Browsing by Author "Sun, Cui"

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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.
High reversible Li plating and stripping by in-situ construction a multifunctional lithium-pinned array
(2020-06-01)
Xu, Pan
;
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.
ZIF-8-Based Quasi-Solid-State Electrolyte for Lithium Batteries
(2019-12-18)
Sun, Cui
;
Zhang, Jin-hua
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Yuan, Xiang-fei
;
Duan, Jia-ning
;
Deng, Sheng-wen
The quasi-solid-state electrolytes (QSSEs) with an inorganic skeleton, a solid-liquid composite material combining their respective merits, exhibit high ionic conductivity and mechanical strength. However, most quasi-solid electrolytes prepared by immobilizing ionic liquid (IL) or organic liquid electrolyte in inorganic scaffold generally have poor interface compatibility and low lithium ion migration number, which limits its application. Herein, we design and prepare a ZIF-8-based QSSE (ZIF-8 QSSE) in which the ZIF-8 has a special cage structure and interaction with the guest electrolyte to form a composite electrolyte with good ionic conductivity about 1.05 x 10(-4) S cm(-1) and a higher lithium-ion transference number of about 0.52. With the ZIF-8 QSSE, a protype lithium battery coupled with LiCoO2 cathode shows good electrochemical performances with an initial discharge capacity of 135 mAh g(-1) at 50 mA g(-1) and a remaining capacity of 119 mAh g(-1) after 100 cycles, only 0.119% capacity degradation per cycle. It is worth noting that the ZIF-8-based QSSEs have good thermal stability up to 350 degrees C that does not show thermal runaway, which is significantly higher than that of a conventional organic liquid battery system.