In the past decades, the battery has reshaped our digital lives. Now they are going to bring a revolution to cars.
New energy vehicles powered by lithium-ion batteries can reach over 500 kilometers today, compared to less than 100 kilometers 10 years ago. But replacing the combustion engine cannot happen overnight. It only takes three to five minutes to refuel once, but it may take at least half an hour to fully charge a car battery.
Everyone is waiting for the arrival of a new super battery that can charge as quickly as you can refill a tank, and we are now closer than ever.
Professor Ji Hengxing's lab at the University of Science and Technology of China (USTC) has a super battery with a new electrode material invented for ultra-fast charging.
"It should be possible to charge the battery fully within 10 minutes. It allows a car's mileage to reach the level of 600 kilometers within one charge," said Ji.
Problems with the existing electrode material of batteries
Choosing the right anode material is the key to build a strong battery. Metal lithium has the highest energy density for energy storage. But you can hardly find a battery with a pure lithium anode because it has a potential danger.
When the negative charged electrons flow through the outer wire, there is another flow of positively charged particles within the battery, called lithium ions.
Scientists find that it will be more and more difficult for returning ions to be evenly distributed on the electrode as time goes by. Instead, they will pile up on the surface, creating what has been called a dendrite.
"It results in a structure like a dendrite, which is similar to bamboo growing from the ground and reaching the cathode. Electrons will flow into the battery, forming an internal short circuit," said Ji.
So scientists have decided to replace the metal lithium electrode with graphite. That makes a new battery with a name that people are more familiar with: the lithium-ion battery.
A lithium-ion battery mainly uses graphite as its anode material. Since graphite has a layered structure, it allows ions to travel freely in and out without creating any dendrite. However, it has less energy storage capacity.
A new material: black phosphorous
That's where a new alternative material comes in handy: black phosphorous.
The bad news is that black phosphorous doesn't exist in nature. It needs to be artificially produced in the lab by heating the more common type of red phosphorous to an extremely high temperature. But this is not its biggest shortcoming.
"When the black phosphorus material is store under normal conditions, its edge of the layered structure is not stable. This structure will collapse. And lithium ions cannot get into the structure," Ji explained.
Therefore, scientists need to strengthen the structure of black phosphorous. Ji and his team started to use graphite since it's stable and has a layered structure. To do so, scientists put graphite and black phosphorus into one container. Rapid rotation mixes them up and allows metal balls inside to hit the combination hard.
Metal balls hit both carbon and phosphorus atoms at a just-right angle. Massive energy produced by the impact makes a new connection between the two. New material is created.
This new material has a higher capacity. According to Jin Hongchang, a researcher from USTC, a mobile phone battery usually uses graphite as its anode material. With the black phosphorous, a battery's capacity can be increased by about four times compared to graphite.
If the battery can be successfully commercialized and scientists can find suitable cathode materials and other matching materials, it is possible to charge the battery in minutes.