Gas–solid battery links hydrogen storage with electricity generation

A Chinese research team has developed the world's first gas-solid battery capable of storing hydrogen at normal room temperature and pressure while simultaneously discharging electricity. This breakthrough bypasses the extreme conditions required by conventional hydrogen containment methods.

The findings were published in the peer-reviewed scientific journal Joule on Wednesday.

"Compared to conventional batteries using liquid electrolytes — the chemical medium that allows electrical charge to flow — such as lithium-ion batteries, all-solid-state batteries fundamentally address the safety issue of battery flammability," said Chen Ping, the corresponding author of the study and a researcher at the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences.

"They also offer potential advantages such as higher energy density, meaning they can store more power in a smaller size, improved cycle performance, and a wider operating temperature range, making them a key development direction for next-generation electrochemical energy storage technologies," Chen added.

However, the widely studied lithium-ion solid-state batteries still face hurdles. These include poor contact between the solid components, slow movement of electrical charges, large changes in the size of the battery electrodes during operation, and high costs. These issues hinder their efficiency and limit their transition from the laboratory to mass production.

To address these problems, Chen's team proposed a new approach in 2018. They suggested using hydride ions — hydrogen atoms with an extra electron that carry a negative charge — as the charge carriers in all-solid-state batteries. These ions are highly reactive, store a large amount of energy, and rely on abundant natural resources. Crucially, they prevent the formation of metal dendrites, which are needle-like structures that can grow inside a battery, cause short circuits, and create safety risks.

The team also developed a novel electrolyte to keep these hydride ions moving smoothly even at low temperatures, and subsequently verified its usability in an all-solid-state hydride ion prototype battery developed last year.

Building on their previous progress, the team introduced hydrogen gas into the battery reaction, enabling it to operate over a wide temperature range from minus 20 C to 90 C. The battery utilizes a heat-releasing reaction between magnesium and hydrogen, which act as the active materials for the negative and positive poles of the battery, respectively. The heat generated by this reaction is harnessed to produce electrical output. In this setup, the solid electrolyte serves as a highway for the hydride ions to travel through, while electrons flow through an external wire to power devices.

Experiments showed that the battery's initial discharge capacity — a measure of how much electrical energy can be released from the battery materials — can reach 1,526 milliamp-hours per gram. Impressively, it retained over 70 percent of its capacity after 60 charge-discharge cycles.

Moreover, when 10 small batteries were stacked together to create a larger battery pack, it generated more than 2.4 volts and successfully powered an LED bulb, demonstrating the technology's practical potential.

Notably, during discharge, hydrogen is converted into hydride ions, while the metal is oxidized to form magnesium hydride. The process reverses during charging: the magnesium hydride releases hydrogen gas and changes back into metal, allowing the hydrogen to be safely locked inside the solid metal.

"The system can function both as a battery for energy storage and as a hydrogen tank, achieving efficient hydrogen storage at ambient temperature and pressure," Chen said.

"As an energy storage device, the battery has a charge-discharge efficiency of around 56 percent, leaving significant room for improvement. However, when employed as a hydrogen storage solution, its hydrogen energy utilization efficiency can reach 93.9 percent, which is one-third higher than that of traditional thermal hydrogen storage methods," she added.

This work has opened up a new path for hydrogen storage. It completely avoids the extreme conditions required by conventional physical methods, such as compressing hydrogen gas under a crushing pressure of 700 atmospheres, or cooling it down to a frigid minus 253 C to turn it into a liquid.

Chen noted that this battery is still in the research and development stage, making its overall market cost difficult to determine. However, a preliminary assessment of material costs shows promise. Magnesium and the raw chemical blocks for the electrolyte both cost several tens of thousands of yuan per metric ton (10,000 yuan is around $1,470), which is relatively low compared to mainstream batteries used today.

The team will continue optimizing the battery's performance, developing superior materials, exploring large-scale assembly processes, and speeding up industrialization, Chen added.