3D nitrogen doped bimetallic phosphate superstructure for enhanced electrochemical energy storage

Phosphates have sparked significant interest as a promising candidate for cathode of supercapacitors due to their large channels, superior conductivity and charge storage capacity. Currently, nitrogen doping is widely employed to achieve customized properties of phosphates. Notably, the construction of bimetallic compounds will remarkably promote redox reactions and improve the cycle stability of the electrode through synergistic effects between the metals. Furthermore, compared to crystalline phases, amorphous materials have the potential to achieve increased specific capacity and cycle stability because of numerous active sites for redox reactions and higher mechanical strength. Herein, a nitrogen-doped bimetallic phosphate Co_0.5Ni_0.5-NPO·nH₂O is proposed, which is converted to the amorphous state (A-Co_0.5Ni_0.5-NPO) through the calcination process in an oxygen atmosphere. The electrode prepared by A-Co_0.5Ni_0.5-NPO achieves 134.98 mAh g⁻¹ (at 0.5 ​A ​g⁻¹) and outstanding rate capability. Furthermore, A-Co_0.5Ni_0.5-NPO//AC asymmetric supercapacitor (ASC) device with a specific capacity of 328 ​F ​g⁻¹ (at 0.5 ​A ​g⁻¹) and outstanding cycle stability (86.51 ​% retention after 3000 cycles at 3 ​A ​g⁻¹) is constructed. The research provides valuable insights for developing bimetallic phosphates as desirable electrode materials for enhanced energy storage systems.