Battery School Pt.3

What is lithium-ion?

How come lithium-ion batteries have 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. Additionally, due to outdated technology, the batteries could only be used a few times before they expired.

So, when lithium-ion became well known for its high energy density* and lightweight, 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.

Read more in this article: Foundations of a battery

Li-ion batteries. Differences in shape

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)

Lithium-ion chemistries

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	Abbr.	Technology	Discovered	Usage areas
Lithium Cobalt Oxide	LCO	LiCoO₂	1991	Broad use, laptops
Lithium Iron Phosphate	LFP	LiFePO₄	1996	Mobility, power tools, EV, ESS
Lithium Manganese Oxide	LMO	LiMn₂O₄	1996	Hybrid EV, cell phones, laptops
Lithium Nickel Cobalt Aluminium Oxide	NCA	LiNiCoAlO₂	1999	EV
Lithium Nickel Manganese Oxide	NMC	LiNixMnyCozO₂	2001	EV, power tools, ESS

Safety and Certifications

It's important to remember that li-ion batteries hold great energy density, but it also has their safety hazards. During regular handling, a Li-ion battery poses no more dangers than conventional batteries. But lithium also carries the potential of thermal runaway* owing to mechanical or thermal breakdowns, which can cause it to catch fire if exposed to air or water.

With precise quality standards, the right installation, and cautious handling, these hazards may be avoided. Li-ion is a dangerous good and must be transported by air, land, or water with a UN38.3 certificate.

Conclusion

• Lithium-ion batteries come in a wide range of shapes, but the shape does not define the chemistry.
• 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? Let's get in touch for further discussion!

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.