Preparation Of Jute Porous Carbon And ZnMn₂O₄ Composites And Their Lithium Storage Performance

Due to the industrial transformation of upgrading fuel vehicles to electric vehicles,the demand for electrochemical energy storage devices in the automobile manufacturing industry has surged.Lithium-ion batteries have outstanding advantages such as high energy density,high operating voltage and long cycle life,so they are widely used in electric vehicle energy storage device.However,the low theoretical specific capacity(372 m Ah g^-1)of the currently widely used graphite anode materials leads to a short cruising range of electric vehicles,which greatly limits the use scenarios of electric vehicles.Therefore,it is necessary to explore new anodes material with high capacity.The binary transition metal oxide ZnMn₂O₄ anode material is a promising anode material with outstanding advantages such as high theoretical specific capacity(784 m Ah g^-1),abundant reserves and environmental friendliness.However,its practical application is limited by low conductivity and excessive volume expansion during cycling,the introduction of carbon matrix and the construction of ZnMn₂O₄ microstructure are effective strategies to solve the above problems.Biomass carbon material has the advantages of low price and large output,its introduction as a carbon matrix can improve electrical conductivity and buffer volume expansion,and the construction of ZnMn₂O₄ microstructure can help alleviate the volume expansion caused by frequent Li⁺intercalation/deintercalation and provide Li⁺transport channels.In this paper,the prepared jute porous carbon is used as a carbon matrix and composited with ZnMn₂O₄ with different microstructures and used as a negative electrode material for lithium-ion batteries,the research contents are as follows:(1)The pre-carbonized jute carbon was co-calcined with K₂CO₃ in an argon protective atmosphere to obtain a jute porous carbon with an ultra-high specific surface area of 1246.89m~2 g^-1 and a rich pore structure.ZnMn₂O₄ spheres were synthesized using spherical Mn CO₃as template,and ZnMn₂O₄ spheres were anchored on jute porous carbon matrix by mixed solvothermal method to prepare ZnMn₂O₄ spheres/jute porous carbon composite.The introduction of jute porous carbon as the carbon matrix significantly increases the dispersion of ZnMn₂O₄ spheres and provides abundant Li⁺channels for the anode material.Compared with pure-phase ZnMn₂O₄ spheres,the electrochemical performance of the composite is significantly improved.After confirming that the introduction of jute porous carbon improves the electrochemical performance,the effects of different mixed solvothermal times(36 h,48 h,60 h)on the microstructure and electrochemical performance of the composite were tested.The SEM and TEM images of the composite prepared by the mixed solvothermal time of 48 h showed that the ZnMn₂O₄ spheres anchored on the jute porous carbon had good dispersion.It exhibits a reversible capacity of 1549.2 m Ah g^-1 at a rate of0.2 C,and its rate performance is significantly improved compared to other solvothermal time composites.(2)Zn_1/3Mn_2/3CO₃ precursors were prepared by microemulsion method,submicron-sized ZnMn₂O₄ cubes were obtained after calcination,and ZnMn₂O₄ cubic/jute porous carbon anode materials were prepared by mixed solvothermal method.The effect of different mixed solvothermal time(12 h,24 h,36 h)on the electrochemical performance of the anode material was explored,and it was found that the anode material had the best electrochemical performance under the solvothermal time of 24 h.After 200 cycles at the rate of 0.2 C,it still has a discharge capacity of 1121.3 m Ah g^-1.In the rate performance test,the composite synthesized under the 24 h solvothermal time have better electrochemical performance than the pure-phase ZnMn₂O₄ cubes and the composites synthesized under the remaining solvothermal time.(3)ZnMn₂O₄ nanoparticles were prepared in solution,and the nanoparticles were anchored on jute porous carbon by hydrothermal method to prepare ZnMn₂O₄nanoparticles/jute porous carbon anode material.The electrochemical properties of the composites with three material ratios(1/1,2/1,3/1)were tested at a hydrothermal temperature of 140?.When the material ratio of nanoparticles to jute porous carbon is 2/1,the electrochemical performance of the composite is better its capacity is 805.9 m Ah g^-1 after200 cycles at 0.2 C.Optimized the hydrothermal temperature parameters,increased the hydrothermal temperature and set three temperature gradients(160?,180?,200?).At a hydrothermal temperature of 180?,the nanoparticles have the best dispersion on the jute porous carbon matrix,and the composite has the best electrochemical performance,it has a capacity of 951.1 m Ah g^-1 after 200 cycles at a rate of 0.2 C.