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Three ionic liquid belonging to the N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imides (Pyr(1),nTFSI with n=4,5,8) have been added as co-solvent to two commonly used electrolytes for Li-ion cells: (a) 1 M lithium hexafluorophosphate (LiPF6) in a mixture of ethylene carbonate (EC) and linear like dimethyl carbonate (DMC) in 1 : 1 v/v and (b) 1 M lithium bis-(trifluoromethanesulfonyl)imide (LiTFSI) in EC : DMC 1 : 1 v/v. These electrolyte formulations (classified as P and T series containing LiPF6 or LiTFSI salts, respectively) have been analyzed by comparing ionic conductivities, transport numbers, viscosities, electrochemical stability as well as vibrational properties. In the case of the Pyr(1,5)TFSI and Pyr(1,8)TFSI blended formulations, this is the first ever reported detailed study of their functional properties in Li-ion cells electrolytes. Overall, P-electrolytes demonstrate enhanced properties compared to the T-ones. Among the various P electrolytes those containing Pyr(1,4)TFSI and Pyr(1,5)TFSI limit the accumulation of irreversible capacity upon cycling with satisfactory performance in lithium cells.

The realization of a high-performance Li-ion full-cell with an anode prominently based on silicon, which can surpass the energy densities of commercial graphite-based Li-ion batteries and cyclability compatible for industrial applications, is still a challenge. Here, we report a Li-ion full-cell that combines a silicon/graphene/carbon (Si/G/C) nanocomposite anodic material, with a commercial LiNi0.33Mn0.33Co0.33O2 (NMC111) cathode. Using a pre-lithiation technique, the proposed Li-ion full-cell exhibits an energy density of ∼400 Wh kg−1 at the electrode material level, with a capacity >1.6 mAh cm−2 and a capacity retention exceeding 90% after 300 cycles at C/2. These performances have been achieved by properly designing the anode material composed by Si nanoparticles wrapped by few-layer graphene flakes. An additional carbon coating is used to further improve the electron conductivity and mechanical integrity of the anodic structure upon charge/discharge cycles. The remarkable performance of the full-cell considering the scalability of the Si-based anode synthesis is a step forward towards the commercialization of high-capacity and high-energy density Li-ion batteries.