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Unlike primary batteries, rechargeable batteries, once discharged, can be returned to their fully charged state and repeatedly discharged for up to hundreds of cycles. The engineering of a rechargeable system is complex. The technical incubation period is often decades, not years. The key problem lies in the repeatability and safety issues related to the highly energetic materials.
Secondary cells can be charged and discharged many times, making it economic to use a more costly construction. Most rechargeable batteries use an aqueous electrolyte but, nevertheless, the electrolyte solutions such as concentrated potassium hydroxide or sulfuric acid, are still liquid at -40oC.
A comparison of the energy and power densities of conventional rechargeable cells and some advanced technologies demonstrate the progress made in recent years to achieve power and energy densities to satisfy an increasing demand of portable power sources. The advantages and disadvantages of some of these technologies is shown in the following Table.
Cell Type | Advantages | Disadvantages |
well known | low energy density | |
excellent power | D-cell smallest size | |
cheap | ||
well known | energy density | |
excellent power use | memory effect | |
in battery packs | Cd is toxic | |
well known, | corrosion of Zn | |
very cheap | ||
high energy density | cost | |
good shelf life | low cycle life | |
Li/V6O13 | insoluble in organic | low power |
solvents | sloping voltage | |
higher voltage | costly | |
low power | ||
good shelf life, | costly | |
low toxicity | poor power | |
safety, flexibility | poor at <25oC | |
non-toxic | low cycle life | |
high energy density | cost | |
high cycle life | poor shelf life | |
excellent power | expensive | |
capability, reliable |
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