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In this study, the geometric structure, strain energy, and electronic properties of armchair C 2 O nanotubes (A _ C 2 O N T s (n , n)) and zigzag C 2 O nanotubes   (Z _ C 2 O N T s (n , 0)) are studied in detail. The results show that these nanotubes behave as special shapes; the section of Z _ C 2 O N T s (n , 0) along the axial direction is an n-edge type, and the section tends to be round with an increase in n while the boundary of section along the axial direction for A _ C 2 O N T s (n , n) fluctuates. With an increase in n, the fluctuation disappears gradually, and the section also tends to be round. Compared with C 2 O nanosheets ( g _ C 2 O ), C 2 O nanotubes have similar or even smaller strain energy, when the tube diameter is greater than or equal to 15 Å , the strain energy begins to show a negative value, and the negative value tends to be stable as the pipe diameter increases. Z _ C 2 O N T s start to show negative strain energies from n = 8 and A _ C 2 O N T s from n = 12, indicating their higher stabilities relative to the   g _ C 2 O sheets. The calculation of the electronic band structure shows that Z _ C 2 O N T s are an indirect band gap semiconductor, and A _ C 2 O N T is a direct band gap semiconductor. The band gap value of Z _ C 2 O N T s first increases and then stabilizes with the diameters of the nanotubes, and the band gap value of A _ C 2 O N T s decreases with the increase in the nanotubes and tends to the band gap value of the g _ C 2 O sheet. In addition, the electronic properties and thermoelectric properties of C 2 O N T s (n = 4 , 6 , 8) before and after N-doping were also studied. We found that N-doping changed the electronic and thermoelectric properties of C 2 O N T s . It reduced the nanotube band gap value and significantly improved the thermoelectric figures of merit of Z _ C 2 O N T s (n = 4 , 6 , 8) and A _ C 2 O N T (4 , 4) , which comprised an effective strategy to improve the thermoelectric figure of merit of nanotubes. The results showed that the C 2 O N T s had potential as thermoelectric materials after N-doping, which provided important guidance for designing low-dimensional g _ C 2 O nanostructures. [ABSTRACT FROM AUTHOR]

The potential application of two electrolyte additives, NiCl2‐DME and NiF2‐DME, in lithium–sulfur batteries is investigated by density functional theory calculations. The results show that both electrolyte additives can effectively adsorb soluble lithium polysulfide (LiPSs) in the electrolyte. With the progress of the charging–discharge reaction, NiCl2 and NiF2 separate from Li2Sn when it is converted to S8 and recombine with 1,2‐dimethoxy‐ethane (DME) to achieve the purpose of cyclic adsorption of polysulfide in the electrolyte. At the same time, NiF2 and NiCl2 also have a catalytic effect in the cycling process. When adsorbed with Li2Sn, the bond length of the Li–S bond in Li2Sn is elongated, which causes the reduction of the Li2Sn activation energy, making it easier to be oxidized, and accelerating the conversion speed of Li2Sn and reducing Li2S, Li2S2 deposition on the surface of the electrode. Therefore, NiCl2‐DME and NiF2‐DME are ideal dual‐function electrolyte additives. [ABSTRACT FROM AUTHOR]

Layered oxide materials are regarded to be the most promising high-performance cathode materials for sodium-ion batteries owing to their high working voltage and facile synthesis. Here, we study the influences of 3d transition metals on the cohesive energies, structural changes and operating voltages of P2-NaxMO2 during discharge based on first-principles calculations. Our results confirm that the performances of P2-NaxMO2 are associated with the chemical properties of the transition metals. In addition to this, we disclose that the involved orbitals of the 3d transition metal also greatly impact the electrochemical performance of the P2-NaxMO2 material during discharge according to the analysis of electronic structures. The jumps in the working voltage and volume during discharge are closely related to the occupation of the eg and t2g orbitals. Therefore, it is necessary to ensure that the discharge or charge process is carried out in one degenerate orbital to avoid jumps in the voltage and volume of the material. Our results could shed a light on the subsequent design of layered oxide cathodes with high cycle stability and a smooth voltage curve. [ABSTRACT FROM AUTHOR]

