Abstract
Previous studies on insertion of lithium into rhombohedral forms of 
and 
have determined the position of the 
redox couple to be at 3.6 and 2.8 eV, respectively, below the Fermi level of lithium. Lithium insertion into rhombohedral 
with NASICON framework exposes the 
redox couple at 3.3–3.4 eV below the Fermi energy of lithium. Unlike 
, the insertion of lithium into the structure of 
is accomplished as a single‐phase solid solution, which makes it attractive as an electrode material for rechargeable lithium batteries.