Electrode Composite for Flexible Zinc–Manganese Dioxide Batteries through In Situ Polymerization of Polymer Hydrogel

Abstract

It remains important to maximize energy density of wearable batteries. In addition, such batteries should be compliant, safe, and environmentally sustainable. Intrinsically safe zinc–manganese dioxide (Zn/MnO2) batteries are great candidates for powering wearables. However, achieving flexibility of these systems is hindered by the absence of a binder that ensures mechanical integrity of the MnO2 electrode composite. Herein, a unique approach to fabricate a mechanically robust MnO2 electrode is presented. Polyvinyl alcohol (PVA)/polyacrylic acid (PAA) gel cross-linked in situ via thermal treatment is used as a binder for the electrode. Furthermore, energy density and rate capability of the printed battery electrodes are improved by replacing graphite with single-walled carbon nanotubes (CNTs). The batteries retain 93% capacity when the discharge rate is increased from C/10 to C/3, as well as 97% of their capacity after being flexed. In contrast, batteries based on conventional composition retain 60% and 23% of the capacity, respectively. Finally, the battery with the modified electrode has high areal energy density of 4.8 mWh cm−2 and volumetric energy density of 320 mWh cm−3.