Preparation Of The PAAS-based Gel Electrolyte And Its Application To The Alkaline Secondary Batteries

In recent years, with the requirements of environment protection and urgent needs for high performance batteries, alkaline secondary battery, especially MH/Ni and Zn/Ni batteries, because of their high energy density, high power density, and no environmental pollution, are quickly become the hotspot of numerous research workers. At present, MH/Ni and Zn/Ni batteries generally use KOH solution as electrolyte, however, due to the liquid electrolyte is easy to dry up, leak, corrosive on the electrodes, and with narrow using temperature range, people are trying to use other types of electrolytes to replace KOH solution. As a result of easy synthesis, high room temperature conductivity, and polymer matrix material is rich, lower-cost of alkaline polymer gel electrolyte, it has entered into the vision of the research workers. Among the studied polymer electrolytes, polyacrylic acid polymer electrolyte has owned the highest conductivity, but the mechanical performance is poor because of the high water content. In view of insufficient mechanical properties of PAAS electrolyte, this paper considered adding nano inorganic salt lithium magnesium silicate(MLS), and prepared the MLS-PAAS-KOH-H2O gel electrolyte, and also assembled the MH/Ni and Zn/Ni batteries to study the battery performance.Firstly, the alkaline gel electrolyte was prepared from MLS, PAAS and KOH by blending method. The samples were studied by AC impedance techniques, cyclic voltammetry. The research results showed that at room temperature, the conductivity of MLS-PAAS-KOH-H2O gel electrolyte was the same order as that of the6mol/L KOH solution; Over the temperature range of290K to330K, the relation between conductivity of gel electrolyte and temperature accorded with the Arrhenius equation, and the calculated conductivity activation energy was about13.55kJ·mol-1; The CV curve showed that the MLS/PAAS/KOH/H2O gel electrolyte had an electrochemical stable window of about1.6V.Secondly, MH/Ni batteries assembled with MLS-PAAS-KOH-H2O gel electrolyte were studied. When discharged at0.5C,1C,2C rates, the discharge capacity of gel electrolyte batteries was similar to each other; The voltage drop between gel electrolyte and KOH solution electrolyte batteries mainly originated from the interface resistance between gel electrolytes and electrodes; Compared with6mol/L KOH solution electrolyte batteries, the gel electrolyte batteries owned better cycle performance and charge retention; Tafel polarization tests indicated that the corrosion resistance of alloy electrodes in the gel electrolyte was better; EIS test manifested that alloy electrodes in gel electrolyte had lower electrochemical impedance.Finally, Zn/Ni batteries assembled with MLS-PAAS-KOH-H2O gel electrolyte were studied. As a result of the gel electrolyte could suppress the dissolution and diffusion of Zn and [Zn(OH)4]2-, weakening the corrosion, shape change, self-discharge and formation of zinc dendrite of zinc electrodes, the gel electrolyte batteries owned favorable charge-discharge, cycle performance and charge retention; Rate discharge tests showed that, at0.2C,0.5C and1C discharge rates, the performance of gel electrolyte batteries were similar to alkaline liquor electrolyte batteries, but at2C rate discharge, the performance of gel electrolyte batteries were worse than alkaline liquor electrolyte batteries; Tafel polarization tests indicated that the corrosion resistance of zinc electrodes in the gel electrolyte was better; CV test showed that the zinc electrodes in gel electrolyte had better reversible and discharge capacity; EIS test manifested that the zinc electrodes in gel electrolyte had slightly higher ohms impedance Rn, and lower electrochemical impedance Rct.