Browsing by Author "Lee, PH"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Monitoring the phase evolution in LiCoO2 electrodes during battery cycles using in-situ neutron diffraction technique
    (John Wiley & Sons, Inc, 2019-12-03) Jena, A; Lee, PH; Pang, WK; Hsiao, KC; Peterson, VK; Darwish, TA; Yepuri, NR; Wu, SH; Chang, H; Liu, RS
    LiCoO2 (LCO) with average particle distribution of 8 μm (LCO-A) and 11 μm (LCO-B) exhibit substantial differences in cycle performance. The half-cells have similar first-cycle discharge capacities of 173 and 175 mAh/g at 0.25 C, but after 100 cycles, the discharge capacities are substantially different, that is, 114 and 141 mAh/g for LCO-A and LCO-B, respectively. Operando neutron powder diffraction of full LCO||Li4Ti5O12 batteries show differences in the LCO reaction mechanism underpinning the electrochemical behavior. LCO-A follows a purely solid solution reaction during cycling compared to the solid solution and two-phase reaction mechanism in LCO-B. The absence of the two-phase reaction in LCO-A is consistent with a homogeneous distribution of Li throughout the particle. The two-phase reaction in LCO-B reflects two distinguishable distributions of Li within the particles. The faster capacity decay in LCO-A is correlated to an increase in electrode cracking during battery cycles. © 2019 The Chemical Society Located in Taipei & Wiley-VCH Verlag GmbH & Co.
  • No Thumbnail Available
    Item
    The storage degradation of an 18650 commercial cell studied using neutron powder diffraction
    (Elsevier, 2018-01-15) Lee, PH; Wu, SH; Pang, WK; Peterson, VK
    Commercial 18650 lithium ion cells containing a blended positive electrode of layered LiNi0.5Mn0.3Co0.2O2 and spinel Li1.1Mn1.9O4 alongside a graphite negative electrode were stored at various depth-of-discharge (DoD) at 60 °C for 1, 2, 4, and 6 months. After storage, the cells were cycled at C/25 at 25 °C between 2.75 and 4.2 V for capacity determination and incremental capacity analysis (ICA). In addition to ICA analysis, the mechanism for capacity fade was investigated by combining the results of neutron powder diffraction under in-situ and operando conditions, in conjunction with post-mortem studies of the electrodes using synchrotron X-ray powder diffraction and inductively-coupled plasma optical emission spectroscopy. Among the cells, those stored at 25% DoD suffered the highest capacity fade due to their higher losses of active Li, NMC, and LMO than cells stored at other DoD. The cells stored at 0% DoD shows second high capacity fade because they exhibit the highest of active LMO and graphite anode among the stored cells and higher losses of active Li and NMC than cells stored at 50% DoD. © 2017 Elsevier B.V