Electrochemically activated nickel-cobalt double hydroxide for aqueous ammonium-zinc hybrid battery

Aqueous rechargeable ammoniumion (NH4+) batteries (AAlBs) with ammonium ions as charge carriers possess many advantages, yet the relatively low discharge capacities (e.g., < 200 mAh(.)g(-1)) of the reported NH4+ host materials hinder the development of AAlBs. Herein, we study the NH4+ storage properties of an electrochemically activated NiCo double hydroxide (A-NiCo-DH) in neutral ammonium acetate electrolyte for the first time. The activation process extracts the interlayer anions (NO3-) from the host material, providing additional cation accommodation sites for charge storage. The introduced H vacancies in A-NiCo-DH could activate the 0 sites, leading to the enhanced cation adsorption capability for the electrode. Therefore, A-NiCo-DH exhibits a high discharge capacity of 280.6 mAh(.)g(-1) at 0.72 A(.)g(-1) with good rate capability. Spectroscopy studies suggest A-NiCo-DH experiences a NH4+/H+ coinsertion mechanism. A NH4+-Zn hybrid cell is assembled using A-NiCo-DH as the cathode and Zn foil as the anode, respectively. The device delivers an energy density of 306 Wh(.)kg(-1) at the power density of 745.8 W(.)kg(-1) (based on the active mass of A-NiCo-DH). This work provides a new NH4+ storage material and would push forward the development of aqueous NH4+-based batteries.