• Contact us

HPL Electronics Co., Ltd
Add:
Kowloon Budg, 555 Nathan Road,Mongkok, Kowloon, HK
Tel: 00852-30732699
E-mail: market@hplbattery.com

Home > FAQ

lithium-ion battery (sometimes Li-ion battery or LIB) is a family of rechargeable battery types in which lithium ions move from the negative electrode to the positive electrode during discharge, and back when charging. Chemistry, performance, cost, and safety characteristics vary across LIB types. Unlike lithium primary batteries (which are disposable), lithium-ion electrochemical cells use an intercalated lithium compound as the electrode material instead of metallic lithium.

Lithium-ion batteries are common in consumer electronics. They are one of the most popular types of rechargeable battery for portable electronics, with one of the best energy densities, no memory effect, and a slow loss of charge when not in use. Beyond consumer electronics, LIBs are also growing in popularity for military, electric vehicle, and aerospace applications.[7] Research is yielding a stream of improvements to traditional LIB technology, focusing on energy density, durability, cost, and intrinsic safety.

Contents

[hide]

Charge and discharge

During discharge, lithium ions Li+ carry the current from the negative to the positive electrode, through the non-aqueous electrolyte and separator diaphragm.[11]

During charging, an external electrical power source (the charging circuit) applies a higher voltage (but of the same polarity) than that produced by the battery, forcing the current to pass in the reverse direction. The lithium ions then migrate from the positive to the negative electrode, where they become embedded in the porous electrode material in a process known as intercalation.

Construction

Cylindrical 18650 cell before closing

The three primary functional components of a lithium-ion battery are the anode, cathode, and electrolyte. The anode of a conventional lithium-ion cell is made from carbon, the cathode is a metal oxide, and the electrolyte is a lithium salt in an organic solvent.[12]

The most commercially popular anode material is graphite. The cathode is generally one of three materials: a layered oxide (such as lithium cobalt oxide), a polyanion (such as lithium iron phosphate), or a spinel (such as lithium manganese oxide).[13]

The electrolyte is typically a mixture of organic carbonates such as ethylene carbonate or diethyl carbonate containing complexes of lithium ions.[14] These non-aqueous electrolytes generally use non-coordinating anion salts such as lithium hexafluorophosphate (LiPF6), lithium hexafluoroarsenate monohydrate (LiAsF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), and lithium triflate (LiCF3SO3).

Depending on materials choices, the voltage, capacity, life, and safety of a lithium-ion battery can change dramatically. Recently, novel architectures using nanotechnology have been employed to improve performance.

Pure lithium is very reactive. It reacts vigorously with water to form lithium hydroxide and hydrogen gas. Thus, a non-aqueous electrolyte is typically used, and a sealed container rigidly excludes water from the battery pack.

Lithium ion batteries are more expensive than NiCd batteries but operate over a wider temperature range with higher energy densities, while being smaller and lighter. They are fragile and so need a protective circuit to limit peak voltages.

Formats

         lithium-ion battery pack.

Li-ion cells are available in various formats, which can generally be divided into four groups:[15]

  • Small cylindrical (solid body without terminals, such as those used in laptop batteries)
  • Large cylindrical (solid body with large threaded terminals)
  • Pouch (soft, flat body, such as those used in cell phones)
  • Prismatic (semi-hard plastic case with large threaded terminals, often used in vehicles' traction packs)

The lack of case gives pouch cells the highest energy density; however, pouch cells (and prismatic cells) require an external means of containment to prevent expansion when their SOC level is high.[16]

History

Lithium batteries were first proposed by M.S. Whittingham at Binghamton University, at Exxon, in the 1970s.[17] Whittingham used titanium(II) sulfide as the cathode and lithium metal as the anode.

The reversible intercalation in graphite[18][19] and intercalation into cathodic oxides [20][21] was also already discovered in the 1970s by J.O. Besenhard at TU Munich. He also proposed the application as high energy density Lithium cells[22][23]

Primary lithium batteries in which the anode is made from metallic lithium pose safety issues. As a result, lithium-ion batteries were developed in which both anode and cathode are made of a material containing lithium ions.

In 1979, John Goodenough demonstrated a rechargeable cell with high cell voltage in the 4V range using lithium cobalt oxide (LiCoO2) etc. as positive electrode and Lithium metal as negative electrode.[24] This innovation provided the positive electrode material which made the lithium-ion battery (LIB) possible. LiCoO2 is a stable positive electrode material which acts as a donor of Lithium ions, which meant that it could be used with negative electrode material other than Lithium metal. By enabling the use of stable and easy-to-handle negative electrode materials, LiCoO2 opened a whole new range of possibilities for novel rechargeable battery systems.

