RESUMO
Lithium-sulfur (Li-S) batteries are highly attractive for their theoretical energy density and natural abundance, but the drawbacks of low sulfur utilization and rapid capacity fade in high-sulfur-loading cathodes still retard their practical use. To enhance kinetics in high-sulfur-loading Li-S cells, it is important to first understand and control the deposition of Li2S/Li2S from highly soluble lithium polysulfide (LiPS) during discharge processes. Here, we presented a series of multiphase-derived self-standing papers with diverse electronic conductivity and LiPS affinity for highly concentrated LiPS discharge processes and explained the Li2S/Li2S deposition behavior in detail. We demonstrated that high rate capacity and long cycle life of as-assembled paper-LiPS cathodes can be greatly depended on their phase material with high conductivity and LiPS affinity. A high-performance self-standing LiPS host-multiwalled carbon nanotube (MWCNT)/cellulose nanofiber (CNF)/NiCo2S4 (3.5 mg cm-2) can catalyze 2.85 mg cm-2 (based on sulfur) loaded LiPS to deliver a high specific capacity of 1154 mAh g-1 at 0.1C and a high rate performance of 963 mAh g-1 at 1C. We suggest that the insulating phase defect of nano-CNF and both highly electronic conductive (above 50 S cm-1) and LiPS adsorptive NiCo2S4 can promote the local concentration effect of LiPS, thus contributing to fast and stable heterogeneous particle-shaped deposition of Li2S2/Li2S and leading to high kinetics of the LiPS cathode.
RESUMO
Previously, we found that Celastrus orbiculatus Thunb. (COT) decreases athero-susceptibility in lipoproteins and the aorta of guinea pigs fed a high-fat diet, and increases high-density lipoprotein (HDL). In the present study, we investigated the effect of COT in reducing lipid accumulation and promoting reverse cholesterol transport (RCT) in vivo and vitro. Healthy male mice were treated with high-fat diet alone, high-fat diet with COT (10.0 g/kg/d), or general fodder for 6 weeks. Serum levels of total cholesterol (TC), triglyceride (TG), HDL-C, non-HDL-C, and (3)H-cholesterol in plasma, liver, bile, and feces were determined. Pathological changes and the levels of TC and TG in liver were examined. The expression of hepatic genes and protein associated with RCT were analyzed. COT administration reduced lipid accumulation in the liver, ameliorated the pathological changes, and lessened liver injury, the levels of TG, TC, and non-HDL-C in plasma were decreased significantly, and COT led to a significant increase in plasma HDL-C and apolipoprotein A (apoA1). (3)H-cholesterol in plasma, liver, bile, and feces was also significantly increased in COT-treated mice compared to controls. Both mRNA and protein expression of SRB1, CYP7A1, LDLR, ATP-binding cassette transporters ABCA1, ABCG5, and LXRα were improved in COT-treated mice. An in vitro isotope tracing experiment showed that COT and its bioactive ingredients, such as celastrol, ursolic acid, oleanolic acid, and quercetin, significantly increased the efflux of (3)H-cholesterol. They also increased the expression of SRB1, ABCA1, and ABCG1 significantly in macrophages. Our findings provided a positive role of COT in reducing lipid accumulation by promoting RCT. These effects may be achieved by activating the SRB1 and ABC transporter pathway and promoting cholesterol metabolism via the CYP7A1 pathway in vivo. The effective ingredients in vitro are celastrol, ursolic acid, oleanolic acid, and quercetin.
