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Home  >  Articles  >  LiFePO4 battery

Lithium Ion Battery

Lithium-ion battery

FromWikipedia,the free encyclopedia

Not to beconfusedwith Lithium battery or Lithium-ionpolymerbattery.

Batteryspecifications


Lithium-ion batteryofVarta, Museum Autovision, Altlußheim, Germany

Energy/weight

100-160Wh/kg[1]

Energy/size

250-360Wh/L[1]

Power/weight

~250-~340W/kg[2] 1700 W/kg (lab)[3]

Charge/discharge efficiency

80-90%[4]

Energy/consumer-price

2.8-5 Wh/US$[5]

Self-dischargerate

5%-10%/month

Timedurability

(24-36)months

Cycledurability

~1200 cycles[citationneeded]

NominalCellVoltage

3.6 /3.7V



Lithium-ionbatteries(sometimes abbreviated Li-ion batteries) are a typeofrechargeablebattery inwhich a lithium ion moves between the anode and cathode. The lithium ion moves from the anode to the cathode during discharge and in reverse, from the cathode to the anode, when charging.

Lithium ionbatteriesare common in consumerelectronics. They are one of the most popular typesof battery for portable electronics, with one of the bestenergy-to-weight ratios, no memory effect, and a slow loss of charge when not in use. In addition to uses for consumer electronics, lithium-ion batteries are growing in popularity for defense, automotive, and aerospace applications due to their high energy density. However certain kinds of mistreatment may cause Li-ion batteries to explode.

The threeprimaryfunctional components of a lithium ion battery aretheanode, cathode, and electrolyte, for which a variety of materials may be used. Commercially, the most popular material for the anode is graphite. The cathode is generally one of three materials: a layered oxide, such as lithiumcobaltoxide, onebased on a polyanion, such as lithiumironphosphate,or a spinel, such as lithium manganese oxide, although materials such as TiS2 (titanium disulfide) were originally used.[6] Depending on the choice of material for the anode, cathode, and electrolyte the voltage, capacity, life, and safety of a lithium ion battery can change dramatically. Lithium ion batteries are not to be confused with lithium batteries, the key difference being that lithium batteries are primary batteries containing metallic lithium while lithium-ion batteries are secondary batteries containing an intercalationanode material.

Contents

[hide]

1History

2 Electrochemistry

2.1 Cathodes

2.2 Electrolytes

3 Advantages and disadvantages

3.1 Advantages

3.2 Disadvantages of traditional Li-ion technology

3.2.1 Shelf life

3.2.2 High internal resistance

3.2.3 Protection circuits required

3.2.4 Safety features

3.2.5 Product recalls

4 Specifications and design

5 Improvements to Lithium Ion Battery Technology

5.1 Overview

5.2 Manganese Spinel Cathodes

5.3 Lithium Iron Phosphate Cathode With Traditional Anode

5.4 High Power Cathode using Lithium Nickel Manganese Cobalt (NMC)

5.5 Traditional Cathode With Lithium Titanate Anode

5.6 Combined anode and cathode developments

6 Research claims

7 Guidelines for prolonging Li-ion battery life

7.1 Storage temperature and charge

7.2 Prolonging Life in Multiple Cells Through Cell Balancing

8Safety

9 Restrictions on transportation

10Uses

11 See also

12 References

13 External links



 [edit] History

Lithium ionbatterieswere first proposed by M.S.Whittingham (Binghamton University), then at Exxon, in the 1970s.[7]Whittinghamused titanium(II) sulfide as the cathode and lithium metal as the anode.

Theelectrochemicalproperties of the lithium intercalation in graphitewere firstdiscovered in 1982 by Rajeeva R. Agarwal and J. RobertSelman atthe Illinois Institute of Technology. They obtained theactivity oflithium in graphite and showed the diffusion of lithiumwas rapidand reversible in essence proving itsre-chargeability.[8]

Lithium batteriesinwhich the anode is made from metallic lithium pose severesafetyissues. As a result, lithium-ion batteries were developed inwhichthe anode, like the cathode, is made of a materialcontaininglithium ions. Lithium-ion batteries came into realitywhenBell Labs developed a workable graphite anode[9] to provide an alternative to the (metallic lithium anode) lithium battery. Following groundbreaking cathode research by a team led by John Goodenough[10], the first commercial lithium-ion battery was released by Sony in 1991. The cells used layered oxide chemistry, specifically lithiumcobaltoxide. These batteries revolutionizedconsumerelectronics.

