An Asymmetric Electrolyte with Dielectric Polarization for High‐Energy‐Density Solid‐State Lithium Metal Batteries

Abstract With high energy density and superior safety performance, solid‐state lithium metal batteries (SSLMBs) demonstrate promising prospects for broad applications. However, the application of Li7La3Zr2O12 (LLZO)‐based composite solid electrolytes (CSEs) is hindered by low ionic conductivity. Herein, oxygen vacancy‐rich LiNbO3 nanofibers (LNOV NFs) are employed as fillers to construct an asymmetric electrolyte poly(vinylidene fluoride‐hexafluoropropylene)/5%‐LNOV NFs/ Li7La3Zr2O11.8F0.2/LiTFSI (PLLO‐5%) for SSLMBs. This PLLO‐5% electrolyte comprises a garnet Li7La3Zr2O11.8F0.2 (LLZOF0.2) layer and a LNOV NFs layer. The LNOV NFs layer on the Li anode side promotes uniform lithium‐ions flux, while the LLZOF0.2 layer on the cathode side ensures high chemical stability. The PLLO‐5% electrolyte establishes a rapid lithium‐ions conduction network, achieving an ionic conductivity of 9.5 × 10−4 S cm−1 at room temperature. Density functional theory (DFT) calculations reveal that the LNOV NFs layer promotes LiTFSI dissociation, while homogenizes lithium‐ions flux and facilitates uniform lithium ions deposition. The Li||PLLO‐5%||Li symmetric cell exhibits ultralong cycling performance up to 3800 h at 0.1 mA cm−2. The Li||PLLO‐5%||LiFePO4 cell achieves a discharge capacity of 113.3 mAh g−1 at 2C after 1500 cycles. Furthermore, the Li||PLLO‐5%||LiNi0.8Co0.1Mn0.1O2 cell presents a high‐capacity retention of 74.1% at 1C after 1000 cycles, demonstrating superior cycling performance.