Preparation And Properties Of PEGDA-based Solid-state Electrolyte

With the continuous improvement of the performance of various portable electronic products,especially the rapid development of electric vehicles and large-scale energy storage technology,the application equipment has put forward higher and higher requirements for energy density,cycle life and safety of energy storage batteries.All solid-state lithium battery is considered as the most competitive next generation energy storage battery due to its high energy density and high safety.However,there is no electrolyte infiltration,which leads to poor lithium ion transmission performance inside the electrode,and poor interface compatibility between solid electrolyte with electrode leads to high interface impedance.These problems seriously affect the rate performance and cycle stability of all solid-state lithium battery.In this work,PEGDA based solid electrolyte was used to improve the overall performance of all solid state batteries,starting from the internal modification of the electrode and the modification of the electrolyte membrane body.Composite cathode materials were prepared by pre-doping PEGDA-based solid electrolyte in cathode materials to solve the problem of slow Li⁺transference rate.The composite cathode showed grest performance improvement,and the Li⁺diffusion coefficient of LFP-10 with 10%doping ratio reached 4.91×10^-13 cm² s^-1,13.4 times higher than the pure Li Fe PO₄.At the same time,the rate performance of the cathode is significantly improved.The average discharge specific capacity at 5C rate is 79.75m Ah g^-1,and even at 10C rate,the average discharge specific capacity is 32.48 m Ah g^-1.The improvement of ion distribution rate has laid a foundation for the application of all-solid-state batteries.In addition,the modification of PEGDA used in solid electrolyte mainly focuses on two aspects.（1）In view of the poor flexibility of PEGDA,another polymer PEO（polyethylene oxide）was introduced to solve the problem,and the mass ratio of the two was determined at 1:5.（2）According to the low ionic conductivity of the polymer matrix,the introduction of inorganic ceramic LAZP and plasticizer SCN（succinonitrile）improved the ionic conductivity of the electrolyte.PP15-30-SCN has an ionic conductivity of 8.5×10^-5 S cm^-1 at room temperature and a Li⁺transference number of 0.43.An all-solid-state battery was assembled with composite electrolyte and tested at 60℃.The polarization of PP15-30-SCN was significantly reduced,and the battery could cycle stably at 0.1-2C.The average specific discharge capacity at 1C was 111.78 m Ah g^-1.At the same time,after more than 70 cycles at 0.5C,the capacity retention rate of PP15-30-SCN is still greater than 99%.