Magnesium–lithium (Mg–Li) alloys are characteristic of great potentials for transformative weight reduction across diverse applications, from aeronautics and spacecraft to automobiles, electronics, and biomaterials. However, commercial services on Mg–Li alloys remain challenges given their poor corrosion resistance. This article critically reviews state-of-the-art progress of corrosion-resistant coatings for Mg–Li alloys, aiming to unlocking the full potential of such promising materials. The preparation techniques employed are summarized, the underlying protective mechanisms are elucidated, and coating performances are critically evaluated. This review further highlights key challenges for future exploration and development, and provides insightful perspectives towards emerging frontiers in this dynamic domain.

The high lattice thermal conductivity of half-Heuslers (HHs) restricts the further enhancement of their thermoelectric figure-of-merit (ZT). In this study, multiscale scattering centers, such as point defects, dislocations, and nanoprecipitates, are synchronously introduced in a n-type ZrNiSn-based HH matrix through Nb doping and Hf substitution. The lattice thermal conductivity is substantially decreased from 4.55 (for the pristine ZrNiSn) to 1.8 W·m⁻¹·K⁻¹ at 1123 K via phonon scattering over a broad wavelength range through the adjustment of multiscale defects. This value is close to the theoretically estimated lowest thermal conductivity. The power factor (PF) is enhanced from 3.25 (for the pristine ZrNiSn) to 5.01 mW·m⁻¹·K⁻² for Zr_0.66Hf_0.30Nb_0.04NiSn at 1123 K owing to the donor doping and band regulation via Nb doping and Hf substitution. This can be ascribed to the synergistic interaction between the lowering of the lattice thermal conductivity and retention of the high PF. Consequently, a ZT value of as high as 1.06 is achieved for Zr_0.66Hf_0.30Nb_0.04NiSn at 1123 K. This work demonstrates that these actions are effective in jointly manipulating the transport of electrons and phonons, thereby improving the thermoelectric performance through defect engineering.

The thermoelectric (TE) performance of p-type ZrCoSb-based half-Heusler (HH) alloys has been improved tremendously in recent years; however, it remains challenging to find suitable n-type ZrCoSb-based HH alloys due to their high lattice thermal conductivity (κ_L). In this work, n-type Zr_1-xTa_xCo_1-xNi_xSb HH alloys were firstly designed by multisite alloying. The evolution of the Raman peak proved that alloy scattering, phonon softening, anharmonicity, entropy-driven disorder, and precipitates had a combined effect on decreasing κ_L by 46.7% compared to that of pristine ZrCoSb. Subsequently, Hf_0.75Zr_0.25NiSn_0.99Sb_0.01 was introduced into Zr_0.88Ta_0.12Co_0.88Ni_0.12Sb to further suppress κ_L. Remarkably, the grain size of the biphasic HH alloys was refined by at least one order of magnitude. A biphasic high-entropy HH alloy with y = 0.2 exhibited the minimum κ_L of ~2.44 W/(m·K) at 923 K, reducing by 67.7% compared to that of ZrCoSb. Consequently, (Zr_0.88Ta_0.12Co_0.88Ni_0.12Sb)_0.9(Hf_0.75Zr_0.25NiSn_0.99Sb_0.01)_0.1 exhibited the highest TE figure of merit (~0.38) at 923 K. The cooperation between the entropy and biphasic microstructure resulted in multiscale defects, refined grains, and biphasic interfaces, which maximized the scattering of the multiwavelength phonons in HH alloys. This work provides a new strategy for further reducing the grain size and κ_L of medium- and high-entropy HH alloys.

Flexible thermoelectric materials are presented with potential applications in electronic devices and energy conversion due to their convenient preparation, good flexibility, and various forms. However, as ductility is rarely observed in inorganic semiconductors and ceramic insulators, reports on applications of inorganic oxide materials in flexible thermoelectric materials are sparse. Here, we report a new method for the synthesis of a flexible Na_1.4Co₂O₄ thermoelectric material based on Na_1.4Co₂O₄ bulk materials, which are prepared by a self-flux method and painted on print paper. Seebeck coefficient and power factor of the obtained thermoelectric material are 78–102 μVK^-1 and 159–223 μWm⁻¹K⁻², respectively, in a temperature range of 303–522 K, which are superior to those values of other conductive polymers and their compounds. More interestingly, the n-type Na_1.4Co₂O₄ flexible material is obtained in the painting process at higher pressure with Seebeck coefficients of −109 to −183 μVK⁻¹ in a temperature range of 303–522 K. The convenient preparation method of these novel flexible thermoelectric materials may be expanded to the synthesis of other flexible thermoelectric materials, which will be the focus of future work.