Application Of Polymetallic Sulfide To High Performance Supercapacitors

With the depletion of fossil energy and the deterioration of ecological environment,new green energy storage devices have attracted more and more attention.Supercapacitors are one of the most promising energy storage devices with high power density,long cycle stability and good operation safety.As electrode materials for supercapacitors,single metal sulfide has the advantages of low cost,friendly environment and large theoretical capacity.However,because of its poor chemical stability,its performance in application is not ideal.In order to improve the electrochemical performance of single metal sulfide as the starting point,this paper through the preparation of a variety of special structure of polymetallic sulfide methods to improve the electrochemical performance of metal sulfide.The main research contents include:（1）NiCo₂S₄/MnO₂ nanocomposites were prepared by two-step hydrothermal method.The specific capacity of NiCo₂S₄/MnO₂ nanocomposites was excellent,and the cyclic stability was also excellent.When the current density is 1 A g^-1,NiCo₂S₄/MnO₂ has a capacity of 450.8 C g^-1.When the current density is 1 A g^-1,the specific capacitance of hybrid supercapacitor（HSC）assembled by NiCo₂S₄/MnO₂ as positive electrode and activated carbon（AC）as negative electrode is 72.2 F g^-1.When the power density is 306 W kg^-1,the energy density is 20.8 Wh kg^-1.At the current density of 4 A g^-1,the specific capacity retention rate is 73%after 15,000 galvanostatic chargedischarge（GCD）cycles,and the cycle stability is good.（2）Ni₃S₂/Zn_0.76Co_0.24S composite was prepared by a two-step hydrothermal method.The test showed that the polymetallic sulfide could improve the electrochemical activity of the electrode,promote the Dalardi reaction between the electrode and electrolyte,and thus improve the electrochemical performance of the SC.When the current density is 1 A g^-1,Ni₃S₂/Zn_0.76Co_0.24S has a specific capacitance of517.7 C g^-1.When the current density is 1 A g^-1,the specific capacitance of the HSC assembled with Ni₃S₂/Zn_0.7Co_0.24S as positive electrode and AC as negative electrode is 106.2 F g^-1.When the power density is 407 W kg^-1,the energy density is 44.1 Wh kg^-1.Under the current density of 4 A g^-1,after 15,000 times of GCD cycle,the specific capacity retention rate is 75%,and the cycle stability is good.（3）CuCo₂S₄/NiCo₂S₄ composite was prepared by a two-step hydrothermal method.When the current density was 1 A g^-1,CuCo₂S₄/NiCo₂S₄ had a specific capacity of 876.5 C g^-1.With CuCo₂S₄/NiCo₂S₄as positive electrode and AC as negative electrode,the specific capacitance of the HSC is 129.4 F g^-1 when the current density is 1 A g^-1,and the energy density can reach 52.9 Wh kg^-1 when the power density is410.0 W kg^-1.At the current density of 6 A g^-1,After 16000 GCD cycles,the specific capacity retention rate after the cycle is 52.4%,which has a good cycle stability.