In 1981, Bell Labs developed a workable graphite anode[25] to provide an alternative to the lithium metal battery.

In 1982, Rachid Yazami demonstrated the reversible electrochemical intercalation of Lithium in graphite.[26][27] The organic electrolytes available at the time would decompose during charging if used with graphite negative electrode, preventing the early development of a rechargeable battery which employed the Lithium/graphite system. Yazami used a solid electrolyte to demonstrate that Lithium could be reversibly intercalated in graphite through an electrochemical mechanism.

In 1983, Dr. Michael Thackeray, Goodenough, and coworkers identified manganese spinel as a cathode material.[28] Spinel showed great promise, given low-cost, good electronic and lithium ion conductivity, and three-dimensional structure which gives it good structural stability. Although pure manganese spinel fades with cycling, this can be overcome with chemical modification of the material.[29] Manganese spinel is currently used in commercial cells.[30]

In 1985, Akira Yoshino assembled a prototype cell using as anode a certain carbonaceous material into which lithium ions could be inserted and as cathode lithium cobalt oxide (LiCoO2) etc. which is stable in air.[31] By using an anode material without metallic lithium, safety was dramatically improved over batteries which used lithium metal. The use of lithium cobalt oxide (LiCoO2) enabled industrial-scale production to be achieved easily.

This was the birth of the current lithium-ion battery.

Then in 1991, Sony and Asahi Kasei released the first commercial lithium-ion battery.

In 1989, Goodenough and Arumugam Manthiram of the University of Texas at Austin showed that cathodes containing polyanions, e.g. sulfates, produce higher voltages than oxides due to the inductive effect of the polyanion.[32]

In 1996, Goodenough, Akshaya Padhi and coworkers identified lithium iron phosphate (LiFePO4) and other phospho-olivines (lithium metal phosphates with olivine structure) as cathode materials.[33]

In 2002, Yet-Ming Chiang and his group at MIT showed a substantial improvement in the performance of lithium batteries by boosting the material's conductivity by doping it with aluminum, niobium and zirconium. The exact mechanism causing the increase became the subject of a debate.[34]

In 2004, Chiang again increased performance by utilizing iron-phosphate particles of less than 100 nanometers in diameter. This decreased particle density by almost one hundredfold, increased the cathode's surface area and improved capacity and performance. Commercialization led to a competitive market and a patent infringement battle between Chiang and Goodenough.[34]

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, and from which, lithium can migrate. During insertion (or intercalation) lithium moves into the electrode. During the reverse process, extraction (or deintercalation), lithium moves back out. When a lithium-based cell is discharging, the lithium is extracted from the anode and inserted into the cathode. When the cell is charging, the reverse occurs.

Useful work can only be extracted if electrons flow through a closed external circuit. The following equations are in units of moles, making it possible to use the coefficient x.

The positive electrode half-reaction (with charging being forwards) is: [35]

mathrm{LiCoO_2} leftrightarrows mathrm{Li}_{1-x}mathrm{CoO_2} + xmathrm{Li^+} + xmathrm{e^-}

The negative electrode half-reaction is:

xmathrm{Li^+} + xmathrm{e^-} + 6mathrm{C} leftrightarrows mathrm{Li_xC_6}

The overall reaction has its limits. Overdischarge supersaturates lithium cobalt oxide, leading to the production of lithium oxide,[36] possibly by the following irreversible reaction:

mathrm{Li^+} + mathrm{LiCoO_2} rightarrow mathrm{Li_2O} + mathrm{CoO}

Overcharge up to 5.2 Volts leads to the synthesis of cobalt(IV) oxide, as evidenced by x-ray diffraction[37]

 mathrm{LiCoO_2} rightarrow mathrm{Li^+} + mathrm{CoO_2}

In a lithium-ion battery the lithium ions are transported to and from the cathode or anode, with the transition metal, cobalt (Co), in LixCoO2 being oxidized from Co3+ to Co4+ during charging, and reduced from Co4+ to Co3+ during discharge.

