The accumulators, our laptops, smartphones, tables and even other mobile devices are those elements that store electrical energy so that the tools work without being constantly plugged in. There are different types provided by most battery supplier companies, such as batteries (usually composed of one cell), capacitors or supercapacitors and grouped cells.
The batteries can have various technologies in their electrochemical cells and can be: NiCd, NiMH, Zinc-Air, Li-Ion, etc. According to their technology we can find primary cells and secondary cells. The primary ones are those that transform chemical energy into electricity in an “irreversible” way. Instead, the secondary ones can be recharged again and are suitable for our batteries.
The cells provide electrical energy thanks to a process known as redox (reduction-oxidation) in which one of the materials that make up the cell oxidizes (loses) and the other reduces (gains electrons). The materials may return to their initial state under certain circumstances that occur during battery charging.
Each cell consists of two electrodes of the same or different material and an electrolyte in which they are submerged. Many materials have since been used: acid-lead, dry-cell (with zinc and carbon electrodes, and plaster or cardboard as an electrolyte), mercury and other heavy metals that are highly toxic and polluting, NiCd (Nickel-Cadmium for electrodes and potassium hydroxide for electrolyte), Fe-Ni (with potassium hydroxide electrolyte), alkaline (with manganese dioxide cathode and zinc anode, with alkaline electrolyte), NiMH (nickel metal hydride), lithium (battery) lithium with cathode with substances such as: iron sulfide, manganese dioxide, sulfur dioxide, thionyl chloride, carbon monofluoride, …) and finally those of lithium ions (with its variant of Ion-Li and Polymer).
In this article, we’re going to talk about Lithium ions.
Currently the most used in all devices are lithium-ion because of its advantages. The 3.7V Lithium Battery is one of the most popular versions of lithium-ion batteries. They appear for the first time in the 80s, when John B. Goodenough and his research team (Sony) managed to create them. In 1996 a variant was created, that of polymer, which replaced the previous electrolyte with a solid composite polymer and laminated electrodes and separator (these cells are flexible). Whose properties are:
– Ion-Li: with graphite anode and cathode of cobalt oxide, trifiline (LiFePO4) or manganese oxide. In the liquid electrolyte there are lithic ions that will be responsible for providing energy. As soon as it suffers memory effect, they achieve high energy densities (115Wh / kg), they can be charged without being completely unloaded and without reducing their useful life. The temperature is a weak point, since at high temperatures they begin to lose efficiency. Nor do they tolerate complete discharges well and suffer damage.
– LiPo: those of polymer are similar to the previous ones, but with better energy density and a higher discharge rate. But the ravages when discharged completely are high, and can be almost unused.
The rechargeable lithium-ion batteries, in terms of their operation, are based on processes called insertion – disintegration of lithium ions (Li +), the reaction that occurs can be described as follows:
The previous reaction occurs in a solid state, between two insertion compounds as electrodes, one of the compounds is called a host, of an ionic nature, reacts by occupying vacant places in the structure of another species, also called host. These reactions can occur reversibly. During the discharge process, the e- move in the opposite direction to that of the electric current, in the positive electrode the reduction occurs, while in the negative the oxidation of the metallic lithium occurs. The lithium ion, such as in 22.2V Lithium Battery, moves through the electrolyte towards the positive electrode where the reduction of the host species and the insertion of the host species occurs.
In contrast, during the charging process, the opposite reaction occurs. Unfortunately during this process the Lithium ions are deposited in the negative electrode growing and expanding more and more in the different charge-discharge processes, which will cause at some point the two electrodes will collide forming a short circuit or the battery explosion. These Redox reactions are limited since the large number of discharges and charges generates an evident wear of the battery until it deteriorates completely.