Battery Technology

In the modern era, electrical energy is normally converted from mechanical energy, solar energy, and chemical energy etc. A battery is a device that converts chemical energy to electrical energy. The first battery was developed by Alessandro Volta in the year of 1800. In the year 1836, John Frederic Daniell, a British chemist developed the Daniell cell as an improved version of the voltaic cell. From that time until today, the battery has been the most popular source of electricity in many daily life applications.In our daily life, we generally use two types of battery, one of them is which can be used once before it gets totally discharged. Another type of battery is rechargeable which means it can be used multiple times by recharging it externally. The former is called primary battery and the later is called secondary battery.  
Batteries can be found in different sizes. A battery may be as small as a shirt button or may be so big in size that a whole room will be required to install a battery bank. With this variation of sizes, the battery is used anywhere from small wrist watches to a large ship.

We often see this symbol in many diagrams of electrical and electronics network. This is the most popularly used symbol for battery. The bigger lines represent positive terminal of the cells and smaller lines represent negative terminal of the cells connected in the battery.

We are often confused about the terms battery cell and battery . We generally refer a battery as a single electro-chemical cell. But literally, battery does not mean that. Battery means a number of electro-chemical cells connected together to meet a certain voltage and  current level. Although there may be a single cell battery, literally,  battery and cell are different.

History of Battery

In the year of 1936 during the middle of summer, an ancient tomb was discovered during construction of a new railway line near Bagdad city in Iraq. The relics found in that tomb were about 2000 years old. Among these relics, there were some clay jars or vessels which were sealed at the top with pitch. An iron rod, surrounded by a cylindrical tube made of wrapped copper sheet was projected out from this sealed top. 
When these pots were filled with an acidic liquid, they produced a potential difference of around 2 volts between the iron and copper. These clay jars are suspected to be 2000 year old battery cells.

In 1786, Luigi Galvani, an Italian anatomist and physiologist was surprised to see that when he touched a dead frog’s leg with two different metals, the muscles of the legs contracted. He could not understand the actual reason why, otherwise he would have been known as the first inventor of the battery cell. He thought the reaction might be due to a property of the tissues.
After that, Alessandro Volta realized that same phenomenon could be created by using cardboard soaked in salt water instead of frog's leg. He sandwiched a copper disc and a zinc disc with a piece of cardboard soaked in salt water in between them and found a potential difference between the copper and zinc. After that in 1800, he developed the first Voltaic Pile (battery) constructed of alternating copper and zinc discs with pieces of cardboard soaked in brine between them. This system could produce measurable current. Alessandro Volta's voltaic pile was considered the first "wet battery cell". Thus, the history of battery began.

The main problem with the Voltaic pile was that, it could not deliver current for a long time. This problem was solved by a British inventor John F. Daniell in 1836. He invented a more developed version of the battery cell which is known as the Daniell cell. Here in this cell, one zinc rod is immersed in zinc sulfate in one container and one copper rod is immersed in copper (II) sulfate in another container. The solutions of these two containers are bridged by a U shaped salt bridge. A Daniell cell could produce 1.1 volt and this type of battery lasted much longer than the Voltaic pile.  
In 1839, the fuel cell was designed by Sir William Robert Grove, a discoverer and man of science. He mixed hydrogen and oxygen within an electrolyte solution, and created electricity and water. The fuel cell did not deliver enough electricity, but it is helpful.
Bunsen (1842) and Grove (1839) created enhancements to battery that used liquid electrodes to supply electricity.  

In the year of 1859, Gaston Plante; first developed the lead acid  battery cell. This was the first form of rechargeable secondary battery. The  lead acid  battery   is still in use for many industrial purposes. It is still the most popular to be used as car battery. 
In 1866, the battery was again developed by a French engineer, Georges Leclanche. It was a carbon-zinc wet cell battery known as the Leclanche cell. Crushed manganese dioxide mixed with a bit of carbon forms the positive electrode and a zinc rod is used as the negative electrode. Ammonium chloride solution is used as a liquid electrolyte. After some years, Georges Leclanche himself improved his own design by replacing liquid ammonium chloride solution with ammonium chloride. This was the invention of the first dry cell.
In 1901, Thomas Alva Edison discovered the alkaline accumulator. Thomas Edison's basic cell had iron as the anode material (-) and nickel oxide as the cathode material(+). This is just one portion of an endless history of  battery .

