Super fast charging batteries could soon be a reality

By Alice Clifford via SWNS

Superfast charging batteries could soon be a reality after a scientific breakthrough.

Researchers say they have cracked the mystery that was standing in the way of making the next generation of quick-charging batteries.

New lithium metal batteries with solid electrolytes are lightweight, inflammable, pack a lot of energy, and can be recharged very quickly.

However, they have been slow to develop due to their mysterious habit of short-circuiting and failing.

Now, a team from Stanford University says they have solved the mystery.

They have found that tiny defects, indentations and impurities such as dust can cause enough stress to lead to battery failure when charging.

Batteries are susceptible to these cracks and defects as most of today’s leading solid electrolytes are ceramic.

While this material enables fast transport of lithium ions, like ceramics in our homes, they can develop tiny cracks on their surface.

Similarly to a pothole when it rains, the more lithium that puts pressure on these fractures, the bigger the gaps become.

With these growing cracks, lithium can then seep through and connect the cathode and anode, causing a short circuit.

Thanks to this discovery, the team is now looking into ways to coat the electrolyte surface to prevent these cracks or repair them when they emerge.

A real-world solid-state battery is made of layers upon layers of cathode-electrolyte- anode sheets stacked one atop another.

The electrolyte’s role is to physically separate the cathode from the anode, yet allow lithium ions to travel freely between the two.

If the cathode and anode touch or are connected electrically in any way a short circuit occurs.

A subtle bend, slight twist, crack or speck of dust caught between the electrolyte and the lithium anode will cause crevices, allowing the lithium to snake through and connect the cathode and anode.

During fast charging, these fractures open and allow lithium to intrude, leading the battery to fail.

Many of these cracks or dents are less than 20 nanometres wide. As a comparison, a sheet of paper is about 100,000 nanometres thick.

Author William Chueh, an associate professor of materials science and engineering in the School of Engineering, said: “Just modest indentation, bending or twisting of the batteries can cause nanoscopic fissures in the materials to open and lithium to intrude into the solid electrolyte causing it to short circuit.

“Even dust or other impurities introduced in manufacturing can generate enough stress to cause failure.”

In each experiment, the researchers applied an electrical probe to a solid electrolyte, creating a miniature battery.

They then used an electron microscope to observe fast charging in real time.

When the electrical probe merely touched the surface of the electrolyte, the lithium gathered beautifully atop, even when the battery was charged for less than one minute.

However, when the probe pressed into the ceramic electrolyte, mimicking the mechanical stresses of indentation, bending and twisting, it was more likely the battery would short circuit.

Dr. McConohy, a lithium ion battery research engineer, said: “Given the opportunity to burrow into the electrolyte, the lithium will eventually snake its way through, connecting the cathode and anode.

“When that happens, the battery fails.”

Dr. Xin Xu, a postdoctoral scholar of materials science and engineering, added: “Lithium is actually a soft material, but, like the water in the pothole analogy, all it takes is pressure to widen the gap and cause a failure.”

This ground-breaking discovery could lead to the successful development of solid electrolyte quick charging rechargeable batteries.

By being able to make more of these energy-dense, fast-charging, non-flammable, long lasting lithium metal batteries, could help create more electric vehicles that are becoming more crucial in the fight against climate change.

Dr. Teng Cui, a postdoctoral scholar of mechanical engineering, said: “These improvements all start with a single question: Why?

“We are engineers. The most important thing we can do is to find out why something is happening. Once we know that, we can improve things.”

The study was published in the journal Nature Energy.