Construction of CNT@K+- doped δ-MnO2 by "killing two birds with one stone" strategy toward high-rate and stable aqueous zinc-ion batteries

Layered manganese dioxide (delta-MnO2) has garnered significant attention due to its exceptional potential as a cathode material in aqueous zinc-ion batteries. Nevertheless, the widespread adoption of delta-MnO2 in commercial applications remains hindered by challenges such as insufficient electrical conductivity and instability in its structural integrity throughout charge and discharge cycles. In this study, using KOH solution as the etchant, CNT@K+-doped delta-MnO2 (CNT@KMO) was successfully fabricated, where the CNTs enhance the transport of electron by establishing a conductive network, while the K+ from KOH serves as pillars to intercalate into the MnO2 interlayer, giving rise to a more stable structure. Consequently, the CNT@KMO electrode demonstrates an ideal reversible specific capacity of 306.1 mA h g(-1) after 150 cycles at a current density of 0.5 A g(-1) in a 2 M ZnSO4+0.2 M MnSO4 aqueous electrolyte. Furthermore, the electrode exhibits a respectable specific capacity of 100.8 mA h g(-1) with a coulombic efficiency close to 100% at a current density of 5 A g(-1) and exceptional cycling stability more than 2000 cycles. This novel synthesis strategy could pave the way for superior aqueous zinc ion batteries.