The Electrochemical Performance Research For Novel Electrodes In Potassium-ion Batteries

Lithium-ion batteries?LIBs?have been widely applied on the portable electronic devices,such as mobile phone,computer,MP4 player,pad and Bluetooth headset et al.,due to their advantages of light weight,stable long cycling life as well as high energy density.With the development of new clean energy car industry,LIBs have been applied on plug-in hybrid Electric Vehicle and Blade Electric Vehicles in recent years,which mean large amount of lithium resources are needed in the future.However,it is doubtable whether or not for such a large scale application due to the limited resources and uneven distribution of lithium in the Earth's crust.Thus,it is necessary to find new alternative energy storage with low cost,high energy,long cycle life and using earth-abundant materials are highly desirable for large-scale energy storage applications.Potassium,in the same column with lithium in the periodic table,has been gain a widespread attention due to the similar chemical properties as lithium,and potassium-ion batteries?KIBs?have caused great concern and developed rapidly in recent years.The researches on anode materials for KIBs include carbon anodes,organic anodes,alloyed anodes,Ti-based MXene nanosheets and metal oxides and sulfides.Among these anodes materials,carbon anodes showed the most promising properties.In this thesis,we adopt different carbon sources as anodes for KIBs and research their electrochemical performance and the potassium insertion mechanism of these hard carbon anodes.Besides,we investigated the reaction mechanism of electrolytes and the formation of solid electrolyte interface?SEI?layer.The main research works of this paper are as follows:?1?Commercial carbon molecular sieves?CMS?was adopted as anodes for KIBs,the electrochemical performance of carbon anodes in KIBs are impressive,especially the rate capacity retention and long stable cycling life.Compared with NIBs,the rate performance is much more excellent,indicate the profitable of KIBs with carbon anode in practical application;?2?A porous carbon was synthesized by sucrose carbonization,then adopted as anodes for KIBs.In this system,we adopt three kinds of carbonate electrolytes,1M KPF₆ dissolved in ethylene carbonate:diethyl carbonate?EC:DEC?,EC:dimethyl carbonate?DMC?and EC:propylene carbonate?PC??v:v=1:1?,respectively.In porous carbon/K batteries,the electrochemical performances were compared between these cells in different electrolytes.And we furtherly investigate the electrolyte decomposition mechanism during the charge/discharge process in the 1M KPF₆ dissolved in EC:DMC electrolyte system.