Preparation And Application Of Self-supporting Nanomaterial Ni₃S₂ For Energy Storage

Due to the increasing environmental pollution and the rapid development of science and technology,various types of clean energy,such as wind energy,tidal energy,lithium-ion batteries and supercapacitors,have received extensive research and attention from scientific researchers.Among them,lithium-ion batteries and supercapacitors have the advantages of high theoretical capacity,good energy storage stability,and low cost,and are widely used in many fields.The performance of energy storage devices is determined by the pros and cons of electrode materials,and the development and research of new materials with high electrochemical activity has become a key research goal.In recent years,transition metal sulfides have been widely used in lithium-ion batteries and supercapacitor energy storage systems due to their rich resources and easy availability,and multiple electron transfer reactions.In this paper,a one-step hydrothermal method is used to synthesize transition metal sulfide(Ni₃S₂)nanomaterials with different morphologies and apply them to lithium-ion batteries and supercapacitors.According to electrochemical test and analysis,Ni₃S₂ electrode material exhibits excellent electrochemical performance.The main research contents of this paper include:(1)Controllable synthesis of Ni₃S₂ nanomaterials on foam nickel substrates by hydrothermal method.The morphology of the sample is characterized by a large-scale nanocone array and secondary structure.The nanocone grows uniformly,with a length of about 5-10?m,and is tightly combined with the Ni substrate to form a self-supporting structure.The intrinsic electronic conductivity and energy density of Ni₃S₂ electrode materials are significantly increased.Thanks to this large-sized Ni₃S₂ nanocone structure,its reversible surface capacity is 15 m Ah cm^-2,which is more than 4 times that of commercial graphite electrodes on the market.In the cycle test,the coulombic efficiency also reached 94%,indicating that the Ni₃S₂ nanocone array structure material has good electrochemical performance.(2)Inspired by the above experiments,we used different sulfur sources and combined the one-step hydrothermal method to control the preparation of Ni₃S₂nanomaterials with different morphological characteristics by adjusting the time and temperature of the experiment.For example,the material is flake at 130 ?/4h,and porous at 150 ?/4h.In order to analyze the electrochemical characteristics of Ni₃S₂nanomaterials with different morphologies,structural characterization and electrochemical performance tests were carried out respectively.We applied the flaky Ni₃S₂ nanomaterial as a working electrode to the supercapacitor,and performed a long-cycle test at a current density of 20 m A cm^-2.After 2000 cycles,the capacitance of the electrode material can still be maintained at 3500 m Ah cm^-2,Coulomb efficiency reaches 93%;meanwhile,in the constant current charge-discharge test,the discharge density is 2 m A cm^-2,and the specific capacitance retention rate after 5 cycles is 86%,which shows that the flake-shaped Ni₃S₂ nanomaterial has a stable structure and good rate And cycle performance.