The alkaline battery gets its name because it has an alkaline electrolyte of potassium hydroxide (KOH) instead of the acidic ammonium chloride (NH4Cl) or zinc chloride (ZnCl2) electrolyte of the zinc–carbon batteries. Other battery systems also use alkaline electrolytes, but they use different active materials for the electrodes.
Alkaline batteries account for 80% of manufactured batteries in the US and over 10 billion individual units produced worldwide. In Japan, alkaline batteries account for 46% of all primary battery sales. In Switzerland, alkaline batteries account for 68%, in the UK 60% and in the EU 47% of all battery sales including secondary types.[1][2][3][4][5] Alkaline batteries contain zinc (Zn) and manganese dioxide (MnO2) (Health codes 1), which is a cumulative neurotoxin and can be toxic in higher concentrations. However, compared to other battery types, the toxicity of alkaline batteries is moderate.[6]
Thomas Edison's nickel–iron batteries manufactured under the "Exide" brand, originally developed in 1901 by Thomas Edison, use a potassium hydroxide electrolyte.
Batteries with alkaline (rather than acid) electrolyte were first developed by Waldemar Jungner in 1899, and, working independently, Thomas Edison in 1901. The modern alkaline dry battery, using the zinc/manganese dioxide chemistry, was invented by the Canadian engineer Lewis Urry in the 1950s in Canada before he started working for Union Carbide's Eveready Battery division in Cleveland, OH, building on earlier work by Edison.[7][8] On October 9, 1957, Urry, Karl Kordesch, and P. A. Marsal filed US patent (2,960,558) for the alkaline battery. It was granted in 1960 and was assigned to the Union Carbide Corporation.[9]
When alkaline batteries were introduced in the late 1960s, their zinc electrodes (in common with the then ubiquitous carbon-zinc cells) had a surface film of mercuryamalgam. Its purpose was to control electrolytic action on impurities in the zinc; that unwanted electrolytic action would reduce shelf life and promote leakage. When reductions in mercury content were mandated by various legislatures, it became necessary to greatly improve the purity and consistency of the zinc.[10]
Chemistry
In an alkaline battery, the negative electrode is zinc and the positive electrode is manganese dioxide (MnO2). The alkalineelectrolyte of potassium hydroxide (KOH) is not consumed during the reaction (it is regenerated), only the zinc and MnO2 are consumed during discharge. The concentration of alkaline electrolyte of potassium hydroxide remains constant, as there are equal amounts of OH−anions consumed and produced in the two half-reactions occurring at the electrodes.
The two half-reactions are:
Anode (oxidation reaction), negatively charged electrode because accepting e− from the reductant in the cell:
Several sizes of button and coin cells. Some are alkaline and others are silver oxide. Two 9V batteries were added as a size comparison. Enlarge to see the size code markings.
The capacity of an alkaline battery is strongly dependent on the load. An AA-sized alkaline battery might have an effective capacity of 3000mAh at low drain, but at a load of 1ampere, which is common for digital cameras, the capacity could be as little as 700mAh.[12] The voltage of the battery declines steadily during use, so the total usable capacity depends on the cutoff voltage of the application.
Voltage
The nominal voltage of a fresh alkaline cell as established by manufacturer standards is 1.5V. The actual zero-load voltage of a new alkaline battery ranges from 1.50 to 1.65V, depending on the purity of the manganese dioxide used and the contents of zinc oxide in the electrolyte. The voltage delivered to a load decreases as the current drawn increases and as the cell discharges. A cell is considered fully discharged when the voltage drops to about 0.9V.[13] Cells connected in series produce a voltage equal to the sum of the voltages of each cell (e.g., three cells generate about 4.5V when new).
