Performance And Lithium Storage Mechanism Of Electroactive Organic And Organic-inorganic Composite Materials As Anodes For Lithium-Ion Batteries

Lithium ion batteries(LIBs),as the advanced rechargeable batteries,are the dominant mobile power sources for portable electronic devices.Nowadays,with the wide application of LIBs in electric vehicles and smart grids,high security and sustainability are required for modern LIBs with high energy and power density.However,traditional LIBs can hardly meet these requirements due to their limited capacity and the moderate rate performance of the widely adopted commercial graphite materials.To break these limitations aroused from graphite anodes,it is imperative to develop new anode materials.Organic electrode materials are receiving more and more attention,with renewable,environmentally friendly,low energy consumption,good flexibility and controllable structure etc.Become a new way to develop large-scale lithium-ion batteries.In this work,electroactive organic materials are investigated.On the one hand,we studied the electrochemical performances of organic materials as anode for LIBs.With the help of spectroscopic techniques and electrochemical measuring techniques,the lithium storage mechanisms of organics were discussed.Promising results obtained for LIBs anodes with high specific capacity,high power,and long life span.And on the basis of these results,we studied orgaic/graphite complex electrodes.The contents include the following aspects:(1)Electrochemical performance of organic materials as anodes of LIBs and the corresponding lithium storage mechanismThe contents include the electrochemical performances of small organic compound Pyromellitic dianhydride(PMDA)as anodes of LIBs and the corresponding lithium storage mechanisms.The PMDA anode is able to reversibly deliver a capacity of 1472.2 mAh g-1 at 30 mA g-1.Even at an extremely high current of 30 A g-1,the electrode still retains 562.7 mAh g-1.After a 500 electrochemical cycles at 150 mA g-1 charge and 600 mA g-1 discharge,almost no capacity loss can be observed.The good electrochemical performance of the pyromellitic anhydride anode is because of its excellent lithium conductivity capability,as well as the stable solid electrolyte interface film formed on the electrode.(2)Electrochemical performance of organic/graphite composite as anodes of LIBs and the corresponding lithium storage mechanismAn itaconic acid-graphite composite anode is prepared for lithium ion batteries.The composite anode exhibits much improved electrochemical performances compared to the traditional graphite anode.Ahigh specific capacity of 571 mAh g-1 can be obtained at 25 mA g-1 in the voltage range of 0.01-3.0 V vs.Li/Li+,and retained 96.8%at 10 A g-1.After cycled 200 cycles at 100mA g-1 charge/200mA g-1 discharge,a reversible capacity of 693 mAh g-1 still can be achieved.At 0.01-1.5 V vs.Li/Li+,it still delivers a specific capacity of 460 mAh g-1,higher than the theoretical capacity of graphite(372 mAh g-1).The reversible lithiation/delithiation process of both itaconic acid and graphite contribute the high capacity.The excellent rate performances are related to the buffering of the itaconic acid matrix combining its superior lithium storage capability.Based on the research of organic-inorganic composites,Further studies on the dilute multiple compound of maleic acid-graphite-high purity graphite,a lot of good results have been achieved,various electrochemical properties of composite materials have improved.It also points out another direction for our future research.