Polyaniline interface engineering-enabled oxygen vacancy-enriched NiCo-LDHs for ammonium-ion supercapacitors†

Aqueous ammonium-ion supercapacitors have attracted much attention due to their high safety and economic and environmental advantages, but the development of high-performance electrode materials for NH₄⁺ storage has lagged behind that of other carriers. Herein, we designed an organic–inorganic hybrid material (LDH-Vo@PANI) as the cathode for efficient NH₄⁺ storage via interface engineering and defect engineering. The polyaniline coating enhanced the structural stability of NiCo-LDHs by constructing Ni/Co–N bonds, which inhibited their dissolution during charging and discharging. The oxygen vacancies effectively buffered the electrostatic interaction between NH₄⁺ and NiCo-LDHs, thereby increasing the diffusion rate of NH₄⁺. Furthermore, density functional theory (DFT) calculations strongly demonstrate the positive effects of PANI coating and oxygen vacancies on the NH₄⁺ adsorption capacity and conductive properties of the electrode material. Therefore, the LDH-Vo@PANI exhibits an area capacitance of up to 2091 mF cm⁻² at 1 mA cm⁻² while maintaining a high rate performance of 55.8%. The assembled supercapacitor exhibits an ultrahigh energy density of 75 W h kg⁻¹ and a power density of 788 W kg⁻¹ and retains 99.48% of its initial capacitance and 100% Coulomb efficiency after 10 000 cycles. This work provides a strategy with universal applicability for the development of high-performance ammonium storage electrode materials.