Lithium Rechargeable Batteries

In this term paper, a discussion on how lithium batteries work will be tabled and the conclusion will be made on how they work. However, not only the functions of the lithium batteries will be discussed but also what components and materials are used to make them work as required.

Introduction

Before talking about what a lithium battery is and how it works, we will first have to know what a battery is for us to be able to understand it better. In a brief way, the battery can be said to be an electric device which has electrochemical cells that are used to transform stored chemical energy into electrical energy. The cells contain both positive and negative terminals which allow the movement of ions and therefore enhancing the flow of current in the cell. There are two types of cells, which can be categorized as primary and secondary. These batteries have different features, but their functions are the same. For a primary cell a user has to use them only once then dispose them after they are exhausted, one of the best examples of this batteries are the alkaline batteries used in watches and torches. While, on the other hand, secondary batteries do not have to be disposed after use since they can be recharged more than one time when they exhaust power. A good example of this kind of cell is the acid battery which is used in vehicles and also most of the lithium batteries we find on portable electronic devices.

When many people hear the word batteries they only imagine of a small object used to power small devices not knowing that batteries can be of different sizes depending on what they are supposed to power. This can be elaborated further by different batteries such as the mini batteries we see in wristwatches; these are familiar to many people and can be said to be the smallest types of cells while on the other hand we have power banks which are rechargeable batteries used in large institution for power backup in case of a power shortage and this can be as large as a room to be specific. When comparing batteries to other forms of power we can say that, batteries tend to have a lower energy specification since they have to do all conversions and deliver their energy in the form of electricity.

When we talk about lithium batteries, it refers to disposable batteries that can also be said to be primary batteries that have lithium metal as an anode. When looking at the specifics of lithium batteries we can say that the cells are meant to produce low power voltages of about 1.5V to 3.7V and this all depends on the designs and also the types of compounds used to manufacture the lithium battery. However, lithium batteries can be said to be different from another kind of cells due to their capability to stay with power for long periods of time. When comparing lithium batteries to lithium-ion batteries which are rechargeable, we can say that for lithium-ion batteries the ions are designed to move from the cathode to anode by the use of reversible insertion of ions into a compound unlike in lithium batteries which use metallic lithium.

Theory

Lithium batteries can be said to have been invented by M. Whittingham back in 1970. However according to Whittingham he used titanium sulfide mixed with lithium as the electric conductors. However, batteries that used lithium as a reactor were supposed to be dangerous. This because  metallic lithium is a very high reactor and  safety measures had to be taken while working with metallic lithium, and by this, the team that was under research proposed that they be using lithium instead of metallic lithium. There are three major components that are functional in a Li-ion battery these are the cathode, the anode and the electrolytes. The anode side of a lithium-ion battery consists of carbon. On the other side, the cathode is a metal oxide while the electrolyte is composed of lithium salt in an organic solution that can dissolve. Electrodes come in many forms depending on if they are negative or positive, one of the mostly used negative electrode is graphite, while on the positive side electrodes can be in three different materials i.e.: spinel, polyanion and last is layered oxide. Electrolytes are a mixture of several materials such as organic carbonates or ethylene carbonate. Since electrolytes do not contain water elements they are forced to use anion salts such as hexafluorophosphate, lithium and many others since it all depends on the materials you like. From the look of things we can say lithium batteries are more expensive but on the brighter side they can be functional over wide temperature ranges and also have high energy density, however, they should always have a protective circuit which hinders the battery from exploding or discharging high energy since it limits its voltage maximum power.

For portable electronic devices such as a laptop or iPad, they are fitted in with lithium-ion battery which comes with temperature sensors which are used to regulate the amount of energy to be taken in by the machine and also stop it from overheating when charging.

