Magnesium - Preparation And Properties Of Polyaniline Battery

With the development of the national economy and increasing demand for energy in recent years, how to develop the secondary battery having the characteristics of high energy density, economy and environmental friendly has been one of the biggest challenges facing most electrochemical workers. Therefore, it will have important theoretical significance and good application prospects to study the new type magensium-polyaniline battery with lower cost and greater safety.In this paper, polyaniline was first synthesized by chemical oxidation and then activated carbon was used to adsorb the undesirable organics of the polyaniline wastewater during the synthesis progress. Various analysis techniques including Fourier transform infrared (FT-IR) spectrometer, UV-visible (UV) spectrometer, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were used to study the property of synthesized polyaniline. Besides, UV spectrophotometry was used to investigate the optimal activated carbon adsorption treatment conditions and the wastewater after adsorption treatment was neutralized by cheap calcium carbonate. Experimental results showed that the structure of polyaniline was stable and the loose and porous structure was helpful to the doping and de-doping of anions as well as electron transfer. Therefore, polyaniline would be a suitable cathode material for the secondary battery. Activated carbon could effectively adsorb the organics in the polyaniline wastewater and the removal percentage could be91%on conditions of16.0g L-1activated carbon, adsorption time30min and pH1.05. The wastewater after adsorption treatment turned colorness and8g L-1calcium carbonate could neutralize the wastewater after activated carbon adsorption treatment to pH6.70.The room temperature ionic liquid1-ethyl-3-methylimidazolium ethyl sulfate (EMIES) was synthesized and characterized by FT-IR spectrometer, UV spectrometer, nuclear magnetic resonance spectrometer (NMR) and cyclic voltammetry (CV); then a preliminary study of the electrochemical property of magnesium electrode and polyaniline electrode was conducted in the ionic liquid-magnesium salt electrolyte. Results showed that the purity of EMIES was high and EMIES had a wide electrochemical window (about3.8V with glassy carbon electrode as the working electrode). In the ionic liquid-magnesium salt electrolyte, especially in0.01M MgSO4-EMIES, magnesium could have overpotential deposition and the depositon surface was uniform and smooth without dendrite; polyaniline showed good oxidation and reduction reversibility and wide redox region (about1.45V) in the magnesium-polyaniline three electrode system. On the basis of above study, the appropriate concentration of MgSO4-EMIES electrolyte was investigated and the detailed electrochemical property of magnesium electrode and polyaniline electrode was studied at the optimal concentration. Results showed that magnesium had high dissolution and deposition reversibility and polyaniline showed good oxidation and reduction reversibility in0.025M MgSO4-EMIES. In addition, electrochemical polymerized polyaniline would be used for the subsequent electrochemical studies, because it had higher purity and more uniform chain length than the chemical one. At current density of0.05mA cm-2, polyaniline electrode had an average discharge potential of0.32V (vs. SCE) and the discharge capacity was more than100mAh g-1at film thickness of0.66μm. Finally, the charge and discharge characteristics of the magnesium-polyaniline battery were investigated in0.025M MgSO4-EMIES. The effect of polyaniline film thickness on the discharge capacity of the magnesium-polyaniline battery was discussed in detail. The study demonstrated that the magnesium-polyaniline battery had longer discharge time and higher discharge capacity at lower current density. In the current density range0.05-0.46mA cm-2, the discharge capacity was115-62mAh g-1and the average discharge potential was2.10-1.90V. At0.05mA cm-2, the charge-discharge curves in the first5cycles had good repeatability and the magnesium-polyaniline battery had good cycling performance, where the coulombic efficiency of the60th cycle could be nearly95%. The magnesium-polyaniline battery would have higher discharge capacity at thinner polyaniline film, in which the discharge capacity decreases from186mAh g-1to72mAh g-1in the film thickness range of0.45～1.75μm.