Batteries and Secondary Cells

Batteries store electrical energy in reversible electrode reactions; secondary (rechargeable) cells can be repeatedly cycled by reversing those reactions with an external charging current.

Definition

A device that stores energy in the chemical states of its electrodes and releases it as electrical current through a redox reaction; in a secondary cell the reaction is reversible, allowing repeated charge and discharge.

Scope

This topic covers the operating principles of batteries: the electrode reactions that store and release charge, the distinction between primary (single-use) and secondary (rechargeable) cells, the architecture of intercalation lithium-ion cells, key performance metrics such as capacity, energy density, and cycle life, and the origins of capacity fade and degradation. It spans classical lead-acid and nickel chemistries through modern lithium-ion systems.

Core questions

• How do the electrode reactions store and release electrical energy?
• What distinguishes a rechargeable secondary cell from a single-use primary cell?
• How does lithium-ion intercalation chemistry achieve high energy density?
• What processes cause capacity fade and limit cycle life?

Key theories

Intercalation electrochemistry

In lithium-ion cells, lithium ions reversibly insert into and extract from layered or framework host electrodes during cycling, storing charge without dissolving the electrode, which enables long cycle life and high energy density.

Reversibility and degradation

Cycle life depends on how cleanly the electrode reactions reverse; side reactions such as solid-electrolyte interphase growth, lithium plating, and structural change consume active material and electrolyte, causing capacity fade.

Clinical relevance

Rechargeable batteries power portable electronics, electric vehicles, medical implants, and grid energy storage; their energy density, safety, and longevity are central to electrification and renewable-energy deployment, driving intensive materials research.

History

Planté invented the rechargeable lead-acid cell in 1859; Whittingham demonstrated lithium intercalation in the 1970s, Goodenough identified lithium cobalt oxide cathodes in 1980, and Yoshino built the first practical lithium-ion cell, commercialized in 1991 and recognized by the 2019 Nobel Prize in Chemistry.

Key figures

• John B. Goodenough
• M. Stanley Whittingham
• Akira Yoshino
• Gaston Planté

Seminal works

• winter2004
• goodenough2013
• newman2004

Frequently asked questions

Why do rechargeable batteries lose capacity over time?

Repeated cycling drives slow side reactions and structural changes—such as growth of the solid-electrolyte interphase, loss of cyclable lithium, and electrode cracking—that permanently remove active material and increase internal resistance.

What makes lithium-ion batteries store so much energy?

Lithium is light and gives a high cell voltage, and intercalation hosts let lithium ions shuttle reversibly between electrodes with little structural disruption, combining high voltage, high capacity, and long cycle life.