Cu2+ intercalation bolstering the rate capability of δ-MnO2 cathode for aqueous zinc-ion battery

Cost-effective manganese dioxide (MnO 2 ) promises the economical advantage of rechargeable aqueous zinc-ion batteries (ZIBs) but suffers its low electrical conductivity, the irreversibility of structural transformations during electrochemical reactions, and the slow kinetics of the reactions. This study employs a one-step co-precipitation technique to synthesize Cu 2+ intercalated δ-MnO 2 nanoflower. The intercalation of Cu 2+ not only enlarges the interlayer spacing through the interaction with water molecules, but also strengthens the interlayer structure with Cu 2+ as the pillars, improves the ionic conductivity, and enhances the rate capability of δ-MnO 2 . It is attributed to the co-insertion/extraction mechanism of Zn 2+ /H + . Therefore, the Cu 2+ intercalation δ-MnO 2 developed for ZIBs demonstrates a high specific capacity (300 mAh g −1 at 0.1 A g −1 ), long cycling stability (179 mAh g −1 until 2000 cycles at 1 A g −1 89.9 % capacity retention), and superior rate capability (195 mAh g −1 at 1 A g −1 ). Meanwhile, the flexible ZIBs assembled with this cathode material have wider commercial applicability.