Study On Manufacturing Technology Of Bamboo Fiber Activated Carbon-based Electrode Materials

Lithium ion battery is a kind of energy conversion and storage equipment with high energy,high power density and high stable cycle characteristics.Electrode material is an important device that affects its performance.It is important to optimize the electrode materials for improving the performance of lithium-ion batteries.In this study,the pyrolysis characteristics of bamboo and bamboo fibers were compared and analyzed,the precursors of bamboo activated carbon were optimized,and the synchronous carbonization-activation method was used to prepare bamboo activated carbon materials with three-dimensional pore structure.Bamboo activated carbon electrode materials were prepared by surface modification of bamboo activated carbon with N doping,and composite with graphene and metal oxide.The influence of preparation technology on pore structure,surface properties and electrochemical properties of materials was explored,and the structure-activity relationship between pore structure,surface properties and electrochemical properties was constructed.The main results were listed as follows:(1)The pyrolysis process of bamboo,bamboo fiber and model compounds can be divided into three stages:water drying stage,pyrolysis thermal analysis stage of cellulose,hemicellulose and some lignin and residue degradation stage by compared with the pyrolysis characteristics of model compounds(cellulose,hemicellulose and lignin).The main pyrolysis temperature range of bamboo,bamboo fiber,cellulose,hemicellulose and lignin were130-560?,232-390?,300-400?,200-300?and 200?to the end of the pyrolysis process,respectively.Heating rate could promote the pyrolysis reaction,the mass loss rate of bamboo fiber was 85.69%when the heating rate was 40?/min,second only to cellulose,and the activation energy of bamboo fiber was the lowest,which was 144.32KJ/mol.Compared with other samples,bamboo fiber had the highest pyrolysis activity,which is helpful to promote the pore forming reaction during activation reaction.(2)The optimum preparation process of N-doped bamboo fiber activated carbon was that the activation ratio of bamboo fiber and KHCO₃ was 1:4,the carbonization temperature was700?.N-doped bamboo fiber activated carbon material(NBFC-700-004)had an amorphous carbon structure.The content of nitrogen element was 4.73%,specific surface area was 1500.9m²/g,and average pore diameter was 1.78 nm.The main types of N elements were mainly pyrrolic-N and graphitized-N with contents of 35.3%and 30.4%,respectively.NBFC-700-004had high positive charge density and good cycle stability.The first discharge specific capacity,charge specific capacity and first cycle coulomb efficiency were 1035.7 mAh/g,477.6 mAh/g and 44.05%,respectively.(3)The optimum preparation process of N-doped bamboo fiber activated carbon and graphene compound material was that the blend ratio of N-doped bamboo fiber activated carbon and graphene was 10:1,and hydrothermal time was 12h.The composite of N-doped bamboo fiber activated carbon and graphene(NBFC/GR-10:1-12h)could form a complete conductive network structure mainly composed of micropores.The micropore specific surface area and pore volume were 706.76m²/g and 0.32cm³/g,accounting for 85%and 76%of the total specific surface area and pore volume,respectively.N element content was 5.79%,the main structural types of N were pyrrole nitrogen and graphitized nitrogen,the contents of which were 27.8%and 35.2%,respectively.The first cycle coulomb efficiency of NBFC/GR-10:1-12h could be reached 53.73%.The reversible specific capacity was 396.2mAh/g after 300cycles at the current density of 0.1A/g,which was 51.2%higher than that of N-doped bamboo fiber activated carbon and it showed the excellent specific capacity reversibility.(4)The optimum preparation process of N-doped bamboo fiber activated carbon and Fe₂O₃ compound material was that the hydrothermal temperature was 180?,hydrothermal time was 10 h and composite ratio of Fe₂O₃ and N-doped bamboo fiber activated carbon was2:1.The surface structure of N-doped bamboo fiber activated carbon and Fe₂O₃ composite(Fe₂O₃/NBFC-2:1-180-10h)was a single phase,all of which were Fe₂O₃particles.The main N structure was graphitized-N,the content of which was 40.4%,and the content of pyridine-N and pyrrole-N were 30.1%and 28.1%,respectively.The reversible specific capacity of Fe₂O₃/NBFC-2:1-180-10h was 311.6 mAh/g after 300cycles at the current density of 0.1A/g,which was 37.4%higher than that of N-doped bamboo fiber activated carbon.In addition to the first lap,the coulomb efficiency was kept above 99%and showed a good cycle stability.