Negative and positive electrode materials for lithium-ion batteries

MnV2O6 + δ5 (0.5 < δ < 1) amorphous oxides reversibly insert large amounts of Li (e.g. Li12MnV2O6.96) at low voltage (≈ 1 V). During the first Li insertion, Mn4+ is first reduced to Mn2+ and V5+ is reduced to V3+. Upon further cycling, the V oxidation state varies reversibly between +3 and +5, whereas the average Mn oxidation state varies reversibly between +2 and ~+2.6. Reversible lithium deintercalation of LiCryMn2 − yO4 (0 < y < 1) occurs in two steps at ≈ 4.9 V and 4 V. The cyclability is excellent for y≤ 0.5. It becomes very poor for y ≥ 0.75 due to a migration of transition metal cations from 16d to 8a and I6c sites, where they accumulate upon cycling.