Lignin-Derived N,S-Co-Doped Carbon Dots Enable Improved Mn₂O₃ Cathodes for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) are highly promising for large-scale energy storage applications owing to their distinct merits, such as exceptional safety, abundant zinc reserves, high ionic conductivity, and facile manufacturing. Featuring natural abundance, low cost, environmental benignity, and high theoretical specific capacity, Mn₂O₃ has emerged as one of the most competitive cathode candidates for AZIBs. However, the low electrical conductivity of Mn₂O₃ impedes electron transport within the electrode, leading to significant polarization during charging and discharging and poor rate performance. Therefore, this study focuses on Mn₂O₃, and combines it with lignin-derived N,S-co-doped carbon dots (NS-CDs). Through a composite modification strategy, efficient conductive pathways are constructed and the structure of Mn₂O₃ is stabilized simultaneously, thereby effectively enhancing the electrical conductivity of the modified cathode. The incorporation of NS-CDs improves the high-rate response of the Mn₂O₃ cathode, with the optimized composite retaining capacity stability at 5 A g^-1. At 0.2 A g^-1, the specific capacity reaches 174 mAh g^-1, and at a current density of 1 A g^-1, the material can sustain 1000 cycles. These results highlight biomass-derived carbon dots as a viable interfacial modifier for Mn-based AZIB cathodes.