Water could form the basis for future, particularly inexpensive rechargeable batteries. Empa researchers have succeeded in doubling the electrochemical stability of water with a special saline solution. This takes us one step closer to using the technology commercially.
In the quest to find safe, low-cost batteries for the future, eventually we have to ask ourselves a question: Why not simply use water as an electrolyte? Water is cheap, in abundant supply, doesn’t burn and can conduct ions. But it has one major drawback:
It is only chemically stable up to a voltage of 1.23 volts. In other words, a water cell provides three times less voltage than a customary lithium ion cell with 3.7 volts, which makes it poorly suited for applications in an electric car. A cost-effective, water-based battery, however, could be extremely interesting for stationary electricity storage applications.
Saline solution without free water
Ruben-Simon Kühnel and David Reber, researchers from Empa’s Materials for Energy Conversion Laboratory, have now discovered a way to potentially solve the problem: The saline electrolyte has to be liquid but so concentrated as not to contain any “surplus” water.
For their experiments, the two researchers used the special salt sodium FSI (precise name: sodium bis(fluorosulfonyl)imide). This salt dissolves extremely well in water: seven grams of sodium FSI and one gram of water produce a clear saline solution (see clip). As all the water molecules are clustered around the positively charged sodium cations in a hydrate envelope in this liquid, there are virtually no unbound water molecules left.
Cheap to produce
The researchers discovered that this saline solution displays an electrochemical stability of up to 2.6 volts – i.e. nearly twice as much as other aqueous electrolytes. The discovery could be the key to inexpensive, safe battery cells; inexpensive because, apart from anything else, the sodium FSI cells can be constructed more safely and thus more easily than the familiar lithium ion batteries.
The system has already withstood a series of charging and discharging cycles in the lab. Until now, however, the researchers have been testing the anodes and cathodes of their test battery separately – against a standard electrode as a partner. In the next step, the two half cells are to be combined into a single battery. Then additional charging and discharging cycles are scheduled.
Empa’s research activities on novel batteries for stationary electricity storage systems are embedded in the Swiss Competence Center for Heat and Electricity Storage (SCCER HaE), which coordinates research for new heat and electricity storage concepts on a national level and is led by the Paul Scherrer Institute (PSI). If the experiment succeeds, inexpensive water batteries will be within touching distance.
Rainer Klose | Empa - Eidgenössische Materialprüfungs- und Forschungsanstalt
Researchers measure near-perfect performance in low-cost semiconductors
18.03.2019 | Stanford University
Robot arms with the flexibility of an elephant’s trunk
18.03.2019 | Universität des Saarlandes
The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.
A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...
Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.
"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...
New research group at the University of Jena combines theory and experiment to demonstrate for the first time certain physical processes in a quantum vacuum
For most people, a vacuum is an empty space. Quantum physics, on the other hand, assumes that even in this lowest-energy state, particles and antiparticles...
Physicists in the EPic Lab at University of Sussex make crucial development in global race to develop a portable atomic clock
Scientists in the Emergent Photonics Lab (EPic Lab) at the University of Sussex have made a breakthrough to a crucial element of an atomic clock - devices...
Every year earthquakes worldwide claim hundreds or even thousands of lives. Forewarning allows people to head for safety and a matter of seconds could spell...
11.03.2019 | Event News
01.03.2019 | Event News
28.02.2019 | Event News
19.03.2019 | Physics and Astronomy
19.03.2019 | Life Sciences
19.03.2019 | Physics and Astronomy