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A ll A bout Part 1: by Dr David Maddison batteries Batteries Imagine life without batteries. We’d have to crank-start our cars; we’d be stuck with fixed phones, non-portable computers, no interactive toys for kids... the list goes on. But you can’t take batteries for granted either. This series will cover just about Background Source: everything you need to know about batteries. https://unsplash.com/photos/F_EooJ3-uTs B atteries are one of our most important technologies. Today, nearly everyone carries a smartphone, and its rechargeable battery is expected to last all day (or sometimes two or three), even with several hours of active use. Many people also have an electronic watch, an electronic key for their car and possibly even electronic implants like a heart pacemaker. Little thought is given to such devices until the battery inevitably fails. Two other important uses for largescale batteries today are electric cars and storage for intermittent electricity production. In this article, we will look at the history of batteries, how they work, some interesting or common types and possible future developments. We will also look in detail at how some of the more common battery types from the past work. Two following articles will have more details on lead-acid batteries and other battery types, information 12 Silicon Chip on vehicle batteries, battery monitoring and miscellaneous extra facts about batteries. in this article. Still, we prefer “cell” when referring to one cell or “battery” for multiple. Terminology The perfect battery Any discussion of batteries has to distinguish between electrochemical cells and batteries. A cell is the basic unit of a battery and uses a chemical reaction to produce electrical energy. A battery is a collection of multiple cells connected together, usually in series, to produce a higher voltage than an individual cell – see Fig.1. Cells can also be paralleled to increase the maximum charge/discharge current and sometimes are connected in series/parallel to form a high-voltage, high-current pack. A typical example of a cell is a standard AA-size alkaline 1.5V cell, often erroneously referred to as a “battery”. The 9V batteries used to power smoke alarms are actual batteries, usually having six internal 1.5V cells in series. Given that it is common terminology, we might use the term battery for cell A perfect battery might have the following characteristics: • be made from inexpensive, non-exotic materials using simple manufacturing processes • be non-toxic when disposed of • be recyclable • be rechargeable a large number of times • provide a useful voltage, not too high or low • work consistently over a wide range of temperatures, including polar or desert regions as well as at room temperature • provide a long life • be fast to recharge • be tolerant of high discharge currents • can be fully discharged safely and repeatedly • have low weight Australia's electronics magazine siliconchip.com.au • be compact for its capacity • survive a large number of charge and discharge cycles • have low self-discharge in storage • will not leak • have a relatively stable voltage during discharge (ie, a small difference between fully charged and fully discharged voltages) • will not catch fire or explode even if misused or badly damaged Of course, there is no perfect battery. Like all engineering solutions, every battery type has advantages and disadvantages and will meet some of the above criteria, but never all (yet!). How does a battery work? A battery (more precisely a galvanic or voltaic cell) is a device that stores energy in chemical form and converts it to electricity via a chemical reaction. There are usually two interfaces to conductors (ie, anode and cathode), and a current flow is created due to the motion of electrons. This is known as an electrochemical or redox reaction. Two reactions are involved; one is called oxidation, the other is called reduction and there is an external electron flow. This is different from ordinary chemical reactions, in which electrons are also exchanged between atoms or ions but in a bulk volume, with no electrodes. In that case, there is no net flow of electrons or current. A discharging battery works spontaneously, ie, nothing is required to start the reaction. The chemical process is known as a spontaneous redox reaction. Not all electrochemical reactions are spontaneous, so not all can be used for a battery. When the battery is discharging, the positive terminal is called the cathode and the negative terminal the anode. The negative terminal is the source of electrons that flow through an attached electrical circuit to the positive terminal (see Fig.2). During oxidation, a chemical species loses one or more electrons, while in reduction, the chemical species gains one or more electrons. In a discharging galvanic cell, oxidation occurs at the anode. That is, electrons are lost, and this is the source of the electrons for the negative terminal. During discharge, reduction also occurs at the cathode. That is, electrons are gained, and the cathode is the positive terminal (www.ausetute. com.au/pbbattery.html). siliconchip.com.au Fig.1: a cell (above) is a single electrochemical cell, generating something like 1-4V via a chemical reaction between the anode and cathode. A battery (right) consists of two or more cells, usually connected in series (but sometimes in parallel or series/parallel), generating a multiple of the cell voltage. Fig.2 (below): the