In 1983,MichaelThackeray, John Goodenough, and coworkersidentifiedmanganese spinel as a cathode material.[11] Spinel showed great promise, since it is a low-cost material, has good electronic and lithium ion conductivity, and possesses a three-dimensional structure which gives it good structural stability. Although pure manganese spinel fades with cycling, this can be overcome with additional chemical modification of the material.[12] Manganese spinel is currently used in commercial cells.[13]

In1989,Arumugam Manthiram and John Goodenough of the UniversityofTexas at Austin showed that cathodes containing polyanions, eg. sulfates, produce higher voltage than oxides due to the inductive effect of the polyanion.[14]

In late1996,Padhi, Goodenough and coworkers identified the lithiumironphosphate (LiFePO4) and other phospho-olivines (lithium metal phosphates with olivine-structure) as cathode material for lithium ion batteries.[15]Owing to its tremendous superiority over other cathode materials in terms of cost, safety, stability and performance, LiFePO4 is currently being used or developed for most lithium-ion batteries to power portable devices such as laptop computers and power tools. LiFePO4 is most suitable for large batteries for electric automobiles and other energy storage applications such as load saving, where safety is of utmost importance.

In 2002,Yet-MingChiang and his group at MIT published a paper in which they showed a dramatic improvement in the performance of Li batteries by boosting the material's conductivity by doping it with aluminium, niobium and zirconium, though at the time, the exact mechanism causing the increase became the subject of a heated debate.[16]

In 2004, Chiangagainincreased performance by utilizing iron-phosphate particleslessthan 100 nanometres across. This miniaturized the particledensityby almost 100 fold, increased the surface area of theelectrode andimproved the battery's ability to store and deliverenergy.Commercialization of the iron-phosphate technology led toacompetitive market and a patent-infringement battle betweenChiangand Goodenough, two of the leading developers ofthetechnology.[16]

[edit] Electrochemistry

The threeparticipantsin the electrochemical reactions in a lithium ionbattery arethe anode, cathode, and electrolyte.

Both the anodeandcathode are materials into which and from which lithiumcanmigrate. The process of lithium moving into the anode or cathodeisreferred to as insertion (or intercalation), and thereverseprocess, in which lithium moves out of the anode or cathodeisreferred to as extraction (or deintercalation). When acellis discharging, the lithium is extracted from the anode and inserted into the cathode. When the cell is charging, the reverse process occurs: lithium is extracted from the cathode and inserted into the anode.

The negative(duringdischarge) electrode (anode) of a conventional Li-ion cell is made from carbon, the positive (during discharge) electrode (cathode) is a metal oxide,and the electrolyte is a lithium salt in an organic solvent.[17]

Useful work canonlybe extracted if electrons flow through an externalcircuit.Therefore the half reactions are enlightening. Thefollowingequations are written in units of moles, making itpossible to usethe coefficient x. The cathode half reaction (withcharging beingforwards) is: [18]

 

The anodehalfreaction is:

 

The overallreactionhas limits. Overdischarge will supersaturate lithium cobaltoxide,leading to the production of lithiumoxide,[19]possibly by the following irreversible reaction:

 

Overcharge up to5.2Vleads to the synthesis of cobalt(IV) oxide, as evidencedbyx-ray diffraction[20]

 

In alithium-ionbattery the lithium ions are transported to and from thecathode oranode, with the transition metal, Co, in LixCoO2 being oxidized from Co3+ to Co4+during charging, and reduced from Co4+ to Co3+ duringdischarge.

[edit] Cathodes

CathodeMaterial

AverageVoltage

GravimetricCapacity

LiCoO2

3.7V

140mAh/g

LiMn2O4

4.0V

100mAh/g

LiFePO4

3.3V

150mAh/g

Li2FePO4F

3.6V

115mAh/g



See uranium trioxide for some details of how the cathode works. While uranium oxides are not used in commercially made batteries, the way in which uranium oxides can reversibly insert cations is the same as the way in which the cathode in many lithium-ion cells work.[citationneeded]

[edit] Electrolytes

The cellvoltagesabove are larger than the potential at whichaqueoussolutions electrolyze. Therefore, nonaqueous solutions are used.

Liquid electrolytes in Li-ion batteries consist of lithium salts, such as LiPF6, LiBF4,or LiClO4, in an organic solvent, such as ether. A liquid electrolyte conducts Li ions, acting as a carrier between the cathode and the anode when a battery passes an electric current through an external circuit. Typical conductivities of liquid electrolyte at room temperature (20 oC) are in the range of 10 mS/cm, increasing by approximately 30-40% at 40 oC and decreasing by a slightly smaller amount at 0 oC.[21]

Unfortunately,organicsolvents are easily decomposed on anodes during charging. However, when appropriate organic solvents are used as the electrolyte, the solvent is decomposed and forms a solid layer called the solid electrolyte interphase (SEI)[22] at first charge that is electrically insulating yet sufficiently conductive to lithium ions. The interphase prevents decomposition of the electrolyte after the second charge. For example, ethylenecarbonate is decomposed at a relatively highvoltage, 0.7 V vs. Li, and forms a dense and stableinterface.[citationneeded]

[edit] Advantages and disadvantages

[edit] Advantages

Lithium-ionbatteries can be formed into a widevariety of shapes and sizes soas to efficiently fill availablespace in the devices theypower.

