Interfacial functionalization of 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 areas of traditional fillers, along with their inherently weak interfacial affinity toward polymer matrices, hamper effective Li⁺ transport across polymer–filler interfaces. 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 Li_0.33La_0.557TiO₃ (PLLTO) framework is constructed to significantly enlarge the solid–solid contact area and promote continuous Li⁺ percolation pathways. Second, surface functionalization is carried out using 3-glycidoxypropyltrimethoxysilane (KH560) to form silicon-coated PLLTO (Si-PLLTO) with a silane-mediated interfacial 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 elevated ionic conductivity of 2.37 mS cm⁻¹ at 60 °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 enhancing a porous lithium ceramic framework with a targeted interfacial chemistry approach markedly improves ion transport, interfacial stability, and cycling durability, providing a generalizable strategy for constructing high-performance, safe solid-state lithium batteries.