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Aqueous rechargeable ammonium-ion (NH4+) batteries (AAIBs) 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 AAIBs. 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 O 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.
Y. S. acknowledges the financial support from the National Natural Science Foundation of China (No. 51804066) and the Fundamental Research Funds for the Central Universities (No. N2205003). X. X. L. acknowledges the support by the 111 Project (B16009) and the financial support from LiaoNing Science and Technology Development Foundation Guided by Central Government (No. 2021JH6/10500139). The authors thank the Analytical and Testing Center of Northeastern University for TEM data acquisition.