electrode designations, current flow and electron flow of a secondary cell during discharging and charging. Electrons are labelled as “e−”. Original source: Wikimedia user Electroche (CC BY-SA 4.0) An alternative way to state the above is that oxidation involves the loss of electrons and always occurs at the anode, while reduction involves the gain of electrons and always occurs at the cathode. The polarity of the anode and cathode (+ or −) is determined by which way electrons flow or current flows during charging and discharging. Main battery categories Batteries are classified as either primary or secondary types. A primary battery can be used once until it is exhausted and is not designed to be recharged. The chemical reactions are not generally easily reversible. AA or AAA ‘alkaline’ cells are a typical example. Note, though, that limited recharging might be possible, even if not generally Australia's electronics magazine recommended. We will discuss that later. A secondary battery is designed to be recharged multiple times; its chemical actions are reversible by applying a reverse current to recharge the battery. An automotive lead-acid battery is a typical example. Secondary batteries eventually wear out and have to be disposed of, recycled or remanufactured because the internal electrodes corrode or the structure of the cell deteriorates. Another less-common type of battery is the reserve battery. These are used in equipment that is stored for a long time and then has to be suddenly activated and used, such as certain types of military equipment like missiles. One way to activate such a battery is to add the electrolyte just before January 2022  13 Fig.3: the Baghdad Battery with a disputed interpretation assuming it was a battery. The ceramic pot is 14cm tall and has an asphalt plug at the top, a copper cylinder with an iron rod inside it immersed in ‘electrolyte’. Source: Wikimedia user Elmar Samizadə (CC BY-SA 4.0) Fig.4: an early “battery” of Leyden jars. Today we would call this a capacitor bank, not a battery. Benjamin Franklin pioneered this method and is believed to have owned this example. Source: American Philosophical Society use. Sometimes, car batteries are sold like this as well (dry). The Baghdad Battery An ancient artefact called the Baghdad Battery dates to somewhere between 150BCE to 650CE (Fig.3). Some interpreted it to be an ancient battery (more correctly a cell), but there is also evidence to suggest that it wasn’t. A copy of this artefact can be made into a workable cell. The TV show “Mythbusters” looked at this in Episode 29, first broadcast on the 23rd of March 2005. They were able to make a replica Baghdad Battery produce voltage, but only a fraction of a volt; they got more voltage by sticking metal fragments into fresh lemons. Fig.5: Jesse Ramsden’s frictional plate electrostatic machine of 1768. It was not a battery but it could produce an electrical charge. Leyden jars (as shown in Fig.4) were used as charge storage devices. Source: gutenberg. org/files/35092/35092-h/35092-h.htm 14 Silicon Chip It could have been something other than a battery. Still, it happens that the presence of an acidic solution such as vinegar enables a current to be generated due to the presence of dissimilar metals. This object disappeared during the looting of the Iraq Museum in April 2003 and has not been seen since. Origin of the term “battery” Benjamin Franklin first used the term battery, akin to an artillery battery, in 1749 to describe how he had linked up Leyden jars, an early form of capacitor, to store electricity from his static generator (see Fig.4). The first battery in Australia Sir Joseph Banks performed electrical experiments onboard the HMS Endeavour, the vessel Captain James Cook used to explore and claim Australia. Two electrical machines were carried. One was made by Jesse Ramsden (Fig.5), a famous instrument maker, and the other was a machine belonging to astronomer Charles Green and made by Francis Watkins. Banks and some other gentlemen amused themselves by giving each other shocks. Both machines appear to be frictional plate electrostatic generators. The charge from each was stored in an ‘electrostatic battery’ (basically a capacitor bank), in what were presumably Leyden jars (see Fig.6). However, they were not described by Banks by that name. Banks noted “the ill success of the Fig.6: a drawing of a Leyden jar being charged, in 1746. The jar was independently invented by German Ewald Georg von Kleist in 1745 and Dutchman Pieter van Musschenbroek of Leiden (Leyden) in 1745-46. Portrayed in the drawing is a similar experiment to the one performed by Banks, although the electrostatic generator uses a rotating glass sphere instead of the disc. The electrical charge produced is stored in the Leyden jar. Australia's electronics magazine siliconchip.com.au Electrical experiments”, possibly due to excessive humidity or moisture. For those interested, an account of Sir Joseph Banks’ electrical experiments onboard the Endeavour can be seen in “The Endeavour Journal of Joseph Banks” at https://setis.library. usyd.edu.au/ozlit/banks/banksvo1. pdf (Fig.7). See pages 81 to 93 of the PDF document (not the diary page numbers). Electrical experiments were performed on the 25th of October 1768 (two months after leaving Plymouth, England) and then again on the 19th of March and the 23rd of March 1770. Cook was still charting New Zealand on the March date and did not leave New Zealand for Australia until the 31st of March 1770, so the