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In a lithium‐ion battery, the organic solvent in the electrolyte simply acts as a medium that facilitates ionic charge transfer, whereas for the lithium‐sulfur (Li—S) battery, the choice of the electrolyte is critical as it influences the chemical nature of the soluble polysulfides and the cycling stability of the lithium metal anode. Li‐S batteries currently use ether‐based electrolytes with high polysulfide solubility. Until now, however, the necessary requirements and the roles of the electrolytes have been inconclusive. This work elucidates the essential features and functions of the electrolyte based on an intensive investigation into 17 variants of solvents. Furthermore, examples of electrolytes for high performance, rechargeable Li—S batteries are suggested. The three major study procedures are (1) analyzing the chemical stability of reactive polysulfide species and lithium metal in the solvents of choice, (2) inspecting the chemical reactivity of lithium metal in a polysulfide solution, and (3) evaluating the influences of the solvent on the performance of Li—S cells. Based on the chemical and electrochemical test results, we suggest that the stability of the active materials (i.e., lithium metal and lithium polysulfides) should be ensured in an electrolyte for the proper operation of Li—S cells, that chemical reactions between the polysulfide species and lithium metal should be negligible during the charge–discharge process. In addition, we have confirmed that the high polysulfide solubility is essential for high rate performance. [ABSTRACT FROM AUTHOR]

Abstract CN(CH 2) 2 Si(CH 3)(OCH 2 CH 2 OCH 3) 2 (BNS) is used as electrolyte solvent to improve the safety for LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM)/graphite battery. BNS increases the thermal stability of the carbonate-based electrolyte with (de) lithiated cathode/anode and the electrochemical stability of coin cells. By using an optimal BNS-based electrolyte formula, 13 Ah NCM/graphite prismatic cell achieves 95.8% retain of capacity at 2 C/3 C (charge/discharge) rate after 600 cycles. Meanwhile, 13 Ah prismatic cell exhibits improved safety performance in the nail penetration test. [ABSTRACT FROM AUTHOR]

Abstract: A new fire retardant-dimethyl methyl phosphate (DMMP) was tested as a nonflammable electrolyte solvent for Li-ion batteries. It is found that in the addition of chloro-ethylene carbonate (Cl-EC) as an electrolyte additive, the electrochemical reduction of DMMP molecules can be completely suppressed and the graphite anode can be cycled very well with high initial columbic efficiency (∼84%) and excellent cycling stability in the DMMP electrolyte. The prismatic C/LiCoO2 batteries using 1.0molL−1 LiClO4 +10% Cl-EC+DMMP electrolyte exhibited almost the same charge and discharge performances as those using conventional carbonate electrolytes, suggesting a feasible use of this new electrolyte for constructing nonflammable Li+-ion batteries. [Copyright &y& Elsevier]

Abstract: Dimethyl methyl phosphonate (DMMP) was selected and tested as a non-flammable solvent for primary and secondary lithium batteries, because of its non-flammability, good solvency of lithium salts and appropriate liquidus properties. Experimental results demonstrated that DMMP can solvate considerable amount of commonly used lithium salts to form non-flammable and Li+-conducting electrolyte, which has very wide electrochemical window (>5V vs. Li) and excellent electrochemical compatibility with metallic lithium anode and oxide cathodes. Primary Li–MnO2 cells using DMMP-based electrolyte showed almost the same discharge performances as those using organic carbonate electrolytes, and also, Li–LiMn2O4 cells using DMMP electrolyte exhibited greatly improved cycleability and dischargeability, suggesting a feasible application of this new electrolyte for constructing high performance and non-flammable lithium batteries. [Copyright &y& Elsevier]