City University of Hong Kong researchers have developed a new water-based battery that uses electrolytes safe enough to be used in tofu production. The battery lasts more than 120,000 recharge cycles and poses no environmental risk when thrown away.
A team of scientists from City University of Hong Kong, Yanan University, the Southern University of Science and Technology, and Songshan Lake Materials Laboratory has built a long-lasting, eco-friendly battery. They published their findings in the peer-reviewed journal Nature Communications on February 18.
The battery uses organic polymer-based electrodes and a water-based electrolyte with a neutral pH of 7.0. The electrolytes are made from magnesium chloride or calcium chloride — the same compounds used as brine to curdle soy milk for tofu . “The electrolytes are environmentally benign and can even be ‘brine’ in tofu production,” the team said.
Conventional lithium-ion batteries pose two major problems. They use flammable solvents that can catch fire if the battery overheats or gets damaged. They also require hazardous waste processing when discarded because they contain toxic materials.
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The team’s water-based design solves both issues. The electrolyte is non-toxic and non-flammable, eliminating fire risk. And because magnesium and calcium are naturally abundant in soil, the battery can be safely disposed of without special treatment. “Our findings represent a considerable advancement in the development of neutral electrolyte-compatible negative electrode materials,” the researchers said.
The battery delivers exceptional performance, lasting more than 120,000 recharge cycles with minimal loss in capacity . For comparison, typical lithium-ion batteries last between 1,000 and 3,000 cycles, while good grid storage batteries manage 6,000 to 10,000 cycles .
This kind of ultra-long life makes the technology ideal for large-scale grid storage, where batteries must charge and discharge daily for decades. It could also work for solar farms, wind energy balancing, and backup power systems where safety matters most.
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However, water-based batteries have a key limitation. Water breaks down at around 1.23 volts, which limits energy density compared to lithium-ion cells that operate at 3.0 to 4.2 volts . This means the new battery is better suited for stationary storage than for electric vehicles or phones.
Despite this boundary, the breakthrough matters because it proves that safe, non-toxic batteries can outperform current technology in cycle life. “Such performance highlights the research potential of this work and underscores its promise for practical application,” the team said. If scaled successfully, this tofu-brine battery could transform how the world stores renewable energy without environmental harm.
