New lithium-sulfur battery for electric cars reduces charging time to 12 minutes

Researchers from Germany, India and Taiwan have presented the concept of lithium-sulfur batteries for electric cars, which will reduce the full charging time to less than 30 minutes.

With the global transition to electric transportation, reducing battery charging time remains one of the key challenges for developers and researchers around the world. Modern Li-ion batteries can be charged from 20 to 80% in about 20-30 minutes, but full charging takes much longer. Meanwhile, high-speed charging leads to a shorter battery life.

The study, conducted by researchers from Kiel University and their colleagues from India and Taiwan, suggests that lithium-sulfur batteries can solve the existing problems. The international study led by Dr Mozaffar Abdollahifar provides a detailed description of how lithium-sulfur batteries can overcome the limitations of current Li-ion batteries in terms of performance and charging time.

The scientists relied on an analysis of hundreds of recent studies and developed a kind of roadmap for how lithium-sulfur batteries can reduce charging time. Some of them can be fully charged in about 12 minutes.

The design consists of a sulfur cathode and a lithium-metal anode. Theoretically, this combination should provide a capacity of up to 2600 watt-hours/kg, which is almost 10 times higher than the energy density of lithium-ion cells. 

This will significantly increase the range of electric vehicles. Sulfur is a relatively inexpensive and readily available material compared to cobalt and nickel. However, sulfur conducts electricity poorly and must be combine with materials based on carbon. This, in turn, increases the weight of the battery and complicates the design.

In addition, the sulfur cathode is subject to volume expansion and contraction of up to 80% during charging. This reduces mechanical stability and shortens battery life. 

One of the key problems is the movement of lithium polysulfide intermediates between the cathode and anode, which cause undesirable chemical reactions and lead to a loss of efficiency. Another problem is the formation of dendrites on the lithium-metal anode. These tiny needle-like structures grow larger during repeated charging cycles and can lead to to short circuits, and in some cases — even until the battery lights up. 

According to one of the lead authors of the study Jakob Offerman, preventing the growth of dendrites is key to the safety and reliability of next-generation batteries. The researchers are paying particular attention to cathode design using advanced materials such as graphene, nanotubes, and porous activated carbon structures. 

In addition, catalytic materials such as metal oxides are used, single-atom catalysts to accelerate sulfur conversion reactions and prevent the movement of lithium polysulfide intermediates between the cathode and anode. The researchers also studied advanced separators and highly concentrated electrolytes that would contain the polysulfides and ensure rapid ion exchange. 

Stabilization of the anode remains a priority. Currently, we are testing protective surface coatings and three-dimensional lithium structures that prevent the formation of dendrites and extend battery life.

At the same time, researchers are conducting experiments with new forms of sulfur, in particular, monoclinic gamma sulfur, which is capable of providing a solid-phase reaction almost bypassing the transfer effect. Researchers are using artificial intelligence to better predict and optimize the process of combining a large number of complex materials. 

As Dr According to Mozaffar Abdollahifar, the first prototypes are already reaching an energy density of about 2 mAh/cm². 

The results of the study are published in the journal Advanced Energy Materials

Source: Interesting Engineering