Li-ion batteriesarelighter than other equivalent secondarybatteries—often much lighter. The energy is stored in these batteriesthrough the movement of lithium ions. However, the bulk of the electrodes are effectively "housing" for the ions and add weight, and in addition "dead weight" from the electrolyte, current collectors, casing, electronics and conductivity additives reduce the charge per unit mass to little more than that of other rechargeable batteries. A key advantage of using Li-ion chemistry is the high opencircuitvoltage that can be obtained in comparison to aqueous batteries (such as lead acid, nickel metal hydride and nickel cadmium).[citationneeded]

Li-ion batteriesdonot suffer from the memory effect. They also have a low self-discharge rate of approximately 5% per month, compared with over 30% per month in common nickelmetalhydride batteries (Low self-dischargeNiMHbatteries have much lower values, around 1.25% per month) and 10% per month in nickel cadmiumbatteries.

According toonemanufacturer, Li-ion cells (and, accordingly, "dumb"Li-ionbatteries) do not have any self-discharge in the usual meaning of this word.[18]What looks like a self-discharge in these batteries is a permanent loss of capacity, described in more detail below. On the other hand, "smart" Li-ion batteries do self-discharge, due to the small constant drain of the built-in voltage monitoring circuit. This drain is the most important source of self-discharge in these batteries.

[edit] Disadvantages of traditional Li-ion technology

 

This sectionneedsadditional citationsfor verification. Please help improve this article by adding reliablereferences (ideally, using inlinecitations).Unsourced material may be challenged and removed. (October 2007)



[edit] Shelf life

A unique drawbackofthe Li-ion battery is that its service life is dependent upon aging (shelf life). From time of manufacturing, regardless of whether it was charged or the number of charge/discharge cycles, the battery will decline slowly and predictably in "capacity". This means an older battery will not last as long as a new battery due solely to its age, unlike other batteries. This is due to an increase in internal resistance, which affects its ability to deliver current, thus the problem is more pronounced in high-current applications than low. This drawback is not widely published.[23] However, as this capacity decreases over time, the time required to charge it also decreases proportionally. Also, high charge levels and elevated temperatures hasten permanent capacity loss for Lithium ion batteries.[24] This heat is caused by the traditional carbon anode, which has been replaced with good results by Lithium titanate. Lithium titanate has been experimentally shown to drastically reduce the degenerative effects associated with charging including expansion and other factors.[25]See "Improvements of lithium Ion technology" below.

At a 100%chargelevel, a typical Li-ion laptop battery that is full most of the time at 25 °C or 77 °F will irreversibly lose approximately 20% capacity per year. However, a battery in a poorly ventilated laptop may be subject to a prolonged exposure to much higher temperatures, which will significantly shorten its life. Different storage temperatures produce different loss results: 6% loss at 0 °C (32 °F), 20% at 25 °C (77 °F), and 35% at 40 °C (104 °F). When stored at 40%–60% charge level, the capacity loss is reduced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively.[26]

[edit] High internal resistance

The internalresistance of lithium-ion batteries is highcompared to other rechargeable chemistries such as nickel-metalhydride and nickel-cadmium. The internal resistance of a typical lithium-ion cell isaround 320 mOhm when new, compared to less than 100 mOhm for a NiCd cell, and it increases with both cycling and chronological age.[27]Rising internal resistance causes the voltage at the terminals to drop under load, reducing the maximum current that can be drawn from them. Eventually they reach a point at which the battery can no longer operate the equipment it is installed in for an adequate period.

Highdrainapplications such as power tools may require the battery to beableto supply a current as high as (15 h-1)C (that is, a currentlevelthat would drain the battery in 1/15 hour if sustained;e.g.22.5 A for a battery with a capacityof1.5 Ah). Lower-power devices such as MP3 players may only require (0.1 h-1)C (e.g. 150 mA for a battery with a capacity of 1500 mAh). With similar battery technology, the MP3 player's battery will effectively last much longer, since it can tolerate a much higher internal resistance.[28]

[edit] Protection circuits required

Li-ion batteriesarenot as durable as nickelmetalhydride or nickel-cadmiumdesigns, and can be extremely dangerous if mistreated. They may explode if overheated or if charged to an excessively high voltage. Furthermore, they may be irreversibly damaged if discharged below a certain voltage. To reduce these risks, li-ion batteries generally contain a small circuit that shuts down the battery when discharged below a certain threshold (typically 3 V) or charged above a certain limit (typically 4.2 V).

Thiscircuitprevents deep discharge in normal use. However, when storedforlong periods, the small current drawn by the protectioncircuitrymay deeply drain the battery. Some applications attempt torecoverdeeply discharged cells by slow-chargingthem.

