Browsing by Author "Bets, Ksenia V."
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Item Battery metal recycling by flash Joule heating(AAAS, 2023) Chen, Weiyin; Chen, Jinhang; Bets, Ksenia V.; Salvatierra, Rodrigo V.; Wyss, Kevin M.; Gao, Guanhui; Choi, Chi Hun; Deng, Bing; Wang, Xin; Li, John Tianci; Kittrell, Carter; La, Nghi; Eddy, Lucas; Scotland, Phelecia; Cheng, Yi; Xu, Shichen; Li, Bowen; Tomson, Mason B.; Han, Yimo; Yakobson, Boris I.; Tour, James M.; Welch Institute for Advanced Materials; NanoCarbon Center; Applied Physics Program; Smalley-Curl InstituteThe staggering accumulation of end-of-life lithium-ion batteries (LIBs) and the growing scarcity of battery metal sources have triggered an urgent call for an effective recycling strategy. However, it is challenging to reclaim these metals with both high efficiency and low environmental footprint. We use here a pulsed dc flash Joule heating (FJH) strategy that heats the black mass, the combined anode and cathode, to >2100 kelvin within seconds, leading to ~1000-fold increase in subsequent leaching kinetics. There are high recovery yields of all the battery metals, regardless of their chemistries, using even diluted acids like 0.01 M HCl, thereby lessening the secondary waste stream. The ultrafast high temperature achieves thermal decomposition of the passivated solid electrolyte interphase and valence state reduction of the hard-to-dissolve metal compounds while mitigating diffusional loss of volatile metals. Life cycle analysis versus present recycling methods shows that FJH significantly reduces the environmental footprint of spent LIB processing while turning it into an economically attractive process.Item Nickel particle–enabled width-controlled growth of bilayer molybdenum disulfide nanoribbons(AAAS, 2021) Li, Xufan; Li, Baichang; Lei, Jincheng; Bets, Ksenia V.; Sang, Xiahan; Okogbue, Emmanuel; Liu, Yang; Unocic, Raymond R.; Yakobson, Boris I.; Hone, James; Harutyunyan, Avetik R.Transition metal dichalcogenides exhibit a variety of electronic behaviors depending on the number of layers and width. Therefore, developing facile methods for their controllable synthesis is of central importance. We found that nickel nanoparticles promote both heterogeneous nucleation of the first layer of molybdenum disulfide and simultaneously catalyzes homoepitaxial tip growth of a second layer via a vapor-liquid-solid (VLS) mechanism, resulting in bilayer nanoribbons with width controlled by the nanoparticle diameter. Simulations further confirm the VLS growth mechanism toward nanoribbons and its orders of magnitude higher growth speed compared to the conventional noncatalytic growth of flakes. Width-dependent Coulomb blockade oscillation observed in the transfer characteristics of the nanoribbons at temperatures up to 60 K evidences the value of this proposed synthesis strategy for future nanoelectronics.Item Single-chirality nanotube synthesis by guided evolutionary selection(AAAS, 2022) Yakobson, Boris I.; Bets, Ksenia V.Bringing to fruition the tantalizing properties, foreseen since the discovery of carbon nanotubes, has been hindered by the challenge to produce a desired helical symmetry type, single chirality. Despite progress in postsynthesis separation or somewhat sporadic success in selective growth, obtaining one chiral type at will remains elusive. The kinetics analysis here shows how a local yet moving reaction zone (the gas feedstock or elevated temperature) can entice the tubes to follow, so that, remotely akin to proverbial Lamarck giraffes, only the fastest survive. Reversing the reaction to dissolution would further eliminate the too fast-reactive types so that a desired chirality is singled out in production.Item Theoretical investigation of dynamic atomistic processes of growth and deformation in carbon nanomaterials(2018-04-20) Bets, Ksenia V.; Yakobson, Boris I.Graphene and carbon nanotubes (CNTs), allotropes of hexagonal sp2-hybridized carbon, were some of the first nanomaterials discovered and had attracted attention since. Current theoretical understanding of the formation processes for those materials mainly relies on thermodynamic principles while kinetics is mostly overlooked. This work proposes a hybrid Kinetic Monte Carlo (KMC) method to represent the kinetic growth of atomically resolved systems of sp2-hybridized carbon at reasonable computational costs. This novel and comprehensive model is used to investigate the growth of grain boundaries (GB) - disordered regions between misoriented grains in polycrystalline graphene. Unlike all previous studies, this work is focused on the dynamic formation of GBs. This model demonstrates a characteristic of the initial configuration that determines the final structure of the GB, resolving a long outstanding discrepancy between theoretical predictions and experimental observations. Additionally, the possibility of asymmetry of graphene GBs is considered. The maximum deviation from symmetry is found not to exceed 12°. More importantly, due to probabilistic nature of GB directions, experimental differentiation between global and local asymmetry was found to be impossible. Extended to three-dimensions and combined with the representation of catalyst particle through Lennard-Jones sphere, the hybrid KMC model presents a computationally efficient simulation method for CNT nucleation. Analysis of collected statistically relevant data (6x104 tubes per parameter set) demonstrated a correlation between catalyst-tube interaction and chiral preference of nucleated CNTs, suggesting possible future routes towards chiral selectivity. Investigating the recent experimental success in chirally selective growth of CNT on the solid Co7W6 catalyst, we discovered energetical preference towards CNT edge with segregated zigzag and armchair facets. This new edge structure mandates growth patterns that lead to defect-induced pooling at observed (12,6) chirality. The KMC simulations predict the (12,6) abundance to be around 90% that closely matches experimental results. Finally, the radial stability of the large diameter single- and double-walled CNT is considered. Using experimental data collected by our collaborators, the critical size of the CNT, beyond which nanotube collapses forming closed-edge graphene nanoribbons, was determined to be 2.8 nm for a single-walled CNT and 4.0 nm for a double-walled CNT.