Battery

Background

Primary cells

Moderate energy primary cells

Medium to high energy primary cells

Secondary cells

Moderate energy storage cells

High energy storage batteries

Resources

In recent decades, billions of battery-powered devices have been sold. The demand for batteries continues to increase rapidly, with the global market in 2006 at around $50 billion. Without batteries, portable electronics—apart from solar-powered calculators—would be impossible.

If two metals are immersed in an aqueous solution that can conduct electricity (electrolyte), they will have different tendencies to dissolve in the solution. A difference in voltage arises because one of the metals appears positive or negative relative to the other.

The combination of two metals (electrodes) in an aqueous solution for the purpose of producing electrical energy from chemical energy is referred to as a galvanic cell. A battery is a set of two or more galvanic cells connected in a series or parallel. (Though not strictly correct usage, a single galvanic cell is also frequently referred to as a battery.) Each cell contains two types of electrodes, an anode (positive electrode) and a cathode (negative electrode), that together provide and absorb electrons with sufficient voltage (electromotive force) to operate useful machines or devices. The electromotive force for every cell reaction that is well understood can be calculated, and the voltage of an actual cell will not exceed this value.

Metals and other conductors can be arranged in an electrochemical, or electromotive, series in which each conductor’s tendency to lose electrons relative to another conductor is ranked. The higher the electric potential, the more likely the metal is to appear electrically positive. In terms of electric potential, carbon has a higher potential than gold, gold a higher potential than silver; this sequence is followed in order by copper, tin, lead, iron, and zinc.

Background

Between 1790 and 1800, Luigi Galvani (1737–1798), lecturer in anatomy at the University of Bologna, and Alessandro Volta (1745–1827), professor of physics at Pavia University, began the science of electrochemistry.

Galvani observed the effect of a copper probe on the muscles of a frog hung from an iron hook (the muscles twitched), and Volta interpreted this phenomena as the result of two metals being near each other, separated by an electrolyte (the blood of the frog).

Volta later built a stack of alternating zinc and silver disks separated by layers of paper or cloth soaked in a solution of sodium hydroxide or brine. He thus created a stable source of electrical current.

In 1834 Michael Faraday (1791–1867), inspired by Volta’s results, derived the quantitative laws of electrochemistry. These established the fundamental relationships between chemical energy and electrical energy. Following Faraday’s work, the following cells were developed:

• Copper and zinc in sulfuric acid (1836)
• Platinum cathode immersed in dilute nitric acid with a zinc anode in another compartment containing sulfuric acid
• Carbon cathode immersed in dilute nitric acid with a zinc anode in another compartment containing sulfuric acid
• Lead/acid battery (1859)
• LeClanche wet cell with a zinc anode and a cathode of naturally occurring manganese dioxide (1866)
• The first dry cell, consisting of a moistened cathode and a swollen starch or plaster of paris separator (1888) battery, dry cell nickel/cadmium and nickel/iron cells developed (1895-1905)
• Silver oxide/zinc cell (1930s and 1940s)

If an incandescent lamp is connected to the two poles of a battery, an electric current flows through the lamp, illuminating it. As current flows through the electrolyte from the positive electrode to the negative one, gas bubbles are deposited on the electrodes, and an internal resistance to current flow builds up. To prevent this depolarization, the buildup of hydrogen gas at the positive electrode (anode) must be prevented to keep the cell functioning.

In the LeClanche cell, depolarization is prevented by enclosing the carbon anode with a mixture of manganese dioxide and graphite. The cell uses a zinc negative pole (cathode) and an ammonium chloride electrolyte. The potential difference between the poles is 1.3 volts. The potential difference does not depend on the size of the cell. (However, the size of the cell does affect the current intensity or amperage that can be delivered.) Chemical energy, which is converted into electrical energy, results as the zinc electrode dissolves and is consumed. Thus the zinc must be renewed from time to time. Cells in which the electrodes are consumed are called primary cells.

A secondary cell can be restored to its original state by charging it, i.e., passing an electric current through it so that the electrodes are regenerated. These cells are also called storage cells or accumulators. They are usually used as groups of two or more cells. A commonly used storage cell consists of lead plates with a dilute sulfuric acid electrolyte. A layer of lead sulphate forms on the plates. When the storage cell is charged, the layer on the anode plate changes to lead dioxide, and the cathode is reduced to lead. Thus one electrode consists of lead and the other of lead dioxide. The electrodes and electrolyte together function as a galvanic cell. The stored chemical energy is converted back to electrical energy on discharging. The nickel-iron storage cell, another secondary cell, uses a potassium hydroxide electrolyte. The lead storage cell produces a potential difference of about 2 volts; the nickel-iron cell a difference of 1.36 volts.

In a dry cell, the electrolyte is in the form of a paste instead of a liquid. Higher voltages are produced by connecting the cells in series. Higher current intensities are produced by connecting cells in parallel. All cells produce direct current, i.e., electric current that flows in one direction.

Primary cells

Primary cells are designed to be discharged only once. This is despite the fact that all electrodes must theoretically participate in a reversible reaction when current is generated. The reason that the primary cell reaction is not reversible has to do with reactions that prevent or limit the efficiency of recharging. For example, a magnesium anode decomposes to produce magnesium ions and electrons. The magnesium ions react with water to produce magnesium hydroxide, which causes the cell to swell, and hydrogen gas. Any attempt to recharge the cell would only generate more hydrogen gas at the oxide surface, because the voltage required to generate hydrogen is less than that required to redeposit the magnesium.

Moderate energy primary cells

Zinc/manganese dioxide systems

The cell developed by Georges LeClanche in 1866 used inexpensive, readily available ingredients. It therefore quickly became a commercial success. The anode is a zinc alloy sheet or cup (the alloy contains small amounts of lead, cadmium, and mercury). The electrolyte is an aqueous solution of zinc chloride with solid ammonium chloride present. The cathode is manganese dioxide blended with either graphite or acetylene black to conduct electrons to the oxide. The system is relatively tolerant of many impurities. These cells are used in barricade flashers, flashlights, garage door openers, lanterns, pen lights, radios, small lighted toys and novelties, and in others.

