Orientational Relationship Between the Solid-Electrolyte Interphase and Li4Ti5O12 Electrode in Hybrid Aqueous Electrolytes

Abstract

<p>Lithium-ion (Li-ion) batteries are essential to modern society, but pose safety risks because of thermal runaway and ignition. This study explores the use of hybrid aqueous electrolytes to enhance the safety and performance of Li-ion batteries, focusing on the solid-electrolyte interface (SEI) formed on lithium titanate (Li₄Ti₅O₁₂; LTO) electrodes. We employed high-resolution transmission electron microscopy (HRTEM) and density functional theory (DFT) calculations to analyze the microstructure and stability of the SEI layer. Further, we prepared LTO and LiMn₂O₄ (LMO) electrodes, assembled full cells with hybrid aqueous electrolytes, and carried out electrochemical testing. The HRTEM analysis revealed the epitaxial growth of a LiF SEI layer on the LTO electrode, which has a coherent lattice structure that enhances electrochemical stability. The DFT calculations confirmed the energetic favorability of the LiF–LTO interface, indicating strong adhesion and potential for epitaxial growth. The full cell demonstrated excellent discharge performance, showing a notable improvement in coulombic efficiency after the initial cycle and sustained capacity over 100 cycles. Notably, the formation of a dense, crystalline LiF SEI layer on the LTO electrode is crucial for preventing continuous side reactions and maintaining mechanical stability during cycling. The experimental results, supported by the DFT results, highlight the importance of the orientational relationship between the SEI and the electrode in improving battery performance. The integration of experimental techniques and computational simulations has led to the development of an LTO/LMO full cell with enhanced discharge capabilities and stability. This study provides insights into the growth mechanisms of the SEI layer and its impact on battery performance, demonstrating the potential of hybrid aqueous electrolytes in advancing lithium-ion battery technology. The findings affirm the viability of this approach for optimizing next-generation Li-ion batteries, which can promote the development of safer and more reliable energy storage solutions.</p>