 Lithium-ion (Li-ion) batteries are comprised of cells that employ lithium intercalation compounds as the positive and negative materials. As a battery is cycled, lithium ions (Li+) exchange between the positive and negative electrodes. They are also referred to as rockingchair batteries as the lithium ions "rock" back and forth between the positive and negative electrodes as the cell is charged and discharged. The positive electrode material is typically a metal oxide with a layered structure, such as lithium cobalt oxide (LiCo02), or a material with a tunneled structure, such as lithium manganese oxide (LiMn20 4), on a current collector of aluminum foil. The negative electrode material is typically a graphitic carbon, also a layered material, on a copper current collector. In the charge/ discharge process, lithium ions are inserted or extracted from interstitial space between atomic layers within the active materials.
The first batteries to be marketed, and the majority of those currently available, utilize LiCo02 as the positive electrode material. Lithium cobalt oxide offers good electrical performance, is easily prepared, has good safety properties, and is relatively insensitive to process variation and moisture. More recently lower cost or higher performance materials, such as LiMn20 4 or lithium nickel cobalt oxide (LiNi l _ xCox0 2), have been introduced, permitting development of cells and batteries with improved performance. The batteries that were first commercialized employed cells with coke negative electrode materials. As improved graphites became available, the industry shifted to graphitic carbons as negative electrode materials as they offer higher specific capacity with improved cycle life and rate capability. The Li-ion battery market has grown in a decade from an R&D interest to sales of over 400 million units in 1999. Market value at the OEM level was estimated to be $1.86 billion in 2000. 1 By 2005, the market is expected to grow to over 1.1 billion units with value of over $4 billion (¥455 billion),2 while the average unit price is expected to fall 46% from 1999 to 2005. Market interest in this cost-effective, high performance, and safe technology has driven spectacular growth, as illustrated in Fig. 35.1. This technology has rapidly become the standard power source in a broad array of markets, and battery performance continues to improve as Li-ion batteries are applied to an increasingly diverse range of applications.
To meet market demand, an array of designs has been developed, including spiral wound cylindrical, wound prismatic and fiat plate prismatic designs in small (0.1 Ah) to large (160 Ah) sizes. Applications now addressed with Li-ion batteries include consumer electronics, such as cell phones, laptop computers, and personal data assistants, as well as military electronics, including radios, mine detectors and thermal weapons sights. Anticipated applications include aircraft, space craft, satellites, and electric or hybrid electric vehicles. 
Li-ion Battery Advantages & Disadvantages: The major advantages and disadvantages of Li-ion batteries, relative to other types of batteries, are summarized in Table below. The high specific energy ( ~ 150 Wh/kg) and energy density ( ~ 400 Wh/L) of commercial products makes them attractive for weight or volume sensitive applications. Li-ion batteries offer a low self-discharge rate (2% to 8% per month) long cycle life (greater than 1000 cycles) and a broad temperature range of operation (charge at -20°C to 60°C, discharge at -40°C to 6S°C), enabling their use in a wide variety of applications. A wide array of sizes and shapes is now available from a variety of manufacturers. Single cells typically operate in the range of 2.5 to 4.2 V, approximately three times that of Ni-Cd or Ni-MH cells, and thus require fewer cells for a battery of a given voltage. Li-ion batteries can offer high rate capability. Discharge at 5C continuous, or 25C pulse, has been demonstrated. The combination of these qualities within a cost effective, package has enabled diverse application of the technology. Advantages & Disadvantages of Li-ion battery
| | Advantages | Disadvantages | | Sealed cells; no maintenance required | Moderate initial cost | | Long cycle life | Degrades at high temperature | | Broad temperature range of operation | Need for protective circuitry | | Long shelf life | Capacity loss or thermal runaway when over-charged. | | Low self-discharge rate | Venting and possible thermal runaway when crushed | | Rapid charge capability | Cylindrical designs typically offer lower power density than Ni-Cd or Ni-Mh | | High rate and high power discharge capability | | | High coulombic and energy efficiency | | | High specific energy and energy density | | | No memory effect | |
A disadvantage of Li-ion batteries is that they degrade when discharged below 2 V and may vent when overcharged as they do not have a chemical mechanism to manage overcharge, unlike aqueous cell chemistries. Li-ion batteries typically employ management circuitry and mechanical disconnect devices to provide protection from over-discharge, overcharge or over temperature conditions. Another disadvantage of Li-ion products is that they permanently lose capacity at elevated temperatures (65°C), albeit at a lower rate than most Ni-Cd or Ni-MH products.
Source: Needbattery.com
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Cell vs. Battery