Step by Step Development in History of Batteries

Developer/Inventor	Country	Year	Invention
Luigi Galvani	Italy	1786	Animal Electricity
Alessandro Volta	Italy	1800	Voltaic Pile
John F. Daniell	Britain	1836	Daniell Cell
Sir William Robert Grove	Britain	1839	Fuel Cell
Robert Bunsen	German	1842	used liquid electrodes to supply electricity
Gaston Plante	France	1859	Lead Acid Battery
Georges Leclanche	France	1866	Leclanche Cell
Thomas Alva Edison	United States	1901	Alkaline Accumulator

Working Principle of Battery

To understand the basic principle of battery properly, first, we should have some basic concept of electrolytes and electrons affinity. Actually, when two dissimilar metals or metallic compounds are immersed in an electrolyte, there will be a potential difference produced between these metals or metallic compounds. 
It is found that, when some specific compounds are added to water, they get dissolved and produce negative and positive ions. This type of compound is called an electrolyte. The popular examples of electrolytes are almost all kinds of salts, acids, and bases etc.
The energy released during accepting an electron by a neutral atom is known as electron affinity. As the atomic structure for different materials are different, the electron affinity of different materials will differ. If two different kinds of metals or metallic compounds are immersed in the same electrolyte solution, one of them will gain electrons and the other will release electrons. Which metal (or metallic compound) will gain electrons and which will lose them depends upon the electron affinities of these metals or metallic compounds. The metal with low electron affinity will gain electrons from the negative ions of the electrolyte solution. On the other hand, the metal with high electron affinity will release electrons and these electrons come out into the electrolyte solution and are added to the positive ions of the solution. In this way, one of these metals or compounds gains electrons and another one loses electrons. As a result, there will be a difference in electron concentration between these two metals. This difference of electron concentration causes an electrical potential difference to develop between the metals. This electrical potential difference or emf can be utilized as a source of voltage in any electronics or electrical circuit. This is a general and basic principle of  battery .

All batteries cells are based only on this basic principle. Let’s discuss one by one. As we said earlier, Alessandro Volta developed the first battery cell, and this cell is popularly known as the simple voltaic cell. This type of simple cell can be created very easily. Take one container and fill it with diluted sulfuric acid as the electrolyte. Now immerse zinc and one copper rod in the solution and connect them externally by an electric load. Now your simple voltaic cell is completed. Current will start flowing through the external load. 
Zinc in diluted sulfuric acid gives up electrons as below:

These Zn ^{+ +} ions pass into the electrolyte, and their concentration is very high near the zinc electrode. As a result of the above oxidation reaction, the zinc electrode is left negatively charged and hence acts as cathode. The diluted sulfuric acid and water disassociate into hydronium ions as given below:

Due to the high concentration of Zn ^{+ +} ions near the cathode, the H₃O⁺ ions are repelled towards the copper electrode and get discharged by removing electrons from the copper atoms. The following reaction takes place at the anode:

As a result of the reduction reaction taking place at copper electrode, copper is left positively charged and hence it acts as the anode.
Daniell Battery Cell: The Daniell cell consists of a copper vessel containing copper sulfate solution. The copper vessel itself acts as the positive electrode. A porous pot containing diluted sulfuric acid is placed in the copper vessel. An amalgamated zinc rod dipping inside the sulfuric acid acts as the negative electrode.
When the circuit is completed, diluted sulfuric acid in the porous pot reacts with zinc so as to liberate hydrogen gas. The reaction takes place as below:

The formation of ZnSO₄ in the porous pot does not affect the working of the cell, until crystals of ZnSO₄ are deposited.
The hydrogen gas passes through the porous pot and reacts with the CuSO₄ solution as below:

Copper so formed gets deposited on the copper vessel.