Structural and electrochemical properties of Cr-substituted lithium manganese oxide thin films

The advantages of Cr substitution in lithium manganese oxide (LiMn2O4) for cathode of rechargeable battery were investigated. LiCrxMn2-xO4 (x <= 0.3) thin films were deposited on Pt/Ti/SiO2/Si substrates via a sol-gel process. The LiCrxMn2-xO4 specimens were found to have the spinel structure of pristine LiMn2O4 with no detectable secondary phase. The Cr ions were found to be trivalent and to occupy the octahedral sites of the spinel lattice. The Cr-substituted specimens exhibited a new phonon mode near 570 cm(-1) in the Raman spectrum. It is ascribed to octahedral Cr3+-O bonding (T(2)g) that is located close to the mode due to octahedral Mn3+-O bonding (580 cm(-1)). According to charge-discharge (C-D) cycling data on the LiCrxMn2-xO4 cathodes, the specimens of x = 0.02 and 0.05 kept larger capacities than that of the pristine LiMn2O4 cathode up to 700 cycles. The x = 0.05 cathode showed initial capacity close to that of x = 0.02. Above 100th cycle, the x = 0.05 cathode showed better capacity retention than that of x = 0.02. Possible reason for the improved capacity retention by the Cr substitution was discussed. [GRAPHICS] .

Automated summary

The advantages of Cr substitution in LiMn2O4 cathode for rechargeable battery were investigated. LiCrxMn2-xO4 thin films were deposited via sol-gel process and found to have spinel structure with no detectable secondary phase. The Cr ions were trivalent and occupied the octahedral sites of the spinel lattice. The Cr-substituted specimens exhibited a new phonon mode and showed better capacity retention in charge-discharge cycling tests.