Browsing by Author "Jena, A"

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    Capacity enhancement of the quenched Li-Ni-Mn-Co oxide high-voltage Li-ion battery positive electrode
    (Elsevier, 2017-03-23) Jena, A; Lee, CH; Pang, WK; Peterson, VK; Sharma, N; Wang, CC; Song, YF; Lin, CC; Chang, H; Liu, RS
    Li-rich metal oxides, regarded as a high-voltage composite cathode, is currently one of the hottest positive electrode material for lithium-ion batteries, due to its high-capacity and high-energy performance. The crystallography, phase composition and morphology can be altered by synthesis parameters, which can influence drastically the capacity and cycling performance. In this work, we demonstrate Li1.207Ni0.127Mn0.54Co0.127O2, obtained by a co-precipitation method, exhibits super-high specific capacity up to 298 mAh g−1 and excellent capacity retention of ∼100% up to 50 cycles. Using neutron powder diffraction and transmission X-ray microscopy, we have found that the cooling-treatments applied after sintering during synthesis are crucially important in controlling the phase composition and morphology of the cathodes, thereby influencing the electrochemical performance. Unique spherical microstructure, larger lattice, and higher content of Li-rich monoclinic component can be achieved in the rapid quenching process, whereas severe particle cracking along with the smaller lattice and lower monoclinic component content is obtained when natural cooling of the furnace is applied. Combined with electrochemical impedance spectra, a plausible mechanism is described for the poorer specific capacity and cycling stability of the composite cathodes. © 2017 Elsevier Ltd.
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    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.