A computational study on bifunctional 1T-MnS2 with an adsorption-catalysis effect for lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries are promising rechargeable energy storage systems with a high energy density, environmental friendliness and low cost. However, the commercialization process of Li-S batteries has been seriously hindered by the shuttling of lithium polysulfides (LiPSs) and the sluggish kinetics of conversion reaction among sulfur species. In this work, the adsorption-catalysis performance of five transition metal disulfide 1T-MS2 (M = Mn, V, Ti, Zr, and Hf) surfaces is investigated by evaluating the adsorption energy of sulfur species, Li-ion diffusion energy barrier, decomposition energy barrier of Li2S, and the Gibbs free energy barrier of the sulfur reduction reaction based on first-principles calculations. Our results show that the sulfiphilicity of 1T-MS2 plays an important role in the adsorption behavior of short-chain sulfur species, in addition to lithiophilicity. Remarkably, among the five 1T-MS2 materials, our results confirm that 1T-TiS2 and 1T-VS2 show excellent adsorption-catalysis performance and it is predicted that 1T-MnS2 is an even better candidate catalyst to inhibit the shuttle effect and accelerate delithiation/lithiation kinetics. Moreover, the outstanding performance of 1T-MnS2 persists in a solvent environment and under strain modulation. Our results not only demonstrate that 1T-MnS2 is an excellent potential catalyst for high-performance Li-S batteries, but also provide great insights into the adsorption-catalysis mechanism during the cycling process.

Direct Monitoring of Li2 S2 Evolution and Its Influence on the Reversible Capacities of Lithium-Sulfur Batteries.

The polysulfide (PS) dissolution and low conductivity of lithium sulfides (Li2 S) are generally considered the main reasons for limiting the reversible capacity of the lithium-sulfur (Li-S) system. However, as the inevitable intermediate between PSs and Li2 S, lithium disulfide (Li2 S2 ) evolutions are always overlooked. Herein, Li2 S2 evolutions are monitored from the operando measurements on the pouch cell level. Results indicate that Li2 S2 undergoes slow electrochemical reduction and chemical disproportionation simultaneously during the discharging process, leading to further PS dissolution and Li2 S generation without capacity contribution. Compared with the fully oxidized Li2 S, Li2 S2 still residues at the end of the charging state. Therefore, instead of the considered Li2 S and PSs, slow electrochemical conversions and side chemical reactions of Li2 S2 are the determining factors in limiting the sulfur utilization, corresponding to the poor reversible capacity of Li-S batteries.

Lithium Atom Surface Diffusion and Delocalized Deposition Propelled by Atomic Metal Catalyst toward Ultrahigh-Capacity Dendrite-Free Lithium Anode.

Lithium metal anode possesses overwhelming capacity and low potential but suffers from dendrite growth and pulverization, causing short lifespan and low utilization. Here, a fundamental novel insight of using single-atomic catalyst (SAC) activators to boost lithium atom diffusion is proposed to realize delocalized deposition. By combining electronic microscopies, time-of-flight secondary ion mass spectrometry, theoretical simulations, and electrochemical analyses, we have unambiguously depicted that the SACs serve as kinetic activators in propelling the surface spreading and lateral redistribution of the lithium atoms for achieving dendrite-free plating morphology. Under the impressive capacity of 20 mA h cm-2, the Li modified with SAC-activator exhibits a low overpotential of ∼50 mV at 5 mA cm-2, a long lifespan of 900 h, and high Coulombic efficiencies during 150 cycles, much better than most literature reports. The so-coupled lithium-sulfur full battery delivers high cycling and rate performances, showing great promise toward the next-generation lithium metal batteries.

Lithium Storage Mechanism and Application of Micron-Sized Lattice-Reversible Binary Intermetallic Compounds as High-Performance Flexible Lithium-Ion Battery Anodes.

