Abstract
Combined with the constant demand for greater durability, safety and lower battery costs, a legitimate question is resurfacing : could aqueous systems be the replacement solution by 2022, given the predicted cost of €100 per kWh of stored energy for Li-ion ? This is what this lecture will attempt to answer. It will begin with a quick review of conventional aqueous batteries (Pb-acid, Ni-Cd, Ni-MeH and even Li(Na)-ion aqueous batteries), before focusing on Zn-MnO2 technology. The history of the Zn electrode, from the Volta battery to Leclanché's saline Zn-MnO2 and then alkaline batteries, will be retraced to put current research into perspective. Rechargeable Zn-MnO2 batteries, first brought to market by RAYOVAC in 1986, are enjoying a resurgence in popularity, with numerous papers in high-impact journals. But what's the real story ? What's new about ? The problem with this technology lies in mastering the Zn electrode, since whatever the pH, Zn reduces water →H2 (gas). This means we're in a situation where we need to avoid passivation and limit dissolution. Initially, low pH was favored (Lechanché-saline batteries), albeit with problems of high self-discharge, limited power and poor low-temperature performance. To get around these difficulties, researchers turned to basic pH (the alkaline batteries we use today), whose conversion to rechargeable batteries (RAYOVAC) was not very successful, due to limited cycling performance (< 20).
