Li and Na storage behavior of bowl-like hollow Co3O4 microspheres as an anode material for lithium-ion and sodium-ion batteries

• A unique bowl-like hollow spherical Co3O4 structure is prepared through a simple, low-cost and mass-yield method.
• Such a bowl-like hollow Co3O4 microsphere demonstrates extraordinary rate and cycling performance for Li-storage.
• The sodium-storage behavior of Co3O4 is investigated for the first time.

Bowl-like hollow Co3O4 microspheres are prepared via a simple and low-cost route by thermally treating Co-containing resorcinol-formaldehyde composites gel in air. Scanning electron microscopy, transmission electron microscope and N2 adsorption-desorption measurements demonstrate that these bowl-like hollow Co3O4 microspheres are composed of hollow inner cavities and outer shell walls (70 nm thickness), on which a considerable amount of mesopores centered around 5-17 nm size are distributed. When employed as the anode material for lithium-ion batteries, these bowl-like hollow Co3O4 microspheres exhibit extraordinary cycling performance (111% retention after 50 cycles owing to capacity rise), fairly high rate capacity (650 mAh g−1 at 5 C) and enhanced lithium storage capacity. Meanwhile, the Na-storage behavior of Co3O4 as an anode material of Na-ion batteries is initially investigated based on such a hollow structure and it exhibits similar feature of discharge/charge profiles and a high initial discharge capacity but relatively moderate capacity retention compared with the Li-storage performance.