Li-ion technology has been at the front of all rechargeable battery technologies since more than two decades. Today´s state-of-the–art cathode materials are mainly transition metal oxides which rely on intercalation chemistry and the maximum achievable capacity is limited by the maximum attainable oxidation state of the transition metal (TM) ions. These limits have been broken by Li-rich compounds where charge compensation happens by oxidation of both the cation (TM-ion) and anion (oxide ion). The ability to access redox activity of the oxide ion increases the specific capacity of these Li-rich materials, but oxidation of oxide ion is typically accompanied by loss of some this lattice-oxygen leading to capacity and voltage degradation on cell cycling. In my presentation I will talk about our efforts to further understand the mechanism of anion redox in these compounds using various spectroscopic techniques. I will also speak about how we for the first time designed compounds that undergo significant reversible oxygen redox without O-loss and how O-loss is related to structural instability of currently studied Li-rich materials and is therefore not an inevitable consequence of Oxygen redox.
In this presentation I will mainly discuss the works published in:
· Oxygen redox chemistry without excess alkali-metal ions in Na2/3[Mg0.28Mn0.72]O2. Nat. Chem., 2018, 10,288
· Lithium manganese oxyfluoride as a new cathode material exhibiting oxygen redox. Energy Environ. Sci., 2018, 11, 2