Browsing by Author "Liu, Yadong"

Now showing 1 - 7 of 7
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    Building Better Li Metal Anodes in Liquid Electrolyte: Challenges and Progress
    (ACS, 2021-01) Yu, Yikang; Liu, Yadong; Xie, Jian; Mechanical and Energy Engineering, School of Engineering and Technology
    Li metal has been widely recognized as a promising anode candidate for high-energy-density batteries. However, the inherent limitations of Li metal, that is, the low Coulombic efficiency and dendrite issues, make it still far from practical applications. In short, the low Coulombic efficiency shortens the cycle life of Li metal batteries, while the dendrite issue raises safety concerns. Thanks to the great efforts of the research community, prolific fundamental understanding as well as approaches for mitigating Li metal anode safety have been extensively explored. In this Review, Li electrochemical deposition behaviors have been systematically summarized, and recent progress in electrode design and electrolyte system optimization is reviewed. Finally, we discuss the future directions, opportunities, and challenges of Li metal anodes.
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    Effects of Ink Formulation on Construction of Catalyst Layers for High-Performance Polymer Electrolyte Membrane Fuel Cells
    (ACS, 2021-07) Gong, Qing; Li, Chenzhao; Liu, Yadong; Ilavsky, Jan; Guo, Fei; Cheng, Xuan; Xie, Jian; Mechanical and Energy Engineering, School of Engineering and Technology
    Rational design of catalyst layers in a membrane electrode assembly (MEA) is crucial for achieving high-performance polymer electrolyte membrane fuel cells. Establishing a clear understanding of the property (catalyst ink)-structure (catalyst layer)-performance (MEA) relationship lays the foundation for this rational design. In this work, a synergistic approach was taken to correlate the ink formulation, the microstructure of catalyst layers, and the resulting MEA performance to establish such a property-structure-performance relationship. The solvent composition (n-PA/H2O mixtures) demonstrated a strong influence on the performance of the MEA fabricated with an 830-EW (Aquivion) ionomer, especially polarization losses of cell activation and mass transport. The performance differences were studied in terms of how the solvent composition affects the catalyst/ionomer interface, ionomer network, and pore structure of the resulting catalyst layers. The ionomer aggregates mainly covered the surface of catalyst aggregates acting as oxygen reduction reaction active sites, and the aggregate sizes of the ionomer and catalyst (revealed by ultrasmall angle X-ray scattering and cryo-transmission electron microscopy) were dictated by tuning the solvent composition, which in turn determined the catalyst/ionomer interface (available active sites). In n-PA/H2O mixtures with 50∼90 wt % H2O, the catalyst agglomerates could be effectively broken up into small aggregates, leading to enhanced kinetic activities. The boiling point of the mixed solvents determined the pore structure of ultimate catalyst layers, as evidenced by mercury porosimetry and scanning electron microscopy. For mixed solvents with a higher boiling point, the catalyst-ionomer aggregates in the ink tend to agglomerate during the solvent evaporation process and finally form larger catalyst-ionomer aggregates in the ultimate catalyst layer, resulting in more secondary pores and thus lower mass transport resistance. Both the enlarged catalyst/ionomer interface and appropriate pore structure were achieved with the catalyst layer fabricated from an n-PA/H2O mixture with 90 wt % H2O, leading to the best MEA performance.
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    Effects of Ink Formulation on the Structure and Performance of PGM-Free Catalyst Layer in PEMFCs
    (IOP, 2021) Li, Chenzhao; Liu, Shengwen; Zeng, Yachao; Liu, Yadong; Wu, Gang; Cullen, David A.; Xie, Jian; Mechanical and Energy Engineering, Purdue School of Engineering and Technology
    Platinum group metal (PGM) catalysts are the major electrocatalysts for oxygen reduction reaction (ORR) in the polymer electrolyte membrane fuel cells (PEMFCs). The cost becomes unaffordable if the PEMFC is in massive application. The PGM-Free catalyst shows very promising activity in rotation disk electrode (RDE) testing. The half-wave potential could reach 0.91 V versus standard hydrogen electrode (SHE). However, in a membrane electrode assembly (MEA), the performance of PGM-Free catalysts is not good enough to replace the PGM catalysts. Since the PGM-free catalysts are so different from the PGM catalysts in terms of catalytic activity, stability, surface conditions, particle size, etc., the fabrication of PGM-Free catalyst MEA cannot simply copy the method of making PGM MEA. We proposed a novel method of fabricating PGM-Free catalyst MEA, so that the intrinsic catalyst activity from RDE can be translated into MEA performance. The method is based on the catalyst coated membrane (CCM) method using optimized ionomer to carbon (I/C) ratio and solvent mixture of catalyst ink. Using this method, the PGM-free catalyst MEA achieved the current density 44.9 mA cm-2 at 0.9 V iR-free in H2/O2 and 150 mA cm-2 at 0.8 V in H2/air, which surpassed the performance targets of US Department of Energy (DOE)for PGM-Free catalyst MEA. The property (solvent composition, dispersion of catalyst and ionomer in an ink), structure (pore structure) and the MEA performance have been characterized using, mercury intrusion porosimetry (MIP), MEA testing. A property-structure-performance relationship has been established.
