Impact of Electrode Nature on Lithium-Ion Battery Performances with Ionic Liquids or Carbonate Electrolytes
In this work, we report the performance of three full cell configurations: graphite (Cgr)// LiFePO4 (LFP), Li4Ti5O12 (LTO)// LiFePO4 (LFP) and Li4Ti5O12 (LTO)// LiNi1/3Mn1/3Co1/3O2 (NMC), with five different ionic liquids and one organic carbonate electrolytes. Their cycling results, at 333 K, with a pyrrolidinium [PYR14][NTf2], series of imidazolium ionic liquids ([C1CnIm][NTf2] and [C1C1CnIm][NTf2]/ n= 4 and 6) associated with LiNTf2 (1mol.L-1) then an organic electrolyte (LiPF6 (1mol.L-1) DEC: EC), are depicted in Figure 1 (a-c).
Some trends have been found. For Cgr//LFP system cycling is observed only in the presence of organic additive, vinylene carbonate (VC) (Fig. 1a). Carbonates, except for LTO//NMC cell, show lower capacity then ILs based electrolytes (Fig. 1). The highest capacity is observed for LTO//NMC system with ([C1C4Im][NTf2], [PYR14][NTf2] and carbonate electrolyte, ~180 mAh.g-1, ~140 mAh.g-1 and ~180 mAh.g-1, respectively (Fig. 1c). The introduction of a donating group (-CH3) on position two of the imidazolium ring (C2-H → C2-CH3) in [C1C1CnIm][NTf2] highly improve the performance of Cgr//LFP cells (Fig. 1) (5). Besides LTO//NMC, the charge/discharge performance is improved by extending the alkyl chain length of the imidazolium ring. Finally, in LTO//LFP and LTO//NMC, higher performances were obtained with ([C1C4Im][NTf2] compare to [PYR14][NTf2].
From these results, we highlight the tremendous impact of each element of the system (electrode, electrolyte, and separator (6)) onto the charge discharge capacity, especially with ionic liquids based ones.
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