The zinc chloride cell without ammonium chloride was patented in 1899, but the technology from commercially producing such cells did not prove practical until about 70 years later. Currently zinc chloride cells deliver more than seven times the energy density of the original LeClanche cell. This cell is used in same applications as the LeClanche cell.

Zinc/manganese dioxide alkaline cells

The zinc/manganese dioxide alkaline cell’s anode consists of finely divided zinc. The cathode is a highly compacted mixture of very pure manganese dioxide and graphite. The cells operate with higher efficiency than the zinc chloride or LeClanche cells at temperatures below 32^→•F(0^→•C). Manganese/manganese dioxide cells have much higher energy densities than zinc chloride systems. Cylindrical batteries are used in radios, shavers, electronic flash, movie cameras, tape recorders, television sets, cassette players, clocks, and camera motor drives. Miniature batteries are used in calculators, toys, clocks, watches, and cameras.

Medium to high energy primary cells

Mercuric oxide/zinc cells

Mercuric oxide/zinc cells use alkaline electrolytes and are frequently used in small button cells. The cell has about five to eight times the energy density available in the LeClanche cell and four times that in an alkaline manganese dioxide/zinc cell. The cell provides a very reliable voltage, and is used as a standard reference cell. These cells are used for walkie-talkies, hearing aids, watches, calculators, microphones, and cameras.

Silver oxide/zinc cells

Silver oxide/zinc cells use cellophane separators to keep the silver from dissolving and the cells from self discharging. The system is very popular with makers of hearing aids and watches because the high conductivity of the silver cathode reaction product gives the cell a very constant voltage to the end of its life. These cells are also used for reference voltage sources, cameras, instruments, watches, and calculators.

Lithium (nonaqueous electrolyte) cells

Lithium/iron sulfide cells take advantage of the high electrochemical potential of lithium and low cost of iron sulfide. The high reactivity of lithium with water requires that the cells use a nonaqueous electrolyte from which water is removed to levels of 50 parts per million (ppm).

Lithium/manganese dioxide cells are slowly increasing in commercial importance. The voltage provides a high energy density, and the materials are readily available and relatively inexpensive.

Lithium/copper monofluoride cells are used extensively in cameras and smaller devices. They provide high voltage, high power density, long shelf life, and good low temperature performance.

Lithium/thionyl chloride cells have very high energy densities and power densities. The cells also function better at lower temperatures than do other common cells.

Lithium/sulphur cells are used for cold weather use and in emergency power units.

Air-depolarized cells

Zinc/air cells are high energy can be obtained in a galvanic cell by using the oxygen of air as a “liquid” cathode material with an anode such as zinc. If the oxygen is reduced in the part of the cell designed for that purpose and prevented from reaching the anode, the cell can hold much more anode and electrolyte volume.

Aluminum/air cells have difficulty protecting the aluminum from the electrolyte during storage. Despite much research on this type of cell, aluminum/air cells are not in much current use.

Secondary cells

Secondary cells are designed so that the power withdrawn can be replaced by connecting the cell to an outside source of direct current power. The chemical reactions are reversed by suitably applying voltage and current in the direction opposite to the original discharge.

Moderate energy storage cells

Lead secondary cells

The lead/acid rechargeable battery system has been in use since the mid-1950s. It is the most widely used rechargeable portable power source. Reasons for the success of this system have included: great flexibility in delivery currents; good cycle life with high reliability over hundreds of cycles; low cost; relatively good shelf life; high cell voltages; ease of casting, welding, and recovery of lead.

The chief disadvantage of this battery is its high weight.

Nickel electrode cells with alkaline electrolytes

Nickel/cadmium cells provide portable rechargeable power sources for garden, household tools, and appliance use. The system carries exceptionally high currents at relatively constant voltage. The cells are, however, relatively expensive. These cells are used for portable hand tools and appliances, shavers, toothbrushes, photoflash equipment, tape recorders, radios, television sets, cassette players and recorders, calculators, personal pagers, and laptop computers.

Alkaline zinc/manganese dioxide cells

Alkaline zinc/manganese dioxide systems been developed and used as special batteries for television sets and certain portable tools or radios.

High energy storage batteries

Silver/zinc cells

Silver/zinc cells are expensive. They are chiefly used when high power density, good cycling efficiency, and low weight and volume are critical, and where poorer cycle life and cost can be tolerated. They are used in primarily four areas: under water, on the ground, in the atmosphere, and in space.

KEY TERMS

Anode— A positively charged electrode.

Battery— A battery is a container, or group of containers, holding electrodes and an electrolyte for producing electric current by chemical reaction and storing energy. The individual containers are called “cells.” Batteries produce direct current (DC).

Cathode— A negatively charged electrode.

Direct current (DC)— Electrical current that always flows in the same direction.

Electrode— The conductor by which electricity enters or leaves a galvanic cell.

Electrolyte— The medium of ion transfer between anode and cathode within the cell. Usually liquid or paste that is either acidic or basic.

Galvanic cell— Combination of electrodes separated by electrolyte capable of producing electric energy by electrochemical action.

Primary cell— A galvanic cell designed to deliver its rated capacity once and then be discarded.

Secondary cell— A galvanic cell designed for reconstitution of power by accepting electrical power from an outside source.

Lithium secondary cells

Lithium secondary cells are attractive because of their high energy densities.

Sodium/sulfur systems

Sodium/sulfur systems are high-temperature batteries that operate well even at 177^→•F (80.6^→•C).

See also Cell, electrochemical; Electricity; Electrical conductivity; Electric conductor.

Resources

OTHER

Buchmann, Isidor. Batteries in a Portable World: A Handbook on Rechargeable Batteries for Non-Engineers. Cadex Electronics Inc., 2006. <http://www.buchmann.ca/> (accessed October 19, 2006).

