The positive impact of a fluoroethylene carbonate (FEC) solvent on the interfacial stability of Li metal electrodes and the electrochemical performance of lithium-sulfur (Li-S) cells is investigated. To confirm the effects of FEC on electrolyte decomposition and cell resistance, the surface chemistry and impedance of an Li electrode cycled in electrolytes with and without a FEC solvent are investigated using attenuated total reflectance–Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectrometry (ToF-SIMS), and electrochemical impedance spectroscopy. A protective layer with a FEC solvent for the formation of robust SEI and carbonate-based solvents for the suppression of polysulfide attack against an Li anode was formed on the Li anode by UV-curing polymerization. It is found that the protective layer with FEC effectively suppresses the significant overcharge by the shuttle process of polysulfide species and improves cycling performance of Li-S cells.

Room-temperature Na-metal-based rechargeable batteries, including Na-O2 and Na-S systems, have attracted attention due to their high energy density and the abundance of sodium resources. Although these systems show considerable promise, concerns regarding the use of Na metal should be addressed for their success. Here, we report dendrite-free Na-metal electrode for a Na rechargeable battery, engineered by employing nonflammable and highly Na(+)-conductive NaAlCl4·2SO2 inorganic electrolyte, as a result, showing superior electrochemical performances to those in conventional organic electrolytes. We have achieved a hard-to-acquire combination of nondendritic Na electrodeposition and highly stable solid electrolyte interphase at the Na-metal electrode, enabled by inducing polygonal growth of Na deposit using a highly concentrated Na(+)-conducting inorganic electrolyte and also creating highly dense passivation film mainly composed of NaCl on the surface of Na-metal electrode. These results are highly encouraging in the development of room-temperature Na rechargeable battery and provide another strategy for highly reliable Na-metal-based rechargeable batteries.

Lithium bis(oxalato)borate (LiBOB) is utilized as an oxidative additive to prevent the unwanted electrolyte decomposition on the surface of Li 1.17 Ni 0.17 Mn 0.5 Co 0.17 O 2 cathodes. Our investigation reveals that the LiBOB additive forms a protective layer on the cathode surface and effectively mitigates severe oxidative decomposition of LiPF 6 -based electrolytes. Noticeable improvements in the cycling stability and rate capability of Li 1.17 Ni 0.17 Mn 0.5 Co 0.17 O 2 cathodes are achieved in the LiBOB-added electrolyte. After 100 cycles at 60 • C, the discharge capacity retention of the Li 1.17 Ni 0.17 Mn 0.5 Co 0.17 O 2 cathode was 28.6% in the reference electrolyte, whereas the LiBOB-containing electrolyte maintained 77.6% of its initial discharge capacity. Moreover, the Li 1.17 Ni 0.17 Mn 0.5 Co 0.17 O 2 cathode with LiBOB additive delivered a superior discharge capacity of 115 mAh g −1 at a high rate of 2 C compared with the reference electrolyte. The OCV of a full cell charged in the reference electrolyte drastically decreased from 4.22 V to 3.52 V during storage at 60 • C, whereas a full cell charged in the LiBOB-added electrolyte exhibited superior retention of the OCV. . [1][2][3][4] Because a large reversible capacity of lithium-rich cathodes is attained with the condition of charging to the voltage range of 4.6-4.8 V at the first charge, 1 the oxidative decomposition of LiPF 6 /carbonate-based electrolytes occurring above 4.5 V vs. Li/Li + is inevitable. 5,6 The anodic limit of current electrolytes is not high enough to prevent such side reactions, which results in the formation of a resistive surface film on the cathode and continuous electrolyte decomposition at high voltages. Therefore, these undesired reactions limit the practical application of lithium-rich cathode materials. From this viewpoint, the formation of surface films through the use of oxidative additives in the electrolytes is thought to be one of the most effective strategies to stabilize the cathode-electrolyte interface in lithium-ion batteries (LIBs). 7,8 Recently, many research groups have reported the effect of electrolyte additives preventing significant electrolyte decomposition at lithium-rich cathodes that are operated above 4.5 V.9-13 Tri(hexafluoro-iso-propyl)phosphate (HFiP) was proposed as a oxidative additive (OA) to improve the cycling performance of the lithium-rich cathode Li 8 These authors also reported that the salt-type additive, LiFOB, can serve as a bi-functional additive, modifying the cathode and anode interfaces, in a subsequent paper.14 In addition, it has been reported that a LiFOB-lithium bis(oxalato)borate (LiBOB) combination leads to an improvement in the electrochemical performances of graphite/Li 1.2 Mn 0.55 Ni 0.15 Co 0.1 O 2 full cells 30• C. Lu et al. reported that the LiFOB additive improved the cycling stability of graphite/xLi 2 MnO 3 · (1-x)LiMO 2 full cells at room temperature. 4 These authors mentioned that the LiFOB-originated solid electrolyte interphase (SEI) on the anode effectively ...

Extensive research efforts have been devoted to the development of alternative battery chemistry to replace the current technology of lithium-ion batteries (LIBs).Here, we demonstrate that the Li−SO 2 battery chemistry, already established 30 years ago, has considerable potential to be regarded as a candidate for post-LIBs when proper nanotechnology is exploited. The recently developed nanostructured carbon materials greatly improve the battery performances of the Li−SO 2 cells, including a reversible capacity higher than 1000 mAh g −1 with a working potential of 3 V and excellent cycle performance over 150 cycles, and provide a theoretical energy density of about 651 Wh kg −1 , which is about 70% higher than that of the currently used LIB.The nanostructured carbon cathodes offer not only an enlarged active surface area, but also a mechanical buffer to accommodate insulating discharge products upon discharge. Considering the other outstanding properties of the SO 2 -based inorganic electrolyte, such as non-flammability and significantly higher ionic conductivities, wisely selected nanotechnology renders the Li−SO 2 battery chemistry a very promising approach towards the development of a post-LIB system.