A secondary cell is any kind of electrolytic cell in which the electrochemical reaction that releases energy is reversible. Widespread examples are rechargeable batteries found in portable consumer electronics such as notebook computers and cell phones, and car batteries. Electrolytic cells are composed of an electrolyte (usually water or another solvent capable of dissolving various ions of interest), a cathode and an anode. ... English chemists John Daniell (left) and Michael Faraday (right), both credited to be founders of electrochemistry as known today. ... A chemical reaction occurs when vapours of hydrogen chloride and ammonia meet to form a cloud of a new substance, ammonium chloride Chemical reaction is a process that results in the interconversion of chemical substances [1]. The substance or substances initially involved in a chemical reaction are called reactants. ... Rechargeable batteries are batteries that can be restored to full charge by the application of electrical energy. ... Laptop with touchpad. ... Motorola T2288 mobile phone A mobile phone is a portable electronic device which behaves as a normal telephone whilst being able to move over a wide area (compare cordless phone which acts as a telephone only within a limited range). ... Most car batteries are lead-acid batteries. ...

Unlike primary cells, secondary cells must be charged before use. Once used, the batteries can be recharged by using an external electric source that reverses the cell reaction and creates a non-equilibrium mixture of reactants. Commonly used secondary cell chemistries are nickel cadmium (NiCd), nickel metal hydride (NiMH), lithium ion (Li-ion), and Lithium ion polymer (Li-ion polymer). A primary cell is any kind of electrolytic cell in which the electrochemical reaction of interest is not reversible. ... This does not cite its references or sources. ... In chemistry, the reactants are the substances that exist at the start of a chemical reaction. ... The nickel-cadmium battery (commonly abbreviated NiCd and pronounced nye-cad) is a popular type of rechargeable battery for portable electronics and toys using the metals nickel (Ni) and cadmium (Cd) as the active chemicals. ... Modern, high capacity NiMH rechargeable batteries A nickel metal hydride (or NiMH) battery is a type of rechargeable battery similar to a nickel-cadmium (NiCad) battery but which does not contain expensive (and environmentally risky) cadmium. ... Lithium ion batteries (sometimes abbreviated Li-Ion) are a type of rechargeable battery commonly used in consumer electronics. ... Lithium ion polymer batteries, or more commonly lithium polymer batteries (Abbreviated Li-Poly or LiPo) are rechargeable batteries which have technologically evolved from lithium ion batteries. ...

Charging

During charging, electrons are taken from the cathode and given to a chemical species in the electrolyte. At the opposite side of the battery, electrolyte ions transfer an electron to the anode. This results in a net flow of electrons from the cathode to the anode. Energy is stored by this process when the electron transfer processes require the input of energy. This energy is released when the battery is operated in the reverse direction. The Electron is a fundamental subatomic particle that carries an electric charge. ... Diagram of a copper cathode in a Daniells cell. ... An electrolyte is a substance that dissociates into free ions when dissolved (or molten), to produce an electrically conductive medium. ... Electron transfer (ET) is the process by which an electron moves from one atom or molecule to another atom or molecule. ...

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Diagrams of the charging and discharging of a secondary cell battery.

Image File history File links File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Image4SC.JPG Summary Secondary Cell Diagram Image 4 Licensing File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

Diagrams and equations of the charging and discharging of a lead-acid cell.

Active Components

The active components in a secondary cell are the chemicals that make up the anode, cathode, and electrolyte. The anode and cathode are made up of different materials, both of which can undergo an electrochemical reaction with the electrolyte, causing oxidation and reduction. Diagram of a zinc anode in a Daniells cell. ... Diagram of a copper cathode in a Daniells cell. ... An electrolyte is a substance that dissociates into free ions when dissolved (or molten), to produce an electrically conductive medium. ... English chemists John Daniell (left) and Michael Faraday (right), both credited to be founders of electrochemistry as known today. ... The most fundamental reactions in chemistry are the redox processes. ... Semi-accurate illustration of a redox reaction Redox reactions include all chemical processes in which atoms have their oxidation number (oxidation state) changed. ...

Example: Nickel Metal Hydride

Nickel oxyhydroxide (NiOOH) is the active component in the cathode, while the anode is composed of hydrogen in the form of metal hydride. The electrolyte of this secondary cell is an aqueous form of potassium hydroxide. The chemical compound potassium hydroxide, (KOH) sometimes known as caustic potash, potassa, potash lye, and potassium hydrate, is a metallic base. ...

In the discharge process, the nickel oxyhydroxide is reduced to nickel hydroxide and the metal hydride is reduced to an alloy. An alloy is a combination, either in solution or compound, of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties. ...

Nickel-Metal Hydride

Energy Density

Graph of energy densities of several secondary cells

The comparison of energy output of the active components to the overall size of a cell and those components is known as energy density. Many of today’s secondary cells have high energy densities, with the exception of the lead cell battery. Small size and high energy output, make these batteries perfect for small portable objects. Image File history File links Secondary_cell_energy_density. ... Image File history File links Secondary_cell_energy_density. ... Energy density is the amount of energy stored in a given system or region of space per unit volume or per unit mass, depending on the context. ...

Advantages/Disadvantages

Each secondary cell has its own advantages and disadvantages when compared to other secondary cells and primary cells. Only time and advances in science will perfect the use of the secondary cell.

Lead-acid batteries, invented in 1859 by French physicist Gaston Planté, are the most commonly used rechargeable batteries today. ... The nickel-cadmium battery (commonly abbreviated NiCd or NiCad) is a popular type of rechargeable battery for portable electronics and toys. ... NIMH or NiMH may refer to: National Institute of Mental Health, a part of the United States National Institutes of Health. ... Lithium ion batteries (sometimes abbreviated Li-Ion) are a type of rechargeable battery commonly used in consumer electronics. ... Lithium ion polymer batteries, or more commonly lithium polymer batteries (Abbreviated Li-Poly or LiPo) are rechargeable batteries which have technologically evolved from lithium ion batteries. ...

See also

• Battery
• Fuel cell

This does not cite its references or sources. ... A fuel cell is an electrochemical device similar to a battery, but differing from the latter in that it is designed for continuous replenishment of the reactants consumed; i. ...

External links

• Portable Rechargeable Battery Association
• Batteries in a Portable World - Handbook on rechargeable batteries.
• Cell Chemistry
• BatteryUniversity.com