Lithium-ion batteries which can also be referred to as Li-ion batteries can be categorized in the rechargeable family, whereby lithium ions in the battery have to move negative to positive electrodes when the battery is discharging stored energy and vice versa when charging the battery. Unlike lithium batteries that use metallic lithium, Li-ion are designed to use intercalated form of lithium. The consistency of lithium-ion batteries plays a big role in the movement of ions through the help of electrolytes. This kind of batteries are mostly found on portable electronics and can be said to be the most common type of rechargeable batteries for most kinds of electronics, they can be said to have a low energy loss system when not being used and they also have a high energy storage capacity as compared to their small sizes and also they have no short term energy loss and this means even if you switch the electronic device off by the time you turn it on the amount of energy stored will still be the same. However, lithium-ion batteries are slowly taking over the market and expanding their use and capabilities. They are also being used in military for powering some of their electronic machineries and cars and also on some aerospace equipment. As technology advances, most companies are also looking forward to replacing the use of lead acid batteries with lithium-ion ones when manufacturing vehicles and all other machines that use lead-acid batteries as a source of power, the point in this is just coming up with a lithium-ion which is smaller in size and can be able to sustain the same amount of energy as the lead acid batteries.

For lithium-ion batteries to charge or discharge energy, there are several stages that they have to go through first. When the lithium-ion battery charges there must be a presence of an external electrical power source or basically a charger which should supply the battery with enough amount of voltage which should be higher than the amount of voltage produced by the battery and there causing the energy being produced by the battery flow backwards as opposed by the charger. Through charging the lithium-ion battery, the ions in the battery are forced to flow from the cathode to anode and eventually become firmly fixed to the porous electrode object. On the other hand, during discharge of energy in a lithium-ion battery, the flow of current is triggered by lithium-ions, which direct the current from anode to cathode through a solution which its water of crystallization has been removed.

When charging a single Li-ion battery and a complete Li-ion battery the processes taken during the charging are a bit different. When it comes to a single Li-ion battery, there are two steps that take place while charging, these are the constant current and voltage source. On the other hand, a complete Li-ion battery is charged through three processes that are, constant current, balance which is not needed when the battery is balanced and finally voltage source. In these processes one can say that during a constant current phase, the charger discharges a constant current which is supplied to the battery in an equally raising voltage, until the voltage limit supposed to be applied in a single cell is reached. However, when charging the battery the charger will reduce the charging power when it reaches the balanced phase, and after doing this the state of all cells is taken to the same level to each other by a balancing circuit to such a point that all the battery gets to the same level and becomes balanced. On the constant voltage stage, when charging the charger uses a voltage that is the same as the maximum cell voltage multiplied to the number of cells in the battery, this is because current reduces as it goes down to zero until the current is under the minimum set amount. When charging a lithium-ion battery it is always advisable to check its voltage limits since charging it with a charger which has more power voltage than the battery might cause and explosion or damage of both the battery and the charger.

On lithium-ion batteries charging can also be affected by temperature and other factors. However, the batteries do not have restrictions on when and where to use, and this is an advantage they come with since you can use them under all kinds of temperatures. The only problem is that they are affected by temperatures when it comes to charging, when you charge the batteries in places with high temperatures it can affect the battery causing it to have a short life span or even spoil it completely. Therefore, it is always advisable that you charge the battery in a room with low or cold temperatures like 4 to 38 °C. At lower temperatures below 4 °C charging is also inevitable but it is always advisable that you change the current used for charging and make it low before charging. However, in most lithium-ion batteries which are specially made for the selling market, one should not charge them in temperatures that go below 0 °C. When charging the battery in such temperatures one cannot see any side effects immediately, since the battery will just appear to be charging normally. However, after a period of time the metallic lithium in the battery can be electroplated when it reaches freezing point, and this can affect the battery, and the damage cannot be fixed even after recharging.

Materials and properties

Lithium, just like all other alkali metals can be said to have a monovalence electron which is easily shared in the chain to create a positively charged ion. Due to this lithium can be seen to be a very good conductor electricity, heat and other reactive objects, but even with all this features lithium remains to be the least reactive when compared to any other alkali metals. The reason lithium has low reactivity as compared to other alkali metals is because of the nearness of its valence electron to the nucleus. Even though lithium is classified as a metal, it is practically so soft it can be cut by a knife. After cutting lithium, the place that has been cut appears to have a shining silvery surface which changes color to gray due to exposure to oxygen. However, it possesses the highest and lowest boiling and melting points as compared to all other alkali metals, but when compared to metals it basically has the lowest boiling point on the list.

Lithium can be said to have very low density, which can be compared to that of oak wood. When compared to all other solid elements in the average temperature it is nearly the least dense of which it is followed by potassium that is like 50% denser than lithium. And also when compared to liquids leaving hydrogen and helium out it is also nearly the less dense. As if that does not make if dense enough lithium is too light it can float on water this making it one of the only metals with this ability.

