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Graphene has good stability and adjustable dielectric properties along with tunable morphologies, and hence can be used to design novel and high-performance functional materials. Here, we have reported a facile synthesis method of nanoscale Fe3O4/graphene capsules (GCs) composites using the combination of catalytic chemical vapor deposition (CCVD) and hydrothermal process. The resulting composite has the advantage of unique morphology that offers better synergism among the Fe3O4 particles as well as particles and GCs. The microwave-absorbing characteristics of developed composites were investigated through experimentally measured electromagnetic properties and simulation studies based on the transmission line theory, explained on the basis of eddy current, natural and exchange resonance, as well as dielectric relaxation processes. The composites bear minimum RL value of -32 dB at 8.76 GHz along with the absorption bandwidth range from 5.4 to 17 GHz for RL lower than -10 dB. The better performance of the composite based on the reasonable impedance characteristic, existence of interfaces around the composites, and the polarization of free carriers in 3D GCs that make the as-prepared composites capable of absorbing microwave more effectively. These results offer an effective way to design high-performance functional materials to facilitate the research in electromagnetic shielding and microwave absorption.

With over fivefold energy capacity, sulfur demonstrates superior advantages over current commercial intercalation compound (LiCoO 2 and LiFePO 4 ) cathode materials. [3][4][5] Despite its considerable advantages, the practical application of Li-S battery has been hindered by poor cycle life due to the shuttle effect, leading to quick capacity decay due to the loss of active materials and an low Coulombic efficiency. [6,7] Moreover, the insulating nature of S/Li 2 S and as large as 78% volume expansion of sulfur cathode when initial state S (2.03 g cm −3 ) is fully converted to final state Li 2 S (1.66 g cm −3 ) result in rapid capacity fading and short cycle life due to the low utilization of active materials and poor electrical contact between sulfur particles and conductive additives. [8,9] Aiming to address these negative impact of at least some of the detrimental processes described above for realizing commercial application of highenergy Li-S battery, various considerable strategies have been focused on cathode material modification including N-doped materials, [10][11][12] porous materials, [13] hierarchical materials, [14] metal oxides [15,16] transition metal disulfides, [17] and functional separator modification, [18,19] as well as employment of solid or As one of the important ingredients in lithium-sulfur battery, the binders greatly impact the battery performance. However, conventional binders have intrinsic drawbacks such as poor capability of absorbing hydrophilic lithium polysulfides, resulting in severe capacity decay. This study reports a new type of binder by polymerization of hydrophilic poly(ethylene glycol) diglycidyl ether with polyethylenimine, which enables strongly anchoring polysulfides for highperformance lithium sulfur batteries, demonstrating remarkable improvement in both mechanical performance for standing up to 100 g weight and an excellent capacity retention of 72% over 400 cycles at 1.5 C. Importantly, in situ micro-Raman investigation verifies the effectively reduced polysulfides shuttling from sulfur cathode to lithium anode, which shows the greatly suppressed shuttle effect by the polar-functional binder. X-ray photoelectron spectroscopy analysis into the discharge intermediates upon battery cycling reveals that the hydrophilic binder endows the sulfur electrodes with multidimensional Li-O, Li-N, and S-O interactions with sulfur species to effectively mitigate lithium polysulfide dissolution, which is theoretically confirmed by density-functional theory calculations.

Safety, nontoxicity, and durability directly determine the applicability of the essential characteristics of the lithium (Li)‐ion battery. Particularly, for the lithium–sulfur battery, due to the low ignition temperature of sulfur, metal lithium as the anode material, and the use of flammable organic electrolytes, addressing security problems is of increased difficulty. In the past few years, two basic electrolyte systems are studied extensively to solve the notorious safety issues. One system is the conventional organic liquid electrolyte, and the other is the inorganic solid‐state or quasi‐solid‐state composite electrolyte. Here, the recent development of engineered liquid electrolytes and design considerations for solid electrolytes in tackling these safety issues are reviewed to ensure the safety of electrolyte systems between sulfur cathode materials and the lithium‐metal anode. Specifically, strategies for designing and modifying liquid electrolytes including introducing gas evolution, flame, aqueous, and dendrite‐free electrolytes are proposed. Moreover, the considerations involving a high‐performance Li+ conductor, air‐stable Li+ conductors, and stable interface performance between the sulfur cathode and the lithium anode for developing all‐solid‐state electrolytes are discussed. In the end, an outlook for future directions to offer reliable electrolyte systems is presented for the development of commercially viable lithium–sulfur batteries.