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

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 (LNO_V NFs) are employed as fillers to construct an asymmetric electrolyte poly(vinylidene fluoride-hexafluoropropylene)/5%-LNO_V NFs/ Li₇La₃Zr₂O_11.8F_0.2/LiTFSI (PLLO-5%) for SSLMBs. This PLLO-5% electrolyte comprises a garnet Li₇La₃Zr₂O_11.8F_0.2 (LLZOF_0.2) layer and a LNO_V NFs layer. The LNO_V NFs layer on the Li anode side promotes uniform lithium-ions flux, while the LLZOF_0.2 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 LNO_V 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%||LiNi_0.8Co_0.1Mn_0.1O₂ cell presents a high-capacity retention of 74.1% at 1C after 1000 cycles, demonstrating superior cycling performance.