131-432: A lithium-ion or Li-ion battery is a type of rechargeable battery that uses the reversible intercalation of Li ions into electronically conducting solids to store energy. In comparison with other commercial rechargeable batteries , Li-ion batteries are characterized by higher specific energy , higher energy density , higher energy efficiency , a longer cycle life , and a longer calendar life . Also noteworthy
262-419: A "20-hour" rate), while typical charging and discharging may occur at C/2 (two hours for full capacity). The available capacity of electrochemical cells varies depending on the discharge rate. Some energy is lost in the internal resistance of cell components (plates, electrolyte, interconnections), and the rate of discharge is limited by the speed at which chemicals in the cell can move about. For lead-acid cells,
393-437: A battery charger using AC mains electricity , although some are equipped to use a vehicle's 12-volt DC power outlet. The voltage of the source must be higher than that of the battery to force current to flow into it, but not too much higher or the battery may be damaged. Chargers take from a few minutes to several hours to charge a battery. Slow "dumb" chargers without voltage or temperature-sensing capabilities will charge at
524-550: A 1992 EPA Superfund report, lead batteries account for about 80% of the lead used in the United States, of which about 60% is reclaimed during times of low lead prices, but more in times of high lead prices; it reported that 50% of the nation's lead needs are filled from recycled lead. Used most frequently in watches, toys, and some medical devices , silver-oxide batteries contain a small amount of mercury . Most jurisdictions regulate their handling and disposal to reduce
655-413: A balancing circuit until the battery is balanced. Balancing typically occurs whenever one or more cells reach their top-of-charge voltage before the other(s), as it is generally inaccurate to do so at other stages of the charge cycle. This is most commonly done by passive balancing, which dissipates excess charge as heat via resistors connected momentarily across the cells to be balanced. Active balancing
786-621: A battery rather than to operate the radio directly. Flashlights may be driven by a dynamo directly. For transportation, uninterruptible power supply systems and laboratories, flywheel energy storage systems store energy in a spinning rotor for conversion to electric power when needed; such systems may be used to provide large pulses of power that would otherwise be objectionable on a common electrical grid. Ultracapacitors – capacitors of extremely high value – are also used; an electric screwdriver which charges in 90 seconds and will drive about half as many screws as
917-399: A battery. For some types, the maximum charging rate will be limited by the speed at which active material can diffuse through a liquid electrolyte. High charging rates may produce excess gas in a battery, or may result in damaging side reactions that permanently lower the battery capacity. Very roughly, and with many exceptions and caveats, restoring a battery's full capacity in one hour or less
1048-571: A battery. To avoid damage from the cell reversal effect, it is necessary to access each cell separately: each cell is individually discharged by connecting a load clip across the terminals of each cell, thereby avoiding cell reversal. If a multi-cell battery is fully discharged, it will often be damaged due to the cell reversal effect mentioned above. It is possible however to fully discharge a battery without causing cell reversal—either by discharging each cell separately, or by allowing each cell's internal leakage to dissipate its charge over time. Even if
1179-466: A cell is brought to a fully discharged state without reversal, however, damage may occur over time simply due to remaining in the discharged state. An example of this is the sulfation that occurs in lead-acid batteries that are left sitting on a shelf for long periods. For this reason it is often recommended to charge a battery that is intended to remain in storage, and to maintain its charge level by periodically recharging it. Since damage may also occur if
1310-418: A conventional lithium-ion cell is graphite made from carbon . The positive electrode is typically a metal oxide or phosphate. The electrolyte is a lithium salt in an organic solvent . The negative electrode (which is the anode when the cell is discharging) and the positive electrode (which is the cathode when discharging) are prevented from shorting by a separator. The electrodes are connected to
1441-551: A day. Shops that sell this amount must by law provide recycling facilities as of 1 February 2010. In Great Britain an increasing number of shops (Argos, Homebase, B&Q, Tesco, and Sainsbury's) are providing battery return boxes and cylinders for their customers. The rechargeable battery industry has formed the Rechargeable Battery Recycling Corporation (RBRC), which operates a battery recycling program called Call2Recycle throughout
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#17327768322991572-443: A device using a rechargeable battery was introduced in 2007, and similar flashlights have been produced. In keeping with the concept of ultracapacitors, betavoltaic batteries may be utilized as a method of providing a trickle-charge to a secondary battery, greatly extending the life and energy capacity of the battery system being employed; this type of arrangement is often referred to as a "hybrid betavoltaic power source" by those in
1703-428: A discharged cell in this way causes undesirable and irreversible chemical reactions to occur, resulting in permanent damage to the cell. Cell reversal can occur under a number of circumstances, the two most common being: In the latter case, the problem occurs due to the different cells in a battery having slightly different capacities. When one cell reaches discharge level ahead of the rest, the remaining cells will force
1834-413: A gelled material, requiring fewer binding agents. This in turn shortens the manufacturing cycle. One potential application is in battery-powered airplanes. Another new development of lithium-ion batteries are flow batteries with redox-targeted solids, that use no binders or electron-conducting additives, and allow for completely independent scaling of energy and power. Generally, the negative electrode of
1965-399: A higher discharge rate. NMC and its derivatives are widely used in the electrification of transport , one of the main technologies (combined with renewable energy ) for reducing greenhouse gas emissions from vehicles . M. Stanley Whittingham conceived intercalation electrodes in the 1970s and created the first rechargeable lithium-ion battery, based on a titanium disulfide cathode and
2096-467: A hybrid lead–acid battery and ultracapacitor invented by Australia's national science organisation CSIRO , exhibits tens of thousands of partial state of charge cycles and has outperformed traditional lead-acid, lithium, and NiMH-based cells when compared in testing in this mode against variability management power profiles. UltraBattery has kW and MW-scale installations in place in Australia, Japan, and
2227-537: A hydrogen-absorbing alloy for the negative electrode instead of cadmium . The lithium-ion battery was introduced in the market in 1991, is the choice in most consumer electronics, having the best energy density and a very slow loss of charge when not in use. It does have drawbacks too, particularly the risk of unexpected ignition from the heat generated by the battery. Such incidents are rare and according to experts, they can be minimized "via appropriate design, installation, procedures and layers of safeguards" so
