Ball-Milled Carbon Nano-Onions as High-Performance Conductive Additives for Zinc-Ion Batteries
Ramu Banavath, Yufan Zhang, Md Zahidul Islam, Smita S. Dasari, Huaixuan Cao, Brian R. Stepp, Navid Attarzadeh, Rajkumar Parso, Stephnie Peat, Joseph V. Kosmoski, Evan C. Johnson, Micah J. GreenAbstract
Manganese dioxide (MnO2) cathodes for aqueous zinc-ion batteries (ZIBs) offer high capacity but suffer from poor electrical conductivity and sluggish kinetics. This study examines ball-milled carbon nano-onions (CNO-BMs) as high-performance conductive additives to address these challenges. We investigated the structural evolution of CNOs ball-milled for 2, 7, and 20 days. Results show that extended milling disrupts quaternary agglomerates (∼10 μm), reducing particle size to 280 nm while enhancing film conductivity from 3 S m−1 to 20 S m−1. When employed in MnO2 cathodes, the 20 day milled CNOs (CNO-BM20) outperform traditional Super P as a conductive additive. The CNO-BM20 cathode achieves a reversible capacity of 200 mAh g−1 at 0.1 A g−1, which is double that of Super P, and retains 80% of its capacity after 2000 cycles, significantly exceeding that of its commercial counterpart. Electrochemical analysis shows that the CNO network lowers charge-transfer resistance and exhibits higher GITT-derived apparent Zn2+ chemical diffusivity than Super P. These findings demonstrate that structurally engineered CNOs effectively unlock the potential of MnO2 for high-rate, durable aqueous energy storage.