AA battery voltage vs capacity, at zero-load and 330mW load[14]
Capacity
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Zero-load
1.59
1.44
1.38
1.34
1.32
1.30
1.28
1.26
1.23
1.20
1.10
330mW
1.49
1.35
1.27
1.20
1.16
1.12
1.10
1.08
1.04
0.98
0.62
Current
The amount of electrical current an alkaline battery can deliver is roughly proportional to its physical size. This is a result of decreasing internal resistance as the internal surface area of the cell increases. A rule of thumb is that an AA alkaline battery can deliver 700mA without any significant heating. Larger cells, such as C and D cells, can deliver more current. Applications requiring currents of several amperes such as powerful portable audio equipment require D-sized cells to handle the increased load.
In comparison, Lithium-ion and Ni-MH batteries can handle 2amperes with ease on the standard AA size.[15]
Construction
Alkaline battery
Alkaline batteries are manufactured in standard cylindrical forms interchangeable with zinc–carbon batteries, and in button forms. Several individual cells may be interconnected to form a true "battery", such as the 9-volt PP3-size battery.
A cylindrical cell is contained in a drawn stainless steel can, which is the cathode connection. The positive electrode mixture is a compressed paste of manganese dioxide with carbon powder added for increased conductivity. The paste may be pressed into the can or deposited as pre-molded rings. The hollow center of the cathode is lined with a separator, which prevents contact of the electrode materials and short-circuiting of the cell. The separator is made of a non-woven layer of cellulose or a synthetic polymer. The separator must conduct ions and remain stable in the highly alkaline electrolyte solution.
The negative electrode is composed of a dispersion of zinc powder in a gel containing the potassium hydroxide electrolyte. The zinc powder provides more surface area for chemical reactions to take place, compared to a metal can. This lowers the internal resistance of the cell. To prevent gassing of the cell at the end of its life, more manganese dioxide is used than required to react with all the zinc. Also, a plastic-made gasket is usually added to increase leakage resistance.
The cell is then wrapped in aluminium foil, a plastic film, or rarely, cardboard, which acts as a final layer of leak protection as well as providing a surface on which logos and labels can be printed.
When describing AAA, AA, C, sub-C and D size cells, the negative electrode is connected to the flat end, and the positive terminal is the end with the raised button. This is usually reversed in button cells, with the flat-ended cylindrical can being the positive terminal.
Some alkaline batteries are designed to be recharged a few times, and are described as rechargeable alkaline batteries. Attempts to recharge standard alkaline batteries may cause rupture, or the leaking of hazardous liquids that corrode the equipment. However, it is reported that standard alkaline batteries can often be recharged a few times (typically not more than ten), albeit with reduced capacity after each charge; chargers are available commercially. The UK consumer organisation Which? reported that it tested two such chargers with Energizer alkaline batteries, finding that battery capacity dropped on average to 10% of its original value, with huge variations, after two cycles (without stating how depleted they were before recharging) after recharging them two times.[16]
In 2017 Gautam G. Yadav published papers reporting that alkaline batteries made by interleaving the interlayers with copper ions could be recharged for over 6,000 cycles due to the theoretical second electron capacity of manganese dioxide.[clarification needed][17][18] The energy density of these rechargeable batteries with copper intercalated manganese dioxide is reported to be over 160Wh/L, the best among the aqueous-based chemistries.[18] It could be capable of energy densities comparable to lithium-ion (at least 250Wh/L) if zinc utilization in the batteries were improved.[17]
Leaks
Potassium compound leakage inside an alkaline battery
Alkaline batteries are prone to leaking potassium hydroxide, a caustic agent that can cause respiratory, eye and skin irritation.[note 1] The risk of this can be reduced by storing batteries in a dry place and at room temperature. Damage from leakage is mitigated by removing batteries when storing devices. Applying reverse current (such as by recharging disposable-grade cells, or by mixing batteries of different types or state of charge in the same device) can increase the risk of leakage.[citation needed]
All batteries gradually self-discharge (whether installed in a device or not) and dead batteries eventually leak. Extremely high temperatures can also cause batteries to rupture and leak (such as in a car during summer) as well as decrease the shelf life of the battery.
