Pomegranate-like shell structured Si@C with tunable inner-space as an anode material for lithium-ion battery

In this work, pomegranate-like shell structured Si@C material with tunable inner-space is designed and synthesized through a self-assembly and excess reduction approach for the first time. Through adjusting the quantity of reactants, the ratio of shell thickness to inner space radius in the hollow structure is optimally tuned. Moreover, the process not only possesses high conversion yield (>90%) but also is environmentally friendly. In this architecture, the void space in the hollow structure and the mechanically constraining carbon layer outside the spheres can synergistically accommodate the huge volume changes during cycling. Combining these characteristics, the Si@C anode affords comprehensively excellent performance, such as a high reversible capacity of 1494 mA h g⁻¹, outstanding cycling stability with the capacity retention over 100 cycles of nearly 97% at 100 mA g⁻¹, 96% at 500 mA g⁻¹ and over 200 cycles of about 92% at 1 A g⁻¹, 85% at 2 A g⁻¹ and superior rate performance with a reversible capacity of 908 mA h g⁻¹ at a high current density of 2 A g⁻¹. Significantly, the areal capacity of Si@C electrode is as high as 3.47 mA h cm⁻² at a high mass loading of 2.32 mg cm⁻².