The Chemistry Behind Lithium-Based Rechargeable Batteries
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Introduction
From mobile phones to cars, the exponential growth of technological advances during the last few decades have increased the demand for energy. This has brought concerns over the damages caused by the resources used to power these advances for the environment, thus, creating the increasing urge to find renewable alternatives. As a result, electrical gadgets have been popularized and batteries are used as main source of stored energy. Batteries are chemical devices that store energy made of two electrochemically active couples, the electrodes being separated by an ion conductive and an electronically insulating medium also known as an electrolyte (Rosa 2009). However, due to the heavy metals and toxic materials that goes into producing and disposing batteries, more people are relying on the use of rechargeable batteries. This paper aims explore the structure, properties of the materials used as well as the advantages and disadvantages of using rechargeable batteries focusing on Lithium-ion batteries and Nickel-metal hydride batteries.
Battery Anatomy
To understand the importance of the materials used for the creation of batteries, one must first understand its anatomy. The internal workings of a battery are maintained within a plastic or metal case. Inside them, a cathode connects to the positive terminal whereas, an anode connects to the negative terminal. As a whole, these components are known as electrodes, which is where the chemical reactions occur. To prevent the electrodes from touching but allowing them to flow freely within them, a separator is added to the middle. The medium that allows electric charge to flow between the electrodes is known as an electrolyte. Lastly, the collector conducts charge to the outside of the battery through the load (Brain, Bryant, Pumphrey 2000).
In a battery, electrodes force electrons to transfer to one another through an electrolyte. The anode produced an oxidation reaction while the cathode produces a reduction reaction (see Fig. 1). When one of the redox reactions is finished, the electron flow stops. If the process can be reversed by applying an external current, batteries can be recharged. The key to building a successful battery is to choose the most suitable compounds at each electrode (Rosa 2009).
Fig. 1 Schematic diagrams of (a) a redox reaction, (b) a primary (non-rechargeable) battery upon discharging and (c) a secondary (rechargeable) battery upon charging (Rosa 2009).
The Chemistry behind Lithium-based Rechargeable Batteries
In the present, the most commonly seen material in the battery industry is Lithium (Li) due to its high cell potential and low atomic weight which results in high specific energy and energy density of the cells (Blomgren 2017).