Tunneling magnetoresistance (TMR) and spin filtering effects in the magnetic tunnel junctions (MTJs) have drawn much attention for potential spintronic applications based on magnetic manipulation of electric transport. However, the traditional MTJs cannot meet the demand for rapid miniaturization of electronic components. Thus, van der Waals (vdW) MTJs with a few atomic layers stacked vertically are ideal candidates for atomic scale devices. In this work, by employing the non-equilibrium Green's function combined with density-functional theory, we systemically study the spin-dependent electronic transport properties across MnBi2Te4 (MBT)-based vdW MTJs with three typical barrier layers, i.e., monolayer hexagonal boron nitride (h-BN), monolayer graphene, and vacuum. By using graphite as the electrode of these junctions, we find that a high TMR ratio up to 4000% and almost 100% spin filtering ratio are realized in MBT|h-BN|MBT MTJ at low bias voltages. Moreover, a remarkable negative differential resistance effect is observed in MBT|h-BN|MBT and MBT|Graphene|MBT junctions. The observed barrier-dependent quantum transport phenomenon is explained by the transmission coefficient. Our unique design of these vdW structures reasonably overcomes the bottleneck of current leakage and avoids the interface contact issues and paves the way for the exploration of spintronics devices with better performance.

Cathode coatings have received extensive attention due to their ability to delay electrochemical performance degradation in lithium-ion batteries. However, the development of cathode coatings possessing high ionic conductivity and good interfacial stability with cathode materials has proven to be a challenge. Here, we performed first-principles computational studies on the phase stability, thermodynamic stability, and ionic transport properties of LiMXO4F (M–X = Al–P and Mg–S) used as cathode coatings. We find that the candidate coatings are thermodynamically metastable and can be synthesized experimentally. The coating materials possess high oxidative stability, with the materials predicted to decompose above 4.2 V, suggesting that they have good electrochemical stability under a high-voltage cathode. In addition, the candidate coatings exhibit significant chemical stability when in contact with oxide cathodes. Finally, we have studied the Li-ion transport paths and migration barriers of LiMXO4F (M–X = Al–P and Mg–S) and calculated the low migration barriers to be 0.19 and 0.09 eV, respectively. Our findings indicate that LiMXO4F (M–X = Al–P and Mg–S) are promising cathode coatings, among which LiAlPO4F has been experimentally confirmed. The theoretical cathode coating computational methods presented here can be extended to the solid-state battery system.

Out-of-plane deformation in graphene is unavoidable during both synthesis and transfer procedures due to its special flexibility, which distorts the lattice and eventually imposes crucial effects on the physical features of graphene. Nowadays, however, little is known about this phenomenon, especially for zero-dimensional bulges formed in graphene. In this work, employing first-principles-based theoretical calculations, we systematically studied the bulge effect on the geometric, electronic, and transport properties of graphene. We demonstrate that the bulge's formation can introduce mechanical strains (lower than 2%) to the graphene's lattice, which leads to a significant charge redistribution throughout the structure. More interestingly, a visible energy band splitting was observed with the occurrence of zero-dimensional bulges in graphene, which can be attributed to the interlayer coupling that stems from the bulged structure. Additionally, it finds that the formed bulges in graphene increase the electron states near the Fermi level, which may account for the enhanced carrier concentration. However, the lowered carrier mobility and growing phonon scattering caused by the formed bulges diminish the transport of both electrons and heat in graphene. Finally, we indicate that bulges arising in graphene increase the possibility of intrinsic defect formation. Our work will evoke attention to the out-of-plane deformation in 2D materials and provide new light to tune their physical properties in the future.

Using the first-principles method, the formation energy of O-vacancy clusters of two Li-rich Mn-based ternary cathode materials of lithium ion battery with different nickel contents, Li_1.2Ni_0.32Co_0.04Mn_0.44O₂ (space group × and Li_1.167Ni_0.167Co_0.167Mn_0.5O₂(space group C2/m), are calculated. Results show that the formation energy of oxygen vacancy clusters of the material with less nickel content Li_1.167Ni_0.167Co_0.167Mn_0.5O₂ can be always higher than the material Li_1.2Ni_0.32Co_0.04Mn_0.44O₂ with higher nickel content. This indicates that oxygen vacancy clusters are more likely to form in cathode materials with higher nickel content. The formation energy of the oxygen vacancy clusters near the transition metal is always greater than that near the lithium ion, indicating that the removal of oxygen tends to occur near the Li ion. Lower temperature and higher partial pressure can increase the formation energy of oxygen vacancy clusters and therefore inhibit the formation of oxygen vacancy clusters. In addition, the formation energies of oxygen vacancy clusters after the substitution of transition metals in the materials by other transition metals (i.e., Ti and Mo) are also calculated. Results show that, in addition to the case of substitution of Ni by Ti near the double oxygen vacancies near the Li-ion in Li_1.2Ni_0.32Co_0.04Mn_0.44O₂, all the rest cases of substitution of the transition metals Ni or Mn by Ti or Mo always increase the formation energy of the O-vacancy clusters. Therefore, the doping should be able to inhibit the loss of oxygen and improve the structural stability of materials.

Li-rich antiperovskite materials are promising candidates as inorganic solid electrolytes (ISEs) for all-solid-state Li-ion batteries (ASSLIBs).