The lithium-ion battery – everything you need to know about it
As you well know, lithium-ion technology is our daily bread. But not everyone realizes how common it is in everyone’s life. After all, lithium-ion batteries are not only laptops, but also power tools, vacuum cleaners, drones and even cars. Today we will find out what li-ion batteries really are and why they are so common.
The history of li-ion technology development
Already at the beginning of the 20th century, a high potential of lithium as a battery material was noticed. It is a metal with the lowest density, high electrochemical potential and high energy-to-weight ratio. American physicist George Newton Lewis began experimenting with lithium batteries as early as 1912, but it was only in 1970 that lithium batteries appeared on the market. The first major leap towards lithium-ion cells took place in 1979. Professor John Goodenough and Koichi Mizushima at Oxford University created a new type of lithium battery in which lithium could travel through the battery from one electrode to another in ion form. This solution is the basis for current lithium-ion batteries. Below is a diagram of battery operation. During charging, the lithium ions move from a carbon anode to a cathode made of lithium oxide and another metal and are stored there. When discharged, the process is reversed… but with the design and operation in a moment.The first commercial lithium-ion battery, however, was only built in 1991. It was introduced by Sony in its cameras, and other companies followed in the footsteps of the Japanese giant. The great advantage of lithium-ion technology over the then dominant nickel-cadmium was quickly noticed. The advantage was not only high density, allowing to gather twice as much charge in batteries of the same size, but also high voltage of the cell at 3.6V. The nickel-cadmium cells were getting 1.2V, so we would need three to get a similar voltage. Additional advantages that pushed li-ion forward are no memory effect, low environmental impact and slower self-discharge.
Construction of the lithium-ion battery
At the very beginning, it would be appropriate to distinguish two concepts that we will use in this segment – the cell and the battery.
Cell – basic energy storage device consisting of electrodes, separator and electrolyte. In theory, the cell itself could function as a battery, but in the case of lithium-ion cells it would be dangerous, among other things because of the risk of overheating. The lithium-ion cell can take different shapes, but by far the most common form is the 18650 cylindrical cell. This number indicates dimensions – about 18 mm in diameter and 65 mm in length. Such cells reach a maximum capacity of 3500 mAh, but the current that they can give out may vary depending on their construction. The cells may have different chemical structure, which significantly affects their parameters. The most popular version is lithium-cobalt, but to build the cells can be used, among others, manganese, titanium, aluminum or nickel in different mixtures and proportions. However, most of these options are not cost-effective.
Battery (rechargeable battery) – a battery is a device used to store electrical energy and adapted to give it back in a safe way. For the purposes of this article we limit ourselves to the definition of a lithium-ion battery, which is a reusable battery – it can be charged and discharged.
The battery can consist of any number of cells. Most lithium-ion batteries are made up of the 18650 cells mentioned above, which are connected in series to higher voltages. The same cells can form both a 10.8V laptop battery (6 cells, 3S2P, or 3 in series and 2 in parallel) and a huge Tesla P100D battery with over 400V and 451 kW maximum power. This battery consists of more than 7000 cells of type 18650, similar to the one in the picture above. However, all indications are that the technology will be changed to another li-ion type. Tesla is developing a new type of cell in 2170 format and with a different chemical structure in cooperation with Panasonic. So far the plan is limited to Tesla Model 3, the first budget car of the American technology pioneer.
Performance and lifetime of the lithium-ion battery
The operating time of a lithium-ion battery depends on two issues: capacity and energy consumption. The capacity of a li-ion battery is usually expressed in mAh and changes with each battery as a result of use. The factory maximum capacity of the laptop battery of e.g. 4400 mAh after a year of use can already be reduced to e.g. 4000 mAh. This, of course, directly affects the operating time of the device. If you want to know a little more about battery capacity, have a look at our article on this topic.
The second aspect is energy consumption. In the case of a laptop or a phone, power consumption can result from a wide range of factors such as screen brightness, processor consumption, internet usage and even the temperature and age of the device itself. Depending on each of these conditions, operating times can vary dramatically. Please also note that the lithium-ion battery loses charge at rest.
Each battery is susceptible to aging and those created with li-ion technology are no exception. However, their lifetime may vary greatly depending on the intensity and correct use. A very common case is that an identical battery will last 1.5 years in one person and even 5 years in another. Shorter battery life very often results from inappropriate use. The most harmful mistake that can be made is to discharge the battery to 0% and leave it in this state for a long time.
Unfortunately, very often by completely unconscious action, we damage the battery heavily, and instead of a few years, it refuses to cooperate after a year. If you want to find out more about the correct operation of the battery, please have a look at our guide – How to use batteries.
Further development of the lithium-ion battery?
Although li-ion and similar lithium polymer technology still dominates the majority of mobile devices, this does not mean that there is no change in this area. There are at least a few improvements on the horizon that can push mobile technology even further. Certainly one of them is the new technology mentioned earlier, created by Tesla. There are also improvements on the horizon related to the use of graphene. If a simple and cheap method of obtaining graphene can be found, it can certainly be used to improve lithium-ion cells. However, we will be saying goodbye for the moment, we hope we have sufficiently highlighted the issue of li-ion, but if you have any questions, please feel free to ask them in your comments.
Author: Krzysztof Wołongiewicz