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Investigation on the Modification and Electrochemical Performance of Li4Ti5O12 Anode for Lithium Ion Battery

Author: YuZiJia
Tutor: WangRongShun
School: Northeast Normal University
Course: Physical and chemical
Keywords: Li-ion battery anode materials Li4Ti5O12 modification electrical conductivity
CLC: TM912
Type: Master's thesis
Year: 2011
Downloads: 292
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Abstract


In recent years, lithium ion batteries （LIB） have been of extensive use for electric vehicles and hybrid electric vehicles with the potential to save oil and to decrease exhaust emissions. Although, commercially available LIB adopting carbon or graphite as anode instead of metallic lithium still possess potential threats against safety. Conventional carbon materials are almost close to 0 V at the end of Li insertion, as a result, dendritic lithium plates on the surface of carbonaceous materials during the fast-charge or over-charge process, which easily induce short circuit and explosion inside batteries. In order to solve this limit of current LIB technology, it is necessary to develop an alternative anode material with higher Li-insertion potential.Spinel Li4Ti5O12 has become a promising anode material for LIB application. Compared with the typical commercial carbon anodes, Li4Ti5O12 with a higher Li-insertion process operates at about 1.55 V （vs. Li/Li+）, which can stop the reduction of electrolyte on the surface of the electrode. Furthermore, as a zero-strain insertion material, Li4Ti5O12 possesses excellent reversibility, structural stability and excellent lithium ion mobility in the charge–discharge process. Hence, it exhibits batter cycling and safety performances. Despite these advantages, the LTO shows poor electronic conductivity, consequently limiting its commercial application.To improve the low electrical conductivity of Li4Ti5O12, our research groups made some new efforts by synthesis of carbon coating and metallic ions doping Li4Ti5O12.1. Li4Ti5O12/C has been synthesized with water soluble polymer polyvinyl alcohol （PVA） as carbon source by high-temperature solid-state method in an inert atmosphere. XRD analysis showed that the presence of PVA reduced the lattice parameter of Li4Ti5O12 and did not affect the host crystal structure of Li4Ti5O12. SEM results showed that Li4Ti5O12/C particles were small and round .At 0.5C rate, the initial discharge capacity of the Li4Ti5O12/C was 141mAh/g,after 120 cycles, it was 104.9 mAh/g, low capacity retention was obtained.2. Li4Ti5O12/C has been synthesized with water soluble polymer polyethylene glycol （PEG） as carbon source by high-temperature solid-state method in an inert atmosphere. XRD analysis showed that the presence of PEG reduced the lattice parameter of Li4Ti5O12 and did not affect the host crystal structure of Li4Ti5O12. The SEM micrograph of Li4Ti5O12/C showed that the average particle size were round about 400nm and had wide particle distribution. At 2C rate, the initial discharge capacity of the Li4Ti5O12/C was 128.2 mAh/g, after 450 cycles, it was 95.3 mAh/g, the capacity retention was only 74.3%. At 1C rate, the initial discharge capacity of the Li4Ti5O12/C was 136 mAh/g, after 70 cycles, it was 125.1 mAh/g, the higher capacity retention, 92%, was obtained.3. Composite material Li3.9Al0.1Ti5O12 has been synthesized by sol-gel process. The SEM micrograph of Li3.9Al0.1Ti5O12 showed that the particles easily agglomerated by high-temperature calcination. There is no impurity peak in XRD pattern which is accorded with the standard pattern （No.26-1198）.4. Composite material Li4Ti4.9V0.1O12 has been synthesized by high-energy ball-milling auxiliary high-temperature solid-state method in an inert atmosphere. XRD analysis showed that the doping of V5+ reduced the parameter of Li4Ti5O12 and did not affect the host crystal structure of Li4Ti5O12. The SEM image of Li4Ti4.9V0.1O12 showed that the average particle size was under 350nm. The doping of V5+ has largely increased the conductivity （both the lithium ion and electron） of Li4Ti5O12, which improved its electrochemical performance.

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CLC: > Industrial Technology > Electrotechnical > Independent power supply technology (direct power) > Battery
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