second battery experiment was performed in New Zealand waters. However, the equipment was brought to Australia, so it can be argued that it was the first battery in Australia. Cook landed in Botany Bay on the 29th of April 1770. Thanks to S. M. of the State Library of NSW for their assistance in finding some of the source documents on this topic. If you want to perform an experiment similar to what Banks would have, or see the type of spark that might have been generated (but using modern materials), see the video titled “William Gurstelle shows How to Build an Electrostatic Generator and a Leyden Jar” at https://youtu.be/ H5wr1Ishmx0 Fig.7: the cover of the 1747 book by Francis Watkins on his electrical experiments. He made one of the machines brought by Banks to Australia. You can read this book online at https://books.google.com.au/ books?id=AzRWAAAAcAAJ Fig.8: one of Volta’s original voltaic piles, on display at the Tempio Voltiano in Como, Italy; see siliconchip.com.au/link/abbp – Source: Wikimedia user GuidoB (CC BY-SA 3.0) The first true battery Alessandro Giuseppe Antonio Anastasio Volta invented the first electrochemical battery in 1799, publishing the results in 1800. This is a true battery in terms of our modern definition of it being an electrochemical device, not a capacitive charge storage device like a Leyden jar. Volta’s original battery or voltaic pile (shown in Figs.8 & 9) comprised a column of alternating copper and zinc discs separated by cloth or cardboard soaked in a brine (saltwater) electrolyte. Volta initially misunderstood how the battery worked. He thought the electricity was generated by the contact between dissimilar materials. Later, it became apparent that the corrosion of the zinc discs was related to the current produced by the battery. Thus, he realised that the battery siliconchip.com.au Fig.9: this shows how Volta’s voltaic pile was constructed. Original source: Wikimedia user Borbrav, SVG version by Luigi Chiesa (CC BY-SA 3.0) Fig.10: a cross-section diagram of the original Daniell cell. Original source: Armando-Martin, public domain worked by an electrochemical process. Even though the original batteries produced by Volta were flawed and only worked for about one hour, they enabled many new discoveries to be made. We will now discuss some of the more important types of primary batteries, both historical and in current use. We will look into some of these in more detail and other types of batteries in the following article next month. Batteries after Volta Primary batteries Early batteries, including Volta’s, were primary (non-rechargeable) batteries. Secondary (rechargeable) batteries were developed later. In 1836, John Frederic Daniell solved some of the problems with Volta’s battery with the Daniell cell. This was a copper pot containing copper Australia's electronics magazine January 2022  15 Fig.11 (left): the construction of a gravity cell. This particular variant is called the crowfoot cell due to the shape of the negative terminal. Original Source: Cyclopedia of Telegraphy and Telephony, 1919 Fig.12 (above): the cross-section of a zinc-carbon battery with ammonium chloride electrolyte. Original source: Wikimedia user Mcy jerry (CC BY 2.5) sulfate into which was immersed a porous earthenware vessel containing sulfuric acid and a zinc electrode (see Fig.10). Ions could pass through the earthenware vessel, but the solutions could not mix. It produced 1.1V and became the first practical cell. It was widely used in the new telegraph networks. There followed several improvements to the Daniell cell such as Bird’s cell (1837) by Golding Bird, the Porous pot cell (1838) by John Dancer and in the 1860s, the gravity cell by mysterious Frenchman Monsieur Callaud, whose first name is unknown. The gravity cell dispensed with the porous barriers used on Bird’s and Dancer’s cells, thus giving it a lower internal resistance and improved current delivery capability. In the gravity cell, the different electrolytes (zinc sulfate and copper sulfate) are not separated by a barrier but by gravity due to the different densities of the two electrolytes (see Fig.11). This gravity separation also renders the cell unsuitable for mobile applications. Also, a current must be continuously drawn from the cell; otherwise, the electrolytes will mix. The gravity cell became standard on the US and UK telegraph networks and was in use until the 1950s. Chromic acid cells were another type of primary cell developed; one was the Poggendorff cell. It used zinc and carbon plates, but the zinc would 16 Silicon Chip dissolve even when the cell was not in use, so a mechanism was needed to lift the zinc out of the electrolyte when the cell was not in use (see Fig.14). A further development of the Poggendorff cell was the Fuller cell (Fig.15). It used mercury to form an amalgam with zinc to prevent its dissolution. Later came the Grove cell (1839) comprising zinc, sulfuric acid, platinum and nitric acid and the Dun cell (1885) comprising iron, carbon and a mixture of hydrochloric and nitric acids. This mixture is known as aqua regia; it is a very powerful acid that can dissolve gold or platinum. The Leclanché cell was invented in 1866 by Georges Leclanché. It consisted of a zinc anode, manganese dioxide and carbon cathode and ammonium chloride as the electrolyte (Fig.16). It produced 1.4V. It was used in telegraphy, telephony, rail signalling and electric bells. One disadvantage was that the battery current would diminish during long telephone conversations due