Vinit Singh is a computer science student pursuing his B.Tech degree in Bharath Institute of Higher Education and Research, Chennai, India.
A battery is a source of power that converts chemical energy into electrical energy. The negative and positive electrode, separator and electrode are the four main components in an electrochemical battery. The flow of ions from one electrode to another electrode generates power. There are different kinds of batteries. Flashlights, mobile phones, laptops and electric vehicles are devices that use batteries.
There are commonly two types of cell phone batteries used these days in terms of chemical composition.
A Lithium-ion battery is also known as a Li-ion battery. Akira Yoshina in 1985 developed the Li-ion battery which was based on earlier research by John Goodenough and Stanley Whittingham. These batteries are considered a pioneering technology that has been successfully adopted as a power source for a wide range of electronics and is also used in electronic vehicles. It is a type of rechargeable battery in which the lithium ions moves from the positive electrode to the negative electrode through an electrolyte and while charging and moves from the negative electrode to the positive electrode while discharging. The most common electrolyte used is lithium hexafluorophosphate. In this kind of battery, graphite is used as a negative electrode, lithium compound as the positive electrode and polyethylene or polypropylene as the separators.
Li-ion batteries have high electrochemical potential with the highest energy density, low self-discharge and no memory effect. These batteries can be manufactured to either prioritize energy or power density. There are many different types of Lithium-ion batteries that differs in Chemistry, performance, cost and safety characteristics. These kinds of li-ion batteries are low maintenance and can stay at a lower capacity. Unlike Nickel-cadmium (Ni-Cd) batteries, these do not contain toxic cadmium that means they can be easily be disposed of when compared to Ni-cd batteries.
The problem with Li-ion batteries is if they are damaged or incorrectly charged can lead to explosions and fires because they contain flammable electrolytes. Transportation is a huge problem. Many airline services have limited the number of Li-ion batteries they take. A li-ion battery should be protected against short circuits using protective covers and should also be carried separately. The cost of manufacturing a li-ion battery is expensive when compared to nickel-cadmium cells which is a major disadvantage. It is said that they are 40% more costly than a typical Ni-Cd battery. Li-ion battery has still been in the developing stage even though it has been available for many years. The lithium-ion battery can withstand up to 1200 charge-discharge cycles and then the battery needs to be replaced. Non-removable batteries in smartphones can be a big issue after its potential is reached.
Lithium polymer(Li-Po) batteries are also known as Lithium-ion polymer batteries. These batteries have been evolved from lithium-ion and lithium metal batteries. Lithium polymer batteries share the history of lithium-ion batteries which underwent extensive researches during the 1980s. The working of a lithium polymer battery is almost similar to the lithium-ion battery. There are four main components in a typical cell: negative electrode, positive electrode, separator and electrolyte. In this kind of battery, the lithium ions move from the negative electrode to the positive electrode through an electrolyte while discharging the battery and vice versa while charging. The electrodes are the same as the lithium-ion battery. The electrolyte in this battery is a solid polymer such as poly(acrylonitrile) or poly(methyl methacrylate) instead of a liquid electrolyte in a lithium-ion battery and the separator used in this also may be a polymer which is the main difference between them. The microporous separator is used in between to prevent the electrodes from touching each other by allowing only the ions and not the electrode particles to move from one side to another.
Lithium polymer batteries are generally more expensive than lithium-ion batteries. These batteries are used in mobile phones, radio-controlled aircraft and electric vehicles. Li-Po takes a shorter time to charge but it can be used for 500 charge cycles which is less than the li-ion batteries. Li-Po can handle a wide temperature range. These batteries are safer lighter in weight when compared to Li-ion batteries.
There are commonly three types of laptop batteries used these days in terms of chemical composition.
Nickel Cadmium batteries were invented back in 1899 by Waldemar Jungner of Sweden and are one of the oldest batteries made. Ni-cd batteries are generally made in a wide range of capacities and sizes. These batteries have nickel oxide hydroxide and metallic cadmium as electrodes. These batteries are manufactured differently thus they can be charged depending on it. The charge rate is measured based on the percentage of the amp-hour capacity. These batteries should be supplied with more energy than their actual capacities regardless of the charge speed. 1.3 V is the maximum electromotive force offered by these batteries. Ni-cd cells were used in portable power tools, photography equipment, flashlights and also in other portable electronic devices.
Nickel-Cadmium batteries are very toxic to the human body. These cells even have physiological effects on the system. Ni-cd has been banned from sale in many countries in Europe. It has a high discharge rate which is said not considered good in terms of productivity.
Nickel Meta hydride(Ni-MH)
Nickel meta-hydride batteries are a replacement for cadmium for Ni-Cd batteries. Development on Ni-Mh batteries began in the geneva research centre. Ni-Cd and Nickel meta-hydride batteries both use nickel oxide hydroxide as the positive electrode and hence the reaction at positive electrode is also the same. But in Ni-Mh, the electrode uses a hydrogen-absorbing alloy instead of cadmium. Ni-Mh needs less maintenance and conditioning because it is less affected by the memory effect when compared to Ni-cd batteries.
Ni-Mh batteries have a 35 per cent higher capacity than a standard Ni-Cd. These batteries also have higher density and the periodic exercise cycles are required less often. Ni-Mh batteries are also environment-friendly because it contains less toxic metals. These batteries have problems at very high or very low temperatures.
They have high self-discharge than Ni-Cd batteries. There is also a low self-discharge nickel-metal hydride battery (LSD NiMH) that has a significantly lower rate of self-discharge. This development was introduced by Sanyo, Eneloop in 2005. These batteries use an improved electrode separator and positive electrode by which the cells retain 75 to 85 % of their capacity.
Li-ion batteries are also used in mobiles as well as in laptops. These batteries are light in weight and perform better than other types of laptop batteries. Li-ion battery doesn't have memory effect, This effect causes them to lose their capacity for a full recharge if they are discharged again and again. Lithium-ion gets charged quickly which is the main advantage. Laptop lithium-ion batteries have a low self-discharge rate of nearly 2 per cent per month. This batteries requires special handling because they can explode easily due to their chemical composition.