Mechanisms and properties of the electron transport at the V2O5 cathode of Li-ion batteries were studied by means of first-principles computations.

The effects of different exchanging ions including Ag, Cu, and Sn on enhancing the photocatalytic activity of KNbTeO6 are investigated by means of experiments and calculations.

The formation of solid-electrolyte interphase (SEI) layers which results from the decomposition of organic solvents in the electrolyte on the anode of sodium-ion batteries (SIBs) is crucial and must be addressed to make SIBs well positioned in commercialization because the SEI layer has profound effects on SIBs’ initial capacity loss, life cycle, and safety. SEI properties such as chemical reactivity, thermal reactivity, mechanical stability, and durability have an impact on the overall performance of the batteries. Carbon-based anode materials are commonly used in SIBs and usually contain many types of defects and oxygenated functional groups. To gain insight into the influence of oxygenated functional groups of carbon-based materials on solvent decomposition mechanisms on the carbon surface, we perform density functional theory (DFT) calculations to investigate the effect of an epoxy group on decomposition mechanisms of ethylene carbonate (EC), which is a common solvent used in SIBs. We find that the presence of the epoxy group on the graphene surface diminishes EC decomposition as evidenced by a significant increase of reaction energies and reaction barriers. The EC decomposition mechanism yielding CO3 and C2H4 is most kinetically favorable. A similar effect of the epoxy group is also exhibited when the Na concentration increases. However, the increase of Na concentration affects the reaction barriers of each elementary step differently. More possible mechanisms were found when the explicit solvent molecules in the first solvation shell of Na are included. The additional pathway that an epoxy group reacts with a solvent molecule is found to be the most energetically favorable one. Thus, the epoxy group could promote EC decomposition through these pathways.

The removal of contaminated HCl gas in the petrochemical plants is essential to prevent corrosion problems, catalysts poisoning, and downstream contamination. Alkali-treated activated carbon (AC) was proposed as an effective adsorbent for HCl removal. Understanding the underlying mechanism of HCl adsorption on modified AC is key to design promising strategies for removal of HCl and other chlorinated hydrocarbon gases in the H2 feedstock. Here, a combined experimental and computational approach was used to study the role of alkali treatment on the adsorption behavior of HCl on the AC surfaces. We find that an interplay between alkali ions and oxygen-containing functional groups on the AC surface plays a crucial role in stabilizing the adsorbed HCl. The origin of such stable adsorbed configurations can be attributed to the dissociative adsorption of HCl leading to a formation of low energy species such as water, OH– and Cl– anions. These anions are electrostatically stabilized by the alkali ions resulting in a strong adsorption of −3.61 eV and −3.69 eV for Na+ and K+, respectively. Close investigation on charge analysis reveals that the epoxy functional group facilitates adsorbent-surface charge transfer where O and Cl atoms gain more charges of 0.37 e and 0.58 e which is in good correlation with the improved adsorption strength. The calculated results are consistence with the experimental observations that the Langmuir adsorptivity has been enhanced upon alkali modification. The maximum adsorption capacity of AC has been improved approximately by 4 times from 78.9 to 188.9 mg/g upon treatment.

Sodium-ion batteries (SIBs) have received much attention as promising alternatives to Li-ion batteries as large scale and low-cost energy storage systems owing to close electrochemical similarity between lithium and sodium, and the natural abundance of sodium resources. However, many challenges must be overcome to make SIBs well-positioned in commercialization such as low cyclability, and low stability of the solid-electrolyte interphase (SEI) formation, results from the decomposition of organic solvents in the electrolyte on the anode of SIBs. The SEI has a profound effect on cycle life and performance of the batteries. Therefore, understanding the SEI compositions and its formation mechanisms is crucial for SIBs development. Carbon-based anode materials are commonly used as the anode for SIBs because of their appropriate electrochemical properties, an abundance of carbon and safety. The oxygen-containing groups often present in the carbon-based anode and they usually actively involved in chemical reactions. In this work, we performed density functional theory (DFT) calculations to elucidate the effect of oxygen containing group of epoxy on decomposition mechanisms at the initial stages of sodiation of ethylene carbonate (EC) molecule which is one of common electrolytes applied in ion-battery. The calculation results indicated that EC decompositions on pristine graphene were initiated by CE-OE bond cleavage which is rate-limiting step followed by Cc-OE bond cleavage in the second step producing CO2 and acetaldehyde as products (Figure 1). The presence of an epoxy group on graphene does not directly change the mechanisms, however, it significantly increased the activation barriers on all decomposition pathways compared to those on pristine graphene. The strong electrostatic interaction between negatively charged epoxy group and positively charged Na ion weakens interaction between EC and carbon surface. Also, the presence of an epoxy group facilitates carbon surface to be more positively charged and electron transfer to EC is less favorable than that on pristine graphene. Furthermore, we investigated the solvation effect on the mechanisms by increase the number of EC molecules to model a solvation shell. The results showed that the inclusion of the electrolyte environment reveals other possible decomposition mechanisms including proton transfer from EC molecule to epoxy group producing hydroxyl group on carbon surface prior to the EC ring-opening reaction step. This work suggests that the presence of oxygenated functional group on anode carbon surface and solvent environment can have significant effects on EC decomposition mechanisms both thermodynamic and kinetic aspects. Including the electrolyte solvation shell is crucial for electrolyte decomposition investigation using molecular modeling. Figure 1