The reason for leaks is that as batteries discharge–either through usage or gradual self-discharge–the chemistry of the cells changes and some hydrogen gas is generated. This out-gassing increases pressure in the battery. Eventually, the excess pressure either ruptures the insulating seals at the end of the battery, or the outer metal canister, or both. In addition, as the battery ages, its steel outer canister may gradually corrode or rust, which can further contribute to containment failure.
Once a leak has formed due to corrosion of the outer steel shell, potassium hydroxide absorbs carbon dioxide from the air to form a feathery crystalline structure of potassium carbonate that grows and spreads out from the battery over time, following along metal electrodes to circuit boards where it commences oxidation of copper tracks and other components, leading to permanent circuitry damage.
The leaking crystalline growths can also emerge from seams around battery covers to form a furry coating outside the device, that corrodes any objects in contact with the leaking device.
Disposal
Since alkaline batteries were made with less mercury beginning in 1996, alkaline batteries are allowed to be disposed of as regular domestic waste in some locations. However, older alkaline batteries with mercury, and the remaining other heavy metals and corrosive chemicals in all batteries (new and old), still present problems for disposal—especially in landfills.[19][20] There is also the issue of simplifying the disposal of batteries by excluding them all from domestic waste, so that the most toxic batteries are diverted from general waste streams.
Disposal varies by jurisdiction. For example, the state of California considers all batteries as hazardous waste when discarded, and has banned the disposal of batteries in domestic waste.[21] In Europe, battery disposal is controlled by the WEEE Directive and Battery Directive regulations, and as such alkaline batteries must not be thrown in with domestic waste. In the EU, most stores that sell batteries are required by law to accept old batteries for recycling.
Recycling
The use of disposable batteries increases by 5–6% every year. In the past, used batteries ended up at landfill sites, but in 2004, disposal of alkaline batteries at landfill sites was forbidden by an EU regulation. EU member countries are committed to recycling 50% of alkaline batteries by 2016. The need for recycling thus amounts to 125000tons per year. The share of alkaline batteries is approximately 80% of the whole.[citation needed]
In the US, only one state, California, requires all alkaline batteries to be recycled. Vermont also has a statewide alkaline battery collection program.[22] In other US states, individuals can purchase battery recycling kits used to ship batteries to recyclers. Some stores such as IKEA also collect alkaline batteries for recycling. However, some chain stores that advertise battery recycling (such as Best Buy) accept rechargeable batteries only, and generally do not accept alkaline batteries.[23]
For recycling, the metals from crushed alkaline batteries are mechanically separated, and the waste black mass is treated chemically to separate zinc, manganese dioxide and potassium hydroxide.
↑ This alkali particularly attacks aluminium, a common material for flashlights, which can be damaged by leaking alkaline batteries.
Related Research Articles
In chemistry and manufacturing, electrolysis is a technique that uses direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially important as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell. The voltage that is needed for electrolysis to occur is called the decomposition potential. The word "lysis" means to separate or break, so in terms, electrolysis would mean "breakdown via electricity."
A nickel–metal hydride battery is a type of rechargeable battery. The chemical reaction at the positive electrode is similar to that of the nickel–cadmium cell (NiCd), with both using nickel oxide hydroxide (NiOOH). However, the negative electrodes use a hydrogen-absorbing alloy instead of cadmium. NiMH batteries can have two to three times the capacity of NiCd batteries of the same size, with significantly higher energy density, although only about half that of lithium-ion batteries.
The nickel–cadmium battery is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes. The abbreviation Ni–Cd is derived from the chemical symbols of nickel (Ni) and cadmium (Cd): the abbreviation NiCad is a registered trademark of SAFT Corporation, although this brand name is commonly used to describe all Ni–Cd batteries.
