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Battery School Part 3 – What is lithium-ion and how does it work?

How come lithium-ion batteries has gained so much popularity in the last 10–15 years?

Early portable devices were powered with nickel cadmium or nickel metal hydride batteries (or even lead acid!) which made the devices bulky and unpractical to use. Plus, because of old technology the batteries would only last for a couple of uses.

A floating orange battery surrounded by feathers and lightning sparks, symbolizing it's light weight and high power.
Li-ion batteries are both lightweight and have high energy density.

So, when lithium-ion became well known for its high energy density* and light weight, it became the clear battery choice for many product developers. Fast forward a couple of years and lithium-ion batteries now come in a large variety of sizes and chemistries.

How does a lithium-ion battery work? A lithium-ion battery is composed of an anode, a cathode, a separator, and an electrolyte. As the battery is being used, lithium ions move between the electrodes (anode and cathode) through the electrolyte. As a li-ion battery is being charged, lithium ions move from the cathode to the anode. As the battery is being discharged, ergo used, the cycle reverses and the lithium ions move from the anode to the cathode. Li-ion batteries have a self-discharge* rate between 1.5 to 2% per month.

The cathode for a li-ion battery is generally made from LiCoO₂ (LCO) or LiMn₂O₄ (LMO), whilst the anode is usually made from graphite or other carbon materials.

When it comes to the different shapes of li-ion cells, it is easiest to divide them into four groups:

  • Small cylindrical

  • Large cylindrical

  • Flat or pouch (soft, flat body - such as those used in phones and laptops. Also called lithium-ion polymer)

  • Rigid plastic case with large threaded terminals (such as prismatic cells)

What lithium-ion chemistries are there? One way of separating the different chemistries apart is through looking at what technology is used for the positive electrode component. A few of the listed examples down below are some of the more well-known examples. Another way to differentiate the chemistries apart is through which technology is used for the anode.

​Positive electrode




Usage areas

Lithium Cobalt Oxide




Broad use, laptops

Lithium Iron Phosphate




Mobility, power tools, EV, ESS

Lithium Manganese Oxide




Hybrid EV, cell phones, laptops

Lithium Nickel Cobalt Aluminium Oxide





Lithium Nickel Manganese Oxide




EV, power tools, ESS

Safety and Certifications

It’s important to remember that li-ion holds great energy density, but it also has its safety hazards. During normal handling, a Li-ion battery does not involve greater risks than other batteries. But Lithium may ignite if exposed to air or water, along with another risk as thermal runaway* due to mechanical or thermal failures. To avoid these risks, it is very important with accurate quality controls, correct installation, and careful handling. Li-ion is considered a dangerous goods and it is mandatory with a UN38.3 certificate for air, road, or sea transportation.


  • Lithium-ion batteries come in a wide range of shapes, but the shape does not define which chemistry it has inside.

  • Li-ion batteries are one of the major drivers in the electrical vehicle and energy grid storage development.

  • Li-ion batteries are popular thanks to their high energy density and light weight.

  • Li-ion batteries are considered dangerous goods.

Curious to find out more about lithium-ion batteries, or are you looking to implement some into your product design? Send us a message and we’ll help you get started.

Fact box

Energy density: The amount of energy stored per volume or mass unit in a system or chemical substance.

Self-discharge: The battery’s charge reduces gradually over time, even if it is not connected to any device.

Thermal runaway: Chain reaction inside the battery that occurs when the battery reaches a temperature that causes a chemical reaction. This produces even more heat and causes more chemical reactions.