Randall Frost

Battery

If two metals are immersed in an aqueous solution that can conduct electricity (electrolyte ), they will have different tendencies to dissolve in the solution. A difference in voltage arises because one of the metals appears positive or negative relative to the other.

The combination of two metals (electrodes) in an aqueous solution for the purpose of producing electrical energy from chemical energy is referred to as a galvanic cell. A battery is a set of two or more galvanic cells connected in a series or parallel . (Though not strictly correct usage, a single galvanic cell is also frequently referred to as a battery.) Each cell contains two types of electrodes, an anode (positive electrode) and a cathode (negative electrode), that together provide and absorb electrons with sufficient voltage (electromotive force ) to operate useful machines or devices. The electromotive force for every cell reaction that is well understood can be calculated, and the voltage of an actual cell will not exceed this value.

Metals and other conductors can be arranged in an electrochemical, or electromotive, series in which each conductor's tendency to lose electrons relative to another conductor is ranked. The higher the electric potential, the more likely the metal is to appear electrically positive. In terms of electric potential, carbon has a higher potential than gold, gold a higher potential than silver; this sequence is followed in order by copper , tin, lead , iron , and zinc.

Background

Between 1790 and 1800, Luigi Galvani, lecturer in anatomy at the University of Bologna, and Alessandro Volta, professor of physics at Pavia University, began the science of electrochemistry. Galvani observed the effect of a copper probe on the muscles of a frog hung from an iron hook (the muscles twitched), and Volta interpreted this phenomena as the result of two metals being near each other, separated by an electrolyte (the blood of the frog).

Volta later built a stack of alternating zinc and silver disks separated by layers of paper or cloth soaked in a solution of sodium hydroxide or brine. He thus created a stable source of electrical current.

In 1834 Michael Faraday, inspired by Volta's results, derived the quantitative laws of electrochemistry. These established the fundamental relationships between chemical energy and electrical energy. Following Faraday's work, the following cells were developed:

• Copper and zinc in sulfuric acid (1836)
• Platinum cathode immersed in dilute nitric acid with a zinc anode in another compartment containing sulfuric acid
• Carbon cathode immersed in dilute nitric acid with a zinc anode in another compartment containing sulfuric acid
• Lead/acid battery (1859)
• LeClanche wet cell with a zinc anode and a cathode of naturally occurring manganese dioxide (1866)
• The first dry cell, consisting of a moistened cathode and a swollen starch or plaster of paris separator (1888) battery, dry cell nickel/cadmium and nickel/iron cells developed (1895-1905)
• Silver oxide/zinc cell (1930s and 1940s)

If an incandescent lamp is connected to the two poles of a battery, an electric current flows through the lamp, illuminating it. As current flows through the electrolyte from the positive electrode to the negative one, gas bubbles are deposited on the electrodes, and an internal resistance to current flow builds up. To prevent this depolarization, the buildup of hydrogen gas at the positive electrode (anode) must be prevented to keep the cell functioning.

In the LeClanche cell, depolarization is prevented by enclosing the carbon anode with a mixture of manganese dioxide and graphite. The cell uses a zinc negative pole (cathode) and an ammonium chloride electrolyte. The potential difference between the poles is 1.3 volts. The potential difference does not depend on the size of the cell. (However, the size of the cell does affect the current intensity

or amperage that can be delivered.) Chemical energy, which is converted into electrical energy, results as the zinc electrode dissolves and is consumed. Thus the zinc must be renewed from time to time. Cells in which the electrodes are consumed are called primary cells.

A secondary cell can be restored to its original state by charging it, i.e., passing an electric current through it so that the electrodes are regenerated. These cells are also called storage cells or accumulators. They are usually used as groups of two or more cells. A commonly used storage cell consists of lead plates with a dilute sulfuric acid electrolyte. A layer of lead sulphate forms on the plates. When the storage cell is charged, the layer on the anode plate changes to lead dioxide, and the cathode is reduced to lead. Thus one electrode consists of lead and the other of lead dioxide. The electrodes and electrolyte together function as a galvanic cell. The stored chemical energy is converted back to electrical energy on discharging. The nickel-iron storage cell, another secondary cell, uses a potassium hydroxide electrolyte. The lead storage cell produces a potential difference of about 2 volts; the nickel-iron cell a difference of 1.36 volts.

In a dry cell, the electrolyte is in the form of a paste instead of a liquid. Higher voltages are produced by connecting the cells in series. Higher current intensities are produced by connecting cells in parallel. All cells produce direct current, i.e., electric current that flows in one direction.

Primary cells

Primary cells are designed to be discharged only once. This is despite the fact that all electrodes must theoretically participate in a reversible reaction when current is generated. The reason that the primary cell reaction is not reversible has to do with reactions that prevent or limit the efficiency of recharging. For example, a magnesium anode decomposes to produce magnesium ions and electrons. The magnesium ions react with water to produce magnesium hydroxide, which causes the cell to swell, and hydrogen gas. Any attempt to recharge the cell would only generate more hydrogen gas at the oxide surface, because the voltage required to generate hydrogen is less than that required to redeposit the magnesium.

Moderate energy primary cells

Zinc/manganese dioxide systems

The cell developed by Georges LeClanche in 1866 used inexpensive, readily available ingredients. It therefore quickly became a commercial success. The anode is a zinc alloy sheet or cup (the alloy contains small amounts of lead, cadmium, and mercury). The electrolyte is an aqueous solution of zinc chloride with solid ammonium chloride present. The cathode is manganese dioxide blended with either graphite or acetylene black to conduct electrons to the oxide. The system is relatively tolerant of many impurities. These cells are used in barricade flashers, flashlights, garage door openers, lanterns, pen lights, radios, small lighted toys and novelties, and in others.

The zinc chloride cell without ammonium chloride was patented in 1899, but the technology from commercially producing such cells did not prove practical until about 70 years later. Currently zinc chloride cells deliver more than seven times the energy density of the original LeClanche cell. This cell is used in same applications as the LeClanche cell.

