关键词: 锂离子电池, Li₄Ti₅O₁₂, 尖晶石负极材料, 结构演化, 离子迁移机制

Abstract: Spinel lithium titanate (Li₄Ti₅O₁₂, LTO) can undergo reversible transformation between Li₄Ti₅O₁₂ and Li₇Ti₅O₁₂, and combines the advantages of a near-zero-strain lattice response, a relatively high operating potential, and good structural reversibility; therefore, it has long been regarded as a high-safety anode material for lithium-ion batteries. These features help suppress the occurrence of particle cracking, electrode swelling, unstable solid electrolyte interphase growth, and lithium plating, giving LTO important application value in fast-charging electric vehicles, hybrid power systems, grid-frequency regulation, lithium-ion capacitors, low-temperature operation, and other safety-critical scenarios. Nevertheless, LTO remains constrained by limited theoretical capacity, intrinsically low electronic conductivity, and transport limitations under extreme lithiation states. Therefore, as an anode material, its electrochemical behavior cannot be fully explained by a static spinel-rock salt two-phase model, and a dynamic, multi-scale cognitive framework centered on structural evolution and Li⁺ migration needs to be established. This review traces the development of structural understanding in LTO, covering the early spinel-rock salt two-phase model, intermediate solid-solution domains, local symmetry breaking, asymmetric phase-boundary kinetics, and extreme-state storage mechanisms. By integrating diffraction, solid-state nuclear magnetic resonance, advanced transmission electron microscopy, X-ray absorption spectroscopy, density functional theory, and molecular dynamics simulations, it systematically summarizes how the Ti–O framework remains stable and supports rapid ion transport during Li⁺ redistribution between tetrahedral 8a and octahedral 16c environments. Special attention is given to the 8a→32e→16c migration pathway, in which the 32e position corresponds to an oxygen-framework-related migration bottleneck or transition region rather than a thermodynamically stable Li-storage site. Meanwhile, the room-temperature Li_4+xTi₅O₁₂ intermediate phase is discussed as a quasi-equilibrium solid solution dependent on size and temperature, whose stability mainly arises from the suppression of miscibility gaps within nanosized domains rather than from stability universally present in the bulk phase. Recent evidence shows that distorted face-sharing Li–O polyhedra, interfacial electric fields, vacancy availability, and electronic-conductivity transitions jointly affect microscopic hopping barriers and macroscopic charge/discharge asymmetry. Under deep lithiation, metastable 48f-related environments may provide additional capacity, but this process is usually accompanied by electrolyte reduction, interfacial pseudocapacitive contributions, and potential structural instability; direct evidence for bulk amorphization or Ti–O bond breakage remains limited. Key challenges and design strategies are further summarized, including oriented nanostructures, mesoporous single crystals, conductive carbon/graphene/TiN networks, controlled defect or dopant engineering, interphase optimization, and the avoidance of excessively deep voltage windows. Overall, LTO should not be regarded as a rigid zero-strain host, but rather as a dynamically adaptive framework; future studies need to simultaneously optimize local lattice flexibility and long-range ion-electron transport. These insights help clarify the structural causes of LTO’s high-rate performance and provide transferable principles for designing next-generation safe, durable, and fast-charging anodes.

Key words: Lithium-ion battery, Li₄Ti₅O₁₂, Spinel anode material, Structural evolution, Ion migration mechanism