Browsing by Author "Dong, Quanfeng"

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A functionalized membrane for lithium-oxygen batteries to suppress the shuttle effect of redox mediators
(2019-06-21)
Chen, Zi-Fang
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Lin, Xiaodong
;
Xia, Hui
;
Hong, Yuhao
;
Liu, Xiaoyu
Redox mediators (RMs) are widely applied in lithium-oxygen (Li-O-2) batteries since they offer an alternative way to avoid the direct electrochemical oxidization of Li2O2 during charging, and thus greatly reduce the charge overpotential. Unfortunately, the defenseless Li-metal anode is severely corroded by the oxidized RMs shuttled from the cathode side, resulting in the low utilization of RMs and poor cycling stability. Herein, a functionalized double-guaranteed NPG membrane with electrostatic repulsion and steric hindrance characteristics is proposed to suppress the shuttle effect of LiI RM. Benefiting from the interaction between the O atoms in PEO and the sulfonic acid groups in Nafion and the two-dimensional skeleton structure of graphene, Nafion, PEO and graphene can couple with each other, forming a large network barrier with multi-functional properties. As expected, the LiI-based Li-O-2 batteries with the NPG membrane exhibited a smooth, iodine-free Li anode surface after many cycles and delivered an ultrahigh discharge capacity of similar to 26 917 mA h g(-1) at a current density of 200 mA g(-1) and ultralong cycle life (472 cycles) at 500 mA g(-1) with a cutoff capacity of 500 mA h g(-1), which are far better than that of the bare batteries.
A polyoxometalate-based polymer electrolyte with an improved electrode interface and ion conductivity for high-safety all-solid-state batteries
(2019-07-14)
Yuan, Xiangfei
;
Sun, Cui
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Duan, Jia-Ning
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Fan, Jingmin
;
Yuan, Ruming
Solid electrolytes have been considered as some of the most promising candidates for next generation lithium-based batteries because they eliminate the potential safety hazards of liquid organic electrolytes and further increase the energy density of batteries. However, inherent defects such as low conductivity and poor interface compatibility with electrodes critically hinder their extensive application. Polyoxometalate Li-7[V15O36(CO3)] (LVC) can dissociate Li+ in electrolyte and possesses a high diffusion coefficient, which constitute a pathway for Li+ transmission. Herein, a polyoxometalate-based polymer electrolyte (PPE) with an improved electrode interface and ion conductivity for high-safety all-solid-state batteries has been designed and synthesized to further enhance their electrochemistry behaviour. Compared with the routine PEO18LiTFSI electrolyte, the ionic conductivity was enhanced. Meanwhile, LVC can improve the interface compatibility between the electrode and electrolyte significantly, which promotes reaction kinetics and suppresses lithium dendrites against Li metal. When employed in LiFePO4|Li batteries, the specific discharge capacity after 180 cycles reached 148 mA h g(-1) with a high coulombic efficiency of around 99.9% at 0.5C. According to the result of ARC, LiFePO4|C batteries with PPEs are endowed with superior safety as the onset temperature of the self-heating process reaches up to 181.4 degrees C and the thermal runaway process does not occur within the range of 360 degrees C, indicating the potential of the PPE for high-safety all-solid-state batteries.
High reversible Li plating and stripping by in-situ construction a multifunctional lithium-pinned array
(2020-06-01)
Xu, Pan
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Lin, Xiaodong
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Hu, Xinyu
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Cui, Xueyang
;
Fan, Xiaoxiang
Lithium metal is the most promising anode candidate because of its ultrahigh theoretical specific capacity. Unfortunately, its high reactivity, uncontrolled dendrites, "dead lithium" formation, and infinite volume expansion hinder its commercial application. Herein, by in-situ constructing a multifunctional lithium-pinned array (m-LPA) endowed with functions of lithiophilicity, zoning effect and riveting effect on a surfacely phosphorized three-dimensional (3D) copper foam, a high reversible Li plating/stripping electrochemistry can be achieved. Benefiting from the m-LPA, lithium can uniformly plate/strip both on the surface and in the inner space of the 3D skeletons with improved morphology. Consequently, a high Coulombic efficiency (similar to 98.41%) could be achieved at 1 mA cm(-2) with 1 mA h cm(-2) for over 600 cycles (1200 h). Moreover, at a higher current density of 10 mA cm(-2) with 0.5 mA h cm(-2), a symmetric cell with m-LPA@Li electrode could still stably cycle for 900 cycles. Finally, a full cell coupled with LiFePO4 cathode displayed excellent rate performance with a lower overpotential. The conception and strategy of m-LPA, which were first proposed here, are a promising way to realize large-scale application of Li anode.
Ionic Liquids with Various Constituent Ions To Optimize Non-Enzymatic Electrochemical Detection Properties of Graphene Electrodes
(2019-10-07)
Xie, Jian-De
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Wang, Chueh-Han
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Patra, Jagabandhu
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Rath, Purna Chandra
;
Gandomi, Yasser Ashraf
Palladium (Pd) nanoparticles, ionic liquids (ILs), or both are integrated with graphene sheets to serve as an electrochemical sensor for detecting various bio-species. Ascorbic acid (AA), uric acid (UA), and dopamine (DA) are used as the model analytes. To assess the effects of the constituent ions of ILs on sensing properties, various ILs, namely, EMI-SCN, EMI-DCA, BMP-DCA, BMI-PF6, EMI-NTF2, and BMP-NTF2, are investigated. The results demonstrate that the graphene/IL electrode shows superior detection sensitivity compared to those of the graphene/Pd and graphene/Pd/IL electrodes. Interestingly, the IL anions are found to play a crucial role in sensing performance. Angle-resolved X-ray photoelectron spectroscopy reveals that graphene can create an aligned cation/anion orientation in the adsorbed IL film, with the anions preferentially occupying the topmost surface, thus dominating the interaction with analytes. The graphene/EMI-SCN electrode shows the highest sensitivity among the electrodes, 1.49 mu A mu M-1 cm(-2), and a detection limit of 0.11 mu M toward DA. Even with large excesses of AA and UA, the concentration of DA can be effectively detected.