Tuesday, October 7, 2014

How safe is your battery in mobile and laptop?

Lithium-ion battery Facts

A battery is essentially a chemical experiment happening in a small metal canister. Connect the two ends of a battery to something like a flashlight and chemical reactions begin: chemicals inside the battery slowly but systematically break apart and join themselves together to make other chemicals, producing a stream of positively charged particles called ions and negatively charged electrons. The ions move through the battery; the electrons go through the circuit to which the battery's connected, providing electrical energy that drives the flashlight. The only trouble is, this chemical reaction can happen only once and in only one direction: that's why ordinary batteries usually can't be recharged.

The big difference is that the chemical reactions in a rechargeable battery are reversible: when the battery is discharging the reactions go one way and the battery gives out power; when the battery is charging, the reactions go in the opposite direction and the battery absorbs power. These chemical reactions can happen hundreds of times in both directions


                       A rechargeable lithium-ion battery is made of one or more power-generating compartments called cells. Each cell has essentially three components: a positive electrode (connected to the battery's positive or + terminal), a negative electrode (connected to the negative or − terminal), and a chemical called an electrolyte in between them. The positive electrode is typically made from a chemical compound called lithium-cobalt oxide (LiCoO2) or, in newer batteries, from lithium iron phosphate (LiFePO4). The negative electrode is generally made from carbon (graphite) and the electrolyte varies from one type of battery to another—but isn't too important in understanding the basic idea of how the battery works.

All lithium-ion batteries work in broadly the same way. When the battery is charging up, the lithium-based positive electrode gives up some of its lithium ions, which move through the electrolyte to the negative electrode and remain there. The battery takes in and stores energy during this process. When the battery is discharging, the lithium ions move back across the electrolyte to the positive electrode, producing the energy that powers the battery. In both cases, electrons flow in the opposite direction to the ions around the outer circuit. Electrons do not flow through the electrolyte: it's effectively an insulating barrier, so far as electrons are concerned.

The movement of ions (through the electrolyte) and electrons (around the external circuit, in the opposite direction) are interconnected processes, and if either stops so does the other. If ions stop moving through the electrolyte because the battery completely discharges, electrons can't move through the outer circuit either—so you lose your power. Similarly, if you switch off whatever the battery is powering, the flow of electrons stops and so does the flow of ions. The battery essentially stops discharging at a high rate (but it does keep on discharging, at a very slow rate, even with the appliance disconnected).

lithium-ion ones have built in electronic controllers that regulate how they charge and discharge. They prevent the overcharging and overheating that can cause lithium-ion batteries to explode in some circumstances.

How a lithium-ion battery charges and discharges

1.During charging, lithium ions flow from the positive electrode (red) to the negative electrode (blue) through the electrolyte (gray). Electrons also flow from the positive electrode to the negative electrode, but take the longer path around the outer circuit. The electrons and ions combine at the negative electrode and deposit lithium there.

2.When no more ions will flow, the battery is fully charged and ready to use.

3.During discharging, the ions flow back through the electrolyte from the negative electrode to the positive electrode. Electrons flow from the negative electrode to the positive electrode through the outer circuit, powering your laptop. When the ions and electrons combine at the positive electrode, lithium is deposited there.

4.When all the ions have moved back, the battery is fully discharged and needs charging up again.

Why  lithium-ion battery explode?

The lithium-ion battery's explosive tendencies are the result of a process known as thermal runaway. It's essentially an energetic positive feedback loop whereby increasing temperature causes the system to get hotter, which increases the temperature, which causes the system to get even hotter, and so on.

  • Short circuits caused by a tear in the membrane that separates the negative and positive poles of a Li-ion battery will often cause a thermal meltdown.

  • Ambient temperatures exceeding 60 degrees C, repeated overcharging, or unauthorized modifications to the case have all also been reported as the source of battery fires

  • Li-ion packs should be replaced every 36 months or so to avoid pushing a worn cell too hard. 

  • Also, these batteries should be recharged once their capacity hits 50 percent.

About Author

Milan Techglyphs
Milan Techglyphs

Author & Editor

Milan Antony is the founder of TGS.He is a Technology Enthusiast with a keen eye on the Cyberspace and other tech related developments.


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