Solid-State Electrochemical Thermal Switches with Large Thermal Conductivity Switching Widths.

Area of Science:

• Materials Science
• Solid-State Physics
• Electrochemistry

Background:

• Electrochemical thermal switches utilize transition metal oxides (TMOs) for tunable thermal conductivity.
• Current TMO-based switches exhibit limited switching width (<4 W m⁻¹ K⁻¹).

Purpose of the Study:

• To develop a solid-state electrochemical thermal switch with an enhanced thermal conductivity switching width.
• To investigate the thermal switching mechanism in LaNiOₓ-based materials.

Main Methods:

• Fabrication of LaNiOₓ-based solid-state electrochemical thermal switches.
• Electrochemical redox treatment to modulate the crystal structure and oxygen stoichiometry.
• Measurement of thermal conductivity (κ) in 'on' (oxidized) and 'off' (reduced) states.

Main Results:

• Achieved a thermal conductivity switching width of 4.3 W m⁻¹ K⁻¹.
• Fully oxidized LaNiO₃ (on state) showed κ = 6.0 W m⁻¹ K⁻¹, dominated by electron thermal conductivity (κ_ele = 3.1 W m⁻¹ K⁻¹).
• Reduced LaNiO₂.₇₂ (off state) exhibited κ = 1.7 W m⁻¹ K⁻¹, attributed to phonon scattering by oxygen vacancies.
• Demonstrated cyclability of thermal conductivity and crystalline lattice of LaNiOₓ.

Conclusions:

• LaNiOₓ-based electrochemical thermal switches offer a substantial improvement in switching width.
• The tunable thermal conductivity is linked to redox-induced changes in crystal structure and oxygen vacancies.
• These switches represent a promising platform for next-generation thermal management devices, including thermal displays.