Surface Free Energy‐Induced Assembly to the Synthesis of Grid‐Like Multicavity Carbon Spheres with High Level In‐Cavity Encapsulation for Lithium–Sulfur Cathode

Abstract Carbon microcapsules with a large interior cavity and porous shell are ideal hosts for guest species, while to maximize in‐cavity volume has always been a challenge. Herein, a surface free energy‐induced assembly approach is proposed for synthesis of multicavity carbon spheres (MCC). When used as a host for lithium–sulfur cathodes, MCC are fully accessible for sulfur—with high level in‐cavity encapsulation ability of grid‐like cavities. The crucial point for this assembly approach is the employment of small sized nanoemulsions with high homogeneity as primary building blocks. Spontaneous aggregation and assembly of substructural units are processing in following hydrothermal synthesis induced by reduction of surface free energy of system. As a result, multicavity structure is formed, where the size and number of cavities can be modulated by changing size of nanoemulsion and concentration of polymer. Confined pyrolysis enables to further enlarge cavity size compared to regular pyrolysis. The carbon–sulfur cathode exhibits excellent cycling stability and rate performance, i.e., high capacity of 943 and 869 mA h g −1 after 200 cycles at current density of 0.5 and 2.0 C. The strategy has paved the way for custom‐ordered synthesis of nanostructured carbon with keen demands in high loading capacity of guest species.