n the extended chiral constituent quark model, the intrinsic cc content of the nucleon is investigated. The probabilities of the quark-antiquark components in the nucleon wave functions are ...calculated by taking the nucleon to be admixtures of three- and five-quark components, with the relevant transitions handled via the super(3)P sub(0) mechanism. Predictions for the probability of the cc in the nucleon wave function and the charmness-nucleon sigma term are presented. Our numerical results turn out to be consistent with the predictions from various other approaches reported in the literature.
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.
Oxygen-vacant niobium oxide electrocatalyst on a high-conductive hierarchical porous nanocarbon (AOV-Nb2O5-x@HHPC) composites is developed as the sulfur species catalyzer and lithium ion accelerator ...by forming the Nb-S bonds. The as-prepared sulfur cathode shows excellent rate and cycling capability. Even under 4.2 mg cm−2 and lean electrolyte/sulfur ratio, the pouch cell delivers a high areal capacity retention and stabilizes for several tens of cycles.
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•Oxygen-vacant niobium oxide electrocatalyst is developed as the sulfur species catalyzer and lithium ion accelerator.•Theoretical simulations and electrochemical results reveal the catalytic effect is realized by forming the Nb-S bonds.•The as-prepared sulfur cathode shows excellent rate and cycling capability.•With lean electrolyte, the high-mass-loading pouch cell delivers a high areal capacity retention.
The development of lithium/sulfur batteries has been hindered by notorious shuttling effect and sluggish electrochemical conversion kinetics owing to high barrier of lithium ion transport behaviors. In this work, anionic oxygen vacancies in niobium oxide nanoparticle is fabricated on a high-conductive hierarchical porous nanocarbon as a sulfur anchor and lithium ion accelerator. As evidenced by optical coloration and electrochemical measurements, the oxygen-deficient electrocatalyst shows much stronger interaction ability to polysulfides and endows superior catalytic ability of propelling ion kinetics and facilitating the precipitation of Li2S. Theoretical simulations have also revealed that Nb-S bonds are formed when polysulfides interacts with AOV-Nb2O5-x catalyst. Consequently, the as-prepared sulfur cathode exhibits a high initial capacity of 1489 mA h g−1, corresponding to the theoretical utilization of 89%, and a long life for 600 cycles at 1 C. Enhancing current rate to 5 C, a rate capacity of 899 mA h g−1 is obtained, demonstrating rapid conversion kinetics. Impressively, even increasing the areal loading to 4.2 mg cm−2 with the lean electrolyte, the pouch cell can still exhibit the initial areal capacity of 3.54 mA h cm−2 at 0.343 mA cm−2 and stabilize for several tens of cycles, providing the promise for fast-charge 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.
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-MS
2
(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 Li
2
S, and the Gibbs free energy barrier of the sulfur reduction reaction based on first-principles calculations. Our results show that the sulfiphilicity of 1T-MS
2
plays an important role in the adsorption behavior of short-chain sulfur species, in addition to lithiophilicity. Remarkably, among the five 1T-MS
2
materials, our results confirm that 1T-TiS
2
and 1T-VS
2
show excellent adsorption-catalysis performance and it is predicted that 1T-MnS
2
is an even better candidate catalyst to inhibit the shuttle effect and accelerate delithiation/lithiation kinetics. Moreover, the outstanding performance of 1T-MnS
2
persists in a solvent environment and under strain modulation. Our results not only demonstrate that 1T-MnS
2
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.
1T-MnS
2
exhibits excellent adsorption-catalysis activity for Li-S batteries, which can enhance the adsorption for polysulfides and accelerate the oxidation of Li
2
S and sulfur reduction reaction.
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-MS
(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 Li
S, and the Gibbs free energy barrier of the sulfur reduction reaction based on first-principles calculations. Our results show that the sulfiphilicity of 1T-MS
plays an important role in the adsorption behavior of short-chain sulfur species, in addition to lithiophilicity. Remarkably, among the five 1T-MS
materials, our results confirm that 1T-TiS
and 1T-VS
show excellent adsorption-catalysis performance and it is predicted that 1T-MnS
is an even better candidate catalyst to inhibit the shuttle effect and accelerate delithiation/lithiation kinetics. Moreover, the outstanding performance of 1T-MnS
persists in a solvent environment and under strain modulation. Our results not only demonstrate that 1T-MnS
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.
