The lithium-ion batteries or Li-ion battery is rechargeable through the actions of lithium ions. These move from the negative electrode to the positive during discharge, and backwards again as they recharge.
As opposed to non-chargeable Li-ion batteries, which use metallic lithium, rechargeable ones use intercalated lithium compounds.
A Short History Of The Invention And Development Of The Li-ion Battery
The idea for the first Li-ion battery was proposed by Stanley Whittingham during the 1970s. At the time, the British scientist was working for Exxon and he used titanium sulfide and lithium metal as the electrodes. Titanium disulfide proved to be impractical, since it needed to be produced under completely sealed conditions, and the price of the raw materials was prohibitive.
Exxon discontinued the production of the battery because of this and also took into consideration that, when exposed to air, titanium disulfide reacts to form hydrogen sulfide compounds, which are toxic and have an unpleasant odor.
Since metallic lithium presented safety issues for use in batteries, research moved toward lithium only compounds that are capable of accepting and releasing lithium ions. Researchers worked at the development of electrode materials for lithium ion rechargeable batteries between 1973 and 1996 and their efforts were concentrated on two main trends. One was concentrated on graphite intercalation compounds through the field of electrochemistry, while the second was from the field of new nano-carbonaceous materials.
During the early 1980s, a polyacenic semi conductive material (PAS) was discovered by Tokio Yamabe, which was later improved by Shjzukuni Yata. Another development that helped the process was the discovery of conductive polymers, made by Professor Hideki Shiakawa and his team and then Alan MacDiarmid and Alan J. Heeger and their team developed the polyacetylene lithium ion battery.
A History Of The Commercial Production Of The Li-ion Battery
⦁ 1991 – the first commercial battery is released by Sony and Asahi Kasei
⦁ 1996 – Lithium iron phosphate (LFP) and other phosphor-olivines are proposed as positive electrode materials by John Goodenough, Akshaya Padhi and others.
⦁ 2001 – Lithium nickel manganese cobalt oxide (NMC) is patented by Zhonghua Lu and Jeff Dahn. This material offers safety and energy density improvements to the lithium cobalt oxide, widely used until then.
⦁ 2002 – By doping the materials for lithium batteries with aluminium, niobium and zirconium, Yet-Ming Chiang and his team at MIT, manage to increase their performance substantially and cause an extensive debate among scientists.
⦁ 2004 – With the rapid growth of the Li-ion battery market, a patent infringement battle breaks out between Chiang and Goodenough. In the meantime Chiang discovers that by utilizing nano lithium iron (II) phosphate particles, the particle density decreases hundredfold, and improves the capacity and performance of the battery through an increased positive electrode surface.
⦁ 2011 – Rechargeable batteries make up for 66% of all battery sales in Japan.
⦁ 2012 – The IEEE Medal for Environmental and Safety Technologies goes to John Goodenough, Rachid Yazami and Akira Yoshino for developing the lithium ion battery.
⦁ 2014 – Amprius Corp. uses a silicon anode which increases the capacity of the batteries by 20% to 650 Wh/L.
John Goodenough, Yoshio Nishi, Rachid Yazami and Akira Yoshino are all recognized for their pioneering efforts in the field by The National Academy of Engineering.
By 2016, global lithium-ion battery production capacity was at 28 gigawatt-hours, of which, 16.4GWh was in China.
Uses For The Li-ion Batteries
There are other rechargeable batteries on the market, namely, the NiCd battery, but even though these are cheaper, they cannot operate over a wider temperature range, nor do they have higher energy densities. Lithium batteries have a protective circuit to limit peak voltage.
For example, each lithium-ion cell of a laptop computer battery pack will contain:
⦁ temperature sensor
⦁ voltage regulator circuit
⦁ charge-status monitor
⦁ mains connector
The design of these components is such, that they minimize the risks of short-circuits by monitoring the charge-state and current flow, keep a record of the latest, full-charge capacity and monitor the temperature.
Due to their lightweight, high energy density power sources, Li-ion batteries can be used for a whole range of devices. When used in larger devices, it is more effective to connect many small batteries in a parallel circuit than to have one large single battery.
