Battery technology is the subject of feverish research worldwide. Better storage does not only depend on the availability of smartphones and the range of electric cars – the switch to renewable energy depends on whether it is possible to “temporarily store” the energy that is naturally generated in order to harmonize electricity production and consumption.
At the moment you can only use reservoirs. Swiss engineers are working on a concept of gigantic storage towers to store the electricity from wind turbines. (Read: “Have the Swiss solved the biggest problem of clean energy?”) In addition to completely new approaches in storage technology, attempts are being made in many places to improve the technology of today’s lithium batteries.
One approach is to replace the liquid components with solid substances. This should increase the energy density of the cells, so you can store more electricity per kilogram of battery. It also aims to improve battery life and safety.
Solid instead of fluid
Scientists at MIT report a breakthrough in their research. A novel solid-state cell is supposed to overcome the problems of earlier approaches. The new concept comes from Ju Li’s laboratory and was presented in the journal “Nature Energy”.
In a normal lithium battery, a liquid electrolyte moves back and forth between the anode and cathode when the battery is charged and discharged. The volatile material is problematic with regard to battery fires. If it is possible to replace the electrolytes used today, it would also be conceivable to change the material of the anodes. The goal is an anode made of pure lithium, it would enable a much higher energy density than the material mixes used today. “There is a lot of work on solid-state batteries with lithium metal electrodes and solid electrolytes,” says Li, but all of these attempts have encountered a number of problems.
Material becomes fragile
One of the biggest problems is that when the battery is charged, atoms accumulate inside the lithium metal, causing it to expand. When discharged, the metal shrinks again when the battery is used. This ups and downs of dimensions mean that the material becomes brittle.
MIT’s new battery architecture is designed to overcome this problem. It is a complex technical solution in the nano range. Here, the anode consists of various solid materials that act as conductors and insulators, they build a honeycomb structure from nanotubes. The massive lithium metal is inserted into the tubes and has enough space within the tubes for expansion.
Honeycombs in nano dimensions
“We designed a structure that enables three-dimensional honeycomb electrodes,” said Ju Li, professor of materials science and engineering at MIT. The cavities in each tube of the structure allow the lithium to “crawl back into the tubes, so no voltage builds up that breaks up the solid electrolyte”.
According to the researchers, this structure combines the properties of solids with those of liquids. The lithium behaves like a liquid and is held in a solid crystalline structure by the small tubes. The expanding and contracting lithium moves in the tubes like the pistons of a car engine in their cylinders, explains Li. Because these structures are built in the nano range, the result is like “an engine with 10 billion pistons, with lithium metal as working fluid”, Li said. The idea of taming difficult substances in nanotubes was recently used to present a membrane that derives energy from the delta of rivers. (Read: “This is how you can get the energy of 2000 nuclear power plants from river water”)
Quadruple energy density
During the charging and discharging process, the shape of the anode remains stable and there is no liquid electrolyte at all. “In our case, everything is really solid,” says Li. “It is neither liquid nor gel-like.”
He expects a battery of the new type to have only a quarter the weight of conventional batteries with the same charge. Conversely, one could formulate: With the same dimensions of the battery, an electric car can achieve four times the range.
Source: Nature Energy
Charges faster and does not burn: IBM builds super batteries with materials made from sea water
Revolution for the electric car: New wonder battery looks like a waffle
Have the Swiss solved the biggest problem of clean energy?
So you can get the energy of 2000 nuclear power plants from river water
How new nuclear power plants want to stop climate change