 

Processing

For a battery to discharge, it all depends on the diffusion of lithium ions on the negative and positive electrodes through the primary collector. This process is based on diffusion through the electrolyte that leads into the cathode. In a situation where high current discharge and charge are being experienced diffusion is the biggest obstacle that can be faced. The reversible and irreversible insertions procedures come up with a volume change in the active electrode materials. There have been some major problems which companies have been facing when processing and manufacturing batteries, however, the efforts in processing and manufacturing the materials for performance improvements and to also avoid volume change has been leading to composite materials which are involved with nanoscaled particles.

Nanoparticles can contain volume change with the smallest chances of cracks appearing composites results in small diffusion path lengths through a slow diffusion stage. On manufacturing, the main focus is always on packing density to amplify active material content and electronic flow which assures charge displacement to collector. Batteries that are circular in shape are manufactured and packed as explained. First the electrolytes are created through paste of active material powders, additives, binders and solvents, after doing this they are taken to a machine to be poured on collector foils which are made of aluminum on the cathode and copper on the anode. Then when all that is done the manufacturers will have to start keeping track of any homogeneous thickness and particle size then afterward slowly cut them into the same width. After the samples are cut, they are then stacked together keeping the anodes apart from the cathodes, then after this they are inserted into cylindrical cases. When the cylinders are inserted, the battery is filled with electrolytes whose primary objective is to make the separator and the electrodes wet. When this process is done any insulators and safety devices are connected. After this, the batteries are charged for the first time just for them to have enough power to be tested. The first charge of a cell determines a lot on the cell performances, Cells life span and also the cycling behavior.

Applications

The use of batteries is more of a daily thing that at this age and time mankind cannot be able to live without. Most of the thing we do every day are connected to batteries in one way or another and in the end we will find out that even living at the comfort of your house without batteries can never be that comfortable. At our houses we find that all electronic devices we use as a mode of entertainment have batteries things like laptops, cameras, watches, etc. Lithium cells always find themselves ending in a long life deal with an electrical devices, this devices are equipped to use lithium-iodine cells that can have a life span of around 15years or more if properly used. However, for less useful objects like toys the lithium battery might end up staying for a long time than the toy, so that is why in such objects we find non expensive types of batteries being used and also which cannot last for so long on the object.

Instead of investing much money on alkaline batteries it is easier to use lithium batteries mostly in objects such as clocks and cameras, even though they are more costly but if price is not an issue then it is the best way to go. The main advantage of using lithium cells is that they will last long, therefore, cutting the cost of buying batteries now and then. However, everything which as an advantage must also have a disadvantage and for the lithium batteries, the users must give attention to the higher voltage that are present in lithium cells before using them as a drop in replacement in objects that are designed to operate on ordinary zinc batteries.

 

Conclusion

In comparison to all batteries it is evident that lithium-ion batteries have the best options when it comes to energy storage and also provide high power and energy for processes such as transportation due to the fact that they have strong electrochemical potential, energy density and theoretical capacity.

 

References

[1] manishi, Nobuyuki, Alan C. Luntz, and Peter G. Bruce. The Lithium Air Battery: Fundamentals. New York: Springer Science Busines Media, 2014. Print.

[2] Ashton Acton, Q. Anhydrides—Advances in Research and Application: 2013 Edition. N.p.: ScholarlyEditions, 2013. Print.

[3] Kazunori, Ozawa, ed. Lithium Ion Rechargeable Batteries: Materials, Technology, and New Applications. N.p.: John Wiley & Sons, 2012. Print.

[4] Smart, M. C., B. V. Ratnakaumar, and K. M. Abraham. Rechargeable Lithium and Lithium Ion Batteries, Issue 29. Ed. M. C. Smart. N.p.: Electrochemical Society, 2008. Print.

[5] Scrosati, Bruno, K. M. Abraham, Walter A. Van Schalkwijk, and JusefHassoun, eds. Lithium Batteries: Advanced Technologies and Applications. N.p.: John Wiley & Sons, 2013. Print.

[6] Doyle, M., E. Takeuchi, and K. M. Abraham. Rechargeable Lithium Batteries: Proceedings of the International Symposium. Pennington, NJ: Electrochemical Society, 2001. Print.

 

 

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