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Context: La2Mo2O9 is a potential electrolyte material for SOFC due to its higher oxygen conduction at high temperatures. However, La2Mo2O9 suffers from detrimental phase transition at high temperature from monoclinic α to cubic β phase. This phase transition can be prevented by lowering the temperature. However, lowering the temperature reduces the ionic conductivity. Substitution of transition metal on Mo site is the best strategy for the suppression of phase transition. In the present work, the effect of substituting element on different sites has been investigated. From the result, it is observed that the band gap increases with concentration of Er. Method: For the assessment of mechanism behind the improved performance, the atomic insight is crucial. For that, we have employed ab initio DFT calculation. We have used PBE and grimme d3 dispersion correction for the accuracy of evaluated band gap and electrochemical stability. All DFT calculations have been performed using Quantum ESPRESSO pwscf code's and for the assessment of thermodynamical stability of La2Mo2O9 and the doped structures, an alternative descriptor, the global instability index (GII), which is based on the bond valance sum approach implemented in SoftBV was used. All the visualizations were done by XCrySDen and VESTA open source software. [ABSTRACT FROM AUTHOR]

The growing demand for high-capacity and energy-dense lithium-ion batteries has driven the increase of nickel content in commercially available cathodes. However, during deep charging (delithiation), these Ni-rich cathodes experience a detrimental phase transformation and a sudden, significant decrease in lattice volume. This lattice collapse is considered the primary culprit behind the limitations in the cathode's electrochemical performance. Notably, the exact cause-and-effect relationship between the phase change and the collapse remains unclear. In the present study, the effect of the site of substitution on the performance of the LiNiO 2 cathode has been investigated by adopting tungsten as a dopant. To gain deeper insights into this connection within Ni-rich LiNiO 2 , the contraction of the c-axis and the change in the a-axis during the delithiation have been investigated using ab initio density functional theory. Findings reveal that the free energy difference between the suspected phases in Ni-rich LiNiO2 is minimal at room temperature, facilitating the transition from the H2 to the H3 phase. This transition appears to be driven by the movement (gliding) of the NiO 2 layer towards the adjacent Li layer. The findings of the present study indicate that among two different configurations due to different sites of substitution, the WLNO-2 configuration suppresses H2 –H3 phase conversion to a greater extent by hindering the gliding of the NiO 2 layer toward the Li layer. Furthermore, a reduction in the collapse of the c-axis lattice during deep de-lithiation for the WLNO-2 configuration has been observed. This reduced collapse is primarily attributed to the altered charge distribution within oxygen atoms and the weakened screening effect from lithium ions. [Display omitted] • Lattice collapse at deep delithiation LiNiO 2 (LNO) cathode suffers from stability which compromises cathode performance and life span. • Several studies have been reported on the correlation between phase transition and lattice collapse, but a clear consensus is still not achieved. • 4 % of the tungsten atoms were substituted at two different sites of Ni in the LNO structure. • Location of the substitution plays a critical role in influencing both phase transition and lattice volume collapse. • Incorporating element substitution at the optimal site, we can pave the way for high-voltage, high-rate, and collapse-free cathodes. [ABSTRACT FROM AUTHOR]

In the present research article, the detailed insight of electronic, thermal, and vibrational properties for a molecular system of silicon dioxide (SiO2)–succinonitrile (SCN), i.e., SiO2/SCN has been investigated using both the theoretical and experimental approaches. Experimentally, SiO2/SCN has been synthesized via one-pot non-hydrolytic sol–gel process using plastic phase crystal, succinonitrile (SCN) and silicon dioxide i.e., SiO2 and further characterized using thermal and vibrational properties. Density functional theory (DFT) has been performed to explore the insights of electronic and vibrational properties and to elaborate the nature of electro-chemical interaction present within the current system, so that the factors responsible for the desired results can be understood easily in detail. The HOMO–LUMO studies of SiO2/SCN explore different global and local chemical descriptors like, electronegativity, chemical potential, chemical hardness, chemical softness, electrophilicity index and energy gap. Herein, our motive is to study the improved electronic, thermal, and vibrational properties of SiO2/SCN due to the interaction of SCN with silicon dioxide atoms at the molecular scale level and to explore their insights which have different applications as the scaffold of many electrolyte materials in secondary batteries, supercapacitors, and solar cells etc. [ABSTRACT FROM AUTHOR]

[Display omitted] • The structural and electronic property explains that the cation Li+ attraction towards ether oxygen of PEO based on Hard-Soft Acid Base Principle. • Reduction in crystalline nature of PEO is observed after addition of plasticiser PEG. • The reduce in the forbidden gap with the addition of PEG in polymer-metal complex justifies the increase in the ionic conductivity. Quantum chemistry-based codes and methods provide valuable computational tools to study the atomic and molecular structure of any system. This paper provides insights into the electronic and structural properties of polyethylene oxide (PEO) and polyethylene glycol (PEG) based solid polymer electrolyte incorporated with lithium iodide as ion-conducting species using first principle method. PEO shows insulator characteristics with a broad bandgap of 5.2 eV which decreased significantly to 3.19 eV in PEO-PEG-LiI. The wide forbidden energy band gap of PEO-PEG-LiI concludes that conductivity in polymer electrolytes is predominantly ionic rather than electronic. The presence of hydrogen bonding between PEG and PEO shows their amazing compatibility. Hirschfield population analysis (HPA) quantify the interactions involved within the structure and explains the interaction of Li-ion with ether group of PEO. Overlapping of wavefunctions of C, O and H atoms in polymers proves the existence of partial ionic and partial covalent bonding among them. [ABSTRACT FROM AUTHOR]

Context: La2Mo2O9 is a potential electrolyte material for SOFC due to its higher oxygen conduction at high temperatures. However, La2Mo2O9 suffers from detrimental phase transition at high temperature from monoclinic α to cubic β phase. This phase transition can be prevented by lowering the temperature. However, lowering the temperature reduces the ionic conductivity. Substitution of transition metal on Mo site is the best strategy for the suppression of phase transition. In the present work, the effect of substituting element on different sites has been investigated. From the result, it is observed that the band gap increases with concentration of Er. Method: For the assessment of mechanism behind the improved performance, the atomic insight is crucial. For that, we have employed ab initio DFT calculation. We have used PBE and grimme d3 dispersion correction for the accuracy of evaluated band gap and electrochemical stability. All DFT calculations have been performed using Quantum ESPRESSO pwscf code's and for the assessment of thermodynamical stability of La2Mo2O9 and the doped structures, an alternative descriptor, the global instability index (GII), which is based on the bond valance sum approach implemented in SoftBV was used. All the visualizations were done by XCrySDen and VESTA open source software. [ABSTRACT FROM AUTHOR]