Combining Reversible Oxygen Charge Transfer and Li-Excess to achieve High Capacity Cathodes

The highest energy density cathode materials are currently found among the layered compounds based on Ni,Co and Mn, but achieving much more than 200mAh/g has become difficult. Two new ideas are promising to obtain substantially higher cathode capacity: 1) By using a substantial amount of Li-excess, cathodes can be made tolerant to metal disorder thereby enabling the use of a much larger group of transition metals, while achieving capacities well above 200 mAh/g. 2) Reversible redox process that take place on the oxygen ions rather than on the transition metal ions are now well established and can reduce the transition metal content of cathode compounds. I will explore the physics of both these new directions and demonstrate with several examples how they have enabled novel high-capacity cathodes.