[edit] Positive electrodes

Electrode materialAverage potential differenceSpecific capacitySpecific energy
LiCoO2 3.7 V 140 mA·h/g 0.518 kW·h/kg
LiMnO4 4.0 V 100 mA·h/g 0.400 kW·h/kg
LiNiO2 3.5 V 180 mA·h/g 0.630 kW·h/kg
LiFePO4 3.3 V 150 mA·h/g 0.495 kW·h/kg
Li2FePO4F 3.6 V 115 mA·h/g 0.414 kW·h/kg
LiCo1/3Ni1/3Mn1/3O2 3.6 V 160 mA·h/g 0.576 kW·h/kg
Li(LiaNixMnyCoz)O2 4.2 V 220 mA·h/g 0.920 kW·h/kg

Negative electrodes

Electrode materialAverage potential differenceSpecific capacitySpecific energy
Graphite (LiC6) 0.1-0.2 V 372 mA·h/g 0.0372-0.0744 kW·h/kg
Hard Carbon (LiC6) ? V ? mA·h/g ? kW·h/kg
Titanate (Li4Ti5O12) 1-2 V 160 mA·h/g 0.16-0.32 kW·h/kg
Si (Li4.4Si)[38] 0.5-1 V 4212 mA·h/g 2.106-4.212 kW·h/kg
Ge (Li4.4Ge)[39] 0.7-1.2 V 1624 mA·h/g 1.137-1.949 kW·h/kg

Electrolytes

The cell voltages given in the Electrochemistry section are larger than the potential at which aqueous solutions can electrolyze, in addition lithium is highly reactive to water, therefore, nonaqueous or aprotic solutions are used.

Liquid electrolytes in lithium-ion batteries consist of lithium salts, such as LiPF6, LiBF4 or LiClO4 in an organic solvent, such as ethylene carbonate, dimethyl carbonate, and diethyl carbonate. A liquid electrolyte conducts lithium 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 °C (68 °F)) are in the range of 10 mS/cm (1 S/m), increasing by approximately 30–40% at 40 °C (104 °F) and decreasing by a slightly smaller amount at 0 °C (32 °F)[40]

Unfortunately, organic solvents easily decompose on anodes during charging. However, when appropriate organic solvents are used as the electrolyte, the solvent decomposes on initial charging and forms a solid layer called the solid electrolyte interphase (SEI),[41] which is electrically insulating yet provides sufficient ionic conductivity. The interphase prevents decomposition of the electrolyte after the second charge. For example, ethylene carbonate is decomposed at a relatively high voltage, 0.7 V vs. lithium, and forms a dense and stable interface.[citation needed]

A good solution for the interface instability is the application of a new class of composite electrolytes based on POE (poly(oxyethylene)) developed by Syzdek et al.[42][43] It can be either solid (high molecular weight) and be applied in dry Li-polymer cells, or liquid (low molecular weight) and be applied in regular Li-ion cells.

Another issue that Li-ion technology is facing is safety. Large scale application of Li cells in Electric Vehicles needs a dramatic decrease in the failure rate. One of the solutions is the novel technology based on reversed-phase composite electrolytes, employing porous ceramic material filled with electrolyte.[44]

Advantages and disadvantages

Note that both advantages and disadvantages depend on the materials and design that make up the battery. This summary reflects older designs that use carbon anode, metal oxide cathodes, and lithium salt in an organic solvent for the electrolyte.

 

Advantages
  • Wide variety of shapes and sizes efficiently fitting the devices they power.
  • Much lighter than other energy-equivalent secondary batteries.[45]
  • High open circuit voltage in comparison to aqueous batteries (such as lead acid, nickel-metal hydride and nickel-cadmium).[46] This is beneficial because it increases the amount of power that can be transferred at a lower current.
  • No memory effect.
  • Self-discharge rate of approximately 5-10% per month, compared to over 30% per month in common nickel metal hydride batteries, approximately 1.25% per month for Low Self-Discharge NiMH batteries and 10% per month in nickel-cadmium batteries.[47] According to one manufacturer, lithium-ion cells (and, accordingly, "dumb" lithium-ion batteries) do not have any self-discharge in the usual meaning of this word.[35] What looks like a self-discharge in these batteries is a permanent loss of capacity (see Disadvantages). On the other hand, "smart" lithium-ion batteries do self-discharge, due to the drain of the built-in voltage monitoring circuit.
  • Components are environmentally safe as there is no free lithium metal.[citation needed]

