RESUMO
The commercialization of lithium-sulfur batteries is facing great challenges, such as the "shuttle effect" and the poor conductivity of sulfur and Li2S2/Li2S, so it is extremely important to design new separator-modified materials with fast charge transfer capability and effective immobilization of polysulfides (LiPSs) to facilitate their conversion to address these challenges. In this paper, we propose a simple way to synthesize NiCo2O4 nanospheres containing oxygen vacancies (OV-NiCo2O4 NSs) and thus modify the separator. The synthesized OV-NiCo2O4 NSs accelerated the conversion of LiPSs through strong chemical interactions. In addition, the introduction of oxygen vacancies provided more active sites for LiPSs, which improved the electron conduction rate and accelerated the ion transport. Based on the above advantages, the battery with an OV-NiCo2O4 modified separator showed excellent electrochemical performance (the initial capacity of the battery was 801 mA h g-1 at 0.5 C, the specific capacity of discharge was maintained at 695 mA h g-1 after 500 cycles, and the capacity retention rate was as high as 87%).
RESUMO
Lithium-sulfur (Li-S) batteries are known as a prospective new generation of battery systems owing to their high energy density, low cost, non-toxicity, and environmental friendliness. Nevertheless, several issues remain in the practical application of Li-S batteries, such as low sulfur usage, poor rate performance, and poor cycle stability. Ordered microporous carbon materials and carbon nanotubes (CNTs) can effectively limit the diffusion of polysulfides (LiPSs) and have high electrical conductivity, respectively. Here, inspired by the evaporation of zinc at high temperatures, we constructed CNTs interpenetrating ordered microporous carbon nanospheres (CNTs/OMC NSs) by high-temperature calcination and used them as a sulfur host material. With the benefit from the excellent electrical conductivity of CNTs and OMC achieving uniform sulfur dispersion and effectively limiting LiPS dissolution, the S@CNTs/OMC NS cathodes show outstanding cycling stability (initial discharge capacity of 879 mAh g-1 at 0.5 C, maintained at 629 mAh g-1 for 500 cycles) and excellent rate performance (521 mAh g-1 at 5.0 C). Furthermore, the current study can serve as a significant reference for the synthesis of CNTs that interpenetrate various materials.
