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The all-solid-state batteries (ASSBs) are of particular interest because of their higher energy density and improved safety. However, the interfacial instability and resulting high interfacial resistance between the cathode and solid electrolyte (SE) have become the major challenges for the practical application of ASSBs. Herein, we report a stable LiFePO4 cathode/γ-Li3PO4 SE interface and systemically investigate the mechanism of Li-ion transport at the interface and the effects of surface nitrogen doping using first-principles calculations. It is found that delithiation at the LiFePO4/γ-Li3PO4 interface initially occurs at the topmost layer of the LiFePO4 cathode side, and hopping through the interface barrier is a rate-limiting step for Li mobility. Nitrogen doping leads to local structural distortion occurred at the interface, affecting the interfacial Li+ diffusion kinetics. Furthermore, the underlying mechanisms in which the different N doping sites alter the Li diffusion barrier are analyzed. We find that, by a rational design, N doping could significantly enhance Li+ diffusion kinetics. Further analysis of the electronic structure of the interface system reveals that the Li3PO4 electrolyte is electrochemically stable against the LiFePO4 cathode in the N-doped interface. Our findings provide a microscopic understanding of the Li+ transport at solid–solid LiFePO4/γ-Li3PO4 interface and suggest that controlling synthesis condition can be critical for enhancing Li+ transport at the N-doped LiFePO4/γ-Li3PO4 interface in an ASSB.

Two-dimensional black phosphorene (BP) has attracted much interest for application in electronic devices. Contacts between BP and metal electrodes are critical components of BP-based devices and can dramatically affect device performances. In this paper, we adopted first-principles calculations to explore binding energies, electronic structures, and potential distribution for interface systems of Al-, Au-, Cu-, Ni-, and Ti-monolayer BP in surface contact and edge contact (EC) types. Moreover, we also used density functional theoretical coupled with the nonequilibrium Green’s function method to investigate contact resistances and Schottky barrier heights (SBHs) for transport systems of monolayer BP with Al, Au, Cu, Ni, and Ti electrodes. Our calculated results indicate that the contact type between BP and metals may greatly affect electrical properties of BP–metal contacts. Changing contact type between metal electrodes and BP channel can change the type of Schottky barrier of metal–BP contacts. The contact barrier of metal–BP depends on the metal material. Selecting an appropriate contact type and metal can effectively regulate the contact barrier of metal–BP. Specifically exciting, our estimated lateral SBHs for the Ni–BP system in EC-type agree well with the experimental results. We have provided a new strategy on choosing an appropriate contact type to achieve low contact resistance for the metal–BP interface.

High-temperature ferromagnetism has always been a classic and interesting subject, especially in spin gapless semiconductor PbPdO 2 with exotic properties. Here, a combination of theoretical and experimental studies was employed to clarify the origin of high Tc. First, based on first-principles calculations, electronic band structures of PbPd 0.875Co 0.125O 2 at different Co substitution positions were studied. Our results indicate that Co atoms tend to form an antiferromagnetic ground state due to the Co–O–Co (180 °) indirect exchange effect, while ferromagnetism is favored in Co-doped PbPdO 2 when a unique molecular field effect induced band crossover and p– d coupling occurs. It is revealed that metallic or semiconductor properties have an important connection with ferromagnetism or antiferromagnetism. Subsequently, a Monte Carlo simulation was carried out based on the first-principles results to predict the ferromagnetism of PbPd 0.875Co 0.125O 2. Finally, the moment-magnetic field and moment-temperature curves were also measured for PbPd 0.875Co 0.125O 2 samples, which was found well consistent with the theoretical findings. The ground state of PbPd 0.875Co 0.125O 2 was confirmed to be ferromagnetic. Our results well explain the origin of high-temperature ferromagnetism in diluted magnetic semiconductors and provide new approaches for the design of future high Tc spintronic devices.

We study the magnetoelectric property and optical absorption for the short-period [001]-oriented (LaMnO3)2/BaTiO3/(SrMnO3)2 superlattices using the first-principle method. By performing the spin-orbit coupling calculations with more effective Perdew-Burke-Ernzerhof functional modified for solid potentials, we demonstrate the electrically controlled spin-flip at the interface. Furthermore, the infrared absorption of the superlattices is significantly improved, depending on the electric polarization of the BaTiO3 layer. The results provide a potential design for pursuing the ferroelectric field effect control of magnetism and optical response.We study the magnetoelectric property and optical absorption for the short-period [001]-oriented (LaMnO3)2/BaTiO3/(SrMnO3)2 superlattices using the first-principle method. By performing the spin-orbit coupling calculations with more effective Perdew-Burke-Ernzerhof functional modified for solid potentials, we demonstrate the electrically controlled spin-flip at the interface. Furthermore, the infrared absorption of the superlattices is significantly improved, depending on the electric polarization of the BaTiO3 layer. The results provide a potential design for pursuing the ferroelectric field effect control of magnetism and optical response.

The effective work functions for Ni/HfO2 interfaces under two strain modes (uniaxial and triaxial strains) were studied by using first-principles methods based on density functional theory. The calculated results indicate that the effective work functions are strongly affected by the type of interface and the strain states (tensile and compressive strains). For the both above strain states, the changed value of the effective work functions linearly increases with increasing strain. Moreover, it is observed that for a certain strain, the variation of the effective work function for triaxial strain state is almost larger than that for uniaxial strain state. Finally, the electrons gas model, the interface dipole, and screening role of HfO2 were used to analyze and explain the strain and interface effects in metal-oxide interfaces. The evident difference between the effective work functions of Ni-Hf and Ni-O interfaces is found to be attributed to different metallic bondings and ionic bondings via the analysis of the charge density distributions. Our work strongly suggests that controlling the strain and interface structure is a promising way for modulating the work function of Ni/HfO2 interfaces.

We present a first-principles calculation for the electronic and Li-ion diffusion properties of the LiFePO4 (010) surface modified by sulfur. The calculated formation energy indicates that the sulfur adsorption on the (010) surface of the LiFePO4 is energetically favored. Sulfur is found to form Fe-S bond with iron. A much narrower band gap (0.67 eV) of the sulfur surface-modified LiFePO4 [S-LiFePO4 (010)] is obtained, indicating the better electronic conductive properties. By the nudged elastic band method, our calculations show that the activation energy of Li ions diffusion along the one-dimensional channel on the surface can be effectively reduced by sulfur surface modification. In addition, the surface diffusion coefficient of S-LiFePO4 (010) is estimated to be about 10−11 (cm2/s) at room temperature, which implies that sulfur modification will give rise to a higher Li ion carrier mobility and enhanced electrochemical performance.

First-principles calculations are performed to study the structural, electronic, and magnetic properties of pure and C-doped GaN nanoribbon with both zigzag edge (ZGaNNR) and armchair edge (AGaNNR). With increasing ribbon width, both the indirect bandgap of ZGaNNR and the direct bandgap of AGaNNR decrease monotonically and become closer to each other approaching their asymptotic limit of a single layer of GaN sheet. One C atom substituting for one N atom causes a slight local expansion, while one C atom substituting for one Ga atom results in a large local contraction. Furthermore, the C atom is preferred to substitute for an edge N or Ga atom in either 6-ZGaNNR or 6-AGaNNR, especially edge Ga atoms in 6-AGaNNR. There exists about 0.65 µB magnetic moment, which arises mainly from doped C atom while a single N atom is substituted by one C atom in either 6-ZGaNNR or 6-AGaNNR, which may open a way to design magnetic nanodevices based on GaNNR.