Li-Ion Batteries Essay

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Pages: 42



Abstract Technology is striving to keep up with today's society. We continuously require smaller, lighter and more autonomous equipment. The rechargeable lithium ion battery is the most important factor in determining the rate of development of modern day consumer electronics. Perhaps not surprisingly the transport of lithium ions (Li+) remains the preferred technology to achieve this. As a result and for the purpose of this review, only the Li-ion battery (rather than the Li-metal battery) will be considered. This contribution is interested in presenting the issues and challenges this technology has and will encounter. Given the huge volume of literature published on this
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Figure 3: Schematic of the discharge in a hypothetical Li-ion cell27.

Therefore, during discharge the negative electrode, LixCnDm acts as a source of lithium and the positive electrode AzBy performs as a Li+ ion sink, and the cell reaction can be written as27: discharge
LixCnDm(s) + AzBy(s) ↔ CnDm(s) +LixAzBy(s) charge

This report will show that this is not always the case, and it will describe in some detail the materials used, past and present and future materials for each of the batteries components.
As an example Figure 4 shows a schematic of a typical rechargeable lithium-ion battery used today.

Figure 4: Schematic of a rechargeable lithium-ion battery48

Positive Electrodes The most widely used cathode material is LiCoO2. It is a stable material under cycling and easily prepared at high quality. LiCoO2 has a well-ordered layered crystal structure which favours fast and reversible lithium intercalation (Figure 5). However, is it very expensive owing to cobalt's rarity, toxic to humans and has relatively low theoretical capacity (~ 130 mA h g-1) .

Figure 5: Layered, spinel and olivine structures for positive electrode materials for lithium ion batteries5. Besides the low capacity discharge, LiCoO2 is thermally