Transcript Memory Effect

Introduction
• A lithium-ion battery (sometimes Li-ion battery or LIB) is a family
of rechargeable battery types in which lithium ions move from the
negative electrode to the positive electrode during discharge, and
back when charging.
Battery History and Basics
 The modern battery was developed by Italian
physicist Alessandro Volta in 1800.
Construction
•The three primary functional components of a lithium-ion
battery are the anode, cathode, and electrolyte. The
anode of a conventional lithium-ion cell is made from
carbon, the cathode is a metal oxide, and the electrolyte is
a lithium salt in an organic solvent.
Formats
•Li-ion cells are available in various formats, which can generally
be divided into four groups:
• Small cylindrical (solid body without terminals, such as those
used in laptop batteries)
• Large cylindrical (solid body with large threaded terminals)
• Pouch (soft, flat body, such as those used in cell phones)
• Prismatic (semi-hard plastic case with large threaded terminals,
often used in vehicles' traction packs)
The Voltaic Pile
Iphone4 and 3 different
 3gs and 4, the main difference is: 4 screen resolution higher than 3g
retina screen for sharper display
4 camera 5 million pixels, and can shoot 720p HD video, and flash.
There is also a front camera, you can video chat (FaceTime).
3gs 3 million pixels, there is no front camera, no flash.
Now 3gs and 4 can multi-task and folder, because Ann is ios4.2.
The common drawback of all the iPhone is: not a long life time, a
typical day down you have to charge, but can not change the
battery, you can not insert the memory card, but users can not
browse the files, only download the application to use.
Charging
• During charging, an external electrical power source (the
charging circuit) applies a higher voltage (but of the same
polarity) than that produced by the battery, forcing the
current to pass in the reverse direction.
Advantages
•Wide variety of shapes and sizes efficiently fitting the
devices they power.
• Much lighter than other energy-equivalent secondary
batteries.
• High open circuit voltage in comparison to aqueous
batteries (such as lead acid, nickel-metal hydride and
nickel-cadmium). This is beneficial because it increases
the amount of power that can be transferred at a lower
current.
• No memory effect.
Disadvantages
•Charging forms deposits inside the electrolyte that inhibit
ion transport. Over time, the cell's capacity diminishes.
The increase in internal resistance reduces the cell's
ability to deliver current.
•High charge levels and elevated temperatures hasten
capacity loss.
Safety requirements
•If overheated or overcharged, Li-ion batteries may suffer
thermal runaway and cell rupture.
Battery types
Nickel-cadmium: (NiCd)



rechargeable,

“memory effect”
Nickel-metal hydride: (NiMH)

rechargeable

no “memory effect”
Lithium-Ion: (Li-Ion)

rechargeable

no “memory effe
Memory Effect
The Memory Effect: (generally) When a battery is
repeatedly recharged before it has discharged more than
half of its power, it will “forget” its original power
capacity.
•
Lithium
•Periodic
Table Symbol: Li
•Atomic Weight: 3 (light!)
•Highly reactive, with a high energy density.
•Used to treat manic-depression because it is particularly
effective at calming a person in a “manic” state.
The Periodic Table

Specifications and design
•Specific energy density ：150 to 250 W.h/kg or 540kj/kg
•Volumetic energy density ：250 to 630 W.h/l or 900 to
1900 J/cm³
•Specific power density: 300 to 1500 W/kg (@ 20 seconds
and 285 W·h/l)
Internal resistance
•The internal resistance of standard (Cobalt) lithium-ion
batteries is high compared to both other rechargeable
chemistries such as nickel-metal hydride and nickelcadmium, and LiFePO4 and lithium-polymer cells.
Conclusion
 Finally, I believe Lithium-Ion Battery is very useful
because its high energy density allows batteries them to
power complex machinery and it also recharge quickly
and hold their charge longer.
Links to References
 http://electronics.howstuffworks.com/battery.htm
 http://www.batteryuniversity.com
 ttp://www.nano.gov/html/research/industry.html

http://everything2.com/e2node/Lithium%2520ion%2520
battery
The End