  We report on \textit{ab initio} electronic structure simulations of
Li$_2$O$_2$, where 1.6% of lithium atoms are substituted by silicon. It is
demonstrated that this leads to the formation of conducting impurity states in
the band gap of Li$_2$O$_2$. We show that these states originate from the
antibonding orbitals of the oxygen pairs and are remarkably stable against
possible polaron formation (upon electron injection). Through this polaron
preemption mechanism, the proposed compound is expected to show significantly
higher electronic mobility than stoichiometric Li$_2$O$_2$, which could have
significant applications in lithium-air batteries.
