Lithium-ion batteries

In plain language

A lithium-ion battery stores energy by moving lithium ions from one electrode to the other through a liquid or gel that conducts them. When the battery charges, lithium ions move into one electrode, and when it discharges they travel back and push electrons round the outside circuit as useful current. The ions fit into gaps in the electrode structure rather than rebuilding it, which is why the cycle can be repeated many times.

This design is now the main battery type in electric cars. Battery electric cars sold in the EU in 2025 had average batteries close to 70 kWh, and in China below 60 kWh, according to the International Energy Agency. Battery prices have also fallen, with a further 8% drop in 2025 according to the IEA, but the price now varies a lot by region, and the batteries still carry real fire and recycling risks.

Technical explanation

Lithium-ion cells work by intercalation, in which lithium ions are inserted into and removed from the structure of host electrodes during charge and discharge. M. S. Whittingham's 1976 paper in Science, "Electrical Energy Storage and Intercalation Chemistry", described the reversible reaction of lithium with layered titanium disulfide as the basis of a new battery system. Commercial cells use a lithium-containing positive electrode and a carbon-based or other negative electrode, separated by a porous membrane and an electrolyte. Energy density, the energy stored per kilogram or per litre, decides how much range a vehicle gets from a given pack. The IEA gives peak cell-level energy densities of up to 205 Wh/kg for LFP (lithium iron phosphate) and up to 265 Wh/kg for NMC (nickel manganese cobalt) chemistries, and up to 175 Wh/kg for sodium-ion. These are maximum figures, and the test conditions behind them were not checked.

Cost and performance have changed quickly, but the best published analyses differ on the rate. Ziegler and Trancik (2021) re-examined how quickly lithium-ion technologies have improved, and found that previous metrics can underestimate improvement rates for stationary storage applications. Their full text was not checked for this profile, so this record does not quote their figures. The IEA's 2026 review reports that average battery prices fell 8% in 2025. Pack prices in China were 30% lower than in North America and 35% lower than in Europe in 2025, against gaps of 20% and 25% in 2022. LFP chemistry made up over 55% of EV batteries deployed globally in 2025.

Safety and recycling are the main technical limits. Thermal runaway is a self-heating failure in which a cell overheats and can burn or explode. A 2021 review of lithium-ion battery fire studies in Applied Sciences identifies battery chemistry and state of charge as the strongest influences on the likelihood of thermal runaway. Recycling of spent cells is an active research area. A 2022 review in Recycling by Islam and Iyer-Raniga, covering 93 articles, reports that publications on this topic are increasing exponentially.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Limitations and open problems

• Thermal runaway can cause fires, and a 2021 review finds battery chemistry and state of charge have the greatest influence on how likely it is (Ghiji and colleagues, 2021).
• Energy density limits range per kilogram. The IEA gives 400 to 600 km for an average SUV with lithium-ion batteries, against up to 350 km for sodium-ion (IEA, 2026).
• Outside China, almost 80% of batteries use nickel-containing chemistries, which ties the sector closely to nickel supply (IEA, 2026).
• Recycling of spent cells is an active research area, as reviewed by Islam and Iyer-Raniga (2022).
• Regional price gaps mean cost figures depend on where batteries are made and sold (IEA, 2026).
• The long-run cost analysis by Ziegler and Trancik (2021) was not checked in full text, so this profile gives no historical cost-decline figures.

Possible future uses

Timeline

1. 11 Jun 1976M. S. Whittingham publishes 'Electrical Energy Storage and Intercalation Chemistry' in Science. Sources: [1]
2. 2021Ziegler and Trancik's re-examination of lithium-ion technology improvement and cost decline is published in Energy & Environmental Science. Sources: [2]
3. 2025Average battery prices fall 8% and LFP chemistry reaches over 55% of EV batteries deployed globally. Sources: [3]
4. 2026The IEA's Global EV Outlook 2026 reports regional battery pack price gaps for 2025, compared with 2022. Sources: [3]

Glossary

Intercalation

The insertion and removal of ions, such as lithium, into the layered or framework structure of an electrode without rebuilding it.

Thermal runaway

A self-heating chain reaction inside a battery cell that can lead to fire or explosion.

Energy density

The amount of energy a battery stores per kilogram (Wh/kg) or per litre (Wh/L); higher means more range for the same weight or size.

State of charge

How full a battery is, given as a percentage of its usable capacity.

Sources

1. peer reviewed paper
   Electrical Energy Storage and Intercalation Chemistry
   M. S. Whittingham. Science, 11 Jun 1976. DOI: 10.1126/science.192.4244.1126. Accessed 22 Oct 2026.
2. peer reviewed paper
   Re-examining rates of lithium-ion battery technology improvement and cost decline
   Micah S. Ziegler, Jessika E. Trancik. Energy & Environmental Science, 2021. DOI: 10.1039/D0EE02681F. Accessed 22 Oct 2026.
3. government report
   Global EV Outlook 2026: Electric vehicle batteries
   International Energy Agency, 2026. Accessed 22 Oct 2026.
4. review article
   A Review of Experimental and Numerical Studies of Lithium Ion Battery Fires
   Matt Ghiji, Shane Edmonds, Khalid Moinuddin. Applied Sciences, 29 Jan 2021. DOI: 10.3390/app11031247. Accessed 22 Oct 2026.
5. review article
   Lithium-Ion Battery Recycling in the Circular Economy: A Review
   Md Tasbirul Islam, Usha Iyer-Raniga. Recycling, 28 May 2022. DOI: 10.3390/recycling7030033. Accessed 22 Oct 2026.

Revision history

3 changes since this profile was created.