As one important component of sulfur cathodes, the carbon host plays a key role in the electrochemical performance of lithium‐sulfur (Li‐S) batteries. In this paper, a mesoporous nitrogen‐doped carbon (MPNC)‐sulfur nanocomposite is reported as a novel cathode for advanced Li‐S batteries. The nitrogen doping in the MPNC material can effectively promote chemical adsorption between sulfur atoms and oxygen functional groups on the carbon, as verified by X‐ray absorption near edge structure spectroscopy, and the mechanism by which nitrogen enables the behavior is further revealed by density functional theory calculations. Based on the advantages of the porous structure and nitrogen doping, the MPNC‐sulfur cathodes show excellent cycling stability (95% retention within 100 cycles) at a high current density of 0.7 mAh cm‐2 with a high sulfur loading (4.2 mg S cm‐2) and a sulfur content (70 wt%). A high areal capacity (≈3.3 mAh cm‐2) is demonstrated by using the novel cathode, which is crucial for the practical application of Li‐S batteries. It is believed that the important role of nitrogen doping promoted chemical adsorption can be extended for development of other high performance carbon‐sulfur composite cathodes for Li‐S batteries.

this promising prospect is hindered by quite a few challenges in Li-S cells. The fi rst one is the intrinsically low electronic conductivity of sulfur (5 × 10 −30 S cm −1 ) and its end discharge products Li 2 S/Li 2 S 2 , which limits the full utilization of sulfur. [ 7 ] Accordingly, downsizing sulfur to nanosize particles and adding a large amount of carbon have been proposed to address the above issue. However, these methods unfortunately sacrifi ce the energy density of the Li-S cells. [ 2,6 ] In particular, high fractions of light carbon materials like porous carbon or carbon nanotube (CNT) do not contribute to the capacity at all but signifi cantly lower the volmetric energy density, which is undesired for higheffi cient portable devices or EV energy storage applications. [ 8 ] The second and more detrimental issue that limits Li-S cell performance is the formation of soluble long-chain polysulfi des such as Li 2 S 8 and Li 2 S 6 , which easily diffuse out of High energy and cost-effective lithium sulfur (Li-S) battery technology has been vigorously revisited in recent years due to the urgent need of advanced energy storage technologies for green transportation and large-scale energy storage applications. However, the market penetration of Li-S batteries has been plagued due to the gap in scientifi c knowledge between the fundamental research and the real application need. Here, a facile and effective approach to integrate commercial carbon nanoparticles into microsized secondary ones for application in high loading sulfur electrodes is proposed The slurry with the integrated particles is easily cast into electrode laminates with practically usable mass loadings. Uniform and crack-free coating with high loading of 2-8 mg cm −2 sulfur are successfully achieved. Based on the obtained thick electrodes, the dependence of areal specifi c capacity on mass loading, factors infl uencing electrode performance, and measures used to address the existing issues are studied and discussed.

this makes it one of the most promising candidates to meet the energy needs for powering future EVs. [ 6,[19][20][21][22][23][24][25][26] Research on Li-S batteries began in the early 1960s. [ 24,27 ] In the following fi ve decades, only limited progress was made based on sporadic research efforts in this fi eld. Recently, in the light of nanoporous carbon materials, the cell performance was greatly improved and the research passion on Li-S batteries has been revived. [ 20,28,29 ] Unlike Li-ion batteries that use Li + -ion insertion chemistry in intercalation inorganic compounds for both cathode and anode, Li-S batteries are based on a conversion reaction of S forming Li 2 S via polysulfi des as intermediate species (Li 2 S n , n = 4-8), which could deliver a high specifi c capacity of 1672 mAh g −1 . [ 20,24 ] However, to realize commercial Li-S batteries, there are still many technical challenges to be solved from cathode to anode, as well as electrolyte. [ 22,30,31 ] The performances of different components in Li-S batteries are often related to each other. For example, the improvements in S based cathode could benefi t from reduced degradation in metallic Li anode by minimizing polysulfi de migration and shuttle effect. In general, Li-S batteries suffer from low S utilization and short cycle life, which originate from poor conductivity of sulfur and its discharged product Li 2 S, self-discharge, large volume expansion (≈80%) upon the formation of Li 2 S, and the dissolution of polysulfi des in liquid electrolytes. [ 24,32,33 ] The insulating nature of S and the large volume expansion of S cathode upon discharge can be largely overcome via forming nanocomposite with highly porous carbon materials, which could greatly improve the S utilization and rate performance. [ 21,25,32,34 ] In addition, the porous cathode structure could hold the formed polysulfi des in the pores so as to reduce the degree of dissolution of polysulfi des into the electrolyte. Recently, it was also found that the synthesis of metastable small S molecules of S 2-4 confi ned in a conductive microporous carbon matrix could avoid the unfavorable formation of long chain polysulfi des, thus avoiding the S dissolution problem. [35][36][37] Although signifi cant improvements have been made in the cyclability of S/C composite cathodes, [ 21,24,28,38 ] there are still many problems involved in Li-S batteries before this technology can be adopted for practical applications. In contrast to the enormous research efforts on S cathode side, the Li metal anode in Li-S batteries, which is directly involved in the shuttle mechanism and the capacity failure, has attracted much less attention. [ 24,39 ] Recently, with the signifi cant improvements in the development of high capacity S cathodes using stable C/S composites, the research spotlight is falling on the anode side With the signifi cant progress that has been made toward the development of cathode materials and electrolytes in lithium-sulfur (Li-S) batteries in recent years, the stability of the anod...

