The development and commercialization of Li ion batteries during recent decades is one of the great successes of modern electrochemistry. The increasing reliability of Li ion batteries makes them natural candidates as power sources for electric vehicles. However, their current energy density, which can reach an average of 200 Wh kg−1 on the single cell level, limits the possible driving range of electric cars propelled by Li‐ion batteries. Thereby, there is a strong driving force to develop power sources technologies beyond Li‐ion batteries that will mark breakthroughs in energy density capabilities. Li‐sulfur batteries have high theoretical energy density that can revolutionize electrochemical propulsion capability. Consequently, in recent years there has been much work throughout the world related to these systems. The scope of work on this topic justifies frequent publications of review articles that summarize recent extensive work and provide guidelines and direction for focused future work. Here, a comprehensive, systematic work related to Li‐sulfur battery systems is described, beginning with the Li anode challenges, carbon‐encapsulated sulfur cathodes, and various kinds of relevant electrolyte solutions. Based on the work described and parallel recent studies by other groups, important and comprehensive guidelines for further research and development efforts in this field are provided.

The development of Li2S electrodes is a crucial step toward industrial manufacturing of Li-S batteries, a promising alternative to Li-ion batteries due to their projected two times higher specific capacity. However, the high voltages needed to activate Li2S electrodes, and the consequent electrolyte solution degradation, represent the main challenge. We present a novel concept that could make feasible the widespread application of Li2S electrodes for Li-S cell assembly. In this concept, the addition of redox mediators as additives to the standard electrolyte solution allows us to recover most of Li2S theoretical capacity in the activation cycle at potentials as low as 2.9 VLi, substantially lower than the typical potentials >4 VLi needed with standard electrolyte solution. Those novel additives permit us to preserve the electrolyte solution from being degraded, allowing us to achieve capacity as high as 500 mAhg(-1)Li2S after 150 cycles with no major structural optimization of the electrodes.

Sulfur cathodes have excellent theoretical properties for use as positive electrodes in rechargeable lithium batteries. However they suffer from an internal redox shuttle process which limit their capacity because the sulfur reduction products, Li x S y species, cannot be fully re-oxidized. In order to overcome this problem, lithium nitrate is commonly used as an additive to the electrolyte solution, suppressing the shuttle phenomena in Li-sulfur batteries. We rigorously studied the electrochemical behavior of LiNO 3 in electrolyte solutions and with electrodes relevant to Li-S cells. EQCM UV-Vis and XPS spectroscopies were used in conjunction with standard electrochemical measurements, in order to determine the stability limits of this additive. An irreversible reduction of the nitrate species occurs in Li-S cells resulting in a precipitation of electrolyte solutions decomposition products such as LiF and oxygencontaining polymeric species formed by reactions of the ethereal solutions due to nitrate reduction on the cathode side below 1.9 V vs. Li .We showed that both the reversible capacity and the voltage profile of Li-S cells are significantly improved when the limiting cutoff potentials for the sulfur cathodes is set above the red-ox potential of LiNO 3 .

Non-aqueous, rechargeable battery development is one of the most important challenges of modern electrochemistry. Li ion batteries are a commercial reality for portable electronics with intensive efforts underway to apply this technology to electro-mobility. Extensive investigations of high energy density Li-sulfur and Li-oxygen systems have also been carried-out. Efforts to promote high energy density power sources for electric vehicles have been accompanied by intensive work on the development of rechargeable sodium and magnesium batteries for load-leveling applications. The electrolyte solution is a key consideration in all batteries determining cell stability, cycle life, and safety. This review discusses the importance of solution selection for advanced, high-voltage, Li ion batteries, sodium ion batteries, as well as Li-sulfur, Li-oxygen and magnesium batteries. Li ion battery standard solutions are discussed and their further optimization is outlined. Limitations of Li metal electrodes are explained. Unique problems in the use of conventional non-aqueous solutions for Li-oxygen batteries, related to intrinsic stability, are delineated. Finally, electrolyte solutions for Mg batteries are briefly reviewed, concluding that only the relatively inert ethereal solutions are suitable for future consideration. Several systems exhibit wide electrochemical windows and reversible behavior with Mg anodes, however compatibility with high-voltage/high-capacity cathodes remains a major challenge.It is impossible to imagine modern society without electrochemical power sources. The electronic revolution relies heavily on the use of highly sophisticated portable devices -including cellular phones with amazing applications, laptops, video cameras and more. All this advancement depends on the availability of high-energy density, safe and cost-effective power sources. The challenge of discovering rechargeable power sources has increased markedly in recent years, spurred by the demand for electro-mobility to replace propulsion by fossil fuels that have traditionally powered internal combustion engines.Challenges such as electrochemical propulsion by electric vehicles (EV), and the need for large-scale storage of sustainable energy (i.e. load-levelling applications) have motivated and stimulated the development of novel rechargeable batteries and super-capacitors. Batteries deliver high energy density, but have only limited cycle life and power density; super-capacitors, on the other hand, provide high power density and very prolonged cycling. Lithium-ion batteries are the focus of intensive R&D (research and development) efforts because they promise high energy density that may be suitable for electrical propulsion. Batteries (especially those like Li ion batteries with high energy density) are exceedingly complicated devices: three active bulks and two active interfaces must function simultaneously without side reactions or detrimental reflections.Consequently, R&D of novel battery systems requires investing time and effort in...

a Composite sulfur-carbon electrodes were prepared by encapsulating sulfur into the micropores of highly disordered microporous carbon with micrometer-sized particles. The galvanostatic cycling performance of the obtained electrodes was studied in 0.5M Li bis(fluorosulfonyl)imide (FSI) in methylpropyl pyrrolidinium (MPP) FSI ionic-liquid (IL) electrolyte solution. We demonstrated that the performance of Li-S cells is governed by the formation of solid electrolyte interphase (SEI) during the initial discharge at potentials lower than 1.5V vs. Li/Li + . Subsequent galvanostatic cycling is characterized by one plateau voltage profile specific to quasi-solid-state reaction of Li ions with sulfur encapsulated in the micropores in solvent deficient conditions. The stability of the SEI thus formed, is critically important for the effective desolvation of Li ions participating in quasi-solid-state reactions. We proved that realization of the quasi-solid-state mechanism is controlled not by the porous structure of the carbon host but rather by the nature of the electrolyte solution composition and the discharge cut off voltage value. The cycling behavior of these cathodes is highly dependent on sulfur loading. The best performance can be achieved with electrodes in which the sulfur loading was 60% by weight, when sulfur filled micropores are not accessible for N2 molecules according to gas adsorption isotherm data. A limited contact of the confined sulfur with the electrolyte solution results in the highest reversible capacity and initial Coulombic efficiency. This insight into the mechanism provides a new approach in the development of new electrolyte solutions and additives for Li-S cells.