Stress effect on lattice thermal conductivity of anode material NiNB_(2)O_(6)for lithium-ion batteries

The thermal transport properties of NiNB_(2)O_(6)as anode material for lithium-ion battery and the effect of strain were studied by machine learning interatomic potential combined with Boltzmann transport equation.The results show that the lattice thermal conductivity of NiNB_(2)O_(6)along the three crystal directions[100],[010],and[001]are 0.947 W·m^(-1)·K^(-1),0.727 W·m^(-1)·K^(-1),and 0.465 W·m^(-1)·K^(-1),respectively,indicating the anisotropy of the lattice thermal conductivity of NiNB_(2)O_(6).This anisotropy of the lattice thermal conductivity stems from the significant difference of phonon group velocities in different crystal directions of NiNB_(2)O_(6).When the tensile strain is applied along the[001]crystal direction,the lattice thermal conductivity in all three directions decreases.However,when the compressive strain is applied,the lattice thermal conductivity in the[100]and[010]crystal directions is increased,while the lattice thermal conductivity in the[001]crystal direction is abnormally reduced due to the significant inhibition of compressive strain on the group velocity.These indicate that the anisotropy of thermal conductivity of NiNB_(2)O_(6)can be enhanced by the compressive strain,and reduced by the tensile strain.

Simulations of monolayer SiC transistors with metallic 1T-phase MoS_(2) contact for high performance application

We preform a first-principles study of performance of 5 nm double-gated(DG)Schottky-barrier field effect transistors(SBFETs)based on two-dimensional SiC with monolayer or bilayer metallic 1T-phase MoS_(2) contacts.Because of the wide bandgap of SiC,the corresponding DG SBFETs can weaken the short channel effect.The calculated transfer characteristics also meet the standard of the high performance transistor summarized by international technology road-map for semiconductors.Moreover,the bilayer metallic 1T-phase MoS_(2) contacts in three stacking structures all can further raise the ON-state currents of DG SiC SBFETs in varying degrees.The above results are helpful and instructive for design of short channel transistors in the future.

Enhanced thermoelectric properties in two-dimensional monolayer Si2BN by adsorbing halogen atoms

Using the first principles calculation and Boltzmann transport theory, we study the thermoelectric properties of Si2BNadsorbing halogen atoms (Si2BN-4X, X = F, Cl, Br, and I). The results show that the adsorption of halogen atoms cansignificantly regulate the energy band structure and lattice thermal conductivity of Si2BN. Among them, Si2BN-4I has thebest thermoelectric performance, the figure of merit can reach 0.50 K at 300 K, which is about 16 times greater than that ofSi2BN. This is because the adsorption of iodine atoms not only significantly increases the Seebeck coefficient due to banddegeneracy, but also rapidly reduces the phonon thermal conductivity by enhancing phonon scattering. Our work proves theapplication potential of Si2BN-based crystals in the field of thermoelectricity and the effective method for metal crystals toopen bandgaps by adsorbing halogens.

Thermal transport in lithium-ion battery: A micro perspective for thermal management

In recent years, lithium ion (Li-ion) batteries have served as significant power sources in portable electronic devices and electric vehicles because of their high energy density and rate capability. There are growing concerns towards the safety of Li-ion batteries, in which thermal conductivities of anodes, cathodes, electrolytes and separator play key roles for determining the thermal energy transport in Li-ion battery. In this review, we summarize the state-of-the-art studies on the thermal conductivities of commonly used anodes, cathodes, electrolytes and separator in Li-ion batteries, including both theoretical and experimental reports. First, the thermal conductivities of anodes and cathodes are discussed, and the effects of delithiation degree and temperature of materials are also discussed. Then, we review the thermal conductivities of commonly used electrolytes, especially on solid electrolytes. Finally, the basic concept of interfacial thermal conductance and simulation methods are presented, as well as the interfacial thermal conductance between separator and cathodes. This perspective review would provide atomic perspective knowledge to understand thermal transport in Li-ion battery, which will be beneficial to the thermal management and temperature control in electrochemical energy storage devices.