Browsing by Author "See, KW"

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    Developing high-voltage spinel LiNi0.5Mn1.5O4 cathodes for high-energy-density lithium-ion batteries: current achievements and future prospects
    (Royal Society of Chemistry, 2020-05-22) Liang, GM; Peterson, VK; See, KW; Guo, ZP; Pang, WK
    High-voltage spinel LiNi0.5Mn1.5O4 (LNMO) is a promising cathode for the next-generation high-performance lithium-ion batteries (LIBs) due to its high energy density (650 W h kg−1), high operating voltage (∼4.7 V vs. Li), low fabrication cost, and low environmental impact. However, the short cycle life of LNMO caused by rapid capacity decay during cycling limits its wide application and commercialization. Intense research effort to improve the electrochemical performance of LNMO has been moderately successful. Accordingly, it is absolutely necessary to revisit and summarize the up-to-date findings and deeper understanding of how to modify LNMO. In this review, the crystallographic structure and electrochemical properties of LNMO spinel, as well as its existing issues and corresponding solutions, are discussed in detail. In addition, the current accomplishments relating to LNMO application in full-cell configurations are also discussed. Finally, some insight into the future prospects for LNMO cathode developments is provided. © The Royal Society of Chemistry 2020
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    Enhanced thermoelectric performance and mechanical strength of n-type BiTeSe materials produced via a composite strategy
    (Elsevier, 2022-01) Yang, G; Sang, L; Mitchell, DRG; Yun, FF; See, KW; Ahmed, AJ; Sayyar, S; Bake, A; Liu, P; Chen, L; Yue, ZJ; Cortie, DL; Wang, XL
    Zone-melted Bi2Te2.7Se0.3 (ZM BTS) alloys are typical n-type commercial thermoelectric (TE) materials and are utilized for refrigeration and power generation near room temperature. They usually suffer from poor mechanical performance, as well as having a low figure of merit (ZT). In this work, we report an effective composite strategy to improve both the TE and mechanical performance of n-type BTS materials by incorporating carbon microfibers. The introduction of carbon microfibers in BTS effectively reduces the lattice thermal conductivity due to phonon scattering at multi-scale boundaries and due to the large interfacial thermal resistance arising from phonon mismatch between the constituent phases. Simultaneously, it also gives rise to an enhancement of the electrical conductivity, which originates from the increased carrier density without significant limitation on its weighted mobility. Consequently, a high peak ZT of 1.1 at 400 K and an average ZTave value of 0.95 are achieved in the temperature range 300 ~ 550 K, yielding a calculated efficiency of η = 9%. Moreover, the BTS/carbon microfiber composites show superior compressive strength compared to a commercial ZM BTS sample. This improved strength is highly desirable for real-world TE applications. Our results demonstrate a novel way to produce high-performance TE materials, in which interfaces with large thermal resistance are used to achieve low thermal conductivity without significantly degrading the electrical properties of the materials. © 2021 Elsevier B.V.