The use of low-cost and light-weight aluminium as current collectors in aqueous Li-ion batteries with water-based electrolytes is restricted by corrosion reactions caused by the aggressive ions in the aqueous environments. Here we report for the first time using highly corrosion-resistant Al foil with the chromate conversion coating (CCC Al) as current collector for cathodes in aqueous Li-ion batteries. Coating aluminium with chromium compounds is currently the most effective way to inhibit corrosion of aluminium and its alloys. The protection with the CCC is two-fold: (1) an impervious hydrated chromium(III) oxide serving as a physical barrier on the surface and (2) the chromium(VI) ions stored in the coating provide active corrosion protection.
We have experimentally demonstrated that CCC Al foil is resistant to corrosion when used as the current collector of LiMn2O4 electrodes. The cyclability of these electrodes are on par with or better than those observed for electrodes fabricated on stainless steel and titanium substrates. In contrast, electrodes fabricated on untreated Al foil saw serious corrosion of the substrate within the initial 10 cycles. Interestingly, CCC also effectively suppress oxygen evolution reaction at high potentials, leading to improved Coulombic efficiency of up to 99%. The increased overpotential for oxygen evolution was attributed to the occupation of active chemisorption sites and inhibition of electron transfer on the substrate surface by the chromium compounds. These results may open a new insight into the design of high performance and high-stability cathode electrodes for aqueous Li- and Na-ion batteries with a higher cell-level energy density.