Preparation And Performance Study Of Polymer/Graphene Composite Electrolyte And Lithium Metal Anode Solid-state Battery

In recent years,solid state lithium battery has attracted much attention due to its outstanding advantages of high safety.However,solid electrolyte has some problems such as low specific discharge capacity and poor cycling performance due to high interface impedance and low ionic conductivity.As the key material of solid state battery,the performance of solid state electrolyte determines the performance of solid state battery.In addition,lithium metal anode has the advantages of low redox potential and high theoretical capacity.However,its safety and stability limit the wide application of lithium metal anode.In order to improve the charge-discharge,rate and cycling performance of solid-state lithium batteries,graphene was creatively introduced in this paper,and PVDF-LiClO₄-Graphene solid polymer electrolytes and PVDF-LiClO₄-LATP-Graphene composite polymer electrolytes were prepared by solution pouring,to analyze whether the addition of graphene can improve the electrochemical performance of the two electrolyte membranes;At the same time,in order to improve the stability of lithium tablets in the air,make lithium battery assembly in the air as soon as possible,and reduce the cost of glove box,this paper creatively prepared modified lithium tablets with certain stability in the air.The specific research content is as follows:（1）Preparation of PVDF-LiClO₄-Graphene solid polymer electrolytes.In this dissertation,PVDF-LiClO₄-Graphene solid polymer electrolytes with different graphene contents were prepared.The physical characterization and electrical chemical performance tests revealed that the PVDF-LiClO₄-Graphene solid polymer electrolyte has excellent electrical chemical performance at 0.4 wt%of graphene content.The Li Fe PO₄cathode,PVDF-LiClO₄-Graphene solid polymer electrolyte and Li cathode were assembled into a Li Fe PO₄/PVDF-LiClO₄-Graphene/Li cell and found to have a first discharge specific capacity of 119 m Ah g^-1at 0.1C multiplicity,which is higher than that of the Li Fe PO₄/PVDF-LiClO₄/Li cell without graphene addition(93 m Ah g^-1).After 500 cycles at 0.2C magnification,its capacity retention rate was 62.89%,which was higher than that of Li Fe PO₄/PVDF-LiClO₄/Li cell without graphene addition（25.93%）.（2）Preparation of PVDF-LiClO₄-LATP-Graphene composite polymer electrolytes.In this dissertation,PVDF-LiClO₄-LATP-Graphene composite polymer electrolytes with different graphene contents were prepared.The physical characterization and electrical chemical performance tests revealed that the PVDF-LiClO₄-LATP-Graphene composite polymer electrolytes with 5 wt%graphene content had better electrical chemical performance.The Li Fe PO₄positive electrode,PVDF-LiClO₄-LATP-Graphene composite polymer electrolyte and Li negative electrode were assembled into a Li Fe PO₄/PVDF-LiClO₄-LATP-Graphene/Li cell and found that its first discharge specific capacity was 133 m Ah g^-1at 0.1C magnification,which was higher than that of the Li Fe PO₄/PVDF-LiClO₄-LATP/Li cell without graphene addition(116 m Ah g^-1).After 500cycles at 0.2C multiplier,its capacity retention rate was 69.16%,which was higher than that of Li Fe PO₄/PVDF-LiClO₄-LATP/Li cell without graphene（35.11%）.（3）Preparation of modified lithium metal negative electrodes.A mixture ofα-hydroxyisobutyrylbenzene（photoinitiator 1173）,1,6-hexanediol diacrylate（photocatalyst HDDA）,aliphatic polyurethane acrylate（monomer 425）,electrolyte（1Mol Li TFSI+DOL/DME）and N-methyl-N-propanemethanesulfonyl pyrrole bis-trifluoride（ionic liquid Pyr13TFSI）was coated on the surface of lithium wafers using the UV photo solidification method.The experiment found that lithium tablets immediately oxidize in air,and their mass increases by 50%after being left for 2 hours.After being placed in air for 2hours,the modified lithium sheet only undergoes oxidation around it,resulting in a mass increase of only 1%.The Li Fe PO₄/PVDF-LiClO₄-Graphene/GLi battery was assembled using a lithium iron phosphate positive electrode,PVDF-LiClO₄-Graphene solid polymer electrolyte,and modified lithium sheets.It was found that at a magnification of 0.2C,the first discharge specific capacity of the Li Fe PO₄/PVDF-LiClO₄-Graphene/GLi battery was maintained at 64.95%compared to the Li Fe PO₄/PVDF-LiClO₄-Graphene/Li battery.The Li Fe PO₄/PVDF-LiClO₄-LATP-Graphene/GLi battery was assembled using a lithium iron phosphate positive electrode,PVDF-LiClO₄-LATP-Graphene composite polymer electrolyte,and modified lithium sheets.It was found that at a magnification of 0.2C,the Li Fe PO₄/PVDF-LiClO₄-LATP-Graphene/GLi battery maintained a first discharge specific capacity of 94.39%compared to the Li Fe PO₄/PVDF-LiClO₄-LATP-Graphene/Li battery,and after 500 cycles,it still maintained a discharge specific capacity of 70.67%.