Preparation And Lithium Storage/Wave Absorption Properties Of Cobalt Based Bimetallic Sulfides/porous Carbon Nanofiber Composite Materials Absorbers

With the continuous increase in global energy consumption,energy crisis has become a serious problem we face.In order to meet future demands,people need to seek and study more environmentally friendly and efficient energy storage technologies,which has attracted increasing attention.Meanwhile,with the rapid development of wireless communication technology and electronic devices,electromagnetic pollution seriously affects people’s daily lives.Carbon-based materials are favored due to their good chemical stability,high specific surface area,and conductivity.Transition metal sulfides have good conductivity,which can more effectively transfer electrons and ions,thereby improving battery performance;higher conductivity and lower internal resistance can better absorb and reflect electromagnetic waves.When the two act alone,they have certain limitations.Therefore,this paper uses polyacrylonitrile（PAN）as a carbon precursor,polymethyl methacrylate（PMMA）as a pore-forming agent,and uses electrospinning to prepare a porous carbon nanofiber membrane.Finally,cobalt-based and bimetallic sulfide/porous carbon nanocomposite fiber membranes were prepared by adding salt content through a hydrothermal method.This experimental method aims to increase the low theoretical capacity of carbon nanofibers,resist the volume expansion and contraction during lithium ion insertion and extraction,and thereby improve the electrochemical performance of lithium batteries.At the same time,the porous carbon nanofibers are not only conducive to the embedding and extraction of lithium ions,but also increase the contact area with the electrolyte,thereby improving battery performance;meanwhile,the porous structure is more conducive to improving the absorption performance of absorbing materials.Based on the current stage of combining the two to make composite materials,the research direction and results of this paper are as follows:（1）Using the hydrothermal method,composite samples ZnCo₂S₄/PCNFs-1,ZnCo₂S₄/PCNFs-3,and ZnCo₂S₄/PCNFs-5 were prepared by adjusting the salt content added.These samples have excellent structural stability,do not require the addition of any conductive agent or current collector,and can be directly used as the negative electrode of lithium-ion batteries,reducing costs while increasing battery safety.ZnCo₂S₄ has stable chemical properties.The crystallinity of ZnCo₂S₄/PCNFs-3 nanoparticles is good,showing the optimal lithium storage performance.Under the condition of a current density of 100 m A g^-1,after continuous cycling for 100 cycles,it can still stabilize at 662.3 m Ah g^-1.Compared with the two contrast samples,ZnCo₂S₄/PCNFs-1 and ZnCo₂S₄/PCNFs-5,it exhibits better cycling performance.（2）The CuCo₂S₄/PCNFs-1,CuCo₂S₄/PCNFs-3,and CuCo₂S₄/PCNFs-5 composite nanofibers have high crystallinity of CuCo₂S₄.Among the electrodes treated with different salt contents by hydrothermal method,CuCo₂S₄/PCNFs-3 exhibits relatively good electrochemical performance,and can still show 550.2 m Ah g^-1 after 100 cycles under a current density of 100 m A g^-1.（3）A series of battery tests and electromagnetic absorption performance tests were conducted on the prepared composite samples of ZnCo₂S₄/PCNFs-1,ZnCo₂S₄/PCNFs-3,and ZnCo₂S₄/PCNFs-5 to investigate the influence of different salt contents of composite nanomaterials on the electromagnetic absorption performance.The RL_min of ZnCo₂S₄/PCNFs-5 reached-47.2 d B at a frequency of 12.4 GHz and thickness of 3 mm,while the corresponding EAB_maxat 2.5 mm was 6.37 GHz（11.27～17.64 GHz）.