Vacancy-ordered perovskite superlattice in cerium titanate negative electrode for enhanced lithium-ion storage.

Abstract

Commercial negative electrodes such as graphite and Li₄Ti₅O₁₂ are fundamental to lithium-ion batteries but face inherent trade-offs among safety, energy density, rate performance, and cycling stability. In this work, we introduce structural ordering and vacancy engineering into a perovskite negative electrode Ce_2/3TiO₃ to tackle this dilemma, by creating highly ordered Ce vacancies that form a stable superlattice. As a result, micron-sized Ce_2/3TiO₃ achieves a high specific capacity (>200 mAh g^-1) at an optimal operating potential (~0.8 V vs. Li⁺/Li), with fast-charging capability up to 50 C and stable cycling performance exceeding 10000 cycles at 20 C. Its electrochemical performance has the potential to overcome the shortcomings of graphite and Li₄Ti₅O₁₂, comparable to many representative intercalation-type negative electrodes. In situ structural analysis and atomic-scale imaging reveal a reversible topological phase transition between long-range and short-range ordering, which preserves the lattice integrity while unlocking low-barrier Li⁺ diffusion pathways. Here, we show that vacancy ordering provides a compelling strategy for designing high-performance electrodes.