Design And Synthesize Of Self-supporting Multi-component Transition Metal Phosphides Electrodes For High-performance Supercapacitors

With substantial merits of fast charge/discharge rate,high power density,long lifespan,supercapacitors(SCs)have been widely recognized as promising candidates for energy storage devices,which are favorable for various applications such as high-power electronic devices,emergency power supplies and hybrid electric vehicles.The performance of SCs rely heavily on the electrode materials.Transition metal oxides/hydroxides as electrode materials for SCs have some limitations including poor electric conductivity,inferior cycle performance,and poor structural stability,impeding their practical application in SCs.Transition-metal phosphides have metalloid characteristics,low electronegativity and excellent electrical conductivity,and thus considered to be potential electrode candidates for high-performance hybrid SCs.Recently,it is well established that bimetallic nickel-cobalt phosphides exhibit higher electrical conductivity and better electrochemical activities than their corresponding single-composition cobalt phosphides and nickel phosphides,more favorable for the significant enhancement of electrochemical performance when used as electrodes for hybrid SCs.The main purpose of this paper is thus to implant different metal cations into single metal phosphide to form multi-component metal phosphides,which can achieve significant enhancement of electrochemical properties.The main contents are as follows:Anion and cation substitution is an effective way in modulating electrochemical properties of electrode materials to achieve enhanced performance.Herein,we report our finding in the fabrication of an advanced binder-free supercapacitor electrodes of hierarchical anion-(phosphorus-)and cation-(zinc-and nickel-)substituted cobalt oxides(denoted as ZnNiCo-P)architectures assembled from nanosheets grown directly on Ni foam.The substitution of anions and cations increases the complexity of the components,and the electrode material can have more redox active sites,thereby promoting the occurrence of the Faraday redox reaction.The binderless structure significantly increases the charge transfer rate,contributes to better rate performance and higher specific capacity,and thus the electrochemical performance is significantly improved.As a result,the as-prepared electrode manifests a markedly improved electrochemical performance with a high specific capacity of～958 C g-1 at 1 A g-1 and an outstanding rate capability(787 C g-1 at 20 A g-1)due to its compositional and structural advantages.Moreover,an aqueous hybrid SC based on self-supported ZnNiCo-P nanosheets electrode demonstrates a high energy density of 60.1 Wh kg-1 at a power density of 960 W kg-1,along with a superior cycling performance(89%of initial specific capacitance after 8,000 cycles at 10 A g-1 is retained).These findings offer insights into the rational design of transition metal compounds with multi-components and favorable architectures by manipulating the cations and anions of metal compounds for high-performance SCs.The design and fabrication and electrochemical properties of NiCoMn-P nanowire materials were investigated.Ni-and Mn-substituted cobalt hydroxides are obtained by a one-step hydrothermal method,and then phosphorus is introduced by low-temperature phosphating to obtain a NiCoMn-P nanowire electrode materials,which are directly grown on the nickel foam substrates.This structure gives the electrode material higher electrical conductivity and better mechanical properties due to the absence of binder addition.When tested in a three-electrode system,the as-prepared electrode can achieve a high specific capacity of 1388 C g-1 at a current density of 1.5 A g-1 and an excellent rate performance(880 C g-1 at 20 A g-1),superior to NiCo-P and Co-P nanowires electrodes.This electrode would be a potential electrode candidate for high-performance hybrid SCs.