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Rechargeable room‐temperature sodium–sulfur (RT Na–S) batteries are a promising energy storage technology, owing to the merits of high energy density and low cost. However, their electrochemical performance has been severely hindered by the poor compatibility between the existing electrolytes and the electrodes. Here, we demonstrate that an all‐fluorinated electrolyte, containing 2,2,2‐trifluoro‐N,N‐dimethylacetamide (FDMA) solvent, 1,1,2,2‐tetrafluoroethyl methyl ether (MTFE) anti‐solvent and fluoroethylene carbonate (FEC) additive, can greatly enhance the reversibility and cyclability of RT Na–S batteries. A NaF‐ and Na3N‐rich cathode electrolyte interphase derived from FDMA and FEC enables a "quasi‐solid‐phase" Na–S conversion, eliminating the shuttle of polysulfides. The MTFE not only reduces polysulfide dissolution, but also further stabilizes the Na anode via a tailored solvation structure. The as‐developed RT Na–S batteries deliver a high capacity, long lifespan, and enhanced safety. [ABSTRACT FROM AUTHOR]

Wearable electronics require lightweight and flexible batteries, of which lithium‐sulfur (Li‐S) batteries are of great interest due to their high gravimetric energy density. Nevertheless, flexible Li‐S batteries have unsatisfactory electrochemical performance owing to electrode fracture during repeated bending, the volume change of sulfur species and the severe shuttle effect. Binders play essential roles in these batteries but have always lacked attention. Herein, a self‐healing polyvinylpyrrolidone‐polyethyleneimine (PVP‐PEI) binder cross‐linked by hydrogen bonds, which also regulates polysulfide redox kinetics, is reported. The dynamic hydrogen‐bonding networks repair the cracks and ensure the integrity of the electrode while numerous polar groups such as CO and ‐NH2 suppress the shuttle effect by immobilizing polysulfides. Therefore, Li‐S batteries with the PVP‐PEI binder exhibit excellent cycling stability (a capacity decay rate of 0.0718% per cycle at 1 C after 450 cycles), an outstanding areal capacity of 7.67 mAh cm−2 even under a high sulfur loading (7.1 mg cm−2) and relatively lean electrolyte conditions (E/S ratio = 8 µL mg−1). Flexible Li‐S pouch cells using the PVP‐PEI binder show a stable performance for 140 cycles and a favorable capacity retention of over 95% after 2800 bending cycles, confirming its application potential in high‐performance flexible Li‐S batteries. [ABSTRACT FROM AUTHOR]

Abstract: Due to high energy density, low cost, and nontoxicity, lithium–sulfur (Li–S) batteries are considered as the most promising candidate to satisfy the requirement from the accelerated development of electric vehicles. However, Li–S batteries are subjected to lithium polysulfides (LiPSs) shuttling due to their high dissolution in liquid electrolyte, resulting in low columbic efficiency and poor cycling performance. Moreover, the Li metal as an indispensable anode of Li–S batteries shows serious safety issues derived from the lithium dendrite formation. The replacement of liquid electrolytes with solid‐state electrolytes (SSEs) has been recognized as a fundamental approach to effectively address above problems. In this review, the progress on applying various classes of SSEs including gel, solid‐state polymer, ceramic, and composite electrolytes to solve the issues of Li–S batteries is summarized. The specific capacity of Li–S batteries is effectively improved due to the suppression of LiPSs shuttling by SSEs, while the rate and cycling performance remain relatively poor owing to the limited ionic conductivity and high interfacial resistance. Designing smart electrode/electrolyte integrated architectures, enabling the high ionic transportation pathway and compatible electrode/electrolyte interface, may be an effective way to achieve high performance solid‐state Li–S batteries. [ABSTRACT FROM AUTHOR]

A carbon-sulfur hybrid with pomegranate-like core-shell structure, which demonstrates a high rate performance and relatively high cyclic stability, is obtained through carbonization of a carbon precursor in the presence of a sulfur precursor (FeS2) and a following oxidation of FeS2 to sulfur by HNO3. Such a structure effectively protects the sulfur and leaves enough buffer space after Fe3+ removal and, at the same time, has an interconnected conductive network. The capacity of the obtained hybrid is 450 mA h g−1 under the current density of 5 C. This work provides a simple strategy to design and prepare various high-performance carbon-sulfur hybrids for lithium-sulfur batteries. [ABSTRACT FROM AUTHOR]

Sheets of Li4Ti5O12 with high crystallinity are coated with nitrogen- doped carbon (NC-LTO) using a controlled process, comprising hydrothermal reaction followed by chemical vapor deposition (CVD). Acetonitrile (CH3CN) vapor is used as carbon and nitrogen source to obtain a thin coating layer of nitrogendoped carbon. The layer enables the NC-LTO material to maintain its sheet structure during the high-temperature CVD process and to achieve high crystallinity. Doping with nitrogen introduces defects into the carbon coating layer, and this increased degree of disorder allows fast transportation of lithium ions in the layer. An electrode of NC-LTO synthesized at 700°C exhibits greatly improved rate and cycling performance due to a markedly decreased total cell resistance and enhanced Li-ion diffusion coefficient (DLi). Specific capacities of 159.2 and 145.8 mAhg-1 are obtained using the NC-LTO sheets, at charge/discharge rates of 1 and 10 C, respectively. These values are much higher than values for LTO particles did not undergo the acetonitrile CVD treatment. A capacity retention value as high as 94.7% is achieved for the NC-LTO sheets after 400 cycles in a half-cell at 5 C discharge rate. [ABSTRACT FROM AUTHOR]

Lithium–sulfur (Li–S) batteries are catching intensive worldwide attention for the outstanding energy density, low‐cost, and nontoxic nature of sulfur. However, the very limited lifespan and rate performance of Li–S systems originating from dissolution and diffusion of long‐chain polysulfides in liquid electrolytes, as well as the intrinsic poor conductivity of sulfur, severely hinder their practical application. Herein, an electrospinning and subsequent dipping and drying method is developed here to fabricate a duplex architecture consisting of reduced graphene oxide (rGO) layer and BaTiO3 (BTO)‐decorated carbon nanofibers (BTO@CNFs), and it is used as a multifunctional interlayer for Li–S batteries. The 3D interwoven CNFs with conductive pathways for both electrons and ions can enhance the contact between polysulfides with BTO nanoparticles and promote the reuse of inactivated sulfur. Additionally, the ferroelectric BTO nanoparticles adhered on CNFs can realize a highly robust trapping to polysulfides via the extremely polar interaction. Moreover, the surface rGO layer can act as a textural barrier to intercept the shuttling polysulfides. Consequently, the modified Li–S batteries with the rGO/BTO@CNF interlayer deliver superior electrochemical performance of 865 mAh g−1 after 200 cycles at 0.3 C and a rate capability of 672 mAh g−1 at 3 C. [ABSTRACT FROM AUTHOR]