Browsing by Author "Duan, Jia-Ning"

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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
;
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
;
Duan, Jia-Ning
;
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.