Doctoral Dissertations

Date of Award

12-2021

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Chemistry

Major Professor

Sheng Dai

Committee Members

Bhavya Sharma, Ampofo K. Darko, Bin Hu

Abstract

Renewable energy storage systems are regarded as the solution to the environmental and energy crises caused by the burning of fossil fuels in vehicles. Unfortunately, owning to the limits to the electrochemical performance of the current anode materials, lithium-ion batteries [LIBs] are still lacking strength in the charging rate-capability and thereby cannot fulfill future application requirements in electrical vehicles [EVs].

Particularly, graphite with a high theoretical specific capacity of 372 mAh/g is unsuitable for EVs due to the safety concerns of passivating solid-electrolyte interphase [SEI] resulted from the low operation potential of 0.1 V versus Li/Li+. The other common anode material is Li4Ti5O12, which exhibits high operating potential of 1.55 V vs Li/Li+, excellent rate-capability and zero-strain property together with superior rate capability and excellent cycle life. However, the theoretical specific capacity of Li4Ti5O12 is only 175 mAh/g, dramatically impeding the practical application in electric vehicles. Therefore, developing new anode materials with excellent fast-rechargeability and high theoretical specific capacity is an urgent research topic.

Recently, transition metal oxides [TMOs], possessing high theoretical capacities and operation voltages, are considered to be promising anode materials for EVs. However, their inherent low electrical conductivities and Li+ diffusivities still challenge their future usage in EVs. Scientists discovered that nano-scaled TMOs can improve the electrochemical kinetics, while the widely used soft and hard template preparation methods can cause considerable environmental pollution (the huge CO2 emission from block-polymer burning and the usage of highly toxic etching agents, respectively). Therefore, developing a new strategy to synthesize nano-scaled TMOs is highly desirable.

Herein, ionothermal syntheses, employing ionic liquids as the solvents and/or templates in the preparations to form nanoporous materials, are novelly applied to develop several types of new nanoporous TMO materials. Moreover, unlike the traditional synthesis methods discussed above, the used ionic liquids can be easily recycled to circumvent the potential environmental concerns. More importantly, the prepared TMO materials successfully deliver superb electrochemical performance, which establishes the promising potential of ionothermal syntheses in the preparation of high-performance anode materials and shines new light on the development of fast-rechargeable LIBs in EVs.

Download
Files over 3MB may be slow to open. For best results, right-click and select "save as..."

Share

COinS