Paper-based, printed zinc–air battery

A flexible battery is printed on paper by screen-printing a zinc/carbon/polymer composite anode on one side of the sheet, polymerising a poly(3,4-ethylenedioxythiophene) (PEDOT) cathode on the other side of the sheet, and applying a lithium chloride electrolyte between the two electrodes. The PEDOT cathode is prepared by inkjet printing a pattern of iron(III)p-toluenesulfonate as a solution in butan-1-ol onto paper, followed by vapour phase polymerisation of the monomer. The electrolyte is prepared as a solution of lithium chloride and lithium hydroxide and also applied by inkjet printing on to paper, where it is absorbed into the sheet cross-section. Measurements on a zinc/carbon-PEDOT/air battery in a similar configuration on a polyethylene naphthalate substrate shows a discharge capacity of up to 1.4 mAh cm−2 for an initial load of 2.5 mg zinc, equivalent to almost 70% of the zinc content of the anode, which generates 0.8 V at a discharge current of 500 μA. By comparison, the performance of the paper-based battery is lower, with an open-circuit voltage of about 1.2 V and a discharge capacity of 0.5 mAh cm2. It appears that the paper/electrolyte combination has a limited ability to take up anode oxidation products before suffering a reduction in ionic mobility. The effects of different zinc/carbon/binder combinations, differences in application method for the zinc/carbon composite and various electrolyte compositions are discussed.