One of the biggest challenges of Li–S batteries (LSBs) is the dissolution of polysulfides at the cathode side. An ideal LSB cathode should be able to prevent polysulfide (Li2Sn, 1 ≤n≤ 8) dissolution, and should have a strong binding energy, high capacity and a light weight, as well as being electrically conductive. Herein, we present our quantum chemical calculations combined with a genetic algorithm for a global structure search using a C2N nanosheet as a LSB cathode. The Gibbs free energies of isolated Li2Sn and LimSn_C2N (1 ≤m, 1 ≤n≤ 8) are calculated to set forth the studies of both the voltages and stabilities of lithiation reactions in every step of the discharging process. Our results indicate that the polysulfides can adhere to the C2N host substrate in a thermodynamically stable cluster state without dissolution, and the system has an energy capacity of up to 1122.21 W h kg−1. The calculated band-structure shows that LimSn_C2N is metallic though the original C2N nanosheet has an optical gap of 1.96 eV. This shows that C2N could be a promising cathode material for LSBs. [ABSTRACT FROM AUTHOR]

Abstract: The fact that a magnetic hysteresis loop is observed only in polymerized C60 and is absent in both pristine and depolymerized C60 establishes a close link between the weak ferromagnetism and the underlying structure. Furthermore, the correlation between the weak ferromagnetism and hydrogen presence has been explored by 1HNMR and 1H–13C cross-polarization NMR, whereby strong bonding between the H adducts and C60 has been verified. The adducted hydrogens most likely form bonds with the carbon atoms of inter-C60 four-membered rings. This conclusion is further supported by the formation energy of adducted H and the exchange energy among adducted H obtained from first-principle calculations on Rh-C60. [Copyright &y& Elsevier]

In magnesium-sulfur batteries, electrolyte exploration is vital for developing high-energy-density, safe, and reliable batteries. This study focused on cyclic THF and chain DME, representative solvents in ether electrolytes. MgCl 2 , an ideal anionic salt, forms mono-nuclear (MgCl 2 (DME) 2 ), bi-nuclear ([Mg 2 (μ-Cl) 2 (DME) 4 ] 2+ ), and tri-nuclear ([Mg 3 (μ-Cl) 4 (DME) 5 ] 2+ ) complexes in DME. With increasing salt concentration, these complexes sequentially form. Under lower salt concentrations, THF and MgCl 2 form mono-nuclear complexes ([MgCl 2 (THF) 4 ]) and continue to form bi-nuclear complexes ([Mg 2 (μ-Cl) 3 (THF) 6 ] + ). However, at higher salt concentrations, bi-nuclear complexes ([Mg 2 (μ-Cl) 3 (THF) 6 ] + ) directly form in THF. Comparing HOMO-LUMO values, [Mg(DME) 3 ] 2+ is easily oxidized. Energy gaps decrease with Cl - ion addition, enhancing solution conductivity. Ratios of Mg 2+ and Cl - in S-reduction complexes differ, suggesting DME is better at a low Mg/Cl ratio, and THF at a high Mg/Cl ratio. This study contributes to understanding complexes and enhancing Mg-S battery performance., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Layered oxide materials are regarded to be the most promising high-performance cathode materials for sodium-ion batteries owing to their high working voltage and facile synthesis. Here, we study the influences of 3d transition metals on the cohesive energies, structural changes and operating voltages of P2-Na x MO 2 during discharge based on first-principles calculations. Our results confirm that the performances of P2-Na x MO 2 are associated with the chemical properties of the transition metals. In addition to this, we disclose that the involved orbitals of the 3d transition metal also greatly impact the electrochemical performance of the P2-Na x MO 2 material during discharge according to the analysis of electronic structures. The jumps in the working voltage and volume during discharge are closely related to the occupation of the e g and t 2g orbitals. Therefore, it is necessary to ensure that the discharge or charge process is carried out in one degenerate orbital to avoid jumps in the voltage and volume of the material. Our results could shed a light on the subsequent design of layered oxide cathodes with high cycle stability and a smooth voltage curve.