Study On Preparation And Electrochemical Performance Of NiCo₂O₄ And Its Composite Material As Cathode Material For Aqueous Zinc-ion Battery

With the continuous consumption of global fossil energy,environmental pollution has intensified,and extreme climates have gradually emerged,the exploration of a green,safe and efficient energy storage device has become the focus.Electrochemical energy storage has begun to become the focus of research.It is well known that lithium-ion batteries are the most widely used in commercial applications.However,scarce resources and high prices have severely restricted the development of lithium-ion batteries.Water-based zinc ion batteries(ZIBs)have received more and more attention due to their high ionic conductivity,environmental stability,safety and high storage capacity of zinc.The research on its cathode materials mostly focuses on manganese-based,vanadium-based oxides and Prussian blue analogs.However,manganese-based cathode materials are prone to disproportionation reactions,and the working voltage of vanadium-based cathode materials and Prussian blue analogs is low.Therefore,it is critical to study new type of water-based zinc-ion battery cathode material.The conversion-based transition metal compounds have diverse compositions and high theoretical specific capacities,which makes it possible to become an extremely attractive cathode material for the next generation of zinc-ion batteries.In this paper,NiCo₂O₄ materials were prepared by different methods,and then composited with multi-walled carbon nanotubes(CNT)for modification.Characterized the difference in the morphology and structure of the materials,and then selected a suitable preparation method to prepare nickel cobaltate and its composite materials,and studied the electrochemical performance of pure nickel cobaltate cathode materials and nickel cobaltate composite cathode materials in aqueous zinc-ion batteries.The specific content was as follows:(1)Used Solvent thermal method+calcined heat treatment,sol-gel method+calcined heat treatment to prepare pure Ni CO₂O₄ materials.And through the CNT modified material,explored the morphological differences in the material prepared by different methods.The SEM results showed that the particle distribution of the pure Ni CO₂O₄prepared by sol-gel method+calcined heat treatment was more uniform,and there was no agglomeration,no impurities.However,after the composite CNT modification,it was contrary to the composite particles distribution prepared by solvent thermal method more uniform.(2)Used sol-gel method+calcined heat treatment to prepare pure Ni CO₂O₄ material.The XRD results showed that the main diffraction peaks of pure Ni CO₂O₄ were highly consistent with the standard card corresponding to spinel,indicating that the material has excellent purity and crystallinity.The SEM and TEM analyses showed that the material particles were uniform,no impurities,and the EDS further proved that pure Ni CO₂O₄ material was successfully prepared.The electrochemical test results showed that at the current density of 100 m Ag^-1,the first discharge specific capacity of the pure Ni CO₂O₄ positive electrode was 92 m Ahg^-1,and the discharge specific capacity was 60 m Ahg^-1 after 100 charge discharge cycle;after 200 turns,the discharge specific capacity was maintained at 44 m Ahg^-1.(3)NiCo₂O₄/CNT of nickel cobaltate compounds was successfully synthesized by solvent thermal method+calcined heat treatment+composited CNT.The XRD characterization showed that the main diffraction peak of the composite was consistent with the spinel cobalt oxagate standard card,indicating that the complex didn't affect the purity and crystallinity of the raw material.The SEM and EDS analyses showed that the NiCo₂O₄/CNT particles were successfully synthesized,and there was basically no agglomeration,no impurities.The electrochemical test showed that at at the current density of 100m Ag^-1,the first discharge specific capacity of the NiCo₂O₄/CNT positive electrode was 99.2 m Ahg^-1,and the discharge specific capacity was 57.8 m Ahg^-1 after the circulation of 300 turns.But the pure NiCo₂O₄ electrode material discharge ratio was only 5.6 m Ahg^-1 after 300 cycle.This showed that the modified composite material has more excellent cycle performance.