Li-ion Lithium Ion Battery Technology
- details about Li-ion, lithium ion battery technology giving an overview of what they are, and how they work.
Lithium ion, or Li-ion batteries are now being widely used for applications such as powering laptop computers, mobile phones cameras and many more devices. The high energy density that Li-ion batteries provide, enables the electronic devices they power to be recharged less frequently. Also Li-ion batteries are comparatively light when compared to other forms of rechargeable cells and batteries.
In view of their convenience, Li-ion, lithium ion batteries are widely used and there are a number of different manufacturers for these batteries. Accordingly costs have fallen from their original high levels, although Li-ion batteries are still expensive.
Growth & development of Li-Ion batteries
Lithium battery technology has taken many years to develop. It offers distinct advantages over other older rechargeable battery technologies such as Nickel cadmium and Nickel Metal Hydride. Despite the advantages of Lithium ion it has taken years to perfect and enable it to reach a maturity level where it could be widely used. Now it is used in many areas and its use has enabled may technologies such as mobile phones, laptops and other items of everyday use to move forwards.
The idea for lithium ion battery technology was first proposed in the 1970s by M Whittingham who used titanium sulphide and lithium metal as the electrodes for his cell.
Work was undertaken at the University of Pennsylvania to enable a graphite electode to be used with lithium ions in the electrode. This was a major advance, although it was not take up immediately by other advances in lithium ion technology.
However other techniques associated with charging needed to be solved before a viable cell could be made. In 1979 J Goodenough demonstrated a rechargeable lithium ion cell using Lithium Cobalt Oxide for the positive electrode and lithium as the negative one.
The next stages in producing a workable production cell were to be able to enable recharging action with lithium in graphite. This was achieved by Rachid Yazami in 1979. It then took until 1985 before a rechargeable lithium ion cell was developed that could be manufactured in large scale production quantities. Akira Yoshino used carbonaceous material into which would accept lithium ions as one electrode, and lithium cobalt oxide, LiCoO2 as the other. The use of Lithium Cobalt Oxide was important because it is stable in air unlike lithium itself, and this made this cell structure more stable chemically and far less dangerous.
Lithium ion, Li-ion battery basics
Although there are various different forms of lithium ion battery technology, there are several common elements in common.
A lithium ion battery, or cell of whatever form has three main constituents:
The main charge carrier is lithium ions - hence the name for the battery technology. Both the anode and cathode are made from materials into which and from which the lithium ions can flow.
During the overall cycle there are two processes associated with movement of the lithium ions:
- Intercalation : The process where the lithium ions in the lithium ion battery are inserted into the electrode is called intercalation.
- Deintercalation : This is the reverse process and occurs when lithium ions are extracted from the electrode, i.e. they move back out.
Lithium ion battery variants
Although lithium ion batteries are generally referred to by their generic name, there are actually several different types of lithium ion battery. Even though they have many similar characteristics, each has its own and is optimum for different applications.
|Lithium Ion Battery Technologies Summary|
|Lithium Cobalt||LiCoO2||LCO||High capacity||Cellphones, laptops,cameras|
|Lithium Manganese Oxide||LiMn2O4||LMO||Safety, but lower capacity||Power tools, medical, hobbyist|
|Lithium Iron Phosphate||LiFePO4||LFP||Safety, but lower capacity||Power tools, medical, hobbyist|
|Lithium Nickel Manganese Cobalt Oxide||LiNiMnCoO2||NMC||Safety, but lower capacity||Power tools, medical, hobbyist|
|Lithium Nickel Cobalt Aluminium Oxide||LiNiCoAlO2||NCA||Electric vehicles and grid storage|
|Lithium Titanate||Li4Ti5O12||LTO||Electric vehicles and grid storage|
More details of the various variants of lithium ion battery can be found later in this tutorial.
Guidelines for using Li-ion batteries
Lithium ion batteries or Li-ion batteries can be relatively expensive. It therefore pays to follow simple guidelines that can help ensure the maximum life is obtained from them.
- Lithium-ion batteries should be charged before the battery is completely discharged.
- Lithium-ion batteries should not be frequently fully discharged and recharged ("deep-cycled") like Ni-Cd batteries. However this may be needed occasionally to recalibrate any associated "fuel gauge" circuitry used to monitor the state of charge, control charging, etc.
- Li-ion batteries should never be depleted to below their minimum voltage, 2.4 V to 3.0 V per cell.
- If a Li-ion battery is not to be used for an extended period of time it should ideally be brought to a charge level of between about 40% and 60% of full charge.
- Li-ion batteries should be kept cool. By keeping them cool, possibly in a refrigerator, the ageing process becomes slower. As a result, Li-ion batteries should not be kept in cars on sunny days as the temperatures rise significantly.
- Li-ion batteries should not be exposed to very low temperatures - most lithium-ion battery electrolytes freeze at approximately 40°C. This may preclude them from some applications where equipment needs powering in extremes of temperature.
- Li-ion batteries should be bought only when needed, because the aging process begins as soon as the battery is manufactured
Li-ion batteries and cells or li-ion batteries and cells are now in widespread use. They have taken a position of dominance in the rechargeable battery market and as a result many mobile phones, laptop computers and cameras, etc use them. Although there are many new battery developments taking place, lithium ion batteries, li-ion batteries will remain one of the main types of battery for many years to come.
By Ian Poole
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