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RISS 인기검색어
- 검색키워드
- 저자 : Liangliang Shui (검색결과 3 건)
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Miao Shui,Weidong Zheng,Jie Shu,Qingchun Wang,Shan Gao,Dan Xu,Liangliang Cheng,Lin Feng,Yuanlong Ren 한국물리학회 2013 Current Applied Physics Vol.13 No.3
Lithium-ion battery cathode material Li1þxV3O8 is synthesized by a citric acid/tartaric acid assisted sol egel method and sintered at 350 C, 450 C and 550 C for 3 h for the formation of Li1þxV3O8 phase. The synthesized samples were fully characterized by FTIR, TG/DTA, XRD, SEM, EIS and chargeedischarge tests. Li1þxV3O8 material synthesized by tartaric acid assisted route and sintered at 450 C for 3 h shows best electro-chemical performance. It shows a high initial capacity of 249 mAh g1 and still reserves a discharge capacity of 260 mAh g1 after 50 cycles. Moreover, in the case of tartaric assisted products, no capacity decadence is observed in 50 cycles. XRD together with TG/DTA measurements reveal that compared with citric acid assisted products, the adoption of tartaric acid as chelating agent effectively lowers the crystallization temperature of amorphous Li1þxV3O8. Therefore, precursors obtained by tartaric acid route calcinated at 450 C for 3 h exhibit lower crystallinity and smaller grain size, which contributes to the better electrochemical performance of the cathode electrodes. From EIS measurements, the bulk resistance is reduced, which favors the intercalation and de-intercalation of lithium ions while cycling.
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Time-domain simulations of transient response in LiFePO4 cathode lithium ion batteries
Xiaoping Xu,Miao Shui,Weidong Zheng,Jie Shu,Lei Hui,Linxia Xu,Liangliang Cheng,Lin Feng,Yuanlong Ren 한국물리학회 2014 Current Applied Physics Vol.14 No.5
The time domain transients of batteries comprised of LiFePO4 cathode material exhibit large nonlinearity with the increasing discharging rates. Hence, the calculated overpotential transients match the experimental determined well only when the discharging current is low enough. The results of electrochemical impedance spectra at different OCV level indicate that the change of the parameters of equivalent circuit or even the circuit architecture are probably responsible for the large discrepancy between the predicted and the measured transient profiles. By taking the change of equivalent circuit model at high discharging current into consideration, we successfully simulate the time domain transients of polarization within the entire discharging current range. Also with the help of circuit analysis, the contribution of the ohmic resistance, charge transfer impedance and solid-state diffusion impedance to total polarization has been differentiated as a function of discharging time.
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Effect of Carboxylic Density on Sulfate Sensitivity of Polycarboxylate Superplasticizers
Yan He,Xiong Zhang,Tao Ji,Liangliang Shui 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.12
Effect of carboxylic density on sulfate sensitivity of polycarboxylate superplasticizers (PCEs) was analyzed. PCEs with different carboxylic densities were synthesized by changing molar ratio of isopropyl oxy polyethylene glycol (TPEG) macro-monomer to acrylic acid. The compositions of the self-synthesized PCEs were tested by 1H nuclear magnetic resonance spectroscopy (1H NMR), and the molecular weight was tested by size exclusion chromatography (SEC). Effects of sulfates on the adsorption-dispersing properties of PCEs and the surface charge of cement system in function of PCEs were investigated through total organic carbon (TOC) analyzer, mini-slump cone, and Zeta potential analyzer. Influence mechanisms of sulfates on the dispersing force of PCEs were evaluated through the competitive adsorption of sulfates, the aggregation of PCEs and the calcium ion concentration in pore solution. The results show that the competitive adsorption between PCE and SO42− impairs the dispersing capability of PCEs. In comparison with calcium sulfate, sodium sulfate has higher negative effects on the dispersing capability of PCEs. High amount of sulfate ions leads to the aggregation of PCEs, which further impairs the dispersing capability of PCEs. PCE with higher carboxylic density is less sensitive to the impact of sulfates.
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