Browsing by Author "Lu, CZ"

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    Effect of AlF3-coated Li4Ti5O12 on the performance and function of the LiNi0.5Mn1.5O4||Li4Ti5O12 full battery—an in-operando neutron powder diffraction study
    (Frontiers Media S.A., 2018-09-10) Liang, GM; Pillai, AS; Peterson, VK; Ko, KY; Chang, CM; Lu, CZ; Liu, CE; Liao, SC; Chen, JM; Guo, ZP; Pang, WK
    The LiNi0.5Mn1.5O4 ||Li4Ti5O12 (LMNO||LTO) battery possesses a relatively-high energy density and cycle performance, with further enhancement possible by application of an AlF3 coating on the LTO electrode particles. We measure the performance enhancement to the LMNO||LTO battery achieved by a AlF3 coating on the LTO particles through electrochemical testing and use in-operando neutron powder diffraction to study the changes to the evolution of the bulk crystal structure during battery cycling. We find that the AlF3 coating along with parasitic Al doping slightly increases capacity and greatly increases rate capability of the LTO electrode, as well as significantly reducing capacity loss on cycling, facilitating a gradual increase in capacity during the first 50 cycles. Neutron powder diffraction reveals a structural response of the LTO and LNMO electrodes consistent with a greater availability of lithium in the battery containing AlF3-coated LTO. Further, the coating increases the rate of structural response of the LNMO electrode during charge, suggesting faster delithiation, and enhanced Li diffusion. This work demonstrates the importance of studying such battery performance effects within full configuration batteries. Copyright © 2018 Liang, Pillai, Peterson, Ko, Chang, Lu, Liu, Liao, Chen, Guo and Pang.
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    Effects of fluorine and chromium doping on the performance of lithium-rich Li1+xMO2 (M = Ni, Mn, Co) positive electrodes
    (American Chemical Society, 2017-12-26) Pang, WK; Lin, HF; Lu, CZ; Liu, CE; Liao, SC; Chen, JM; Peterson, VK
    Lithium-rich metal oxides Li1+zMO2 (M = Ni, Co Mn, etc.) are promising positive electrode materials for high-energy lithium-ion batteries, with capacities of 250-300 mAh·g-1 that closely approach theoretical intercalation limits. Unfortunately, these materials suffer severe capacity fade on cycling, among other performance issues. While ion substitution can improve the performance of many of these materials, the underlying mechanisms of property modification are not completely understood. In this work we show enhanced performance of the Li1+zMO2 electrode, consisting of Li2MnO3 (with C2/m space group) and LiMO2 (with R3m space group) phases, and establish the effects of cationic and anionic substitution on the phase and structure evolution underpinning performance changes. While the undoped material has a high capacity of ∼270 mAh·g-1, only 79% of this remains after 200 cycles. Including ∼2% Cr in the material, likely at the R3m metal (3a) site, improved cycle performance by ∼13%, and including ∼5% F in the material, likely at the R3m oxygen (6c) site, enhanced capacity by ∼4-5% at the expense of a ∼12% decline in cycle performance. Moreover, Cr doping enhances energy density retention by ∼13%, and F doping suppresses this by 17%. We find that these changes arise by different mechanisms. Both anionic and cationic substitution promote faster Li diffusion, by 48% and 20%, respectively, as determined using cyclic voltammetry and leading to better rate performance. Unlike anionic substitution, cationic substitution enhances structural stability at the expense of some capacity, by suppressing lattice distortion during Li insertion and extraction. This work implicates strategic cationic-anionic codoping for enhanced electrochemical performance in lithium-rich layered metal-oxide phases. © 2017 American Chemical Society.
