AN INTRODUCTION TO LITHIUM-ION VS. LEAD-ACID BATTERIES What is Lithium? Lithium is a chemical element with the symbol Li. It is the lightest metal and the least dense solid element. Traces of Lithium can be found in water, plant-life, food and even the human body. Its high reactivity never occurs freely in nature, but only when lithium is transformed into a compound. Commercial extraction comes from rocks/granite with high abundance of lithium-containing minerals.

What is a Lithium-ion battery? A Lithium-ion battery or Li-ion battery, is a type of rechargeable battery in which lithium ions move from the negative electrode to the positive electrode during discharge and back when charging.

They should not be confused with lithium batteries, which are primary (non-rechargeable) batteries that you may recognise in the form of an AA dry cell or a button/coin cell battery used in your remote car key for example. Lithium-ion batteries are most commonly found in portable electronics due to their high energy density and low self-discharge. This battery type has undoubtedly played a key role in the development and widespread use of today s mobile devices and laptop computers.

What are the main benefits of Lithium-ion? Lithium-ion offers the highest energy storage to smallest weight/volume ratio of any kind of today s commercially available battery. Very fast recharge and longer life are also very compelling arguments for this battery type.

How do Lithium-ion batteries scale up and challenge applications traditionally performed by Lead-Acid?

Lithium-ion batteries are made up from multiple cells (typically 3.2V or 3.7V) that can be connected in serial configuration to attain the required voltage. To better understand this arrangement, consider two extreme ends of the spectrum. Exide s Motorbike Li-Ion battery contains four cells of 3.2V each, connected in serial to produce a total nominal voltage of 12.8V. At the other end of the scale, Tesla s Model S electric car uses an 85 kWh battery pack containing 7,104 Lithium-ion battery cells.

Are there any disadvantages of Lithium-ion? The strong plus points come at a significantly higher cost. This is due to more expensive raw materials, complex assembly of

components and high precision required in the manufacturing process. To put cost into context, Exide s Li-Ion Motorbike battery costs around 3-4 times more than a lead-acid equivalent and the approximate cost of a Tesla battery pack in 2019 was US$30,000.

Lithium-ion batteries also pose some unique safety hazards. A small fault or damage can create an internal short-circuit and a subsequent build-up of heat. In extreme cases, an overheated battery can possibly burst into flame. Yet this situation is rare and is protected against with a battery management system to prevent operation outside each cell s safe operating range i.e. min-max charge, safe temperature, etc.

What is the future of Lithium-ion? Lead-acid battery technology has come a long way over recent years. It still offers the only economically viable solution to engine starting and the vast majority of supply battery requirements. Continuous development is pushing lead-acid technology beyond its previous limits of performance and has even demonstrated success in new, full electric modes of Personal Rapid Transit. Of course, future developments in Lithium-ion will be focused on reducing battery costs, further improving safety and addressing the question of recycling the end of life product. Within a decade we are likely to see crossover between lead-acid and Lithium-ion in a number of applications, but no great change of dominance of one technology over the other.

Many electric cars still use lead-acid batteries A 12V lead-acid battery often compliments the main traction battery in electric vehicles to stabilise the electrical system and maintain security/safety features. Learn more about this topic on page 21.

Tesla Model S charging at the Zoutelande dunes,

in the Netherlands

11