Constructing sodium L-aspartate assisted N-doped carbon encapsulated hollow CoP spheres with enhanced electrochemical kinetics and its derived macroporous N-doped carbon foam for high-energy density hybrid supercapacitors

Herein, nitrogen-doped carbon (NC) encapsulated CoP hollow spheres are designed and prepared through a sodium L-aspartate assisted carbonization-oxidation-phosphorization route. Experimental and theoretical analysis unveil that the encapsulating of NC results in improved electric conductivity and enhanced electrolyte wettability. Particularly, an interfacial charge redistribution induces the establishment of local electric field at the CoP/NC interface, which leads to a decrease in surface OH – adsorption energies, an enhancement in charge transfer efficiency between OH – and active materials, and a reduction in OH – diffusion energy barriers. Thus, the CoP@NC electrode materials demonstrate enhanced capacity values (998C g −1 at 2 A g −1 and 640C g −1 at 20 A g −1 ) and cyclic stability (a capacity retention of 92.7 % after 5000 cycles). Moreover, three-dimensional macroporous N-doped carbon foams (MNCFs) are prepared through a facile and eco-friendly strategy using sodium L-aspartate as N-containing carbon source. Such MNCFs possess large surface area, enhanced electrical conductivity, and high-efficiency mass and ion transport, thus achieving specific capacitances of up to 426F g −1 at 1 A g −1 and 325F g −1 at 10 A g −1 . Furthermore, the fabricated CoP@NC||MNCFs hybrid supercapacitor device delivers an energy density of up to 75.1 Wh kg −1 at 800 W kg −1 , and demonstrates a capacity retention of 93.8 % after 5000 cycles. Our work not only provides valuable insights but also opens new avenues for designing and constructing advanced electrode materials for high-efficiency energy storage applications.