The electrolyte in each storage tank is circulated through the appropriate loop. During discharge product of reaction, the soluble zinc bromide is stored, along with the rest of the electrolyte, in the two loops and external tanks. During charge, bromine is liberated on the positive electrode and zinc is deposited on the negative electrode. Bromine is then complexed with an organic agent to form a dense, oily liquid polybromide complex.
It is produced as droplets and these are separated from the aqueous electrolyte on the bottom of the tank in positive electrode loop. During discharge, bromine in positive electrode loop is again returned to the cell electrolyte in the form of a dispersion of the polybromide oil. A vanadium redox battery is another type of a flow battery in which electrolytes in two loops are separated by a proton exchange membrane PEM.
Chemical reactions proceed on the carbon electrodes. Under actual cell conditions, an open circuit voltage of 1. The extremely large capacities possible from vanadium redox batteries make them well suited to use in large RAPS applications, where they could to average out the production of highly unstable power sources such as wind or solar power. The extremely rapid response times make them suitable for UPS type applications, where they can be used to replace lead acid batteries.
Sodium, just like lithium, has many advantages as a negative-electrode material. Sodium has a high reduction potential of Sodium salts are highly found in nature, they are cheap and non-toxic. Sulphur is the positive electrode material which can be used in combination with sodium to form a cell. Sulphur is also highly available in nature and very cheap. The problem of a sodium-sulphur cell is to find a suitable electrolyte.
Aqueous electrolytes cannot be used and, unlike the lithium, no suitable polymer was found. In each cell, the negative electrode molten sodium was contained in a vertical tube diameter from 1 to 2 cm. The positive electrode molten sulphur is absorbed into the pores of carbon felt serves as the current-collector and inserted into the annulus between the ceramic beta-alumina electrolyte tube and the cylindrical steel case Fig. Between molten sodium and beta-alumina electrolyte also could be found a safety liner with a pin-hole in its base. Sodium ions pass from the sodium negative electrode, through the beta-alumina electrolyte, to the sulphur positive electrode.
There they react with the sulphur to form sodium polysulphides. Standard voltage of the cell is about 2 V. Uncontrolled chemical reaction of molten sodium and sulphur could cause a fire and corrosion inside the cell and consequently destruction of the cell. It often happens after the fracture of the electrolyte tube. This problem is solved by inserting of safety liner to the beta-alumina tube.
This allows a normal flow of sodium to the inner wall of the beta-alumina electrolyte, but prevents the flow in the case of tube fracture. In the sodium-metalchloride battery the sulphur positive electrode there is replaced by nickel chloride or by a mixture of nickel chloride NiCl 2 and ferrous chloride FeCl 2 — see Fig.
The negative electrode is from molten sodium, positive electrode from metalchloride and electrolyte from the ceramic beta-alumina the same as in the sodium-sulphur battery. The second electrolyte, to make good ionic contact between the positive electrode and the electrolyte from beta-alumina, is molten sodium chloraluminate NaAlCl 4. The positive electrode is from a mixture of metal powder Ni or Fe and sodium chloride NaCl. During charge, these materials are converted into the corresponding metal chloride and sodium. Advantage of the sodium metalchloride cell over the sodium sulphur cell is that there is possibility of both an overcharge and overdischarge reaction, when the second electrolyte molten sodium chloraluminate reacts with metal overcharge or with sodium overdischarge.
Another advantage of the sodium metalchloride system is safety of operation. When the beta-alumina electrolyte tube cracks in this system, the molten sodium first encounters the NaAlCl 4 electrolyte and reacts with it according the overdischarge reaction.
This chapter is focused on electrochemical storage or batteries that constitute a large group of technologies that are potentially suitable to meet a broad market needs. The five categories of electrochemical systems secondary batteries were selected and discussed in detail: standard batteries lead acid, Ni-Cd modern batteries Ni-MH, Li—ion, Li-pol , special batteries Ag-Zn, Ni-H2 , flow batteries Br2-Zn, vanadium redox and high temperature batteries Na-S, Na—metalchloride.
