Electrochemical Properties Of Conjugated Carbonyl Electrode Materials And Their Composites

In the long-term development and application of Lithium ion batteries(LIBs),traditional inorganic lithium intercalation compound cathode materials have highlighted many limitations.Conjugated carbonyl materials are a new class of organic electrode materials with carbonyl groups as electrochemically active functional groups.They have the advantages of environmental friendliness,outstanding theoretical specific capacity,abundant and easily available resources,etc.There are practical problems such as easy solubility in electrolyte and low redox potential.Aiming at the problems of easy solubility and poor electrical conductivity of conjugated carbonyl materials,this paper uses 1,4-p-benzoquinone and 2,5-dihydroxy-1,4-benzoquinone as the main raw materials,novel conjugated carbonyl materials and their composites were synthesized by molecular structure design and in-situ composite carbon materials,respectively,and the energy storage application of the synthesized materials in LIBs was explored by combining the electrolyte regulation strategy.The specific research contents are as follows:(1)Through molecular structure design,a simple green one-pot method was used to introduce C-N bonds to expand the overall molecular structure of the compound,and three conjugated carbonyl compounds named AQ-1,AQ-2,and AQ-3 were synthesized.An ether electrolyte,1M Li TFSI-DOL/TEGDME,was designed in combination with the electrolyte regulation strategy.Benefiting from the decrease in solubility,the specific capacity of AQ-3 in the ether electrolyte was increased to 161.2 m Ah/g in the first cycle,and the capacity retention rate was 69.5%after 100 cycles of charge and discharge.The research results show that the presence of hydroxyl groups in the conjugated system can significantly increase the redox potential of carbonyl compound materials,while reducing its solubility in electrolytes.Combined with the application of ether electrolytes,it can effectively improve the electrochemical performance of conjugated carbonyl compounds.(2)Two novel conjugated carbonyl polymers,PAQ-1 and PAQ-2,were synthesized by adopting the monomer polymerization strategy.When the current density was 25 m A/g for cycling test,the discharge specific capacity of PAQ-2 in ether electrolyte was 112.2 m Ah/g in the first cycle,and the discharge specific capacity increased to 177 m Ah/g after 100 cycles.Different from the monomer structure,the hydroxyl group in the conjugated system of the polymer will lead to a decrease in the redox potential,but the solubility and the degree of distortion of the molecular structure are significantly improved,and it is more advantageous in terms of capacity and stability.(3)Conductive modification was carried out by using graphene nanosheets composite,and the effect of the addition amount of conductive agent on the electrochemical performance of the conjugated carbonyl electrode material was explored.The specific discharge capacity of PAQ-2/0.05G with a mass ratio of 5%was 216.7 m Ah/g after 100 cycles.The results show that in the ether electrolyte,the composite graphene nanosheets help to improve the electronic conductivity of conjugation carbonyl electrode materials,and the strongπ-πinteraction with conjugated carbonyl electrode materials can further slow down the dissolution of conjugated carbonyl materials.(4)Based on the concept of green and sustainable development,using biomass pomelo peel as biochar source,two kinds of special biochars were prepared by simple pyrolysis treatment.The specific surface area of the biochar BC-1 sample treated by vacuum pyrolysis is355.087 m~2/g,the pore size is 7.271 nm,and it is in-situ composited with the conjugated carbonyl material.After 100 cycles of the PAQ-2/0.1BC-1 composite with biochar mass ratio of 10%added,the specific discharge capacity remained at 236.8 m Ah/g.showing the broad application prospects of biochar materials in the field of conjugated carbonyl materials.