Negative thermal expansion (NTE) behavior is an interesting physical phenomenon, but the number of NTE materials is limited. In this study, a new NTE compound has been found, FeFe(CN)6 Prussian blue analogue, where the average linear coefficient of thermal expansion (αl) is −4.260 × 10−6 K−1 between 100 and 450 K. The NTE properties and local vibration dynamics have been investigated by joint experiments of synchrotron X-ray diffraction, X-ray pair distribution function, and extended X-ray absorption fine structure spectroscopy. It has been observed that the Fe–C/Fe–N bonds expand with increasing temperature, while the unit cell shrinks in FeFe(CN)6. The vibration directions of both Fe–C and Fe–N prefer to be perpendicular to the linkage of Fe–CN–Fe rather than being parallel. More pieces of evidence indicate that the transverse vibrations of N atoms dominate the NTE behavior of FeFe(CN)6. The present results prove directly that the transverse thermal vibrations of C and N atoms are crucial for the occurrence of the NTE of Prussian blue analogues.
The application needs of small electronic devices and large-scale power grid storage continuously promote the development of a new battery energy system. Rechargeable metal batteries based on aluminum (Al) are of enormous potential due to the abundant Al reserves, the trivalent charge carrier, high theoretical specific capacity (2980 mAh/g), and volumetric energy density (8046 mAh/cm 3 ). However, the passivating oxide layer on the surface of the Al anode blocks the migration of electrons and ions, resulting in the operation difficulty and irreversibility of aluminum-based batteries. Herein we treated Al anode with a deep eutectic solution (DES) and constructed stable solid interface interphase on its surface, which can effectively prevent surface passivation , improve the chemical properties of the interface, promote ion transfer, and enable aqueous Al batteries with superior electrochemical performance . The assembled symmetric cells with treat Al (TAl) can cycle for more than 300 h with a low overpotential (~0.2 V). The TAl anode coupling with the FPB cathode material to assemble the full cells based on the aqueous electrolyte system can deliver a high discharge capacity of 85 mAh/g and exhibit capacity retention of 58 mAh/g after 150 cycles and an average coulombic efficiency of 97.1% at a current density of 100 mA/g. This work provides a novel surface modification strategy of Al metal anode and demonstrates high stability and cost-effective aqueous Al metal battery system, which suggest the significance for the commercialization of Al-metal batteries and their applications in large-scale energy store.
危险品化学品经营许可证（带存储）