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This research article presents a comprehensive first-principles study on the piezoelectric properties of Wurtzite Aluminum Nitride (AlN) films under in-plane strain conditions. By calculating the piezoelectric tensor coefficients (e33, e31, and e15), we investigate the variation patterns of these constants with respect to in-plane strain. Our results indicate significant changes in the piezoelectric constants within the range of in-plane strain considered, exhibiting a linear trend despite opposite trends for e33 compared to e31 and e15. This study highlights the extreme sensitivity of AlN films' piezoelectric performance to in-plane strain, suggesting its potential as an effective means for tuning and optimizing the piezoelectric properties of AlN-based devices. [ABSTRACT FROM AUTHOR]

Silicon (Si) and Si-based compounds have been considered by many researchers as one of the anode materials for the next-generation lithium-ion batteries (LIBs) due to their extraordinarily large theoretical capacity, moderate operating voltage, and abundant resources. However, silicon's poor conductivity and significant volume changes during charge and discharge, compared to conventional carbon materials, severely restrict its widespread use in LIBs. In this study, a two-dimensional (2D) mesoporous Si nanosheet/carbon (pSi@C) composite is designed using cetrimonium bromide–disodium edetate dihydrate (CTAB–EDTA) as a template via a sol–gel method, magnesium thermal reduction method, and thermal decomposition method. The vertical diffusion distance of Li+ is significantly reduced by the 2D Si nanosheets. Additionally, the carbon coating on the Si surface provides a protective layer to limit the volume expansion of Si and form a stable solid electrolyte interface (SEI). This enhances the structural integrity and cycle stability of the pSi@C anode material during Li+ insertion and extraction. At a current density of 1 A g–1, the reversible capacity of the pSi@C composite after 150 cycles is 2236 mAh g–1, with a capacity retention rate of 71.5%. The electrode's capacity is 467.8 mAh g–1 after 500 cycles at a current density of 5 A g–1. Therefore, this unique template and technology can be used to design 2D anode composites with excellent properties, thereby providing an effective strategy for commercial application of LIBs. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2) is a promising anode material for lithium-ion batteries with the characteristics of highly stable structure and excellent safety, while the application is constrained by its inferior electrical conductivity and sluggish lithium-ion diffusion kinetics. Herein, H2Ti4O9 was prepared as a precursor, and it was wrapped with polyvinylpyrrolidone (PVP) as the nitrogen and carbon sources. Then, the N-doped carbon-filled TiO2 nanocrystals (N-TiO2/C), which had a unique dragon fruit structure with TiO2 nanocrystals acting as seeds and carbon acting as the flesh, were successfully prepared from PVP-coated H2Ti4O9 by one-step heat treatment. It is noteworthy that four modification methods, including carbon filling, nanosizing, nitrogen doping, and morphological designing, are all accomplished simultaneously during this process. The N-TiO2/C composite exhibits an outstanding stable capacity of 444.6 mAh g–1 after 600 cycles at 1 A g–1, and it possesses a reversible capacity of 146.7 mAh g–1 at 5 A g–1. The superior electrochemical capacity can be attributed to the distinctive dragon fruit structure along with nitrogen doping and carbon filling. The ingenious modification strategy can extend to the investigation on the other oxide anode materials. [ABSTRACT FROM AUTHOR]

Due to poor electrical conductivity and significant volume change during the lithiation/delithiation process, the application of silica anode materials for lithium-ion batteries is severely limited. Here, SiO2 nanotubes with a uniform and complete carbon layer were prepared employing ZnO nanorods as templates. The controllable wall thickness of SiO2 nanotubes is about 11 nm, and the thinner wall reduces the lithium-ion diffusion distance and boosts performance. The uniform and complete carbon layer leads to a perfect dispersity of SiO2 nanotubes, enhances the overall electrical conductivity, and also buffers the mechanical stresses caused by volume change, which helps to exhibit high specific capacity and a long cycle life. The nanotubular SiO2@C composite reveals a high discharge specific capacity of about 526.3 mAh g−1 at a current density of 1 A g−1 after 500 cycles without significant capacity fade. In addition, it demonstrates excellent rate performance, which can maintain above 420 mAh g−1 even at a current density of 5 A g−1. The strategy may be adopted to prepare other anode materials as well. [ABSTRACT FROM AUTHOR]

Ternary wurtzite In0.5Al0.5N films and coatings are promising candidates for microelectronic or optoelectronic devices due to their excellent physical and chemical properties. However, as a universal and non-negligible phenomenon, in-plane strain and its effects on the structure and properties of In0.5Al0.5N still need systematic research. In particular, the deformation mechanism of In0.5Al0.5N under biaxial strain is not clearly understood currently. To reveal the role of the internal relaxation effect in lattice deformation, the lattice variation, thermal stability, and the electronic properties of ternary wurtzite compound In0.5Al0.5N under different biaxial strains are systematically investigated, using first-principles calculations based on density functional theory. The results indicate that, compared with the classic elastic deformation mechanism with constrained atomic coordinates, atom relaxation results in a much smaller Poisson ratio. Moreover, the plastic relaxation In0.5Al0.5N phase, generated by free atom relaxation, exhibits higher thermal stability than the elastic relaxation phase, so it is the most likely phase in reality when biaxial strain is imposed. Meanwhile, the biaxial strain has a remarkable influence on the electronic structure of In0.5Al0.5N films, where a non-linear variety of energy band gaps can be seen between the valance band and conduction band. [ABSTRACT FROM AUTHOR]