Fabrication And Electrochemical Performance Of Conductive Polymer Electrode Materials For Lithium-Ion Batteries

The development of advanced energy storage methods is one of the key technologies to improve energy utilization.Lithium-ion batteries are widely used in portable electronic products,automobiles,aerospace and other fields due to their high energy density and good stability.Organic polymers are considered to the next generation of high-performance lithium-ion batteries due to the due to the facile synthesis,resource renewability,structure diversity and design flexibility.In this dissertation,we aims to improve the energy density and cycle stability for lithium-ion batteries.Design and preparation new triphenylamine and thiophene polymer materials for lithium-ion batteries and carefully studies the effect of polymer structure on battery performance.The main results and new finding and results are as follows:(1)The polymers of p BHT,p BAT and p BABT based on benzhene-thiophene were designed and successfully prepared for lithium ion battery anode materials.The pore structures of three polymers are quite different.SEM and BET measurements of p BHT exhibits the unique stacked hollow tube morphology and possesses the high surface area(1139 m~2/g).Being explored for the battery performance as anode materials,at the current of 100 m A/g,the p BHT electrode displayed a specific discharge capacity of1649 m Ah/g in the first cycle and sharp decay to 84 m Ah/g in the second cycle,shows poor stability.This uncommon electrochemical properties may be attributed to the unique hollow tube morphology for the polymer p BHT,which limit the lithium ion released and might form“dead lithium”,cause the polymer structure to collapse.In contrast,the p BAT and p BABT with very low specific surface area(32.5 m~2/g and 12.5m~2/g),but shows excellent electrochemical performance(525 m Ah/g and 729 m Ah/g at 100 m A/g of the second cycle).The p BABT electrode has a discharge specific capacities of 401 m Ah/g and capacity retention rate of 93%at 500 m A/g after 1000cycles.The p BAT and p BABT have strong conjugate structure and loose surface structure,provides a good channel for charge transport and lithium-ion insertion and extraction.It proves that the abundant microporous structure does not necessarily improve the battery properties of thiophene derivatives,but loose surface and macropore structure can improve the electrochemical performance.This found can give a reference to make high-performance polymer anode materials.(2)The conjugated polymers p DTPA-EAq and p TPA-Aq-TPA based on triphenylamine-anthraquinone were designed and successfully prepared.Being explored as cathode materials,the p DTPA-EAq electrode has a discharge capacity of119 m Ah/g in the first cycle at 20 m A/g and 53.2 m Ah/g after 100 cycles.However,p TPA-Aq-TPA electrode has a discharge capacity of 84.4 m Ah/g and capacity retention rate reaches 71.7%after 100 cycles.The results showed that this kind of polymer electrode materials have obvious charge trapping effect.The stronger the conjugation between triphenylamine and anthraquinone,the more obvious and the higher potential required to release.The capacity attenuation caused by the CT effect can be partially recovered by a limited number of charge releases.CT effect was found in lithium ion batteries and proposedthe CT effect can improve the electrode's cycling stability.This discovery can give some design ideas to make high-performance cathode materials with both p-doped and n-doped.