Interfacial Functionalized Porous Li₀.₃₃La₀.₅₅₇TiO₃ Enabling Fast Lithium-ion Transport in Solid Polymer Electrolytes

Abstract

Incorporating inorganic electrolyte fillers within solid polymer electrolytes (SPEs) is generally considered an efficient strategy for constructing rapid Li⁺ transport channels, thereby markedly enhancing ionic conductivity. However, the relatively low specific surface area of traditional fillers, along with their inherently weak interfacial affinity toward polymer matrices, hampers effective Li⁺ transport across the polymer–filler interface. Consequently, Li⁺ migration from the polymer domain into the filler phase remains kinetically unfavorable, which ultimately limits further improvement in the overall electrochemical performance of SPEs. Here, we report a scalable porosity–interface co-engineering strategy to overcome these limitations. First, a three-dimensional, percolating porous Li₀.₃₃La₀.₅₅₇TiO₃ (PLLTO) scaffold is constructed to significantly enlarge the solid–solid contact area and promote continuous Li⁺ percolation pathways. Second, surface functionalization using 3-glycidoxypropyltrimethoxysilane (KH560) to form silicon-coated PLLTO (Si-PLLTO) with a silane-mediated interface layer. This interfacial layer enhances polymer/ceramic bonding through hydrogen bonding and possible covalent linkage formation, decreases interfacial Li⁺ transfer resistance, and suppresses electron transfer toward titanium centers, thereby mitigating undesirable reduction from Ti⁴⁺ to Ti³⁺. Density functional theory (DFT) calculations reveal that surface silicon modification lowers the Li⁺ migration energy barrier (1.77 eV) by modulating surface electronic structures and weakening Li-O coordination along interfacial conduction pathways, thus enabling energetically favorable Li⁺ transport. As a consequence, the resulting SPE exhibits a elevated ionic conductivity of 1.32 mS cm−1 at 30 °C. It further delivers an ion transfer number of 0.57 and sustained lithium plating/stripping for 4000 h in lithium symmetric batteries. LiFePO₄|Li batteries retain 82.4% of their initial capacity after 1200 cycles at 0.2C with 99.9% coulombic efficiency (CE). These results demonstrate that coupling a porous ceramic scaffold with targeted interfacial chemistry markedly improves ion transport, interfacial stability, and cycling durability, providing a generalizable strategy for constructing high performance, safe solid state lithium batteries.