LI METAL-FREE RECHARGEABLE LIMN2O4/CARBON CELLS - THEIR UNDERSTANDING AND OPTIMIZATION

So-called "rocking-chair" rechargeable batteries that use lithium intercalation compounds for the positive and negative electrodes should be safer than batteries that contain free-lithium metal. Such a cell, using the spinel LiMn2O4 as the positive electrode and carbon as the negative electrode, was optimized as a function of various operating parameters. These cells reversibly insert 0.32 Li atoms per Mn at an average output voltage of 3.7 V, yielding an effective specific energy of 250 mWh/g of electrode materials (3 times that of Ni-Cd). They can sustain high current rates similar to Ni-Cd batteries, and can be discharged to 0 V without any degradation of their operating conditions. By systematically studying the stability of several electrolyte systems, we were able to minimize electrolyte decomposition (by controlling drastically the charge cut-off voltage) so that these cells show a promising cycle life even at 55-degrees-C while maintaining 75% of their initial capacity.