Manganese dioxide is the inorganic compound with the formula MnO 2. This blackish or brown solid occurs naturally as the mineral pyrolusite, which is the main ore of manganese and a component of manganese nodules. The principal use for MnO 2 is for dry-cell batteries, such as the alkaline battery and the zinc–carbon battery. MnO 2 is also used as a pigment and as a precursor to other manganese compounds, such as KMnO 4. It is used as a reagent in organic synthesis, for example, for the oxidation of allylic alcohols. MnO 2 has an α-polymorph that can incorporate a variety of atoms in the "tunnels" or "channels" between the manganese oxide octahedra. There is considerable interest in α-MnO 2 as a possible cathode for lithium-ion batteries.
A primary battery or primary cell is a battery that is designed to be used once and discarded, and it is not rechargeable unlike a secondary cell. In general, the electrochemical reaction occurring in the cell is not reversible, rendering the cell unrechargeable. As a primary cell is used, chemical reactions in the battery use up the chemicals that generate the power; when they are gone, the battery stops producing electricity. In contrast, in a secondary cell, the reaction can be reversed by running a current into the cell with a battery charger to recharge it, regenerating the chemical reactants. Primary cells are made in a range of standard sizes to power small household appliances such as flashlights and portable radios.
A dry cell is a type of electric battery, commonly used for portable electrical devices. Unlike wet cell batteries, which have a liquid electrolyte, dry cells use an electrolyte in the form of a paste, and are thus less susceptible to leakage.
A zinc–air battery is a metal–air electrochemical cell powered by the oxidation of zinc with oxygen from the air. During discharge, a mass of zinc particles forms a porous anode, which is saturated with an electrolyte. Oxygen from the air reacts at the cathode and forms hydroxyl ions which migrate into the zinc paste and form zincate, releasing electrons to travel to the cathode. The zincate decays into zinc oxide and water returns to the electrolyte. The water and hydroxyl from the anode are recycled at the cathode, so the water is not consumed. The reactions produce a theoretical voltage of 1.65 Volts, but is reduced to 1.35–1.4 V in available cells.
A silver oxide battery is a primary cell using silver oxide as the cathode material and zinc for the anode. These cells maintain a nearly constant nominal voltage during discharge until fully depleted. They are available in small sizes as button cells, where the amount of silver used is minimal and not a prohibitively expensive contributor to the overall product cost.
A zinc–carbon battery (or carbon zinc battery in U.S. English) is a dry cell primary battery that provides direct electric current from the electrochemical reaction between zinc (Zn) and manganese dioxide (MnO2) in the presence of an ammonium chloride (NH4Cl) electrolyte. It produces a voltage of about 1.5 volts between the zinc anode, which is typically constructed as a cylindrical container for the battery cell, and a carbon rod surrounded by a compound with a higher Standard electrode potential (positive polarity), known as the cathode, that collects the current from the manganese dioxide electrode. The name "zinc-carbon" is slightly misleading as it implies that carbon is acting as the oxidizing agent rather than the manganese dioxide.
A mercury battery is a non-rechargeable electrochemical battery, a primary cell. Mercury batteries use a reaction between mercuric oxide and zinc electrodes in an alkaline electrolyte. The voltage during discharge remains practically constant at 1.35 volts, and the capacity is much greater than that of a similarly sized zinc-carbon battery. Mercury batteries were used in the shape of button cells for watches, hearing aids, cameras and calculators, and in larger forms for other applications.
A nickel–zinc battery is a type of rechargeable battery similar to nickel–cadmium batteries, but with a higher voltage of 1.6 V.
A rechargeable alkaline battery, also known as alkaline rechargeable or rechargeable alkaline manganese (RAM), is a type of alkaline battery that is capable of recharging for repeated use. The formats include AAA, AA, C, D, and snap-on 9-volt batteries. Rechargeable alkaline batteries are manufactured fully charged and have the ability to hold their charge for years, longer than nickel-cadmium and nickel-metal hydride batteries, which self-discharge. Rechargeable alkaline batteries can have a high recharging efficiency and have less environmental impact than disposable cells.
