In my group, Riley, Tess and I are researching and learning about how lithium-ion batteries to function and how they work chemically. Lithium Ion batteries are usually found in iPhones and other types of phones. They are a member of a family of rechargeable batterie. In Li-ion batteries, lithium ions move from the anode to the cathode during discharge, and from the cathode to anode when charging for recharge. When charging a lithium Ion battery, lithium is inserted into the silicon, causing a dramatic increase in volume. On discharge, lithium is extracted from the silicon which returns to a smaller size. In Lithium batteries, the battery transfers electrical charge from a lithium metal cathode through an electrolyte consisting of an organic solvent containing lithium salts over to a carbon cathode. These types of batteries also usually contain a metal coil and a flammable lithium ion fluid. Due to this, tiny metal fragments can float in the liquid. Lithium batteries can be useful for a lot of things like being able to power and charge a phone but they can be very dangerous batteries if not handled well.
In our project, we are using the lithium ion battery for our project which is inside of my iPhone 6s. We bought a foldable solar panel and tested it’s charge during a sunny day and a sunny but somewhat cloudy day. Here are our results:
|12:30||74% (blockage of sun)|
|1:18||At 1:18pm from 12:42 – 1: 18 the battery percentage reached 100%. It took about 50 minutes.|
Since the day was cloudy, the phone didn’t charge as well as it did when it was sunny. In the beginning, it seemed like the charge was going up a little, or, at least, staying stable, but then it started to gradually drop, and eventually it just stopped charging.
Luckily, the foldable solar panel worked for a cheap price of 30$ on amazon. Our group and I still have a lot to accomplish in our project but we are so grateful that we got to see how solar panels work while charging our own phones and other people’s phones.
The movement of Lithium Ion batteries occurs at a fairly high voltage, which causes each cell to produce 3.7 volts. This is much higher than 1.5 volts which are typical of an AA alkaline cell. Lithium ion batteries typically use a lithium metal oxide in the cathode and a carbon-based material in the anode. When the batteries are charging, electrons move from the cathode to the anode, and lithium ions move from the cathode and into the carbon-based material of the anode. If the cathode and anode are connected in this state, lithium ions flow from the anode and return to the cathode, and the electrons travel through the connection to the cathode and combine with the lithium ions. When this occurs, an electric current is generated from the cathode to the anode.
Other than learning about Lithium Batteries and how they work, this week we have been learning and reviewing redox chemistry and questions. An oxidation-reduction reaction is a type of chemical reaction that involves a transfer of electrons between two species. An oxidation-reduction reaction is any chemical reaction in which the oxidation number of a molecule, atom, or ion changes by losing an electron.
The overall reaction on a Li-ion cell:
C + LiCoO2 ↔ LiC6 + Li0.5CoO2
At the cathode:
LiCoO2 – Li+ – e– ↔ Li0.5CoO2 ⇒ 143 mAh/g
At the anode:
6C + Li+ + e– ↔ LiC6 ⇒ 372 mAh/g
In iPhones, the Lithium Ion battery will look like this: