Crunchie Bar Batteries (KS2)

Background

The experiment

A pdf version of this experiment for students is available here. A downloadable version of this experiment for teachers is available here. Please ensure you refer to the safety card.

AIM

To understand:

  1. The different ways we can recycle batteries
  2. The differences between these battery recycling methods
  3. The advantages and disadvantages of these techniques

YOU WILL NEED

  • Crunchie bars
  • rolling pin
  • microwave
  • microwave safe bowl
  • cup
  • spoon
  • plastic plate
  • warm water
  • ice cube tray
  • plastic knife

PROCEDURE

Batteries have three main parts, a positive electrode, an electrolyte, and a negative electrode. In our experiment, the chocolate represents the 2 electrodes and the honeycomb is the electrolyte. When we recycle, we want to separate these parts.

(Add image of “chocolate battery”)

The focus of the experiment is less on battery composition/ operation, and more on the different methods can be used for materials separation, with application to a battery.

Throughout the experiment, investigators are encouraged to think about:

  • Appearance of materials after each separation method.
  • How successful the method was
  • Other materials which may be better suited to each separation method.

METHOD 1 Melting batteries (pyrometallurgy)

Pyrometallurgy: The shredded battery is heated in order to melt. The melted mixture can then be mixed with other materials to make new batteries.

  1. Firstly crush up the battery (Crunchie bar) to make it easier to dissolve. Take 1 Crunchie bar and smash it up into small pieces with the rolling pin.
  2. Add half of the pieces of Crunchie into the microwave-safe bowl, and the other half to a cup.
  3. Then, focussing on melting, heat the Crunchie pieces in the microwave until they are fully melted, stirring every 30 seconds. Take care as it will get very hot!
  4. Carefully, pour the melted chocolate mixture into the ice cube tray and leave to set in the fridge.

QUESTIONS

How easy was it to melt together the crushed Crunchie?

Does the chocolate from the ice cube tray look the same as the original chocolate bar?

LEARING OUTCOMES

Melting the batteries is not always that easy. The material recovered is of lower quality than the original battery material (you can see from your melted crunchie in your ice cube tray!)

METHOD 2 – Dissolving batteries (hydrometallurgy)

hydrometallurgy: the crushed battery is added to a special solution to separate parts of the battery.

  1. Firstly crush up the battery (Crunchie bar) to make it easier to dissolve. Take 1 Crunchie bar and smash it up into small pieces with the rolling pin.
  2. This crushed battery material is then added to a special solution to separate parts of the battery. Fill the cup with warm water, add the crushed crunchie bar and stir with a spoon. Keep stirring until all the honeycomb is dissolved.

QUESTIONS

What happened to the honeycomb and the chocolate when they were stirred in warm water?

Is there any way to get the honeycomb and chocolate back out of the water again?

LEARING OUTCOMES

Dissolving the batteries is not always that easy. Different parts of the battery will dissolve more easily than others (you can see from the different ways that the chocolate and honeycomb dissolve!)

METHOD 3 – Separating battery components

  1. Take a whole Crunchie bar, and using the knife, try to separate all of the chocolate from the honeycomb so that they are completely separate. Take care when cutting with a knife!

QUESTIONS

Are there any other ways to completely separate the chocolate and the Crunchie?

What are the advantages/ disadvantages of this method?

LEARING OUTCOMES

If separated successfully using the method where you break apart the battery (closed-loop recycling), the honeycomb and chocolate pieces can easily be “reused”. As you will have found, however, there is quite a lot of difficulty in getting all the components completely separate without any contamination. Scientists from the Faraday Institution are trying really hard to find ways to do this!

In the research lab

Lithium-ion battery (LiB) research is a really important part of chemistry, as these batteries are found in everyday portable devices (such as phones and laptops), and even in electric vehicles, such as the Nissan Leaf. LiB research has gained traction in recent years, due to the worldwide movement towards the electrification of the vehicle industry.

In the School of Chemistry, and in various other departments at the University of Birmingham, there are numerous academics, PhD and Postdoctoral researchers who have dedicated their studies to LiB research, though projects led by the Faraday Institution. To find out more about our research at Birmingham please see:

Recycling lithium-ion batteries from electric vehicles

Faraday Institution Research Projects: Lithium Ion

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This work is licensed under a Creative Commons Attribution 4.0 International License.