of 2600 W h kg −1 . [2] However, the development of Li-S battery is plagued by several challenges that must be addressed. First of all, sulfur is both electrically and ionically insulating, as well as its lithiated product Li 2 S, which necessitates the incorporation of sulfur into a conductive matrix. [3] In addition, quite different from traditional Li intercalation compounds, sulfur suffers electrochemical dissolution and deposition reactions and generates a series of polysulfide (PS n ) species, of which highorder PS n (4 ≤ n ≤ 8) are soluble in etherbased electrolyte and prone to diffuse to the anode side for reducing deeply to the insoluble Li 2 S 2 and Li 2 S. Correspondingly, Li 2 S 2 and Li 2 S could migrate back to the cathode and be oxidized. [4] The so-called "shuttle effect" leads to an irreversible loss of active sulfur and a fast degradation of cycle stability. Consequently, during the redox reaction, the repetitive dissolution and deposition reactions of the PS n passivate both cathode and anode gradually, resulting in a considerable increase of the electrode impedance. [5] Moreover, the density difference between sulfur (2.07 g cm −3 ) and Li 2 S (1.66 g cm −3 ) leads to a significant volume expansion, which is adverse to the mechanical strength of sulfur cathode. [2c,6] All of these factors restrict severely the electrochemical performance of sulfur cathode.To date, upsurge of attention has been paid in fabricating high-efficiency and stable sulfur cathode, the vital component of the Li-S battery. These efforts focus on developing novel nanocomposites by incorporating sulfur into various host materials, such as carbonaceous materials (including porous carbon, [7] hollow carbon spheres, [8] carbon nanotube/fibers, [9] graphene and its derivatives, [10] or hybrid carbon hosts, [11] ) conducting polymers, [12] metal oxides, [13] and metal or covalent organic frameworks. [14] These host materials are expected to promote the electron transfer, accommodate the volumetric expansion, and trap the soluble PS n . In this respect, carbonaceous materials are proven to be a promising option owing to their excellent electrical conductivity, outstanding mechanical strength, and multiple architectures. Typically, the members with higherdimensional contrast structure are endowed with exclusive superiority in compositing with sulfur. In detail, carbon nanotubes (CNTs) possess classic 1D structure and exhibit a self-weaving Carbon materials have attracted extensive attention as the host materials of sulfur for lithium-sulfur battery, especially those with 3D architectural structure. Here, a novel 3D graphene nanosheet-carbon nanotube (GN-CNT) matrix is obtained through a simple one-pot pyrolysis process. The length and density of CNTs can be readily tuned by altering the additive amount of carbon source (urea). Specifically, CNTs are in situ introduced onto the surface of the graphene nanosheets (GN) and show a stable covalent interaction with GN. Besides, in the GN-CNT matrix, cobalt nanoparticles with...

Lithium-sulfur (Li-S) batteries are regarded as the promising next-generation energy storage device due to the high theoretical energy density and low cost. However, the practical application of Li-S batteries is still limited owing to the cycle stability of both the sulfur cathode and lithium anode. In particular, the instability in the bulk and at the surface of the lithium anode during cycling becomes a huge obstacle for the practical application of Li-S battery. Herein, a Li-rich lithium-magnesium (Li-Mg) alloy is investigated as an anode for Li-S batteries, based on the consideration of improving the stability in the bulk and at the surface of the lithium anode. Our experimental results reveal that the robust passivation layer is formed on the surface of the Li-Mg alloy anode, which is helpful to reduce side reactions, and enable the smooth surface morphology of anode during cycling. Meanwhile, the mixed electron and Li-ion conducting matrix of the Li-poor Li-Mg alloy as a porous skeleton structure can also be formed after delithiation, which can guarantee the structural integrity of the anode in the bulk during Li stripping/plating process. Therefore, the Li-rich Li-Mg alloy is demonstrated to be a very promising anode material for Li-S battery.

A lithium anode protected with a porous Al2O3layer is beneficial for improving the cycle stability and capacity retention of a lithium–sulfur battery.

The lithium-sulfur (Li-S) battery is expected to be the high-energy battery system for the next generation. Nevertheless, the degradation of lithium anode in Li-S battery is the crucial obstacle for practical application. In this work, a porous carbon paper obtained from corn stalks via simple treating procedures is used as interlayer to stabilize the surface morphology of Li anode in the environment of Li-S battery. A smooth surface morphology of Li is obtained during cycling by introducing the porous carbon paper into Li-S battery. Meanwhile, the electrochemical performance of sulfur cathode is partially enhanced by alleviating the loss of soluble intermediates (polysulfides) into the electrolyte, as well as the side reaction of polysulfides with metallic lithium. The Li-S battery assembled with the interlayer exhibits a large capacity and excellent capacity retention. Therefore, the porous carbon paper as interlayer plays a bifunctional role in stabilizing the Li anode and enhancing the electrochemical performance of the sulfur cathode for constructing a stable Li-S battery.