关于 开关稳压电源 或 锂离子电池 的英文文章
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首先要说明的是开关稳压电源是switch voltage-stabilized source
锂离子电池是 Lithium ion battery
参考
开关稳压电源的原理及发展 Principle and development of switch voltage-stabilized source
本文简述了开关稳压电源的基本原理,以及开关电源与线性电源、相控电源相比较的优劣性.介绍了数字开关稳压电源的发展前景.
仪器仪表用户 Instrumentation Customer 2007年
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Lithium-ion battery
Lithium-ion batteries (sometimes abbreviated Li-ion batteries) are a type of rechargeable battery in which a lithium ion moves between the anode and cathode. The lithium ion moves from the anode to the cathode ring discharge and from the cathode to the anode when charging.
Lithium ion batteries are commonly used in consumer electronics. They are currently one of the most popular types of battery for portable electronics, with one of the best energy-to-weight ratios, no memory effect, and a slow loss of charge when not in use. Certain kinds of mistreatment may cause Li-ion batteries to explode. In addition to uses for consumer electronics, lithium-ion batteries are growing in popularity for defense, automotive, and aerospace applications e to their high energy density.
The three primary functional components of a lithium ion battery are the anode, cathode, and electrolyte, for which a variety of materials may be used. Commercially, the most popular material for the anode is graphite, although materials such as TiS2 were originally used.[3] However, the cathode is generally one of three materials: a layered oxide, such as cobalt oxide, a polyanion, such as lithium iron phosphate, or a spinel, such as manganese oxide. 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 have a metallic lithium anode and lithium ion batteries have an anode material into which lithium inserts.
History
Lithium batteries were first proposed by M.S. Whittingham, then at Exxon, in the 1970s.[4] Whittingham used titanium sulfide as the cathode and lithium metal as the anode.
Lithium batteries, in which metallic lithium is the anode, posed severe safety issues. As a result, lithium ion-batteries were developed, in which the anode, like the cathode, is also a material into which lithium ions insert. Lithium-ion batteries came into reality once Bell Labs developed a workable graphite anode[5] to provide an alternative to lithium metal, the lithium battery. Following groundbreaking cathode research by a team led by John Goodenough[6] (then at Oxford University, now at the University of Texas, Austin), the first commercial lithium ion battery was released by Sony in 1991. The cells utilized layered oxide chemistry, specifically lithium cobalt oxide. These batteries revolutionized consumer electronics.
In 1983, Michael Thackeray and coworkers identified manganese spinel as a cathode material.[7] Spinel showed great promise, since it is a low-cost material, has good electronic and lithium ion conctivity, and possess a three dimensional structure, which gives it good structural stability. Although pure manganese spinel shows fade with cycling, this can be overcome with additional chemical modification of the material.[8] Manganese spinel is currently used in commercial cells.[9]
In 19, Arumugam Manthiram and John Goodenough at the University of Texas at Austin showed that cathodes containing polyanions, such as sulfates, show higher voltage than oxides e to the inctive effect of the polyanion.[10] Following this, in 1996, Goodenough and coworkers discovered the electrochemical utility of the olivine material lithium iron phosphate, LiFePO4. It is an important and emerging cathode material for lithium-ion batteries e in part to its enhanced safety compared to other lithium-ion chemistries. Cells containing lithium iron phosphate cathodes have been commercialized by multiple companies, including Phostech, Valence Technology, A123Systems, Aleees and Lithium Technology Corp.
[edit] Electrochemistry
The three participants in the electrochemical reactions in a lithium ion battery are the anode, cathode, and electrolyte.
Both the anode and cathode are materials into which lithium inserts and extracts. The process of lithium moving into the anode or cathode is referred to as insertion, and the reverse process, in which lithium moves out of the anode or cathode is referred to as extraction. When discharging of the cell, the lithium is extracted from the anode and inserted into the cathode. When charging the cell, the exact reverse process occurs: lithium is extracted from the cathode and inserted into the anode.
The anode of a conventional Li-ion cell is made from carbon, the cathode is a metal oxide, and the electrolyte is a lithium salt in an organic solvent. [11]
The underlying chemical reaction that allows Li-ion cells to provide electricity is:
[citation needed]
It is important to note that lithium ions themselves are not being oxidized; rather, in a lithium-ion battery the lithium ions are transported to and from the cathode or anode, with the transition metal, Co, in LixCoO2 being oxidized from Co3+ to Co4+ ring charging, and reced from Co4+ to Co3+ ring discharge.
