New hydrogen battery can operate four times colder than before — meaning denser and longer-lasting EV batteries
Future electric cars could abandon lithium ion batteriesthanks to a new advance in storing hydrogen energy at much lower temperatures than was previously possible.
Researchers at the Tokyo Institute of Science have created a hydrogen battery that uses magnesium hydride as an anode and hydrogen gas as a cathode, along with a solid electrolyte with a crystal structure.
Hydrogen batteries with solid-state components already exist, just like hydrogen fuel cells. The former, however, require high operating temperatures, while the latter struggle to be as efficient as lithium-ion batteries, as well as store hydrogen gas under high pressure. But with this new hydrogen battery, scientists have reached the full theoretical storage capacity of MgH.2 anode and high ionic conductivity at room temperature.
Solid base
The heart of this hydrogen battery lies in its solid electrolyte. Formed from barium, calcium and sodium hydride, the electrolyte has a crystalline structure that provides both high electrochemical stability and high ionic conductivity, particularly when dealing with hydrogen ions, at relatively low temperatures.
In operation, the battery works much like a lithium-ion battery, except instead of positively charged ions moving through the electrolyte, this new battery uses hydride ions that carry a negative charge and can pass through its crystal structure.
Upon supplying energy (discharging), the hydrogen gas in the cathode undergoes a chemical reaction that reduces it to hydride ions which move through the electrolyte to the magnesium anode, where they oxidize to form MgH.2. In this state, oxidation-reduction (redox) reactions take place, causing a loss of electrons from the negatively charged anode. These flow through an external circuit to the cathode, which now has a net positive charge and, in doing so, powers the connected devices or systems.
The opposite happens when charging, with an external power source invoking redox. Here, MgH2 The anode releases hydride ions which pass through the electrode and are then oxidized at the hydrogen electrode to form hydrogen gas. As such, the electrons come from the H2 electrode to that of Mg until the reduction reaction can no longer occur, meaning the battery is in a fully charged state.
With this battery design, hydrogen gas can be stored and released on demand in a solid-state cell, with a capacity of 2,030 mAh per gram (for reference, lithium-ion batteries tend to have a capacity of 154 to 203 mAh per gramwhile some of the best phones have lithium-ion battery capacities of 5,000 mAh for the entire cell).
Although the operating temperature is just below the boiling point of water, meaning such a battery is not ready for use in everyday electronic devices like smartphones or laptops, it could pave the way for more efficient and easier hydrogen storage. This, in turn, could lead electric vehicles to adopt hydrogen batteries rather than lithium-ion batteries, which are heavy and suffer from degradation as well as a drop in efficiency over their lifespan.
Better storage of hydrogen without the need for high-pressure systems, extreme cooling or high operating temperatures could further open up the use of hydrogen as a green energy source. Indeed, their carbon footprint could be lower than that of fossil fuels and current hydrogen-based electricity systems.
Hydrogen has often been presented as one of the means of transition to green energy, even if its production, storage and use in electricity distribution systems remain a niche activity. If developed and put into production, this battery breakthrough could continue to propel hydrogen as the fuel of the future.
