Amino-functionalized carbon nanotubes stimulating γ-MnO2 to achieve high-performance zinc-ion batteries

With suitable operating voltage and high capacity, manganese dioxide (MnO2) shows great potential for the cathode of aqueous zinc ion batteries. However, its cycling stability is severely limited by the unstable host structure and inevitable dissolution of Mn2+. Herein, the amino-functionalized carbon nanotubes (MWCNTs-NH2) are introduced to construct the MWCNTs-NH2/γ-MnO2 nanocomposite (NCM) to significantly stimulate the cyclic stability of γ-MnO2. On the one hand, MWCNTs-NH2 can give impetus for stable integral structure and good overall electrical conductivity to γ-MnO2 through homogeneous three-dimensional mechanical and conductive networks. On the other hand, the amino groups of MWCNTs-NH2 can participate in the storage of Zn2+/H+ and, most importantly, boost the deposition of Mn2+ ions from the electrolyte to the cathode to inhibit the loss of active substance in the long-term cycle. Driven by these advantageous effects, the NCM cathode exhibits an ultra-high capacity of 417.9 mAh g−1 at 0.2 A g−1 and a long cycling life over 3500 cycles at 3.0 A g−1 with 91.4% capacity retention. This study reveals the importance of promoting Mn2+ deposition in Zn-MnO2 batteries and presents an effective strategy for achieving stable cycling of MnO2 cathodes.