In this paper we describe a modified (AEG/CH) coated separator for Li-S batteries in which the shuttling phenomenon of the lithium polysulfides is restrained through two types of interactions: activated expanded graphite (AEG) flakes interacted physically with the lithium polysulfides, while chitosan (CH), used to bind the AEG flakes on the separator, interacted chemically through its abundance of amino and hydroxyl functional groups. Moreover, the AEG flakes facilitated ionic and electronic transfer during the redox reaction. Live H-cell discharging experiments revealed that the modified separator was effective at curbing polysulfide shuttling; moreover, X-ray photoelectron spectroscopy analysis of the cycled separator confirmed the presence of lithium polysulfides in the AEG/CH matrix. Using this dual functional interaction approach, the lifetime of the pure sulfur-based cathode was extended to 3000 cycles at 1C-rate (1C = 1670 mA/g), decreasing the decay rate to 0.021% per cycle, a value that is among the best reported to date. A flexible battery based on this modified separator exhibited stable performance and could turn on multiple light-emitting diodes. Such modified membranes with good mechanical strength, high electronic conductivity, and anti-self-discharging shield appear to be a scalable solution for future high-energy battery systems.

A separator comprising polypropylene (PP)coated with MoO3 nanobelts, prepared through facile grinding of commercial MoO3 powder, exhibit excellent electrochemical performance at high C-rate for Li–S battery.

Despite issues related to dendrite formation, research on Li metal anodes has resurged because of their high energy density. In this study, graphene oxide (GO) layers are decorated onto Li metal anodes through a simple process of drop-casting and spray-coating. The self-assembly of GO is exploited to synthesize coatings having compact, mesoporous, and macroporous morphologies. The abilities of the GO coatings to suppress dendrite formation are compared through Li|Li symmetrical cell charging at a current density of 5 mA cm −2 for 2000 cyclesa particularly abusive test. The macroporous structure possesses the lowest impedance, whereas the compact structure excels in terms of stability. Moreover, GO exhibits a low nucleation overpotential and is transformed into reduced GO with enhanced conductivity during the operation of the cells; both factors synergistically mitigate the issue of dendrite formation. Li−S batteries incorporating the GO-decorated Li anodes exhibit an initial capacity of 850 mA h g −1 and maintain their stability for 800 cycles at a C-rate of 1 C (1675 mA h g −1 ), suggesting the applicability of GO in future rechargeable batteries.

In this paper, we demonstrate a unique multifunctional separator prepared by sputtering a thin layer of graphite on top of a commercial polypropylene−polyethylene separator. This modified separator, when used in a Li−Li symmetrical cell, suppresses Li dendrite growth by maintaining a uniform ionic flux on top of the Li metal. When employed in a lithium−sulfur battery (LSB), the thin graphite layer can retard the shuttling of lithium polysulfides (LiPSs) through a physical interaction, as demonstrated through the live discharge of an H-cell. Moreover, the conductivity of the graphite resulted in it, also acting as a secondary current collector, thereby leading to higher utilization of the sulfur content and assisting in the redox mechanism of the LiPSs. The electrochemical performance of cells incorporating the modified separator was characterized by a low overpotential (in the case of Li−Li symmetrical cells) and high Coulombic efficiency and a low decay rate (in the LSB, simultaneously). The roll-to-roll sputtering of the thin layer of graphite on the pristine separator would appear to be a scalable solution for the commercialization of such modified separators.

No abstract