Difference Between Rechargeable and Non Rechargeable Batteries

Main Difference – Rechargeable vs. Non Rechargeable Batteries

Batteries provide a way to power electric devices that cannot be plugged into a mains supply at all times. Cars, mobile phones, laptops, and children’s toys can be powered by batteries. Depending on their ability to be re-used, batteries are classified into two categories: non rechargeable (primary) and rechargeable (secondary) batteries. The main difference between rechargeable and non rechargeable batteries is that rechargeable batteries can be put to use again after have been fully discharged once, while non rechargeable batteries cannot be charged again once they discharge fully.

What are Non Rechargeable Batteries

Batteries consist of two electrodes called the cathode and the anode, which are placed in electrolytes. When the electrodes are connected, chemical reactions take place at the cathode and anode, as we have discussed with an example on the article about anodes and cathodes. These chemical reactions result in a flow of electrons from the anode to the cathode. These electrons have electrical energy, and if we connect an electric component between the electrons’ path, the electrons can lose their energy as they go through the component. The electrical energy that the electrons lose can be then converted into a form that is useful to us. For instance, a light bulb converts the electrical energy into light energy (and thermal energy), and a motor converts the electric energy into kinetic energy.

Before we discuss the difference between chargeable and rechargeable batteries, let us first look at a typical alkaline battery to see how it works:

Difference Between Rechargeable and Non Rechargeable Batteries - Alkaline_battery_longitudinal_section

A longitudinal section through an alkaline battery

At the anode, zinc reacts with the hydroxide ions released from the cathode, producing zinc oxide and water, and releasing electrons in the process:

$\mathrm{Zn+2OH^-\rightarrow ZnO+H_2O+2e^-}$

At the cathode, the released electrons are combined with manganese (IV) oxide and water to produce manganese (III) oxide and hydroxide ions:

$\mathrm{2MnO_2+H_2O+2e^-\rightarrow Mn_2O_3+2OH^-}$

For these reactions to continue, the ions are continuously travelling through the electrolyte while the electrons are travelling outside the electrolyte through the wires that connect the anode and the cathode. This creates an electric current in the wire.

Alkaline batteries are non rechargeable. This means that these reactions can only take place in the above direction. Once all of the manganese (IV) oxide has been converted into manganese (III) oxide, the reactions come to a halt and the battery can no longer produce an electric current.

What are Rechargeable Batteries

With rechargeable batteries, it is possible to reverse the reactions that allow them to drive electrons around a circuit. A good example for rechargeable batteries is the lithium-ion battery, which is used to power most mobile phones and laptops. When the batteries are being used to power up devices, we say the battery is discharging. While this is happening, the “negative terminal” releases lithium ions, which travel through the electrolyte to the positive terminal. At the same time, electrons flow outside the circuit from the negative terminal towards the “positive terminal”. During charging, the battery takes energy from an external source to reverse these flows: lithium ions flow from the “positive terminal” towards the “negative terminal”, replenishing the battery’s ability to conduct current again.

Difference Between Rechargeable and Non Rechargeable Batteries - Lithium-ion_Battery

A lithium-ion battery designed for use in a laptop

However, the performance of rechargeable batteries does become degraded over time. The rechargeable predecessors to lithium-ion batteries included nickel-cadmium batteries. These batteries had several disadvantages: their performance tended to suffer if they are frequently overcharged, or if they were not frequently allowed to drain fully. In addition, cadmium was a toxic metal which meant that improperly disposed nickel-cadmium batteries posed an environmental hazard.

Difference Between Rechargeable and Non-Rechargeable Batteries

Usage after Complete Discharge

Rechargeable batteries can be re-used after charging, once they have been completely discharged.

Non rechargeable batteries can only be fully discharged once. After that, the battery cannot be charged and it cannot be used to produce an electric current.

Cost

The price of rechargeable batteries is higher compared to that of non rechargeable ones. However, over the long term, using rechargeable batteries is more cost effective.

Non rechargeable batteries are cheaper compared to rechargeable ones.