SECONDARY BATTERY

Secondary batteries have reversible reactions at the electrodes i.e. applying an external voltage to reconstruct the electrodes to their original state; hence the batteries can be rechargeable. Thus rechargeable batteries act as an energy source as well as energy storage system.

There are several types of secondary batteries and the main ones are as follows; lead acid, nickel-cadmium, nickel-metal hydride, lithium ion and sodium ion batteries.

Lead acid batteries use lead plates and sulfuric acid to store energy. In this battery lead serves as the anode and lead dioxide serves as the cathode, which are dipped into an electrolyte solution of sulfuric acid.

Nickel-cadmium batteries use nickel oxide hydroxide and cadmium to store energy. In this battery cadmium serves as the anode and nickel hydroxide as the cathode. The electrolyte is potassium hydroxide (KOH) with small addition of lithium hydrate.

Nickel-metal hydride (NiMH) batteries use nickel metal oxide, a hydrogen absorbing alloy to store energy. The hydrogen storage alloy is a proton inserting negative electrode or anode material. The positive electrode or cathode id nickel hydroxide Ni(OH)2 and the electrolyte is potassium hydroxide (KOH).

Lithium ion batteries use lithium compounds to store energy. The cathode is typically made of lithium metal oxide while the anode is made up of graphite a form of carbon. The electrolyte is lithium salt dissolved in an organic solvent.

Sodium ion batteries use sodium ions to store energy. The cathode is typically made up of sodium metal oxide and the anode is made up of hard carbon. The electrolyte is a sodium salt dissolved in an organic solvent.

The components of a secondary battery are as follows; anode (negative terminal), cathode (positive terminal), electrolyte, separator, current collectors, terminals and jacket or casing.

The anode is the negative terminal of the battery. It is typically made of made of materials such as graphite or silicon.

The cathode is the positive terminals of the battery. It is typically made of materials such as lithium cobalt oxide (LiCoO2) or nickel manganese cobalt oxide (NMC).

The electrolyte is a chemical substance that facilitates the flow of ions between the anode and cathode. It is typically liquid or gel like substance such as potassium hydroxide (KOH) or lithium/sodium salt dissolved in an organic solvent.

The separator is a thin porous material that separates the anode and cathode preventing electrical shorts and ensuring the battery operates safely.

The current collectors are conductive materials that collect electrons from the anode and cathode allowing them to flow through the external circuit.

The terminals are the metal contacts on the battery that connect to the external device allowing the battery to power the device.

The jacket or casing is the outer casing of the battery. It is typically made of metal or plastic which protects the internal components and provide structural strength and integrity.

When a secondary battery is charged, ions flow from the cathode to the anode through the electrolyte and electrons flow through the external circuit. During discharge the process is reversed and the battery releases electrical energy.

The advantages of secondary batteries are as follows; secondary batteries can be reused multiple times reducing the overall cost per use. Rechargeable batteries are environmentally friendly since they reduce waste. Some secondary batteries like lithium ion batteries have high energy density making them suitable for high drain devices. Secondary batteries can be recharged and discharged multiple times extending their life span.

The disadvantages of secondary batteries are as follows; secondary batteries can lose their charge over time, even when not in use. While secondary batteries can be reused they have limited number of charge cycles before their capacity starts to degrade. Secondary batteries require specific charging conditions to ensure safe and efficient charging. Some secondary batteries like lithium ion batteries can overheat during charging or discharging posing a safety risk.

Secondary batteries find applications in the following; electric vehicles where they are used to provide the necessary power for propulsion. Secondary batteries are used in smart phones, laptops and other portable devices to provide power on the go. Secondary batteries are used in renewable energy systems such as solar, wind etc., to store excess energy for later use. Secondary batteries are used in backup power systems such as UPS systems to provide power during outages.

The future of secondary batteries is based on the advances and development of the following technologies; solid state batteries, lithium air batteries, sodium ion batteries so as to enhance safety, improved energy density , reduced cost as well as provide alternative to the traditional lithium ion batteries.

 

SOURCES:

• Batteries in a portable world: A handbook of batteries by Isidor Buchmann.
• Hand book of batteries by David Linden and Thomas Reddy.
• The storage battery: A practical treatise on the construction, theory and use of secondary batteries by Augustus Treadwell.
• Batteries and energy storage: Technology and applications by Paul T. Moseley and J. Garche.
• Electrochemical power sources: primary and secondary batteries by S.S. Dhere and S, M. Joshi.