A Weldable, Low‐Cost Graphite‐Based Electrode for Mn ²⁺ /MnO ₂ Redox Chemistry with High Volumetric Energy Density

ABSTRACT Aqueous rechargeable zinc–manganese batteries show considerable promise for large‐scale energy storage owing to their high safety, environmental friendliness, low cost, and competitive energy density. Recently, the Mn ² ⁺/MnO ₂ deposition–dissolution mechanism has gained attention because of its high specific capacity and cycling stability. High‐porosity, high‐surface area carbon felt has been widely employed as a cathode to facilitate Mn ² ⁺ transport and MnO ₂ deposition, it suffers from non‐weldability, high cost, as well as low volumetric energy density. Constructing coat‐able slurries offers an alternative. Naturally abundant, low‐cost flake graphite is an ideal building block for slurry‐processed, weldable cathodes. However, flake graphite cathodes suffer from ion‐channel blockage by MnO ₂ deposition due to their tightly packed structure. We found that incorporating spherical graphite (SG) expands the electrode framework, thereby creating additional mesopores and macropores. This structural modification enhances Mn ² ⁺ transport and effectively alleviates pore blockage. The optimized SG‐50 electrode sustained over 300 cycles at an areal capacity of 1.5 mAh cm ⁻² , with a coulombic efficiency of ∼94% and energy densities of 166 Wh L ⁻¹ . The estimated cost is 3.4 $/m ² , demonstrating a remarkable advantage over conventional carbon felt (60 $/m ² , 11 Wh L ⁻¹ ). This work provides a practical electrode design strategy for slurry‐coated, weldable cathodes in aqueous zinc–manganese systems involving dissolved redox species.