However, this intriguing olivine material suffers from intrinsic sluggish kinetics of lithium (de-)insertion, which limits the reversible reaction in practical lithium cells. LiMnPO 4 is a potential cathode for lithium-ion battery of high thermal stability, low cost, environmental sustainability and high theoretical energy density. Preliminary results at 20 ☌ indicates a capacity of 130 mAh g − 1 at C/10 rate (17 mA g − 1) with coulombic efficiency higher than 99.5%, thereby suggesting PEO:Pyr 12O1 FTFSI:LiFTFSI as suitable electrolyte for lithium-metal polymer batteries for stationary storage applications, coupled for example with PV and wind generation. Impedance spectroscopy measurements reveal low resistance of the electrode/electrolyte interface at both the anode and the cathode. Combined with the LiFePO 4 composite electrode, whose pores are filled with the Pyr 12O1 FTFSI:LiFTFSI electrolyte, and Li-metal anode, it yields Li/LiFePO 4 cells delivering at 40 ☌ stable capacity (150 mAh g − 1 or 0.7 mAh cm − 2) with coulombic efficiency higher than 99.5%. The ternary membrane has a PEO:Pyr 12O1 FTFSI:LiFTFSI composition of 20:6:4 by mole, which ensures thermal stability up to 220 ☌, overall ionic conductivity of 10 − 3 S cm − 1 at 40 ☌ and suitable Li + transport properties. Lithium metal/LiFePO 4 cells with such an electrolyte offer promising results in terms of stable LiFePO 4 /electrolyte interface, investigated by impedance spectroscopy, as well as delivered capacity above 160 mAh g À1 with 81% of retention after 80 galvanostatic cycles.Ī cross-linked polymer membrane formed by poly(ethylene oxide) (PEO), N-methoxyethyl-N-methylpyrrolidium (fluorosulfonyl)(trifluoromethanesulfonyl)imide (Pyr 12O1 FTFSI) ionic liquid and LiFTFSI salt is proposed as the electrolyte for lithium-metal batteries. At this temperature, the electrolyte has viscosity of 65.8 mPa s, ionic conductivity of the order of 5 mS cm À1, and limiting current density of 10 À2 mA cm À2. Thus, it is proposed for application at 60 C in a lithium cell with stable LiFePO 4 cathode. The Pyr 14 TDI-LiTDI mixture, melting at 49 C, shows remarkable stability within the 50–250 C range, as well as suitable ionic conductivity, lithium ion transport, and electrochemical stability window. A new ionic liquid formed by coupling 4,5-dicyano-2-(trifluoromethyl)imidazole (TDI À) anion with N-butyl-N-methyl-pyrrolidinium (Pyr 14 +) cation is successfully synthesized and characterized by Raman spectroscopy, thermal and rheological analyses, as well as electrochemical techniques.
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