in nature is driving the search for alternatives. For that reason, sodium-ion batteries have attracted increasing attention in recent years. The main obstacle to their development is the anode as, unlike for lithium-ion batteries, graphite cannot be used due to the inability to form stoichiometrically useful intercalation compounds with sodium. A promising candidate for sodium storage is hard carbon a form of nongraphitisable carbon, that can be synthesized from various precursor materials. Processing of hard carbons is often done by using mechanochemical treatments. Although it is generally accepted and often observed that they can influence the porosity of hard carbons, their effect on battery performance not well understood. Here, the changes in porosity occurring during ball milling are elucidated and related to the properties of hard carbons in sodium storage. Analysis by combined gas physisorption and small angle X-ray scattering shows that porosity changes during ball milling with a significant increase of the open porosity, unsuitable for reversible sodium storage, and decrease of the closed porosity, suitable for reversible sodium storage. While pristine hard carbon can store 58.5 mAh g(-1) in the closed pores, upon 5 h of mechanical treatment in a ball mill it can only store 35.5 mAh g(-1). The obtained results are furthermore pointing towards the disputed "intercalation-adsorption" mechanism. KW - Hard carbons KW - Sodium-ion batteries KW - Anodes KW - Microporosity KW - Ball milling Y1 - 2022 U6 - https://doi.org/10.1016/j.carbon.2021.09.063 SN - 0008-6223 SN - 1873-3891 VL - 186 SP - 55 EP - 63 PB - Elsevier Science CY - Amsterdam [u.a.] ER -