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    Failure Detection for Over-Discharged Li-Ion Batteries
    (Office of the Vice Chancellor for Research, 2012-04-13) Xiong, Jing; Banvait, Harpreetsingh; Li, Lingxi; Chen, Yaobin; Xie, Jian; Liu, Yadong; Wu, Meng; Chen, Jie
    Li-ion batteries are high density, slow loss of charge when not in use and no memory effect. Vast research on Li-ion batteries has been focusing on increasing the energy density, durability, and cost. Due to its advantages it has been widely used in consumer electronics and electric vehicles. Apart from its advantages, safety is a major concern for Li-ion batteries. The Li-ion safety issues have been widely publicized due to devastating incidents with laptop and cell phone batteries. Despite of much research towards the safety of Li-ion battery, it remains as a major concern related to Li-Ion batteries. A failure of Li-ion battery may result in thermal runaway. Li-ion battery failure may be due to overcharge, over-discharge, short circuits, particles poisoning, mechanical or thermal damage [1, 2]. Short circuit, overcharge, and over-discharge are the most common electrical abuses a battery suffers. This poster presents preliminary results for the failure signatures of over-discharged Li-ion batteries, and proposes a rule-based method and a probabilistic method for failure detection. The two methods Rule-based method and Probabilistic method are verified using experimental results for a Li-ion battery. The proposed methods were successfully implemented in a real-time system for failure detection and early warning.
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    In Situ Temperature Evolution and Failure Mechanisms of LiNi0.33Mn0.33Co0.33O2 Cell under Over-Discharge Conditions
    (ECS, 2018-09) Wu, Linmin; Liu, Yadong; Cui, Yi; Zhang, Yi; Zhang, Jing; Mechanical Engineering, School of Engineering and Technology
    In this work, in situ study of commercial 18650 NMC (LiNi0.33Mn0.33Co0.33O2) cells under over-discharge charge conditions (100%, 110%, and 120%) has been performed. Both voltage and cell skin temperature evolutions were simultaneously monitored in situ during discharge process. The results show that there is a clear correlation between the voltage and temperature. For the NMC cell under 120% over-discharge condition, the cell failed after only 1 cycle. The voltage dropped to negative values at the end of the discharge. The skin temperature at the end of discharge increased dramatically to 73°C, indicating strong exothermal reactions happened inside the cell. For the 110% over-discharged cell, the cell failed after 10 cycles. The voltage at the end of the discharge process became negative after the 1st cycle. The cell skin temperature increased from 23.2°C to 61.7°C. The peak temperature in each cycle kept increasing until failure. These implies the micro short circuits were developed during the charge-discharge process. The failed components were examined by SEM/EDX and XRD. The results show substantial aluminum exists inside the failed separators. The results suggest that during the over-discharge process, the alumina inside the separator was reduced to aluminum. The electrons migrate through aluminum channel, leading to the failure of the cells.
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    Pseudocapacitive contribution in amorphous FeVO4 cathode for lithium-ion batteries
    (Wiley, 2022) Liu, Tianwei; Liu, Yadong; Niu, Chaoqun; Chao, Zi-Sheng; Mechanical and Energy Engineering, School of Engineering and Technology
    Amorphous iron vanadate (FeVO4 ) nanoparticle cathode materials are successfully synthesized through a facile, efficient, and highyielding ion exchange-liquid precipitation method. The composition, structure, morphology, surface area, and electrochemical performances of the synthesized materials have been characterized by the Thermogravimetric-Differential scanning calorimetry (TGDSC), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), X-ray photon spectroscopy (XPS), Brunauer?Emmet?Teller (BET), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), respectively. The electrochemical performance results indicate that the amorphous FeVO4 delivers a specific capacity as high as 275 mAh g-1 at 0.1 C in a voltage range of 1.5?4.5 V. The excellent electrochemical performances can be ascribed to the pseudocapacitive behavior. The systematic kinetic analysis demonstrates that the pseudocapacitive charge storage allows the amorphous FVO cathode delivering the excellent high specific capacity.
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    V2O5/Graphene Hybrid Supported on Paper Current Collectors for Flexible Ultrahigh-Capacity Electrodes for Lithium-Ion Batteries
    (ACS, 2018-04) Aliahmad, Nojan; Liu, Yadong; Xie, Jian; Agarwal, Mangilal; Mechanical Engineering, School of Engineering and Technology
    An ultrahigh-capacity, flexible electrode made with vanadium pentoxide/graphene (with a specific capacity of 396 mAh/g) supported on paper-based current collectors has been developed. The ultrahigh-capacity graphene-modified vanadium pentoxide is fabricated by incorporating graphene sheets (2 wt %) into the vanadium pentoxide nanorods to improve the specific capacity, cycle life, and rate capability. This active material is then incorporated with the paper-based current collectors [carbon nanotube (CNT)–microfiber paper] to provide flexible electrodes. The flexible current collector has been made by depositing single-wall CNTs over wood microfibers through a layer-by-layer self-assembly process. The CNT mass loading of the fabricated current collectors is limited to 10.1 μg/cm2. The developed electrodes can be used to construct the flexible battery cells, providing a high-capacity/energy and rechargeable energy storage unit for flexible electronic devices.