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    Enhanced rate-capability and cycling-stability of 5 V SiO2- and polyimide-coated cation ordered LiNi0.5Mn1.5O4 lithium-ion battery positive electrodes
    (American Chemical Society, 2017-01-23) Pang, WK; Lin, HF; Peterson, VK; Lu, CZ; Liu, CE; Liao, SC; Chen, JM
    The ordered LiNi0.5Mn1.5O4 spinel exhibits great promise as a potential high-energy positive electrode for lithium-ion batteries due to its exceptionally high working potential of 4.7 V (vs. Li) and energy density of 640 Wh kg–1. The commercial application of this material at such voltages is unfortunately prevented by reaction phenomena including hydrofluoric acid attack and manganese dissolution, as well as the two-phase mechanism of Li insertion and extraction, with these limiting Li diffusivity and cycling stability. In this work, we demonstrate the improved performance of LiNi0.5Mn1.5O4 achieved by encapsulating the material in a thin layer of silica (SiO2) or polyimide using a simple wet-chemical method and organic solvents. The pristine and coated ordered LiNi0.5Mn1.5O4 spinel are both confirmed to have P4332 symmetry, with only a minor difference in their lattice parameter. The SiO2 coating is found to reduce capacity fade of ordered LiNi0.5Mn1.5O4 by 45 and 65% at 25 and 55 °C, respectively, with the improvement attributed to enhanced Li diffusivity alongside the suppression of the hydrofluoric acid attack. The polyimide coating is found to have a marginally negative effect on both capacity and rate performance of ordered LiNi0.5Mn1.5O4, with this being greatly offset by excellent thermal stability leading to high-temperature protection, with the material having the low capacity fade of 0.0585 mAh g–1 cycle–1 at 55 °C, which is comparable to that at 25 °C. While similar effects of these coatings are found for disordered LiNi0.5Mn1.5O4, the magnitude of enhancement to properties offered by these coatings is significantly lesser than those found here for the ordered LiNi0.5Mn1.5O4. A stabilizing effect of the coatings that mitigates against phase segregation occurring during the additional two-phase reaction in the ordered but not the disordered phase of the material may explain the greater benefit of the coatings to the ordered phase. © 2017 American Chemical Society
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    Introducing 4s–2p orbital hybridization to stabilize spinel oxide cathodes for lithium-ion batteries
    (Wiley-VCH GmbH, 2022-04-25) Liang, GM; Olsson, E; Zou, JS; Wu, ZB; Li, JX; Lu, CZ; D'Angelo, AM; Johannessen, B; Thomsen, L; Cowie, BCC; Peterson, VK; Cai, Q; Pang, WK; Guo, ZP
    Oxides composed of an oxygen framework and interstitial cations are promising cathode materials for lithium-ion batteries. However, the instability of the oxygen framework under harsh operating conditions results in fast battery capacity decay, due to the weak orbital interactions between cations and oxygen (mainly 3d–2p interaction). Here, a robust and endurable oxygen framework is created by introducing strong 4s–2p orbital hybridization into the structure using LiNi0.5Mn1.5O4 oxide as an example. The modified oxide delivers extraordinarily stable battery performance, achieving 71.4 % capacity retention after 2000 cycles at 1 C. This work shows that an orbital-level understanding can be leveraged to engineer high structural stability of the anion oxygen framework of oxides. Moreover, the similarity of the oxygen lattice between oxide electrodes makes this approach extendable to other electrodes, with orbital-focused engineering a new avenue for the fundamental modification of battery materials. © 2022 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH - Open access.
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    A long cycle-life high-voltage spinel lithium-ion battery electrode achieved by site-selective doping
    (John Wiley & Sons, Inc, 2020-03-23) Liang, GM; Wu, ZB; Didier, C; Zhang, WC; Cuan, J; Li, BH; Ko, KY; Hung, PY; Lu, CZ; Chen, YZ; Leniec, G; Kaczmarek, SM; Johannessen, B; Thomsen, L; Peterson, VK; Pang, WK; Guo, ZP
    Spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode candidate for the next-generation high energy-density lithium-ion batteries (LIBs). Unfortunately, the application of LNMO is hindered by its poor cycle stability. Now, site-selectively doped LNMO electrode is prepared with exceptional durability. In this work, Mg is selectively doped onto both tetrahedral (8a) and octahedral (16c) sites in the Fdurn:x-wiley:14337851:media:anie202001454:anie202001454-math-0001 m structure. This site-selective doping not only suppresses unfavorable two-phase reactions and stabilizes the LNMO structure against structural deformation, but also mitigates the dissolution of Mn during cycling. Mg-doped LNMOs exhibit extraordinarily stable electrochemical performance in both half-cells and prototype full-batteries with novel TiNb2O7 counter-electrodes. This work pioneers an atomic-doping engineering strategy for electrode materials that could be extended to other energy materials to create high-performance devices. © 2020 Wiley-VCH Verlag GmbH & Co