Magnesium battery is potentially a safe, cost-effective, and high energy density technology for large scale energy storage. However, the development of magnesium battery has been hindered by the limited performance and the lack of fundamental understandings of electrolytes. Here, we present a study in understanding coordination chemistry of Mg(BH4)2 in ethereal solvents. The O donor denticity, i.e. ligand strength of the ethereal solvents which act as ligands to form solvated Mg complexes, plays a significant role in enhancing coulombic efficiency of the corresponding solvated Mg complex electrolytes. A new electrolyte is developed based on Mg(BH4)2, diglyme and LiBH4. The preliminary electrochemical test results show that the new electrolyte demonstrates a close to 100% coulombic efficiency, no dendrite formation, and stable cycling performance for Mg plating/stripping and Mg insertion/de-insertion in a model cathode material Mo6S8 Chevrel phase.

The basic requirements for getting reproducible Li-S battery data have been discussed in this work. Unlike Li-ion batteries, electrolyterich environment significantly deteriorates the cycling stability of Li-S batteries assembled and tested under the same conditions. The reason has been assigned to the low concentration of polysulfide-containing electrolyte in the cells, which shows profound influences on both sulfur cathode and lithium metal anode. With optimized sulfur/electrolyte (S/E) ratio of 50 g L −1 , a good balance between electrolyte viscosity, wetting ability, diffusion rate of dissolved polysulfide and nucleation/growth of short-chain Li 2 S/Li 2 S 2 has been established along with largely reduced corrosion of the lithium metal anode. Accordingly, good cyclability, high reversible capacity and Coulombic efficiency are achieved in Li-S cell with optimized S/E ratio without any additive. Other factors such as sulfur content in the composite and sulfur loading in the whole electrode also need careful concern in Li-S battery system in order to generate reproducible results and gauge the various methods used to improve Li-S battery technology.Lithium-sulfur (Li-S) batteries have attracted increasing interest because of their high theoretical capacity, natural abundance and environmental benignity. 1-5 Li-S battery operates by reduction of sulfur during discharge to form lithium polysulfides with different chain lengths and finally to insoluble Li 2 S 2 or Li 2 S. The multi-electron conversion reaction generates high capacity and energy of 1675 Ah kg −1 and 2650 Wh kg −1 , respectively, drastically higher than those of state-of-the-art lithium ion batteries. 6-9 Li-S batteries suffer from the soluble intermediate products, a series of polysulfides Li 2 S x (x > 2), which participate in the well documented 'sulfur shuttle mechanism' reactions. 1,10 The undesired shuttle effect not only lowers the Coulombic efficiency, but also causes fast capacity degradation and severe self-discharge. Moreover, the irreversible relocation of polysulfides in the whole cell during "shuttle reactions" is also the reason leading to the quick loss of energy-bearing materials. [11][12][13] The end result is the significantly shortened lifespan of Li-S battery, which plagues its market penetration.In an effort to overcome the hurdles in Li-S battery technology, various approaches have been proposed, spanning from immobilization of sulfur in the different kinds of hosting materials, 10,11,14-17 electrolyte modification 18-20 and anode protection by employing LiNO 3 as the electrolyte additive. 3,21-24 It is known that electrolyte is critical for Li-S battery thus novel electrolyte or electrolyte additives have been explored. 25,26 However, the basic information on the electrolyte composition and the electrolyte amount used in each test are rarely mentioned in literature. 27 For lithium ion batteries, excessive amount of electrolyte always improves the results from half-cell tests, although it is not the case in practical applicatio...