Disadvantages

   Cell life

  • Charging forms deposits inside the electrolyte that inhibit ion transport. Over time, the cell's capacity diminishes. The increase in internal resistance reduces the cell's ability to deliver current. This problem is more pronounced in high-current applications. The decrease means that older batteries do not charge as much as new ones (charging time required decreases proportionally).
  • High charge levels and elevated temperatures (whether from charging or ambient air) hasten capacity loss.[48][49] Charging heat is caused by the carbon anode (typically replaced with lithium titanate which drastically reduces damage from charging, including expansion and other factors).[50]
  • A Standard (Cobalt) Li-ion cell that is full most of the time at 25 °C (77 °F) irreversibly loses approximately 20% capacity per year. Poor ventilation may increase temperatures, further shortening battery life. Loss rates vary by temperature: 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%, and 15%, respectively.[51][citation needed] In contrast, the calendar life of LiFePO4 cells is not affected by being kept at a high state of charge.[52]

Internal resistance

  • The internal resistance of standard (Cobalt) lithium-ion batteries is high compared to both other rechargeable chemistries such as nickel-metal hydride and nickel-cadmium, and LiFePO4 and lithium-polymer cells.[53] Internal resistance increases with both cycling and age.[49][54][55] Rising internal resistance causes the voltage at the terminals to drop under load, which reduces the maximum current draw. Eventually increasing resistance means that the battery can no longer operate for an adequate period.
  • To power larger devices, such as electric cars, connecting many small batteries in a parallel circuit is more effective[56] and efficient than connecting a single large battery.[57]

Safety requirements

If overheated or overcharged, Li-ion batteries may suffer thermal runaway and cell rupture.[58] In extreme cases this can lead to combustion. Deep discharge may short-circuit the cell, in which case recharging would be unsafe.[59] To reduce these risks, Lithium-ion battery packs contain fail-safe circuitry that shuts down the battery when its voltage is outside the safe range of 3–4.2 V per cell.[35][47] When stored for long periods the small current draw of the protection circuitry itself may drain the battery below its shut down voltage; normal chargers are then ineffective. Many types of lithium-ion cell cannot be charged safely below 0°C.[60]

Other safety features are required in each cell:[35]

  • shut-down separator (for overtemperature)
  • tear-away tab (for internal pressure)
  • vent (pressure relief)
  • thermal interrupt (overcurrent/overcharging)

These devices occupy useful space inside the cells, add additional points of failure and irreversibly disable the cell when activated. They are required because the anode produces heat during use, while the cathode may produce oxygen. These devices and improved electrode designs reduce/eliminate the risk of fire or explosion.

These safety features increase costs compared to nickel metal hydride batteries, which require only a hydrogen/oxygen recombination device (preventing damage due to mild overcharging) and a back-up pressure valve.[47]

Specifications and design

  • Specific energy density: 150 to 250 W·h/kg (540 to 900 kJ/kg)[1]
  • Volumetric energy density: 250 to 620 W·h/l (900 to 1900 J/cm³)[2]
  • Specific power density: 300 to 1500 W/kg (@ 20 seconds and 285 W·h/l)[1]

Because lithium-ion batteries can have a variety of cathode and anode materials, the energy density and voltage vary accordingly.

Lithium-ion batteries with a lithium iron phosphate cathode and graphite anode have a nominal open-circuit voltage of 3.2 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 performed at constant voltage with current-limiting circuitry (i.e., charging with constant current until a voltage of 4.2 V is reached in the cell and continuing with a constant voltage applied until the current drops close to zero). Typically, the charge is terminated at 3% of the initial charge current. In the past, lithium-ion batteries could not be fast-charged and needed at least two hours to fully charge. Current-generation cells can be fully charged in 45 minutes or less. Some lithium-ion varieties can reach 90% in as little as 10 minutes.[61]

Charging procedure

Stage 1: Apply charging current until the voltage limit per cell is reached.[62]

Stage 2: Apply maximum voltage per cell limit until the current declines below 3% of rated charge current.[62][unreliable source?]

Stage 3: Periodically apply a top-off charge about once per 500 hours.[62][unreliable source?]

The charge time is about three to five hours, depending on the charger used. Generally, cell phone batteries can be charged at 1C and laptop-types at 0.8C, where C is the current that would discharge the battery in one hour. Charging is usually stopped when the current goes below 0.03C but it can be left indefinitely depending on desired charging time. Some fast chargers skip stage 2 and claim the battery is ready at 70% charge.[62][unreliable source?]

