K. Zaghib

Temperature Effect on LiFePO4 Cathode Performance

Two forms of LiFePO4 material were evaluated in lithium cells. One type of LiFePO4 (PI) that has a particle size ranging from 1-5 µm is compared to LiFePO4 (P-II) consisting of nano-particles. Coated electrodes on Al-carbon with thickness varying from 18 to 25 µm were used in this study. The addition of VGCF carbon fiber greatly improved the rate capability at low temperature. This suggests a good conductivity networking and wettability in the cathode. LiFePO4 (P-II) has improved the low- and high-rate discharge capacity. When VGCF fibers were combined with LiFePO4 (P-II) in the same composite cathode, the high rate capacity at 12C was increased by 51% compared to LiFePO4 (P-I) cathode with carbon black. At -10°C and at 2C rate, 90 mAh/g was delivered from the cell. Cycling at 60°C occurred with negligible capacity fade after 400 cycles. Furthermore, the cell was capable of good performance at high rate with 120 mAh/g at 10C, and it still has a good reserve at 25C with 73mAh/g.

HQ Asymmetric Super Capacitor: Graphite-Li4Ti5O12/Ionic Liquid/Carbon

Introduction Electrodes containing Li4Ti5O12 have good Liion intercalation and de-intercalation reversibility and exhibit no structural change (zero-strain insertion material) during charge–discharge cycling. Thus, Li4Ti5O12 is an interesting candidate in negative electrodes for solid-state [1] and liquid-type [2] lithiumion batteries. This active material has a middischarge voltage close to 1.55 V versus Li/Li, which is very promising for electrodes in a large number of battery applications [3, 5]. It can be used as an anode with: (a) high-voltage cathodes in Li-ion batteries, and (b) carbon electrodes in hybrid supercapacitors, which was suggested for the first time by Zaghib and Armand [3,4]. . The CLi4Ti5O12 powder was characterized by X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) observations. The electrochemical discharge and charge of asymmetric supercapacitor (ASC) behaviour was determined in a liquid electrolyte and ionic liquid (molten salt). Some comparisons between electrode processes using PVDF versus water-soluble binder (WSB) are presented. The performance ASC using new negative based on multilayer Graphite Li4Ti5O12 at 0. 25 and 60°C will be presented