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The finding of appropriate electrolytes and applying them to low-temperature lithium-ion batteries is of special interest. Lithium difluoro (oxalate) borate (LiODFB) and lithium tetrafluorobotate (LiBF4) are promising salts for lithium-ion batteries owing to their unique characteristics. In this work, the electrochemical behaviors of blend salts of LiODFB and LiBF4 with different mole ratio were studied by employment of ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl sulfite (DMS) as mixed solvents in order to optimize the low-temperature performance for lithium-ion batteries. The results show that the electrolyte system of LiODFB/LiBF4 (1:1, by molar)-EC/DEC/DMS (1:2:1, by volume) is the optimized electrolyte, and the discharge capacity of the electrodes in the optimized electrolyte is 82.5 mAh g−1 at −40°C, maintaining 55.7% of the room temperature capacity and nearly 100% of capacity retention for 50 cycles. The electrolyte exhibits not only excellent film-forming characteristics, but also low impedance of the interface film at low temperature. Especially, the action mechanism of LiODFB, LiBF4 as well as functional solvent on optimization of low-temperature performance is discussed.

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Graphite electrode surfaces are pretreated by spray‐deposition method with 0.5 mol L−1 Li2SO4 aqueous solution. The physical and electrochemical properties of a solid electrolyte interphase (SEI) film formed on the surface of Li2SO4‐treated graphite electrode are investigated by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, and electrochemical measurements. The results show that the SEI film formed, promoted by Li2SO4, is thin, stable, effective, and elastic to accommodate volume changes of graphite electrode during electrochemical cycles. Due to the fact that the Li/mesophase carbon microbeads (MCMB) cell based on Li2SO4‐treated graphite electrode exhibits excellent cycling performance and low interfacial impedance, we can deduce that such modifies have positive implications for lithium‐ion batteries (LIBs), offering the possibility of faster‐charging LIBs and LIBs that are suitable for rate‐demanding applications, such electric vehicles and hybrid electric vehicles.

The lithium transition‐metal phosphate LiFe0.6Mn0.4PO4 has two operating potentials, 3.5 V and 4.1 V, which is favorable for increasing the energy and power densities of lithium‐ion batteries (LIBs). To study the compatibility between LiFe0.6Mn0.4PO4 and electrolytes, lithium bis(oxalate)borate (LiBOB) is chosen as the lithium salt, based upon ethylene carbonate (EC), dimethyl carbonate (DMC), and dimethyl sulfite (DMS) as the supporting electrolyte solvents. The electrochemical performances of lithium hexafluorophosphate (LiPF6)‐based and LiBOB‐based electrolytes are compared. The combination of LiBOB and DMS can facilitate the formation of an effective passivation film. In addition, LiBOB‐EC/DMS electrolyte exhibits better cycle and rate performance. The results suggest that LiBOB‐EC/DMS electrolyte has good compatibility with LiFe0.6Mn0.4PO4, which makes it an attractive electrolyte for rechargeable LIBs based upon LiFe0.6Mn0.4PO4 cathodes.

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