In situ Encapsulation Hollow FeP spheres Into High Yield 3D N, P-codoped Graphenic Framework as Advanced Anode Material for High-performance Supercapacitors

The performance of carbon-based materials as negative electrodes for supercapacitors can be effectively enhanced through the method like increasing the surface area and active sites as well as heteroatoms doping, while the limited capacitance caused by the surface adsorption mechanism restricts the further improvement of capacitance. Herein, we design hollow and porous FeP spheres (H-FeP) in-situ encapsulated into 3D honeycomb-like porous graphitic N, P-codoping carbon (PGNPC) by a unique post-annealing strategy. The post-annealing process acts as an efficient modification strategy in two aspects: the formation of a porous graphitic carbon framework during the catalytic reaction between iron oxide with carbon and the morphology changing from solid to hollow by introducing the Kirkendall diffusion process. With the synergetic effect of introducing hollow FeP into carbon, the N, P-codoping and 3D porous graphitic carbon framework ensure the as-prepared materials with enhanced performance for negative electrodes. Thus, H-FeP@PGNPC materials display outstanding specific capacitance (696 F g -1 ), high rate capacity and cycling stability. Using multi-shelled Mn 3 O 4 encapsulated in rGO as the positive electrode, the assembled asymmetric supercapacitor exhibits high specific capacitance and energy density with negligible capacity loss (retain 90% after 5000 cycles). • Novel in-situ encapsulated hollow FeP into N,P-codoped porous graphenic framework obtained through a high-yield process. • The catalytic reaction caused by the post-annealing process provides more active sites and extra pseudocapacitive contributions. • The porosity and hollow structure of FeP manipulated by Kirkendall effect. • N,P-codoped porous graphenic framework simultaneously acts as the buffer layer and expressway for electrons transport.