Power Banks Face New Safety Push After Fires

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As fires involving power banks mount, manufacturers are rushing to roll out products using newer battery designs marketed as less likely to ignite, including so-called semi-solid-state and quasi-solid-state batteries.

Compared with conventional batteries that rely heavily on liquid electrolytes, the new designs are being promoted as safer, intensifying an industrywide race to claim an edge on safety. Interest in next-generation batteries is growing, but so are questions about Chinese-made products that claim to use cutting-edge technology not yet believed to be available in stable mass production.

An Intensifying Safety Race

The push to market less flammable products comes amid a rising number of accidents. According to the National Institute of Technology and Evaluation, 1,860 product-related accidents involving lithium-ion batteries were reported between 2020 and 2024. About 85% resulted in fires.

Power banks account for more accidents than any other product category. In July 2025, one caught fire aboard a JR Yamanote Line train and was later confirmed to be the recalled cheero Flat 10000mAh, made by Osaka-based TRA.

The incidents have kept coming. In February, the transport ministry proposed new in-flight safety rules limiting passengers to two power banks and barring their use to charge other devices during flights. The changes are expected to take effect in mid-April.

Why do power banks catch fire? Hajime Kinoshita, a senior executive officer at KRI, an Osaka Gas subsidiary focused on battery-materials research, said the answer lies in the lithium-ion cells they use. "The inside of the battery is filled with flammable liquid, so if something goes wrong, it can ignite," he said.

A drop, crushing pressure, overcharging, or prolonged use in high temperatures can cause heat to build quickly inside the cell. That can break down the electrolyte and release gas. If the temperature keeps climbing, the battery can enter thermal runaway, an abnormal chain reaction driven by heat, leading to smoke or fire.

Kinoshita said the industry's push for higher performance may also have played a role, as manufacturers prioritized greater energy density and capacity over safety.

Makers Bet on Semi-Solid-State Batteries

A more practical answer now gaining traction is the semi-solid-state or quasi-solid-state battery.

Semi-solid-state batteries reduce the amount of flammable liquid used in conventional cells and combine it with materials closer to solids, such as gel-like substances. Quasi-solid-state batteries are built on a similar principle, with less liquid inside. Both are seen as less prone to ignition.

*Smoke rising from a bag of collected combustible waste containing a product with a lithium-ion battery. (Courtesy of the Tokyo Fire Department)*

Electronics company Maxell launched a semi-solid-state power bank in December 2025 that cuts liquid content by about 50% while still allowing roughly 2,000 charge-discharge cycles.

Buffalo plans to release a model in late April using what it calls a more viscous "semi-solid electrolyte," and says it has undergone nail-penetration, crush, and gas-detection tests.

Elecom has made semi-solid-state models a new pillar of its lineup, including a feature that estimates replacement timing based on charge-discharge cycles. TRA has also rolled out quasi-solid-state models, highlighting their safety.

The Solid-State Sales Pitch

At the same time, products claiming to use cutting-edge all-solid-state technology have begun to appear, though the claims are hard to verify.

At BATTERY JAPAN, a rechargeable-battery trade show held at INTEX OSAKA in November 2025, a Chinese manufacturer showcased a power bank it said was equipped with an all-solid-state battery.

The company hasn't decided whether to bring it to Japan, but a representative said a 5,000 mAh model would likely cost about ¥10,000 JPY (about $68 USD) due to high material costs. Overseas, some products are also marketed as "solid-state" even though they are in fact only semi-solid-state.

All-solid-state batteries replace the flammable liquid inside the cell with solid materials. "There is nothing combustible inside an all-solid-state battery. Its defining feature is a high level of safety," Kinoshita said. With less risk of the degradation associated with liquid electrolytes, the technology is also seen as promising for longer life and stronger performance.

Still Short of Mass Production

Still, he said it is too soon to suggest commercial rollout is near. "They may emerge as development progresses, but at this point it is questionable whether they can really be sold as power banks, given supply volumes and cost," he said. Materials development is moving forward, but the technology is not yet at a stage where it can be produced cheaply and consistently at scale.

For now, all-solid-state development is centered on electric vehicles. Toyota aims to launch EVs equipped with the batteries in 2027-28, while Nissan targets commercialization by fiscal 2028. Portable devices also demand smaller, safer, and more powerful batteries. If mass-production techniques advance in EVs, the technology could eventually make its way into power banks.