Next-generation rechargeable batteries are promising candidates for state-of-the-art lithium-ion batteries owing to their high energy density and preferred cost efficiency. For instance, Lithium-sulfur batteries, which are featured by their theoretically 10 times higher capacity and 5 times higher energy density, are reviving in both the academic and the industry. Shu Lei Chou and colleagues from the Institute for Superconducting and electronic materials, University of Wollongong, presented a review article and proposed a new concept of 4S (stable, safe, smart, sustainable) batteries. They reviewed the latest development of functional membrane separators in liquid-electrolyte next-generation batteries and based on which they reported the four important criteria for guiding the advancement of novel battery systems. This work, entitled "Functional membrane separators for next-generation high-energy rechargeable batteries", was recently published in National Science Review.
Compared to conventional lithium-ion batteries capable of thousands of cycles, next-generation batteries are plagued by the poor cycling behavior, which is normally caused by the active material loss and the electrode degradation. Functional membrane separators provide an effective approach to extend the cycling stability of several important battery systems. As can be seen from Figure 2, this work breaks the boundaries of five types of next-generation batteries, i.e., Li-S, room-temperature Na-, Li-organic, organic-based redox-flow and Li-air batteries. Ion-selective materials are applied as the separator to retard the unwanted shuttling of some specific species, e.g., polysulfide diffusion in Li-S batteries. The applied functional membrane materials are Nafion (protonated, lithiated or sodiated), polymer of intrinsic microporosity (PIM), polyurethane (PU), metal organic frameworks (MOF), graphene oxide and lithium superionic conductor (LISICON). All these materials, whether polymers or inorganics, possess characteristic pore structures for the transport of the component ions but reject others, therefore prevent the side reactions and greatly enhance the cycling stability.
The safety performance of batteries closely relates to the life and property security of customers, hence is also a key criterion for battery development. Separators with important properties of high thermal/dimensional stability, good wetting performance and excellent thermal conductivity help improve the battery safety. With regard to the notorious lithium dendrite problem, separator approaches that create homogeneous environment for lithium deposition enhance the battery safety. Besides, this article reviews the latest works of smart and sustainable separators. For instance, a voltage-responsive smart membrane system was constructed using a doped polypyrrole. When the applied electric field is zero, the membrane allows no ionic current. Otherwise, when a certain reducing electric field is applied, the transport of positive ions is facilitated because the polymer is negatively charged and provides hopping pathways for cations, the pore size expanded and the polymer turns from hydrophobic to hydrophilic. In addition, renewable polymers like cellulose are studied as promising candidates for fossil-based polyolefin materials to enable sustainable separators. The paper concludes that functional separators need further investigation and are expected to play a key role in advancing next-generation batteries towards the goal of 4S: stable, safe, smart, and sustainable.
About Institute for Superconducting and electronic materials, University of Wollongong
The ISEM was established in 1994 and is a world-class collaborative team conducting research in superconducting and electronic materials science and technology. This flagship research institute has grown to more than 160 researchers and postgraduate students led by Professor Shi Xue Dou, a Fellow of the Australian Academy of Technological Science and Engineering. ISEM researchers are recognized as world leaders in superconductors, electronic and energy materials. The ISEM has developed a dynamic, innovative research environment in its research programs including batteries for electric vehicles and energy storage; applied superconductivity for electrical and medical devices; energy conversion and transmission; spintronic and electronic materials for applications; terahertz science; and nano structured materials. ISEM seeks to stimulate the technological and commercial development to advance technologies. The Institute is located at the Australian Institute for Innovative Materials (AIIM), at the University of Wollongong's Innovation Campus, Australia's first multifunctional materials facility that has the capacity to develop the processes and devices needed to scale-up lab-based breakthroughs in preparation for commercialization. Visit isem.uow.edu.au to learn more.
This research received funding from Australian Research Council.
See the article:
Yuede Pan, Shulei Chou, Hua Kun Liu, and Shi Xue Dou
Functional membrane separators for next-generation high-energy rechargeable batteries
Natl Sci Rev nwx037 (2017)
The National Science Review is the first comprehensive scholarly journal released in English in China that is aimed at linking the country's rapidly advancing community of scientists with the global frontiers of science and technology. The journal also aims to shine a worldwide spotlight on scientific research advances across China.