Browsing by Author "Guo, H"

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    Enhancing the reaction kinetics and structural stability of high-voltage LiCoO 2 via polyanionic species anchoring
    (Royal Society of Chemistry (RSC), 2024-05-16) Zheng, W; Liang, GM; Guo, H; Li, JX; Zou, JS; Yuwono, JA; Shu, H; Zhang, S; Peterson, VK; Johannessen, B; Thomsen, L; Hu, WB; Guo, ZP
    Increasing the charging voltage to 4.6 V directly enhances battery capacity and energy density of LiCoO2 cathodes for lithium-ion batteries. However, issues of the activated harmful phase evolution and surface instability in high-voltage LiCoO2 lead to dramatic battery capacity decay. Herein, polyanionic PO43− species have been successfully anchored at the surface of LiCoO2 materials, achieving superior battery performance. The polyanionic species acting as micro funnels at the material surface, could expand LiCoO2 surface lattice spacing by 10%, contributing to enhanced Li diffusion kinetics and consequent excellent rate performance of 164 mA h g−1 at 20C (1C = 274 mA g−1). Crucially, polyanionic species with high electronegativity could stabilize surface oxygen at high voltage by reducing O 2p and Co 3d orbital hybridization, thus suppressing surface Co migration and harmful H1–3 phase formation and leading to superior cycling stability with 84% capacity retention at 1C after 300 cycles. Furthermore, pouch cells containing modified LiCoO2 and Li metal electrodes deliver an ultra-high energy density of 513 W h kg−1 under high loadings of 32 mg cm−2. This work provides insightful directions for modifying the material surface structure to obtain high-energy-density cathodes with high-rate performance and long service life. © Royal Society of Chemistry 2024.
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    Pentanary transition-metals Na-ion layered oxide cathode with highly reversible O3-P3 phase transition
    (Elsevier, 2021-05-15) Guo, H; Avdeev, M; Sun, K; Ma, XB; Wang, HL; Hu, YS; Chen, DF
    Two dual-cation transition metal fluorides K2TiF6 and K2NbF7 are introduced into Mg(BH4)2 by ball-milling to catalyze the dehydrogenation of Mg(BH4)2. According to the DSC and TPD results, the onset dehydrogenation temperature of Mg(BH4)2 doped with K2TiF6 and K2NbF7 are remarkably reduced to 105.4 and 118.0 °C, respectively. Meanwhile, both the K2TiF6 and K2NbF7 catalyzed systems can release more than 6.4 wt% H2 under 280 °C, showing an improvement in dehydrogenation kinetics. In addition, the reversible capacity of the Mg(BH4)2–3%K2TiF6 system is 2.7 wt% at 280 °C in 250 min, which is enhanced comparing to that of pristine Mg(BH4)2. X-ray diffraction, Fourier-transformed infrared and 11B nuclear magnetic resonance investigations reveal that the K2TiF6 actually acts as a catalytic precursor to react with Mg(BH4)2, forming active hydrides of KBH4 and TiH2, which further serve as catalyzing agents to facilitate the re-generation of Mg(BH4)2 from intermediates under moderate conditions. © 2021 Elsevier B.V.