Synthesis Of Nickel And Manganese-Based Electrode For Aqueous Hybrid Supercapacitors

Hybrid supercapacitor（HSC）is a new type of energy storage device with features of low cost,safety,high power density and long cycle life.This theis first reviews the research progress of hybrid supercapacitors and introduces the research progress of nickel-based and manganese-based hybrid supercapacitors.We conducted a systematic and in-depth study on the surface structure design of nickel foam,the structural stability strategy of manganese-based material,large-scale preparation,applications in new aqueous ion hybrid supercapacitors,and a series of meaningful research results were obtained:（1）Commercial nickel foam（NF）is a good three-dimensional（3D）conductive substrate,but it has the problems of insufficient surface activity,low specific surface area,easy oxidation,and poor stability is used.To overcome these bottlenecks,NF supported Ni O nanosheets with a NF@Ni O core@shell structure was synthesized by a facile etching-reoxidation method.The obtained NF@Ni O can function as high-performance free-standing electrodes for hybrid supercapacitors.When employed as the cathode for hybrid supercapacitors,the NF@Ni O exhibits a high areal capacitance of 2010 m F cm^-2 at 8 m A cm^-2.By coupling with a Fe OOH anode,the assembled NF@Ni O//Fe OOH hybrid supercapacitor delivers a peak energy density of 0.215 m Wh cm^-2 and a peak power density of 275 m W cm^-2 with remarkable cyclic durability（84.7%capacity retention for 5000 cycles）.（2）Ni₃S₂,which has metal-like properties,shows good electrochemical activity and has been regarded as a very promising cathode material for hybrid supercapacitors.In this thsis,we designed and prepared a free-standing hierarchical cobalt-doped Ni₃S₂（Co-Ni₃S₂）nanorod arrays as a novel pseudocapacitive electrode to realize impressively high areal capacitance.When applied as the HSC cathode in three-electrode system,the Co-Ni₃S₂ manifests a remarkable areal capacitance of 3460 m F cm^-2 at 8 m A cm^-2.An ideal cyclability（91.4%retention for 10 000 cycles）has been achieved as well,demonstrating the benefits of the welldesigned free-standing nanostructure.More importantly,by coupling with an Fe OOH anode,the matched Co-Ni₃S₂//Fe OOH HSC reaches an excellent areal capacitance of 1610 m F cm^-2 and delivers a high energy density of 0.73 m W h cm^-2,a peak power density of 36.00 m W cm^-2,and stable cycling performance.（3）We prepared a rechargeable ammonium-ion hybrid supercapacitor（A-HSC）,where layeredδ-MnO₂ nanosheets on flexible carbon cloth acts as the cathode,activated carbon cloth（ACC）acts as the anode,and（NH4）2SO4 acts as the electrolyte.In the A-HSC,the intercalation/de-intercalation and adsorption/desorption exist in the layeredδ-MnO₂ nanosheets cathode together with the adsorption/desorption in the ACC anode can provide superior electrochemical properties.The prepared A-HSC presents an ultrahigh areal capacitance of 1550.2 m F cm^-2 at 2 m A cm^-2,and the operating voltage window reaches a wide range of 0-2.0 V.The A-HSC also delivers an excellent peak areal energy density of 0.86 m Wh cm^-2 and a peak areal power density of 20.0 m W cm^-2.The rechargeable A-HSC shows a superior capacity retention of 72.2%after 5000 cycles.（4）We designed a highly stable tunnel-structure of Zn_x MnO₂ nanowires grown on mechanically flexible carbon cloth with a disruptively large mass loading of 12 mg cm^-2.The Zn²⁺stabilized tunnel structure of Zn_x MnO₂ an grown on flexible carbon cloth is developed by one-step hydrothermal process,where the pre-intercalation of Zn²⁺transforms the layeredδ-MnO₂ nanosheets into tunnel-structured Zn_x MnO₂ nanowires with high stability.In Zn-HSCs,the ion insertion/extraction in the Zn_x MnO₂ nanowire cathode and the adsorption/desorption on the ACC anode provide an outstanding electrochemical performance.The as-prepared Zn-HSC presents an ultrahigh areal capacitance of 1745.8 m F cm^-2 at 2 m A cm^-2 with a wide operating voltage window of 0-2.0 V.They also deliver a remarkable areal energy density of 0.97m Wh cm^-2 and a peak areal power density of 20.1 m W cm^-2.The rechargeable Zn-HSCs show a superior capacity retention of 83.1%after 5000 cycles.The above research provides new insights into optimizing the electrochemical performance of nickel-based and manganese-based electrode materials and the development of novel hybrid supercapacitors.