to increasing internal resistance. In 1886, a variant of the Leclanché cell was produced by Carl Gassner in which he mixed the liquid ammonium chloride electrolyte along with zinc chloride (to extend the shelf life of the electrolyte) with plaster of Paris to make a ‘dry cell’ producing 1.5V. In 1896, the National Carbon Company in the USA developed it further, replacing the plaster with rolled cardboard. The battery could be used in any orientation and was maintenance-­ free. The first battery they made was a telephone battery (see Fig.13), and in 1898, the company introduced what later became known as the D-cell or ‘flashlight (torch) battery’. These became known as zinc-carbon cells and were the first mass-produced battery for widespread use, leading to the development of the battery flashlight (torch). This type of cell is still common and available today. Fig.16: a Leclanché cell. This example is a Samson No.2 brand ammonium chloride, zinc and manganese dioxide/carbon battery, c.1906-1916. Such a battery is also featured in the 25th catalogue of Manhattan Electrical Supply Co. c.1910. The complete battery sold for US$1.60 and all parts were replaceable. Source: Harvard University, The Collection of Historical Scientific Instruments Australia's electronics magazine siliconchip.com.au Fig.13: Columbia Gray Label dry cell telephone batteries of the type first produced by the National Carbon Company. It isn’t known when these were made, but they bear the Eveready trademark, so they must have been made after 1917 when Union Carbide acquired Eveready. This type of battery was produced until at least the 1950s. Source: www.flickr.com/ photos/51764518<at>N02/36670011780 (Creative Commons) In parallel with these developments, in 1887, another dry battery based on the Leclanché cell was developed independently by Dane Wilhelm Hellesen. Sakizou Yai of Japan also developed a dry cell in 1887 (said to involve carbon and paraffin), which were used with great success in the Sino-­Japanese war of 1894-95, earning him the title “king of the dry battery”. He established a battery factory in 1910. Improvements were made to the zinc-carbon cell over the twentieth century, including about a fourfold capacity increase. Other improvements were a longer shelf life, better sealing and the use of less toxic components, such as the elimination of mercury. Standard zinc-carbon batteries use Fig.14: the Poggendorff cell, described as a “Student’s Plunge Cell”. Source: 25th catalogue of Manhattan Electrical Supply Co. c.1910, page 176 Fig.15: the Fuller cell, both regular and high-current versions. Source: 25th catalogue of Manhattan Electrical Supply Co. c.1910, page 173 an ammonium chloride electrolyte with possibly some zinc chloride. “Heavy-duty” cells use mostly zinc chloride as the electrolyte. A heavyduty battery has about twice the capacity of a standard battery. However, zinc-carbon cells have been mostly replaced these days by the alkaline variety, which have about eight times the capacity (see below). zinc reacts to produce two electrons and is consumed during discharge. The electrons flow through the external load to the cathode, where the manganese dioxide reacts with either ammonium chloride or zinc chloride (or both). The reaction for batteries with an ammonium chloride electrolyte is: Chemistry of zinc-carbon cells A zinc-carbon cell comprises a zinc ‘can’, which constitutes the negative terminal or anode of the cell and a carbon rod with manganese dioxide, which is the positive terminal of the battery or cathode – see Fig.12. The electrolyte is either ammonium chloride or zinc chloride (or a mixture). Regardless of the electrolyte, the Zn + 2MnO2 + 2NH4Cl ⇌ Mn2O3 + Zn(NH3)2Cl2 + H2O The reaction for batteries with a zinc chloride electrolyte is: Zn + 2MnO2 + ZnCl2 + 2H2O ⇌ 2MnO(OH) + 2Zn(OH)Cl This type of battery is widely available in the AAA, AA, C, D and PP3 (9V) size formats – see Fig.17. These batteries have a typical voltage when Fig.17: a selection of modern disposable consumer batteries. L to R, top to bottom they are: 4.5V (3LR12) battery (primarily used in Europe), D, C, AA, AAA, AAAA, A23, 9V, LR44 and CR2032. There are many proprietary designations for battery sizes; the ANSI and the IEC establish standard names. Source: Wikimedia user Lead holder (CC BY-SA 3.0) siliconchip.com.au Australia's electronics magazine January 2022  17 Collecting old batteries Believe it or not, some people collect old batteries. For some good examples, visit www.ericwrobbel. com/collections/batteries.htm new of 1.55V to 1.7V and are considered flat when they reach around 0.8V under load. Alkaline cells In alkaline cells, the acidic ammonium chloride or zinc chloride electrolyte of regular zinc-carbon batteries is replaced with zinc powder in an alkaline potassium hydroxide gel. A current pickup spike forms the negative electrode (anode). The carbon electrode is replaced with manganese dioxide with carbon powder to make the positive electrode (cathode) – see Fig.18. A patent for the modern alkaline cell based on zinc-manganese dioxide was filed by Canadian Lewis Urry in 1957, awarded in 1960. Most of the energy of these cells is contained within the zinc electrode. The nominal voltage is 1.5V. They are direct substitutes for carbon-zinc batteries in common appliances and come in the standard sizes of AAA, AA, C, D etc. The reaction for alkaline zinc-­ manganese dioxide cells is as follows: Zn(s) + 2MnO2(s) ⇌ ZnO(s) + Mn2O3(s) Standard alkaline batteries are said to be