The use of some sulfonic acids for improving aluminum current collector resistance

The corrosion behavior of aluminum current collectors in the standby and high-load modes was investigated by simulating via immersion and anodization experiments in electrolyte environments. The immersion experiments were carried out using aluminum alloy (AA5754) in camphorsulfonic (CSA), p-toluenesulfonic (PTSA), trifluoromethanesulfonic (TFMSA), and fluorosulfonic (FSA) acid solutions, and the results were compared with those of H2SO4 and methanesulfonic acid (MSA). Corrosion resistance increased in the order of FSA, MSA, TFMSA, PTSA, H2SO4, and CSA. Thin-film XRD and XPS results revealed sulfonic acid adsorption to Al2O3. From AFM, the least rough and highest crystalline oxide layer was obtained with CSA, while FSA yielded the opposite. In addition, AA5754 was anodized in 0.1 M CSA, PTSA, and H2SO4 solutions, and its corrosion behavior was examined. R-ct values were about one hundred times higher than in the immersion experiments; besides, less rough and thicker layers were obtained on the surface owing to the controlled dissolution. The mixture of CSA: H2SO4 (1:1) was used as an anodization solution, and the maximum resistance (5652 Omega.cm(2)) was obtained at 20 V, which was a better corrosion behavior according to individual electrolytes. This could be due to the optimum combination of the high acidity of H2SO4 and the ability of CSA to block the surface sites thanks to its larger cyclic structure. Finally, a symmetric supercapacitor cell prepared using a carbon-coated Al current collector in PVA/H2SO4:CSA gel electrolyte was tested by cyclic voltammetry and GCD. The cell provided 26 Wh.kg(-1) and 10.2 kW.kg(-1) with 89% efficiency and 64% retention after 5000 cycles over a wide potential range of 1.6 V, exhibiting better capacitive performance than the gel electrolyte without CSA. This increase could be because CSA contributes to the growth of the protective aluminum oxide layer as an anionic surfactant.