Speakers

The development of oxide-based solid-state electrolytes (SSEs) is central to enabling next-generation all-solid-state batteries with enhanced safety and energy density. Despite their intrinsic thermal and mechanical stability relative to liquid electrolytes, oxide SSEs remain constrained by limited Li⁺ conductivity, interfacial instability, and electronic inhomogeneity, phenomena that frequently originate from structural and chemical disorder. These limitations are not solely dictated by static lattice defects but emerge from the interplay of lattice vibrations, charge carriers, and local electronic structure.
Here, we advance a quantum-physical perspective that links phonon dynamics to Li⁺ migration and electrochemical stability in oxide SSEs. Using Ta-doped Li₇La₃Zr₂O₁₂ as a model system, we show that aliovalent substitution at Zr sites generates a non-linear vibrational landscape that dynamically reshapes local potential energy surfaces. This environment promotes correlated Li⁺ hopping through enhanced phonon–phonon coupling and the activation of low-frequency anharmonic modes, increasing migration entropy and driving a transition from single-ion to collective multi-ion transport. These findings highlight phonon engineering as a decisive lever for overcoming conductivity bottlenecks in oxide SSEs.
Beyond bulk transport, we reveal that grain boundaries in Li0.33La0.57TiO3 act as preferential electron-conduction pathways due to oxygen deficiency, giving rise to space-charge layers characterized by Li accumulation and inhomogeneous Ti⁴⁺ reduction. The resulting electron–phonon coupling facilitates polaron formation and spatially uneven Li⁺ flux, ultimately triggering dendritic growth. Importantly, aliovalent doping introduces controlled anharmonic phonons that suppress polaron localization and restore homogeneous Li⁺ transport across grain boundaries.
Collectively, these insights establish phonon–phonon and phonon–electron interactions as fundamental physical parameters governing Li⁺ flux in oxide SSEs and provide a mechanism-based framework for the rational design of high-performance solid-state electrolytes.