Liquid-flow batteries, which contribute to large-scale energy storage, are expected to be useful in the pie of renewable energy backup, but there are still some problems to overcome. The good news is that engineers at Stanford University have just created a metal mixture that can be kept liquid at room temperature and used in a new type of liquid-flow battery-characterized by scalability, safety, efficiency, and cheapness. In a liquid-flow battery, the cathode and anode are in fluid form and kept in an external tank so that the battery is pumped when needed. There, the two liquids are separated by membranes;
When charging or releasing energy, they are selectively allowed to exchange electrons.
Left: Stanford Ph. D. PhD Geoff Mcconohy, Antonio Baclig, Andrey Poletayev (photography/mark goled) Liquid-flow battery devices are expected to be the preferred option for future large-scale energy storage, but previously used chemicals are often toxic, expensive and difficult to handle.
To design a new type of liquid-flow battery, the Stanford University team used a unique combination of materials to overcome these problems. First, the fluid used as a battery cathode is replaced with a sodium-potassium alloy.
The mixture is still liquid at room temperature, and the theoretical energy density can reach 10 times times the traditional solution.
On the anode of the battery, the team also tested four different water-based fluids.
Sodium-potassium alloy is a liquid metal at room temperature and can be used in high-pressure liquid-flow batteries. The application of the second new material hides in the membrane inside the battery.
The team used ceramic membranes made of potassium and alumina to allow currents to flow between them while keeping positive and negative fluids separate.
The combination of a new battery anode and membrane produces twice times more voltage than other liquid-flow batteries-which means the battery can have higher energy densities and lower production costs, the report said.
The team developed prototypes that have proven thousands of hours of operational stability.
Research Map-1: Battery principle and voltage introduction
Antonio Baclig, co-author of the paper, said:
New battery technology can meet many different performance indicators, through further work, we are expected to achieve cost, efficiency, size, longevity, security and other aspects of the balance.
In the future, the team could try to regulate the thickness of the film or use a non-aqueous liquid as the anode of the battery, the researchers said.
Study on the stability and compatibility of sodium-potassium-alumina with fig. 2:
