Achieving High Safety for Lithium-Ion Batteries by Optimizing Electron and Phonon Transport

For lithium-ion batteries, frequent safety issues remain a huge challenge for safe applications. Herein, we focus on the coupled effect of electronic transport and phonon scattering on the thermal safety of Li[NixCoyMnz]O-2 cathode materials. It is revealed that the electric conductivity of Li[NixCoyMnz]O-2 doubles to 33 S/m as Ni content increases from 1/3 to 0.8. However, the closure in the band gap leads to a strong compensation of phonon scattering due to the thermal motion of lattice atoms. The collision between electrons and phonons damages the periodicity of the potential field, leading to a much stronger phonon scattering and ultimately a 22% decrease in thermal conductivity. We demonstrate that an improvement in electronic conduction can result in a stronger lattice vibration that deteriorates the thermal safety of the battery. Understanding the electronic/thermal transport mechanism provides new guidance for solving the basic issue of heat generation, which is critical for designing Li-ion batteries with high safety.