A strategy of lattice-reversible binary intermetallic compounds of metallic elements is proposed for applications in flexible lithium-ion battery (LIB) anode with high capacity and cycling stability. First, the use of metallic elements can ensure excellent electronic conductivity and high capacity of the active anode substance. Second, binary intermetallic compounds possess a larger initial lattice volume than metallic monomers, so that the problem of volume expansion can be alleviated. Finally, the design of binary intermetallic compounds with lattice reversibility further improves the cycle stability. In this work, the feasibility of this strategy is verified using an indium antimonide (InSb) system. The volumetric expansion and lithium storage mechanism of InSb are investigated by in situ Raman characterization and theoretical calculations. The active material utilization is significantly improved and the growth of In whiskers is inhibited in the micron-sized ball-milled and carbon coated InSb (bInSb@C) anode, which exhibits a reversible capacity of 733.8 mAh g-1 at 0.2 C, and provides a capacity of 411.5 mAh g-1 after 200 cycles at 3 C with an average Coulombic efficiency of 99.95%. This strategy is validated in pouch cells, illustrating the great potential of lattice-reversible binary intermetallic compounds for use as commercial flexible LIB anodes.

Multi-ion Modulated Single-Step Synthesis of a Nanocarbon Embedded with a Defect-Rich Nanoparticle Catalyst for a High Loading Sulfur Cathode.

Oxygen defect-rich iron oxide (ODFO) nanoparticle catalyst on nanocarbon is in situ synthesized with the assistance of multi-ion modulation in one pot. The nanoparticle catalyst is employed to propel electrochemical kinetics in lithium/sulfur batteries. Electrochemical analysis and theoretical simulation evidently verify the critical role of defect sites on catalyzing conversion reactions of sulfur species and reducing energy barriers. As a consequence, the ODFO-enhanced sulfur cathode exhibits a high specific capacity of 1489 mA h g-1 at 0.1 C, an excellent rate performance of 644 mA h g-1 at 10 C, and a superior cycling stability with an average capacity fading rate of as low as 0.055% per cycle under an ultrahigh rate of 10 C. More importantly, even with a high sulfur loading of 11.02 mg cm-2, the Li/S cell can still deliver an areal capacity of 8.7 mA h cm-2 at 0.5 C (9.23 mA cm-2). Such performance is the highest among reported metal oxide-catalyzed sulfur cathodes. This work opens a new route to boosting conversion reaction kinetics by introduction of active oxygen defect sites in electrodes of various emerging ultrafast batteries.

Identification of the absorbed components and their metabolites of Tianma-Gouteng granule in rat plasma and bile using ultra-high-performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry.

Tianma-Gouteng granule (TGG), a Chinese herbal formula preparation, is clinically used for the treatment of cardio-cerebrovascular diseases such as hypertension, cerebral ischaemia, acute ischaemic stroke and Parkinson's disease. Although few reports have been published concerning the absorbed prototype components of TGG, the possible metabolic pathways of TGG in vivo remain largely unclear. In this study, a method using UPLC-Q/TOF MS was established for the detection and identification of the absorbed prototype components and related metabolites in rat plasma and bile after oral administration of TGG at high and normal clinical dosages. A total of 68 components were identified or tentatively identified in plasma and bile samples, including absorbed prototypes and their metabolites. The major absorbed components were gastrodin, isorhynchophylline, rhynchophylline, isocorynoxeine, corynoxeine, geissoschizine methyl ether baicalin, baicalein, wogonoside, wogonin, geniposidic acid, leonurine, 2,3,5,4'-tetrahydroxystilbene-2-O-ß-d-glucoside and emodin. The main metabolic pathways of these components involved phase I (isomerization, hydrolysis and reduction) and phase II (glucuronidation and sulfation) reaction, and the phase II biotransformation pathway was predominant. The present study provides rich information on the in vivo absorption and metabolism of TGG, and the results will be helpful for further studies on the pharmacokinetics and pharmacodynamics of TGG.