A new method of pretreatment of lithium manganese spinels and high-rate electrochemical performance of Li[Li0.033Mn1.967]O4

Abstract

Lithium manganese spinels tend to aggregate upon annealing and do not allow for attaining high discharge rates when used as cathodes in lithium-ion batteries. To obtain spinel samples of lower aggregation and better high-rate properties, precursors synthesized by means of a citric acid-aided route are suggested to be pyrolyzed in an inert atmosphere, instead of pyrolysis in air. The synthesis of nanosized Li[Li0.033Mn1.967]O4 is described, and its characteristics including X-ray diffraction, scanning electron microscopy, and porosity, as well as electrochemical test results are presented. The particle size of the materials obtained is smaller, the degree of aggregation is lower, and high-rate properties are better than for analogues pyrolyzed in air. In particular, sample Li||Li[Li0.033Mn1.967]O4 cells deliver ~60 mAh g-1 at the current loads of 4,000 mA g-1 (30 C). After a sequence of 62 charge/discharge cycles with the currents growing from 0.1 to 100 C the specific capacity retains its initial value.