Bond‐Discretization in Nickel Oxide to Boost Capacity for Rechargeable Nickel─Zinc Batteries

Abstract Aqueous Ni─Zn batteries are highly attractive for grid‐scale energy storage due to their safety, low cost, and environmental friendliness. However, their energy density is limited by the underutilization of nickel‐based cathode materials. Here, a bond‐discretization strategy in NiO is developed to overcome this challenge. By designing a low‐symmetry crystallographic structure with a reduced Ni–Ni coordination number of 9, the NiO cathode achieves a near‐theoretical capacity for the one‐electron reaction. This structural modification leads to a discretization of Ni─O bonds and achieves a ratio of 50% for weak O─H bonds in the transformation product of Ni(OH) 2 , equal to the proportion (50%) of H atoms that needs to be detached from Ni(OH) 2 to NiOOH, which can realize nearly theoretical capacity for the one‐electron reaction. The bond‐discretization also promotes catalytic activity for oxygen evolution and oxygen reduction reactions, enabling the integration of Ni─Zn batteries with Zn‐air batteries. The low‐symmetry NiO cathode demonstrates high specific capacity, excellent rate capability, and superior cycling stability, with a full cell paired with a zinc anode achieving a specific energy of 459 Wh kg −1 at a specific power of 995.7 W kg −1 . This work provides a new bonding‐engineering strategy for constructing high‐performance energy storage devices.