Cathodes
Material Average Voltage Gravimetric Capacity
LiCoO2 3.7 V 140 mAh/g
LiMnO2 4.0 V 100 mAh/g
LiFePO4 3.3 V 170 mAh/g
Li2FePO4F 3.6 V 115 mAh/g
[edit] Electrolytes
Liquid electrolytes in Li-ion batteries consist of solid lithium-salt electrolytes, such as LiPF6, LiBF4, or LiClO4, and organic solvents, such as ether. A liquid electrolyte concts Li ions, which act as a carrier between the cathode and the anode when a battery passes an electric current through an external circuit. However, solid electrolytes and organic solvents are easily decomposed on anodes ring charging, thus preventing battery activation. Nevertheless, when appropriate organic solvents are used for electrolytes, the electrolytes are decomposed and form a solid electrolyte interface at first charge that is electrically insulating and high Li-ion concting. The interface prevents decomposition of the electrolyte after the second charge. For example, ethylene carbonate is decomposed at a relatively high voltage, 0.7 V vs. Li, and forms a dense and stable interface.[citation needed]
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.[citation needed]
[edit] Advantages and disadvantages
[edit] Advantages
Lithium-ion batteries can be formed into a wide variety of shapes and sizes so as to efficiently fill available space in the devices they power.
Li-ion batteries are lighter than other equivalent secondary batteries—often much lighter. The energy is stored in these batteries through 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 conctivity additives rece 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 open circuit voltage that can be obtained in comparison to aqueous batteries (such as lead acid, nickel metal hydride and nickel cadmium).[citation needed]
Li-ion batteries do not 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 nickel metal hydride batteries (Low self-discharge NiMH batteries have much lower values; they can still hold 85% of their charge, after one year) and 10% per month in nickel cadmium batteries.
According to one manufacturer, Li-ion cells (and, accordingly, "mb" Li-ion batteries) do not have any self-discharge in the usual meaning of this word.[12] 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, e 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.
Disadvantages
A unique drawback of the Li-ion battery is that its life span is dependent upon aging from time of manufacturing (shelf life) regardless of whether it was charged, and not just on the number of charge/discharge cycles. So an older battery will not last as long as a new battery e solely to its age, unlike other batteries. This drawback is not widely published.[13]
At a 100% charge level, a typical Li-ion laptop battery that is full most of the time at 25 degrees Celsius or 77 degrees Fahrenheit will irreversibly lose approximately 20% capacity per year. However, a battery stored inside a poorly ventilated laptop may be subject to a prolonged exposure to much higher temperatures than 25 °C, which will significantly shorten its life. The capacity loss begins from the time the battery was manufactured, and occurs even when the battery is unused. Different storage temperatures proce 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, these figures are reced to 2%, 4%, 15% at 0, 25 and 40 degrees Celsius respectively.
Under certain temperature conditions, the batteries have a tendency to become damaged and can sometimes never fully recharge again. In certain situations where the temperature is too cold (below the recommended battery temperature) the battery will still hold its charge but cannot be recharged as a result of the cold temperature. This is most common in smaller batteries such as cellular phones and handheld devices.
As batteries age, their internal resistance rises. This causes the voltage at the terminals to drop under load, recing 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.
High drain applications such as powertools may require the battery to be able to supply a current of (15 h-1)C - 15/hour times "C" - the battery capacity in Ampere hours, whereas MP3 players may only require (0.1 h-1)C (discharging in 10 hours). With similar technology, the MP3 battery can tolerate a much higher internal resistance, so will have an effective life of many more cycles.[14]
Li-ion batteries can even go into a state that is known as deep discharge. At this point, the battery may take a very long time to recharge. For example, a laptop battery that normally charges fully in 3 hours may take up to 42 hours to recharge. Or the deep discharge state may be so severe that the battery will never come back to life. Deep discharging only takes place when procts with rechargeable batteries are left unused for extended periods of time (often 2 or more years) or when they are fully discharged so often that they can no longer hold a charge. This makes Li-ion batteries unsuitable for back-up applications where they may become completely discharged.
A stand-alone Li-ion cell must never be discharged below a certain voltage to avoid irreversible damage. Therefore all Li-ion battery systems are equipped with a circuit that shuts down the system when the battery is discharged below the predefined threshold.[12] It should thus be impossible to "deep discharge" the battery in a properly designed system ring normal use. This is also one of the reasons Li-ion cells are rarely sold as such to consumers, but only as finished batteries designed to fit a particular system.