2358-403: A liquid solvent (such as propylene carbonate or diethyl carbonate ) is added. The electrolyte salt is almost always lithium hexafluorophosphate ( LiPF 6 ), which combines good ionic conductivity with chemical and electrochemical stability. The hexafluorophosphate anion is essential for passivating the aluminium current collector used for the positive electrode. A titanium tab
2489-503: A lithium-aluminium anode, although it suffered from safety problems and was never commercialized. John Goodenough expanded on this work in 1980 by using lithium cobalt oxide as a cathode. The first prototype of the modern Li-ion battery, which uses a carbonaceous anode rather than lithium metal, was developed by Akira Yoshino in 1985 and commercialized by a Sony and Asahi Kasei team led by Yoshio Nishi in 1991. M. Stanley Whittingham , John Goodenough , and Akira Yoshino were awarded
2620-523: A lithium-ion cell can change dramatically. Current effort has been exploring the use of novel architectures using nanotechnology to improve performance. Areas of interest include nano-scale electrode materials and alternative electrode structures. The reactants in the electrochemical reactions in a lithium-ion cell are the materials of the electrodes, both of which are compounds containing lithium atoms. Although many thousands of different materials have been investigated for use in lithium-ion batteries, only
2751-551: A long and stable lifetime. The effective number of cycles is above 5000 and the battery is not damaged by deep discharge. The energy density is rather low, somewhat lower than lead–acid. A rechargeable battery is only one of several types of rechargeable energy storage systems. Several alternatives to rechargeable batteries exist or are under development. For uses such as portable radios , rechargeable batteries may be replaced by clockwork mechanisms which are wound up by hand, driving dynamos , although this system may be used to charge
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#17327768322992882-450: A lot of people complied with the request to dispose of batteries responsibly. From April 2005 to March 2008, the UK non-governmental body WRAP conducted trials of collection methods for battery recycling around the UK. The methods tested were: Kerbside, retail drop-off, community drop-off, postal, and hospital and fire station trials. The kerbside trials collected the most battery mass, and were
3013-473: A low rate, typically taking 14 hours or more to reach a full charge. Rapid chargers can typically charge cells in two to five hours, depending on the model, with the fastest taking as little as fifteen minutes. Fast chargers must have multiple ways of detecting when a cell reaches full charge (change in terminal voltage, temperature, etc.) to stop charging before harmful overcharging or overheating occurs. The fastest chargers often incorporate cooling fans to keep
3144-520: A marked increase in motor vehicles, and a corresponding increase in lead-acid battery recycling. India lacks a formal planned recycling industry. The industry is not respected, and lacks designated zones for recycling. However, in a nation with a vast population of people still in poverty, most lead-acid battery recycling is by individuals and small informal enterprises, often taking no safety or environmental precautions. ILZDA has demanded multiple changes to India's industry and its regulation, including
3275-421: A method that refurbishes the cathode showed that this technique perform just as well as those with a cathode made from original materials. The study showed that the batteries using the recycled cathode charged faster and lasted longer than new batteries. By 2023, several companies had moved beyond research and had set up process lines to recycle commercial quantities of Li-ion batteries. In its Nevada pilot plant,
3406-888: A much lower total cost of ownership and environmental impact , as they can be recharged inexpensively many times before they need replacing. Some rechargeable battery types are available in the same sizes and voltages as disposable types, and can be used interchangeably with them. Billions of dollars in research are being invested around the world for improving batteries as industry focuses on building better batteries. Devices which use rechargeable batteries include automobile starters , portable consumer devices, light vehicles (such as motorized wheelchairs , golf carts , electric bicycles , and electric forklifts ), road vehicles (cars, vans, trucks, motorbikes), trains, small airplanes, tools, uninterruptible power supplies , and battery storage power stations . Emerging applications in hybrid internal combustion-battery and electric vehicles drive
3537-422: A non-aqueous electrolyte is typically used, and a sealed container rigidly excludes moisture from the battery pack. The non-aqueous electrolyte is typically a mixture of organic carbonates such as ethylene carbonate and propylene carbonate containing complexes of lithium ions. Ethylene carbonate is essential for making solid electrolyte interphase on the carbon anode, but since it is solid at room temperature,
3668-416: A number of heavy metals and toxic chemicals and disposing of them by the same process as regular household waste has raised concerns over soil contamination and water pollution . While reducing the amount of pollutants being released through disposal through the uses of landfill and incineration, battery recycling can facilitate the release of harmful materials from batteries to both the environment and
3799-447: A polymer gel as an electrolyte), a lithium cobalt oxide ( LiCoO 2 ) cathode material, and a graphite anode, which together offer high energy density. Lithium iron phosphate ( LiFePO 4 ), lithium manganese oxide ( LiMn 2 O 4 spinel , or Li 2 MnO 3 -based lithium-rich layered materials, LMR-NMC), and lithium nickel manganese cobalt oxide ( LiNiMnCoO 2 or NMC) may offer longer life and
3930-444: A process called insertion ( intercalation ) or extraction ( deintercalation ), respectively. As the lithium ions "rock" back and forth between the two electrodes, these batteries are also known as "rocking-chair batteries" or "swing batteries" (a term given by some European industries). The following equations exemplify the chemistry (left to right: discharging, right to left: charging). The negative electrode half-reaction for
4061-528: A range of alternative materials, replaced TiS 2 with lithium cobalt oxide ( LiCoO 2 , or LCO), which has a similar layered structure but offers a higher voltage and is much more stable in air. This material would later be used in the first commercial Li-ion battery, although it did not, on its own, resolve the persistent issue of flammability. These early attempts to develop rechargeable Li-ion batteries used lithium metal anodes, which were ultimately abandoned due to safety concerns, as lithium metal
Lithium-ion battery - Misplaced Pages Continue
4192-437: A reducing agent. This is followed by selective precipitation of the metals as salts. Hydrometallurgical processes have several advantages, such as low energy consumption, low cost and little hazardous gas emission. However, the use of dangerous acids during extraction poses safety concerns. Additionally, the method requires extensive and complicated processing to selectively precipitate each metal salt. Pyrometallurgy involves
4323-482: A refundable deposit is paid on batteries. This encourages recycling of old batteries instead of abandonment or disposal with household waste. Businesses that sell new car batteries may also collect used batteries (or be required to do so by law) for recycling. A 2019 study commissioned by battery-industry promotional group, the Battery Council , calculated battery lead recycling rates in the United States in
