Investigation on the Electrochemical Properties of Antimony Tin Oxide Nanoparticle-Modified Graphene Aerogel as Cathode Matrix in Lithium-Sulfur Battery

摘要

Lithium-sulfur (Li-S) batteries are considered the most appealing secondary batteries attributed to the ultrahigh theoretical specific capacity as 1675 mA.h.g(-1) for elemental sulfur cathode. Nevertheless, there are still several disadvantages (sulfur insulation, insoluble lithium polysulfide, shuttle effect, etc.) impeding the commercial application of Li-S batteries. Recent studies have discovered that nanosized metal oxides can effectively modify the electrochemical properties of composite cathodes in Li-S batteries. In this paper, graphene aerogels (GA) loaded with different mass fractions of antimony tin oxide (ATO) nanoparticles were incorporated with sulfur and utilized as cathode materials for Li-S batteries. The sample (GA/ATO-3) loaded with 3 wt.% ATO nanoparticles showed the best electrochemical performance. For example, the specific discharge capacity of first cycle reached 1210 mA.h.g(-1) under a current of 0.1 C. The reversible discharge capacity was reduced to 545 mA.h.g(-1) after 50 cycles, namely, the corresponding capacity retention rate was approximately 50%. However, the coulombic efficiency was still near 100%. Potential modification mechanism was considered to be a combination between the GA with excellent conductivity, which effectively improved the internal conductivity of the cathode material, and the ATO nanoparticles, which improved the distribution uniformity of the solid sulfur and its sulfurized product because the ATO nanoparticles acted as heterogeneous nucleation points. Furthermore, the ATO nanoparticles with strong polarity possessed a strong capture ability on the soluble polysulfide ions. For the above reasons, the ATO-loaded GA cathode could effectively inhibit the "shuttle effect," thereby, improved the electrochemical performance of Li-S batteries.