The active cathode material in commercial rechargeable lithium batteries, is shown to be a p‐type semiconductor, associated with the presence of a small concentration of ions. Its conductivity at room temperature can be increased by over two orders of magnitude, to ∼0.5 S cm−1, by partial substitution of by and compensating hole creation. The electrochemical performance of is comparable to that of ; a small reduction in capacity, associated with a reduction in content, occurs but good reversibility is retained and, in contrast to , the Mg‐doped material is single phase throughout the charge/discharge cycle.