Yolk–shelled cathode materials with extremely high electrochemical performances prepared by spray pyrolysis

Abstract

A facile, continuous preparation process of yolk–shell-structured lithium–metal oxide powders without a template for use as cathode materials in lithium ion batteries is introduced for the first time. Single and double-shelled LiNi_0.5Mn_1.5O₄ yolk–shell powders as the first target materials are prepared directly by spray pyrolysis from a spray solution with sucrose, at a short residence time of 4 s. Fast combustion and contraction of a carbon-mixed oxide composite intermediate, formed from a micro-sized droplet inside a hot wall reactor maintained at 700 °C, produces the yolk–shell powders. The yolk–shell structure of the precursor powders directly prepared by spray pyrolysis is well maintained even at a high post-treatment temperature of 750 °C. The yolk–shell LiNi_0.5Mn_1.5O₄ powders delivered a 1000^th high discharge capacity of 108 mA h g⁻¹ at 10 C. The discharge capacities are as high as 103, 95, and 91 mA h g⁻¹ at extremely high discharge rates of 100, 200, and 300 C and the corresponding specific energy densities are 420, 370, and 328 W h kg⁻¹. The capacity retention at a constant discharge rate of 200 C is 90% after 500 cycles.