These batteries appear to be promising to meet the requirements for end-user applications.
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However, the use of secondary batteries involves some technical problems. Since their cells slowly self-discharge, batteries are mostly suitable for electricity storage only for limited periods of time. They also age, which results in a decreasing storage capacity. For electrochemical energy storage, the specific energy and specific power are two important parameters.
Other important parameters are ability to charge and discharge a large number of times, to retain charge as long time as possible and ability to charge and discharge over a wide range of temperatures. This chapter is supported by the EU project CZ. Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution 3.
Help us write another book on this subject and reach those readers. Login to your personal dashboard for more detailed statistics on your publications. Edited by Ahmed F.
We are IntechOpen, the world's leading publisher of Open Access books. Built by scientists, for scientists. Our readership spans scientists, professors, researchers, librarians, and students, as well as business professionals. Downloaded: Introduction Electrochemical energy storage covers all types of secondary batteries.
Common commercially accessible secondary batteries according to used electrochemical system can be divided to the following basic groups: Standard batteries lead acid, Ni-Cd modern batteries Ni-MH, Li—ion, Li-pol , special batteries Ag-Zn, Ni-H2 , flow batteries Br2-Zn, vanadium redox and high temperature batteries Na-S, Na—metalchloride. Standard batteries 2. Lead acid battery Lead acid battery when compared to another electrochemical source has many advantages.
Battery composition and construction Construction of lead acid LA battery depends on usage. Types of LA batteries According to the usage and construction, lead acid batteries split into stationary, traction and automotive batteries. VRLA batteries Originally, the battery worked with its plates immersed in a liquid electrolyte and the hydrogen and the oxygen produced during overcharge were released into the atmosphere.
Failure mechanisms of LA batteries Lead acid batteries can be affected by one or more of the following failure mechanisms: positive plate expansion and positive active mass fractioning, water loss brought about by gassing or by a high temperature, acid stratification, incomplete charging causing active mass sulphation, positive grid corrosion, negative active mass sulphation batteries in partial state of charge PSoC cycling - batteries in hybrid electric vehicles HEV and batteries for remote area power supply RAPS applications. Battery composition and construction The nickel cadmium cell has positive electrode from nickel hydroxide and negative electrode from metallic cadmium, an electrolyte is potassium hydroxide.
Modern batteries 3. Ni-MH battery 3. Battery composition and construction The sealed nickel metal hydride cell has with hydrogen absorbed in a metal alloy as the active negative material. Memory effect Ni-MH batteries also suffer from the memory effect. Li-ion battery Lithium is attractive as a battery negative electrode material because it is light weight, high reduction potential and low resistance.
Battery composition and construction The principle of the lithium-ion cell is illustrated schematically in Fig. Li-pol battery Polymers contained a hetero-atom i. Special batteries 4. Ag-Zn battery 4. Battery composition and construction The zinc-silver oxide battery has one of the highest energy of aqueous cells. Electrolyte is water solution of KOH 1. Ni-H 2 battery 4. Battery composition and construction The Ni-H 2 battery is an alkaline battery developed especially for use in satellites see Fig. Flow batteries Flow batteries store and release electrical energy with help of reversible electrochemical reactions in two liquid electrolytes.
Br 2 -Zn battery 5. Battery composition and construction The zinc-bromine cell is composed from the bipolar electrodes. Vanadium redox battery 5. Battery composition and construction A vanadium redox battery is another type of a flow battery in which electrolytes in two loops are separated by a proton exchange membrane PEM.
High temperature batteries 6. Na-S battery 6. Battery composition and construction Sodium, just like lithium, has many advantages as a negative-electrode material. Na-metalchloride battery 6. Battery composition and construction In the sodium-metalchloride battery the sulphur positive electrode there is replaced by nickel chloride or by a mixture of nickel chloride NiCl 2 and ferrous chloride FeCl 2 — see Fig.
