Shulou(Shulou.com)11/24 Report--

CTOnews.com, April 27 (Xinhua) after years of research, researchers at the University of Science and Technology of China have designed a new type of ion conduction membrane to achieve approximately friction-free ion conduction in the microporous frame ion membrane. This kind of ionic membrane is expected to be widely used in energy conversion, large-scale energy storage, distributed power generation and other fields.

It is reported that the research results were published in the international academic journal Nature on April 26, Beijing time.

For many years, efficient storage and utilization of solar energy, wind energy and other new energy is an important research and development topic for Chinese researchers. CCTV pointed out that the advent of this kind of domestic ion-exchange membrane will break the technological monopoly of similar products abroad for many years.

Ionic membrane is a key component of related processes, such as hydrolytic tank, fuel cell, redox flow cell and ion capture electrodialysis. The team of Professor Xu Tongwen / Yang Zhengjin of the University of Science and Technology of China and their collaborators proposed a new type of triazine (CTOnews.com remarks: Q í n) frame polymer ionic membranes in view of the "conductivity-selectivity" relationship of ionic membranes.

Based on the limited domain effect of the rigid channel and the "ion coordination" mechanism in the channel, this kind of membrane material shows near-frictionless ion transfer and realizes the fast charge of the organic liquid flow battery in the water system. the charge and discharge current density of the battery reaches 500 mA / cm2, which is more than 5 times of the commonly reported value.

▲ figure 1. Design idea and preparation of triazine frame polymer ionic membrane after long-term research accumulation and a large number of experimental explorations, a new type of "microporous frame polymer ionic membrane" was designed. The "ion coordination" mechanism in the rigid microporous channel (figure 1D) is proposed to realize the approximately frictionless ion conduction in the membrane and the fast charging of water system organic flow battery. Key innovations include:

1. A series of self-supporting microporous frame ionic membranes with hydrophobic frame and hydrophilic functional side chain were prepared by one-pot method (Fig. 1). The results show that the main structure of the hydrophobic frame is stable after water absorption, and the adverse effects of ion membrane water absorption on ion channel size and macroscopic mechanical strength are avoided, and a rigid micropore limited environment is provided for ion transfer. The results show that the membrane has excellent anti-aging and swelling resistance (figure 2a-2d), the water absorption swelling ratio of the membrane is only 3.1% (figure 2d), and efficient ion transfer can be achieved under low water absorption (figure 2e).

two。 The mechanism of "ion coordination" in rigid microporous channels is proposed. The research team introduced charged groups and a variety of functional groups that can weakly interact with ions in the microporous frame ion membrane to reduce the ion transfer barrier by means of electrostatic interaction and ion-dipole interaction (Fig. 3a). Solid-state NMR and PFG-NMR tests (figure 3b-3f) show that the self-diffusion coefficient of Na + in the film is 1.18 × 10-5cm2 / s, which is close to the diffusion coefficient of Na + in aqueous solution (1.28 × 10-5cm2 / s) and infinite dilution Na + (1.33 × 10-5cm2 / s).

3. The surface resistance of the water system organic flow battery (anthraquinone / potassium ferricyanide system, Fig. 4a) assembled with microporous frame ionic membrane as separator is only 0.17 Ω cm2 (Fig. 4B). The battery has excellent rate performance (Fig. 4C), its charge-discharge current density can be as high as 500mA cm-2 (≤ 100mA cm-2 is generally reported in the literature), and it remains stable during cyclic charge and discharge under high current density (Fig. 4D). The membrane realizes the fast charge of the water system organic liquid flow battery, and the energy efficiency and capacity utilization efficiency of the battery at different current densities are significantly higher than those reported in the literature (Fig. 4emem4f). The researchers also expanded the research results and realized the fast charge of the neutral system liquid flow battery.

▲ figure 2. Excellent dimensional stability and ionic conductivity of triazine-framed polymer ionic membranes

▲ figure 3. Triazine frame polymer ion membrane realizes approximately frictionless ion transfer and ion conduction mechanism.

▲ figure 4. Fast charge of organic flow battery in water system by triazine frame polymer ionic membrane

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