Zinc/manganese dioxide alkaline cells

The zinc/manganese dioxide alkaline cell's anode consists of finely divided zinc. The cathode is a highly compacted mixture of very pure manganese dioxide and graphite. The cells operate with higher efficiency than the zinc chloride or LeClanche cells at temperatures below 32°F (0°C). Manganese/manganese dioxide cells have much higher energy densities than zinc chloride systems. Cylindrical batteries are used in radios, shavers, electronic flash, movie cameras, tape recorders, television sets, cassette players, clocks, and camera motor drives. Miniature batteries are used in calculators, toys, clocks, watches, and cameras.

Medium to high energy primary cells

Mercuric oxide/zinc cells

Mercuric oxide/zinc cells use alkaline electrolytes and are frequently used in small button cells. The cell has about five to eight times the energy density available in the LeClanche cell and four times that in an alkaline manganese dioxide/zinc cell. The cell provides a very reliable voltage, and is used as a standard reference cell. These cells are used for walkie-talkies, hearing aids, watches, calculators, microphones, and cameras.

Silver oxide/zinc cells

Silver oxide/zinc cells use cellophane separators to keep the silver from dissolving and the cells from self discharging. The system is very popular with makers of hearing aids and watches because the high conductivity of the silver cathode reaction product gives the cell a very constant voltage to the end of its life. These cells are also used for reference voltage sources, cameras, instruments, watches, and calculators.

Lithium (nonaqueous electrolyte) cells

Lithium/iron sulfide cells take advantage of the high electrochemical potential of lithium and low cost of iron sulfide. The high reactivity of lithium with water requires that the cells use a nonaqueous electrolyte from which water is removed to levels of 50 ppm.

Lithium/manganese dioxide cells are slowly increasing in commercial importance. The voltage provides a high energy density, and the materials are readily available and relatively inexpensive.

Lithium/copper monofluoride cells are used extensively in cameras and smaller devices. They provide high voltage, high power density, long shelf life, and good low temperature performance.

Lithium/thionyl chloride cells have very high energy densities and power densities. The cells also function better at lower temperatures than do other common cells.

Lithium/sulphur cells are used for cold weather use and in emergency power units.

Air-depolarized cells

Zinc/air cells are high energy can be obtained in a galvanic cell by using the oxygen of air as a "liquid" cathode material with an anode such as zinc. If the oxygen is reduced in the part of the cell designed for that purpose and prevented from reaching the anode, the cell can hold much more anode and electrolyte volume .

Aluminum/air cells have difficulty protecting the aluminum from the electrolyte during storage. Despite much research on this type of cell, aluminum/air cells are not in much current use.

Secondary cells

Secondary cells are designed so that the power withdrawn can be replaced by connecting the cell to an outside source of direct current power. The chemical reactions are reversed by suitably applying voltage and current in the direction opposite to the original discharge.

Moderate energy storage cells

Lead secondary cells

The lead/acid rechargeable battery system has been in use since the mid-1950s. It is the most widely used rechargeable portable power source. Reasons for the success of this system have included: great flexibility in delivery currents; good cycle life with high reliability over hundreds of cycles; low cost; relatively good shelf life; high cell voltages; ease of casting, welding , and recovery of lead.

The chief disadvantage of this battery is its high weight.

Nickel electrode cells with alkaline electrolytes

Nickel/cadmium cells provide portable rechargeable power sources for garden, household tools, and appliance use. The system carries exceptionally high currents at relatively constant voltage. The cells are, however, relatively expensive. These cells are used for portable hand tools and appliances, shavers, toothbrushes, photoflash equipment, tape recorders, radios, television sets, cassette players and recorders, calculators, personal pagers, and laptop computers.

Alkaline zinc/manganese dioxide cells

Alkaline zinc/manganese dioxide systems been developed and used as special batteries for television sets and certain portable tools or radios.

High energy storage batteries

Silver/zinc cells

Silver/zinc cells are expensive. They are chiefly used when high power density, good cycling efficiency, and low weight and volume are critical, and where poorer cycle life and cost can be tolerated. They are used in primarily four areas: under water, on the ground, in the atmosphere, and in space .

Lithium secondary cells

Lithium secondary cells are attractive because of their high energy densities.

Sodium/sulfur systems

Sodium/sulfur systems are high-temperature batteries that operate well even at 177°F (80.6°C).

See also Cell, electrochemical; Electricity; Electrical conductivity; Electric conductor.

Resources

books

Macaulay, David. The New Way Things Work. Boston: Houghton Mifflin Company, 1998.

Meyers, Robert A., Encyclopedia of Physics Science and Technology. New York, NY: Academic Press, Inc., 1992.

KEY TERMS

Anode

—A positively charged electrode.

Battery

—A battery is a container, or group of containers, holding electrodes and an electrolyte for producing electric current by chemical reaction and storing energy. The individual containers are called "cells". Batteries produce direct current (DC).

Cathode

—A negatively charged electrode.

Direct current (DC)

—Electrical current that always flows in the same direction.

Electrode

—The conductor by which electricity enters or leaves a galvanic cell.

Electrolyte

—The medium of ion transfer between anode and cathode within the cell. Usually liquid or paste that is either acidic or basic.

Galvanic cell

—Combination of electrodes separated by electrolyte capable of producing electric energy by electrochemical action.

Primary cell

—A galvanic cell designed to deliver its rated capacity once and then be discarded.

Secondary cell

—A galvanic cell designed for reconstitution of power by accepting electrical power from an outside source.

Battery

Background

Benjamin Franklin's famous experiment to attract electricity by flying a kite in a lightning storm was only one of many late eighteenth- and early nineteenth-century experiments conducted to learn about electricity. The first battery was constructed in 1800 by Italian Alessandro Volta. The so-called voltaic pile consisted of alternating discs of silver and zinc separated by leather or pasteboard that had been soaked in salt water, lye, or some alkaline solution. Strips of metal at each end of the pile were connected to small cups filled with mercury. When Volta touched both cups of mercury with his fingers, he received an electric shock; the more discs he assembled, the greater the jolt he received.

