Enhanced cycling stability of o-LiMnO₂ cathode modified by lithium boron oxide coating for lithium-ion batteries

The effect of lithium boron oxide (LBO) coating on the electrochemical performance of orthorhombic LiMnO₂ (o-LiMnO₂) cathode for lithium-ion batteries is investigated. o-LiMnO₂ synthesized via solid state synthesis technique is modified with LBO addition. The presence of LBO is identified via Fourier transform infrared spectroscopy analysis. o-LiMnO ₂ is observed to transform to a spinel-like phase during cycling which undergoes capacity fading. Studies indicate that the presence of 1-2 wt% LBO results in an improved capacity and better capacity retention with cycling. The pristine sample reveals a maximum specific capacity of 172 mAhg ^-1, whereas the LBO-modified samples display about 189.1 mAhg ^-1 in the cycling tests conducted at a rate of 50 mAg^-1 in the voltage range of 2-4.5 V. After 70 cycles, the LBO-modified LiMnO ₂ displayed higher capacity retention of 175 mAhg^-1 as compared to the pristine sample that exhibited 130 mAhg^-1. By analyzing the charge-discharge behavior, it is observed that the capacity obtained from lithium insertion into the tetrahedral sites of the spinel structure is more or less constant throughout the cycling and that the bulk of the capacity loss is resulting when lithium is inserted into the octahedral sites of the spinel structure. Impedance measurement reveals a reduced charge-transfer resistance for the LBO-modified samples suggesting that the presence of LBO is countering capacity loss arising from insertion of lithium into the octahedral sites thus contributing to the overall cycling stability.