| Nowdays, with the development of electric vehicles and mobile appliances, the study on secondary batteries has attracted more and more attentions. Lithium ion batteries(LIBs) are considered as the most promising candidates for their high output voltage, high energy density, long cycle performance, no memory effect and fast charge and discharge et al. As one of promising anode materials, spinel lithium titanate(Li4Ti5O12, LTO) shows the stable charge/discharge voltage platforms, no SEI film and lithium dendrite formation and “zero-strain”. But LTO hasn’t been utilized widely as anode material for LIB yet due to its low rate capacity led by from poor electronic conductivity. In this work, firstly we choose one step liquid coprecipitation to synthsis spinel LTO, and then improve its electronic conductivity through carbon coating and metal ion doping by the coprecipitation. Besides, one step liquid coprecipitation and electrospining are adoped to compose Sr Li2Ti6O14 for low charge/discharge voltage platforms.In this work, sucrose is incorporated into LTO as carbon source by one step liquid coprecipitation. The as-prepared LTO/C sample presents much larger surface area(58.79 m2 g-1) relative to the value of pure LTO(2.44 m2 g-1), with a size around 13 nm in average. Besides, its electronic conductivity of 6.56×10-4 S cm-1 is over 4000 higher than the pure one. The composite anode dispiays a distinguished electrochemical charge/discharge performance, especially, quite high rate capability along with a stable cyclability. It delivers the initial discharge specific capacities of 156.7 and 142.1mAh g-1 at 40 C and 60 C respectively, and remains the values of 114.2 and 98.1 mAh g-1 after 200 cycles. Furthermore, a capacity of 132.8 mA h g-1 is delivered even at an 80 C rate and the value of 82.7 mA h g-1 can be maintained after 200 cycles. The ultrafast charge/discharge capability may be attributed to the shorten Li+ transport path in the nanosized composite and the enlarged access area with electrolyte. Additionally, the carbon coating may provide an effective conductive network among the particles promoting charge transfer.For metal ion doping, Zirconium n-butoxide 80% in n-butanol as Zr source is reaction with LTO to synthsis Li4Ti5-xZrxO12 samples. We confirm the Zr ion doping to spinel LTO by calculating the cell parameters of samples from XRD patterns. When charge and discharge at different rates, the Li4Ti5-x ZrxO12 samples show higher discharge specifie capacities than the pure LTO. And the Li4Ti4.97Zr0.03O12 material is the best one among them. It delievers the initial discharge specific capacities of 139.1 mAh g-1 at 20 C, and the value of 117.3 mAh g-1 can be maintained after 200 cycles. Even at 40 C, its first and 200 th cycle’s capacities can reach 106.0 mAh g-1 and 78.4 mAh g-1.Finally, one step liquid coprecipitation and electrospining are adoped to compose SrLi2Ti6O14 anode materials. At 0.1C rate, the charge and discharge voltage platforms of the two electrodes are about 1.4 V, which is lower than the 1.55 V of spinel LTO. |
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