Based on high-performance liquid-like materials, the Cu₂Se/Yb_0.3Co₄Sb₁₂ thermoelectric module including eight n-type Ni/Ti/Yb_0.3Co₄Sb₁₂ legs and eight p-type Ni/Mo/Cu₂Se legs is innovatively fabricated. A high energy conversion efficiency up to 9.1% and excellent service stability are reported in Joule. Such strategy goes beyond the normal design of TE modules based on the traditional TE materials, under the joint cooperation between the scientists from the Shanghai Institute of Ceramics, Chinese Academy of Sciences and the Northwestern University of US.

 Thermoelectric technology can realize direct conversion between heat and electricity. Due to the advantages of no noisy, no moving part, and high reliability, it has attracted great attentions as an alternative way to high-efficiently utilize energy.

The usual design of thermoelectric module based on traditional materials only needs to realize high efficiency or high-power output through optimizing material leg’s geometry and interfaces. However, the liquid-like ions presents a new challenge. Beyond the high energy conversion efficiency or high-power output, the service stability must be included in the design of thermoelectric module based on liquid-like materials.

During the service, the voltage across liquid-like materials (V_a) is directly related with the ratio of cross-sectional areas of p- and n-legs (A_p/A_n). If the liquid-like material is p-type, the larger A_p/A_n will lead to the smaller V_a and consequently better stability during service.

Two kinds of TE modules based on liquid-like materials are developed. Cu₂Se and Cu_1.97S are chosen as the p-type legs, and Yb_0.3Co₄Sb₁₂ filled skutterudite was selected as the n-type legs. The Cu_1.97S/Yb_0.3Co₄Sb₁₂ TE module is not stable during service. However, the Cu₂Se/Yb_0.3Co₄Sb₁₂ TE module is quite stable when the A_p/A_n is higher than 4. The three-dimensional numerical analysis shows that the high energy conversion efficiency requires the A_p/A_n between 2 and 8. Thus, the A_p/A_n values of 4-8 are required to simultaneously maximize conversion efficiency and achieve good stability.

A maximum energy conversion efficiency for the Cu₂Se/Yb_0.3Co₄Sb₁₂ thermoelectric module reaches 9.1%, a record-high energy conversion efficiency among the high temperature thermoelectric modules. The long-term aging test confirmed the good stability of the module. This strategy can be also used to design new TE module based on other liquid-like materials such as Ag₉GaSe₆ and Zn₄Sb₃.

Figure 1. a, Schematic drawing of a Cu₂Se/Yb_0.3Co₄Sb₁₂ TE couple used in the module. b, Temperature dependence of TE figure of merit (zT) for several typical liquid-like TE materials. c, Optical image of the eight-couple Cu₂Se/Yb_0.3Co₄Sb₁₂ TE module. d, Maximum TE conversion efficiency (η_max) as a function of temperature gradient (△T) for the Cu₂Se/Yb_0.3Co₄Sb₁₂ module.

Reference:

Contact:

Prof. SHI Xun, Prof. CHEN Lidong

Shanghai Institute of Ceramics

xshi@mail.sic.ac.cn