Top-off charging is recommended when voltage goes below 4.05 V/cell.[62][unreliable source?]

Typically, lithium-ion cells are charged with 4.2 ± 0.05 V/cell, except for military long-life cells where 3.92 V is used for extending battery life. Most protection circuits cut off if either 4.3 V or 90 °C is reached. If the voltage drops below 2.50 V per cell, the battery protection circuit may also render it unchargeable with regular charging equipment. Most battery protection circuits stop at 2.7–3.0 V per cell.[62][unreliable source?]

For safety reasons it is recommended the battery be kept at the manufacturer's stated voltage and current ratings during both charge and discharge cycles.

Variations in materials and construction

The increasing demand for batteries has led vendors and academics to focus on improving the power density, operating temperature, safety, durability, charging time, output power, and cost of LIB solutions.

LIB types
AreaTechnologyResearchersTarget applicationDateBenefit
Cathode Manganese spinel (LMO) Lucky Goldstar Chemical,[63] NEC, Samsung,[64] Hitachi,[65] Nissan/AESC[66] Hybrid electric vehicle, cell phone, laptop 1996 durability, cost
  Lithium iron phosphate University of Texas/Hydro-Québec,[67]/Phostech Lithium Inc., Valence Technology, A123Systems/MIT[68][69] Segway Personal Transporter, power tools, aviation products, automotive hybrid systems, PHEV conversions 1996 moderate density (2 A·h outputs 70 amperes) operating temperature >60 °C (140 °F)
  Lithium nickel manganese cobalt (NMC) Imara Corporation, Nissan Motor[70][71]   2008 density, output, safety
  LMO/NMC Sony, Sanyo     power, safety (although limited durability)
  Lithium iron fluorophosphate University of Waterloo[72]   2007 durability, cost (replace Li with Na or Na/Li)
  Lithium air University of Dayton Research Institute[73] automotive 2009 density, safety[73]
  5% Vanadium-doped Lithium iron phosphate olivine Binghamton University[74]   2008 output
Anode Lithium-titanate battery (LT) Altairnano automotive (Phoenix Motorcars), electrical grid (PJM Interconnection Regional Transmission Organization control area,[75] United States Department of Defense[76]), bus (Proterra[77]) 2008 output, charging time, durability (20 years, 9,000 cycles), safety, operating temperature (-50–70 °C (-58–158 °F)[78][dead link]
  Lithium vanadium oxide Samsung/Subaru.[79] automotive 2007 density (745Wh/l)[80]
  Cobalt-oxide nano wires from genetically modified virus MIT   2006 density, thickness[81]
  Three-Dimensional (3D) Porous Particles Composed of Curved Two-Dimensional (2D) Nano-Sized Layers Georgia Institute of Technology [82] high energy batteries for electronics and electrical vehicles 2011 specific capacity > 2000 mA·h/g, high efficiency, rapid low-cost synthesis [83]
  Iron-phosphate nano wires from genetically modified virus MIT   2009 density, thickness[84][85][86]
  Silicon/titanium dioxide composite nano wires from genetically modified tobacco virus University of Maryland explosive detection sensors, biomimetic structures, water-repellent surfaces, micro/nano scale heat pipes 2010 density, low charge time[87]
  Porous silicon/carbon nanocomposite spheres Georgia Institute of Technology portable electronics, electrical vehicles, electrical grid 2010 high stability, high capacity, low charge time[88]
  nano-sized wires on stainless steel Stanford University wireless sensors networks, 2007 density[89][90] (shift from anode- to cathode-limited), durability issue remains (wire cracking)
  Metal hydrides Laboratoire de Réactivité et de Chimie des Solides, General Motors   2008 density (1480 mA·h/g)[91]
  Silicon Nanotubes (or Silicon Nanospheres) Confined within Rigid Carbon Outer Shells Georgia Institute of Technology, MSE, NanoTech Yushin's group [92] stable high energy batteries for cell phones, laptops, netbooks, radios, sensors and electrical vehicles 2010 specific capacity 2400 mA·h/g, ultra-high Coulombic Efficiency and outstanding SEI stability [93]
Electrode LT/LMO Ener1/Delphi,[94][95]   2006 durability, safety (limited density)
  Nanostructure Université Paul Sabatier/Université Picardie Jules Verne[96]   2006 density

