Study On Synthesis And Lithium-ions Batteries Performances Of Boron-containing Polymers

During the past several decades,lithium-ions batteries?LIBs?have made remarkable progress and are widely used in portable electronic products due to their high energy density and long cycle life.Compared to anode materials,it is challenging to design high-capacity,low-cost and environmentally-friendly cathode materials.Transition metal compounds are usually employed as cathode materials in LIBs,but they have many shortcomings,such as toxicity,limited raw materials and tedious waste disposal.As an alternative,organic compounds are intensively investigated due to their inherent benefits,such as light weight,environmental friendliness,good mechanical flexibility and processability.Organic electrode materials mainly include organic conductive polymers?eg:polyaniline,polythiophene and polyimide?,organosulfur compounds,carbonyl compounds and stable radical polymers.Boron is located in the group 13 of the periodic table,with one electron less than carbon.Boron-containing materials have drawn considerable attention in recent years due to the unique properties resulting from the electron-deficient nature.Lots of studies have shown that the introduction or doping of boron can significantly improve the electrochemical performance of electrode materials.However,it's difficult to control the site and content through physical methods.Besides,there are few reports about boron-containing polymers used as battery electrode materials to the best of our knowledge.Based on the above reasons,two types of boron-containing organic polymers were successfully synthesized in this paper and their electrochemical properties as electrode materials were explored.The effects of the structure and content of boron-containing monomers on the electrochemical properties were investigated.The main tasks are listed as follows:?1?A new type of polymer B-AQ with triarylboron as the center and anthraquinone as the branch has been designed and successfully synthesized.The influence of electrolyte and conductive carbon content on its electrochemical performance was studied.The results show that,in 1 M LiTFSI DOL/DME electrolyte and at 60 wt%conductive carbon content,B-AQ has excellent electrochemical performance.In this structure,triarylboron moiety was introduced into the polymer skeleton,and the highly crosslinked honeycomb-like porous structure inhibited its dissolution in the electrolyte,resulting in excellent cycle stability of B-AQ.In 1-3.5 V voltage window?vs.Li⁺/Li?and at a current density of 1 Ag^-1,the discharge capacity of B-AQ button cell is 92.2 mAh g^-1 after 500 cycles,which retains86.3%of its initial discharge capacity.?2?A series of new organic radical battery?ORB?cathodes PTMA-PSBpin with different PSBpin unit content have been designed and sucessfully synthesized,and the effect of PSBpin content on the electrochemical performance was clarified.At 50 wt%active material content,the PTMA-PSBpin electrodes are found to bear great capacity,long-term cycle life and impressive rate performance.Due to the different content of PSBpin unit,the electrochemical performance of PTMA-PSBpin electrode is obviously different.Compared to PTMA-PSBpin-1 and PTMA-PSBpin-2,the PTMA-PSBpin-3electrode possesses the lowest voltage separation??V?,because the higher content of PSBpin unit enhances the conductivity of the material and reduces its ohmic resistance.In addition,the according oxidation/reduction mechanism of the PTMA-PSBpin electrodes during the discharge/charge process is revealed by electron paramagnetic resonance?EPR?spectra.