The zinc-ion battery

04 February 2012 - Concepts

In the meanwhile (see earlier blog) Xu, Li, Du & Kang have a new battery design of their own they would like to call the zinc-ion battery (DOI). They combine discharge power with high capacitance. The cathode is manganese dioxide, with zinc as anode and aqueous zinc sulfate as the electrolyte. Zinc is oxidized to zinc(II) ions which then migrate to the MnO2 cathode. MnO2 has a peculiar crystal structure with long channels that can incorporate zinc ions by a process of intercalation (aka insertion). Zn2+ and MnO2 are then reduced to ZnMn2O4. In recharging mode the reverse reaction takes place and zinc migrates back where it came from (extraction).
Compare this to the Lithium-ion battery where lithium is doing all the shuttling between anode (graphite) and cathode (Lithium cobalt oxide). Lithium intercalates into the carbon electrode (see: Graphite intercalation compound). Another similar battery type is the Zinc-carbon battery where zinc is again oxidized to Zn2+ and manganese(IV) oxide is reduced to Manganese(III) oxide. According to the Wikipedia article the carbon present in this battery type just sits around and collects current but surely intercalation must be playing a role here as well.
The zinc-ion battery people find their new battery attractive because the electrolyte is non-corrosive (commercial batteries are either alkaline or acidic) and the other materials are nontoxic and low-cost. In one of those do-not-try-this-at-home experiments they demonstrate that the battery is also safe to use in a nailing experiment (no flash!) which must be what we think it is.