4454-486: A regulated current source that tapers as the battery reaches fully charged voltage. Charging a battery incorrectly can damage a battery; in extreme cases, batteries can overheat, catch fire, or explosively vent their contents. Battery charging and discharging rates are often discussed by referencing a "C" rate of current. The C rate is that which would theoretically fully charge or discharge the battery in one hour. For example, trickle charging might be performed at C/20 (or
4585-483: A resistive voltage drop that is greater than the cell's forward emf . This results in the reversal of the cell's polarity while the current is flowing. The higher the required discharge rate of a battery, the better matched the cells should be, both in the type of cell and state of charge, in order to reduce the chances of cell reversal. In some situations, such as when correcting NiCd batteries that have been previously overcharged, it may be desirable to fully discharge
4716-427: A solid organic electrolyte, polyethylene oxide , which was more stable. In 1985, Akira Yoshino at Asahi Kasei Corporation discovered that petroleum coke , a less graphitized form of carbon, can reversibly intercalate Li-ions at a low potential of ~0.5 V relative to Li+ /Li without structural degradation. Its structural stability originates from its amorphous carbon regions, which serving as covalent joints to pin
4847-539: A temperature range of 5 to 45 °C (41 to 113 °F). Charging should be performed within this temperature range. At temperatures from 0 to 5 °C charging is possible, but the charge current should be reduced. During a low-temperature (under 0 °C) charge, the slight temperature rise above ambient due to the internal cell resistance is beneficial. High temperatures during charging may lead to battery degradation and charging at temperatures above 45 °C will degrade battery performance, whereas at lower temperatures
4978-540: A terminal voltage that does not decline rapidly until nearly exhausted. This terminal voltage drop complicates the design of power electronics for use with ultracapacitors. However, there are potential benefits in cycle efficiency, lifetime, and weight compared with rechargeable systems. China started using ultracapacitors on two commercial bus routes in 2006; one of them is route 11 in Shanghai . Flow batteries , used for specialized applications, are recharged by replacing
5109-520: A theoretical capacity of 1339 coulombs per gram (372 mAh/g). The positive electrode 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 ). More experimental materials include graphene -containing electrodes, although these remain far from commercially viable due to their high cost. Lithium reacts vigorously with water to form lithium hydroxide (LiOH) and hydrogen gas. Thus,
5240-976: A type of energy accumulator ), is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or primary battery , which is supplied fully charged and discarded after use. It is composed of one or more electrochemical cells . The term "accumulator" is used as it accumulates and stores energy through a reversible electrochemical reaction . Rechargeable batteries are produced in many different shapes and sizes, ranging from button cells to megawatt systems connected to stabilize an electrical distribution network . Several different combinations of electrode materials and electrolytes are used, including lead–acid , zinc–air , nickel–cadmium (NiCd), nickel–metal hydride (NiMH), lithium-ion (Li-ion), lithium iron phosphate (LiFePO4), and lithium-ion polymer (Li-ion polymer). Rechargeable batteries typically initially cost more than disposable batteries but have
5371-514: A very small number are commercially usable. All commercial Li-ion cells use intercalation compounds as active materials. The negative electrode is usually graphite , although silicon is often mixed in to increase the capacity. The electrolyte is usually lithium hexafluorophosphate , dissolved in a mixture of organic carbonates . A number of different materials are used for the positive electrode, such as LiCoO 2 , LiFePO 4 , and lithium nickel manganese cobalt oxides . During cell discharge
Lithium-ion battery - Misplaced Pages Continue
5502-578: Is "lost" during battery use and restore the cathode to its original capacity. This relithiation process can be carried out via several different methods, including solid state, electrochemical, or solution-based relithiation. While direct recycling is not yet commercialized, research indicates that it can restore cathode materials to their original electrochemical capacity and performance. Specific dangers associated with lithium-ion battery recycling processes include electrical, chemical, and thermal dangers, and their potential interactions. A complicating factor
5633-440: Is a CuF 2 /Li battery developed by NASA in 1965. The breakthrough that produced the earliest form of the modern Li-ion battery was made by British chemist M. Stanley Whittingham in 1974, who first used titanium disulfide ( TiS 2 ) as a cathode material, which has a layered structure that can take in lithium ions without significant changes to its crystal structure . Exxon tried to commercialize this battery in
5764-417: Is a bit more than the heat of combustion of gasoline but does not consider the other materials that go into a lithium battery and that make lithium batteries many times heavier per unit of energy. Note that the cell voltages involved in these reactions are larger than the potential at which an aqueous solutions would electrolyze . During discharge, lithium ions ( Li ) carry the current within
5895-469: Is a dramatic improvement in lithium-ion battery properties after their market introduction in 1991: over the following 30 years, their volumetric energy density increased threefold while their cost dropped tenfold. There are at least 12 different chemistries of Li-ion batteries; see " List of battery types ." The invention and commercialization of Li-ion batteries may have had one of the greatest impacts of all technologies in human history , as recognized by
6026-416: Is a refinement of lithium ion technology by Excellatron. The developers claim a large increase in recharge cycles to around 40,000 and higher charge and discharge rates, at least 5 C charge rate. Sustained 60 C discharge and 1000 C peak discharge rate and a significant increase in specific energy , and energy density. lithium iron phosphate batteries are used in some applications. UltraBattery ,
6157-400: Is already in place for the product. The potassium-ion battery delivers around a million cycles, due to the extraordinary electrochemical stability of potassium insertion/extraction materials such as Prussian blue . The sodium-ion battery is meant for stationary storage and competes with lead–acid batteries. It aims at a low total cost of ownership per kWh of storage. This is achieved by
6288-569: Is commonly done informally by individuals or informal enterprises, with little or no formal record-keeping, nor effective regulatory oversight. Spent lead–acid batteries are generally designated as " hazardous waste " and subject to relevant safety, storage, handling and transport regulations, though those vary from country to country. A multilateral international agreement, the Basel Convention , officially governs all transboundary movements of hazardous waste for recovery or disposal, among
6419-413: Is considered fast charging. A battery charger system will include more complex control-circuit- and charging strategies for fast charging, than for a charger designed for slower recharging. The active components in a secondary cell are the chemicals that make up the positive and negative active materials, and the electrolyte . The positive and negative electrodes are made up of different materials, with
