Browsing by Author "Pan, PI"

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    In operando detection of lithium diffusion behaviors at low temperature in 18650 Li-ion battery anode
    (Elsevier, 2018-12-15) Wu, CM; Chang, CC; Avdeev, M; Pan, PI; Li, WH
    Lithium diffusion process in an 18650 cell was investigated in-operando using neutron diffraction. The graphite anode delithiation rate and the amount of discharge capacity during the discharging process were correlated with the temperature and current rate. At room temperature, the lithium diffusion rate in LiC6 phase at the high rate capability (C/5) is same as at low rate capability (C/20), which means that lithium diffusion in LiC6 crystal phase is independent of the current rate in this range during the discharge process. Lowering temperature to −20 °C decreases both the lithium diffusion and capacity, although the latter can be partially recovered by using lower C-rate. © 2018 Elsevier B.V.
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    Low temperature effect of lithium diffusion in 18650-type MNC battery
    (Australian Institute of Physics, 2016-02-02) Wu, CM; Avdeev, M; Chang, CC; Pan, PI
    Investigations of the phenomena in atomic scale are essential for fully understandings of the activities in battery operation. The battery is known to be operated in a broad temperature range below and above the ambient temperature. Temperature change could affect the performance, and might even raise safety issue. Li-plating, where metallic Li-ions accumulate onto the graphite anode, is a recently realized atomic pheromone that severely degrades the performance of the battery. These including capacity loss, impedance raise, activity slowing down and aging speeding up. It is now known that intercalation into the graphite and platting onto the graphite surface can both occur when Li-ions return to the graphite anode upon charging. Li-plating will partially block the insertion of Li-ions onto the graphite electrode in some extent, which reduces the migration of Li-ions during discharging and charging. Clearly, local environment, such as temperature or electric field, could affect the insertion rate, but experimental study or theoretical modeling concerning these effects are still limited. Here, we report on the results of studies made, using cold neutron triple-axis spectrometer – SIKA’s elastic mode, on the Li+ diffusion rate of an 18650-type Li-ion battery in discharging-charging operations, carried out at and below the ambient temperature. Sizable in-situ neutron diffraction intensities for the {001} reflection of LiC6, for the {002} reflection of LiC12, as well as for the {004} reflection of LiC54 were clearly detected in very 5 minute interval during a discharging-charging operation, which were then used to extract the Li+ diffusion rate during operation. Interestingly, operation with a C/5 discharging rate performed at -20 ℃ causes a dramatically 25% reduction in the Li+ diffusion rate and even more surprisingly the discharge transfers only 35% of the Li out of the graphite anode since the diffusion essentially stop in the early stage (~1/3) of the discharge period. The reduction and stopping of Li+ diffusion can effectively corrected by employing a lower discharging rate in the operation.
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    Low-temperature effect on lithium diffusion in 18650 Li-ion battery
    (International Conference on Neutron Scattering, 2017-07-12) Wu, CM; Chang, CC; Pan, PI; Avdeev, M
    Investigations of the phenomena at the atomic scale are essential for full understanding of battery operation. The cells are operated in a broad temperature range below and above the ambient temperature. Temperature change could affect the performance and might even raise the safety issue. Apparently, local environment, such as temperature or electric field, could affect the insertion rate, but experimental studies of these effects are still limited. Here, we report on the results of studies made, using cold neutron triple-axis spectrometer – SIKA’s elastic mode, on the Li+ diffusion rate of an 18650-type Li-ion battery in discharging-charging operations, carried out at and below the ambient temperature. Operation with a C/5 discharging rate performed at -20 ? showed a dramatic 25% reduction in the Li+ diffusion rate and even more surprisingly the discharge transfer of only 35% of Lithium out of the graphite anode since the diffusion essentially stops in the early stage (~1/3) of the discharge period. The reduction and stopping of Li+ diffusion can be effectively alleviated by employing a lower discharging rate in operation.
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    The mechanism of the sodiation and desodiation in super P carbon electrode for sodium-ion battery
    (Elsevier, 2017-02-01) Wu, CM; Pan, PI; Cheng, YW; Liu, CP; Chang, CC; Avdeev, M; Lin, SK
    The sodiation and desodiation of sodium (Na) into the Super-P carbon anode material were investigated using electrochemical analyses, high-resolution transmission electron microscopy (HRTEM), and neutron powder diffraction (NPD). In the sodiated Super-P carbon, sodium is stored both in the graphite interlayer space of carbon nano-particles and pores between the particles. Sodium metal clusters found in micro-pores between the carbon particles are responsible for the large irreversible capacity of the Super-P electrode. The graphite interlayer distance increases on sodiation from 3.57 Å to two distinct values of ∼3.84 and 4.41 Å. The mechanism of the process is discussed. © 2016 Elsevier B.V.