The price of lithium-ion batteries has been increasing constantly since 2020. The price of lithium alone has skyrocketed by about 500% in the last year. Other minerals used in Li-ion batteries have also become expensive, and many energy experts suggest that the price of such batteries is likely to rise in the coming years as well. Therefore, Li-ion batteries may no longer be a suitable choice for medium and large-scale energy backup systems that store renewable energy.

An international team of researchers has come up with an alternative to Li-ion technology. They claim to have developed a budget-friendly battery system from aluminum and sulfur. Both are abundantly available on Earth. In fact, aluminum ranks second in terms of market availability and first among the most abundant metals in our planet’s crust. Moreover, as compared to lithium-ion batteries, the new batteries could prove to be a more feasible choice for powering homes and businesses.   

Although lithium-ion batteries are currently the most popular energy storage systems on the planet — powering almost everything ranging from smartphones to smoke detectors and electric vehicles (EVs) — due to their high cost and limited supply, the new battery system has a good chance to replace Li-ion in some industries, according to the researchers.

The merits of aluminum-sulfur batteries

A battery system contains electrodes (cathodes and anodes, the former is the positive end and the latter is the negatively charged end) and an electrolyte (a conductive medium that allows the exchange of ions for the purpose of charging and discharging between the two ends). The new battery system is composed of molten chloro-aluminate salt as the electrolyte, and sulfur and aluminum as electrodes. 

The researchers decided to go with these chemical elements because they form a cheap and easily available battery cell combination. They also claim that as compared to Li-ion batteries which come with a flammable electrolyte, aluminum-sulfur batteries could prove to be much safer. Since the electrolyte used in the new batteries has a low melting point, it is better equipped to prevent any battery-fire incidents and short-circuits resulting from the natural accumulation of dendrites, metallic spikes that often get formed on electrodes in Li-ion batteries during charging and discharging.

The proposed battery architecture could be useful for energy storage and backup system for homes, medium-scale businesses, and EV charging stations. Explaining this further, one of the authors of the study and professor emeritus of materials chemistry at MIT, Donald Sadoway said in a statement:

“When electric vehicles become common enough on the roads that several cars want to charge up at once, as happens today with gasoline fuel pumps, if you try to do that with batteries and you want rapid charging, the amperages are just so high that we don’t have that amount of amperage (maximum electric current that can safely run through a system) in the line that feeds the facility.” He further added, “So having a battery system such as this to store power and then release it quickly when needed could eliminate the need for installing expensive new power lines to serve these chargers.”

The new battery system also performed well in charging stress tests, retaining its performance through hundreds of charging cycles. Bearing this in mind, the cost per cell of an aluminum-sulfur battery could be about 83% less than a lithium battery cell. These tests also showed that aluminum-sulfur battery cells could be charged in a bit over a minute with a capacity per weight equal to that of conventional Li-ion batteries. When charged in just six minutes, the charge capacity was 25% higher than Li-ion.

But is this a miracle product? Far from it. Its most important limitation is that it needs 90° C, which is almost the boiling point of water, to operate. As such, aluminum-sulfur batteries require special insulation and anticorrosion measures.

Limitations and future of the new battery architecture

Currently, the proposed battery system can easily meet the energy storage demands of activities that require tens of kilowatt-hours of power as backup. However, the technology is not yet powerful enough to support megawatt-scale energy needs. Professor Sadoway has co-founded a company called Ambri to bring this exciting technology into the market. 

Currently, the researchers are planning to conduct more tests to further check the scalability and stress endurance of the aluminum-sulfur battery system.

The study is published in the journal Nature.