6550-449: Is five times more expensive than mined lithium. However, lithium extraction from Li-ion batteries has been demonstrated in small setups by various entities as well as in production scale by battery material recycling companies like Electra Battery Materials and Redwood Materials, Inc . A critical part of recycling economics is the value of the recovered cobalt. Manufacturers working to remove cobalt from their products might produce
6681-413: Is less common, more expensive, but more efficient, returning excess energy to other cells (or the entire pack) via a DC-DC converter or other circuitry. Balancing most often occurs during the constant voltage stage of charging, switching between charge modes until complete. The pack is usually fully charged only when balancing is complete, as even a single cell group lower in charge than the rest will limit
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#17327768322996812-427: Is no longer available to participate in the next discharge cycle. Sealed batteries may lose moisture from their liquid electrolyte, especially if overcharged or operated at high temperature. This reduces the cycling life. Recharging time is an important parameter to the user of a product powered by rechargeable batteries. Even if the charging power supply provides enough power to operate the device as well as recharge
6943-459: Is recommended to be initiated when voltage goes below 4.05 V/cell. Failure to follow current and voltage limitations can result in an explosion. Charging temperature limits for Li-ion are stricter than the operating limits. Lithium-ion chemistry performs well at elevated temperatures but prolonged exposure to heat reduces battery life. Li‑ion batteries offer good charging performance at cooler temperatures and may even allow "fast-charging" within
7074-478: Is the water sensitivity: lithium hexafluorophosphate , a possible electrolyte material, reacts with water to form hydrofluoric acid ; cells are often immersed in a solvent to prevent this. Once removed, the jelly rolls are separated and the materials removed by ultrasonic agitation , leaving the electrodes ready for melting and recycling. Pouch cells are easier to recycle to salvage copper despite significant safety issues. Extraction of lithium from old batteries
7205-409: Is ultrasonically welded to the aluminium current collector. Other salts like lithium perchlorate ( LiClO 4 ), lithium tetrafluoroborate ( LiBF 4 ), and lithium bis(trifluoromethanesulfonyl)imide ( LiC 2 F 6 NO 4 S 2 ) are frequently used in research in tab-less coin cells , but are not usable in larger format cells, often because they are not compatible with
7336-399: Is unable to recover lithium from the slag. Direct recycling is an emerging battery recycling method that focuses on directly regenerating cathode materials without damaging the crystal structure . This is distinct from existing hydro- and pyrometallurgical methods, which break down the cathode into precursors and require subsequent processing to regenerate cathode materials. Maintaining
7467-535: Is unstable and prone to dendrite formation, which can cause short-circuiting . The eventual solution was to use an intercalation anode, similar to that used for the cathode, which prevents the formation of lithium metal during battery charging. The first to demonstrate lithium ion reversible intercalation into graphite anodes was Jürgen Otto Besenhard in 1974. Besenhard used organic solvents such as carbonates, however these solvents decomposed rapidly providing short battery cycle life. Later, in 1980, Rachid Yazami used
7598-627: The Japan Portable Rechargeable Battery Recycling Center (JBRC) was created to handle and promote battery recycling throughout Japan. They provide battery recycling containers to shops and other collection points. India is one of the world's chief consumers of lead–acid batteries, according to the India Lead Zinc Development Association (ILZDA). India, with its recent rapid rise in average wealth, has seen
7729-796: The Redwood Materials process had recovered more than 95% of important metals (including lithium, cobalt, nickel and copper) from 230,000 kg (500,000 lb) of old NiMH and Li-Ion packs. Italics designates button cell types. Bold designates secondary types. All figures are percentages; due to rounding they may not add up to exactly 100. Battery recycling is an international industry, with many nations exporting their used or spent lead-acid batteries to other nations for recycling. Consequently, it can be difficult to get accurate analyses of individual nations' exact rate of domestic recycling. Further, in many countries, lead-acid battery recycling (chiefly from automobiles and motorcycles)
7860-401: The constant current phase, the charger applies a constant current to the battery at a steadily increasing voltage, until the top-of-charge voltage limit per cell is reached. During the balance phase, the charger/battery reduces the charging current (or cycles the charging on and off to reduce the average current) while the state of charge of individual cells is brought to the same level by
7991-654: The 172 signatory countries. (The U.S. is not a party, but has alternate arrangements with the Organisation for Economic Co-operation and Development (OECD), and with Canada and with Mexico (where it ships many lead-acid batteries for recycling ). Figures for Q1 and Q2 2012. In 2006, the European Union passed the Battery Directive , one of the aims of which is a higher rate of battery recycling. The EU directive states that at least 25% of all
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#17327768322998122-732: The 2019 Nobel Prize in Chemistry "for the development of lithium-ion batteries". Jeff Dahn received the ECS Battery Division Technology Award (2011) and the Yeager award from the International Battery Materials Association (2016). In April 2023, CATL announced that it would begin scaled-up production of its semi-solid condensed matter battery that produces a then record 500 Wh/kg . They use electrodes made from
8253-481: The 2019 Nobel Prize in Chemistry . More specifically, Li-ion batteries enabled portable consumer electronics , laptop computers , cellular phones , and electric cars , or what has been called the e-mobility revolution. It also sees significant use for grid-scale energy storage as well as military and aerospace applications. Lithium-ion cells can be manufactured to optimize energy or power density. Handheld electronics mostly use lithium polymer batteries (with
8384-475: The 2019 Nobel Prize in Chemistry for their contributions to the development of lithium-ion batteries. Lithium-ion batteries can be a safety hazard if not properly engineered and manufactured because they have flammable electrolytes that, if damaged or incorrectly charged, can lead to explosions and fires. Much progress has been made in the development and manufacturing of safe lithium-ion batteries. Lithium-ion solid-state batteries are being developed to eliminate
8515-553: The EU's used batteries must be collected by 2012, and rising to no less than 45% by 2016, of which at least 50% must be recycled. In 2020, 47% of batteries in the EU were collected for recycling. In early 2009, Guernsey took the initiative by setting up the Longue Hougue recycling facility, which, among other functions, offers a drop-off point for used batteries so they can be recycled off-island. The resulting publicity meant that
8646-479: The U.S. It has also been subjected to extensive testing in hybrid electric vehicles and has been shown to last more than 100,000 vehicle miles in on-road commercial testing in a courier vehicle. The technology is claimed to have a lifetime of 7 to 10 times that of conventional lead-acid batteries in high rate partial state-of-charge use, with safety and environmental benefits claimed over competitors like lithium-ion. Its manufacturer suggests an almost 100% recycling rate
