Novel Electrospun Anatase/Poly(3,4-Ethylenedioxythiophene) Polystyrene Sulfonate-based Li-ion Battery Anodes and their Electrochemical Performances
Charkhesht, Vahid (2020) Novel Electrospun Anatase/Poly(3,4-Ethylenedioxythiophene) Polystyrene Sulfonate-based Li-ion Battery Anodes and their Electrochemical Performances. [Thesis]
Among the common batteries, LIBs as one of the pioneers in rechargeable batteries has become an intrinsic part of almost all the electronic devises. However, there are lots of rooms for improvement in terms of safety, working life, and charging pace. Using fibrous electrodes can improve the electrochemical behavior thanks to the enhancement of connection of the electrolyte with active material by increasing voids to facilitate the Li+ transference. Electrospining as a simple, scalable, and cost-effective technique can build up the fibrous electrodes used in LIBs. In this study, for the first time, highly conductive poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) polymer was used as a carrier of electrospun TiO2/CB-based anode. Due to the low viscosity of PEDOT:PSS solution, another carrier polymer with high molecular weight, PEO, was added to electrospinning ink to increase the viscosity and make the electrospinning process practical. A systematic and laborious optimizing work was performed to achieve the homogeneous ink composition and finally fibers with homogeneous particle distribution. The parameters include sonication type and time, PEO/PEDOT:PSS ratio, ink solid ratio, dispersants ratio (DMF/Water), PEO polymer ratio, and PEO molecular weight besides the operational parameters like operational voltage, needle to collector distant, polymer feeding rate and relative humidity. TGA, XRD, RAMAN, FTIR, and FE-SEM techniques were used to characterize the electrodes. After electrode fabrication, electrochemical tests including galvanostatic charge/discharge, cyclic voltammetry, and electrochemical impedance spectroscopy were performed. Presence of PEDOT:PSS assists the anode performance by: i) improving the conductivity and ii) increasing capacity due to the electrochemical activity of the polymer. Not only the achieved areal capacity (1.67 mAh.cm-2) was comparable to the other studies, but also the gravimetric capacity (300 mAh.g-1) was much higher than similar studies. These results are very promising for the next generation electrospun LIB electrodes fabricated using PEDOT: PSS as a binder/carrier.
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