Li-superionic conductive Sc-based solid electrolyte
ABSTRACT
We report a new Li-superionic conductive chloride, Li2Sc2/3Cl4, that crystallizes in a disordered spinel structure, and exhibits an ionic conductivity of 1.5 mS·cm-1 with a low activation energy barrier for Li+ ion diffusion of 0.34 eV. This material represents the first spinel-type Li-superionic conductor. Structural elucidation via powder neutron diffraction reveals a significantly disordered Li+-ion distribution over available tetrahedral and octahedral sites within the lattice, which forms an infinitely 3D connected Li+ ion diffusion pathway comprised of face-sharing octahedra and tetrahedra. Due to the high oxidative stability of Li2Sc2/3Cl4, all solid state lithium batteries employing Li2Sc2/3Cl4 and high voltage cathodes (LiCoO2, LiNi0.6Mn0.2Co0.2O2 or high-Ni LiNi0.85Mn0.1Co0.05O2) - without any coating - exhibit excellent electrochemical performance up to 4.6 V in terms of capacity retention and cycle life.
Conclusions
In summary, we have synthesized a new superionic chloride, Li2Sc2/3Cl4, with a disordered spinel structure and high Li+ ion conductivity of 1.5 mS·cm-1 , representing the first spinel structure superionic conductor. Excellent electrochemical performance is observed for bulk-type ASSBs with bare LiCoO2 or NMC cathode materials (no external coating) at potentials up to 4.6 V, which augers well for the future development of advanced high energy density and stable cycling life ASSBs. Most importantly, while we report the first spinel superionic conductors, multiple elemental doping can be conducted to further increase the ionic conductivity. The same concept can be applied to other Li-spinel structured materials including sulfides and oxides, which opens a new avenue in developing new solid electrolytes for all solid state batteries.
https://www.osti.gov/pages/servlets/purl/1657953