Molecular engineering of self-assembled monolayers for highly utilized Zn anodes

Abstract

Stabilizing the Zn anode under high utilization rates is highly applauded yet very challenging in aqueous Zn batteries. Here, we rationally design a zincophilic short-chain aromatic molecule, 4-mercaptopyridine (4Mpy), to construct self-assembled monolayers (SAMs) on a copper substrate to achieve highly utilized Zn anodes. We reveal that 4Mpy could be firmly bound on the Cu substrate via Cu–S bond to form compact and uniform SAMs, which could effectively isolate the water on the electrode surface and thus eliminate the water-related side reactions. In addition, the short-chain aromatic ring structure of 4Mpy could not only ensure the ordered arrangement of zincophilic pyridine N but also facilitate charge transfer, thus enabling uniform and rapid Zn deposition. Consequently, the Zn/4Mpy/Cu electrode not only enables the symmetric cell to stably cycle for over 180 ​h at 10 ​mA ​cm⁻² under a high depth-of-discharge of 90%, but also allows the MnO₂-paired pouch cell to survive for 100 cycles under a high Zn utilization rate of 78.8%. An anode-free 4Mpy/Cu||graphite cell also operates for 150 cycles without obvious capacity fading at 0.1 ​A ​g⁻¹. This control of interfacial chemistry via SAMs to achieve high utilization rates of metal anodes provides a new paradigm for developing high-energy metal-based batteries.