When the voltage monitoring circuit is built inside the battery (a so-called "smart" battery) rather than the equipment, it continuously draws a small current from the battery even when the battery is not in use; furthermore, the battery must not be stored fully discharged for prolonged periods of time, to avoid damage e to deep discharge.
Li-ion batteries are not as rable as nickel metal hydride or nickel-cadmium designs and can be extremely dangerous if mistreated. They are usually more expensive.
Li-ion chemistry is not as safe as nickel metal hydride or nickel-cadmium, and a Li-ion cell requires several mandatory safety devices to be built in before it can be considered safe for use outside of a laboratory. These are: shut-down separator (for overtemperature), tear-away tab (for internal pressure), vent (pressure relief), and thermal interrupt (overcurrent/overcharging).[12] The devices take away useful space inside the cells, and add an additional layer of unreliability. Typically, their action is to permanently and irreversibly disable the cell.
Approximately 1% of Li-ion batteries are the subject of recalls.[15] .
The number of safety features can be compared with that of a nickel metal hydride cell, which only has a hydrogen/oxygen recombination device (preventing damage e to mild overcharging) and a back-up pressure valve.[citation needed]
Specifications and design
Specific energy density: 150 to 200 Wh/kg (540 to 720 kJ/kg)
Volumetric energy density: 250 to 530 Wh/l (900 to 1900 J/cm³)
Specific power density: 300 to 1500 W/kg (@ 20 seconds[16] and 285 Wh/l)
Because lithium-ion batteries can have a variety of cathode and anode materials, cell specifications, such as the energy density and voltage vary from chemistry to chemistry.
Lithium ion batteries with a lithium iron phosphate cathode and graphite anode have a nominal open-circuit voltage of 3.6 V and a typical charging voltage of 4.2 V. The charging procere 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.
Commercialization of Lithium Ion Batteries
Lithium Cobalt Oxide Cathodes
Lithium ion batteries were first commercialized by Sony in 1991.[18] The cells utilized a lithium cobalt oxide cathode and a graphite anode. Sony and Sanyo are the leading procers of lithium ion batteries.[19][20] A variety of Chinese, Japanese, and South Korean companies proce cells based on the lithium cobalt oxide cathode chemistry.[21]
[edit] Manganese Spinel Cathodes
LG, which is the third largest procer 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 HEV applications.[22] Several other companies are also working on manganese spinel, including NEC and Samsung.[23]
[edit] Lithium Iron Phosphate Cathodes
The University of Texas first licensed its patent for lithium iron phosphate cathodes to HydroQuebec.[24] Phostech was later spun-off from Hydroquebec for the sole development of lithium iron phosphate.
Valence Technology, located in Austin, TX, is also working on lithium iron phosphate cells. Since March 2005, the Segway Personal Transporter has been shipping with extended-range lithium-ion batteries[25] made by Valence Technology using iron phosphate cathode materials. Segway, Inc. chose to build their large-format battery with this cathode material because of its improved safety over metal-oxide materials.
In November 2005, A123Systems announced[26] the development of lithium iron phosphate cells based on research licensed from MIT.[27][28] While the battery has slightly lower energy density that 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 proction (1Q/2006) and being used in consumer procts including DeWalt power tools, aviation procts, automotive hybrid systems and PHEV conversions.
[edit] Titanate Anodes
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 can handle approximately 20,000 recharging cycles, so rability 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.[29] The batteries are currently being tested in a new proction car made by Phoenix Motorcars which was on display at the 2006 SEMA motorshow.
Enerdel, which is jointly owned by Ener1 and Delphi, is working to commercialize cells containing a titanate anode and manganese spinel cathode.[30] Although the cells show excellent thermal properties and cyclability, their low voltage may mitigate commercial success.[31]
All these formulations involve new electrodes (anodes or cathodes). By increasing the effective electrode area — thus decreasing the internal resistance of the battery — the current can be increased ring both use and charging. This is similar to developments in ultracapacitors. Therefore, the battery is capable of delivering more power (watts); however, the battery's capacity (ampere-hours) is increased only slightly.
http://www.google.com.sg/search?hl=en&q=Lithium+ion+battery&meta=
字数超限所以搂主自己去这些网站看吧
http://en.wikipedia.org/wiki/Lithium_ion_battery
参考资料：http://en.wikipedia.org/wiki/Lithium_ion_battery
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