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14. Degradation Diagnostics from the Subsurface of Lithium‐Ion Battery Electrodes.

Author

Yao, Xuhui, Šamořil, Tomáš, Dluhoš, Jiří, Watts, John F., Du, Zhijia, Song, Bohang, Silva, S. Ravi P., Sui, Tan, and Zhao, Yunlong

Subjects
LITHIUM-ion batteries, ELECTRODES, FOCUSED ion beams, PLASMA etching, PLASMA focus, SOLID electrolytes, CONFLICT management
Abstract

Despite the long‐established rocking‐chair theory of lithium‐ion batteries (LIBs), developing novel characterization methodology with higher spatiotemporal resolution facilitates a better understanding of the solid electrolyte interphase studies to shape the reaction mechanisms. In this work, we develop a Xenon ion plasma focused ion beam (Xe+ PFIB)‐based characterization technique to probe the cross‐sectional interface of both ternary cathode and graphite anode electrodes, with the focus on revealing the chemical composition and distribution underneath the electrode surface by in‐depth analysis of secondary ions. Particularly, the lithium fluoride is detected in the pristine cathode prior to contact with the electrolyte, reflecting that the electrode degradation is in the form of the loss of lithium inventory during electrode preparation. This degradation is related to the hydrolysis of the cathode material and the decomposition of the PVDF binder. Through the quantitative analysis of the transition‐metal degradation products, manganese is found to be the dominant element in the newly formed inactive fluoride deposition on the cathode, while no transition metal signal can be found inside the anode electrode. These insights at high resolution implemented via a PFIB‐based characterization technique not only enrich the understanding of the degradation mechanism in the LIBs but also identify and enable a high‐sensitivity methodology to obtain the chemical survey at the subsurface, which will help remove the capacity‐fade observed in most LIBs. [ABSTRACT FROM AUTHOR]

Published
2022
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16. New Insights into Structural Evolution of LiNiO2 Revealed by Operando Neutron Diffraction.

Author

Chien, Po‐Hsiu, Wu, Xianyang, Song, Bohang, Yang, Zhijie, Waters, Crystal K., Everett, Michelle S., Lin, Feng, Du, Zhijia, and Liu, Jue

Subjects
NEUTRON diffraction, BOND angles, CHEMICAL bond lengths, CRYSTAL lattices, CHARGE transfer, PHASE transitions
Abstract

LiNiO2 (LNO) represents the end member in the compositional space of the LiNi1‐x‐yMnxCoyO2 (as x and y approach zero) cathode system. Despite its high theoretical specific capacity (275 mAh/g), LNO suffers from phase transitions with large volume change and unfavorable reactions upon electrochemical cycling, which restricts its practical use in the application of lithium‐ion batteries. While the contributing factor to the structural instability is commonly linked to the undesired volume collapse associated with the H2‐H3 phase transition, detailed analysis of structural evolution following the entire route of phase transitions (H1‐M‐H2‐H3) in real time under battery operating conditions remains a challenging task. In this work, we employ operando neutron diffraction to study the structural changes (crystal lattice, Li/Ni−O bond length, O−Ni−O bond angles, and LiO2/NiO2 layer thickness) of LNO cathode in a home‐built LixNiO2||graphite full cell during Li+ de‐/intercalation. In particular, the anomalous increase(decrease) of Ni−O(Li−O) bond length at high SOC (>∼85 %) in the H3 phase is discussed in the context of O2− (2p)→Ni4+(3d) negative charge transfer. [ABSTRACT FROM AUTHOR]

Published
2021
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20. Understanding the Low-Voltage Hysteresis of Anionic Redox in Na2Mn3O7

Author

Song, Bohang, primary, Tang, Mingxue, additional, Hu, Enyuan, additional, Borkiewicz, Olaf J., additional, Wiaderek, Kamila M., additional, Zhang, Yiman, additional, Phillip, Nathan D., additional, Liu, Xiaoming, additional, Shadike, Zulipiya, additional, Li, Cheng, additional, Song, Likai, additional, Hu, Yan-Yan, additional, Chi, Miaofang, additional, Veith, Gabriel M., additional, Yang, Xiao-Qing, additional, Liu, Jue, additional, Nanda, Jagjit, additional, Page, Katharine, additional, and Huq, Ashfia, additional

Published
2019
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28. Exploiting the Oxygen Redox Reaction and Crystal-Preferred Orientation in a P3-Type Na2/3Mg1/3Mn2/3O2Thin-Film Electrode

Author

Zhang, Yiman, Phillip, Nathan D., Song, Bohang, Sacci, Robert L., Liu, Jue, and Dudney, Nancy J.

Abstract

The anionic redox reaction (ARR) can be used to enhance the capacity of cathode materials. Understanding how ARR proceeds along with transition metal redox electrochemistry is crucial for designing the next-generation high-energy-density cathodes. In this study, we use a Na2/3Mg1/3Mn2/3O2(NMMO) thin film as a model cathode material for Na-ion batteries to study the oxygen redox reaction. We are able to control the orientation of the thin film using a pre-conditioning step of the Pt current collector layer and, thus, tune the cathode electrolyte interphase (CEI). Preferential orientation along the (001) direction prevents the extraction of Na+ions from the lattice during charge. However, the randomly oriented NMMO thin films perform similar to the slurry electrode from powder. The characteristics of the electrode surface from XPS illustrate the evolution of CEI at different states of charge in the randomly oriented thin-film electrode. Our results show that the crystalline orientation can drastically affect the availability of the electrochemical reaction.