Usage guidelines

      Prolonging battery pack life

  • Depletion below the low-voltage threshold (2.4 to 2.8 V/cell, depending on chemistry) results in a dead battery which does not even appear to charge because the protection circuit (a type of electronic fuse) disables it.[97] This can be reversed in many modern batteries, especially single-cell ones, by applying a charging voltage for long enough to make the cell voltage rise above the low-voltage threshold; however this behaviour varies by manufacturer.
  • Lithium-ion batteries should be kept cool; they may be stored in a refrigerator.[97][98]
  • The rate of degradation of Lithium-ion batteries is strongly temperature-dependent; they degrade much faster if stored or used at higher temperatures.[97][99]

  Multicell devices

Li-ion batteries require a Battery Management System to prevent operation outside each cell's Safe Operating Area (over-charge, under-charge, safe temperature range) and to balance cells to eliminate SOC mismatches, significantly improving battery efficiency and increasing overall capacity.[100] As the number of cells and load currents increase, the potential for mismatch also increases.[101] There are two kinds of mismatch in the pack: state-of-charge (SOC) and capacity/energy ("C/E") mismatch. Though SOC is more common, each problem limits pack capacity (mA·h) to the capacity of the weakest cell.

 Safety

Lithium-ion batteries can rupture, ignite, or explode when exposed to high temperature. Short-circuiting a battery will cause the cell to overheat and possibly to catch fire. Adjacent cells may also then heat up and fail, in some cases, causing the entire battery to ignite or rupture. In the event of a fire, the device may emit dense irritating smoke.[102]

Replacing the lithium cobalt oxide cathode material in lithium-ion batteries with a lithium metal phosphate such as lithium iron phosphate, improves cycle counts, shelf life and safety, but lowers capacity. Currently, these 'safer' lithium-ion batteries are mainly used in electric cars and other large-capacity battery applications, where safety issues are critical.[103]

Lithium-ion batteries normally contain safety devices to protect the cells from disturbance. However, contaminants inside the cells can defeat these safety devices.

  Recalls

In March 2007, Lenovo recalled approximately 205,000 batteries at risk of explosion. In August 2007, Nokia recalled over 46 million batteries at risk of overheating and exploding.[104] One such incident occurred in the Philippines involving a Nokia N91, which uses the BL-5C battery.[105]

In December 2006, Dell recalled approximately 22,000 laptop batteries from the U.S. market.[106] Approximately 10 million Sony batteries used in Dell, Sony, Apple, Lenovo/IBM, Panasonic, Toshiba, Hitachi, Fujitsu and Sharp laptops were recalled in 2006. The batteries were found to be susceptible to internal contamination by metal particles. Under some circumstances, these particles could pierce the separator, causing a short-circuit.[107]

In October 2004, Kyocera Wireless recalled approximately 1 million mobile phone batteries to identify counterfeits.[108]

  Transport restrictions

In January 2008, the United States Department of Transportation ruled that passengers on board commercial aircraft could carry lithium batteries in their checked baggage if the batteries are installed in a device. Types of batteries affected by this rule are those containing lithium, including Li-ion, lithium polymer, and lithium cobalt oxide chemistries. Lithium-ion batteries containing more than 25 grams (0.88 oz) equivalent lithium content (ELC) are exempt from the rule and are forbidden in air travel.[109] This restriction greatly reduces the chances of the batteries short-circuiting and causing a fire.[citation needed]

Additionally, a limited number of replacement batteries may be transported in carry-on luggage. Such batteries must be sealed in their original protective packaging or in individual containers or plastic bags.[109][110]

Some postal administrations restrict air shipping (including EMS) of lithium and lithium-ion batteries, and products containing these (e.g. laptops, cell phones etc.). Among these countries and regions are Hong Kong,[111] Australia and Japan.[112]

 Research

Researchers are working to improve the power density, safety, recharge cycle, cost and other characteristics of these batteries.

Solid-state designs have the potential to deliver three times the energy density of typical 2011 lithium-ion batteries at less than half the cost per kilowatt-hour. This approach eliminates binders, separators, and liquid electrolytes. By eliminating these, "you can get around 95% of the theoretical energy density of the active materials."[113]

Earlier trials of this technology ran into cost barriers, because the semiconductor industry's vacuum deposition technology cost 20–30 times too much. The new process deposits semiconductor-quality films from a solution. The nanostructured films grow directly on a substrate and then sequentially on top of each other. The process allows the firm to "spray-paint a cathode, then a separator/electrolyte, then the anode. It can be cut and stacked in various form factors."[113]