Furthermore,this circuit adds to the cost oflithium-ion batteries, which isusually higher than that ofcomparable-capacity NiMH or NiCDbatteries.

[edit] Safety features

Li-ion chemistryisnot as safe as nickelmetalhydride or nickel-cadmium, and a li-ion cell requires several mandatorysafetydevices to be built in before it can be considered safe foruseoutside of a laboratory. These are:[18]

shut-downseparator (forovertemperature),

tear-awaytab(for internal pressure),

vent(pressurerelief), and

thermalinterrupt(overcurrent/overcharging).

Thesedevicesoccupy useful space inside the cells, and reduce theirreliability;typically, they permanently and irreversibly disablethe cell whenactivated. They are required because the anodeproduces heat duringuse, while the cathode may produce oxygenduring use. Safetydevices and recent, improved electrode designsgreatly reduce oreliminate the risk of fire orexplosion.

The safety featuresoflithium-ion cells can be compared with nickelmetalhydride cells, which only have a hydrogen/oxygen recombination device(preventing damage due to mild overcharging) and a back-up pressurevalve.[citationneeded]

[edit] Product recalls

About 1% ofLi-ionbatteries are the subject of recalls.[29].

[edit] Specifications and design

 

 

Alithium-ionbattery from a mobile phone.

Specificenergydensity: 150 to 200 Wh/kg (540 to 720 kJ/kg)

Volumetricenergy density: 250 to 530 Wh/l (900 to1900J/cm³)

Specificpowerdensity: 300 to 1500 W/kg (@ 20 seconds[30]and 285 Wh/l)

Becauselithium-ion batteries can have a varietyof cathode and anodematerials, the energy density and voltage varyfrom chemistry tochemistry.

Lithium ionbatterieswith a lithium iron phosphate cathode and graphite anodehave anominal open-circuitvoltage of3.2 V and a typical charging voltage of 3.6 V. Lithium nickel manganese cobalt (NMC) oxide cathode with graphite anodes have a 3.7 V nominal voltage with a 4.2 V max charge. The charging procedure is done at constant voltage with current limiting circuitry. This means charging with constant current until a voltage of 4.2 V is reached by the cell and continuing with a constant voltage applied until the current drops close to zero. Typically the charge is terminated at 7% of the initial charge current. In the past, lithium-ion batteries could not be fast-charged and typically needed at least two hours to fully charge. Current generation cells can be fully charged in 45 minutes or less; some Lithium-Ion variants can reach 90% in as little as 10 minutes.[31]

[edit] Improvements to Lithium Ion Battery Technology

[edit] Overview

Improvementsfocus on several areas, and ofteninvolve advances innanotechnology andmicrostructures:

Increasing cyclelifeand performance (decreases internal resistance and increasesoutputpower) by changing the composition of the material used intheanode and cathode along with increasing the effective surfaceareaof the electrodes.(related developments have helpedultracapacitors)

Improvingcapacity by improving the structure toincorporate more activematerials.

Improvingthesafety of Lithium Ion style batteries.

[edit] Manganese Spinel Cathodes

LG, which is the third largest producer of lithium ion batteries, uses the lithium manganese spinel for its cathode. It is working with its subsidiary CPI to commercialize lithium ion batteries containing manganese spinel for HEVapplications.[32] Several other companies are also working on manganese spinel, including NEC and Samsung.[33]

[edit] Lithium Iron Phosphate Cathode With Traditional Anode

The UniversityofTexas firstlicensed its patent for lithium iron phosphate cathodestothe canadian utility Hydro-Québec.[34] Phostechwas later spun-off from Hydro-Québec for the sole development of lithium iron phosphate.

ValenceTechnology, located in Austin, Texas, is also working on lithium iron phosphate cells. Since March 2005, the Segway Personal Transporter has been shippingwithextended-range lithium-ion batteries[35]madeby Valence Technology using iron phosphate cathodematerials.Segway, Inc. chose to build their large-format batterywith thiscathode material because of its improved safety overmetal-oxidematerials.

InNovember2005, A123Systems announced[36] the development of lithium iron phosphate cells based on research licensed from MIT.[37][38] While the battery has slightly lower energy density than other competing Lithium Ion technologies, a 2 Ahr cell can provide a peak of 70 Amps without damage and operate at temperatures above 60 degrees C. Their first cell is in production (1Q/2006) and being used in consumer products including DeWalt power tools, aviation products, automotive hybrid systems and PHEVconversions.

LiFePO4cellsare currently available commercially.

[edit] High Power Cathode using Lithium Nickel Manganese Cobalt (NMC)

ImaraCorporation, based out of MenloPark, CAis commercializing a new materials-agnostictechnology first applied on an NMC material which has the effect oflowering impedance and extending cycle life. These high powercapable cells have high energy density relative to other high powercells in the market.[39]Thebatteries are being deployed in power tools, outdoor powerequipmentand hybrid vehicles.