rechargeable a few times, with reduced capacity and some risk of leakage. This practice is not recommended by manufacturers, although you can find chargers designed for this purpose, such as the ReZAP charger (https://rezap.com/) from an Australian company. It also supports various other battery chemistries. Some alkaline cells (known as RAM or rechargeable alkaline manganese) have been designed to have limited rechargeability, up to about 10 times. They are primarily suitable for lowdrain devices. These days, they might not be cost-effective due to the low cost of low-self-discharge NiMH cells, which are rechargeable hundreds of times. acid electrolyte. The original design was improved in 1881 by Camille Alphonse Faure, who replaced the cathode with a lead grid into which lead dioxide was pressed, allowing multiple plates to be stacked together. This basic design is still in use. The lead-acid battery is heavy and bulky but is relatively cheap and can produce a very high current for a short period, making it ideal as a car starting battery. It is one of the most recycled of all products, as virtually all parts are highly recyclable. We will discuss lead-acid batteries more, including describing different versions like gel cells and AGM batteries, in the article to follow next month. Secondary (rechargeable) batteries Nickel-cadmium cells Primary batteries have the obvious disadvantage that they must be replaced (or in early types of primary batteries, various components had to be replaced) once they are depleted. Replacing them with rechargeable batteries would, in the long term, reduce both cost and waste products. Lead-acid batteries The first rechargeable battery was invented in 1859 by Gaston Planté, based on lead-acid chemistry. This is still popular today, used in car starting batteries, backup power systems, emergency lighting, UPSs, off-grid systems, caravans, boats and more. These comprise a lead anode and lead dioxide cathode with a sulfuric The NiCd, nicad or nickel-cadmium cell was invented in 1899 by Waldemar Jungner in Sweden. It was a wet cell using an alkaline electrolyte of potassium hydroxide and was commercialised in 1910, being introduced in the USA in 1946. It was originally a competitor to lead-acid batteries. Later models were made as sealed dry cells and were available in the same form factors as zinc-carbon cells such as AA, C, D etc. The terminal voltage is 1.2V, which remains relatively constant during discharge. They are capable of high discharge rates. Nicad batteries are also robust and tolerant of deep discharge and can even be stored in a fully discharged state. They have a longer life than lead-acid in terms of lifetime charge and discharge cycles. Fig.18: a cross-sectional diagram of an alkaline cell, the most common type of primary cell used today. Original source: Wikimedia user electrical4u (CC BY 3.0) Fig.19: a nickel-hydrogen storage battery for space applications. This model (21HB-7) is from Russia. It weighs 5kg, has a capacity of 7Ah, a working pressure of up to 6.2MPa (900psi) and a service life of five years or 25000 cycles at an operating voltage between 21V and 325V. Source: https://ueip.org/ 18 Silicon Chip Australia's electronics magazine siliconchip.com.au A common myth surrounding nicad cells is that they suffer a “memory effect” where a battery will “remember” an incomplete discharge followed by a charge and suffer a voltage drop when the battery is again discharged to the point of the incomplete discharge. The authors of the original paper that claimed this retracted it. Nicads were once common in mobile phones, power tools and other portable devices but were supplanted by NiMH types (described below), which themselves have been superseded by lithium-ion cells. Their use has been decreased dramatically, partly due to the disposal problems of toxic cadmium and their higher cost compared to NiMH cells. Nickel-hydrogen batteries The nickel-hydrogen battery was first patented in 1971 and is a specialised battery primarily suitable for spacecraft such as the Hubble Space Telescope. They are now being considered for stationary storage applications. They can be regarded as a hybrid battery, with elements of both an electrochemical cell and a fuel cell. They operate at high pressures within a vessel, and use nickel as the positive electrode and a hydrogen fuel cell as the negative electrode – see Fig.19. They contain nickel, hydrogen in gaseous form at a pressure of up to 8.2MPa (1200psi) and potassium hydroxide as electrolyte. They have an energy density of about one-third that of a lithium battery; their main advantage is long service life. They also have a relatively high self-discharge rate, but this is not a great concern in space, where the battery is regularly recharged in orbit as the solar cells exit the earth shadow. As the battery discharges, the hydrogen pressure drops. A single cell has an open-circuit voltage of 1.55V. The NiH2 batteries on the Hubble Telescope were replaced after 18 years, although they were still working with only some loss of capacity. They were designed to last just five years. Nickel-metal-hydride cells Nickel-metal-hydride cells (NiMH) are now a common rechargeable type, replacing nicad cells in consumer items. They are available in standard sizes such as AAA, AA, C, D etc. They are similar to nicads, using a positive siliconchip.com.au Fig.20: the structure of a NiMH cell. The electrodes are rolled up in what is known as a “jelly roll” construction, common in many rechargeable cells