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ARTICLES IN THE BOOK

  1. AAAA battery
  2. AAA battery
  3. AA battery
  4. A battery
  5. Absorbent glass mat
  6. Alessandro Volta
  7. Alkaline battery
  8. Alkaline fuel cell
  9. Aluminium battery
  10. Ampere
  11. Atomic battery
  12. Backup battery
  13. Baghdad Battery
  14. Batteries
  15. Battery charger
  16. B battery
  17. Bernard S. Baker
  18. Beta-alumina solid electrolyte
  19. Betavoltaics
  20. Bio-nano generator
  21. Blue energy
  22. Bunsen cell
  23. Car battery
  24. C battery
  25. Clark cell
  26. Concentration cell
  27. Coulomb
  28. 2CR5
  29. Daniell cell
  30. Direct borohydride fuel cell
  31. Direct-ethanol fuel cell
  32. Direct methanol fuel cell
  33. Dry cell
  34. Dry pile
  35. Duracell
  36. Duracell Bunny
  37. Earth battery
  38. Electric charge
  39. Electric current
  40. Electricity
  41. Electrochemical cell
  42. Electrochemical potential
  43. Electro-galvanic fuel cell
  44. Electrolysis
  45. Electrolyte
  46. Electrolytic cell
  47. Electromagnetism
  48. Electromotive force
  49. Energizer Bunny
  50. Energy
  51. Energy density
  52. Energy storage
  53. Flashlight
  54. Float charging
  55. Flow Battery
  56. Formic acid fuel cell
  57. Fuel cell
  58. Fuel cell bus trial
  59. Galvanic cell
  60. Gel battery
  61. Grove cell
  62. Half cell
  63. History of the battery
  64. Hybrid vehicle
  65. Lead-acid battery
  66. Leclanché cell
  67. Lemon battery
  68. List of battery sizes
  69. List of battery types
  70. List of fuel cell vehicles
  71. Lithium battery
  72. Lithium ion batteries
  73. Lithium iron phosphate battery
  74. Lithium polymer cell
  75. LR44 battery
  76. Luigi Galvani
  77. Manganese dioxide
  78. Memory effect
  79. Mercury battery
  80. Metal hydride fuel cell
  81. Methane reformer
  82. Methanol reformer
  83. Michael Faraday
  84. Microbial fuel cell
  85. Molten carbonate fuel cell
  86. Molten salt battery
  87. Nickel-cadmium battery
  88. Nickel-iron battery
  89. Nickel metal hydride
  90. Nickel-zinc battery
  91. Open-circuit voltage
  92. Optoelectric nuclear battery
  93. Organic radical battery
  94. Oxyride battery
  95. Panasonic EV Energy Co
  96. Peukert's law
  97. Phosphoric acid fuel cell
  98. Photoelectrochemical cell
  99. Polymer-based battery
  100. Power density
  101. Power management
  102. Power outage
  103. PP3 battery
  104. Primary cell
  105. Prius
  106. Proton exchange membrane
  107. Proton exchange membrane fuel cell
  108. Protonic ceramic fuel cell
  109. Radioisotope piezoelectric generator
  110. Ragone chart
  111. RCR-V3
  112. Rechargeable alkaline battery
  113. Reverse charging
  114. Reversible fuel cell
  115. Searchlight
  116. Secondary cell
  117. Short circuit
  118. Silver-oxide battery
  119. Smart Battery Data
  120. Smart battery system
  121. Sodium-sulfur battery
  122. Solid oxide fuel cell
  123. Super iron battery
  124. Thermionic converter
  125. Trickle charging
  126. Vanadium redox battery
  127. Volt
  128. Voltage
  129. Voltaic pile
  130. Watch battery
  131. Water-activated battery
  132. Weston cell
  133. Wet cell
  134. Zinc-air battery
  135. Zinc-bromine flow battery
  136. Zinc-carbon battery
 



BATTERIES
This article is from:
http://en.wikipedia.org/wiki/Lithium_polymer_cell

All text is available under the terms of the GNU Free Documentation License: http://en.wikipedia.org/wiki/Wikipedia:Text_of_the_GNU_Free_Documentation_License 

Lithium ion polymer battery

From Wikipedia, the free encyclopedia

(Redirected from Lithium polymer cell)

Lithium ion polymer batteries, or more commonly lithium polymer batteries (Abbreviated Li-Poly or LiPo) are rechargeable batteries which have technologically evolved from lithium ion batteries. Ultimately, the lithium salt electrolyte is not held in an organic solvent like in the proven lithium ion design, but in a solid polymer composite such as polyacrylonitrile. There are many advantages of this design over the classic lithium ion design, including the fact that the solid polymer electrolyte is not flammable (unlike the organic solvent that the Li-Ion cell uses). Lithium ion polymer batteries started appearing in consumer electronics around 1996.

Overview

Cells sold today as polymer batteries have a different design from the older lithium ion cells. Unlike lithium ion cylindrical, or prismatic cells, which have a rigid metal case, polymer cells have a flexible, foil-type (polymer laminate) case, but they still contain organic solvent. The main difference between commercial polymer and lithium ion cells is that in the latter cells, the rigid case presses the electrodes and the separator onto each other, whereas in polymer cells this external pressure is not required because the electrode sheets and the separator sheets are laminated onto each other.

Since no metal battery cell casing is needed, the battery can be lighter and it can be specifically shaped to fit the device it will power. Because of the denser packaging without intercell spacing between cylindrical cells and the lack of metal casing, the energy density of Li-Poly batteries is over 20% higher than that of a classical Li-Ion battery and approximately three times better than NiCd and NiMH batteries.

