What Is a Lithium Ion Battery?
A lithium-ion battery is a rechargeable battery that charges and discharges as lithium ions move between the positive and negative electrodes.
They are used in electric vehicles, industrial storage batteries, smartphones, and laptop computers. Compared to lead-acid batteries, the voltage is higher, and the ratio of active materials that can store energy in the battery is smaller, which has the advantage of making the battery smaller in size compared to batteries with the same amount of energy.
Batteries are products that deteriorate as they are repeatedly charged and discharged and eventually reach the end of their useful life. Lithium-ion batteries are no exception, but they have been confirmed to have a longer life than other batteries in an endurance test called a cycle test.
Applications of Lithium-Ion Batteries
Typical applications for lithium-ion batteries include IT, automotive, and energy.
Lithium-ion batteries have a high energy density, making it possible to produce small, thin, and high-capacity batteries. Applications such as cell phones and notebook PCs require smaller and lighter batteries, and lithium-ion batteries are widely used to meet these demands, with lithium-ion batteries being used in almost all products.
They are also used as a medium and large-sized batteries for electric vehicles (EVs) and energy storage systems, taking advantage of their high electric capacity.
Structure of a Lithium Ion Battery
A lithium-ion battery is similar to a typical storage battery, consisting of a cathode, an anode, and an electrolyte in which they are immersed.
The cathode and anode are separated by a membrane called a separator that allows lithium ions to pass through but not electrons, and the gap between them is filled with electrolytes. The lithium ions in the electrolyte move from the positive electrode to the negative electrode during charging, generating a potential difference (voltage) between the negative and positive electrodes, which can be connected to the desired circuit to generate a current (discharge).
In charging, lithium ions are transferred from the positive electrode active material to the negative electrode active material by applying an external voltage. After charging, lithium ions can move again in the direction of discharge, so the battery can be used repeatedly for charging and discharging.
Other Information on Lithium Ion Batteries
1. Electrode Materials
Cathode-active materials are mainly lithium-based oxides, such as lithium cobalt oxide (LCO). The type of cathode active material greatly affects the performance of lithium-ion batteries.
Carbon-based materials such as artificial graphite, natural graphite, and hard carbon are the main active materials for the negative electrode. Less commonly used materials include silicon (Si) and tin (Sn) alloys and lithium oxides such as titanium (Ti) and niobium (Nb).
2. Reaction Equation of Discharge in Lithium-Ion Battery
The reaction equation for discharge in a lithium-ion battery varies depending on the type of metal oxide and other factors, but an example is shown below. When charging, the reaction occurs in the opposite direction of when discharging, i.e., from the right side to the left side.
- Reaction on the cathode side: Li(1-x)MO2 + xLi^(+) + xe^(-) → LiMO2
*M is a metallic element - Reaction on the anode side: LixC → C + xLi^(+) + xe^(-)
- Reaction of the whole system: Li(1-x)MO2 + LixC → LiMO2 + C
3. Safety of Lithium-Ion Batteries
Abnormal Heat Generation in Lithium-Ion Batteries
The electrolyte used in lithium-ion batteries is a carbonate-based organic solvent that is highly flammable. Therefore, if a lithium-ion battery malfunctions and the temperature rises excessively, it may cause a fire or explosion.
Most abnormal heat generation is caused by a short circuit (short circuit) between electrodes. Short circuits between electrodes can be caused by various factors, such as strong external shocks and lithium metal precipitation (lithium dendrites) in the electrodes. Accidents involving the ignition of lithium-ion batteries can occur not only by mishandling but also during normal use.
How to Prevent Lithium-Ion Battery Ignition Accidents
The majority of lithium-ion battery-related ignition accidents are caused by misuse. Therefore, it is necessary to understand the proper handling of lithium-ion batteries in order to prevent ignition accidents. Specific precautions are as follows.
- Always use the charger specified by the manufacturer when charging.
- If you notice anything unusual during charging, stop using the battery immediately and consult the manufacturer or seller.
- If the lithium-ion battery swells or smells strange, stop using it and replace it with a new one. It is also essential not to disassemble or replace the lithium-ion battery forcibly, as it is difficult to replace it in some products and is not recommended.
It is also essential to select products with guaranteed safety. Products that have passed the safety standards set by the government are marked with the PSE mark, which indicates safety.