In addition, they have 3D diffusion channels where Li + migrate through "gate sites": sixmember cation rings perpendicular to the diffusion path. LMNO, however, has improved energy density and cycling stability compared to LMO partly due to a reduced prevalence of Mn 3+ in LMNO. Mn 3+ gives rise to pronounced Jahn-Teller (JT) distortion and Mn dissolution via disproportionation reactions (2Mn 3+ → Mn 2+ + Mn 4+ ) leading to structural instability. Depending on synthesis conditions, LMNO can show site disorder in the octahedral TM cation sites (see Figure ). A lower synthesis/anneal temperature (∼700 °C) leads to the formation of the ordered (P 4 3 32) phase, where Ni and Mn are located at 4b and 12d Wyckoff sites. In the ideal P 4 3 32 LMNO, all Mn species present as redox-inactive Mn 4+ . The Ni 2+ /Ni 4+ couple gives rise to a distinctive voltage at ∼4.7 V. Higher synthesis temperatures (> 700 °C) promote the formation of the F d3m LMNO with Mn and Ni disordered across the 16d sites. High temperature synthesis may also drive oxygen vacancy formation, which is expected to be compensated by the reduction of Mn 4+ to Mn 3+ , leading to an off-stoichiometric composition (LiMn 1.5 Ni 0.5 O 4-δ ) with the formation of rock-salt phase (e.g. Li x Ni 1-x O) impurities. Mn 3+ is redox active and the Mn 3+ /Mn 4+ redox reaction introduces an additional plateau at ∼4 V on the voltage profile. The disordered phase generally exhibits better cycling stability and rate capability than the ordered phase, however the connection between disorder and performance has remained unclear, with increasing attention placed on understanding the role of cation disorder. While some studies found that Mn/Ni disorder increases with oxygen vacancy and Mn 3+ formation, others have suggested that the "disordered" phase from different studies is likely to be samples with partial cation disordering, a varying degree of oxygen content and impurity phases. Regardless, the correlation between cation disorder and oxygen content has made it difficult to distinguish the key driving factor for improved performance, illustrating the need to decouple these effects and study their impacts independently.