Structural and Thermal Stabilities of Spinel LiMn2O4 Materials Under Commercial Power Batteries Cycling and Abusive Conditions

The commercial 18650 spinel LiMn2O4/graphite high power batteries are prepared and the structural and thermal stabilities of the spinel LiMn2O4 cathode materials under high rate cycling and abusive conditions are investigated using the commercial 18650 LiMn2O4/graphite high power batteries. Results show that the batteries present the best power performance when the compaction density of LiMn2O4 electrode is 2.93g cm-3. The microstructure of LiMn2O4 materials undergoes obvious distortion due to the Mn dissolution after the LiMn2O4 power batteries have been subjected to 100 cycles with discharge rate of 8 C at 25 o C and discharge rate of 5C at 55 o C. The charge-transfer resistance (Rct) of power batteries after cycling at high temperature rises significantly. During battery overcharge, the solid electrolyte interface (Rsei) and Rct of power batteries increase greatly and the electrolyte shows obviously less reaction activities on LiMn2O4 electrode than on Li(Ni1/3Co1/3Mn1/3)O2 electrode. The reactions of fully charged LiMn2O4 cathodes and graphite anodes with electrolyte inside battery during battery overcharge and oven tests can be activated at much lower temperature than that outside battery, while these reactions do not occur during short current test in the fully charged batteries