Based on high-performance liquid-like materials, scientists from the Shanghai Institute of Ceramics of the Chinese Academy of Sciences and Northwestern University in US innovatively fabricated a Cu2Se/Yb0.3Co4Sb12 thermoelectric module with eight n-type Ni/Ti/Yb0.3Co4Sb12 legs and eight p-type Ni/Mo/Cu2Se legs.
Their strategy goes beyond the normal design of TE modules based on traditional TE materials, thus realizing a high energy conversion efficiency of 9.1% and excellent service stability. The study was published in Joule.
The usual design of thermoelectric modules based on traditional materials only needs to realize high efficiency or high-power output through optimizing the geometry and interfaces of material legs. However, liquid-like ions present a new challenge and service stability must be included in the design of thermoelectric modules based on liquid-like materials.
During service, the voltage across liquid-like materials (Va) is directly related to the ratio of the cross-sectional areas of the p- and n-legs (Ap/An). If the liquid-like material is p-type, the larger Ap/An will lead to a smaller Va and consequently better stability during service.
In this study, scientists developed two kinds of TE modules based on liquid-like materials. They chose Cu2Se and Cu1.97S for the p-type legs and selected Yb0.3Co4Sb12-filled skutterudite for the n-type legs. The results showed that the Cu1.97S/Yb0.3Co4Sb12 TE module is not stable during service, while the Cu2Se/Yb0.3Co4Sb12 TE module is quite stable when Ap/An is higher than four.
Three-dimensional numerical analysis showed that high energy conversion efficiency requires that Ap/An be between two and eight. Thus, Ap/An values between four and eight are required to simultaneously maximize conversion efficiency and achieve good stability.
The scientists realized a maximum energy conversion efficiency of 9.1% for the Cu2Se/Yb0.3Co4Sb12 thermoelectric module, a record-high energy conversion efficiency among high-temperature thermoelectric modules. The long-term aging test confirmed the good stability of the module.
This strategy can also be used to design new TE modules based on other liquid-like materials such as Ag9GaSe6 and Zn4Sb3.
Thermoelectric technology can realize direct conversion between heat and electricity. Due to the advantages of no noise, no moving parts, and high reliability, it has attracted great attention as an alternative way to very efficiently utilize energy.