TY - JOUR
T1 - Electrochemical studies of N-methyl N-propyl pyrrolidinium bis(trifluoromethanesulfonyl) imide ionic liquid mixtures with conventional electrolytes in LiFePO4/Li cells
AU - Theivaprakasam, Sowmiya
AU - Macfarlane, Douglas Robert
AU - Mitra, Sagar
PY - 2015
Y1 - 2015
N2 - The electrochemistry of the electrolyte plays a significant role in the performance of lithium ion batteries. In order to further investigate the effect of combining an ionic liquid with a conventional electrolyte, a hybrid electrolyte (HE) based on a mixture of 38% N-methyl-N-propyl-pyrrolidinium bis(trifluromethanesulfonyl) imide in an electrolyte consisting of LiPF6 in Ethylene Carbonate: Diethyl Carbonate (1:1) was studied and compared with the properties of a standard organic electrolyte in this work. Thermal measurements reveal that the addition of the ionic liquid improves the thermal stability of the hybrid electrolyte. The interfacial behavior was studied in lithium symmetric cells and it was found that the combined effects of the ionic liquid and the conventional electrolyte results in lower interfacial resistance. The charge-discharge behaviour of LiFePO4 / Li cells was investigated; at the end of 100 cycles, the discharge capacity of the cell with LP30, HE and [C3mpyr][TFSI] was 141 mAh/g, 148 mAh/g and 45mAh/g, respectively. Analysis of the separator recovered from Li/LiFePO4 cells that had been stored for 30 days at 20°C shows iron dissolution from the cathode into the LP30 electrolyte, but not into the hybrid electrolyte. Posthumous studies of the cycled electrodes were carried out using FTIR, XRD, FEG-SEM and HR-TEM analyses, show that the HE forms a permeable interface on the cathode material which prevents metal dissolution from the cathode structure, leading to better cyclic performance
AB - The electrochemistry of the electrolyte plays a significant role in the performance of lithium ion batteries. In order to further investigate the effect of combining an ionic liquid with a conventional electrolyte, a hybrid electrolyte (HE) based on a mixture of 38% N-methyl-N-propyl-pyrrolidinium bis(trifluromethanesulfonyl) imide in an electrolyte consisting of LiPF6 in Ethylene Carbonate: Diethyl Carbonate (1:1) was studied and compared with the properties of a standard organic electrolyte in this work. Thermal measurements reveal that the addition of the ionic liquid improves the thermal stability of the hybrid electrolyte. The interfacial behavior was studied in lithium symmetric cells and it was found that the combined effects of the ionic liquid and the conventional electrolyte results in lower interfacial resistance. The charge-discharge behaviour of LiFePO4 / Li cells was investigated; at the end of 100 cycles, the discharge capacity of the cell with LP30, HE and [C3mpyr][TFSI] was 141 mAh/g, 148 mAh/g and 45mAh/g, respectively. Analysis of the separator recovered from Li/LiFePO4 cells that had been stored for 30 days at 20°C shows iron dissolution from the cathode into the LP30 electrolyte, but not into the hybrid electrolyte. Posthumous studies of the cycled electrodes were carried out using FTIR, XRD, FEG-SEM and HR-TEM analyses, show that the HE forms a permeable interface on the cathode material which prevents metal dissolution from the cathode structure, leading to better cyclic performance
KW - Hybrid Electrolyte
KW - Symmetric cells
KW - Ionic liquid
KW - Interfacial study
KW - Iron dissolution
UR - http://goo.gl/obzjbA
U2 - 10.1016/j.electacta.2015.08.137
DO - 10.1016/j.electacta.2015.08.137
M3 - Article
VL - 180
SP - 737
EP - 745
JO - Electrochimica Acta
JF - Electrochimica Acta
SN - 0013-4686
ER -