Designing of Birnessite/Polyaniline Composite for Improving Cyclability as Cathode Material for Zinc Ion Batteries Based on Insights into the Reaction Mechanism

Abstract

AbstractAqueous Zn/MnO2 batteries (ZIBs) have high application value and development prospects in large‐scale energy storage. However, the cyclability of MnO2 is poor and its reaction mechanism is still controversy. Here, we revealed the zinc storage mechanism was Zn2+/H+ intercalation and conversion mechanism rather than Zn2+ and H+ co‐insertion reaction mechanism of birnessite (δ‐MnO2) electrode, and cycle fading was mainly caused by bad reversibility of ZnMn3O7 ⋅ 2H2O which was formed during conversion reactions by combining with X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and Raman spectroscopy analyses and so on. On this basis, appropriate polyaniline (PANI) was intercalated to the layer of δ‐MnO2 to stabilize its structure. The composite electrode exhibited higher capacity of 105 mAh/g after 250 cycles at 1 C rate, while δ‐MnO2 electrode had capacity of 86 mAh/g at same condition. Therefore, PANI intercalation can improve the cycle performance of the ZIBs to some extent. This work is believed to provide new strategy for further research on MnO2 cathode in ZIBs.