Stress effect on lattice thermal conductivity of anode material NiNb ₂O ₆ for lithium-ion batteries

The thermal transport properties of NiNb ₂O 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 ₂O 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 ₂O ₆. This anisotropy of the lattice thermal conductivity stems from the significant difference of phonon group velocities in different crystal directions of NiNb ₂O 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 ₂O ₆ can be enhanced by the compressive strain, and reduced by the tensile strain.