An Universal Strategy Toward Ultra-Long Cycle and Superior Rate of Battery-Type Supercapacitor Electrode: In-Situ Built Bonded Interface Induced by Defect Engineering

Abstract

Holding ultralong cycle life and superior rate capability with high specific capacity is an inevitable requirement for the practical applications of transition metal compounds battery-type supercapacitor electrode materials. In this paper, a novel class of transition metal phosphide (TMP) nanostructures evenly bonded on N/P co-doped graphene nanotubes (N/P-GNTs@b-TMP) is firstly built via one-step in-situ growth procedure. The N, P elements as substitutions of C in GNTs skeleton introduce rich electronic centers, further change the surface electronic structures of the skeleton, inducing the TMPs to anchor the surface of N/P-GNTs through metal-N and metal-P bonds, which is demonstrated by the characterizations and Density functional theory (DFT) calculation.  Moreover, ex-situ impedance and capacitive/diffusion control analysis suggest the fast ions diffusion behavior and reaction kinetics. Benefiting from the unique architecture, the achieved N/P-GNTs@b-NiCoP positive electrode possesses high specific capacity of 250 mAh g-1 (1800 F g-1) at 2 A g-1 and 166 mAh g-1 (1200 F g-1) at 50 A g-1. Meanwhile, the N/P-GNTs@b-Fe2NiP and N/P-GNTs@b-FeCoP negative electrodes constructed by the same approach can also own a high specific capacity of 151.9, 159.7 mAh g-1 (547, 575 F g-1) at 1A g-1 and 63.6, 73.6 mAh g-1 (229, 265 F g-1) at 50 A g-1, respectively. In addition, an asymmetric supercapacitor (ASC) using the achieved N/P-GNTs@b-NiCoP as electrode expresses a remarkable energy density of 69.5 Wh kg-1 and cycling stability. This work provides an innovative structural design strategy for obtaining battery-type supercapacitor electrode materials with commercial application prospects.

Keywords: chemically bonded interface, battery-type TMP electrode materials, ultra-long cycle, superior rate, asymmetric supercapacitor