Formation of carbon coated yolk-shelled Fe3O4-CeO2 hollow spheres toward remarkable performance supercapacitors

Yolk-shelled hollow structures with unique structural features are incredibly attractive for energy storage systems . Here we present a self-template strategy to prepare carbon coated yolk-shelled Fe 3 O 4 -CeO 2 hollow spheres. First, yolk-shelled Fe-Ce glycerate precursors are designed by a solvothermal method. Afterward, the carbon coated yolk-shelled Fe 3 O 4 -CeO 2 hollow spheres are eventually synthesized via calcinations the obtained precursors in Ar. Such unique structures endow the Fe 3 O 4 -CeO 2 with abundant inner cavities, large surface area and more electroactive site. As electrode material for supercapacitors , a large capacity of 430 C g −1 is obtained at 2.0 A g −1 , and it can be as high as 198.4 C g −1 even at 20 A g −1 . Moreover, it also takes outstanding rate capability and superior cycling durability (only 5.2 % capacity reduction over 5000 cycles at 6.0 A g −1 ). Furthermore, a quasi-solid-state flexible asymmetric supercapacitor device is constructed by Fe 3 O 4 -CeO 2 cathode and activated carbon anode . The device manifests a high energy density of 46.6 Wh kg −1 at 2.0 A g −1 ( versus 1650 W kg −1 power density). Even at 15 A g −1 , the energy density is still 21 Wh kg −1 with 12,441 W kg −1 . We envision that this work not only explores a promising electrode material for supercapacitors, but also provides an alternative avenue to prepare yolk-shelled hollow structures toward energy storage applications .