Development of cathode material for the rechargeable Al-ion battery

Abstract

Many research activities focus on emergent energy storage technologies such as Na-ion, Zn-ion and Al-ion as alternative systems to established ones like lead acid, NiMH and Li-ion batteries. Function principle of an Al-ion cell in AlCl3containing electrolyte is more similar to that of a Li-metal one where Al dissolution/deposition occurs from/on Al foil during cell charge/discharge step leading to AlCl4- ion deintercalation/intercalation from the graphitic carbon counter electrode. The state-of-the art of Al-ion cell faces several challenges e.g. dendrites growth at the metal electrode and delamination of graphitic layers in pyrolytic graphite due to repetitive intercalation/deintercalation of large AlCl4- ions at positive electrode. In that context, search for more stable intercalation materials is of great importance for sustainable Al-ion battery development. In this work different resorcinol-formaldehyde-based carbon xerogels were successfully synthesized by varying resorcinol/catalyst ratio and their electrochemical performance as positive electrode material was evaluated in Al ion battery system. Carbon xerogels (CXG) were synthesized by polycondensation of resorcinol (R) with formaldehyde (F) in presence of sodium carbonate as catalyst (C). In order to find out optimal Resorcinol to catalyst ratio (R/C), fourteen different carbon xerogels (CXGs) samples (50 < R/C < 20.000) were produced. The synthesis mainly involved addition and condensation reaction between resorcinol and formaldehyde in presence of Na2CO3 followed by vacuum drying at 0.2 mbar and pyrolysis at 800ºC. Mass loss behavior of CXG with temperature is evaluate by Thermogravimetric analysis (TGA). The presence of disorder mode of C (sp3) and tangential mode of C (sp2)carbons was evidenced by emergence of both D band (1352 cm-1) and G band (1598 cm-1) in Raman spectra of all CXG samples. All CXG materials was found to be amorphous by X-ray diffraction pattern. and the surface morphology was demonstrated by Scanning Electron Microscopy (SEM). Further, the electrochemical performance of selected CXGs (R/C50, 500, 1000, 1500, 2000 & 2500) was studied in Al ion battery system on cathode side. With specific surface area of 720 m2g-1, Al-ion cell with R/C500 CXG cathode enabled a gravimetric discharge capacity of 88 mAhg-1 at 0.5 mA current with 85% coulombic efficiency. In addition, cells with R/C1000 and R/C1500 displayed gravimetric discharge capacity of 101 mAhg-1 and 96 mAhg-1 with 77% and 84% coulombic efficiency, respectively. To summarize, best results in terms of capacity were yielded by Al-ion cells with carbon xerogels R/C500, 1000 & 1500ratios which comparable to that obtained with natural graphite (NG).