Theoretical Insights into Li-Ion Transport in LiTa₂PO₈

Recently, a solid electrolyte material LiTa2PO8 (LTPO) with a high room-temperature ionic conductivity (1.6 mS/cm) has been reported in experiment. To understand its Li transport mechanism and find its theoretical performance limit, we systematically investigate the properties of LTPO using density functional theory and ab initio molecular dynamic (AIMD) simulations. Our results show that LTPO is electrochemically stable with a wide electrochemical window. AIMD simulations indicate that Ta, P, and O are immobile during Li diffusion, indicating a high stability of the material. The Li-ion diffusion channels form a quasi-two-dimensional honeycomb framework. The intrinsic ionic conductivity of LTPO is predicted to be as high as 35.3 mS/cm at room temperature. The diffusion activation energy is only 0.16 eV, consisting of a low-energy barrier obtained from the minimum-energy path calculations. These results encourage further experimental studies on this promising solid-state electrolyte material

Theoretical Investigation on the Role of Na and O for High Conductivity in Na-Doped SrSiO₃

Generally, the conductivity of any electrolyte depends on the concentration of charge carriers and the activation energy of mobile species in the electrolyte. The detailed mechanism inducing high oxide ion conductivity in alkali-doped strontium silicate Sr3–3xNa3xSi3O9–1.5x (x = 0.45) (SNS) is still unclear and is under debate up to now. Questions are proposed about the charge carrier species of SNS. In this work, AIMD simulations are performed to investigate the Na and O dynamics and the effect of Na on the conductivity in Na-doped SrSiO3. Our AIMD simulations reveal that perfect SrSiO3 is an insulator, whereas SNS exhibits an excellent high oxide (O) ion conductivity (2.5 × 10–2 S/cm) with a low activation energy (0.37 eV). Na doping leads to amorphization of the structure and disrupts the bonding between O and the surrounding atoms, resulting in a greatly increased MSD. Moreover, trajectory study suggests that Na shows a random diffusion throughout the structure and collides not only with Sr but also with Si and O. The atomic collision behavior of Na may contribute to the excellent high oxide ion conductivity of SNS. This work highlights the central underline of Na’s role in oxide ion conductivity. However, such a random diffusion of Na may have important implications for its use as solid-state oxide fuel cells

Na₂FeS₂ Cathode for Sodium-Ion Batteries: A Theoretical Study

Sodium-ion batteries (SIBs) with high energy density, improved safety, and low cost are exciting candidates for next-generation energy storage and electrical vehicles. Cathode materials are the core component for SIBs. Recently, an experimental study reported a promising Na2FeS2 cathode with a specific structure consisting of edge-shared and chained FeS4 tetrahedra as the host structure and a high capacity of 320 mA h g–1 for sodium storage. However, the underlying reaction mechanisms and Na migration pathways have not been fully understood. In this study, density functional theory (DFT) and DFT + U calculations are performed to study the structural stability, phase stability, electronic properties (spin polarization density of states), average voltage using total energy based on fully charged and discharged states, and Na-ion transport and diffusion channel using ab initio molecular dynamic simulations of the NaXFeS2 (X = 2, 1.5, and 1) cathode materials. It is revealed that Na2FeS2 is unstable at 0 K and possesses a theoretical capacity of 323 mA h g–1 with a low diffusion barrier of 0.40 eV in NaxFeS2 series. Moreover, some transition metals are substituted at Fe sites to evaluate the structural effect of Na2FeS2, in which Na2MnS2 exhibits excellent structural stability, low hull energy, and high theoretical capacity of 325 mA h g–1, which could be appealing for researchers in the future

Larval and pupal weight (mean ±SE) of <i>P</i>. <i>gossypiella</i> on wheat germ, okra and chickpea diet.

The means followed by bar gram by same letters are not significantly different at p>0.05 by Tukey’s HSD test.</p

Fig 5 -

1: Neonate larva shifted on diet 2: Second instar larva feed on prepared diet 3: Third instar 4: Fully grown fourth instar ready to pre-pupate 5: Male and female dark brown pupae 6: Emerged pink bollworm adult.</p

Wheat germ meal artificial diet and its gradients used in this study.

Wheat germ meal artificial diet and its gradients used in this study.</p

Growth and development of <i>Pectinophora gossypiella</i> reared on various treatment diets.

Growth and development of Pectinophora gossypiella reared on various treatment diets.</p

Ingredients of chickpea medium along with their quantity.

Ingredients of chickpea medium along with their quantity.</p

Total life span (mean ±SE) of male and female <i>P</i>. <i>gossypiella</i> on wheat germ, okra and chickpea diet.

The means represent by bar gram by same letters are not significantly different at p>0.05 by Tukey’s HSD test.</p

Mean comparison of larval and pupal weights of pink bollworm reared on three treatment diets.

Mean comparison of larval and pupal weights of pink bollworm reared on three treatment diets.</p