TU/e), the Netherlands. Currently, he is conducting his research at Forschungszentrum Jülich (Germany). His research interests focus on the design and development of effective strategies for high-performance Li-S batteries. Dmitri L. Danilov, Ph.D., has a background in physics and mathematics and obtained his M.Sc. at the Saint-Petersburg University in 1993. In 2003, he got Ph.D. degree from the University of Tilburg.In 2002, he joined Eurandom institute in Eindhoven University of Technology, being involved in various national and international research projects. His current research interests include mathematical modeling of complex electrochemical systems, including Li-ion and NiMH batteries, ageing and degradation processes, thin-film batteries, and advanced characterization methods. Starting 2017, he joined IEK-9 in the Forschungszentrum Jülich.

of lithium-ion batteries on a large scale. Therefore, the development of rechargeable batteries with high energy density and reliability would be a priority. One of the most promising candidates is lithiumsulfur (Li-S) batteries, which have great potential for addressing these issues. [5][6][7] The conversion reaction based on the reduction of sulfur to lithium sulfides (Li 2 S) yields a high theoretical capacity of 1675 mAh g −1 (S 8 + 16 Li = 8 Li 2 S). Such a capacity is significantly higher than that of insertion cathode materials such as LiCoO 2 and LiFePO 4 , which deliver capacities below 200 mAh g −1 . The 16-electron electrochemical charge transfer reaction with a working voltage of about 2.2 V allows a specific energy density of 2600 Wh kg −1 for Li-S batteries. With optimal configuration, a practical energy density of 500-600 Wh kg −1 would be achievable when considering additional battery components. [8] Moreover, sulfur possesses the merits of abundant resources, safety, and environmental friendliness. The breakthrough in Li-S batteries will promote the development and application of renewable energy.Despite the great potential for replacing lithium-ion batteries, Li-S batteries still face several critical problems. [9] The principal one is the sluggish conversion kinetics of the sulfur reduction reaction (SRR) during discharging due to the low conductivity of sulfur species and complicated 16-electron conversion Lithium-sulfur batteries are one of the most promising alternatives for advanced battery systems due to the merits of extraordinary theoretical specific energy density, abundant resources, environmental friendliness, and high safety. However, the sluggish sulfur reduction reaction (SRR) kinetics results in poor sulfur utilization, which seriously hampers the electrochemical performance of Li-S batteries. It is critical to reveal the underlying reaction mechanisms and accelerate the SRR kinetics. Herein, the critical issues of SRR in Li-S batteries are reviewed. The conversion mechanisms and reaction pathways of sulfur reduction are initially introduced to give an overview of the SRR. Subsequently, recent advances in catalyst materials that can accelerate the SRR kinetics are summarized in detail, including carbon, metal compounds, metals, and single atoms. Besides, various characterization approaches for SRR are discussed, which can be divided into three categories: electrochemical measurements, spectroscopic techniques, and theoretical calculations. Finally, the conclusion and outlook part gives a summary and proposes several key points for future investigations on the mechanisms of the SRR and catalyst activities. This review can provide cutting-edge insights into the SRR in Li-S batteries.

The detection of chemical messenger molecules, such as neurotransmitters in nervous systems, demands high sensitivity to measure small variations, selectivity to eliminate interferences from analogues, and compliant devices to be minimally invasive to soft tissue. Here, an organic electrochemical transistor (OECT) embedded in a flexible polyimide substrate is utilized as transducer to realize a highly sensitive dopamine aptasensor. A split aptamer is tethered to a gold gate electrode and the analyte binding can be detected optionally either via an amperometric or a potentiometric transducer principle. The amperometric sensor can detect dopamine with a limit of detection of 1 μM, while the novel flexible OECT-based biosensor exhibits an ultralow detection limit down to the concentration of 0.5 fM, which is lower than all previously reported electrochemical sensors for dopamine detection. The low detection limit can be attributed to the intrinsic amplification properties of OECTs. Furthermore, a significant response to dopamine inputs among interfering analogues hallmarks the selective detection capabilities of this sensor. The high sensitivity and selectivity, as well as the flexible properties of the OECT-based aptasensor, are promising features for their integration in neuronal probes for the in vitro or in vivo detection of neurochemical signals.