Principle of operation The basic cell reactions during discharge are simple, i. Conclusion This chapter is focused on electrochemical storage or batteries that constitute a large group of technologies that are potentially suitable to meet a broad market needs. More Print chapter. How to cite and reference Link to this chapter Copy to clipboard. Available from:. Over 21, IntechOpen readers like this topic Help us write another book on this subject and reach those readers Suggest a book topic Books open for submissions.
More statistics for editors and authors Login to your personal dashboard for more detailed statistics on your publications. Access personal reporting. Other battery types and future prospects Chapter 4. Lead Batteries: Main Characteristics 4.
Introduction 4. Electrical characteristics 4. Charge of lead batteries 4. Energy management 4. SOC indicator 4. Conditions of use 4. Economic considerations 4. Applicable standards 4. Future developments 4. To find out more 4. Solutions to exercises Chapter 5. Manufacturing Starting, Lighting and Ignition Batteries 5.
Introduction 5. Manufacturing an SLI battery 5. Raw materials 5. Different ways of manufacturing lead SLI batteries 5. Composition of the paste 5. Pasting the grids 5. Curing of the plates 5. Assembly 5. Formation of the battery 5. Final test and dispatch 5. Solutions to exercises PART 3. Nickel—Cadmium Batteries 6. Introduction 6. Operating principle 6. Main characteristics Chapter 7. Nickel—Metal Hydride Batteries 7. Introduction 7. Operating principle 7. Main characteristics 7. A switch opens or closes the circuit. A porous membrane is placed between the two half-cells to complete the circuit.
The various electrochemical processes that occur in a voltaic cell occur simultaneously. It is easiest to describe them in the following steps, using the above zinc-copper cell as an example. Zinc atoms from the zinc electrode are oxidized to zinc ions. This happens because zinc is higher than copper on the activity series and so is more easily oxidized.
The electrode at which oxidation occurs is called the anode. The zinc anode gradually diminishes as the cell operates due to the loss of zinc metal. The zinc ion concentration in the half-cell increases. Because of the production of electrons at the anode, it is labeled as the negative electrode. The electrons that are generated at the zinc anode travel through the external wire and register a reading on the voltmeter.
They continue to the copper electrode. Electrons enter the copper electrode where they combine with the copper II ions in the solution, reducing them to copper metal. The electrode at which reduction occurs is called the cathode. The cathode gradually increases in mass because of the production of copper metal.
The concentration of copper II ions in the half-cell solution decreases. The cathode is the positive electrode. Ions move through the membrane to maintain electrical neutrality in the cell. The two half-reactions can again be summed to provide the overall redox reaction occurring in the voltaic cell. How many volts is that? The first meters were called galvanometers and they used basic laws of electricity to determine voltage. They were heavy and hard to work with, but got the job done.
The first multimeters were developed in the s, but true portability had to wait until printed circuits and transistors replaced the cumbersome wires and vacuum tubes. Electrical potential is a measurement of the ability of a voltaic cell to produce an electric current. Electrical potential is typically measured in volts V.
The voltage that is produced by a given voltaic cell is the electrical potential difference between the two half-cells. It is not possible to measure the electrical potential of an isolated half-cell. For example, if only a zinc half-cell were constructed, no complete redox reaction can occur and so no electrical potential can be measured. It is only when another half-cell is combined with the zinc half-cell that an electrical potential difference, or voltage, can be measured.
The electrical potential of a cell results from a competition for electrons. In a zinc-copper voltaic cell, it is the copper II ions that will be reduced to copper metal. Instead, the zinc metal is oxidized. The reduction potential is a measure of the tendency of a given half-reaction to occur as a reduction in an electrochemical cell. In a given voltaic cell, the half-cell that has the greater reduction potential is the one in which reduction will occur.
In the half-cell with the lower reduction potential, oxidation will occur. What is a standard? We all compare ourselves to someone. Can I run faster than you? Am I taller than my dad? When we use a standard for our comparisons, everybody can tell how one thing compares to another. One meter is the same distance everywhere in the world, so a meter track in one country is exactly the same distance as a meter track in another country.
