One of the biggest challenges in battery development is how to increase their energy density. The cathode material represents a major fundamental limitation. Layered oxides, such as LiNi0.9Mn0.05Co0.05O2 and NaNi1/3Mn1/3Fe1/3O2, remain the best class of materials for the highest energy density Li-ion and Na-ion cells. However, to increase further the amount of energy they can store requires moving to alkali-rich cathodes (ie Li:TM>1) and contending with structural instability at high states of charge.

In this talk, I will discuss recent advances we have made in understanding the behaviour of next generation cathode materials. I will explore how oxide ions in the structure participate in the energy storage reaction to store extra charge. I will show how this O-redox reaction drives structural order-disorder transitions and results in the formation of O2 molecules trapped within the structure. I will illustrate how we have applied this understanding to overcome some of the critical issues they face and to develop improved Li-rich cathode materials. I will also look beyond layered oxides to discuss advances and opportunities in alkali-rich disordered rocksalt cathodes for beyond Li batteries.