Ethers are promising electrolyte solvents for secondary Li metal batteries because of their excellent cathodic stability. However, their anodic stability has been mostly relying on the high concentration approach, and limited progress has been made on building effective interphase to protect the cathode from the corrosion of the electrolyte. In this work, we construct a semi-crystalline interfacial layer on the surface of Li(Ni_0.8Co_0.1Mn_0.1)O₂ cathode that can achieve improved electrochemical stability in the highly corrosive chemical environment formed by the decomposition of ether molecules. Different from traditional brittle crystalline interphases, the optimized semi-crystalline layer with low modulus and high ionic conductivity can effectively relieve electrode strain and maintain the integrity of the interface layer. Due to this design, the continuous anodic decomposition of ether-based electrolytes could be significantly suppressed and the battery shows outstanding cycling stability (84% capacity retention after 300 cycles). This article provides a solution to address the anodic instability issue of ether-based electrolytes.