Browsing by Author "Chou, SL"

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    Development and investigation of a NASICON‐type high‐voltage cathode material for high‐power sodium‐ion batteries
    (Wiley, 2020-02-03) Chen, MZ; Hua, WB; Xiao, J; Cortie, DL; Guo, XD; Wang, E; Gu, QF; Hu, Z; Indris, S; Wang, XL; Chou, SL; Dou, SX
    Herein, we introduce a 4.0 V class high‐voltage cathode material with a newly recognized sodium superionic conductor (NASICON)‐type structure with cubic symmetry (space group P213), Na3V(PO3)3N. We synthesize an N‐doped graphene oxide‐wrapped Na3V(PO3)3N composite with a uniform carbon coating layer, which shows excellent rate performance and outstanding cycling stability. Its air/water stability and all‐climate performance were carefully investigated. A near‐zero volume change (ca. 0.40 %) was observed for the first time based on in situ synchrotron X‐ray diffraction, and the in situ X‐ray absorption spectra revealed the V3.2+/V4.2+ redox reaction with high reversibility. Its 3D sodium diffusion pathways were demonstrated with distinctive low energy barriers. Our results indicate that this high‐voltage NASICON‐type Na3V(PO3)3N composite is a competitive cathode material for sodium‐ion batteries and will receive more attention and studies in the future. © 2019Wiley-VCHVerlagGmbH&Co
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    Enhanced reversible lithium storage in a nanosize silicon/graphene composite.
    (Elsevier, 2010-02) Chou, SL; Wang, JZ; Choucair, M; Liu, HK; Stride, JA; Dou, SX
    Si/graphene composite was prepared by simply mixing of commercially available nanosize Si and graphene. Electrochemical tests show that the Si/graphene composite maintains a capacity of 1168 mAh g−1 and an average coulombic efficiency of 93% up to 30 cycles. EIS indicates that the Si/graphene composite electrode has less than 50% of the charge-transfer resistance compared with nanosize Si electrode, evidencing the enhanced ionic conductivity of Si/graphene composite. The enhanced cycling stability is attributed to the fact that the Si/graphene composite can accommodate large volume charge of Si and maintain good electronic contact. © 2010, Elsevier Ltd.
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    Epitaxial nickel rerrocyanide stabilizes Jahn–Teller distortions of manganese ferrocyanide for sodium‐ion batteries
    (Wiley, 2021-06-06) Gebert, F; Cortie, DL; Bouwer, JC; Wang, W; Yan, Z; Dou, SX; Chou, SL
    Manganese‐based Prussian Blue, Na2−δMn[Fe(CN)6] (MnPB), is a good candidate for sodium‐ion battery cathode materials due to its high capacity. However, it suffers from severe capacity decay during battery cycling due to the destabilizing Jahn–Teller distortions it undergoes as Mn2+ is oxidized to Mn3+. Herein, the structure is stabilized by a thin epitaxial surface layer of nickel‐based Prussian Blue (Na2−δNi[Fe(CN)6]). The one‐pot synthesis relies on a chelating agent with an unequal affinity for Mn2+ and Ni2+ ions, which prevents Ni2+ from reacting until the Mn2+ is consumed. This is a new and simpler synthesis of core–shell materials, which usually needs several steps. The material has an electrochemical capacity of 93 mA h g−1, of which it retains 96 % after 500 charge–discharge cycles (vs. 37 % for MnPB). Its rate capability is also remarkable: at 4 A g−1 (ca. 55 C) it can reversibly store 70 mA h g−1, which is also reflected in its diffusion coefficient of ca. 10−8 cm2 s−1. The epitaxial outer layer appears to exert an anisotropic strain on the inner layer, preventing the Jahn–Teller distortions it normally undergoes during de‐sodiation. © 1999-2024 John Wiley & Sons, Inc
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    Irradiation Si on carbon nanotube paper as a flexible anode material for lithium-ion batteries
    (American Scientific Publishers, 2012-02-01) Chou, SL; Ionescu, M; Wang, JZ; Winton, BR; Liu, HK
    Silicon/single-walled carbon nanotube (SWCNT) composite paper was modified by low energy ion implantation using Si to obtain a flexible composite paper. Raman and FE-SEM results show that structure of SWCNT could be destroyed by the implantation. Electrochemical measurements display that the implanted Si can improve the specific capacity and the reversible capacity of CNT paper. After 50 cycles, the specific capacity of Si-implanted CNT paper is 30% higher than the pristine CNT. © 2020 Ingenta