The voltage of a Li-Poly cell varies from about 2.7 V (discharged) to about 4.23 V (fully charged), and Li-Poly cells have to be protected from overcharge by limiting the applied voltage to no more than 4.235 V per cell used in a series combination. Overcharging a Li-Poly battery will likely result in explosion and/or fire. During discharge on load, the load has to be removed as soon as the voltage drops below approximately 3.0 V per cell (used in a series combination), or else the battery will subsequently no longer accept a charge.

Early in its development, lithium polymer technology had problems with internal resistance. Other challenges include longer charge times and slower maximum discharge rates compared to more mature technologies. Li-Po batteries typically require more than an hour for a full charge. Recent design improvements have increased maximum discharge currents from two times to 15 or even 30 times the cell capacity (discharge rate in amps, cell capacity in amp-hours). In March 2005 Toshiba announced a new design offering a much faster (about 1-3 minutes) rate of charge. These cells have yet to reach the market but should have a dramatic effect on the power tool and electric vehicle industries, and a major effect on consumer electronics; especially electrically powered model aircraft.

When compared to the lithium ion battery, Li-Poly had a greater life cycle degradation rate. However, in recent years, manufacturers have been declaring upwards of 500 charge-discharge cycles before the capacity drops to 80% (see Sanyo). Another variant of Li-Poly cells, the "thin film rechargeable lithium battery" has been shown to provide more than 10,000 cycles.

Applications

A compelling advantage of Li-Poly is that manufacturers can shape the battery almost however they please, which can be important to mobile phone manufacturers constantly working on smaller, thinner, and lighter phones. Another advantage of lithium polymer cells over nickel cadmium and nickel metal hydride cells is that the rate of self discharge is much lower.

Li-Poly batteries are also gaining favor in the world of radio-controlled aircraft, where the advantages of both lower weight and greatly increased run times can be sufficient justification for the price. However, lithium polymer-specific chargers are required to avoid fire and explosion. Explosions can also occur if the battery is short circuited as tremendous current would be available for a short time. Radio control enthusiasts take special precautions to ensure their battery leads are properly connected and insulated. Specially designed electronic motor speed controls are used to prevent excessive discharge and subsequent battery damage. This is achieved using a Low Voltage Cut-off (LVC) setting, that is adjusted to maintain cell voltage at (typically) 3v per cell.

Li-poly batteries are also gaining ground in PDAs and laptop computers, such as Apple's MacBook and small digital music devices such as iPods and other MP3 players, as well as portable gaming devices like the Sony PSP or Nintendo's Game Boy Advance SP, where small form factors and energy density outweigh cost considerations.

These batteries may also power the next generation of battery electric vehicles. The cost of an electric car of this type is prohibitive, but proponents argue that with increased production, the cost of Li-Poly batteries will go down.

Canadian company BionX had been supplying electric conversion kits for some time that used brushless motors and Nickel Metal Hydride batteries, but during 2006, they introduced batteries that used Lithium Ion technology. During 2007 Urban Mover introduced the first commercially available Li-Poly powered electric bikes, as opposed to just supplying conversion kits.

Technology

There are currently two commercialized technologies, both lithium-ion-polymer (where "polymer" stands for "polymer electrolyte/separator"). They are called "polymer electrolyte batteries".

The idea is to use an ion-conducting polymer instead of the traditional combination of a microporous separator and a liquid electrolyte. This promises not only better safety, as polymer electrolyte does not burn as easily, but also the possibility to make battery cells very thin, as they don't require pressure applied to "sandwich" cathode+anode together. Polymer electrolyte seals both electrodes together like a glue.

The design is: anode (Li or carbon-Li intercalation compound)/conducting polymer electrolyte-separator/cathode (LiCoO2 or LiMnO4)

Typical reaction:

  • Anode: carbon-Li(x) - xLi+ - xe
  • Separator: Li+ conduction
  • Cathode: Li(1-x)CoO2 + xLi+ + xe

Polymer electrolyte/separator can be real solid polymer (polyethyleneoxide, PEO) plus LiPF6 or other conducting salt plus SiO2 or other filler for better mechanical properties (such systems are not available commercially yet). Some are planning to use metallic Li as the anode, whereas others want to go with the proven safe carbon intercalation anode.

Both currently commercialized technologies use PVdF (a polymer) gelled with conventional solvents and salts, like EC/DMC/DEC etc. The difference between the two technologies is that one (Bellcore/Telcordia technology) uses LiMnO4 as the cathode, and the other, more conventional LiCoO2.

Other, more exotic (although not yet commercially available) Li-polymer batteries use a polymer cathode. For example, Moltech is developing a battery with a plastic conducting carbon-sulfur cathode. However, as of 2005 this technology seems to have problems with self-discharge and manufacturing cost.

Yet another proposal is to use organic sulfur containing compounds for the cathode in combination with an electrically conducting polymer such as polyaniline. This approach promises high power capability (i.e. low internal resistance) and high discharge capacity, but has problems with cycleability and cost.

External links

  • BatteryUniversity.com
  • World's First Electric Powered Paraglider - running on Lipo.
  • A sailplane with auxilary electric power, running on lipos.
  • 2005.11.02 - A123Systems Launches New Higher-Power, Faster Recharging Li-Ion Battery Systems [1]
    2006.05.19 - Hybrid vehicle application note
  • Electrolite - Information pages on LiPo batteries, and how to use.
  • BionX electric bike conversion kits - NiMH and Li-Ion
  • Urban Mover Li-Po powered bikes
Retrieved from "http://en.wikipedia.org/wiki/Lithium_ion_polymer_battery"

 



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