Controllable Synthesis of Carbon Yolk-Shell Microsphere and Application of Metal Compound-Carbon Yolk-Shell as Effective Anode Material for Alkali-Ion Batteries.

Recently, nanostructured carbon materials, such as hollow-, yolk-, and core-shell-configuration, have attracted attention in various fields owing to their unique physical and chemical properties. Among them, yolk-shell structured carbon is considered as a noteworthy material for energy storage due to its fast electron transfer, structural robustness, and plentiful active reaction sites. However, the difficulty of the synthesis for controllable carbon yolk-shell has been raised as a limitation. In this study, novel synthesis strategy of nanostructured carbon yolk-shell microspheres that enable to control morphology and size of the yolk part is proposed for the first time. To apply in the appropriate field, cobalt compounds-carbon yolk-shell composites are applied as the anode of alkali-ion batteries and exhibit superior electrochemical performances to those of core-shell structures owing to their unique structural merits. Co O -C hollow yolk-shell as a lithium-ion battery anode exhibits a long cycling lifetime (619 mA h g for 400 cycles at 2 A g ) and excellent rate capability (286 mA h g at 10 A g ). The discharge capacities of CoSe -C hollow yolk-shell as sodium- and potassium-ion battery anodes at the 200th cycle are 311 mA h g at 0.5 A g and 268 mA h g at 0.2 A g , respectively.