Identifier

etd-04092017-201734

Degree

Master of Science in Mechanical Engineering (MSME)

Department

Mechanical Engineering

Document Type

Thesis

Abstract

Nowadays, rechargeable lithium-ion batteries (LIBs) have been widely used as energy storage devices for portable electronic devices. The increasing demand for their emerging applications in hybrid electric vehicles (HEVs) and electric vehicles (EVs) requires us to develop LIBs with higher energy density and power density. However, both the commercial cathode material (LiCoO2) and anode material (graphite) exhibit low specific capacity and poor rate capability, which severely hinder the practical application of lithium-ion batteries for transportation. This thesis mainly includes four research works on novel design and synthesis of nanostructured electrode materials for advanced lithium-ion batteries. To improve the electrochemical performances of cathode materials Li4Mn5O12, dual doping of Ni and Fe has been applied. It is found that the facile doping strategy can effectively improve both the operating voltage and reversible specific capacity of Li4Mn5O12, demonstrating as a promising high-voltage cathode material for high-energy high-power LIBs. Li-rich transition metal oxides display very high theoretical capacity but suffer from poor cycling stability and rate capability due to its large initial capacity loss and inferior structural stability upon cycling. To solve these problems, we have designed and synthesized a L@S core–shell structure (Li-rich layered-spinel core–shell heterostructure) via evaporation-induced self-assembly (EISA) of ultrafine Li4Mn4.5Ni0.5O12 nanoparticles onto the surface of Li-rich layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 (LMNCO), which demonstrates significantly improved specific capacity, cycling performance and rate capability for application as a cathode in new-generation LIBs compared to pristine LMNCO. In addition to cathode materials, we have synthesized two types of high-performance anode materials for LIBs. A novel structure with Sn nanoparticles well-dispersed in the microspheres of manganese-nickel-cobalt carbonate MNCCO3 (Sn@MNCCO3) has been prepared by using a facile one-step solvothermal process. We also synthesized sandwich-like, porous nitrogen-doped carbons by using zeolitic imidazolate framework (ZIF-8) as a template and carbon precursor.

Date

2017

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Wang, Ying

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