Summary
Overview
Michael Stevens and Hannah Fry explore the history and limitations of batteries, from ancient discoveries to modern lithium-ion technology. Hannah argues that lithium batteries are surprisingly inefficient compared to common materials like butter and body fat, and discusses dangerous design flaws while exploring promising future alternatives from sodium batteries to liquid air storage.
Energy Density: Why Lithium Batteries Are Pathetic
Hannah challenges Michael to identify the most energy-dense item in his room, revealing that lithium-ion batteries are shockingly inferior to everyday materials. While wood provides 16 megajoules per kilogram and human body fat offers around 40, lithium-ion batteries deliver less than one megajoule per kilogram - making body fat approximately 40 times more energy dense than the fanciest smartphone battery. This dramatic comparison sets the stage for a broader critique of our dependence on lithium technology.
- Wood provides 16 megajoules per kilogram of energy
- Petrol delivers 45-46 megajoules per kilogram, while olive oil provides 37
- Human body fat contains 39-40 megajoules per kilogram
- Lithium-ion batteries provide less than one megajoule per kilogram
" Lithium ion batteries, you're getting less than one megajoule per kilogram. If you had the choice between a slab of butter or human body fat and a bit of a lithium-ion battery you would be a fool to ever go for the lithium-ion it's pathetic "
" The fat in your butt cheek is 40 times more energy dense than the fanciest lithium battery in your phone "
The Oxford Bell: The Battery That Won't Die
Hannah describes a remarkable battery-powered bell at Oxford University that has been ringing continuously since 1840 - before the invention of the light bulb. This ancient dry pile battery is expected to outlast the physical bell itself, with the four-millimeter clapper likely to wear out before the battery dies. The device demonstrates an incredibly slow, stable release of electricity that has sustained it for nearly two centuries.
- An Oxford bell has been ringing twice per second continuously since 1840
- The battery will outlive the physical bell, which will wear out first
- The battery won't run flat in our lifetimes
- The device works by swinging a pendulum between two bells, switching charge direction
" This bell has been ringing 1840. That's before the invention of the light bulb. Before the invention of the electric light, an electric bell has been ringing nonstop continuously. "
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