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

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.