Interconnected hollow carbon spheres with tunable wall-thickness for improving the high-rate performance of energy storage devices

Highlights: • A facile synthesis of hollow carbon spheres is developed by forming the hard template in-situ. • The interconnected carbon spheres effectively reduce the contact resistance. • The wall thickness of the hollow carbon spheres can be easily tuned to enhance rate performances. • The sample with 9 nm wall-thickness demonstrate 208 F g⁻¹ at 1 A g⁻¹ in supercapacitors. • The sulfur composite electrode exhibits highest capacity of 996 mAh g⁻¹ at 0.2C for Li-S batteries. -- Abstract: We report a facile synthetic method to produce the interconnected hollow carbon spheres with various wall-thickness (as low as 9 nm). Instead of synthesizing and dispersing the silica hard templates in advance, we produce the templates in-situ to form the interconnected hollow-sphere structure. This interconnected structure provides a fast and efficient pathway for electron transfer. Meanwhile, decreasing the wall-thickness effectively shortens the distance of ion diffusion, which further promotes the high-rate performances of the interconnected hollow carbon spheres. For supercapacitor applications, at 1 A g⁻¹, the MF-1.1-20 (with 9-nm wall-thickness) electrode demonstrates a high specific capacitance of 208 F g⁻¹ and retains 93% of its initial capacity after 10000 cycles. Under a large current density of 20 A g⁻¹, MF-1.1-20's specific capacity remains 153 F g⁻¹, demonstrating excellent high-rate performances. In another aspect, as the electrode for lithium-sulfur battery, MF-1.1-20/S composite electrode demonstrates high specific capacity of 996 mAh g⁻¹ and 465 mAh g⁻¹ at 0.2C and 10C, respectively. The excellent electrochemical behavior of the interconnected hollow carbon spheres demonstrates their potential for applications in high-rate energy storage devices.