Aqueous aluminum ion batteries (AAIBs) possess the advantages of high safety, cost-effectiveness, eco-friendliness and high theoretical capacity. However, the Al2O3 film on the Al anode surface, a natural physical barrier to the plating of hydrated aluminum ions, is a key factor in the decomposition of the aqueous electrolyte and the severe hydrogen precipitation reaction. To circumvent the obnoxious Al anode, a proof-of-concept of an anode-free AAIB is first proposed, in which Al2TiO5, as a cathode pre-aluminum additive (Al source), can replenish Al loss by over cycling. The Al-Cu alloy layer, formed by plating Al on the Cu foil surface during the charge process, possesses a reversible electrochemical property and is paired with a polyaniline (cathode) to stimulate the battery to exhibit high initial discharge capacity (175 mAh g-1), high power density (≈410 Wh L-1) and ultra-long cycle life (4000 cycles) with the capacity retention of ≈60% after 1000 cycles. This work will act as a primer to ignite the enormous prospective researches on the anode-free aqueous Al ion batteries.
The composite or hybrid of organic and inorganic materials is one of the common ways to improve the properties of photoelectric functional materials. Perylene bisimide (PBI) derivatives, as large π-conjugated organic small molecules, are a class of photoelectric functional materials with excellent performance. However, there were few reports on PBIs in the electrochromic field due to the difficulty of film-forming caused by their generally poor solubility. Here, water-soluble PBI derivatives (PDI-COOH and PCl-COOH) were synthesized. The hybrid films (ZnO@PDI-COOH/PCl-COOH) formed by the coordination bond and π-π stacking were prepared via a simple solution immersion method. Fourier transform infrared spectrometry and X-ray diffraction as well as scanning electron microscopy, and energy-dispersive spectrometry results further confirmed the formation of hybrid films. At the same time, electrochemical and spectroelectrochemical analyses revealed that the films have reversible redox activity and cathodic electrochromic properties, which can change from orange-red to purple. The ZnO@PDI-COOH hybrid film formed by coordination bonds exhibits fast switching times (1.7 s colored time and 2.6 s bleached time), good stability (retain 92.41% contrast after 2400 cycles), a low driving voltage (-0.6-0 V), and a high coloration efficiency (276.14 cm2/C). The corresponding electrochromic devices also have good electrochromic properties. On this basis, a large-area (100 mm × 100 mm) electrochromic display device with fine patterning was fabricated by using the hybrid film, and the device shows excellent reversible electrochromic performance. This idea of constructing organic-inorganic hybrid materials with coordination bonds provides an effective, energy-saving, and green method, which is expected to promote the large-scale and fine production of electrochromic materials.
The metastable intermixed composite (MIC) is one of the most popular research topics in the field of energetic materials (EMs). The goal is to invent EMs with tunable reactivity and desired energy content. However, it is very difficult to tune the reactivity of MIC due to its high reactivity and sensitivity caused by enlarged specific surface area and intimate contact between the oxidizers and fuels. Herein, we demonstrated a facile fabrication method that can be used to control the reactivity between the nanoaluminum (n-Al) and poly(tetrafluoroethylene) (PTFE) using an in situ-synthesized polydopamine (PDA) binding layer. It was found that PDA can adhere to both n-Al and PTFE particles, resulting in integrated n-Al@PDA/PTFE MICs. In comparison with traditional n-Al/PTFE MICs, the n-Al@PDA/PTFE showed an increased energy release and reduced sensitivity and more importantly tunable reactivity. By regulating the experimental conditions of coating, the thickness of PDA could be well controlled, which makes the tunable reactivity of n-Al@PDA/PTFE possible. The PDA interfacial layer may increase the preignition reaction (PIR) heat of Al2O3/PTFE and therefore the overall reaction heat of n-Al/PTFE. It also reveals that the PDA interfacial layer postponed the PIR, leading to an increase in onset thermal decomposition temperature ( To). As To increased, a more complete reaction between PTFE and Al nanoparticles could be achieved.
