  We have explored the effects of the Li intercalation on the electronic and
magnetic properties of transition-metal (TM) doped anatase TiO$_2$. By Li
intercalation, Mn-doped TiO$_2$ exhibits the insulator to metal transition. On
the other hand, Li-intercalated Fe-doped TiO$_2$ has the insulating ground
state for low concentration of Li/Ti=0.067, but the metallic ground state for
high concentration of Li/Ti=0.133. We discuss the $n$-type carrier induced
ferromagnetism in Li-intercalated TM-doped anatase TiO$_2$. Based on the
Li-intercalated TM-doped anatase TiO$_2$, we propose a potential spintronic and
electrochromic device controlled by the electric-field.