8777-683: The USA in that period, with a net amount of approximately 2 billion pounds battery scrap lead being exported. Of the 13.6 billion pounds remaining after exports, 13.5 billion pounds were recycled. The U.S. Environmental Protection Agency (EPA), has reported lesser and varying levels of lead-acid battery recycling in the United States in earlier years, under various administrations, Republican and Democrat. The EPA reported in 1987 that varying economics and regulatory requirements have contributed to rates of 97 percent in 1965, above 83 percent in 1980, 61 percent in 1983, and around 70 percent in 1985. According to
8908-672: The United States and Canada. RBRC provides businesses with prepaid shipping containers for rechargeable batteries of all types while consumers can drop off batteries at numerous participating collection centers. It claims that no component of any recycled battery eventually reaches a landfill. Other programs, such as the Big Green Box program, offer a recycling option for all chemistries, including primary batteries such as alkaline and primary lithium. A study estimated battery recycling rates in Canada based on RBRC data. In 2002, it wrote,
9039-437: The United States are increasingly being transported to Mexico for recycling as a result of a widening gap between the strictness of environmental and labor regulations between the two countries. In 2015, Energizer announced availability of disposable AAA and AA alkaline batteries made with 3.8% to 4% (by weight) of recycled batteries, branded as EcoAdvanced. Japan does not have a single national battery recycling law, so
9170-449: The [RBRC] program for all end of life small sealed lead acid (SLA) consumer batteries were estimated at 10% for 5-year and 15-year hoarding assumptions. [...] It should also be stressed that these figures do not take collection of secondary consumer batteries through other sources into account, and actual collection rates are likely higher than these values." A November 2011 The New York Times article reported that batteries collected in
9301-604: The acid, and separating the polymers from the lead. The recovered materials are used in a variety of applications, including new batteries. The lead in a lead–acid battery can be recycled. Elemental lead is toxic and should therefore be kept out of the waste stream. The casing of a lead–acid battery is often made of either polypropylene or ABS , which can also be recycled, although there are significant limitations on recycling plastics . Many cities offer battery recycling services for lead–acid batteries. In some jurisdictions, including U.S. states and Canadian provinces ,
9432-536: The active material, they may also contain cobalt and nickel . To prevent a future shortage of cobalt, nickel, and lithium and to enable a sustainable life cycle of these technologies, recycling processes for lithium batteries are needed. These processes have to regain not only cobalt , nickel , copper , and aluminium from spent battery cells, but also a significant share of lithium. Other potentially valuable and recoverable materials are graphite and manganese. Recycling processes today recover approximately 25% to 96% of
9563-437: The advice given is to follow local and regional statutes and codes in disposing batteries. The Battery Association of Japan (BAJ) recommends that alkaline, zinc-carbon, and lithium primary batteries can be disposed of as normal household waste. The BAJ's stance on button cell and secondary batteries is toward recycling and increasing national standardisation of procedures for dealing with these types of batteries. In April 2004,
9694-433: The aluminium current collector. Copper (with a spot-welded nickel tab) is used as the current collector at the negative electrode. Current collector design and surface treatments may take various forms: foil, mesh, foam (dealloyed), etched (wholly or selectively), and coated (with various materials) to improve electrical characteristics. Depending on materials choices, the voltage , energy density , life, and safety of
9825-623: The anode. Energy saving and effective recycling solutions for lithium-ion batteries can reduce the carbon footprint of the production of lithium-ion batteries significantly. As of 2022 , several facilities are operating and under construction, including Fredrikstad in Norway and a black mass facility in Magdeburg , Germany in 2023. In early 2022, research published in Joule showed that recycling existing lithium-ion batteries by focusing on
9956-412: The area of non-flammable electrolytes as a pathway to increased safety based on the flammability and volatility of the organic solvents used in the typical electrolyte. Strategies include aqueous lithium-ion batteries , ceramic solid electrolytes, polymer electrolytes, ionic liquids, and heavily fluorinated systems. Research on rechargeable Li-ion batteries dates to the 1960s; one of the earliest examples
10087-414: The battery cell from the negative to the positive electrode, through the non- aqueous electrolyte and separator diaphragm. During charging, an external electrical power source applies an over-voltage (a voltage greater than the cell's own voltage) to the cell, forcing electrons to flow from the positive to the negative electrode. The lithium ions also migrate (through the electrolyte) from the positive to
10218-527: The battery is not constant during charging and discharging. Some types have relatively constant voltage during discharge over much of their capacity. Non-rechargeable alkaline and zinc–carbon cells output 1.5 V when new, but this voltage drops with use. Most NiMH AA and AAA cells are rated at 1.2 V, but have a flatter discharge curve than alkalines and can usually be used in equipment designed to use alkaline batteries . Battery manufacturers' technical notes often refer to voltage per cell (VPC) for
10349-404: The battery is overcharged, the optimal level of charge during storage is typically around 30% to 70%. Depth of discharge (DOD) is normally stated as a percentage of the nominal ampere-hour capacity; 0% DOD means no discharge. As the usable capacity of a battery system depends on the rate of discharge and the allowable voltage at the end of discharge, the depth of discharge must be qualified to show
10480-457: The battery, the device is attached to an external power supply during the charging time. For electric vehicles used industrially, charging during off-shifts may be acceptable. For highway electric vehicles, rapid charging is necessary for charging in a reasonable time. A rechargeable battery cannot be recharged at an arbitrarily high rate. The internal resistance of the battery will produce heat, and excessive temperature rise will damage or destroy
10611-422: The cathode structure represents an important increase in efficiency, since it produces a higher-value product than other recycling methods. In order to perform direct recycling, the cathode "black mass" (containing critical metals such as Li, Co, Mn, and Ni) must be separated from other battery components. Traditional separation methods, primarily battery shredding, are insufficient, as they introduce impurities into
10742-437: The cathode. Alternative separation methods include the use of solvents to recover the black mass. Many of the organic solvents investigated for this process are toxic and pose hazards to both humans and the environment. Identifying safer solvents which can effectively separate the black mass is a topic of current research. Once the cathode black mass is obtained, the material undergoes relithiation to reintroduce lithium which
10873-404: The cells from overheating. Battery packs intended for rapid charging may include a temperature sensor that the charger uses to protect the pack; the sensor will have one or more additional electrical contacts. Different battery chemistries require different charging schemes. For example, some battery types can be safely recharged from a constant voltage source. Other types need to be charged with
