Preparation of Key Materials for Lithium-Air Battery and Their Applications in Flexible Devices

Author:Liu Tong

Supervisor:zhang xin bo


Degree Year:2019





In recent years,with the rapid development of flexible electronics,a lot of progress has been made in many fields,and the requirement for flexible energy storage devices is increasing.Lithium-air batteries have attracted much attention due to their high energy density,and are expected to be used in the next generation of flexible electronics.However,lithium-air batteries are still in the early stage,and there is an urgent need to solve the many key scientific problems.At present,the electrochemical performance of lithium-air batteries is low,the electrolyte is volatile and unstable,the lithium metal anodes are easily corroded,the batteries cannot operate in the air,rigid battery structure cannot meet the requirements of application in flexible devices,and the battery safety is poor,these problems limit the further development of lithium-air batteries.In response,we have carried out some studies on the synthesis of catalysts,preparation of electrolytes,protection of anodes and structural design of flexible batteries.The main results are as follows:Gel polymer electrolytes were produced in situ on the surface of lithium metal rods.The gel electrolyte possessed high flexibility,hydrophobicity,electrochemical stability and good ionic conductivity,and can provide comprehensive protection for lithium metal anode.Based on the gel electrolyte and flexible carbon cloth cathode,a new flexible Li-air battery was successfully fabricated.The battery showed high flexibility and good electrochemical stability under various bending conditions and after repeated bending.The flexible battery can operate normally even partially immersed in water,indicating the batteries is highly safe.Inspired by the idea of "break up the whole into parts",an ultrathin,lightweight,and wearable Li-air battery was fabricated.A catalyst that ruthenium dioxide confined inside the channels of carbon nanotubes(RuO2@CNTs)was synthesized,which was employed as cathode for Li-air batteries to improve the overall performance of batteries.Compared with pristine CNTs,the RuO2@CNTs exhibited greatly improved round-trip efficiency,discharge capacity,rate performance and cycle stability.At the current density of 200 mA g-1 and the limited capacity of 500 mAh g-1,the wearable Li-air battery can cycle for 288 times.In addition,the electrochemical performance of this ultrathin,lightweight,and wearable Li-air battery was stable even after repeated folding 10,000 times due to its unique battery structure.Moreover,calculated on its overall weight,the wearable battery exhibited high gravimetric/volumetric energy density(294.68 Wh kg-1/274.06 Wh L-1),which is far more exceed that of lithium ion batteries and conventional Li-air batteries.A hydrophobic composite polymer electrolyte(SHCPE)was prepared in situ on the lithium metal anode.It demonstrated many features,such as high flexibility,hydrophobicity,chemical/electrochemical/thermal/mechanical stability,and high ionic conductivity.The introduction of this SHCPE modified the contact interface between the anode and the electrolyte,reduced the corrosion of the lithium anode by harmful gases which crossover from the air,and improved the cycle life of the anode.Thus,the Li-air battery displayed improved capacity,rate performance and cycle stability when opreating in the air(from 24 cycles to 95 cycles).Based on the SHCPE protected lithium metal anode and high-efficiency MnOOH catalyst,a pouch-type flexible Li-air battery was successfully prepared,which exhibited high flexibility,stable mechanical properties and long cycle life(180 cycles in the air).In addition,the pouch-type flexible Li-air battery also displayed excellent safety,which can work stably even after repeated bending,soaking in water,high temperature and nail penetration.