3.2.1 The manufacture of lithium ion batteries
In this activity, you are asked questions on the following video which explains why lithium ion batteries, now used in electric powered cars, are different from their predecessors.
Activity 5 Lithium ion batteries
Timing: Allow about 10 minutes
Consider the following questions as you watch the video, and note down your answers.
- a.Why is it important to make the lithium metal alloy as pure as possible, and with as uniform a chemical composition as possible?
- b.What is the role of the electrolyte (transport medium)?
Download this video clip.Video player: t271_2018j_openlearn_vwr026-640x360.mp4
Transcript
[MUSIC PLAYING]
NARRATOR
The lithium ion battery is the power source for modern electric vehicles. These days, everyone's heard of lithium ion batteries, but what makes them so special? First of all, each battery is made up of many smaller batteries called cells. Let's take a closer look at one to see how it works. The electrical current reaches the cells via conductive surfaces-- in this case, aluminium on one side and copper on the other. And just as in every other battery, there is a positive and negative electrode called the cathode and the anode.
The cathode, or positive electrode, is made of a very pure lithium metal oxide. The more uniform its chemical composition, the better the performance and the longer the battery life is. As you'd expect, the anode or negative electrode is located on the other side. It's made of graphite, a form of carbon with a layered structure. The battery is filled with the transport medium, the electrolyte, so that the lithium ions carrying the battery's charge can flow freely. This electrolyte must be extremely pure and as free of water as possible in order to ensure efficient charging and discharging.
To prevent a short circuit, there's a layer placed between the two electrodes, the separator. To the tiny lithium ions, the separator is actually permeable. The experts call this property microporosity. Let's take a look at what happens when a battery is charged. The positively charged lithium ions pass from the cathode through the separator into the layered graphite structure of the anode where they're stored. Now, the battery is charged.
When the battery discharges-- that is, when energy is removed from the cell-- the lithium ions travel via the electrolyte from the anode through the separator back to the cathode. The motor converts the electrical energy into mechanical energy, making the car go. The amount of energy available and how long the batteries last is closely related to the quality of the materials used. To sum it all up, higher quality, pure materials, along with customised formulations lead to longer battery life and better battery performance.
[MUSIC PLAYING]
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Answer
- a.When the lithium metal alloy is purer and has a more uniform chemical composition, the battery performance and battery life increase.
- b.It allows the lithium ions to flow freely between the anode and cathode through the micro-porous layer.
Lithium ion power supplies are not just used in toys; the technology features in mobile phones, handheld tools, electric cars and some household goods. Major advancements in high-capacity rechargeable batteries are expected in upcoming years, which will drive the proliferation of electric vehicles.