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Study on functional additives to improve electrochemical performances of overlithiated layered oxides

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Title
Study on functional additives to improve electrochemical performances of overlithiated layered oxides
Author
Park, Inbok
Advisor
Choi, Nam-Soon
Keywords
High voltage cathode; Li-rich layered oxides; OLO; cathode additive; electrolyte additive
Issue Date
2016-02
Publisher
Graduate School of UNIST
Abstract
The lithium ion battery is introduced for small electronic appliances at first. After several decades, sustainable energy sources are required to replace existing fossil fuel. One of renewable energy sources, electricity is suggested as candidates for available energy sources because it has no air pollution and high efficiency. Due to this benefits, it is considered to replace internal combustion engine of car and adapt to energy storage system (ESS). However, large scale batteries used in ESS or vehicle which need high capacity and high voltage is not able to be realized with existing cathode. The lithium cobalt oxide (LCO) is used for common lithium ion batteries. It is viable option for small appliances because it doesn’t require high spec. The structure of LCO is being unstable when it release more than half of its lithium sources. Also, it cannot bear high voltage circumstances above 4.2V because it react with electrolyte easily. Many researchers attempt to solve this problem. They use coating on cathode surface to protect it from side reactions and structural changes at high voltages instead of changing cathode. It has two type. One is physical method directly spraying coating materials and the other is chemical method which use electrochemical reaction. The chemical method is modifying solid electrolyte interphase (SEI) layer by additives. Those additives less than 5% of total electrolyte solution make ideal SEI layer which protects cathode material from side reactions with bulk electrolyte and selectively transfers lithium ions. Furthermore, they search cathode materials fit to industrial requirements. It is necessary to develop new cathode because existing electrode has limit even we use coating method. The overlithiated layered oxides (OLO), lithium rich layered oxides, is one of promising candidates for high voltage, high capacity cathodes. It is denoted as Li1+xM1-xO2 (0
Description
Department of Energy Engineering(Battery Science and Technology)
URI
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