Operando Synchrotron XRD研究电化学还原焦磷酸银铁（Ag 7 Fe 3（P 2 O 7）4）时金属银的形成,The Journal of Physical Chemistry C

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Operando Synchrotron XRD研究电化学还原焦磷酸银铁（Ag ₇ Fe ₃（P ₂ O ₇）₄）时金属银的形成
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2017-05-11 00:00:00 , DOI: 10.1021/acs.jpcc.7b03723
Yiman Zhang ₁ , Kevin C. Kirshenbaum ₂ , Amy C. Marschilok _{1,

3} , Esther S. Takeuchi _{1,

2,

3} , Kenneth J. Takeuchi _{1,

3}

Affiliation

研究了Ag ₇ Fe ₃（P ₂ O ₇）_4的电化学还原和锂化形成导电金属银的过程。交流阻抗谱测量显示在还原中的一个电子转移（EE），这是与由既证明一个银金属导电网络的形成重合在电荷转移电阻的34％的下降易地和operando X射线衍射。从操作XRD得出的Ag金属形成的定量评估表明，在最初的3ee中仅还原了Ag ⁺离子，随后同时还原了Ag ⁺和Fe下一个5ee（从3ee到8ee）减少³⁺，最终减少剩余的Ag ⁺。扫描电子显微镜图像显示，具有较高放电深度的Ag颗粒之间和之中的Ag金属微晶尺寸较小，最近邻居距离较短。进行了高速率间歇性脉动放电测试，该单元在完全放电期间会发出12个总脉冲，以探测Ag金属形成对Li / Ag ₇ Fe ₃（P ₂ O ₇）_4的影响细胞电化学。欧姆电阻源自每个脉冲的电压降。最初的电阻为65Ω，在4.5 ee放电时达到最小的26Ω，在降低7.0 ee后稳定在35Ω。初始的Ag减少是通过两者的降低表明所述导电网络形成更显著- [R _CT和欧姆电阻，这有利于电池的功率输出为高。

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Operando Synchrotron XRD Investigation of Silver Metal Formation upon Electrochemical Reduction of Silver Iron Pyrophosphate (Ag7Fe3(P2O7)4)

The formation of conductive metallic silver upon electrochemical reduction and lithiation of Ag₇Fe₃(P₂O₇)₄ is investigated. Alternating current impedance spectroscopy measurements show a 34% decrease in charge transfer resistance upon one electron equivalent (ee) of reduction, which is coincident with the formation of a Ag metal conductive network evidenced by both ex situ and operando X-ray diffraction. Quantitative assessment of Ag metal formation derived from operando XRD shows that only Ag⁺ ions are reduced during the first 3ee, followed by simultaneous reduction of Ag⁺ and Fe³⁺ reduction for the next 5ee (3ee to 8ee), culminating in reduction of the remaining Ag⁺. Scanning electron microscopy images show smaller Ag metal crystallite size and shorter nearest neighbor distance between and among Ag particles with higher depth of discharge. A high rate intermittent pulsatile discharge test is conducted where the cell delivers 12 total pulses during full discharge to probe the effect of Ag metal formation on the Li/Ag₇Fe₃(P₂O₇)₄ cell electrochemistry. The Ohmic resistance is derived from the voltage drop of each pulse. The resistance is 65 Ω initially, reaches its minimum of 26 Ω at 4.5 ee discharge, and levels off at 35 Ω after 7.0 ee reduction. The initial Ag reduction is more significant for the conductive network formation indicated by the decrease of both R_ct and Ohmic resistance, which facilitates the high power output of the cell.

更新日期：2017-05-25

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