How smartphone batteries work

Smartphone batteries are one of the most important parts of a smartphone today. Without them our phones won’t power on or stay on for long. You must have heard people complain about how their smartphone batteries work poorly or do not last very long. Everyone now wants their next phone to come with a huge battery.

Companies and advertisers bombard our collective consciousness with adverts promising bigger, long lasting batteries with unbelievable fast charge capabilities.

These days, everyone seems to be fussing over their batteries. We want to know how to charge them, how not to damage them and how to prolong their lifespans.

These notwithstanding, batteries are very misunderstood by a lot of people. Many of whom do not actually know how smartphone batteries work or what they do?

Read: Screen on Time and Battery performance

What is a battery?

A battery is a device consisting of one or more electrochemical cells with external connections for powering electrical devices such as flashlights, smartphones, cars etc.

A battery works by simply converting chemical energy directly into electrical energy. Chemicals of choice used in batteries are high energy metals like lead, zinc or lithium.

Key terms to note

  • Electrolyte: is any substance (solid, liquid, paste or gel) that allows current to flow through it.
  • Electrode: is a solid metal conductor of electricity. It helps to connect a battery to its load.
  • Electron: is a negatively charged subatomic particle.
  • Ion: an atom or molecule with a net electrical charge (i.e. either positive or negative).
  • Cation: a positively charged ion
  • Anion: a negatively charged ion

  • Cell: a battery compartment
  • Current: this is a steady flow of electrons
  • Redox reactions: A redox (reduction-oxidation) reaction is a type of chemical reaction in which the oxidation state of atoms are changed. Electron floating around the nucleus of an atom love to do so in pairs. An electron floating by itself will want to seek another free electron so it can be paired up. This means that atoms with free electrons will either lose or gain electrons so as to balance (or pair) up their free electrons.

So if atom A has a free electron, it will lose it to atom B in order to become stable. This is called oxidation. Atom B then receives a free electron from Atom A to pair up its own free electron and becomes stable. This is called reduction.

Battery structure

Understanding the structure of a battery goes a long way to understanding how it works. A battery is a single cell divided into two half cells. The two half cells are connected by an electrolyte containing cations. Both half cells are separated by a barrier to prevent the ions (i.e. cations and anions) on both sides from mixing.

One half cell contains electrolytes and a negatively (-ve) charged electrode called the anode. The anode is where the negatively charged ions (anions) migrate to.

The other half cell contains electrolytes and a positively (+ve) charged electrode called the cathode. The cathode is where the positively charged ions (cations) migrate to.

For a battery to work, electrons will flow from the anode into the phone and then out to the cathode i.e. from anode side into phone and out into the cathode side.

How smartphone batteries work?

The anode side of a full battery is highly negatively (-ve) charged while the cathode side is highly positively charged. When connected to a load, the anions in the electrolyte will migrate to the anode.

When they get to the anode, oxidation then occurs. The anions will lose their free electrons. These electrons then travel through the anode into the phone and power it up. After travelling through the smartphone’s circuit board, they then enter the cathode. When there is no longer enough electrons on the anode side or the charges (-ve and +ve) have become balanced on both sides, the battery “dies”.

Read: What is SoT?

When the phone’s battery dies and we connect a charger to it, it reverses the chemical reaction that occurred during discharge.

This is due to the fact that the current from the charger contains electrons. These electrons increases the negative charge of the cathode and makes it more negative than the anode. Thus, the cathode and anode switch roles. This forces the electrons to flow back to their original position (i.e. the anode).

When this happens, we can then say that our battery is recharged and ready for use. As soon as the charger is removed, the electrons from the anode begin their journey all over again.

Thank you for reading to the end. As always, ensure to check out our links for more information


  1. To be honest how you take your time to research and write about these topics so well is incredible. The words are simple to understand, thank you for this enlightening post about battery.

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