Preparation And Electrochemical Properties Of Carbon-based Nanomaterials

Although commercial lithium-ion batteries have been widely used,they still have many shortcomings in terms of capacity,service life,and rate performance.Improving lithium-ion batteries and developing a new generation of electrochemical energy storage devices are important research directions in the current energy research field.Carbon-based materials are used in the field of electrochemical energy storage due to the characteristics of high chemical stability,excellent electronic conductivity and good mechanical strength.However,for different electrochemical energy storage systems,it is necessary to develop high-performance electrode materials according to their energy storage principles and characteristics.In this paper,a series of carbon-based composite（doped）nanomaterials were synthesized by taking the electrode materials of lithium/sodium ion battery and the rechargeable zinc-air battery as the research objects,and their corresponding electrochemical energy storage characteristics were studied in detail.The following innovative research results were obtained:（1）High performance anode materials for lithium ion battery（NPCCs）were prepared by hydrothermal pre-carbonization and high temperature calcination doping using biomass corn stalk as carbon source.The material characterization and electrochemical test results show that NPCCs have three-dimensional porous amorphous carbon nanosheet structure,and the amount of nitrogen atom doping is as high as 18.79 at%.NPCCS has shown high reversible specific capacity,excellent cycle stability and excellent rate performance in the test of lithium-ion half battery:The specific capacity is 589.5m Ah g^-1 after 100 cycles at the current density of 0.1 A g^-1,and remaine stable at 369.4m Ah g^-1 after 1000 cycles at the current density of 1 A g^-1.Even at the current density of 5 A g^-1,the specific capacity is still 279.5m Ah g^-1.The first reversible specific capacity of lithium ion full battery（LNCM//NPCCS）assembled with commercial Li Ni_0.6Co_0.2Mn_0.2O₂ cathode material and NPCCS anode material at the current density of 0.1 A g^-1 is as high as 523.6 m Ah g^-1.These results indicate that NPCCs as anode materials for lithium-ion batteries are promising to be applied in practice.（2）A high performance anode material for sodium ion battery（Zn S/Fe S2@r GO）was prepared by in-situ co-precipitation and high temperature solid phase sulfurization using graphene oxide（GO）as carbon matrix.The Zn S and Fe S₂ bimetallic nanoparticles were tightly coated with reduced graphene oxide（r GO）by spatial confining,which improved the electrical conductivity and structural stability of the composites,and alleviated the volume change effect of metal nanoparticles in the process of charge and discharge.The electrochemical performance of Zn S/Fe S₂@r GO as the anode material of sodium ion battery was tested.The reversible specific capacity reached 361.4 m Ah g^-1 after 100 cycles at the current density of 0.1A g^-1,and 156.3m Ah g^-1 after 1500 cycles at the current density of 1 A g^-1.There is 187.5 m Ah g^-1 at the current density of 5 A g^-1,which indicates that it has good rate performance,capacity performance and cycle stability.（3）Using tetraethyl orthosilicate(C₈H₁₂O₈Si)as the silicon source and phenolic resin（RF）as the carbon source,a high-performance zinc-air battery cathode catalyst（Fe₃C@N/MCHSs）was prepared by in-situ polymerization and high-temperature calcination.The oxygen-containing groups in RF are used to anchor Fe³⁺to prevent metal particles from agglomerating during high-temperature pyrolysis,so that 3-5 nm Fe C₃ nano-dots are evenly embedded in the porous carbon hollow spherical shell layer,forming a stable heterostructure with nitrogen-doped carbon.Under alkaline conditions,the catalytic performance（catalytic activity,methanol resistance,cycling stability）of Fe₃C@N/MCHSs for oxygen reduction reaction is significantly better than that of N/MCHSs and commercial Pt/C catalysts.At the same time,the liquid rechargeable zinc air battery assembled with Fe₃C@N/MCHSs as the cathode catalyst also exhibits high specific discharge capacity and cycle life.