Synthesis And Supercapacitor Properties Of High Entropy Oxides Nanopowders

Supercapacitors have wide applications in area of energy storage because of their high power density and long cycle life.To improve their performance,it is crucial to develop high-performance electrode materials.In recent years,high entropy has emerged as a promising material design strategy,expanding the possibilities for electrochemical energy storage materials.This approach is expected to yield exceptional electrochemical energy storage properties,providing new avenues for supercapacitor development.This paper describes a simple process for producing high-entropy oxide nanopowders and investigating their potential use in supercapacitors.(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)₃O₄high-entropy nanopowders were synthesized via a co-precipitation method,and the effect of preparation parameters on the phase,particle size of high-entropy nanopowders and its supercapacitor performance was explored.The single-phase(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)₃O₄high-entropy powder with spinel structure can be obtained by calcining the precipitate at 500-700℃for 2 h.Higher calcination temperature is beneficial to the formation of spinel structured high entropy phase.The prepared high-entropy oxide powder exhibits irregular spherical morphology with a average particle size of 98 nm.Electrochemical tests indicated that the samples calcined at 700℃for 2 hours had the highest specific capacitance,exhibiting a specific capacitance of 88 F/g at a current density of 1 A/g,with a capacitance retention rate of 23%at a current density of 20 A/g.(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)₃O₄high-entropy nanopowders were prepared by a polymer network gel method.The influence of calcination temperature and acrylamide/metal cation mole ratio（A/M）on the phase and particle size of high-entropy nanopowders,as well as their supercapacitor performance was studied.The results showed that the higher the calcination temperature and the higher the mole ratio of acrylamide/metal cation,the more favorable to obtain single-phase high-entropy nanopowders with spinel structure.The prepared(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)₃O₄high-entropy nanopowders showed irregular spherical morphology with a particle size of 50-80 nm.Increasing the A/M molar ratio can obtain high-entropy nanopowders with finer particle size.The results of the electrochemical tests indicated that the(Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)₃O₄high-entropy nanopowders prepared with a calcination temperature of 800℃and an A/M mole ratio of 120/1 exhibited superior supercapacitor performance.It showed a specific capacitance of 384 F/g at a current density of 1 A/g,with a capacitance retention rate of 58%at a current density of 20 A/g.After 2000galvanostatic charge/discharge（GCD）cycles at a current density of 5 A/g,its capacitance retention was 60%.(Mg_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2)O high-entropy nanopowders were prepared by a polymer network gel method.The effects of calcination temperature and acrylamide/metal cation molar ratio（A/M）on the phase and particle size of high-entropy nanopowders were explored,and their supercapacitor performance was studied.The results showed that single-phase high-entropy nanopowders can be prepared at a lower calcination temperature by increasing the A/M molar ratio.The as-prepared(Mg_0.2Co_0.2Ni_0.2Cu_0.2Zn_0.2)O high-entropy nanopowders exhibits irregular spherical morphology with a particle size of 40-65 nm.Increasing the A/M molar ratio can prepare high-entropy nanopowders with finer particle size.The results of electrochemical tests showed that the high-entropy nanopowders prepared at A/M=120/1 and calcined at 900°C exhibited the best supercapacitor performance.At a current density of 1A/g,its specific capacitance is 402 F/g,and a capacitance retention rate of 62%at a current density of 20 A/g.Furthermore,after 2000 galvanostatic charge/discharge（GCD）cycles at a current density of 5 A/g,its capacitance retention rate remained at 61%...