Battery Failure Electro Chemistry Essay, Research Paper

PROBLEM: BATTERIES TEND TO FAIL AT EXTREME TEMPERATURES.

TESTABLE QUESTION: HOW AND WHY DO DIFFERENT BATTERY TYPES FAIL AT EXTREME TEMPERATURES?

ELECTRO CHEMISTY

BATTERY FAILURE

HONORS CHEMISTY RESEARCH PROJECT

HISTORY OF THE BATTERY

The battery s origins may be followed back to very ancient times. We know that many of the wise men could have been exploring and testing electricity. For example, a clay vase, thought to be several thousand years old, was discovered in 1932 near Baghdad. It contained an iron rod inserted into a thin copper cylinder, which may have served to hold static electricity. Although we may never know the truth, it still makes one wonder if the ancients actually did try to harness static electricity.

Whether their predecessors who assembled the clay vase knew anything about static electricity or not, we know for certain that the ancient Greeks did. They knew if a piece of amber was rubbed, it would attract light weight objects. And Aristotle knew about the lodestone, a strongly magnetic ore that attracts iron and metals. Theses two facts prove that the Greek s had the thought process to extrapolate theories and ideas from simple experiments, thus leading many to believe that they had a basic understanding of basic natural forces.

The next big step in the harnessing of electricity came when Benjamin Franklin began to suspect that lightning was an electrical current in nature. To test his suspicions, Franklin devised his famous experiment in which he fastened a key to a kite to see if the lightning would pass through the metal. As we all know Franklin’s experiment worked thus proving that lightning is a stream of electrified air. Franklin went on to coin many of today’s standard electrical terms, including “battery,” “charge,” and “conductor.”

Amber rubbing and lodestone studying aside, the actual development of batteries for everyday use has been a project since only the early 1800 s. Alessandro Volta, a professor of natural philosophy at the University of Pavia [located in Italy], constructed the first apparatus known to produce continuous electricity. To do so he stacked pairs of coin-sized discs, one silver, the other zinc, and separated the pairs by a wafer of pasteboard, leather, or some other spongy material. The wafers had been soaked in salt water and sometimes, alkaline solutions. Several piles were assembled side by side and were connected by metal strips. At each end of the system, a metal strip was bent down to dip into a small cup of mercury, an excellent electrical contact.

A few years later, in 1813, Sir Humphrey Davy came up with a giant battery in the basement of Britain’s Royal Society. It was made up of 2,000 pairs of plates and took up 889 square feet. Davy used this battery for experimental usages. Through electrolysis, he broke apart natural sodium and potassium compounds to isolate pure sodium and potassium metal. It was a risky undertaking because both explode on contact with water and must be kept immersed in kerosene or some other hydrocarbon liquid. Davy’s work, however, went beyond mere tinkering in the basement with dangerous chemicals; the experiments he conducted were crucial. They paved the way to a deeper understanding about the electric nature of things that is; how elementary substances combine through electrical attraction to form common natural compounds.

Close behind Sir Humphrey Davy’s battery experiments, Michael Faraday was using voltaic piles to conduct important research on electricity and magnetism. He found that by pumping an electric current through a wire, a magnetic field was induced in a parallel wire. Faraday pressed on and in 1831, he showed that a moving magnet could generate electricity in a nearby wire.

Other scientists meanwhile were improving Volta’s piles. They realized that each zinc-paper-silver sandwich was actually a separate source of low-voltage electricity. That insight led to the development of individual cells containing an anode of one metal and a cathode of another immersed in an electrolyte, much like present day batteries.

Finally in the 1860’s, George Leclanche of France developed what would be the precursor of the world’s first widely used battery: the zinc carbon cell. The anode was a zinc and mercury alloyed rod. Zinc, which was the anode in Volta’s original cell, proved to be one of the best metals for this job. The cathode was a porous cup of crushed manganese dioxide and some carbon. Into the mix a carbon rod was inserted to act as the current collector. Both the anode and the cathode cup were plunged into a liquid solution of ammonium chloride, which acted as the electrolyte. The system was called a “wet cell.”

Though Leclanche’s cell was rugged and inexpensive, it was eventually replaced by the improved “dry cell” in the 1880’s. The anode became the zinc can containing the cell, and the electrolyte became a paste rather than a liquid: basically the zinc carbon cell that is known today.

NEEDED TERMINOLOGY

The battery being the basis of this research investigation needs to be defined and explained. A battery, also referred to as an electric cell, is a device that converts chemical energy into electricity. Batteries consist of two or more cells connected in series or parallel, mean they are either connected head to tail or head-to-head and tail-to-tail. All cells consist of a liquid, paste, or solid electrolyte and a positive electrode, and a negative electrode. The electrolyte is an ionic conductor; one of the electrodes will react, producing electrons, while the other will accept electrons. When the electrodes are connected to a device to be powered, called a load, an electrical current flows.