11004-526: The collection rate was 3.2%. This implies that 3.2% of rechargeable batteries were recycled, and the rest were thrown in the trash. By 2005, it concluded, the collection rate had risen to 5.6%. In 2009, Kelleher Environmental updated the study. The update estimates the following. "Collection rate values for the 5 [and] 15-year hoarding assumptions respectively are: 8% to 9% for NiCd batteries; 7% to 8% for NiMH batteries; and 45% to 72% for lithium ion and lithium polymer batteries combined. Collection rates through
11135-414: The current through the discharged cell. Many battery-operated devices have a low-voltage cutoff that prevents deep discharges from occurring that might cause cell reversal. A smart battery has voltage monitoring circuitry built inside. Cell reversal can occur to a weakly charged cell even before it is fully discharged. If the battery drain current is high enough, the cell's internal resistance can create
11266-660: The day to be used at night). Load-leveling reduces the maximum power which a plant must be able to generate, reducing capital cost and the need for peaking power plants . According to a report from Research and Markets, the analysts forecast the global rechargeable battery market to grow at a CAGR of 8.32% during the period 2018–2022. Small rechargeable batteries can power portable electronic devices , power tools, appliances, and so on. Heavy-duty batteries power electric vehicles , ranging from scooters to locomotives and ships . They are used in distributed electricity generation and in stand-alone power systems . During charging,
11397-466: The discharge of mercury into the environment. Silver oxide batteries can be recycled to recover the mercury through the use of both Hydrometallurgical methods and pyrometallurgical methods. More recent silver oxide batteries no longer contain mercury and the process of recycling them does not give cause for concern for releasing mercury into the environment. Lithium-ion batteries contain lithium and high-grade copper and aluminium . Depending on
11528-430: The electrolyte liquid. A flow battery can be considered to be a type of rechargeable fuel cell . Rechargeable battery research includes development of new electrochemical systems as well as improving the life span and capacity of current types. Battery recycling Battery recycling is a recycling activity that aims to reduce the number of batteries being disposed as municipal solid waste . Batteries contain
11659-511: The entire battery's usable capacity to that of its own. Balancing can last hours or even days, depending on the magnitude of the imbalance in the battery. During the constant voltage phase, the charger applies a voltage equal to the maximum cell voltage times the number of cells in series to the battery, as the current gradually declines towards 0, until the current is below a set threshold of about 3% of initial constant charge current. Periodic topping charge about once per 500 hours. Top charging
11790-419: The external circuit toward the cathode where they recombine with the cathode material in a reduction half-reaction. The electrolyte provides a conductive medium for lithium ions but does not partake in the electrochemical reaction. The reactions during discharge lower the chemical potential of the cell, so discharging transfers energy from the cell to wherever the electric current dissipates its energy, mostly in
11921-481: The external circuit. During charging these reactions and transports go in the opposite direction: electrons move from the positive electrode to the negative electrode through the external circuit. To charge the cell the external circuit has to provide electrical energy. This energy is then stored as chemical energy in the cell (with some loss, e. g., due to coulombic efficiency lower than 1). Both electrodes allow lithium ions to move in and out of their structures with
12052-861: The flammable electrolyte. Improperly recycled batteries can create toxic waste, especially from toxic metals, and are at risk of fire. Moreover, both lithium and other key strategic minerals used in batteries have significant issues at extraction, with lithium being water intensive in often arid regions and other minerals used in some Li-ion chemistries potentially being conflict minerals such as cobalt . Both environmental issues have encouraged some researchers to improve mineral efficiency and find alternatives such as Lithium iron phosphate lithium-ion chemistries or non-lithium-based battery chemistries like iron-air batteries . Research areas for lithium-ion batteries include extending lifetime, increasing energy density, improving safety, reducing cost, and increasing charging speed, among others. Research has been under way in
12183-466: The graphite is The positive electrode half-reaction in the lithium-doped cobalt oxide substrate is The full reaction being The overall reaction has its limits. Overdischarging supersaturates lithium cobalt oxide , leading to the production of lithium oxide , possibly by the following irreversible reaction: Overcharging up to 5.2 volts leads to the synthesis of cobalt (IV) oxide, as evidenced by x-ray diffraction : The transition metal in
12314-459: The individual cells that make up the battery. For example, to charge a 12 V lead-acid battery (containing 6 cells of 2 V each) at 2.3 VPC requires a voltage of 13.8 V across the battery's terminals. Subjecting a discharged cell to a current in the direction which tends to discharge it further to the point the positive and negative terminals switch polarity causes a condition called cell reversal . Generally, pushing current through
12445-417: The industry. Ultracapacitors are being developed for transportation, using a large capacitor to store energy instead of the rechargeable battery banks used in hybrid vehicles . One drawback of capacitors compared to batteries is that the terminal voltage drops rapidly; a capacitor that has 25% of its initial energy left in it will have one-half of its initial voltage. By contrast, battery systems tend to have
12576-439: The internal resistance of the battery may increase, resulting in slower charging and thus longer charging times. Batteries gradually self-discharge even if not connected and delivering current. Li-ion rechargeable batteries have a self-discharge rate typically stated by manufacturers to be 1.5–2% per month. The rate increases with temperature and state of charge. A 2004 study found that for most cycling conditions self-discharge
12707-495: The joint program is to advance environment protection and sustainability. Despite the positive outlooks on battery recycling, negative effects also have been shown to impact developing nations that recycle batteries, especially those with lead and lithium. Lead is a highly toxic substance, and processing it can result in pollution and contamination of people, resulting in long-term health problems and even disability. According to one ranking, lead-acid battery recycling is, by far,
12838-560: The late 1970s, but found the synthesis expensive and complex, as TiS 2 is sensitive to moisture and releases toxic H 2 S gas on contact with water. More prohibitively, the batteries were also prone to spontaneously catch fire due to the presence of metallic lithium in the cells. For this, and other reasons, Exxon discontinued the development of Whittingham's lithium-titanium disulfide battery. In 1980, working in separate groups Ned A. Godshall et al., and, shortly thereafter, Koichi Mizushima and John B. Goodenough , after testing
