How This Battery Runs on Sugar… Seriously

Author: Matt Ferrell

You’ve heard of paper straws and cups, but how about a paper battery? One you can compost when you’re done with it. Two companies are already proving it works, one of them with a battery that runs on sugar. So how did humble paper become a next-generation battery material? And could these compostable batteries actually replace the ones we use today?

I love my smart home sensors around my house, but swapping out disposable batteries every few months? Not so much. I make the trek to a recycling center a couple of times a year, but let’s be real: most batteries don’t get that treatment. More than half of all portable batteries still end up in the trash.¹ And while lithium battery recycling is really picking up,² many people don’t know where to drop them off.³

That means hundreds of thousands of tons of batteries go into landfills each year, which is a major environmental hazard. While there have been major advances in battery recycling and making batteries less toxic overall, the reality is that most are still an environmental hazard. Common battery materials like cadmium, cobalt, copper, lead, lithium, and nickel are super toxic ⁴ and can seep into soil, streams, and groundwater.

If recycling isn’t guaranteed, and landfilled batteries pose serious risks, how can we make a battery that goes easier on the environment?

From Wood to Watts

Turns out, paper’s technological revolution didn’t stop at books. It’s now a key ingredient in a new generation of compostable batteries.

Paper fibers are mostly cellulose, a structural material plants use to reinforce their cell walls, providing the strength to stand as tall as a 115-meter (380-foot) redwood tree ⁵ while staying flexible enough to bend in high winds without snapping. Cellulose is the most abundant natural polymer on Earth, made up of long chains of sugar molecules. And if that’s not sweet enough, cellulose isn’t just renewable — it’s also biodegradable.⁶

Researchers exploring greener materials for electronics are leveraging wood’s unique structural properties to create a wooden satellite — which I talk about in another video.⁷ They’re also developing printed paper circuit boards⁸ and even wood-based electrical transistors.⁹ And now, two startups are pushing paper’s potential even further, using it as the backbone for two radically different battery designs.

Bioenzymatric Fuel Cells à la Paper

Based in France, Bioenzymatric Fuel Cells à la Paper, or BeFC, aims to replace the ubiquitous button-battery with a paper-based, compostable alternative.¹⁰ Their design uses carbon electrodes and electrical contacts, avoiding metals entirely.¹¹ And they can do that because, technically, their innovation isn’t a traditional battery; it’s a bioenzymatic fuel cell that runs on sugar. Just like the rest of us … or in my wife’s case … a lot of candy.

How does BeFC’s biobattery actually work? Between its electrodes is a layer of paper infused with sugars and enzymes. When activated by moisture (like by squeezing a blister pack of water) the enzymes break down sugar at the anode, releasing both electrons and protons. The electrons travel through an external circuit, generating electricity, while at the cathode, oxygen from the air reacts with incoming protons and electrons to form water, completing the reaction.¹¹
By mimicking biological energy generation, BeFC has created a lower-waste button battery alternative that won’t leak toxic battery juices or heavy metals like conventional batteries, even if it ends up in the trash. There’s a catch, though: BeFC’s biobattery only outputs 0.75V, so it’s not replacing 1.5V AA batteries anytime soon. The company is instead aiming to have its batteries built right into one-time-use items like medical devices or cold-chain shipping tags that monitor location or temperature.¹¹
This fills a crucial gap in sustainable power, but we still need an environmentally-friendly, compostable solution for higher-powered, and even rechargeable, consumer batteries. That’s where Flint comes in. I stumbled upon them at CES this year.

Powering Up Devices, Powering Down Waste

A lot of us grow up hoping to someday change the world for the better. But after a childhood witnessing natural disasters worsened by climate change, Carlo Charles wasn’t willing to wait for “someday.”¹² While still a student at Nanyang Technological University in Singapore, he co-founded a startup called Flint to commercialize a rechargeable battery with a lower environmental footprint developed by two of his professors, Seok Woo Lee and Hong Jin Fan.¹³

Lee and Fan knew that paper is an ideal separator between a battery’s electrodes because its rough, porous texture provides a large surface for ion exchange, and its absorbent fibers soak up battery juices like a sponge, enhancing conductivity.¹⁴¹⁵ The catch is that you can’t just print anode and cathode metals onto opposite sides of a piece of paper, because the battery will short-circuit through those pores.

So, Lee and Fan infused the paper with hydrogel to create a super thick, flexible sheet of paper onto which they could directly screen print electrode metals front-and-back. That makes paper — yup, regular old paper — the backbone of this battery, the electrode separator, and even the electrolyte once it’s soaked up enough battery juice.¹⁵

Sounds good on paper, but how did it perform?

