Combining the conducting polymer polypyrrole (PPy) with layered molybdenum disulfide (MoS2) has proved to be an effective strategy to obtain a porous network flexible electrode. Various self-standing flexible electrodes with different structural parameters can be synthesized by controlling the preparation conditions. In this study, kinetics of the electrochemical behavior of PPy-MoS2 electrodes were systematically investigated by analyzing electrochemical impedance spectroscopy and cyclic voltammetry (CV) curves. The Trasatti analysis method was adopted to quantify the charge stored at the inner and outer surfaces during energy storage. Results show that the volumetric capacity of the porous network flexible electrodes varies with thickness. The difference in volumetric capacity derives from the kinetic control on the energy storage reaction. The dominant control in that reaction changes from surface control to diffusion control as the thickness of the flexible electrode increases from 5 to 60 μm. When surface control and diffusion control coexist at similar levels, the porous network flexible electrode yields its maximum capacity (68 mA·h/cm3 at 5 mV/s). Therefore, to maximize storage efficiency, the interaction between active materials and electrolyte ions should be carefully optimized when the porous network film is applied to a flexible electrode.
Keywords：porous network flexible electrode
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kinetic analysis
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surface control
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diffusion control
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storage efficiency
（1）MoS2纳米片的制备：0.3 g Na2MoO4与0.6 g TAA加入到20 mL EG和30 mL纯水的混合溶液中，搅拌0.5 h直至充分溶解，混合均匀。然后将反应前驱体转移至100 mL反应釜中，200 ℃加热24 h。待反应完成后，将反应物通过清水过滤清洗，得到MoS2纳米片水分散液。进行浓度标定后，继续加纯水将MoS2的浓度稀释至0.5 mg/mL。
Fig. 3
(a) Volumetric capacity of the porous network flexible electrodes at different sweep rates; (b) plot of volumetric capacity (5 mV/s) of the porous network flexible electrodes variation as a function of film density
Fig. 4
(a) Electrochemical impedance spectroscopy (EIS) and (b) the corresponding fitted curves of the porous network electrodes with thicknesses of 35 μm and 60 μm
图5
厚度分别为(a) 5 μm、(b) 7.5 μm、(c) 35 μm、(d) 50 μm和(e) 60 μm的多孔网络柔性电极的阳极、阴极峰电流与扫描速率之间的关系，其斜率为 b 值；(f) 不同厚度的多孔网络柔性电极的 b 值对比
Fig. 5
b-value determination of the peak anodic and cathodic currents of the porous network flexible electrodes with thicknesses of (a) 5 μm, (b) 7.5 μm, (c) 35 μm, (d) 50 μm, (e) 60 μm; and (f) b-values at different thicknesses
Fig. 6
Dependence of qv on v-1/2 of porous network film electrode with thicknesses of (a) 5μm, (c) 7.5 μm, and (e) 35 μm; Ratios of diffusion contribution and non-diffusion contribution of (b) 5μm, (d) 7.5 μm, and (f) 35 μm
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