12969-435: The layers together. Although it has a lower capacity compared to graphite (~Li0.5C6, 186 mAh g–1), it became the first commercial intercalation anode for Li-ion batteries owing to its cycling stability. In 1987, Yoshino patented what would become the first commercial lithium-ion battery using this anode. He used Goodenough's previously reported LiCoO 2 as the cathode and a carbonate ester -based electrolyte. The battery
13100-586: The low cost, makes it attractive for use in motor vehicles to provide the high current required by automobile starter motors . The nickel–cadmium battery (NiCd) was invented by Waldemar Jungner of Sweden in 1899. It uses nickel oxide hydroxide and metallic cadmium as electrodes . Cadmium is a toxic element, and was banned for most uses by the European Union in 2004. Nickel–cadmium batteries have been almost completely superseded by nickel–metal hydride (NiMH) batteries. The nickel–iron battery (NiFe)
13231-440: The materials of a lithium-ion battery cell. In order to achieve this goal, several steps are combined into complex process chains, while ensuring safety. These steps are: One or more of these metal recovery processes are used to recover critical metals from battery waste. In hydrometallurgical methods, metals are first extracted in aqueous solution, typically using acids (such as sulfuric acid ) and hydrogen peroxide as
13362-429: The most well-received and understood by the public. The community drop-off containers that were spread around local community areas were also relatively successful in terms of mass of batteries collected. The lowest performing were the hospital and fire service trials (although these served their purpose very well for specialized battery types like hearing aid and smoke alarm batteries). Retail drop off trials were by volume
13493-428: The negative electrode is the anode and the positive electrode the cathode : electrons flow from the anode to the cathode through the external circuit. An oxidation half-reaction at the anode produces positively charged lithium ions and negatively charged electrons. The oxidation half-reaction may also produce uncharged material that remains at the anode. Lithium ions move through the electrolyte; electrons move through
13624-475: The negative electrode where they become embedded in the porous electrode material in a process known as intercalation . Energy losses arising from electrical contact resistance at interfaces between electrode layers and at contacts with current collectors can be as high as 20% of the entire energy flow of batteries under typical operating conditions. The charging procedures for single Li-ion cells, and complete Li-ion batteries, are slightly different: During
13755-500: The number of charge cycles increases, until they are eventually considered to have reached the end of their useful life. Different battery systems have differing mechanisms for wearing out. For example, in lead-acid batteries, not all the active material is restored to the plates on each charge/discharge cycle; eventually enough material is lost that the battery capacity is reduced. In lithium-ion types, especially on deep discharge, some reactive lithium metal can be formed on charging, which
13886-446: The overall sustainability of lithium-ion batteries. Studies have found that components such as the battery casing, current collectors, electrolyte , and separators have potential to be recycled given further research into processing methods. In addition, recycling anode materials (primarily graphite) could significantly increase the recovery of lithium from spent batteries, since much of the lithium "lost" during battery use ends up in
14017-461: The period 2014–2018, taking into account battery scrap lead import/export data from the Department of Commerce . The report says that, after accounting for net scrap battery lead exports from the United States, 99.0% of the remaining lead from lead-acid batteries in the United States is reclaimed. The Battery Council figures indicate that around 15.5 billion pounds of battery lead was consumed in
14148-510: The positive active material is oxidized , releasing electrons , and the negative material is reduced , absorbing electrons. These electrons constitute the current flow in the external circuit . The electrolyte may serve as a simple buffer for internal ion flow between the electrodes , as in lithium-ion and nickel-cadmium cells, or it may be an active participant in the electrochemical reaction, as in lead–acid cells. The energy used to charge rechargeable batteries usually comes from
14279-467: The positive electrode is the cathode on discharge and the anode on charge, and vice versa for the negative electrode. The lead–acid battery , invented in 1859 by French physicist Gaston Planté , is the oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, its ability to supply high surge currents means that the cells have a relatively large power-to-weight ratio . These features, along with
14410-410: The positive electrode, cobalt ( Co ), is reduced from Co to Co during discharge, and oxidized from Co to Co during charge. The cell's energy is equal to the voltage times the charge. Each gram of lithium represents Faraday's constant /6.941, or 13,901 coulombs. At 3 V, this gives 41.7 kJ per gram of lithium, or 11.6 kWh per kilogram of lithium. This
14541-532: The positive exhibiting a reduction potential and the negative having an oxidation potential. The sum of the potentials from these half-reactions is the standard cell potential or voltage . In primary cells the positive and negative electrodes are known as the cathode and anode , respectively. Although this convention is sometimes carried through to rechargeable systems—especially with lithium-ion cells, because of their origins in primary lithium cells—this practice can lead to confusion. In rechargeable cells
14672-431: The powered circuit through two pieces of metal called current collectors. The negative and positive electrodes swap their electrochemical roles ( anode and cathode ) when the cell is charged. Despite this, in discussions of battery design the negative electrode of a rechargeable cell is often just called "the anode" and the positive electrode "the cathode". In its fully lithiated state of LiC 6 , graphite correlates to
14803-454: The presence of ethylene carbonate solvent (which is solid at room temperature and is mixed with other solvents to make a liquid). This represented the final innovation of the era that created the basic design of the modern lithium-ion battery. In 2010, global lithium-ion battery production capacity was 20 gigawatt-hours. By 2016, it was 28 GWh, with 16.4 GWh in China. Global production capacity
14934-483: The range of 150–260 Wh/kg, batteries based on lithium-sulfur are expected to achieve 450–500 Wh/kg, and can eliminate cobalt, nickel and manganese from the production process. Furthermore, while initially lithium-sulfur batteries suffered from stability problems, recent research has made advances in developing lithium-sulfur batteries that cycle as long as (or longer than) batteries based on conventional lithium-ion technologies. The thin-film battery (TFB)
15065-550: The registration of all battery dealers, and the collection of their returns, and recognition of the best-registered recyclers, while enforcing punishments for violators of government regulations. Two of India's largest lead companies—lead manufacturer/exporter Gravita India and lead battery manufacturer Amara Raja—partnered to annually recycle 8,000 tonnes of lead scrap from Amara Raja's facilities, and return it to them for re-use (Gravita said it can recycle and process up to 50,000 tonnes of lead and aluminium yearly). The companies said
