Aluminium-sulfur battery economical, scalable power backup solution for renewable energy sources, demonstrate researchers

With the build-up of large wind and solar power systems, the need for economical, scalable backup solutions to provide power when the wind is calm and the sun is down is growing fast. The lithium-ion batteries currently used are too expensive for most such applications, and alternatives such as pumped hydro requires specific topography that is always not available.

In a new development, researchers at MIT and other institutions have developed a new kind of battery, composed completely from abundant and inexpensive materials, which could serve the purpose.

The new battery architecture is described in a paper in Nature.

The objective was to invent something that was much better than lithium-ion batteries for small-scale static use, and ultimately for automotive use.

Besides high cost, lithium-ion batteries contain a flammable electrolyte, which make them less than ideal for transportation. This led the researchers to study the periodic table, in a bid to find cheap, abundantly available metals to substitute lithium.

In fact, commercially dominant metal, iron, does not have the required electrochemical properties for an efficient battery, stated the lead researcher. But the second-most abundant metal available commercially, which is also the most abundant metal on earth, is aluminium.

The question following this what to pair aluminium with for the other electrode, and what kind of electrolyte to use in between to transport ions to and fro during charging and discharging. Sulfur is the most inexpensive among all non-metals, and thus became the second electrode material.

For the electrolyte, researchers refrained from using volatile, flammable organic liquids that have sometimes led to hazardous fires in cars and other applications of lithium-ion batteries. Some polymers were tried, but, at the end, variety of molten salts were looked at.

Improved thermal instability helps increase safety of lithium-ion batteries, say researchers

Under an umbrella of several national and international projects, researchers from CMT- Motores Termicos at the Univesitat Politecnica de Valencia are working to improve the safety of lithium-ion batteries, which are currently most used in electric vehicles.

The future of the automotive sector to a large extent depends on the massive use of lithium-ion batteries, pointed out one of the researchers. This is despite some current problems that may affect safety, one of them being thermal stability.

In fact, lithium ion batteries are not safe under certain conditions. This is due to the phenomenon of thermal runaway, which can lead the battery to catch fire that further carries risk to the occupants of the vehicle.

Importantly, the thermal energy that is released during the process is approximately 5.4 times the electrical energy contained in the battery, and thus this requires extreme precautions to be taken.

Meanwhile, thermal instability of batteries can occur under high demand conditions, during fast charging for example. If the thermal stability is not managed well, it can go into thermal runaway and initiate a fire. In light of this, a German city has already banned the parking of electric cars in underground garages.

Furthermore, to reduce the risk of thermal instability, the team of researchers are currently working on two national and two European projects. The objective is to better understand the problems associated with thermal runaway of lithium-ion batteries – the ones that are currently used and the ones that will reach the market in future in next 15 years.

In order to understand this, the researchers are applying results of more than 40 years of work undertaken on combustion engines that affects lithium-ion batteries.

Researchers discover new environments to assemble lithium-ion batteries

For the Nobel Prize in Chemistry for 2020, those behind lithium-ion rechargeable batteries bagged the honor. Evidently, lithium-ion rechargeable batteries have become an essential power source for electronic devices that range from small IT devices to electric vehicles.

Meanwhile, Tesla – a leading automaker in the U.S., emphasized the need to set up an innovative production system and reduce battery cost. This is because batteries make up a large portion of cost of electric vehicles, thus, cost reduction of batteries is essential to make electric vehicles popular.

In the interim, a team of researchers at the Department of Chemistry, POSTECH and Ulsan College have successfully developed a multi-functional separator. This does not prevent the batteries from functioning even if the pouch cell is assembled in ambient air.

The findings of the study are published in the online edition of Energy Storage Materials.

In fact, for assembling lithium-ion batteries, a dry room with less than 1% humidity is required. This is because the electrolyte inside the battery acts with moisture to cause decay. Nonetheless, it is costly to maintain a dry room.

Currently used environments expensive for long-term sustainability

Meanwhile, studies have also been conducted to suppress impurities such as hydrofluoric acid or moisture. This involves injecting additives into the electrolytes. However, injecting additives can cause unwanted side reaction during battery operation. In fact, when batteries are operational on high temperatures, even a small speck of moisture causes deterioration of performance at a fast rate. Therefore, this requires a material that is capable of trapping moisture and contaminants in the battery without causing adverse electrochemical reaction on the additives.

To address this, the research team that worked on it jointly introduced functional materials that can catch impurities on the surface of the separator.