Canadian rock legend Neil Young once wrote that rust never sleeps. Young used rust as a metaphor for artistic complacency, an inevitable corrosive influence that gradually ate away at creativity and left behind a crumbling edifice that preserved the superficial shape but destroyed its inner integrity.
Humans have known about rust for as long as we have worked iron. By the early Iron Age, blacksmiths were keenly aware that iron degraded when exposed to air and moisture.
Medieval armourers knew that keeping iron dry mattered, shipwrights knew salt air accelerated corrosion, and farmers knew tools rusted fastest when left in damp soil, even if they did not understand the underlying chemical reactions.
As is often the case, observation preceded explanation by centuries.
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But the chemical revolution of the late 18th century ushered in a revised understanding of the process.
Early attempts to explain both combustion and rusting relied on phlogiston, a hypothetical substance release during burning or decay.
In 1774 French chemist Antoine-Laurent de Lavoisier used experiments to show that a gas was the key agent. He named this gas oxygen in 1878 from the Greek ὀξύς (oxys), meaning sharp or acid, in a mistaken belief that it was an essential component of acids.
As well as showing that oxygen was necessary for combustion, Lavoisier demonstrated that when metals rust they gain mass, combining with oxygen from the air. Rust was no longer a form of decay but instead a process of oxidation.
Iron, when exposed to oxygen and moisture, forms iron oxides, similar in principle to combustion, but slower.
Despite ditching his double-barrelled first name and the aristocratic particle de in an attempt to align himself with the revolutionary spirit, Lavoisier was executed at the height of the Reign of Terror for his role in the hated tax-farming operation, the ferme générale.
He did not, therefore, learn of Michael Faraday’s electromagnetic experiments in the early 19th century. Faraday showed, among many other things, that oxidation reactions involved the transfer of electrons, making it an electrical process. This understanding was central to the development of metal-based batteries.
Iron-air batteries work by harnessing rust itself. They store energy by oxidising iron, essentially allowing it to rust, and then reversing the process using electricity
Lithium batteries are hugely important, but their supply chains are environmentally challenging and geographically concentrated in a few locations. Mining and refining often involve significant water use and local ecological disruption and, while recycling is improving, they still rely on materials such as cobalt and nickel, which raise both ethical and security of supply concerns.
As grid-scale storage expands, these constraints become more acute. Crucially, lithium batteries are also poorly suited to long-duration storage. That is a problem for power systems increasingly dominated by variable renewables such as solar and wind.
Faraday’s shadow looms large over the possible solutions. Last September, a team at the University of Oxford, supported by the Faraday Institution, developed a new class of sodium-ion battery cathodes that store charge on oxygen atoms as well as metal atoms in the crystal structure.
This significantly boosts energy density, potentially allowing sodium, which is much more abundant, to rival lithium at lower cost. Having demonstrated the concept in pouch cells, the team is now scaling and plans to spin out a company to commercialise the materials.
Iron-air batteries, meanwhile, work by harnessing rust itself. They store energy by oxidising iron, essentially allowing it to rust, and then reversing the process using electricity.
These batteries can store energy for 100 hours or more at a fraction of the cost of lithium-ion. That makes them uniquely suited to grid-scale applications where space is available and response time is less critical.
With a demonstrator project ongoing in Donegal, commercialisation could be possible by the end of this decade.
For energy systems such as ours, long-duration storage is not optional. Interconnection is a welcome step, but it cannot fully substitute for domestic resilience during multi-day weather events.
Sodium and iron are abundant and environmentally less disruptive to source than lithium, even if they aren’t impact-free. But their use aligns with broader European goals around strategic autonomy and supply-chain resilience.
Offshore wind capacity is set to grow dramatically, but without adequate storage, curtailment will rise and system costs will follow. Betting solely on lithium would be expensive and exposed to geopolitical risk.
David Thomason from energy consultancy Everoze once told me that the biggest challenge facing hydrogen was that it was a Swiss army knife solution, when energy solutions succeeded on specific use cases.
Not every post-lithium battery will succeed: many promising ideas from zinc-based systems to organic flow batteries have struggled to move beyond pilots. But with sodium and iron we know have two options that suited to specific uses, rather than finding a one-size-fits-all solution.
Hopefully Neil Young would appreciate the irony; in rust we see that the future may not belong only to the shiny and the new.
