Electrochemical Characterization of Gel Electrolytes for Aqueous Lithium-Ion Batteries

The augmentation of the operating voltage span of water-based electrolytes would render aqueous lithium-ion batteries nearer to real application, as a substitute for high-power lithium-ion batteries. The possibility for improving the electrochemical stability window of the water-based solutions 2M Li2SO4 and 4M LiClO4 by adding different gelling agents is investigated here by addressing the cathodic and anodic domains of the stability window separately. The conductivity of all electrolytes and the corresponding activity of water are determined using electrochemical impedance spectroscopy and mass spectrometry, respectively. The stability window is assessed by alternating high (+/- 100Acm(-2)) and low (+/- 10Acm(-2)) current densities in a chronopotentiometric mode, thereby simulating the self-discharge performance of batteries under operating conditions. In the case of Li2SO4-based solutions, the addition of gelling agents (carboxymethyl cellulose and agar) results in the enlargement of the stability window and in the reduction of the electrolyte ionic conductivity.