[edit] Traditional Cathode With Lithium Titanate Anode

Mainarticle:Lithium-titanatebattery

Altairnano, a small firm based in Reno, Nevada, has announced a nano-sized titanate electrode material for lithium-ion batteries. It is claimed the prototype battery has three times the power output of existing batteries and can be fully charged in six minutes. However the energy capacity is about half that of normal li-ion cells. The company also says the battery cells have now achieved a life of over 9,000 charge cycles and they still retain up to 85% charge capacity, so durability and battery life are much longer, estimated to be around 20 years or four times longer than regular lithium-ion batteries. The batteries can operate from -50 °C to over 75 °C and will not explode or result in thermal runaway even under severe conditions because they do not contain graphite-coated-metal anode electrode material.[40]Thebatteries are currently being tested in a new production carmade byPhoenixMotorcarswhich was on display at the 2006 SEMAmotorshow. They're also beingtested, on a one megawatt grid scale,in the PJM InterconnectionRegional Transmission Organizationcontrol area[41]inNorristown,PAas well as by several branches of the U.S. Department of Defense.[42]Inaddition the batteries are being demonstrated by Proterra intheirall-electric EcoRide BE35 vehicle, a lightweight35-footbus.[43]Altairnanois currently working with three different cellchemistries, forvarious energy and power storage applications,with another new cellchemistry expected in the fall of 2009. Thenature of their latestcathode materials is currentlyproprietary.

[edit] Combined anode and cathode developments

EnerDel, which is jointly owned by Ener1 and Delphi, is working to commercialize cells containing a titanate anode and manganese spinel cathode.[44] Although the cells show excellent thermal properties and cyclability, their low voltage may hamper commercial success.[45]

[edit] Research claims

In April 2006, agroupof scientists at MIT announced a process which uses viruses to form nano-sized wires. These can be used to build ultrathin lithium-ion batteries with three times the normal energy density.[46]

As of June2006,researchers in Francehave created nanostructured battery electrodeswith several times the energy capacity, by weight and volume, ofconventional electrodes.[47]

In the September2007issue of Nature, researchers from the University ofWaterloo,Canada, reported a new cathode chemistry, whereby thehydroxidegroup in the iron phosphate cathode was replacedbyfluorine. [5]Theadvantages seem to betwo-fold. First, there is less volume changein the cathode over acharge cycle which indicates a possibility forlonger battery life.Second, the chemistry allows the substitutionof Sodium or aSodium/Lithium mixture for the Lithium in the battery(hence theirreference to it as an Alkali-Ionbattery).

InNovember2007, Subaru unveiled their concept G4e electric vehicle with a lithium vanadium oxide based lithium ion battery, promising double the energy density of a conventional lithium ion battery (lithium cobalt oxide and graphite).[6] In the lab, Lithium vanadium oxide anodes, paired with lithium cobalt oxide cathodes, have achieved 745Wh/l, nearly three times the volumetric energy density of conventional lithium ion batteries. [7]

InDecember2007, researchers at StanfordUniversityreportedcreating a lithium ion nanowirebatterywith ten times the energy density (amount ofenergy available byweight) through using silicon nanowiresdeposited on stainless steelas the anode. The battery takesadvantage of the fact that siliconcan hold large amounts oflithium, and helps alleviate thelongstanding problem of crackingby the small size of the wires.[8]Togain a tenfold improvement in energy density, the cathode wouldneedto be improved as well; however, just improving the anode assuchcould provide "several" times the energy density, according totheteam. The team leader, Yi Cui, expects to be able tocommercializethe technology in about five years.[9].Havinga large capacitive anode won't increase the capacity of thebatteryas predicted by the author when the cathode material is farlesscapacitive than the anode. However current Li-ion capacity ismainlylimited by the low theoretical capacity (372 mAh g−1) ofgraphite asthe anode material so improvement would be significantand limitedby cathode material instead ofanode.

There are trialsinprogress to use metal hydrides as anode material forLi-ionbatteries. Practical capacity of electrode as high as 1480mAh g-1is reported.[10]

InApril2009 a report inNewScientistclaimed that Angela Belcher's team at MIT hadsucceeded in producingthe first full virus-based 3-volt Lithiumion battery.[48]

[edit] Guidelines for prolonging Li-ion battery life

Likemanyrechargeable batteries, lithium-ion batteries should bechargedearly and often. However, if they are not used for a longtime,they should be brought to a charge level ofaround40%–60%

Lithium-ionbatteriesshould not be frequently fully discharged andrecharged("deep-cycled"), but this may be necessary after aboutevery 30threcharge to recalibrate any electronic charge monitor(e.g. abattery meter). This allows the monitoring electronics tomoreaccurately estimate battery charge.[28]

Li-ionbatteriesshould never be depletedto below their minimum voltage, 2.4 V to 3.0 V per cell.

