The effect of ammonia reduction on the spinel electrode materials, LiMn2O4 and Li(Li1/3Mn5/3)O4

摘要: Abstract Treating the lithium manganese oxide spinels, LiMn2O4 and Li ( 1 3 Mn 5 ) O 4 with ammonia at elevated temperatures causes oxygen loss. The reaction between these materials as a function of temperature has been studied using X-ray diffraction Thermal Gravimetric Analysis (TGA). Electrochemical studies subsequent deintercalation from have made Li/non-aqueous electrolyte/spinel cells. Very little can be removed (synthesized 750°C) by NH3 reduction before disproportionation to Li2Mn2O4 Mn3O4 occurs. By contrast, treatment (both synthesized 400°C) near 200°C removes without inducing phase change. For , product is best characterized 4−δ δ large 0.25. Unlike (prepared 750°C), where half in 3+ oxidation state almost all electrochemically, very (all Mn4+) because it apparently difficult oxidize atoms beyond 4+ state. When increases, average decreases then substantial deintercalated. Similarly, reducing increases amount which extracted material. These results demonstrate striking effect Mn:O ratio, or equivalently state, on electrochemical behavior Li/spinel