We now have a universal basis for comparison. The activity series allows us to predict the relative reactivities of different materials when used in oxidation-reduction processes. We also know we can create electric current by a combination of chemical processes. But how do we predict the expected amount of current that will flow through the system? We measure this flow as voltage an electromotive force or potential difference. In order to do this, we need some way of comparing the extent of electron flow in the various chemical systems. The best way to do this is to have a baseline that we use — a standard that everything can be measured against.
For determination of half-reaction current flows and voltages, we use the standard hydrogen electrode. The Figure below illustrates this electrode. A platinum wire conducts the electricity through the circuit. The wire is immersed in a 1. The half-reaction at this electrode is. Under these conditions, the potential for the hydrogen reduction is defined as exactly zero.
We call this , the standard reduction potential. We can then use this system to measure the potentials of other electrodes in the half-cell. A metal and one of its salts sulfate is often used is in the second half-cell. We will use zinc as our example see Figure below. The standard hydrogen half-cell paired with a zinc half-cell. As we observe the reaction, we notice that the mass of solid zinc decreases during the course of the reaction.
Lead-Nickel Electrochemical Batteries by Christian Glaize -
This suggests that the reaction occurring in that half-cell is. So, we have the following process occurring in the cell:. We define the standard emf electromotive force of the cell as:. We can do the same determination with a copper cell Figure below. The standard hydrogen half-cell paired with a copper half-cell. As we run the reaction, we see that the mass of the copper increases, so we write the half-reaction:.
This makes the copper electrode the cathode. We now have the two half-reactions:. Now we want to build a system in which both zinc and copper are involved. We know from the activity series that zinc will be oxidized and cooper reduced, so we can use the values at hand:. Keeping rust away. When exposed to moisture, steel will begin to rust fairly quickly. This creates a significant problem for items like nails that are exposed to the atmosphere.
The nails can be protected by coated them with zinc metal, making a galvanized nail. The zinc is more likely to oxidize than the iron in the steel, so it prevents rust from developing on the nail. In order to function, any electrochemical cell must consist of two half-cells. The Table below can be used to determine the reactions that will occur and the standard cell potential for any combination of two half-cells without actually constructing the cell.
The half-cell with the higher reduction potential according to the table will undergo reduction within the cell. The half-cell with the lower reduction potential will undergo oxidation within the cell.
Lead-Nickel Electrochemical Batteries
If those specifications are followed, the overall cell potential will be a positive value. The cell potential must be positive in order for redox reaction of the cell to be spontaneous. If a negative cell potential were to be calculated, that reaction would be spontaneous in the reverse direction. Write the balanced equation for the overall cell reaction that occurs. Identify the anode and the cathode.
Step 1: List the known values and plan the problem. The silver half-cell will undergo reduction because its standard reduction potential is higher. The tin half-cell will undergo oxidation. The overall cell potential can be calculated by using the equation.
Before adding the two reactions together, the number of electrons lost in the oxidation must equal the number of electrons gained in the reduction. The silver half-cell reaction must be multiplied by two. After doing that and adding to the tin half-cell reaction, the overall equation is obtained.
Step 3: Think about your result. The standard cell potential is positive, so the reaction is spontaneous as written. Tin is oxidized at the anode, while silver ion is reduced at the cathode. Note that the voltage for the silver ion reduction is not doubled even though the reduction half-reaction had to be doubled to balance the overall redox equation.
A substance which is capable of being reduced very easily is a strong oxidizing agent. Conversely, a substance which is capable of being oxidized very easily is a strong reducing agent. According to the standard cell potential table, fluorine F 2 is the strongest oxidizing agent. It will oxidize any substance below on the table.
For example, fluorine will oxidize gold metal according to the following reaction. Lithium metal Li is the strongest reducing agent. It is capable of reducing any substance above on the table. For example, lithium will reduce water according to this reaction.