Study On LiMnO₂/Li₄Ti₅O₁₂ Battery

As the environmental problems and energy crisis become more and more serious, in the past years, considerable efforts have been made to research on lithium ion batteries used for electrical vehicles and power backups. Spinel Li₄Ti₅O₁₂ has attracted great attention in this field due to the features of "zero stain",capability of quick charge-discharge and long cycling life performance. Meanwhile, layered LiMnO₂ is gradually becoming more widely used as anode material because of its advantages of being environmentally friendly, low cost and high-theoretic specific capacity. However, there are still few reports about layered LiMnO₂ used as anode material of lithium titanate battery. In this thesis, physical properties of Li₄Ti₅O₁₂ prepared by different manufacturers were characterized first, and then we focused on how it affects the electrochemical performance of Li₄Ti₅O₁₂/Li half cell and LiMnO₂/Li₄Ti₅O₁₂ pouch battery, the effects of different separator for the electrochemical performance of LiMnO₂/Li₄Ti₅O₁₂ pouch battery had been discussed as well.According to the XRD and SEM characterization results of material powders, LTO-1 had smaller diameter, but LTO-2 had better dispersibility and homogeneity, which were conducive to exhibiting good electrochemical performance. It was found that LTO-2 electrode shows better rate and cycling performance than LTO-1 electrode measured in a Li₄Ti₅O₁₂/Li half cell, the LTO-2 electrode delivered a discharge capacity of 153.6 and 130.8 mAh·g-1 respectively at 0.2C and 5 C charge-discharge rate while the charge capacity was 153.4 and 114.6 mAh-g-1, the result of the cycling performance showed a initial discharge capability of 151.1 mAh·g-1 which can remain at 149.2 mAh·g-1 and the capacity retention was 98.7% after 100 cycles at 1 C.The tests of pouch battery also showed that the electrochemical performance of LTO-2 material was superior to LTO-1 material. Pouch battery made by LTO-2 material as anode electrode exhibited excellent rate and cycling performance. In four kinds of separator, S-1 separator had the best rate performance with constant current charge capacity accounted relatively high in rate charge and the maximum rate discharge capacity retention; S-2 separator could achieve the capacity of quick charge easily as its charge capacity almost via constant current mode in rate charge performance testing; pouch battery used S-4 separator exhibited the largest actual capacity that was very close to the design capacity; both S-1 and S-3 separator had a good absorption capacity. With the increase of the separator layers, the rate and cycling performance of the pouch battery were degrading, but it had lower defective percentage and few losses of electrolyte in formation stage, at the same time, it's hardness has been improved, which is conducive to assemble batteries.