Carbon Nanotube Network Induces Porous Deposited MnO₂ for High-Areal Capacity Zn/Mn Batteries

Mn²⁺/MnO₂ aqueous battery is a promising candidate for large-scale energy storage owing to its feature of low-cost and abundant crustal reserves. However, the inherent MnO₂ shedding issue results in a limited areal capacity and poor cycling life, which prohibits its further commercialization. In this manuscript, it is revealed that the cause of shedding is the cracking of MnO₂ layer due to stress. To circumvent this challenge, carbon nanotubes framework is introduced on pristine carbon felt, which provides more deposition sites and induces the formation of a porous deposition layer. Compared to the dense deposition layer on pristine carbon felt, the porous structure can effectively avoid cracking and subsequent shedding issue. Moreover, the porous deposited layer is conducive to proton diffusion and rich in defects, which facilitates the subsequent dissolution reaction. As results, the assembled Zn/Mn battery demonstrates more than 200 cycles with the areal capacity of 15 mAh cm^-2 at 40 mA cm^-2. Even with a high areal capacity of 40 mAh cm^-2, it can still run for more than 60 cycles. This breakthrough paves a way toward practical manganese-based batteries, bringing us closer to achieve cost-effective batteries.