(301f) Applications of Advanced Fibers for Next-Generation Lithium Batteries: From Liquid to Solid-State Cells

Rechargeable lithium-ion batteries (LIBs) have received tremendous attention over the past three decades due to their relatively higher energy density, longer cycle life, and lower environmental impact compared to the traditional Ni-Cd/MH battery systems. Due to the continuously increasing demand of the world energy consumption, the general goal for battery development is to increase the energy densities. However, it is extremely difficult to improve the state-of-the-art LIBs’ energy densities furthermore because of the limited capacities of the graphite anode (~370 mAh g^-1) and insertion-oxide cathode (~250 mAh g^-1). Therefore, alternative cathode and anode materials offering higher capacities should be developed.

Lithium-sulfur (Li-S) battery is one of the prospective candidates in this regard not only because both sulfur and lithium have high theoretical capacities but also because sulfur is low cost and environmentally friendly. Moreover, lithium metal has a low negative potential. Nevertheless, the commercialization of Li-S batteries has been hindered by several issues, such as the insulating nature of sulfur and its intermediates, polysulfide shuttle effects, safety concerns of the lithium metal electrode, etc. Intensive efforts have been taken to solve these problems by developing novel sulfur host materials, solid-state electrolytes, separators and interlayers, and binders, etc., during the past decade. It should be noted that advanced fibers have played extremely important roles in the abovementioned solutions due to their substantial surface-to-volume ratio, flexibility in surface functionalities, large porosity, and good mechanical properties.

Here, I will mainly concentrate my efforts on the advancements and progress of fibers employed for achieving high-performance Li-S batteries: from liquid to solid-state cells. The fundamental electrochemistry and challenges of Li-S batteries will firstly be discussed. It will then focus on advantages of using fibers in Li-S batteries and the mechanisms behind their operations which are detailed from two perspectives: i) separator selection and design; and ii) solid-state electrolytes. I will talk about how fiber-based separators improve the rate capability of Li-S cells, and how nanofiber-based solid-state electrolytes prevent the growth of the lithium dendrites, addressing the safety issue of Li-S cells. Finally, the critical research directions needed and the remaining challenges to be addressed in this area will be summarized.