such as 18650s. Source: Radio Shack nickel electrode, but instead of cadmium for the negative electrode, they use a hydrogen-absorbing metal (see Fig.20). They have two to three times the energy density of nicad, but still lower than lithium-ion, and are relatively non-toxic. Their nominal voltage is 1.2V, and they can typically replace alkaline cells. They were invented in 1967 but weren’t released onto the consumer market until 1989. The first commercial NiMH batteries had a significant self-discharge rate of 0.5-4% per day, but in 2005, Sanyo developed a low-self-discharge battery under the Eneloop brand that had a capacity of 70-85% after one year. The low self-discharge is due to thicker separators between the positive and negative electrodes, but this means less room for active materials and thus lower capacity. A low self-discharge AA cell might have a capacity of 2500mAh and a regular one, 2700mAh. Panasonic took over ownership of Sanyo in 2009, and FDK Corporation now produces NiMH batteries for Panasonic. Before lithium-ion batteries became commonplace in electric vehicles (EVs), NiMH cells tended to be used, such as in the General Motors EV1 and early Toyota Prius models. Nickel-iron (Edison) batteries The nickel-iron or NiFe battery has nickel(III) oxide-hydroxide positive plates and iron negative plates, an alkaline electrolyte of potassium hydroxide, and a nominal cell voltage of 1.2V – see Fig.21. They were invented by the Swede Waldemar Jungner in 1899, when he substituted the cadmium in nicad batteries for lower-­ cost iron. The best disposable batteries Disposable AAA, AAA, C, D and 9V batteries from the “big two” (Duracell and Energizer) are generally good but don’t ignore batteries and cells from other sources. We have had success with cells from Aldi or Varta cells from Bunnings, where 30 AA or AAA cells can be had for less than $10. Australia's electronics magazine January 2022  19 Safety warning for lithium button cells Always store and dispose of lithium button cells correctly, keeping them away from children and pets. If ingested by children or pets, gastric juices can corrode the battery case and cause the harmful contents to leak out and cause chemical burns. Current flowing between the terminals can also damage internal tissue. disadvantage, but which may be an advantage, as we will now discuss. Proponents of intermittent energy sources like wind and solar power are investigating nickel-iron batteries because they can store energy and produce hydrogen as a byproduct. They continue safely making it even when the batteries are fully charged (continued charging would harm most batteries). The hydrogen can be used later as a fuel – see Fig.22. Such batteries are called battolysers, a combination of a battery and an electrolysis cell. A battolyser is better than an electrolytic cell for making hydrogen because there is minimal cell degradation with the battolyser; in fact, the battery improves in capacity once it has been used to produce hydrogen when fully charged. He patented the invention but abandoned development because of lower charging efficiency and excessive hydrogen production. In the USA, Thomas Edison patented the NiFe battery in 1901. He saw it as the ideal battery for electric vehicles (the preferred type of car in the early 1900s) and superior to the lead-acid battery. As internal combustion engines became popular, Edison was disappointed that his battery was not chosen as the starter battery in such vehicles. At the time, his batteries could be charged faster and had a higher energy density than lead-acid batteries. However, they performed poorly in cold weather and were also more expensive. Despite not being adopted in motor vehicles, Edison batteries (as they were also known) were produced from 1903 to 1972 by the Edison Storage Battery Company. They had a wide range of applications such as in railroads, forklifts and backup power. These batteries are still available today, made by other companies, and can be suitable for offgrid power systems, among other uses. NiFe batteries have the advantages of cheap materials, long life, durability, high depth-of-discharge (80%), tolerance of overcharging/overdischarging and short circuit resistance. While somewhat more expensive than leadacid and lithium-ion batteries for the same total energy storage, they have a claimed lower cost over their lifetime, which can be 50 years or more. Modern NiFe batteries also have a wide temperature tolerance, working from -30°C to +60°C. Due to their high self-discharge rate (1% per day), it is best to use them in situations where they are frequently recharged. Disadvantages include: • not being maintenance-free; they have to be checked and topped up regularly but do not need to be ‘equalised’ like lead-acid batteries • lower energy density than leadacid batteries (although the high depth-of-discharge helps to make up for this) • lower charge and discharge rate due to higher internal resistance (about five times that of lead-acid) NiFe batteries produce a lot of hydrogen during charging, usually a Fig.21: the Edison nickel-iron battery. Source: Edison Storage Battery Company, 1917 Fig.22: the usage scheme for a nickel-iron battolyser. Source: Delft University of Technology 20 Silicon Chip Australia's electronics magazine Lithium and Li-ion batteries At the moment, lithium-ion batteries are in the news more than any other battery type. They are mostly standard in consumer devices, phones, watches, electric cars and many largescale energy