Synthesis And Energy Storage Performance Of Ni-co-mn Ternary Metal Sulfide Composites

Supercapacitors play an important role in many fields due to their high power density and long cycling stability.The energy storage mechanism of supercapacitors has evolved from a single electrostatic adsorption to a combination of multiple mechanisms.The corresponding material systems are also complex:e.g.,carbon materials with ultra-long cycling stability,transition metal oxides and sulfides which store energy via redox reactions to achieve high specific capacity,etc.In addition to the electrode material,the decisive factor for the energy storage performance of supercapacitors is the electrolyte.Aqueous asymmetric supercapacitors have become a research hotspot due to their high electrical conductivity and safety.As the research target of this work,the ternary metal sulfides(NiCoMnS₄)and their composites exhibit high research value,while less research has been reported.Through the combination of NiCoMnS₄ and other materials,high specific capacity and high power density are achieved,cycling stability and potential window are improved.Finally,aqueous asymmetric supercapacitors with commercial value are assembled by using the prepared electrodes as the cathode,activated carbon as the anode,and 2 M KOH as the electrolyte.The specific studies are as follow:(1)Synthesis and energy storage performance of S-GO/CNTs@NiCoMnS₄ on nickel foam.The mixed powder of graphene oxide(GO)and carbon nanotubes(CNTs)was first sulfided(S-GO/CNTs)by the hydrothermal method.The vulcanized powder was then uniformly coated on the surface of nickel foam,and NiCoMnS₄(NCMS)nanosheets were then grown on the Ni foam coated with active material by electrochemical deposition to form S-GO/CNTs@NiCoMnS₄(S-GO/CNTs@NCMS)electrodes.Through the exploration of a series of experimental conditions,the optimal growth conditions of the electrode(S-GO/CNTs@NCMS-16)were obtained,and the specific capacity of the electrode reached 5109 m F cm^?2 at 1 m A cm^?2.The cycling stability of S-GO/CNTs@NCMS-16 electrode was also tested and compared with that of NCMS on nickel foam,and the results showed that the cycling stability of the electrode was significantly improved.Then,S-GO/CNTs@NCMS-16,activated carbon,and 2 M KOH were used as the cathode,anode,and electrolyte,respectively to assemble an aqueous asymmetric supercapacitor,which achieved an energy density of0.323 m Wh cm^–2 at a power density of 0.849 m W cm^–2.(2)Synthesis and energy storage performance of Ni Co₂O₄@NiCoMnS₄ on carbon cloth.We developed a high-performance self-supported flexible composite electrode,consisting of NiCoMnS₄(NCMS)nanosheets on Ni Co₂O₄(NCO)nanowires grown by the hydrothermal method(Ni Co₂O₄)and the following electrodeposition(NiCoMnS₄)on carbon cloth(CC).A high specific capacity of up to 4836.2 m F cm^–2 at 1 m A cm^–2and excellent rate performance,e.g.,3820.0 m F cm^–2 at 10 m A cm^–2 and 2820.0 m F cm^–2 even at 60 m A cm^–2 can be obtained.An aqueous asymmetric supercapacitor assembled using the NCO@NCMS cathode,the activated carbon(AC)anode and the2 M KOH electrolyte delivers an energy density of 0.399 m Wh cm^–2 at 0.85 m W cm^–2and outstanding cycling stability of?81.2%capacity retention after 20000 cycles at a relatively high current density of 20 m A cm^–2.