Lithium-ion batteries function via an intercalation mechanism, a reversible insertion of ions into a layered host material. During discharge, lithium ions (\(Li^+\)) de-intercalate from a negative electrode (anode), typically graphite, and move through a non-aqueous electrolyte to intercalate into a positive electrode (cathode), typically a metal oxide. Electrons travel through the external circuit, creating current.
Lithium-ion Intercalation Mechanism
- M. Stanley Whittingham
- John B. Goodenough
- Akira Yoshino
The concept of intercalation is central to the success of lithium-ion batteries. Unlike older battery chemistries where the electrodes undergo significant chemical phase changes, intercalation involves lithium ions acting as ‘guests’ that slide into and out of the ‘host’ crystalline structure of the electrode materials. For the anode, the host is typically graphite, which has a layered structure allowing \(Li^+\) ions to fit between its graphene sheets, forming \(LiC_6\). For the cathode, the host is a metal oxide, such as lithium cobalt oxide (\(LiCoO_2\)), where lithium ions occupy layers between cobalt oxide sheets.
This process is highly reversible and does not dramatically alter the host’s structure, which leads to a long cycle life with minimal degradation. The movement of ions is facilitated by a non-aqueous organic electrolyte, as lithium is highly reactive with water. A micro-porous polymer separator keeps the anode and cathode from touching and short-circuiting while allowing ions to pass through.
During charging, an external voltage forces the process to reverse: lithium ions are extracted from the cathode, travel back across the electrolyte, and re-insert into the graphite anode. The high electrochemical potential of lithium, combined with its low atomic weight, allows for batteries with very high energy density and specific energy, which is why they have revolutionized portable electronics and are enabling the transition to electric vehicles.
Type
Disruption
Usage
Precursors
- Discovery of lithium metal and its high electrochemical potential
- Fundamental research on intercalation compounds in the 1970s
- Development of stable non-aqueous electrolytes
- Early, unsafe prototypes of rechargeable lithium metal batteries
Applications
- smartphones, laptops, and tablets
- electric vehicles (EVs)
- cordless power tools and garden equipment
- grid-scale energy storage systems
- implantable medical devices and hearing aids
Patents:
- US4357215A
Potential Innovations Ideas
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Historical Context
Lithium-ion Intercalation Mechanism
(if date is unknown or not relevant, e.g. "fluid mechanics", a rounded estimation of its notable emergence is provided)
Related Invention, Innovation & Technical Principles