Tailored Morphology And Electrochemical Properties Of Self-supporting NiCo₂O₄/NF Electrode Materials

As an important element of supercapacitor,electrode material is the main factor that determine the electrochemical performance of supercapacitor.Therefore,it is great significance to design and prepare electrode materials.The spinel Ni Co₂O₄ material not only have the excellent electrochemical properties of general transition metal oxides,but also have the advantages of low cost,environment-friendly and rich resources.It has become an important material for the development and design of supercapacitor electrode materials.However,the traditional method is to use polymer binder to prepare Ni Co₂O₄ nano powder electrode active material,which is pressed on the collector by coating and bonding.This not only increases the process and cost,but also destroys the structure of Ni Co₂O₄ and affects its electrochemical activity.It also causes the conductive substrate to be coated with adhesive,so the conductivity of electrode material was greatly reduced and the overall electrochemical performance was affected.At the same time,the electrochemical performance of Ni Co₂O₄ is directly related to its morphology and structure.However,there are some problems in the preparation of Ni Co₂O₄ by traditional methods,such as agglomeration,morphology was not easy to control and so on;Moreover,it has low product utilization,poor conductivity,poor magnification etc.;More importantly,the binding force given by the binder between the electrode active material and the current collector is very weak,as the charging and discharging process progresses,the electrode material is easily detached from the current collector,which will cause a decreasing cycling ability;These restricted the real application of Ni Co₂O₄ material.In this paper,taking Ni Co₂O₄ as the research object,the Ni Co₂O₄ of micro nano structure is directly grown on the foam nickel collector,and combined with the principle of“controllable growth”of surfactant as a special microreactor of soft template.On this basis,the development from“random in situ growth”to“controllable in situ growth”is further realized.Series of self-supporting Ni Co₂O₄/foam nickel?NF?composite electrode material with different dimensions,different shapes and novel structures can be controlled.The effects of different surfactant and reaction conditions on the morphology,structure and electrochemical properties of the materials were systematically studied,and the mechanism of controllable growth was explored.?1?The micro-nano Ni Co₂O₄ of directly growing on foamed nickel was realized.The self-supporting Ni Co₂O₄/NF composite electrode without adhesive was successfully prepared.The effects of reaction temperature and time on the morphology,structure and electrochemical properties of the materials were studied,and the growth mechanism was explored.The results show that the flake array Ni Co₂O₄/NF was obtained at 80?,120?and 140?,while the micro flower array structure of nanoflake Ni Co₂O₄ self-assembled was formed at 100?and 160?.The effect of reaction time on morphology and structure is more obvious.When the reaction time was 4 h,the nano flake structure was formed;when the reaction time was 6 h,the nano flower structure was formed;when the reaction time was 8 h and 10 h,the fiber grow on the flake structure,and the cactus shape with multi-level structure was formed,and the more dense and longer the fiber grow on the cactus with increasing time.The electrochemical properties showed that the three-dimensional structure of nanoflake micro flower and cactus had higher specific capacitance and cycle stability;The results show that Hg²⁺and Cu²⁺ions in water can be simultaneously detected by micro flower structure,and it has a good detection sensitivity?29.8?A/?m?and a low detection limit?0.00991?m?.Furthermore,after 10 cycles of testing,the original peak current can still maintain 97.6%,indicating an excellent stability.These results show that the Ni Co₂O₄/NF composite electrode material with three-dimensional structure has a broad application prospect in the field of supercapacitor and electrode materials of metal ion sensors.?2?“Micro reactor”and“Controllable growth”principle of new surfactant as soft template was combined innovatively with"in situ growth".Ni Co₂O₄ of micro-nano structure with controllable in-situ growth on foam nickel has been successfully realized.A series of self-supporting Ni Co₂O₄/NF composite electrode materials with different dimensions,different morphologies and excellent electrochemical properties were prepared.The effects of surfactant type,structure and reaction conditions on the morphology,structure and electrochemical properties of the materials were studied in detail.The results show that the addition of K12 can control the formation of different sizes of fibrous and fiber microsphere structures,and the addition of AES can control the formation of different sizes of flake and fibrous structures.Adding DMHAC10 can control the formation of flaky,cacti palmate and fibrous structure;adding GC-A can control the formation of flaky,cacti globular,urchin and fibrous structure.Ni Co₂O₄ could not be grown in situ on NF,when nonionic surfactants were added.The results show that the cacti globular Ni Co₂O₄/NF material of three-dimensional multi-stage structure prepared adding GC-A had higher specific electric capacity?4.74 F/cm²,1.98 times of 2.40 F/cm²without surfactant?,better charge discharge ratio,smaller impedance,better cycle stability and other excellent electrochemical properties.It provides a new strategy for the precise design of high-performance Ni Co₂O₄/NF composite electrode materials.?3?On the basis of in-situ growth,the controllable preparation method of multi metal oxide self-supporting composite electrode material was studied.Ni Co₂O₄ of high specific capacity and excellent electrochemical activity was strongly combined with metal oxide Co₃O₄ of short diffusion path,excellent charge discharge rate and high theoretical specific capacitance.Ni Co₂O₄@Co₃O₄/NF composites materials were successfully prepared by in-situ growth of Ni Co₂O₄ modification of Co₃O₄/NF.The results showed that Ni Co₂O₄@Co₃O₄/NF electrode materials did not only show higher specific capacitance of 1075 F/g,but also showed better electrochemical charge rate?when charge density increases 5 times,the specific capacitance increases 102.4%?and long-term cycle stability?the specific capacitance remains 92.6%after 2000 cycles?.These results provide a new idea to further optimize the electrochemical performance of Ni Co₂O₄.