Batteries in which the chemicals cannot be brought back into their original form once the energy has been converted, are called primary cells or voltaic cells. Basically if a battery can not be recharged after being used it is called a primary cell. On the other hand batteries in which the chemicals can be reconstituted by passing an electric current through them in the direction opposite that of normal cell operation are called secondary cells, rechargeable cells, or storage cells.

ELECTRO CHEMISTRY BASICS

Electrochemistry is the foundation on which batteries are built upon, and is therefore necessary to understand. Electrochemistry is the part of the science of chemistry that deals with the interrelationship of electrical currents, voltages, chemical reactions, and with the mutual conversion of chemical and electrical energy. In general, electrochemistry is the study of chemical reactions that produce electrical effects and of the chemical phenomena that are caused by currents or voltages. To understand why a battery fails after certain temperatures it is necessary to understand why batteries work in the first place.

Using general knowledge it can be described that a battery works through a series of redox reactions. Such reactions consist of two parts; an oxidation reaction, in which an electron is lost, and a reduction reaction, in which an electron is gained. When a redox reaction occurs inside a battery the oxidation reaction always occurs at the anode and the reduction reaction occurs at the cathode. We then use this knowledge in addition to a chart of electromotive forces to deduce the electric potential or number of volts that a battery can produce. The electrode potential is found with the simple equation EMF cell = EMF oxidation + EMFreduction where EMF stands for the electromotive forces (See Appendix). This equation, however, does not apply to this problem as much as the following equation, known as Nernst s Law. The law states that ef is equal to (R x T x E) over (N x F), where ef equals the electromotive force, R is the gas constant, T is the temperature in Kelvin, E is the number of electrons produced, N is Avagadros number, and F is Faradays constant (See Appendix). This equation will allow me to test the electromotive forces that are produced at lower temperatures.

THE PROBLEM

It is a commonly known problem that batteries tend to fail when exposed to extreme temperatures. The problem first arose when man started exploring the outer limits of the earth s atmosphere. Batteries not able to withstand extreme temperature cannot be changed so as to be able to withstand them; however, certain batteries have been made specifically to withstand those temperatures and are currently in use by NASA, other Government, and some commercial applications. Once an object leaves the earth s ground, geothermal heat no longer has a significant impact on its temperature, and therefore must either rely on its own heat or direct sunlight. Space is a great example of this problem and, objects traveling nearer to the sun, or in the suns rays receive high amounts of heat, while objects that are not in the suns rays are extremely cold. The National Aeronautics & Space Administration or NASA was one of the first to tackle this problem.

FACTORS THAT CAUSE THE PROBLEM

There is but one factor that causes the problem stated. That factor is temperature, and it can be regulated only in the lab, and not anywhere outside of it. The final problem that needs to be solved is not how do we regulate the temperature, but how do we prevent the temperature from affecting the chemicals inside the battery, more specifically the electrolyte.

FACTORS THAT RELATE TO THE PROBLEM

The factors that relate to the problems include; the battery s composition and starting voltage, type of battery, length of exposure time to high/low temperature, and drain place upon the battery. First off battery composition varies between types of batteries, for example depending on the electrodes that a battery has, a certain electrolyte is chosen to be put in the battery, thus different chemical reactions take place and also the reaction that the electrolyte has with temperature may vary. Starting voltage may play a role in how long it takes for the battery to become affected by the temperature. The length of the exposure time may also play a role in the battery s operation, if the exposure time is not long enough there may be not reaction on the battery. Finally, if the battery has a high/low drain place upon itself it may cause the results to be skewed.

SOLUTIONS/POSSIBLE EXPIRIMENTS

Although there is no remedy for batteries, which have already been made, it is possible to make batteries that can withstand extreme temperatures. Possible experiment to see which battery performs the best/worst under extreme conditions could be:

1. Measure at different temperature the voltage output of a battery.

2. Use batteries in different temperatures outside.

Of course when looking at the two experiments the second is more likely to be that of a younger child, but essentially that is what we want to do: test the battery as if it were in those everyday conditions. A more scientific approach is to have a controlled experiment in which, we control our variable(s).

HYPOTHESIS

From research that I have been conducting I have pieced together this hypothesis: Once the battery s temperature rises the EMF will increase, the when temperature continues to rise the EMF will fall, when the temperature decreases the battery s EMF will decrease rapidly.