Here, we focus on the high-resolution detection of sulfide-based species differing by one sulfur atom by using the nanopore technology.
Up to now, existing analytical techniques to identify intermediate polysulfides and monitor Li–S batteries electrolyte composition, such as UV-vis, X-ray, mass spectrometry or cyclic voltammetry 22 do not allow to detect and sequence at the single molecule level these parasitic redox species. Alternatively, other strategies to tackle the polysulfide shuttle effect have focused on the separator to prevent (S n) 2− diffusion to the anode with either micro intrinsic porosity 19, 20 or using grafting chemistry to repeal (S n) 2− via repulsive electrostatic interactions 21. Such supramolecular structures were also used as ionic conducting polymer membrane in Li-ion batteries 16, 17 and cyclodextrins trapping properties were exploited by placing cyclodextrins polymers in S-based electrodes to address the redox shuttle issue in Li–S batteries, e.g., migration of soluble polysulfides Li 2S n (3 ≤ n ≤ 8), intermediates back and forth between the two electrodes 18.
Cyclodextrins have recently entered the field of batteries as well, as witnessed by the design of highly stretchable binders integrating sliding ring polyrotaxanes 15, e.g., self-assembled architectures of cyclodextrins to auto-repair fractured Si electrodes. Such properties have already been widely exploited for thermal switches 11 and in medicine for drug delivery 12 or as a molecular adapter to identify the DNA nucleotides 13, or small organic molecules 14. Thus the feasibility to use the temperature as a stimulus 9 to regulate on demand the uptake or release of trapped species within their cavities, offers an interesting auto-repairing function 10. Following nature’s strategy relying on the use of sacrificial weak bonds for self-repairing, battery scientists have developed materials based on bio-molecules or polymers, with auto-repairing properties 6 relying on dynamic supramolecular self-assembly such as hydrogen bonding, ionic bonding or host-guest interaction 5, 7.Īmong supramolecular materials, cyclodextrins have been extensively studied because of their rich molecular recognition that is temperature dependent and their wide range of functionalization. Not surprisingly, most of the auto-repairing approaches are inspired by biological systems and benefit from the general strategies and formalisms well established for most living creatures. Great advances have been made over the last few years to either restore the electrode conductivity 7 or at the electrolyte-membrane component to regulate species migration when injured 8. The latter calls for the development of smart batteries embedded with intelligent sensing 4 and curing chemical functionalities 5, 6. Hence the ongoing activities center on alternative technologies (Na-ion, Li-air, Li–S,…) but also in the quest of means to enhance present batteries lifespan, durability and reliability. Nevertheless, improvements are needed to increase their lifetime and sustainability. Among them, the Li-ion batteries are the technology of choice as they offer the largest energy density while their cost is continuously decreasing 2, 3. Our findings offer innovative perspectives to use nanopores as electrolyte sensors and chemically design membranes capable of selective speciation of parasitic molecules for battery applications and therefore pave the way towards smarter electrochemical storage systems.īatteries, as one of the most versatile energy storage technologies, play a central role in the ongoing transition from fossil fuels to renewable energy 1. By investigating the host-guest interaction between polysulfides of different chain-lengths and cyclodextrins, via combined chemical approaches and molecular docking simulations, and using a selective nanopore sensor inserted into a lipid membrane, we demonstrate that supramolecular polysulfide/cyclodextrin complexes only differing by one sulfur can be discriminated at the single molecule level. Here, we report the use of biological membranes hosting a nanopore sensor for electrical single molecule detection and use aqueous sodium polysulfides encountered in sulfur-based batteries for proof of concept. However, they could be used as a toolbox for injecting chemical functionalities to capture unwanted species and enhance battery lifetime. Research on batteries mostly focuses on electrodes and electrolytes while few activities regard separator membranes.