Volta's discovery led to further experimentation. In 1813, Sir Humphrey Davy constructed a pile with 2,000 pairs of discs in the basement of the Royal Institution of London. Among other applications, Davy used the electricity he produced for electrolysis—catalyzing chemical reactions by passing a current through substances (Davy separated sodium and potassium from compounds). Only a few years later, Michael Faraday discovered the principle of electromagnetic induction, using a magnet to induce electricity in a coiled wire. This technique is at the heart of the dynamos used to produce electricity in power plants today. (While a dynamo produces alternating current (AC) in which the flow of electricity shifts direction regularly, batteries produce direct current (DC) that flows in one direction only.) A lead-acid cell capable of producing a very large amount of current, the forerunner of today's automobile battery, was devised in 1859 by Frenchman Gaston Planté.

In the United States, Thomas Edison was experimenting with electricity from both batteries and dynamos to power the light bulb, which began to spread in the United States in the early 1880s. During the 1860s, Georges Leclanché invented the wet cell, which, though heavy because of its liquid components, could be sold and used commercially. By the 1870s and 1880s, the Leclanché cell was being produced using dry materials and was used for a number of tasks, including providing power for Alexander Graham Bell's telephone and for the newly-invented flashlight. Batteries were subsequently called upon to provide power for many other inventions, such as the radio, which became hugely popular in the years following World War I. Today, more than twenty billion power cells are sold throughout the world each year, and each American uses approximately 27 batteries annually.

Design

All batteries utilize similar procedures to create electricity; however, variations in materials and construction have produced different types of batteries. Strictly speaking, what is commonly termed a battery is actually a group of linked cells. The following is a simplified description of how a battery works.

Two important parts of any cell are the anode and the cathode. The cathode is a metal that is combined, naturally or in the laboratory, with oxygen—the combination is called an oxide. Iron oxide (rust), although too fragile to use in a battery, is perhaps the most familiar oxide. Some other oxides are actually strong enough to be worked (cut, bent, shaped, molded, and so on) and used in a cell. The anode is a metal that would oxidize if it were allowed to and, other things being equal, is more likely to oxidize than the metal that forms part of the cathode.

A cell produces electricity when one end of a cathode and one end of an anode are placed into a third substance that can conduct electricity, while their other ends are connected. The anode draws oxygen atoms toward it, thereby creating an electric flow. If there is a switch in the circuit (similar to any wall or lamp switch), the circuit is not complete and electricity cannot flow unless the switch is in the closed position. If, in addition to the switch, there is something else in the circuit, such as a light bulb, the bulb will light from the friction of the electrons moving through it.

The third substance into which the anode and the cathode are placed is called an electrolyte. In many cases this material is a chemical combination that has the property of being alkaline. Thus, an alkaline battery is one that makes use of an alkaline electrolyte. A cell will not produce electricity by itself unless it is placed in a circuit that has been rendered complete by a simple switch, or by some other switching connection in the appliance using the battery.

Designing a cell can lead to many variations in type and structure. Not all electrolytes, for example, are alkaline. Additionally, the container for the electrolyte can act as both a container and either the cathode or the anode. Some cells draw their oxygen not from a cathode but right out of the air. Changes in the compositions of the anode and the cathode will provide more or less electricity. Precise adjustment of all of the materials used in a cell can affect the amount of electricity that can be produced, the rate of production, the voltage at which electricity is delivered through the lifetime of the cell, and the cell's ability to function at different temperatures.

All of these possibilities do, in fact, exist, and their various applications have produced the many different types of batteries available today (lithium, mercury, and so on). For years, however, the most common cell has been the 1.5 volt alkaline battery.

Different batteries function better in different circumstances. The alkaline 1.5 volt cell is ideal for photographic equipment, handheld computers and calculators, toys, tape recorders, and other "high drain" uses; it is also good in low temperatures. This cell has a sloping discharge characteristic—it loses power gradually, rather than ceasing to produce electricity suddenly—and will lose perhaps four percent of its power per year if left unused on a shelf.

Other types of batteries include a lithium/manganese dioxide battery, which has a flat discharge characteristic—it provides approximately the same amount of power at the beginning of its life as at the end—and can be used where there is a need for small, high-power batteries (smoke alarms, cameras, memory backups on computers, and so on). Hearing aids, pagers, and some other types of medical equipment frequently use zinc air button type batteries, which provide a high energy density on continuous discharge. A mercury battery is frequently used in many of the same applications as the zinc air battery, because it, too, provides a steady output voltage.

Raw Materials

This section, as well as the following section, will focus on alkaline batteries. In an alkaline battery, the cylinder that contains the cells is made of nickel-plated steel. It is lined with a separator that divides the cathode from the anode and is made of either layered paper or a porous synthetic material. The canister is sealed at one end with an asphalt or epoxy sealant that underlies a steel plate, and at the other with a brass nail driven through the cylinder. This nail is welded to a metal end cap and passed through an exterior plastic seal. Inside the cylinder, the cathode consists of a mixture of manganese dioxide, graphite, and a potassium hydroxide solution; the anode comprises zinc powder and a potassium hydroxide electrolyte.

The Manufacturing
Process

The cathode

• 1 In an alkaline battery, the cathode actually doubles as part of the container. Huge loads of the constituent ingredients—manganese dioxide, carbon black (graphite), and an electrolyte (potassium hydroxide in solution)—are delivered by train and mixed in very large batches at the production site. The mixture is then granulated and pressed or compacted into hollow cylinders called preforms. Depending on the size of the battery being made, several preforms may be stacked one on top of another in a battery. Alternatively, the series of preforms can be replaced by an extruded ring of the same material.
• 2 The preforms are next inserted into a nickel-plated steel can; the combination of the preforms and the steel can make up the cathode of the battery. In a large operation, the cans are made at the battery factory using standard cutting and forming techniques. An indentation is made near the top of the can, and an asphalt or epoxy sealant is placed above the indentation to protect against leakage.