It achieved volumetric and power densities more than twice as high as many other flexible zinc-based batteries at the time, with a charge/discharge efficiency over 95%. Unfortunately, the batteries didn’t cycle well, with performance dropping to just a quarter of the original after 500 cycles.¹⁵

Still, Charles was determined to make sure this paper-based battery made it out of the lab and into everyday devices. And ever since, Flint has been improving on Fan and Lee’s original design, raising the charge/discharge efficiency to 99.8%.¹⁶

Flint is now achieving gravimetric and volumetric energy densities of 226Wh/kg¹⁷ and 410Wh/L¹⁸, which is comparable to some lithium ion batteries¹⁹ even though it uses a zinc and carbon black anode and a manganese dioxide cathode.

That’s a chemistry similar to typical alkaline batteries, meaning they share the same nominal 1.5 Volts, allowing Flint’s batteries to serve as drop-in replacements.¹⁷ But Flint’s design stands out in two key ways. First, the company claims its water-based electrolyte isn’t hazardous like the potassium hydroxide used in alkaline batteries. Second…and this is crucial…Flint’s batteries can now endure 1,000 charge cycles before their capacity drops to 80%, putting their long-term performance on par with many lithium-ion technologies. That translates to about five to six years of use¹⁶ in everyday products before the battery sees the inside of a garbage bin, or, hopefully, a recycling center. But probably the trash.

That’s why it helps that the paper backbone of these batteries is compostable, breaking down in soil within just six weeks.²⁰¹⁵ Flint is also exploring compostable casings for future models, but for now, the company’s priority is bringing this greener chemistry to market, and that means sticking with industry-standard casings.²¹

Ideally, though, the steel casings, aluminium tabs, and zinc anode would be recycled before the manganese cathode and hydrogel-reinforced paper were thrown to the worms.¹⁶ Because although zinc and manganese are abundant minerals with smaller extraction footprints than lithium (at least according to S&P Global)²², mining always carries an ecological and human cost.²³ Still, if these batteries do end up in landfill, they’ve at least sidestepped the most toxic metals found in consumer batteries like cobalt and nickel.⁴

Safety is enhanced as well. Paper doesn’t rely on a flammable electrolyte like lithium-ion batteries, which eliminates the risk of catastrophic fires if punctured, submerged, or overheated.²⁴²¹ Flint says its batteries operate safely across an impressive temperature range of -20°C to 80°C,¹⁶ far beyond the 15°C to 35°C sweet spot of lithium-ion cells.²⁵ That makes them not just safer, but also more reliable in extreme conditions, whether baking in the sun or freezing in the cold.

To start, Flint is reaching for the low-hanging fruits of coin cells and pouch batteries. But they have plans to tackle its first cylindrical cells, like the double and triple As that fill our junk drawers, next year.¹⁶ The company is also looking to scale up for backup power and energy storage systems.¹⁶ By wiring eight pouch cells in series with a battery management system (BMS), Flint can create a 12V battery, just like a typical lead-acid car battery but 30% lighter, thanks to its higher gravimetric energy density.²⁶¹⁶

Mobility, though? That’s a jump-start beyond this battery’s current power. A greener zinc-based chemistry may never pack the same punch as the lithium and cobalt powering EVs.²⁷²⁸ However, there are plenty of applications that don’t need quite as much oomph. Flint’s flexible, paper-based cells could slip into devices that move with your body, fold into compact tech, or even mold to a device’s curved frame.²¹ Bottom line: you may have a wearable biomedical device built with paper someday, but probably won’t be driving a paper-powered car any time soon.

So what does all this safety and sustainability cost? Flint claims that its batteries are 1.8 times cheaper per kWh compared to lithium-ion chemistries and might cost as little as $50 per kWh once in full scale production.²¹¹⁶

That scale-up from laboratory to startup to first production run is happening fast. In 2023, Charles told TechCrunch:

“I went to a battery plant recently and they have this big slurry machine where you put in the powders to turn them into a liquid form, and they run that huge machine, which is almost half the size of my room, and they run it 12 hours just to make one slurry component. Do you know what we do to make our batteries? We use an egg beater, and we beat it for three hours with our hands. And our numbers are decent even with all that. Imagine if we had the resources and facilities.”²⁹

Just over a year later, in December 2024, Flint secured $2 million in seed funding to bring its technology to market, with plans to begin pilot production mid-2025.²⁶³⁰ Right around the corner.

That’s great news, because decades of effort doesn’t seem to have brought up recycling levels above 50%. Rechargeable and compostable technologies may be the greener way forward for consumer batteries, especially as we add more electronic devices to our daily lives. And with companies like Flint and BeFC bringing real solutions to market soon, change is on the horizon.

In the meantime, don’t let your dead batteries pile up. Drop them off for recycling! In the US, Call2Recycle offers a free locator tool to help you find a nearby recycling center.³¹