The polysulfide (PS) dissolution and low conductivity of lithium sulfides (Li2S) 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 Li2S, lithium disulfide (Li2S2) evolutions are always overlooked. Herein, Li2S2 evolutions are monitored from the operando measurements on the pouch cell level. Results indicate that Li2S2 undergoes slow electrochemical reduction and chemical disproportionation simultaneously during the discharging process, leading to further PS dissolution and Li2S generation without capacity contribution. Compared with the fully oxidized Li2S, Li2S2 still residues at the end of the charging state. Therefore, instead of the considered Li2S and PSs, slow electrochemical conversions and side chemical reactions of Li2S2 are the determining factors in limiting the sulfur utilization, corresponding to the poor reversible capacity of Li‐S batteries.
A series of operando spectral results reveal that Li2S2 undergoes chemical reactions accompanied by its electrochemical conversions during operation for the first time. The chemical reactions related to Li2S2 can increase polysulfide dissolution and Li2S generation without capacity contribution. Instead of the commonly considered Li2S, Li2S2 is the solid “dead” sulfur species and restricts the actual sulfur utilization and reversible capacity.
The volumetric energy density of lithium–sulfur (Li–S) batteries is particularly important to accommodate the ever-shrinking space of practical devices. A feasible path for improving the volumetric ...energy density of the cathode is to increase the utilization of active materials within a limited volume. However, the sluggish conversion kinetics and severe migration of polysulfides hinder its development. Herein, different from simple additives with large aggregation, we propose
in situ
growth of ultra-small tungsten carbide nanoparticles on highly conductive nanocarbon in a relatively low-temperature process. As evidenced by the comprehensive density functional theory (DFT) calculations, X-ray photoelectron spectroscopy (XPS) and electrochemical kinetic analyses, the
in situ
formed WC nanoparticles could strongly enhance the absorption ability of the sulfur species and reduce the reaction energy barriers, boosting the whole interconversion kinetics. Benefiting from these advantages, the as-synthesized hybrid cathode delivered a high rate capability of 6C (627 mA h g
−1
) and enabled a long-term cycling lifespan of 500 cycles with a low decay rate of 0.039% at 5C. Moreover, a high volumetric capacity up to 625 mA h cm
−3
(volumetric energy density of 1312 W h L
−1
) was reached at the cathode-level with a high sulfur loading of 5.9 mg cm
−2
at 1C, suggesting a great promise in the development of Li–S batteries with high volumetric energy density.
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•Interfacial catalytic “Li-N” bond bridges are constructed.•The kinetics of sulfide oxidation reactions is significantly accelerated by Li-N catalytic sites.•The so-fabricated ...catalytic cathode exhibits long life and rate performance.•The high-content high-loading cells delivers comparable rate and cycling areal capacity.
Lithium sulfur batteries have exhibited unparalleled advantages in energy density. However, the sulfide oxidation reactions (SORs) in sulfur cathode are much more sluggish, which is mainly restricted by high conversion barriers. Herein, the catalytic “Li-N” bond sites are designed to activate SORs in high areal loading cathode with the multi-functions of bridging the active materials and carbon matrix tightly. The presence of catalytic “Li-N” bonds is co-revealed by X-ray photoelectronic spectroscopy and electronic energy loss spectroscope. As unraveled by theoretical physical van der Waals interaction analysis and various electrochemical tests, the improved kinetics and mechanism of SORs are achieved by motivating polysulfide interconversions and propelling lithium ion diffusion. Consequently, the so-fabricated electrode with abundant Li-N bond catalytic sites deliveries 900 mA h g−1 at 0.05 C and a stable retention of 74.3% at 1 C after 300 cycles. More impressively, high-loading with high-weight-content cathodes remain rapid SORs kinetics, high capacity utilization and retention from 3.0 to 6.9 mg cm−2. At 6.5 mg cm−2, the cathode displays 550 mA h g−1 at 0.76 mA cm−2 corresponded to 3.58 mA h cm−2, which is better than many reports. These results shed light on using intrinsic catalytic sites to realize application of batteries.
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