Dopants enhance solid electrolyte performance through three primary mechanisms: improving ionic conductivity, stabilizing interfacial interactions, and modifying structural properties.
Ionic Conductivity Enhancement
Dopants optimize ion transport by altering lattice structures or creating charge carriers. For example, fluoride anions (F⁻) in garnet-type Li₇La₃Zr₂O₁₂ reduce grain boundary resistance and stabilize the Li⁺-conducting cubic phase, enhancing bulk ionic conductivity. Similarly, Ga-doping in Li₀.₃₃La₀.₅₆TiO₃ introduces lattice distortions that facilitate Li⁺ hopping, significantly boosting ionic conduction.
Interfacial Stability
Dopants mitigate interfacial degradation between electrodes and electrolytes. In sulfide-based systems, Nb-doped cathode materials (e.g., NCM cathodes) form a protective surface layer during synthesis, minimizing side reactions with the electrolyte and improving Coulombic efficiency from ~72% (undoped) to ~81%. This coating-like effect suppresses undesirable electrochemical decomposition at interfaces.
Structural Modification
Dopants stabilize crystal phases and reduce secondary phase formation. Fluoride doping in Li₇La₃Zr₂O₁₂ suppresses Li-volatilization during sintering, leading to denser microstructures and improved mechanical integrity. Advanced doping strategies, including gradient dopant distribution, combine bulk modifications with surface passivation to address both bulk and interfacial challenges simultaneously.
These mechanisms collectively enable higher energy density, longer cycle life, and improved safety in all-solid-state batteries.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/what-role-do-dopants-play-in-enhancing-the-performance-of-solid-electrolytes/
