PEO对固态锂电池正极/电解质界面的改性

Modification of Cathode/Electrolyte Interface in Solid State Lithium Battery by PEO

摘要:

电动汽车工业的快速发展对高安全性和高能量密度的固态电池提出了迫切需求，电解质和界面阻抗是制约固态电池性能的两大关键问题。本文在固态锂电池正极/氧化物电解质界面处引入聚氧化乙烯（PEO）缓冲层以改善固体接触。用热压烧结法制备了密度为5.25 g/cm3、锂离子电导率为8.33×10-4 S/cm的Li6.4La3Zr1.4Ta0.6O12(LLZTO)固体电解质，配制了PEO-LiTFSI-LLZTO缓冲层和LiFePO4复合正极浆料，用匀胶机旋涂法将PEO缓冲层和复合正极浆料依次涂覆在电解质表面，测得60 °C下正极界面电阻值为509 Ωcm2。测试对称电池充放电曲线证明界面稳定性良好，电池首次循环放电容量145.8 mAh/g，库伦效率大于97%。

Abstract:

The rapid development of electric vehicle industry has placed urgent need for solid state battery with large capacity and high energy density. The electrolyte and interface problems are two key issues that limit the performance of solid state battery. The paper introduced PEO buffer layer to the cathode/electrolyte interface to improve contact. First, Li6.4La3Zr1.4Ta0.6O12(LLZTO) with density of 5.25 g/cm3 and ionic conductivity of 8.33×10-4 S/cm was prepared. Second, the paper prepared PEO-LiTFSI-LLZTO buffer layer and LiFePO4 composite cathode slurry. The PEO buffer layer and cathode slurry were coated on the surface of electrolyte by spin coating, respectively. The interfacial resistance was 509 Ωcm2 at 60 °C. The galvanostatic charge and discharge curve of symmetric battery proved excellent interfacial stability. The solid state battery has fist discharge capacity of 145.8mAh/g and coulombic efficiency of over 97%.