Portable devices that use Li-ion batteries include: Mobile phones, smartphones, laptops, tablets, digital cameras, electronic cigarettes, torches and portable game consoles.
Power tools that use the batteries include: All cordless tools and garden equipment, including drills, sanders saws, hedge trimmers and lawnmowers.
Modes of transport that use the batteries include: Electric cars, hybrid cars, electric motorcycles and scooters, electric bicycles, electric wheelchairs, electric golf caddies, radio-controlled model cars and aircraft, aircraft and even the Curiosity rover sent to Mars.
Telecommunications service providers use a type of secondary non-aqueous lithium battery to provide reliable backup power for their equipment; while Li-ion batteries with specific technical criteria can be use in outside location huts and enclosures. Here the users have to be made aware of the hazardous material information and have to meet the correct regulatory requirements and fire-fighting procedures.
Battery Discharge Rates And Life
Li-ion batteries self discharge at a rate of 1.5 -2% per month when not connected. This does increase when various other factors come into play, which include higher temperatures, state of charge and age of the battery.
Capacity loss is affected by inactive storage and by a defined number of full charge-discharge cycles which affect the lifespan of the battery.
The average lifetime of a Li-ion battery consists of 1000 cycles, and usually it is specified for no more than 500 cycles. That means that the batteries of hand held devices like mobile phones can be expected to last for approximately three years. Batteries based on carbon anodes can offer more than 10,000 cycles.
The voltage of the battery gradually diminishes as it discharges, but it stops discharging at a set level of depletion of 2.4 – 2.9 V/cell (this depends on the chemical composition), which is the protection circuit’s low-voltage threshold. At this level it stops discharging until recharged.
These rates may not be fully accurate because there may be variations depending on full depth of discharge/recharge, which can affect the life of the battery and once again, temperatures also play a role.
With use, Li-ion batteries degrade progressively and they have a reduced capacity, cycle life and safety because of chemical changes to the electrodes. This degradation is strongly related to temperature, with 25 degrees being the ideal storage temperature. Anything over or below that increases the degradation and even charging elevates temperatures. Poor ventilation in some devices or apparatus also increases the temperature.
Safe Usage Of Li-ion Batteries
Thermal runaway and cell rupture may occur in overheated or overcharged Li-ion batteries. In order to reduce the risk of this happening, many lithium batteries have a safety feature that disconnects them when their voltage surpasses the safety range of 3-4.2 V per cell or if they are overcharged or discharged.
It is also important that they are not used outside their recommended voltage range set by the manufacturer, as the batteries will age prematurely and the reactive components within the cell pose safety risks. Some types of lithium batteries are not safe to charge at temperatures of 0° and below.
Since Li-ion batteries require many safety features (which cannot be applied to all types of cells) they are more expensive, and contaminants inside their cells may decrease their safety. The presence of the potentially hazardous pressurized flammable liquid electrolytes in the batteries, require strict manufacturing regulations.
There have been a few aviation incidents and crashes caused by lithium-ion battery fires, where batteries have spontaneously ignited.
Li-ion Batteries And The Environment
Lithium batteries contain iron, nickel and cobalt and are considered safer to discard than other types which contain toxic metals like lead or cadmium. The metals they contain can be recycled but at a larger cost than mining these metals, so most end up in landfills or incinerators.
Cobalt is the most expensive metal used in lithium battery manufacture, and lithium iron phosphate is the cheapest, but with a danger of future shortages. Lithium extraction does impact the environment through water pollution and recycling could help prevent this and future shortages. Lithium is mined in the Americas, Asia, South Africa and China.
Nickel and cobalt need a solvent in their manufacturing process which does present environmental and health hazards.
Each one kg of Li-ion battery production takes the energy equivalent of 1.6 kg of oil.
Over the years there have been huge recalls of various batteries by companies such as Dell, Apple, Lenovo, Toshiba and many others. Many restrictions have also been imposed to transporting or flying with them. Most devices can be transported in checked baggage, but spare batteries may only be transported in carry-on baggage and should be protected against short circuiting. It is estimated that more than a billion lithium batteries are flown each year.
Ongoing research will see improved batteries in the years to come, with better power density, battery life, recharge time, cost and safety.
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