Synthesis And Characterization Of Pivotal Materials For Advanced Lithium Ion Batteries

Abstract:Lithium ion batteries are important energy storage devices, which could be employed in electronic products, electric vehicles and smart gird electric storage stations. The commercial lithium ion batteries still can not meet the requirements under special environments, such as super higher energy densities, super stability and high-temperature proof lithium ion batteries. Herein, Li1.3Al0.3Ti1.7(PO4)3based lithium ion conductors that can be utilized in elevated temperature and the MoO2based anode with excellent cycle performance are investigated in present thesis. In details, this work includes the following content.(1) The Li1.3Al0.3Ti1.7(PO4)3(LATP) lithium-ion conductive materials were prepared by a wet chemical method which is polymerized by polyvinyl alcohol. The LATP-xLP (x=0,0.01,0.03,0.05) ceramics were prepared by using Li4P2O7(LP) as sintering additive. The results show that the LP sintering additive can decrease the sintering temperature of LATP about150℃and improve the ionic conductivity. The analysis of the DC and AC conductivities of the LATP-0.03LP ceramic revealed that the ionic conductivity is99.5%of the total conductivity.(2) A facile and template-free one-pot strategy is applied to synthesize MoO2nanostructured particles via a hydrothermal methodology. The as-annealed MoO2nanostructured particles exhibit interconnecting features. These factors that could influence the properties of MoO2anode are investigated and the fact is that microstructure have an important impact on the electrochemical performance of MoO2electrode. Also, microstructure investigations on products after full-lithiation are analyzed, the results confirm the lithium ion uptake/removal mechanism, which is different from the cycling behavior of micro size MoO2materials, in nano MoO2electrode.(3) MoO2@C nanostructured particles with carbon coationg are synthesized via a hydrothermal methodology. Evaluated as an anode in lithium ion batteries, the lithium storage performance of MoO2@C electrode is excellent, which can be attributable to the ultra fine and carbon coating structure. This special structure can drastically improve the kinetic feasibility. With the help of transmission electron microscope, we investigate the cycle behavior of MoO2@C electrode in the first cycle. The results show that, the MoO2@C electrode undergoes a conversion reaction after an addition type reaction. More specifically, the MoO2phase is transferred into an intermediate phase like Li0.98MoO2before decomposing into metallic Mo in the lithium uptake process. In return, the Mo oxidizes to the high valence Lio.98Mo02phase and then remove Li and restore to nano MoO2phase upon forthcoming lithium removal process.