A New Design Strategy Enables High Mn-Utilization Rate in Aqueous Zinc-Manganese Batteries: Constructing Cathodic Local Mn-Rich Region

The deposition-dissolution mechanism with a two-electron transfer reaction endows aqueous Zn-Mn batteries with a desirable theoretical energy density. However, due to the limited solubility of traditional manganese-based materials and the competitive Mn shuttle behavior, the practical performance is unsatisfactory. Herein, by synergistically incorporating a novel Mn-rich Mn4N cathode with a plasma functionalized carbon nanotubes film (PCNT) interlayer, an aqueous Zn-Mn battery with a high Mn-utilization rate and high energy/power density is successfully developed. Specifically, the Mn4N cathode boasts high manganese content and dissolution activity, thereby offering a copious supply of Mn2+ ions for the battery system. The PCNT interlayer, with abundant micropore structures and functional groups, not only restrains the Mn2+ shuttle by entrapping the dissolved Mn2+ but also offers copious reaction sites, ensuring concentrating Mn2+ on the cathodic side and maximizing their contribution to the electrochemical reaction. Consequently, Mn4N-PCNT exhibits a low polarization voltage and superior Mn-utilization rate (64.8%). Without the MnSO4 additive, Mn4N-PCNT achieves an ultra-high energy density of 821.9 W h kg(-1) and remarkable long-term cycling stability (90% capacity retention over 9000 cycles). The delightful results demonstrate the practical application potential of Mn4N-PCNT and open up new avenues for the rational design of advanced Zn-Mn batteries.