An improved high-power battery with increased thermal operating range: C-LiFePO4//C-Li4Ti5O12

The carbon-coated LiFePO4 and C-Li4Ti5O12 particles of 90 nm in diameter have been tested as active elements of electrodes of Li-ion batteries. The 18650-size cell using the usual electrolyte 1 mol L-1 LiPF6 in ethylene carbonate (EC) and diethylene carbonate (DEC) displays a charge capacity of 650 mAh at low C-rate and retains more than 80% of rated capacity at 60C charge rate (1 min). 2032-size coin cells have been tested with different electrolytes: 1.5 mol L-1 lithium tetrafluoroborate LiBF4 in EC+ gamma-butyrolactone (GEL), and 0.5 mol L-1 lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)(2). LiTFSI) + 1 mol L-1 LiBF4 in EC + GBL, aiming to replace the less stable LiPF6 salt. The LiTFSI-based electrolyte can be used owing to the low operating voltage that avoids the corrosion of the aluminum of the collector. This electrolyte shows the best results as the performance is even higher at 60 degrees C. The infrared images show that the temperature of the cell never reaches this temperature during cycling, making this battery a high-power battery with remarkable thermal stability. The maximum temperature reached by the cell is 34 degrees C at 40C-rate and 40 degrees C at 60C. The free EC-based electrolytes even operate at 80 degrees C by using 1 mol L-1 lithium bis(fluorosulfonyl)imide (LiFSI) in GBL or 1 mol L-1 LiFSI in PC + GBL, thus increasing importantly the operating temperature range for the battery. The carbon coated on LTO depresses the evolution of gases during charge discharge. (C) 2012 Elsevier B.V. All rights reserved.