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    Lithium rich and deficient effects in LixCoPO4 (x=0.90, 0.95, 1, 1.05) as cathode material for lithium-ion batteries
    (Elsevier, 2013-01-15) Xu, J; Chou, SL; Avdeev, M; Sale, M; Liu, HK; Dou, SX
    A series of LixCoPO4 (x = 0.90, 0.95, 1, 1.05) compounds with different lithium content in the starting compositions were prepared by the sol–gel method. The phase identification was carried out by X-ray diffraction and neutron diffraction. The structure, atom positions, and occupancies were characterized by neutron diffraction. The morphology of LixCoPO4 (x = 0.90, 0.95, 1, 1.05) was examined by field emission scanning electron microscopy. Electrochemical analysis indicated that Li0.95CoPO4 presented the highest discharge capacity at various current densities among all the different x value compounds. The Li0.95CoPO4 showed better cycling stability and coulombic efficiency in the room temperature ionic liquid electrolyte ([C3mpyr][NTf2] containing 1 M LiNTf2) at various current densities in the voltage range of 3.5–5.0 V than in the conventional electrolyte (1 M LiPF6 in ethylene carbonate:diethyl carbonate).© 2012, Elsevier Ltd.
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    NASICON-type air-stable and all-climate cathode for sodium-ion batteries with low cost and high-power density
    (Springer Nature, 2019-04-01) Chen, MZA; Hua, WB; Xiao, Jin; Cortie, DL; Chen, W; Wang, E; Hu, Z; Gu, QF; Wang, XL; Indris, S; Chou, SL; Dou, SX
    The development of low-cost and long-lasting all-climate cathode materials for the sodium ion battery has been one of the key issues for the success of large-scale energy storage. One option is the utilization of earth-abundant elements such as iron. Here, we synthesize a NASICON-type tuneable Na4Fe3(PO4)2(P2O7)/C nanocomposite which shows both excellent rate performance and outstanding cycling stability over more than 4400 cycles. Its air stability and all-climate properties are investigated, and its potential as the sodium host in full cells has been studied. A remarkably low volume change of 4.0% is observed. Its high sodium diffusion coefficient has been measured and analysed via first-principles calculations, and its three-dimensional sodium ion diffusion pathways are identified. Our results indicate that this low-cost and environmentally friendly Na4Fe3(PO4)2(P2O7)/C nanocomposite could be a competitive candidate material for sodium ion batteries. - © Open Access This article is licensed under a Creative Commons Attribution 4.0
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    Solving key challenges in battery research using in situ synchrotron and neutron techniques
    (John Wiley & Sons, Inc, 2017-03-17) Gu, QF; Kimpton, JA; Brand, HEA; Wang, ZY; Chou, SL
    Understanding the electrochemical reaction mechanisms and kinetics in batteries is the key challenge for developing breakthroughs with new or existing electrode materials. X-rays and neutrons are excellent probes for studying atomic structure changes and phase evolution in battery materials during charge and discharge. Synchrotron X-ray powder diffraction (SXPD), with its high angular resolution and beam intensity, allows fast scattering and diffraction data collection to record crystalline structure changes that occur on short time-scales. Neutron powder diffraction (NPD) provides complementary information that is sensitive to different structural details during charge/discharge. More recently X-ray absorption spectroscopy (XAS) has been used to identify the oxidation states of transition metal ions present in new cathode compositions at different stages of battery cycling. Using in-house designed battery cells, electrodes or other cell components can be subjected to conditions designed to mimic their real operating conditions. It is preferable to investigate battery materials in operation to identify any critical intermediate stages during charge/discharge rather than using ex situ methods to analyse dismantled batteries. Examples and combinations of SXPD, XAS, and NPD measurements, which have been used to investigate lithium ion batteries and sodium ion batteries, are described and reviewed in this contribution. © 2017 Wiley-VCH Verlag GmbH & Co