Researchers Design Thermoelectric Modules Using Highly Efficient Liquid-Like Materials

Researchers at the Shanghai Institute of Ceramics of the Chinese Academy of Sciences and Northwestern University in the United States synthesized a novel Cu₂Se/Yb_0.3Co₄Sb₁₂ thermoelectric (TE) module with eight p-type Ni/Mo/Cu₂Se legs and eight n-type Ni/Ti/Yb_0.3Co₄Sb₁₂ legs, based on high-performance liquid-like materials.

Their approach outperforms the normal design of TE modules based on conventional TE materials, thereby leading to a high energy conversion efficiency of 9.1% and good service stability. The research has been reported in Joule.

The common design of TE modules based on conventional materials must achieve only high efficiency or high-power output by improving the geometry and interfaces of material legs. But liquid-like ions impose a new challenge. It is necessary for service stability to be introduced in the design of TE modules based on liquid-like materials.

While in use, the voltage across liquid-like materials (V_a) has a direct relationship with the ratio of the cross-sectional areas of the p-legs and n-legs (A_p/A_n). If the liquid-like material is p-type, the high A_p/A_n ratio will result in low V_a and hence better stability during operation.

As part of this study, the researchers designed two types of TE modules based on liquid-like materials. They selected Cu_1.97S and Cu₂Se for the p-type legs and Yb_0.3Co₄Sb₁₂-filled skutterudite for the n-type legs. The outcomes revealed that the Cu_1.97S/Yb_0.3Co₄Sb₁₂ TE module is unstable while at work, whereas the Cu₂Se/Yb_0.3Co₄Sb₁₂ TE module is relatively stable when A_p/A_n is >4.

Three-dimensional numerical analysis revealed that A_p/A_n should be in the range of 2–8 for high efficiency of energy conversion. Hence, the values of A_p/A_n between 4 and 8 are needed to simultaneously increase conversion efficiency and attain good stability.

The researchers achieved a maximum energy conversion efficiency of 9.1% for the Cu₂Se/Yb_0.3Co₄Sb₁₂ TE module, which is a record-high energy conversion efficiency among TE modules of high temperature. The long-term aging test verified the optimal stability of the module.

This approach can also be used to develop new TE modules based on other liquid-like materials, for example, Ag₉GaSe₆ and Zn₄Sb₃.

TE technology can be used to achieve direct conversion between electricity and heat. Thanks to the benefits of no moving parts, no noise, and high reliability, it has gained considerable attention as an alternative method for using energy very efficiently.