Li-ionbatteriesshould be kept cool. Ideally they are stored in arefrigerator.Aging will take its toll much faster at hightemperatures. The hightemperatures found in cars cause lithium-ionbatteries to degraderapidly.

Li-ionbatteriesshould not be frozen [49] (most lithium-ion battery electrolytes freeze at approximately −40 °C; however, this is much colder than the lowest temperature reached by household freezers).

Li-ionbatteriesshould be bought only when needed, because the agingprocess beginsas soon as the battery ismanufactured.[28]

When using anotebookcomputer running from fixed line power over extendedperiods,consider removing the battery[50]and storing it in a cool place so that it is not affected by the heat produced by the computer.

[edit] Storage temperature and charge

Storing aLi-ionbattery at the correct temperature and charge makes allthedifference in maintaining its storage capacity. The followingtableshows the amount of permanent capacity loss that will occurafterstorage at a given charge levelandtemperature.

Permanent Capacity Loss versusStorageConditions

Storage Temperature

40%Charge

100%Charge

0°C (32°F)

2%loss after 1 year

6%loss after 1 year

25°C (77°F)

4%loss after 1 year

20%loss after 1 year

40°C (104°F)

15%loss after 1 year

35%loss after 1 year

60°C (140°F)

25%loss after 1 year

80%loss after 6 months

Source:BatteryUniversity.com[28]



It issignificantlybeneficial to avoid storing a lithium-ion battery atfull charge. ALi-ion battery stored at 40% charge will last manytimes longerthan one stored at 100% charge, particularly athighertemperatures.[28]

If a Li-ion batteryisstored with too low a charge, there is a risk of allowing thechargeto drop below the battery's low-voltage threshold, resultingin anunrecoverable dead battery. Once the charge has dropped tothislevel, recharging it can be dangerous. Some batteriesthereforefeature an internal safety circuit which will preventcharging inthis state, and the battery will be for all practicalpurposesdead.[citationneeded]

Incircumstanceswhere a second Li-ion battery is available for agiven device, it isrecommended that the unused battery bedischarged to 40% and placedin the refrigerator to prolong itsshelf life. While the battery canbe used or charged immediately,some Li-ion batteries will providemore energy when brought to roomtemperature.

[edit] Prolonging Life in Multiple Cells Through Cell Balancing

Analogfrontends that balance cells and eliminate mismatches of cells inseriesor parallel significantly improve battery efficiency andincreasethe overall pack capacity. As the number of cells and loadcurrentsincrease, the potential for mismatch also increases. Thereare twokinds of mismatch in the pack: State-of-Charge (SOC)andcapacity/energy (C/E) mismatch. Though the SOC mismatch ismorecommon, each problem limits the pack capacity (mAh) to thecapacityof the weakest cell.

It is importanttorecognize that the cell mismatch results more from limitationsinprocess control and inspection than from variations inherent intheLithium Ion chemistry. The use of cell balancing can improvetheperformance of series connected Li-ion Cells by addressing bothSOCand C/E issues.[51]SOC mismatch can be remedied by balancing the cell during an initial conditioning period and subsequently only during the charge phase. C/E mismatch remedies are more difficult to implement and harder to measure and require balancing during both charge and discharge periods.

CellBalancing

Cell balancingisdefined as the application of differential currents toindividualcells (or combinations of cells) in a series string.Normally, ofcourse, cells in a series string receive identicalcurrents. Abattery pack requires additional components andcircuitry toachieve cell balancing. However, the use of a fullyintegratedanalog front end for cell balancing[52]reduces the required external components to just balancing resistors.

This typeofsolution eliminates the need for discrete capacitors, diodesandmost other resistors to achieve balance.

Batterypack cells are balancedwhen all the cells inthe battery pack meet twoconditions:

If allcellshave the same capacity, then they are balanced when they havethesame State of Charge (SOC.) In this case, the Open CircuitVoltage(OCV) is a good measure of the SOC. If, in an out of balancepack,all cells can be differentially charged to fullcapacity(balanced), then they will subsequently cycle normallywithout anyadditional adjustments. This is mostly a oneshotfix.

If thecellshave different capacities, they are also considered balancedwhenthe SOC is the same. But, since SOC is a relative measure,theabsolute amount of capacity for each cell is different. To keepthecells with different capacities at the same SOC, cellbalancingmust provide differential amounts of current to cells inthe seriesstring during both charge and discharge oneverycycle.

[edit] Safety

Lithium-ionbatteriescan rupture, ignite, or explode when exposed to hightemperatureenvironments, for example in an area that is prone toprolongeddirect sunlight.[53]Short-circuiting a Li-ion battery can cause it to ignite or explode, and as such, any attempt to open or modify a Li-ion battery's casing or circuitry is dangerous. Li-ion batteries contain safety devices that protect the cells inside from abuse, and, if damaged, can cause the battery to ignite or explode.

