Abstract
Honeycomb-layered oxides with monovalent or divalent, monolayered cationic lattices generally exhibit myriad crystalline features encompassing rich electrochemistry, geometries, and disorders, which particularly places them as attractive material candidates for next-generation energy storage applications. Herein, global honeycomb-layered oxide compositions, Ag(2) M(2) TeO(6) ( M = Ni, Mg, etc .) exhibiting Ag atom bilayers with sub-valent states within Ag-rich crystalline domains of Ag(6) M(2) TeO(6) and Ag -deficient domains of Ag2-xNi2TeO6 ( 0 < x < 2 ). The Ag -rich material characterized by aberration-corrected transmission electron microscopy reveals local atomic structural disorders characterized by aperiodic stacking and incoherency in the bilayer arrangement of Ag atoms. Meanwhile, the global material not only displays high ionic conductivity but also manifests oxygen-hole electrochemistry during silver-ion extraction. Within the Ag -rich domains, the bilayered structure, argentophilic interactions therein and the expected Ag sub-valent states ( 1/2 + , 2/3 + , etc.) are theoretically understood via spontaneous symmetry breaking of SU(2)× U(1) gauge symmetry interactions amongst 3 degenerate mass-less chiral fermion states, justified by electron occupancy of silver 4dz2 and 5s orbitals on a bifurcated honeycomb lattice. This implies that bilayered frameworks have research applications that go beyond the confines of energy storage.