Browsing by Author "Chen, Weiyin"
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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 Joule heating routes for nanomaterial syntheses and surface modification for nanoscale applications(2022-12-02) Chen, Weiyin; Tour, James M.It is widely known that chemical properties of nanomaterials are structure- and composition-dependent. Through the direct control of synthetic methods and experimental conditions, material-specific features, like constituents, dimensionalities, and arrangement of the atoms within the materials, can be engineered, and the manipulation of desired chemical properties can be achieved. Compared with traditional materials preparation and processing methods, a new electrothermal strategy can achieve selective Joule heating of the reactants to a high temperature (>3000 K) with rapid heating and cooling rates (>104 K s-1), enabling the kinetic control of chemical reactions and the formation of hitherto hard-to-access metastable nanomaterials. To this end, my thesis covers research on direct electrothermal methods to synthesize ~30 different thermodynamically metastable nanomaterials, followed by the exploration of phase transformations and evolution using experiments and simulations. These nanomaterials show new mechanical, optical, and electronic properties, distinct from their more thermodynamically stable counterparts. This thesis begins with the syntheses of carbonaceous nanomaterials using the rapid high temperature electrothermal method. In Chapter 1, 8 different types of heteroatom-doped turbostratic graphene were synthesized and compared with commercial graphite and undoped turbostratic graphene, demonstrating that doped turbostratic graphene had better dispersibility and electrocatalytic oxygen reduction performance. In Chapter 2, the detailed spectroscopic and microscopic studies were provided, related to the formation of fluorinated nanodiamonds and subsequent reaction time-dependent phase evolution to fluorinated graphene and concentric carbon. Non-carbonaceous nanomaterials can also be synthesized or processed, demonstrating the universality of the electrothermal method. The preparation of turbostratic boron nitride, various boron-carbon-nitrogen ternary compounds and 1T-phase transition metal dichalcogenides were illustrated in Chapter 3 and Chapter 4. The rapid Joule heating methods to recycle the anode, cathode, and their mixtures were further discussed in Chapters 5-7. In addition, the utilization of above nanomaterials as the additives to fabricate the coating for modifying the surface wettability was demonstrated in Chapter 8. The artificial coating of the reactive metals and current collectors to improve the electrochemical stability in the rechargeable metal batteries were discussed in Chapter 9 and Chapter 10, reflecting the promising applications of these nanomaterials for surface modification.Item Phase controlled synthesis of transition metal carbide nanocrystals by ultrafast flash Joule heating(Springer Nature, 2022) Deng, Bing; Wang, Zhe; Chen, Weiyin; Li, John Tianci; Luong, Duy Xuan; Carter, Robert A.; Gao, Guanhui; Yakobson, Boris I.; Zhao, Yufeng; Tour, James M.; Smalley-Curl Institute; NanoCarbon Center and the Welch Institute for Advanced MaterialsNanoscale carbides enhance ultra-strong ceramics and show activity as high-performance catalysts. Traditional lengthy carburization methods for carbide syntheses usually result in coked surface, large particle size, and uncontrolled phase. Here, a flash Joule heating process is developed for ultrafast synthesis of carbide nanocrystals within 1 s. Various interstitial transition metal carbides (TiC, ZrC, HfC, VC, NbC, TaC, Cr2C3, MoC, and W2C) and covalent carbides (B4C and SiC) are produced using low-cost precursors. By controlling pulse voltages, phase-pure molybdenum carbides including β-Mo2C and metastable α-MoC1-x and η-MoC1-x are selectively synthesized, demonstrating the excellent phase engineering ability of the flash Joule heating by broadly tunable energy input that can exceed 3000 K coupled with kinetically controlled ultrafast cooling (>104 K s−1). Theoretical calculation reveals carbon vacancies as the driving factor for topotactic transition of carbide phases. The phase-dependent hydrogen evolution capability of molybdenum carbides is investigated with β-Mo2C showing the best performance.