storage systems. Lithium is attractive as an active material in batteries because of its low weight, high atomic mobility (ease of movement through the electrolyte) and its specific electrochemical properties. Lithium-based primary cells usually contain metallic lithium, while rechargeable batteries usually contain siliconchip.com.au Fig.23: older lithium/iodinepolyvinylpyridine (or Li-I2) batteries, as used in cardiac pacemakers. lithium in ion form instead; an important distinction. Lithium primary cells are sometimes referred to as “lithium metal” to distinguish them from lithium-ion rechargeable cells. Note though that rechargeable lithium metal batteries are being developed (described next month). Lithium-based batteries are relatively lightweight, have a high energy density, low self-discharge, and can be optimised for either high energy density (mAh capacity) or high power density (maximum current that they can handle). They usually produce no gas, so they can be fully sealed. However, of all batteries in use, they have probably been involved in the most safety incidents. Lithium-based batteries can be manufactured with a variety of chemistries and were first commercially produced in the 1970s as primary cells (non-­ rechargeable). Depending on the specific chemistry, their voltage can range from about 1.5V to 3.7V (or 4.2V fully charged). A lithium/iodine-­polyvinylpyridine primary battery was first patented in 1971-72 by James Moser and Alan Schneider and used in a cardiac pacemaker implanted in 1972. This dramatically improved the life of the device and reduced its size compared to the mercury-zinc batteries it replaced (see Fig.23). This type of lithium battery is still in use in pacemakers and other implanted medical devices today. They have a terminal voltage of 2.8V and a high internal resistance of around 10kW, so they can only be used for low-current/low-power applications (eg, 1mW), such as pacemakers. These batteries have outstanding reliability in their pacemaker application. Battery life is typically 5-15 years, depending on pacemaker activity. In the 1980s, there were major developments towards lithium-based secondary (rechargeable) batteries. In 1985, Akira Yoshino developed the siliconchip.com.au Fig.24: a Panasonic 18650 lithiumion battery taken out of its case. Note the “jelly roll” construction of the battery core (green). The 18650 form factor is very popular in various applications. Source: Wikimedia user RudolfSimon (CC BY-SA 3.0) Fig.25: a lithium-polymer (LiPo) battery as used in a mobile phone. Source: Wikimedia user Kristoferb (CC BY-SA 3.0) first prototype lithium-ion rechargeable battery based on earlier research in the 1970s and 1980s by John B. Goodenough, M. Stanley Whittingham, Rachid Yazami and Koichi Mizushima. In 1991, a commercial lithium-ion battery was then made by Sony and Asahi Kasei, with a team led by Yoshio Nishi. In 2019, John B. Goodenough, M. Stanley Whittingham and Akira Yoshino received a Nobel Prize for their work. In 1997, the first lithium polymer (LiPo) battery was produced by Sony and Asahi Kasei. These have a flexible wrapping that can be made in any desired size and shape rather than the rigid, typically cylindrical casing of lithium-ion batteries (see Figs.24 & 25). There are numerous lithium-based battery chemistries, along with a few common ones (see panel overleaf). Fig.26 shows the trade-off between power delivery and cell capacity. The greater the current delivery, the lower the capacity. The negative electrode of a lithium battery is usually carbon (eg, graphite), while the positive electrode is a metal oxide or “polyanion” such as the one first identified by John Goodenough, lithium iron phosphate. It is treated in various ways to make it more electrically conductive. The electrolyte is a lithium salt in an organic solvent. For a lithium-ion battery using a negative carbon (C) electrode and a positive lithium-cobalt-oxide (LiCoO2) electrode, the full chemical reaction is as follows (also see Fig.27). Left to right Fig.26: the trade-off between energy density and power density for lithium-ion cells (mostly 18650 size) based upon cathode surface area. Australia's electronics magazine January 2022  21 Substituting batteries in old radios and tape players Vintage transistor radios and cassette tape players often need four, six or eight relatively expensive C or D cells. Modern AA alkaline cells are usually capable of powering these devices as well or better than the C or D cells that were available in the 1960s or 1970s, when these devices were designed. All that’s needed is to buy a “sabot” adaptor, commonly available online. Right: this “sabot” adaptor allows a AA cell to be used in place of a C cell. Other adaptors exist that let you substitute two AA cells for a D cell. is discharging, right to left is charging. LiC6 + CoO2 ⇌ C6 + LiCoO2 Because lithium-ion cells can be easily damaged if overcharged or overdischarged (and in extreme cases can catch fire or explode), they are generally packaged with protective electronics in each cell or battery. This disconnects them from external circuitry if it detects a problem such as the voltage being outside the normal range, high temperature or excessive current flow (see Fig.28). Safety of lithium batteries Lithium batteries are generally considered safe. Some lithium-ion chemistries, such as LiFePO4 (lithium-­ironphosphate), are notably more robust than others and will withstand abuse without failing (unless the abuse is extreme) or catching fire. Regular