The separator

• 3 A paper separator soaked in the electrolyte solution is then inserted inside the can against the preforms; the separator is made from several pieces of paper laid at crossgrains to each other (like plywood). Looking down at an open can, one would see what looks like a paper cup inserted into the can. The separator keeps the cathode material from coming into contact with the anode material. As an alternative, a manufacturer might use a porous synthetic fiber for the same purpose.

The anode

• 4 The anode goes into the battery can next. It is a gel composed primarily of zinc powder, along with other materials including a potassium hydroxide electrolyte. This gel has the consistency of a very thick paste. Rather than a solution, it is chemically a suspension, in which particles do not settle (though an appropriate filter could separate them). The gel does not fill the can to the top so as to allow space for the chemical reactions that will occur once the battery is put into use.

The seals

• 5 Though the battery is able to produce electricity at this point, an open cell is not practical and would exhaust its potential rapidly. The battery needs to be sealed with three connected components. The first, a brass "nail" or long spike, is inserted into the middle of the can, through the gel material and serves as a "current collector." The second is a plastic seal and the third a metal end cap. The nail, which extends about two-thirds of the way into the can, is welded to the metal end cap and then passed through the plastic seal.
• 6 This seal is significantly thinner in some places than in others, so that if too much gas builds up in the can, the seal will rupture rather than the entire battery. Some battery designs make use of a wax-filled hole in the plastic; excess gas pushes through the wax rather than rupturing the battery. The seal assembly meets the indentation made in the can at the beginning of the process and is crimped in place.
• 7 The opposite end of the can (the positive end of the battery) is then closed with a steel plate that is either welded in place or glued with an epoxy-type cement.

The label

• 8 Before the battery leaves the factory, a label is added identifying the type of battery, its size, and other information. The label is often paper that is simply glued to the battery. One large manufacturer has its label design printed on plastic shrink wrap: a loose fitting piece of heat-sensitive plastic is wrapped around the battery can and then exposed to a blast of heat that makes the plastic shrink down to fit tightly around the can.

Quality Control

Because battery technology is not especially new or exotic, quality control and its results are especially important as the basis for brand competition. The ability of a battery to resist corrosion, to operate well under a variety of conditions, to maintain a good shelf and usage life, and other factors, are the direct results of quality control. Batteries and ingredients are inspected and tested at almost all stages of the production process, and the completed batches are subjected to stringent tests.

Environmental Issues

Although making batteries does present some environmental obstacles, none are insurmountable. Zinc and manganese, the major chemicals in alkaline batteries, do not pose environmental difficulties, and both are considered safe by the Food and Drug Administration (FDA). The major potential pollutant in batteries is mercury, which commonly accompanies zinc and which was for many years added to alkaline batteries to aid conductivity and to prevent corrosion. In the mid-1980s, alkaline batteries commonly contained between five and seven percent mercury.

When it became apparent several years ago that mercury was an environmental hazard, manufacturers began seeking ways to produce efficient batteries without it. The primary method of doing this focuses on better purity control of ingredients. Today's alkaline batteries may contain approximately .025 percent mercury. Batteries with no added mercury at all (it is a naturally occurring element, so it would be difficult to guarantee a product free of even trace qualities) are available from some manufacturers and will be the industry-wide rule rather than the exception by the end of 1993.

The Future

Batteries are currently the focus of intense investigation by scientists and engineers around the world. The reason is simple: several key innovations depend on the creation of better batteries. Viable electric automobiles and portable electronic devices that can operate for long periods of time without needing to be recharged must wait until more lightweight and more powerful batteries are developed. Typical lead-acid batteries currently used in automobiles, for instance, are too bulky and cannot store enough electricity to be used in electric automobiles. Lithium batteries, while lightweight and powerful, are prone to leaking and catching fire.

In early 1993, scientists at Arizona State University announced that they had designed a new class of electrolytes by dissolving polypropylene oxide and polyethylene oxide into a lithium salt solution. The new electrolytes appear to be highly conductive and more stable than typical lithium electrolytes, and researchers are now trying to build prototype batteries that use the promising substances.

In the meantime, several manufacturers are developing larger, more powerful nickel-metal hydride batteries for use in portable computers. These new batteries are expected to appear in late 1994.

Where To Learn More

Books

Packaged Power. Duracell International Inc., 1981.

Periodicals

"Plastic May Recharge Battery's Future," Design News. November 17, 1986, p. 24.

Greenberg, Jeff. "Packing Power: Subnotebook Batteries, Power Management," PC Magazine. October 27, 1992, p. 113.

Leventon, William. "The Charge Toward a Better Battery: Designing a Long-Life Battery," Design News. November 23, 1992, p. 91.

Methvin, Dave. "Battery Contenders Face-Off in Struggle To Dominate Market," PC Week. November 12, 1990, p. S21.

Schmidt, K. F. "Rubbery Conductors Aim at Better Batteries," Science News. March 13, 1993, p. 166.

Zimmerman, Michael R. "Better Batteries on the Way: Nickel-Metal Hydride Is Short-Term Winner," PC Week. April 26, 1993, p. 25.

—Lawrence H. Berlow

Battery

Sections within this essay:

Background

In both criminal and civil law, a battery is the intentional touching of, or application of force to, the body of another person, in a harmful or offensive manner, and without consent. A battery is often confused with an assault, which is merely the act of threatening a battery, or of placing another in fear or apprehension of an impending and immediate battery. A battery is almost always preceded by an assault, which is why the terms are often used transitionally or combined, as in "assault and battery."

The Restatement (Second) of Torts, Sections 13 and 18, states that an actor commits a battery if he acts intentionally either to cause a harmful or offensive contact or to cause imminent apprehension of such a contact and a harmful or offensive contact actually occurs.