Contaminantsinsidethe cells can defeat these safety devices. For example,themid-2006 recall of approximately 10 million Sony batteriesusedin Dell, Sony, Apple, Lenovo/IBM, Panasonic, Toshiba, Hitachi, Fujitsu and Sharp laptops was stated to be as a consequence of internal contamination with metal particles. Under some circumstances, these can pierce the separator, causing the cell to short, rapidly converting all of the energy in the cell to heat resulting in an exothermic oxidizing reaction, increasing the temperature to a few hundred degrees Celsius in a fraction of a second.[54]This causes the neighboring cells to heat up, causing a chain thermal reaction.

The mid-2006Sonylaptop battery recall was not the first of its kind, however itwasthe largest to date. During the past decade there havebeennumerous recalls of lithium-ion batteries in cellular phonesandlaptops owing to overheating problems. In October2004,Kyocera Wireless recalled approximately 1 million batteries used in cellular phones, due to counterfeit batteries produced in Kyocera's name.[55] In December 2006, Dell recalled approximately 22,000 batteries from the U.S. market.[56]InMarch 2007, Lenovo recalled approximately 205,000 9-celllithium-ionbatteries due to an explosion risk. In August 2007,Nokiarecalledover 46 million lithium-ion batteries, warning that someof themmight overheat and possibly explode.[57]Therewas an incident in the Philippinesinvolvinga NokiaN91,which uses the BL-5C battery.[58]

Replacingthelithiumcobaltoxide cathode material in li-ion batteries with lithiated metal phosphate leads to longer cycle, and shelf life, improves safety, but lowers capacity. Currently these 'safer' li-ion batteries are mainly used in electric cars and other large-capacity battery applications, where the safety issues are more critical. [59]

Another option istouse manganese oxide or iron phosphate cathode.[60]

A new class ofhighpower cathode materials, lithium nickel manganese cobalt(NMC)oxide has recently been introduced that have 40% higherenergydensity than iron phosphate, 3 times the cycle life ofmanganeseoxide and exceptional high power performance. These cellshave asignificantly higher temperature tolerance compared tolithiumcobalt oxide. [61]

[edit] Restrictions on transportation

As ofJanuary2008, the US Department of Transportation issued a new rulethatpermits passengers on board commercial aircraft to carrylithiumbatteries in their checked baggage, if and only if theyareinstalled in a device.[62].

The purpose ofthisrestriction is that it greatly reduces the chances of thembecomingshort-circuited and causing a fire. The only types ofbatteriesaffected by this rule are ones containing lithium,includingLi-ion, Lithium Polymer, and Lithium Cobalt Oxidechemistries. Incidentally, hand luggage is not affected by the ruling.

[edit] Uses

Across theglobe,major automakers including GeneralMotors,BYD Auto, Hyundai, Toyota, and Tata Motors have been racing to be first to sell electric vehicles powered by lithium-ion batteries.[63] A US company Tesla Motors is already delivering their lithium-ion-powered BEV Tesla Roadster.[64]Inthe aftermarket, models such as the Prius have been fitted with lithium-ion batteries.[65]

[edit] See also

Battery balancer

Battery holder

Battery recycling

Lithium battery

Lithium ironphosphatebattery

Nanowire battery

Power-to-weightratio

Silver-oxidebattery

Superpolymer

Lithiumpolymerbattery

[edit] References

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^ http://www.panasonic.com/industrial/battery/oem/images/pdf/Panasonic_LiIon_CGA103450A.pdf

^ Lithium IonBatteryResearch

^ The effect of PHEV and HEV duty cycles on battery and battery pack performance, http://www.pluginhighway.ca/PHEV2007/proceedings/PluginHwy_PHEV2007_PaperReviewed_Valoen.pdf

^ http://www.werbos.com/E/WhoKilledElecPJW.htm (which links to http://www.thunder-sky.com/home_en.asp)

^ MRS Website : Theme Article - Science and Applications of Mixed Conductors for Lithium Batteries

^ Electrical Energy StorageandIntercalation Chemistry - WHITTINGHAM 192 (4244): 1126-Science

^ Activity and Diffusivity of Lithium Intercalated in Graphite - Dept. of Energy Citation

^ US patent 4304825, "Rechargeablebattery",granted 1981-12-08 

^ USPTO search for inventions by "Goodenough, John"

^ http://dx.doi.org/10.1016/0025-5408(83)90138-1

^ http://books.google.com/books?id=k4duxuea3eIC

^ IEEE Spectrum: Lithium Batteries Take to the Road

^ http://dx.doi.org/10.1016/0378-7753(89)80153-3

^ Phospho-olivines as positive-electrode materials for rechargeable lithium batteries, A.K. Padhi, K.S. Nanjundaswamy and J.B. Goodenough, J. Electrochem. Soc., 144, 1188-1194 (1997).. http://scitation.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JESOAN000144000004001188000001&idtype=cvips&gifs=yes

^ a b "In search of the perfect battery". The Economist. 2008-03-06. http://www.economist.com/science/tq/displaystory.cfm?story_id=10789409. Retrieved on 2008-08-24

^ Silberberg, M. 2006. Chemistry: The Molecular Nature of Matter and Change, 4th Ed. New York (NY): McGraw-Hill Education. p 935.