15196-461: The relationship between time and discharge rate is described by Peukert's law ; a lead-acid cell that can no longer sustain a usable terminal voltage at a high current may still have usable capacity, if discharged at a much lower rate. Data sheets for rechargeable cells often list the discharge capacity on 8-hour or 20-hour or other stated time; cells for uninterruptible power supply systems may be rated at 15-minute discharge. The terminal voltage of
15327-593: The risk is acceptable. Lithium-ion polymer batteries (LiPo) are light in weight, offer slightly higher energy density than Li-ion at slightly higher cost, and can be made in any shape. They are available but have not displaced Li-ion in the market. A primary use is for LiPo batteries is in powering remote-controlled cars, boats and airplanes. LiPo packs are readily available on the consumer market, in various configurations, up to 44.4 V, for powering certain R/C vehicles and helicopters or drones. Some test reports warn of
15458-595: The risk of fire when the batteries are not used in accordance with the instructions. Independent reviews of the technology discuss the risk of fire and explosion from lithium-ion batteries under certain conditions because they use liquid electrolytes. ‡ citations are needed for these parameters Several types of lithium–sulfur battery have been developed, and numerous research groups and organizations have demonstrated that batteries based on lithium sulfur can achieve superior energy density to other lithium technologies. Whereas lithium-ion batteries offer energy density in
15589-485: The second most effective method but one of the least well received and used by the public. Both the kerbside and postal trials received the highest awareness and community support. Household batteries can be recycled in the UK at council recycling sites as well as at some shops and shopping centers, e.g. Currys, and The Link . A scheme started in 2008 by Sainsbury's allowed household batteries to be posted free of charge in envelopes available at their shops. This scheme
15720-405: The smelting of battery materials, followed by hydrometallurgical extraction to obtain metal salts from the slag. Pyrometallurgy has advantages such as flexibility in battery feedstock and simpler pretreatment methods. However, extremely high temperatures are required for smelting, giving pyrometallurgy a relatively high carbon footprint. This method also requires extensive processing of the slag, and
15851-596: The technology to reduce cost, weight, and size, and increase lifetime. Older rechargeable batteries self-discharge relatively rapidly and require charging before first use; some newer low self-discharge NiMH batteries hold their charge for many months, and are typically sold factory-charged to about 70% of their rated capacity. Battery storage power stations use rechargeable batteries for load-leveling (storing electric energy at times of low demand for use during peak periods) and for renewable energy uses (such as storing power generated from photovoltaic arrays during
15982-426: The unintended consequence of reducing recycling. A novel approach is to maintain the cathode's crystalline structure, eliminating the significant energy expense of recreating it. Another approach is to use ultrasound for separating the individual cathode components. While cathode materials are the focus of most recycling efforts due to their high economic value, recycling additional battery components could improve
16113-827: The vast majority of consumer battery use, but there is currently no cost-neutral recycling option. Consumer disposal guidelines vary by region. An evaluation of consumer alkaline battery recycling in Europe showed environmental benefit but at significant expense over disposal. Zinc–carbon and Zinc–air batteries are recycled in the same process. E.U. consumers recycled almost half of portable batteries bought in 2017. Lead-acid batteries include but are not limited to: car batteries , golf cart batteries, UPS batteries, industrial fork-lift batteries, motorcycle batteries, and commercial batteries. These can be regular lead–acid , sealed lead–acid, gel type , or absorbent glass mat batteries. These are recycled by grinding them, neutralizing
16244-582: The way it is to be measured. Due to variations during manufacture and aging, the DOD for complete discharge can change over time or number of charge cycles . Generally a rechargeable battery system will tolerate more charge/discharge cycles if the DOD is lower on each cycle. Lithium batteries can discharge to about 80 to 90% of their nominal capacity. Lead-acid batteries can discharge to about 50–60%. While flow batteries can discharge 100%. If batteries are used repeatedly even without mistreatment, they lose capacity as
16375-465: The workers recycling batteries. Most types of batteries can be recycled. However, some batteries are recycled more readily than others, such as lead–acid automotive batteries (nearly 90% are recycled) and button cells (because of the value and toxicity of their chemicals). Rechargeable nickel–cadmium (NiCd), nickel–metal hydride battery (NiMH) , lithium-ion (Li-ion) and nickel–zinc (NiZn), can also be recycled. Disposable alkaline batteries make up
16506-417: Was 767 GWh in 2020, with China accounting for 75%. Production in 2021 is estimated by various sources to be between 200 and 600 GWh, and predictions for 2023 range from 400 to 1,100 GWh. In 2012, John B. Goodenough , Rachid Yazami and Akira Yoshino received the 2012 IEEE Medal for Environmental and Safety Technologies for developing the lithium-ion battery; Goodenough, Whittingham, and Yoshino were awarded
16637-420: Was also developed by Waldemar Jungner in 1899; and commercialized by Thomas Edison in 1901 in the United States for electric vehicles and railway signalling . It is composed of only non-toxic elements, unlike many kinds of batteries that contain toxic mercury, cadmium, or lead. The nickel–metal hydride battery (NiMH) became available in 1989. These are now a common consumer and industrial type. The battery has
16768-629: Was assembled in the discharged state, which made it safer and cheaper to manufacture. In 1991, using Yoshino's design, Sony began producing and selling the world's first rechargeable lithium-ion batteries. The following year, a joint venture between Toshiba and Asashi Kasei Co. also released a lithium-ion battery. Significant improvements in energy density were achieved in the 1990s by replacing Yoshino's soft carbon anode first with hard carbon and later with graphite. In 1990, Jeff Dahn and two colleagues at Dalhousie University (Canada) reported reversible intercalation of lithium ions into graphite in
16899-464: Was cancelled at the request of the Royal Mail because of hazardous industrial battery waste being sent as well as household batteries. From 1 February 2010, batteries can be recycled anywhere the "Be Positive" sign appears. Shops and online retailers that sell more than 32 kilograms of batteries a year must offer facilities to recycle batteries. This is equivalent to one pack of four AA batteries
17030-457: Was estimated at 2% to 3%, and 2–3% by 2016. By comparison, the self-discharge rate for NiMH batteries dropped, as of 2017, from up to 30% per month for previously common cells to about 0.08–0.33% per month for low self-discharge NiMH batteries, and is about 10% per month in NiCd batteries . Rechargeable battery A rechargeable battery , storage battery , or secondary cell (formally
17161-481: Was primarily time-dependent; however, after several months of stand on open circuit or float charge, state-of-charge dependent losses became significant. The self-discharge rate did not increase monotonically with state-of-charge, but dropped somewhat at intermediate states of charge. Self-discharge rates may increase as batteries age. In 1999, self-discharge per month was measured at 8% at 21 °C, 15% at 40 °C, 31% at 60 °C. By 2007, monthly self-discharge rate
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