Mobile battery technology explained: Why Column rechargeable battery catch fire

Chemistry

The batteries used in mobile devices are a masterpiece of chemical engineering: a large amount of power can be stored in a small cube, allowing mobile devices to run for hours. How does it work? How can it be used to its full potential?

Most modern mobile devices use Column rechargeable battery, which mainly consist of two parts: a pair of electrodes and an electrolyte between them. The electrodes can be made of many materials, such as lithium, graphite, or even nanowires, but without exception, they all rely on the chemical component of lithium. It is an active metal, so it is easy to synthesize with other elements. Pure lithium is so active that it can even spontaneously combust in air, so most batteries use lithium cobalt oxide, which is safer.

Between the two electrodes is the electrolyte, usually a liquid organic solvent, which allows electrons to flow through it. When the lithium battery is charged, the lithium cobalt oxide molecules can capture electrons and then release them during the battery's use, thereby supporting the operation of the phone.

Column rechargeable battery are the most common type of battery because they can store the most power in the smallest space. This is measured by energy density, which is the amount of energy that can be stored per kilogram of battery, measured in watt-hours (Wh). Column rechargeable battery typically have an energy density of between 150 and 250 Wh/kg, while NiMH batteries have a density of only 100 Wh/kg. In other words, Column rechargeable battery are smaller and lighter than other types of batteries, so they can be compacted and still have long battery life.

The chemistry can be summarized as follows: the battery in a device stores energy, and then the chemicals inside release it in any way possible. But this can also be problematic, for example, the batteries in the latest Boeing 787 Dreamliner have caught fire when the plane is parked.

This is one of the flaws of Column rechargeable battery: if the battery is discharged too much, the chemicals inside will break down, forming too much lithium oxide, which will burn and form more lithium oxide, and so on. Chemists call this "thermal runaway", and ordinary people see it as fire, which is why the Boeing 787 was banned from flying by the US Special Operations Administration (FAA). Because the same thing can happen if a battery is punctured, the Transportation Security Administration (TSA) recommends that airline passengers carefully place batteries in carry-on luggage rather than check them in.

Battery Capacity

Battery capacity is measured in milliamp-hours (mAh), which represents the total amount of power a battery can provide. For example, if a battery has a capacity of 1,000 mAh, it can continuously supply 1,000 milliamps of current for 1 hour. If your device draws 500 milliamps, then the battery will last about 2 hours.

However, the battery life of a device is more complicated because the specific amount of power a particular device uses depends on the tasks it is performing. If the device's screen is on, wireless transmission functions are turned on, and the processor is running at full speed, it will use more power than if the screen is off, wireless transmission functions are turned off, and the processor is idle.

Because of this, consumers should be more cautious about the battery life claims of manufacturers - they may reduce the screen brightness or turn off some components to extend the battery life. If you're curious, there are dedicated apps that monitor the power consumption and battery status of mobile devices, such as BatteryMonitorWidget for Android and BaterryLifePro for iOS.

Controlling the Current

Lithium-ion batteries must be carefully controlled because of the potential for fire. Battery manufacturers do this by managing the current through a charge controller. Essentially, each battery has a small computer built into it to prevent it from over-discharging. This component also controls the current that enters the battery during charging, slowing it down as it nears full to prevent overcharging.

Mobile Phone

To demonstrate this process, we charged a Samsung Galaxy Note phone and measured the current throughout the process and compared it to the corresponding proportion of power. As you can see in the figure above, the current is highest at the beginning of the charge and then gradually decreases. The last portion of the charge takes a long time to charge because the controller slows the current to prevent overcharging the battery.

Future Developments

Battery technology is constantly improving, and many laboratories around the world are working on new battery technologies to replace Column rechargeable battery or develop more advanced lithium battery technologies.

Many of these new technologies use supercapacitors, which store electricity for a split second and then release it instantly, similar to a flashlight. Because they involve almost no chemical reaction, supercapacitors can greatly speed up charging time, but current supercapacitors can only release electricity in a split second, which is not suitable for most mobile devices.

Fuel cells that can generate electricity from hydrogen will also be available soon. The Nectar fuel cell system demonstrated at the International Consumer Electronics Show (CES) in Las Vegas in January can run a mobile phone for two weeks using a $10 fuel tank. However, fuel cells are not small enough to be installed in mobile phones - the Nectar system can only charge the lithium battery built into the phone, but it cannot replace it.

Sulfur may also eventually be used in Column rechargeable battery. Scientists at Stanford University in the United States recently developed a battery technology that can use nanotechnology to add sulfur to existing chemical components, which can increase the energy density of Column rechargeable battery by up to 5 times and extend their service life. However, this technology will not be put into the market for several years.

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