^ a b c (pdf) Gold Peak IndustriesLtd.,Lithium Ion technical handbook. http://www.gpbatteries.com/html/pdf/Li-ion_handbook.pdf

^ H.C. Choi et al., J. Phys. Chem. B 107 p5806(2003) doi:10.1021/jp030438w

^ G.G. Amatucci, J.M. Tarascon, L.C. Kein J. Electrochemical Society 143 p1114 1996 doi:10.1149/1.1836594

^ http://www.cheric.org/PDF/Symposium/S-J2-0063.pdf

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^ Buchmann, Isidor. "Will Lithium-Ion batteries power the new millennium?". Isidor Buchmann (CEO of Cadex Electronics Inc.). http://www.buchmann.ca/Article5-Page1.asp

^ Aging -capacityloss

^ Altair Nano: Power & Energy Systems

^ Battery University: Fig.1Non-recoverable capacity loss

^ Buchmann, Isidor. "Choosing a battery that will last". Isidor Buchmann (CEO of Cadex Electronics Inc.). http://www.buchmann.ca/Article9-Page1.asp

^ a b c d e Buchmann, Isidor (September 2006). "BatteryUniversity.com: Howtoprolong lithium-based batteries". Cadex Electronics Inc..http://www.batteryuniversity.com/parttwo-34.htm

^ Lewis, Leo (August 21, 2007). "Japanese experts demand change to make phones and laptops safe". The Times. http://business.timesonline.co.uk/tol/business/industry_sectors/technology/article2295743.ece

^ http://www.e-one.com.tw/News_2005_e.htm

^ AeroVironment Achieves Electric Vehicle Fast Charge Milestone Test Rapidly Recharges a Battery Pack Designed for Use in Passenger Vehicles. 10 Minute Re-Charge Restores Enough Energy to Run Electric Vehicle for Two Hours at 60 Miles Per Hour

^ http://www.aei-online.org/automag/techbriefs/10-2006/1-114-10-16.pdf

^ IEEE Spectrum: Lithium Batteries Take to the Road

^ Bickel & Brewer - A law firm devoted exclusively to the resolution of complex commercial disputes. Bickel & Brewer was formed with a singular goal: to serve clients in significant, disputed matters that involve substantial dollar or business exposures...: Detail

^ http://www.segway.com/personal-transporter/lithium_ion.html

^ http://www.a123systems.com/html/news/articles/051102_news.html

^ Green Car Congress: A123Systems Launches New Higher-Power, Faster Recharging Li-Ion Battery Systems

^ Yahoo! Groups

^ [http://www.imaracorp.com

^ Microsoft PowerPoint - 061125 Altair EDTA Presentation

^ [2]

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^ Microsoft PowerPoint -EnerDelTechnical Presentation.ppt[Read-Only]

^ Science Express (preprint) http://www.sciencemag.org/cgi/content/abstract/1122716

^ Technology Review: Higher-Capacity Lithium-Ion Batteries

^ Zandonella, Catherine (11 April 2009). "Battery grown from "armour plated" viruses". New Scientist (Tribune media Services International) 202 (2703): 1. http://www.newscientist.com/article/mg20227035.400-batteries-grown-from-armourplated-viruses.html

^ L.M. Cristo, T. B. Atwater. Characteristics and Behavior of 1M LiPF6 1EC:1DMC Electrolyte at Low Temperatures. Fort Monmouth, NJ: U.S. Army Research. 

^ How to prolong lithium-based batteries

^ AN1333

^ ISL9208 Multi-CellLi-ionBattery Pack OCP/Analog Front End

^ http://www.tayloredge.com/museum/mymuseum/sciencefun/li-ion_003.mov

^ Dell laptop explodesatJapanese conference - The INQUIRER

^ Kyocera Wireless (2004-10-28). Kyocera LaunchesPrecautionaryBattery Recall, Pursues Supplier ofCounterfeitBatteries. Press release. http://www.kyocera-wireless.com/news/20041028_2.htm

^ Tullo, Alex. "Dell Recalls Lithium Batteries." Chemical and Engineering News 21 August 2006: 11.

^ http://en.wikinews.org/wiki/Nokia_issues_BL-5C_battery_warning%2C_offers_replacement

^ Nokia N91 cellphoneexplodes

^ Safety Last - NewYorkTimes

^ Technology Review: New Batteries Readied for GM's Electric Vehicle