Criminal Battery

The difference between battery as a crime and battery as a civil tort is merely in the type of intent required. A criminal battery requires the presence of mens rea, or a criminal intent to do wrong, i.e., to cause a harmful or offensive contact. Accordingly, a defendant found guilty of the crime of battery is often sued by the defendant in a civil action for the same offense/incident.

Simple criminal battery is most often prosecuted as a misdemeanor. Repeat offenses or the specific nature of the offense may warrant more severe treatment. For example, in some states, a second or third offense against the same individual is a felony. In cases of domestic violence, many states do not permit battery charges to be dropped against the defendant, even at the request of the victim, because of the potential for repeat or escalated harm.

Most sexual crimes include elements of battery (since they are basically non-consensual contacts), and some states actually have penal codes listing the specific crime of "sexual battery."

Aggravated battery is a simple battery with an additional element of an aggravating factor. This is most often the addition of a weapon (whether use was real or merely threatened), and is almost always a felony offense. Other aggravated batteries include those committed against protected persons (children, the elderly or disabled, or governmental agents); those in which the victim suffers serious in-jury; or those occurring in a public transit vehicle or station, or school zone, or other protected place. These are all aggravating factors that will enhance simple misdemeanor batteries to the level of felonies.

Civil Battery (Tort)

A battery is an intentional tort. The elements to establish the tort of battery are the same as for criminal battery, excepting that criminal intent need not be present. For a tortious battery to occur, the requisite intent is merely to touch or make contact without consent. It need not be an intention to do wrong, and the wrongdoer need not intend to cause the particular harm that occurs.

Elements of a Battery

Intent

Battery is a general intent offense. This means that the actor need not intend the specific harm that will result from the unwanted contact, but only to commit an act of unwanted contact. This also means that gross negligence or even recklessness may provide the required intent or (in criminal matters) mens rea to find a battery.

The doctrine of transferred intent is also applicable. If one person intends to strike another, but the person moves out of the way to avoid being struck, causing the blow to hit a third person, both an assault (against the second person) and a battery (against the third person) have occurred, in both criminal and civil law.

This is important in the distinction between a battery and an assault. A battery involves actual contact. An assault is, in actuality, an incomplete battery; a person commits an assault if he or she intentionally places a person in apprehension of an impending battery. Conversely, if a persons intended only an assault (to cause apprehension of an imminent battery), and harmful or offensive contact actually occurs, the person has committed a battery as well as an assault.

This is also important in distinguishing accidental conduct. If a person violently slams into a fellow passenger on a moving public bus, there is no liability. But if, on the same public bus, there is only the slightest intentional touching of another, which is harmful or offensive and also non-consensual (such as reaching out and touching a woman's thigh), a battery has occurred.

Conversely, if there was only an intended assault, as in a person gesturing toward another in a menacing manner, and the person trips and actually crashes into the other person, both an assault and battery have occurred.

Contact

Non-consensual contact may be made with either a person or that person's extended personality. This means that if one person leans forward and yanks the jewelry necklace off another, a battery has occurred, even though the first person never actually touched the neck of the second person. If this act was preceded with an intent to cause the other to apprehend an impending violent yank of the necklace, both an assault and a battery have occurred. If the wrongdoer only intended an assault (causing the other to apprehend an impending violent yank of the necklace) but did not intend to actually complete the violent yank, and yet his hand made contact with, and actually yanked off the necklace, both an assault and a battery have occurred. In other words, if in the process of physically gesturing to violently yank the necklace off, contact is actually made and the necklace is pulled from the other's neck, a battery has occurred.

The tort rule of "extended personality" applies to both civil and criminal battery. For example, if a person threatens to spit into another's cup of coffee (clearly offensive and possibly harmful), and then proceeds to do so, both a criminal and civil battery have occurred. In another case involving the issue of extended contact, a Texas hotel manager was found guilty of a battery when he snatched away a patron's dinner plate in a "loud and offensive manner," even though the contact did not result in any physical harm to the diner.

Harm

A plaintiff or complainant in a case for battery does not have to prove an actual physical injury. Rather, the plaintiff must prove an unlawful and unpermitted contact with his or her person or property in a harmful or offensive manner. This, in and of itself, is deemed injurious. As in the case of the Texas hotel manager above, the harm may be offensive rather than physical, but equally worthy of compensation under the law.

Damages

Once there is palpable harm (be it physical, emotional, or monetary) all elements of a battery are present, and an aggrieved person may file charges. Of course, in criminal law, the state will file charges for battery, and the victim becomes a witness for the prosecution. In criminal court, the focus is on the guilt or innocence of the defendant and generally, no damages are available to the victim. However, harm may be so severe that he or she may qualify for assistance through a "victims' compensation fund."

Conversely, the victim of a battery may file a civil lawsuit stemming from the same incident, in which the defendant is charged with the tort of battery. In such a case, damages are typically compensatory (a monetary award), along with special relief such as injunctive or punitive. Substantial harm is not required, but nonetheless, there must be palpable harm. Compensatory damages may be for either/both economic and non-economic (emotional) harm. In the case of the necklace (above), the plaintiff may ask for monetary damages to cover property (the broken necklace); physical harm to her neck (economic damages for medical bills, if any, and non-economic damages for pain and suffering, if any); and emotional harm caused from the incident (the apprehension of a battery; the embarrassment when it actually occurred, etc.). In the case of transferred intent involving an assault and battery, there will likely be two plaintiffs: the person who was the intended victim of the battery (who sues for assault) and the person who was actually physically harmed (who sues for battery).

In medical malpractice cases involving unauthorized treatments or lack of informed consent (see below), the patient may sue for all costs and treatments/procedures associated with the treatment received. This is true, in many cases, even where the patient ultimately benefited from the unauthorized treatment (although this may be argued as a mitigating factor by defense).

Special Applications

Medical Battery

Virtually all states have recognized, either by express statute or common law, the right to receive information about one's medical condition, the treatment choices, risks associated with the treatments, and prognosis. The information must be in plain language terms that can readily be understood and in sufficient amounts such that a patient is able to make an "informed" decision about his or her health care. If the patient has received this information, any consent to treatment that is given will be presumed to be an "informed consent." A doctor who fails to obtain informed consent for non-emergency treatment may be charged with a civil and/or criminal offense, including a battery, for the unauthorized touching of the plaintiff's person.

Toxic Battery

Toxic torts (toxic exposure cases) typically involve claims of negligence or strict liability. However, in recent years, cognizable claims for toxic battery have succeeded in many courts. Again, the intent necessary to constitute a tortious battery need not be an intent to cause harm, but rather, the intent to do the act which ultimately causes the harm. Companies that manufacture chemicals that are known to be volatile or known to ultimately result in human contact are vulnerable to such claims. They may be sued for illegal disposal of toxic/hazardous materials as well as toxic battery if persons are harmed by leached chemicals or fumes in the air, ground, or water. The intent was not to harm others, but to dump the material in an illegal manner or location. This is a good example of gross negligence or recklessness so egregious as to constitute the requisite intent to commit battery under law.

Cases of toxic batteries began appearing in the late 1900s. In the early case of Gulden v. Crown Zellerbach Corp. (9th Circuit, 1989), the court held that exposing workers to PCBs (known carcinogens and harmful agents) at 500 times the maximum exposure allowed under EPA standards could constitute a battery. Toxic battery also became an element in many of the tobacco and breast implant cases. Obviously, such cases often involve multiple plaintiffs and multiple defendants, and may become class action suits in the case of widespread exposure to harm.

Sports

Most sports injuries, which are common in competitive, contact sports, are accidental. However, viable causes of action have been found in cases where sports players used excessive force in their tactics, to the detriment or harm of other players. Of course, the infamous fights among hockey players have resulted in numerous multi-party claims for battery.

Domestic Violence

Of all torts and crimes involving domestic relations, the most recurring ones involve charges of battery. This is true not only in spousal relations, but also in child abuse cases. Sexual offenses against other persons (including children) are both specific crimes as well as batteries. Unfortunately, spousal batteries often escalate into situations involving serious physical harm and property damage. Some courts permit batteries to the "extended personality," committed in the presence of the victim, because intentional destruction of items personal to a spouse are not uncommon in situations involving highly emotionally-charged marital discord. Moreover, in criminal battery, authorities recognize that victims may not want to press charges for fear of future harm or retaliation, especially in spousal battery. For this reason, prosecution may proceed even where the spousal victim is compelled to testify, or becomes an adverse witness for the state.

Defenses

Viable defenses to both tortious and criminal battery are similar. A defendant may raise lack of intent, especially in criminal battery, and in those circumstances tending to show accidental behavior. Another commonly-invoked defense, especially where a battery results in physical injury, is self-defense or the defense of others or property. These are the only true defenses, and other issues raised (lack of harm or injury, provocation, etc.) are merely mitigating factors. A defense of contributory negligence cannot be raised in a claim for intentional tort.

Additional Resources

Diamond, John L., et al. Understanding Torts. 2000.

Prosser. W. Prosser and Keeton on Torts. 5th ed., 1984. Sections 13-18.

Weaver, Russell L., John H. Bauman, et al. Torts: Cases, Problems, and Exercises. 2003.

Organizations

National Coalition Against Domestic Violence

P.O. Box 18749
Denver, CO 80218
Phone: (303) 839-1852
Fax: (303) 831-9251
URL: www.ncadv.org

Battery

A battery is a device for converting chemical energy into electrical energy. Batteries can consist of a single voltaic cell or a series of voltaic cells joined to each other. (In a voltaic cell, electrical energy is produced as the result of a chemical reaction between two different metals immersed in a solution, usually a liquid.) Batteries can be found everywhere in the world around us, from the giant batteries that provide electrical energy in spacecraft to the miniature batteries that power radios and penlights.

The correct use of the term battery is reserved for groups of two or more voltaic cells. The lead storage battery found in automobiles, for example, contains six voltaic cells. However, in common usage, a single cell is often referred to as a battery. For example, the common dry cell battery found in flashlights is really a single voltaic cell.

Types of batteries

Batteries can be classified as primary or secondary batteries (or cells). A primary battery is one designed to be used just once. When the battery has run down (produced all the energy it can), it is discarded. Secondary batteries, on the other hand, can be recharged and reused.

Special Kinds of Batteries

The best known example of a primary battery is probably the common dry cell invented by French engineer Georges Leclanché (1839–1882). The dry cell consists of a zinc container that supplies electrons to the battery; a carbon rod through which the electrons flow; and a moist paste of zinc chloride and ammonium chloride, which accepts the electrons produced from the zinc. Technically, the zinc container is the anode (the electrode at which electrons are given up to a reaction) and the moist paste is the cathode (the electrode at which electrons are taken up from a reaction) in the cell. The Leclanché cell is called a dry cell because no liquid is present in it. However, it is not really dry because of the presence of the moist paste, which is needed if electrons are to flow through the cell.

The dry cell runs down as the zinc can is slowly used up. At some point there is not enough zinc left to produce electrons at a useable rate. At that point, the dry cell is just thrown away.

Secondary cells. The secondary cell with which you are likely to be familiar is the lead storage battery found in automobiles. The lead storage battery usually consists of six voltaic cells connected to each other. The total amount of energy produced by the battery is equal to the sum of the electrical energy from the six cells. Since each cell produces about two volts, the total energy available from the cell is 12 volts.

As the lead storage battery is used, it runs down. That is, the lead plates in the battery are converted to lead sulfate. Unlike the dry cell, however, this process can be reversed. Electrical current can be passed back into the battery, and lead sulfate is changed back into lead. If you could see the lead plates in a battery, you would see them slowly disappearing when the battery is being used and slowly reappearing when the battery is being recharged. Recharging occurs naturally when the automobile is operating and generating its own electricity or when a source of external current is provided in order to recharge the battery.

[See also Cell, electrochemical; Electrical conductivity; Electric current; Electricity ]