The rapidly developing market for mobile electronics and hybrid electric vehicles (HEVs) has prompted the urgent need for batteries with high energy density, long cycle life, high efficiency, and low cost.[1] Recently, rechargeable lithium-sulfur (Li-S) batteries have attracted considerable attention because of their high theoretical gravimetric (volumetric) energy density of 2570 W h kg À1 (2200 W h l À1 ), and low cost. [2] However, the use of S as cathode material for Li-S batteries suffers from two major issues. One is the insulating nature of S, which results in low active-material utilization and limited rate capability.[2a] The other is the formation of electrolytesoluble polysulfides; these polysulfide intermediates, which are generated in the discharge/charge process, dissolve in the electrolyte and migrate to the Li anode, a process known as the shuttle effect.[3] Consequently, the S cathode suffers a significant loss of S during cycling, resulting in a rapid capacity decrease. Many strategies have been used to address these problems, such as the impregnation of S into various conductive porous matrixes, [4] surface coating of S, [5] and the use of suitable electrolytes [6] and additives. [7] Although remarkable improvements have been achieved, the application of Li-S batteries is still hindered by the intrinsic drawbacks of S. Therefore, it is of great importance to explore and develop new high-energy cathode materials with improved electronic conductivity and cycling stability, to cover the shortfalls of S and provide alternative choices for practical applications.From this perspective, selenium, an element belonging to the same group in the periodic table as sulfur, is a prospective candidate for cathode materials. Although Se has a lower theoretical gravimetric capacity (675 mA h g À1 ) than S (1675 mA h g À1 ), its higher density (ca. 2.5 times that of S) offsets the deficiency and provides a high theoretical volumetric capacity density (3253 mA h cm À3 ), comparable to that of S (3467 mA h cm À3 ). It has been reported that Li-Se batteries deliver a high output voltage, [8] so Li-Se batteries are also expected to have a high volumetric energy density. It is known that for applications in portable devices and HEVs, volumetric energy density is more important than gravimetric energy density because of the limited battery packing space. [9] Moreover, the electronic conductivity of Se (1 10 À3 S m À1 ) is considerably higher than that of S (5 10 À28 S m À1 ), [8] which suggests that Se could have higher utilization rate, better electrochemical activity, and faster electrochemical reaction with Li. Therefore, the advantages of Se promise an attractive alternative cathode material for building high-energy batteries for specific applications, including consumer electronics and transportation. However, at present, research on Li-Se batteries is still at a very early stage.Recently, Abouimrane et al. [8] conducted pioneering work on the use of Se as a cathode material. The results show that, even bulk ...

The Li metal anode has long been considered as one of the most ideal anodes due to its high energy density. However, safety concerns, low efficiency, and huge volume change are severe hurdles to the practical application of Li metal anodes, especially in the case of high areal capacity. Here it is shown that that graphitized carbon fibers (GCF) electrode can serve as a multifunctional 3D current collector to enhance the Li storage capacity. The GCF electrode can store a huge amount of Li via intercalation and electrodeposition reactions. The as-obtained anode can deliver an areal capacity as high as 8 mA h cm and exhibits no obvious dendritic formation. In addition, the enlarged surface area and porous framework of the GCF electrode result in lower local current density and mitigate high volume change during cycling. Thus, the Li composite anode displays low voltage hysteresis, high plating/stripping efficiency, and long lifespan. The multifunctional 3D current collector promisingly provides a new strategy for promoting the cycling lifespan of high areal capacity Li anodes.