The Leclanché cell is a battery invented and patented by the French scientist Georges Leclanché in 1866. The battery contained a conducting solution (electrolyte) of ammonium chloride, a cathode of carbon, a depolarizer of manganese dioxide (oxidizer), and an anode of zinc (reductant). The chemistry of this cell was later successfully adapted to manufacture a dry cell.
Batteries provided the primary source of electricity before the development of electric generators and electrical grids around the end of the 19th century. Successive improvements in battery technology facilitated major electrical advances, from early scientific studies to the rise of telegraphs and telephones, eventually leading to portable computers, mobile phones, electric cars, and many other electrical devices.
Eco-Cement is a brand-name for a type of cement which incorporates reactive magnesia, another hydraulic cement such as Portland cement, and optionally pozzolans and industrial by-products, to reduce the environmental impact relative to conventional cement. One problem with the commercialization of this cement, other than the conservatism of the building industry, is that the feedstock magnesite is rarely mined.
An electric battery is a source of electric power consisting of one or more electrochemical cells with external connections for powering electrical devices. When a battery is supplying power, its positive terminal is the cathode and its negative terminal is the anode. The terminal marked negative is the source of electrons. When a battery is connected to an external electric load, those negatively charged electrons flow through the circuit and reach to the positive terminal, thus cause a redox reaction by attracting positively charged ions, cations. Thus converts high-energy reactants to lower-energy products, and the free-energy difference is delivered to the external circuit as electrical energy. Historically the term "battery" specifically referred to a device composed of multiple cells; however, the usage has evolved to include devices composed of a single cell.
The lithium–air battery (Li–air) is a metal–air electrochemical cell or battery chemistry that uses oxidation of lithium at the anode and reduction of oxygen at the cathode to induce a current flow.
A zinc-ion battery or Zn-ion battery (abbreviated as ZIB) uses zinc ions (Zn2+) as the charge carriers. Specifically, ZIBs utilize Zn metal as the anode, Zn-intercalating materials as the cathode, and a Zn-containing electrolyte. Generally, the term zinc-ion battery is reserved for rechargeable (secondary) batteries, which are sometimes also referred to as rechargeable zinc metal batteries (RZMB). Thus, ZIBs are different than non-rechargeable (primary) batteries which use zinc, such as alkaline or zinc–carbon batteries.
A silver–cadmium battery is a type of rechargeable battery using cadmium metal as its negative terminal, silver oxide as the positive terminal, and an alkaline water-based electrolyte. It produces about 1.1 volts per cell on discharge, and about 40 watthours per kilogram specific energy density. A silver–cadmium battery provides more energy than a nickel–cadmium cell of comparable weight. It has higher life cycle expectancy than silver–zinc cells, but lower terminal voltage and lower energy density. However, the high cost of silver and the toxicity of cadmium restrict its applications.
Battery leakage is the escape of chemicals, such as electrolytes, within an electric battery due to generation of pathways to the outside environment caused by factory or design defects, excessive gas generation, or physical damage to the battery. The leakage of battery chemical often causes destructive corrosion to the associated equipment and may pose a health hazard.
↑ "Absatzzahlen 2008"(PDF) (in German). Interessenorganisation Batterieentsorgung. Archived from the original(PDF) on March 25, 2012. Retrieved July 29, 2014.
↑ McComsey, Dennis W. "Chapter 8: Zinc-Carbon Batteries (LeClanché and Zinc-Chloride Cell Systems". In Linden & Reddy (2002), p.8-3.
↑ Scarr, Robert F.; Hunter, James C.; Slezak, Philip J. "Chapter 10: Alkaline–Mangangese Dioxide Batteries". In Linden & Reddy (2002), p.10-6.
↑ "...the capacity of a battery generally decreases with increasing discharge current." Linden, David (2002a). "Chapter 3: Factors Affecting Battery Performance". In Linden & Reddy (2002), p.3-5.
↑ "Batteries". Waste Prevention Information Exchange of ion due to graphite. California Department of Resources Recycling and Recovery (CalRecycle). Retrieved September 5, 2012.
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