  Metastable cation-disordered compounds have greatly expanded the
synthesizable compositions of solid-state materials and drawn sharp attention
among battery electrochemists. While such a strategy has been very successful
in a few well-known structures, such as rock salts, metastable
cation-disordered materials for other structural types, especially for
non-close packed structures, are peculiarly underexplored. In this work, we
develop a new series of fully cation-disordered metastable niobium tungsten
oxides with a simple structure, and name this new structural type anti-Li3N.
Furthermore, we find that metastable anti-Li3N NWOs transform to a
cation-disordered cubic structure when applied as a Li-ion battery anode,
highlighting an intriguing non-close packed to close packed conversion between
two cation-disordered phases, as evidenced in various physicochemical
characterizations, in terms of diffraction, electronic, and vibrational
structures. This work enriches the structural and compositional space of
niobium tungsten oxide families, cation-disordered solid-state materials, and
the working mechanisms of Li-ion battery anodes.