Published
2020
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30. A novel P3-type Na2/3Mg1/3Mn2/3O2 as high capacity sodium-ion cathode using reversible oxygen redox.

Author

Song, Bohang, Hu, Enyuan, Liu, Jue, Zhang, Yiman, Yang, Xiao-Qing, Nanda, Jagjit, Huq, Ashfia, and Page, Katharine

Abstract

There is great interest in the discovery of Li/Na-ion cathode materials with capacity exceeding the limitation of conventional intercalation-based oxide cathodes. One plausible but challenging path is to reversibly use the charge compensation of both lattice oxygen redox and transition metal (TM) redox. Here, we report that lattice oxygen redox alone contributes over 190 mA h g−1 charge capacity (cut-off at 4.65 V vs. Na+/Na) for the newly synthesized P3-type Na2/3Mg1/3Mn(iv)2/3O2. Similar amounts of discharge capacity are reversibly achieved. The discharge capacity exceeds 220 mA h g−1 when Mn3+/Mn4+ redox is partially used in addition to the oxygen redox reaction. This represents one of the highest energy density sodium-ion cathodes with superior low-cost. Our results reveal that cations with strong ionic bonding nature with oxygen (such as Mg2+) are very effective in inducing the reversible oxygen redox reaction. We also identified the origin of voltage hysteresis to be a P3-to-O3 phase transition in concomitance with Mg2+ migration, suggesting further structure design that reduces the structure transition induced cation migration is critical for increasing the energy efficiency of the oxygen redox reactions. [ABSTRACT FROM AUTHOR]

Published
2019
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37. Metastable Li1+δMn2O4(0 ≤ δ ≤ 1) Spinel Phases Revealed by in Operando Neutron Diffraction and First-Principles Calculations

Author

Song, Bohang, Veith, Gabriel M., Park, Jinseon, Yoon, Mina, Whitfield, Pamela S., Kirkham, Melanie J., Liu, Jue, and Huq, Ashfia

Abstract

In this work, we examine the reaction mechanisms driven by the lithiation of Li1+δMn2O4(0 ≤ δ ≤ 1) spinels via in operando neutron powder diffraction (NPD). New reaction mechanisms are proposed involving solid-solution regions within both cubic and tetragonal spinel phases in addition to a continuous phase transition between them. In operando NPD is an ideal tool to follow the light elements such as lithium and oxygen in cathode materials which are often the key to fully understand their structural evolutions. Here, we report a novel methodology to prepare an extremely thick electrode with ∼378 mg·cm–2loading density suitable for the in operando NPD studies. Enabled by such thick electrode, we find that the metal oxygen M–O (M = Li and Mn) bond lengths in both end members LiMn2O4and Li2Mn2O4experience pronounced changes larger than dictated by the change in lattice parameters because of the locally formed Jahn–Teller distorted Mn3+. First-principles density functional theory calculations confirm these metastable intermediates and further propose atomistic reaction pathways for the phase transition by coupling a global structure search algorithm. These findings redefine the conventional understandings on two-phase reactions of this spinel material.

Published
2019
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42. Synthesis and Electrochemical and Structural Investigations of Oxidatively Stable Li2MoO3and xLi2MoO3·(1 – x)LiMO2Composite Cathodes

Author

Self, Ethan C., Zou, Lianfeng, Zhang, Ming-Jian, Opfer, Richard, Ruther, Rose E., Veith, Gabriel M., Song, Bohang, Wang, Chongmin, Wang, Feng, Huq, Ashfia, and Nanda, Jagjit

Abstract

The structural evolution of Li2MoO3during electrochemical delithiation/lithiation is reported. Li2MoO3undergoes an irreversible crystalline to amorphous transformation which starts during the first delithiation step and gradually proceeds throughout subsequent cycles. This observation is supported by complementary data obtained from X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The amorphization does not prevent reversible Li storage, and the Li2MoO3cathodes exhibit initial capacities of 147 mAh/g (corresponding to 0.87 Li cycled per formula unit) at an average operating potential ∼2.5 V vs Li/Li+with reasonably good cycling stability (81% capacity retention after 50 cycles). In-situmass spectrometry studies reveal the amorphization of Li2MoO3does not involve the release of oxygen gas even when charged to very positive potentials (i.e., 4.8 V vs Li/Li+). The Li storage properties and excellent oxidative stability of Li2MoO3make it a promising candidate to improve the performance of traditional LiMO2compounds in layered–layered composite cathodes with the general formula xLi2MoO3·(1 – x)LiMO2. Multiple synthesis routes were explored to prepare composites with x= 0.10–0.15, and their structure was characterized using XRD and time-of-flight neutron diffraction. Preliminary characterization of these materials shows that Li2MoO3improves the cycling stability of an NMC cathode, presumably by mitigating detrimental structural rearrangement at high states of charge.

Published
2018
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