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APR 21, 2020 Pageview：11
Lithium-ion batteries are a type of rechargeable lithium batteries and are commonly used in conventional consumer devices. These cells are well known for their high-energy densities as well as other prosperous features that make them a reliable battery technology.
How is a lithium-ion battery made?
Lithium-ion batteries are commonly found in several conventional devices in our daily lives. However, more people are concerned about their capabilities for their intended devices and less about how these batteries came to be. Making a lithium-ion battery isn’t as complicated as one would think because as it only involves a few industrial processes that apply for any general battery as well. The following is a summary of how the batteries are manufactured:
Step 1. Designing the container
The first step would be designing the container of the battery, which is also the basic structure of the cell. The container holds all the contents of the cell and also determines the size of the battery.
Step 2. Making the electrodes
While the container size is being designed, the electrodes are prepared using different materials for the anode and cathode. The anode is made out of carbon while the cathode is manufactured from a metal oxide.
Step 3. Designing the separator
Usually, a paper strip is rolled into a small tube then sealed at the bottom. It is then inserted in the middle of the battery and used as the separator.
Step 4. The electrolyte
The battery container is then filed with the electrolyte made of lithium-ion salt in an organic solvent and is usually non-aqueous.
Step 5. Designing the collectors
The current collectors are soldered into the desired shape and fixed into the cells.
Step 6. Packaging
At this point, the battery is done but still naked. They are, therefore, sealed and wrapped up with the intended wrappers and stickers.
How do lithium-ion batteries work?
What do we know about lithium-ion batteries in general? Well, just like any other battery, it is made up of two electrodes, the anode and cathode, separator and an electrolyte. The electrolyte is responsible for carrying positively charged lithium ions from the anode to the cathode and back through the separator. The anode is usually considered a positive electrode, while the cathode is negative. The movement of lithium ions creates free electrons within the anode, which in turn creates a charge at the positive current collector. This forces the electrical current to flow from the designated current collector through the electrical device to the negative current collector. The separator is used for restricting the flow of electrons inside the cell.
When it comes to discharging processes, lithium ions tend to transport the current within the cell from the negative electrode towards the positive one. This is conducted through a non-aqueous electrolyte as well as a separator diaphragm. During charging, the charging circuit tends to give out a higher voltage than the battery produces, forcing a charge current to flow within the cell. The current flows from the positive electrode to the negative one. This is typically the reverse direction of the flow of current for a discharge process. Once the lithium ions are on the negative electrode, they get embedded in the porous electrode material through intercalation.
The charging procedure
The charging process intended for lithium-ion batteries comes in three stages, and they include:
When it comes to the constant current phase, the charger tends to apply a constant current on the battery at an increasing voltage. This occurs until the voltage limit per cell is achieved.
The balance phase is, however, not required once the battery is balanced. In this stage, the charger tends to cycle the charging process on and off. Doing this helps reduce the average current. While this happens, the state of charge for single cells is brought to the same level using a balancing circuit until finally, the whole battery is balanced. However, chargers tend to charge the cells differently. For example, some fast chargers tend to skip this stage while others achieve it by charging each cell on its own.
In the constant voltage phase, the charger tends to apply a voltage that is equal to the maximum cell voltage multiplied by the number of cells in series to the pack. This process occurs gradually as the current drops to 0 until it is below a standard threshold of 3% of the previous constant charge current. Topping charge is recommended for lithium-ion cells once the voltage drops below 4.05V per cell. However, this should be done once per 500 hours as advised by experts. Failure to adhere to the current and voltage limitations of the cells can lead to battery failure or explosions.
The limits to the charging temperature of lithium-ion cells are usually more intense as compared to the operating ones. The chemical reactions within a lithium-ion battery tend to perform rally well in elevated temperatures. However, extended exposure to such temperatures tends to reduce the life of the battery gradually. Also, lithium-ion batteries can be charged better under cold temperature ranges and can even allow fast-charging. This occurs within a temperature range of about 5 to 45 °C. It is recommended that one should charge their lithium-ion cells within this range of temperature. If you decide to charge your lithium-ion battery within a low-temperature range of about 0 to 5 °C, you are advised to reduce the charging current.
During charging in low temperatures, the small rise in temperature above average because of internal cell resistance if viewed as beneficial. However, high temperatures during charging processes may degrade the battery while at extreme temperature, the battery performance is severely affected. At shallow temperatures, the internal resistance of the cells tends to increase, and this can lead to a slower and longer charging process. Lithium-ion batteries designed for conventional consumer devices are not to be charged below 0 °C. This is because possible electroplating can take place on the negative electrode in a subfreezing charge, and this might turn out to be a permanent problem. For your safety and that of the battery, many lithium-ion-based devices are not allowed to be charged out of the 0 – 45 °C temperature range.
Lithium-ion batteries are the game-changers of battery technology due to their exemplary performances in their various applications. Knowing more about these batteries allows you to get the most out of them in your intended use.
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