Design And Synthesis Of Stretchable Gel Electrolytes And Performance Research

Flexible electronics has brought many remarkable achievements and has been well applied in the fields of displays,semiconductors,perovskite cells,and embedded devices.As a derivative of flexible electronics,stretchable electronics can adapt to more complex application scenarios and meet the needs of daily life,and it has attracted widespread attention.At the same time,the development of stretchable energy storage devices that can match stretchable electrons is imminent.Lithium-ion battery（LIBs）,as a mature commercial energy storage device,has the advantages of high energy,low self-discharge and long service life,which is an ideal choice for realizing stretchable energy storage devices.This paper focuses on stretchable LIBs,starting from the design and synthesis of stretchable electrolytes（a key component of LIBs）,and studies on their mechanical properties,thermal properties,electrochemical performance（including ionic conductivity,electrochemical windows,etc.）.Finally,stretchable current collectors are also prepared to integrate SLIBs.The main research results are as follows:（1）An intrinsically stretchable polymer electrolyte containing hydrogen bonds with high ionic conductivity and excellent mechanical properties is constructed by a copolymerization strategy.The influence of the content of each component,including2-methoxyethylacrylate（EGMEA）,2-（3-（6-methyl-4-oxo-1,4-dihydropyrimidin-2-yl）ureido）ethyl methacrylate（Upy MA）,succinonitrile（SN）and lithium salt on the electrolyte properties,is thoroughly investigated.The optimal ratio is determined based on the mechanical and electrochemical performances of the diblock copolymer electrolyte.Specifically,PEU-4 with excellent mechanical（strain and stress of 4431%and 0.12 MPa,respectively）and electrochemical properties(electrochemical window of 5.3 V,room temperature ionic conductivity of 3.54×10^-4S·cm^-1,and the ionic conductivity of2.2×10^-5S·cm^-1under 4000%strain at 10℃)is successfully achieved.（2）The poly（2-methoxyethyl acrylate）ionic gel electrolyte is prepared by free radical polymerization,and the effects of monomer,ionic liquid and lithium salt content on the mechanical and electrochemical properties of the electrolyte are deeply explored.Finally,the optimized ion gel electrolyte（PBU）can be stretched 52.86times,the maximum stress value is 0.23 MPa,the thermal decomposition temperature is 337℃,the glass transition temperature is-42℃,and the room temperature ionic conductivity can reach 2.18×10^-4S·cm^-1ion gel electrolyte（PBU）.The assembled Li/PBU/LFP battery has excellent long-cycle and rate performance,with 1000charge-discharge cycles at 0.7 C rate,with an initial discharge capacity of 151m A·h·g^-1,and a capacity retention of 94.9%.Then,the cell can still be stable cycled for 1000 cycles at 2.7 C rate,with an initial discharge capacity of 95 m A·h·g^-1,and a capacity retention rate of 93.1%,confirming the superior cycle and rate performances of the cell using PBU.（3）A stretchable current conductor is prepared using a liquid metal（EGa In）as the conductive layer and a silica gel plate as the substrate.The conductor can be used as a lithium battery current collector.The current collector has a resistance of only 44.31Ωat both ends separated by 18.5 cm under 500%stretching.A stretchable electrode is obtained by scratch coating electrode slurry on the surface of the stretched current collector.Combining the prepared highly stretchable,highly conductive polymer electrolyte with the prepared stretched electrode,a stretchable LIB can be achieved,which can light up an LED under 100%strain.