lithium-­ion and LiPo types are more sensitive. There have been some notable incidents such as: September 2010: UPS Airlines Flight 6, a Boeing 747-400F, crashed after an onboard fire in a cargo pallet containing 81,000 lithium batteries and other material. It is not known what caused the auto-ignition. January 2013: there was a problem with Boeing 787 onboard lithium-ion batteries catching fire. Fortunately, no one was hurt, but investigations revealed a ‘thermal runaway’ event due to a shorted cell that was attributed to inadequate quality control at manufacture and inadequate scenario testing by Boeing engineers. The problem was solved with better quality control by the battery manufacturer and better thermal and electrical Fig.28: a battery management circuit, as used in many lithium cells such as 18650s, to prevent overcharging, overdischarging and provide short circuit protection. Source: Wikimedia user Oldobelix (public domain) insulation, along with other changes. The problem was solved by April 2013, and the aircraft returned to service. 2016: Samsung Galaxy Note 7 phones were prohibited from being taken on planes due to a manufacturing fault related to the battery, which could cause the device to catch fire or explode after thermal runaway. The product was recalled, and Samsung issued software updates that stopped the phone from being charged at all. August 2018: Australia’s CASA (Civil Aviation Safety Authority) has published a procedure to deal with lithium battery fires onboard aircraft – see siliconchip.com.au/link/abbl July 2021: General Motors announced a combination of hardware and software alterations to their Chevrolet Bolt and Bolt EUV cars to address fire risks. At the same time, Fig.27: a simplified view of the processes in a lithium-ion battery during charging and discharging. 22 Silicon Chip Australia's electronics magazine siliconchip.com.au Common primary (lithium metal) types: Figs.29 & 30: Contingency East (emergency services) in Copenhagen developed this device to contain electric vehicle fires. Source: the Danish Institute of Fire and Security Technology they withdrew their previous advice to park the car more than 15m away from other vehicles or structures after 12 spontaneous fires in their battery packs (made by LG). See siliconchip. com.au/link/abbm August 2021: there was a large lithium-­ion battery fire in Moorabool, near Geelong, Victoria, at the Victorian Big Battery (Tesla). It took more than three days to extinguish. You can read the report of the investigation by Energy Safe Victoria at siliconchip. com.au/link/abbn The investigation revealed that “The most likely root cause of the incident was a leak within the Megapack cooling system that caused a short circuit that led to a fire in an electronic component. This resulted in heating that led to a thermal runaway and fire in an adjacent battery compartment within one Megapack, which spread to an adjacent second Megapack...” “The supervisory control and data acquisition (SCADA) system for a Megapack took 24 hours to ‘map’ to the control system and provide full data functionality and oversight to operators.” siliconchip.com.au “The Megapack that caught fire had been in service for 13 hours before being switched into an off-line mode when it was no longer required as part of the commissioning process. This prevented the receipt of alarms at the control facility.” Container for EV fires Local emergency services in Copenhagen have developed a container to place over an electric vehicle in the event of a battery fire (see Figs.29-30). A damaged or burning electric car is lifted into or pushed into the container. It has nozzles to spray cooling water and a pump for recirculation. More on lithium-ion batteries For more details, see our article on lithium-ion cells (August 2017; siliconchip.com.au/Article/10763) & the article on LiFePO4 cells (June 2013; siliconchip.com.au/Article/3816). In the second article in this series, to be published next month, we’ll describe quite a few new and upcoming battery chemistries/technologies. We’ll also have considerably more detail on lead-acid batteries, which SC are still in widespread use. Australia's electronics magazine Li-MnO2, 3V The most common consumer primary lithium battery Li-(CF)x, 3V Used for memory backup and aerospace applications Li-FeS2, 1.4V-1.6V Can replace alkaline consumer batteries Li-SOCl2, 3.5V Works at low temperatures (down to -55°C), used by militaries, expensive, hazardous Li-SO2, 2.85V Wide temperature range (-55°C to 70°C), used by militaries, toxic, hazardous Li-I2, 2.8V Used for medical implants Li-Ag2CrO4, 2.6V-3.1V Used for medical implants Li-Ag2V4O11 / Li-SVO / Li-CSVO Medical use, emergency beacons Li-CuO, 1.5V Replacement for consumer alkaline batteries; no longer popular Li-Bi2Pb2O5, 1.5V Replacement for silver-oxide batteries Li/Al-MnO2, 3V Made by Maxell Common secondary (lithium-ion) types: LiCoO2 or LCO (lithium-cobaltoxide), 3.7V Good overall performance, used in mobile phones, tablets, laptops, remote-controlled vehicles etc but less safe than most other types NMC (nickel-manganese-cobaltoxide), 3.6V-3.7V Longer-lived and higher-capacity compared to LiCoO2; used in power tools and electric vehicles NCA (nickel-cobalt-aluminiumoxide), 3.6V-3.7V Used in electric vehicles (eg. the Panasonic batteries used by Tesla) and consumer devices LiFePO4 (lithium-ironphosphate), 3.0V-3.2V Robust but lower capacity density; applications in vehicles, power tools, backup power systems etc January 2022  23