Gas template-assisted spray pyrolysis: A facile strategy to produce porous hollow Co₃O₄ with tunable porosity for high-performance lithium-ion battery anode materials

Porous hollow Co₃O₄ microspheres have been synthesized from a mixed cobalt nitrate and urea solution through spray pyrolysis followed by calcination at 600 ℃ in air. This porous hollow Co₃O₄ is assembled by nanoparticles and exhibits variable porosity depending on the amount of gas in the system. In pyrolysis process, urea continuously decomposes into gaseous components, which act as a template to control the porous structure. The amount of gas escaping from precursor droplets can directly influence the porosity of the microspheres and the size of the nanoparticles controlled by the ratio of urea to cobalt nitrate. Electrochemical measurements show that the performance of the porous hollow Co₃O₄ microspheres is related to the porosity and size of the nanoparticles. The sample with optimal porosity delivers a high first charge capacity of 1, 417.9 mAh·g^-1 at 0.2C (1C = 890 mA·g^-1), and superior charge cycle performance of 1, 012.7 mAh·g^-1 after 100 cycles. In addition, the optimized material displays satisfactory rate performance of 1, 012.4 mAh·g^-1 at 1C after 50 cycles and 881.3 mAh·g^-1 at 2C after 300 cycles. Superior charge/discharge capacity, excellent rate performance and high yield achieved in this study is promising for the development of high-performance Co₃O₄ anode materials for lithium-ion batteries.