Paper bags and cardboard boxes normally headed for the trash were carbonized into anodes for lithium-ion batteries, and the resulting electrodes survived 1,200 charge cycles — roughly twice the durability of anodes used in current phone batteries

A paper bag that carried someone’s lunch on Tuesday has a plausible future inside a phone.

Researchers at NTU Singapore have worked out how to bake kraft paper, the brown stuff in grocery bags and cardboard boxes, into the carbon anodes that lithium-ion batteries run on. Not as a metaphor. The actual packaging, cooked down into working electrodes.

Sheets of kraft paper get laser-cut and stacked into lattice shapes, a few of them resembling a spiky piñata, then loaded into a furnace at 1,200 degrees Celsius with the oxygen stripped out. Deprived of oxygen, paper cannot burn. It sheds water and volatile compounds instead, until what remains is nearly pure carbon, still holding the shape it was cut into. Carbonisation is the technical term for the process.

Incineration, which is where most kraft paper currently ends up, gives off carbon dioxide.

An anode, in plain terms, is a parking spot for ions. A lithium-ion battery shuttles those ions back and forth between two electrodes, and on charge they travel to the anode and slot themselves between stacked sheets of carbon atoms, sitting tight until the battery is asked to do some work. Graphite is the usual host because, as EE Power explains, it can absorb a large number of ions without its structure buckling. Any replacement has to manage the same trick, thousands of times over, without falling apart.

What the lab cells did

Cells built with the paper-derived anodes were charged and discharged up to 1,200 times, which NTU puts at roughly double the working life of anodes in a phone battery today. Batteries using them absorbed crushing energy up to five times better than conventional equivalents, a toughness the team credits to how the paper fibres sit against one another before they go into the heat.

One team, one study, one batch of lab cells. Published in the journal Additive Manufacturing, the work belongs to materials science well before it belongs to any product roadmap, and the same paper reports reversible capacities of 65 to 140 milliamp hours per gram. Commercial graphite, by comparison, delivers roughly 372 milliamp hours per gram. Energy density is still the open question here.

Why the anode costs so much

Why should anyone care where an anode comes from? Cost, mostly. As reported by E&T magazine, the anode is worth 10 to 15 per cent of the total cost of a lithium-ion battery. Almost all of that is graphite, mined or synthesised, and graphite has quietly become one of the tightest chokepoints in the energy transition.

By 2035, the International Energy Agency expects China to supply around 80 per cent of battery-grade graphite. In October 2025, Beijing announced export controls covering graphite anode materials, cathode materials and battery manufacturing equipment. The agency’s 2026 critical minerals outlook puts a figure on the exposure: a full disruption to battery-grade graphite trade would threaten more than 300 billion US dollars a year of production outside China.

Demand is not helping either. Graphite consumption grew between 6 and 8 per cent in 2024, in step with nickel, cobalt and rare earths. Per the IEA, energy uses, chiefly electric vehicles and grid storage, drove 85 per cent of that growth in battery metals demand over the two years prior.

Seen against that, a furnace full of old cardboard stops looking like a curiosity.

From spiky piñata to factory floor

“Paper is used in many facets in our daily lives,” said Assistant Professor Lai Changquan of NTU’s School of Mechanical and Aerospace Engineering, who led the project. It turns up as gift wrapping, heavy-duty packaging, protective wrapping and void filling on building sites. Very little of it gets managed at the disposal end beyond incineration, and paper waste made up close to a fifth of everything Singapore threw out in 2020.

Where the appeal really sits, though, is the invoice. As documented by IOM3, the team’s pitch is that manufacturers currently pay for mined graphite, while a plant built around this process would be paid to accept wastepaper instead. The same disposal fees that currently cover incineration would instead cover the raw material.

NTUitive, the university’s commercialisation arm, has filed a patent on the technique, and commercialisation is reportedly next on the agenda. Scaling a laser-cut lattice to industrial volumes is its own engineering problem, and a harder one than it looks from a bench.

As reported by The Straits Times, carbonised paper blocks have also turned up doing duty as gas filters and fire-protection insulators, giving any future plant more than one product to sell while the battery application matures. Professor Juan Hinestroza of Cornell University, who had no involvement in the research, said in the same report that the work might push other researchers towards different cellulose-based leftovers, naming textiles and packaging as candidates.

That is the part with legs. Kraft paper is one waste stream among dozens built from the same fibres, and almost every one of them costs money to get rid of. Turning even a fraction of that into something a battery factory wants to buy changes the arithmetic of what counts as rubbish in the first place.