Li4Ti5O12 coated graphite anodes with piperidinium-based hybrid electrolytes for lithium ion batteries

The electrochemical performances of the 2 wt% and 5 wt% Li4Ti5O12 coated carbon microbeads (CMB) composites in the piperidinium-based hybrid electrolytes are investigated. Particularly, the interfacial properties and crystal structures of cycled LTO-CMB electrodes are explored by means of scanning electron microscopy, electrochemical impedance and X-ray diffraction. It is found that, the Li4Ti5O12 coating can help to reduce the interfacial reactions and decrease the initial irreversible capacity. At 0.05 C, the initial coulombic efficiency are improved from 62.7% of pristine CMB to 63.5% of 2% LTO-CMB and 72.5% of 5% LTO-CMB respectively. However, due to its incomplete surface coating, the discharge capacities of 2% LTO-CMB vary with cycle number as an undulate shape, and show a large capacity loss. By contrast, the cycled 5% LTO-CMB covered by a stable and dense granular surface film, shows better rate capability and cycle life. The discharge capacity can always maintain about 290 mAh g−1 during the first 22 cycles at 0.1 C. Even at 1 C or 2 C, the reversible capacity is about 50--100 mAh g−1 higher than the unmodified CMB.