Realization of Li+ Domain Diffusion Effect via Constructing of Molecular Brushes on LLZTO Surface and Its Application in All-solid-state Lithium Batteries
All-solid-state lithium metal batteries based on polymer electrolytes provide great promise for solving security issues and specific energy. However, poor ionic conductivity and large interfacial impedance still holds back their development. Introduction of inorganic nanoparticles strategy was used to improve the ionic conductivity and enhance the mechanical properties but the current migration mechanism in the composite polymer electrolyte (CPE) is ambiguous. In this work, the Li6.4La3Zr1.4Ta0.6O12 (LLZTO) nanoparticles with molecular brushes (MB-LLZTO) were designed and introduced into poly (ethylene oxide) (PEO) to form a high ionic conductivity composite electrolyte. MB-LLZTO in the polymer matrix play an ideal role for increasing the ionic conductivity by the Li+ domain-diffusion effect. The CPE with 15 wt % MB-LLZTO exhibits the highest ionic conductivity of 3.11×10-4 S/cm at 45 ℃ (the value of pristine LLZTO-CPE is 9.16×10-5 S/cm). The high-resolution solid-state Li NMR provides the experimental evidence for the proposed mechanism in composite electrolyte that Li+ tend to diffuse in the fast-conduction domains introduced by the brushes of MB-LLZTO surface. Consequently, the all-solid-state Lithium-Sulfur battery with MB-LLZTO-CPE shows a discharge capacity of approximately 1280 mA h g-1 at low temperature, and stable cycling performance (752 mA h g-1 after 220 cycles). Construction of molecular brushes on LLZTO surface may be an effective way to unlock more potential solid polymer electrolytes.