Browsing by Author "Wang, JZ"

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    Direct evidence of concurrent solid-solution and two-phase reactions and the nonequilibrium structural eEvolution of LiFePO(4)
    (American Chemical Society, 2012-05-09) Sharma, N; Guo, XW; Du, GD; Guo, ZP; Wang, JZ; Wang, ZX; Peterson, VK
    Lithium-ion batteries power many portable devices and in the future are likely to play a significant role in sustainable-energy systems for transportation and the electrical grid. LiFePO(4) is a candidate cathode material for second-generation lithium-ion batteries, bringing a high rate capability to this technology. LiFePO(4) functions as a cathode where delithiation occurs via either a solid-solution or a two-phase mechanism, the pathway taken being influenced by sample preparation and electrochemical conditions. The details of the delithiation pathway and the relationship between the two-phase and solid-solution reactions remain controversial. Here we report, using real-time in situ neutron powder diffraction, the simultaneous occurrence of solid-solution and two-phase reactions after deep discharge in nonequilibrium conditions. This work is an example of the experimental investigation of nonequilibrium states in a commercially available LiFePO(4) cathode and reveals the concurrent occurrence of and transition between the solid-solution and two-phase reactions. © 2012, American Chemical Society.
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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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    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