In recent years, there has been a surge in interest surrounding advanced rechargeable batteries that boast high energy density, exceptional performance, and reduced costs. This heightened attention can be attributed to the growing demand for energy storage technologies in the realm of green transportation and large-scale energy storage applications.

The sales of new electric vehicles (EVs) have been steadily increasing, reflecting a shift towards more sustainable modes of transportation. However, there remains significant pressure to enhance battery performance in order to meet the evolving needs of consumers. Presently, electric vehicles offer ranges of approximately 322-483 km, but there is a push for even greater efficiency.

In response to this demand, numerous laboratories worldwide have been conducting innovative experiments and exploring new applications in search of battery chemistry that surpasses the current Lithium-Ion technology used in electric vehicles. These efforts aim to develop batteries that not only outperform existing models but also pave the way for a more sustainable and efficient future in the realm of energy storage.

 

Our research team has spent several years experimenting with various chemical component combinations, exploring new battery technologies, and developing different formulas in order to achieve a cutting-edge battery with superior specifications and performance. The research conducted in our laboratory has resulted in significant enhancements in the form of a highly efficient and high-performance battery, utilizing Lithium and Sulfur as its base components. The Lithium-Sulfur battery shows great promise in meeting the demands of green transportation and large-scale energy storage applications due to its high theoretical capacity, cost-effectiveness, and environmentally friendly characteristics.

The upcoming ExtraLiS project aims to significantly increase the range of electric vehicles while reducing costs. This is made possible by utilizing sulfur, which is more plentiful than cobalt used in current batteries. With traditional transportation being a major source of greenhouse gases, there is an increasing need for more electric vehicles.

Advanced Lithium-Sulfur batteries have the potential to accelerate EV production and adoption. The main goal of this venture is to create long-lasting, high-energy, and cost-effective batteries on a practical scale. Achieving a high utilization rate for sulfur cathodes with reduced electrode thickness and electrolyte amount will be crucial.

Furthermore, advanced characterization techniques will be employed to explore the dispersion process of soluble polysulfide from thick cathodes as well as fundamental reaction mechanisms under electrical fields - expediting Lithium-Sulfur battery technology development. In addition, alternative anode materials are being investigated to address lithium anode concerns. The research team diligently conducts daily tests aimed at identifying both positive and negative aspects of the battery design in order to make necessary improvements towards commercialization.

 

In the conventional Lithium-Ion battery, the movement of Li+ ions occurs between the positive electrode intercalation host, where they are stored during discharge, and the carbon negative electrode, where they are stored during charging up to a maximum capacity. The cell voltages typically range from 3.4 to 3.8 V compared to Li/Li+. Theoretical energy densities, based on electrode materials, reach approximately 500 Wh Kg-1. Consequently, the upcoming Lithium-Sulfur battery holds the potential to enable an extended EV range of 1,000 km.

 

 

The storage mechanism in the new system is fundamentally different from that of a Lithium-Ion battery, as it is based on redox reactions. The positive electrode, sulfur, has a calculated capacity of 1675 mAh g-1, which is achieved through the formation of Li2S when it combines with the negative electrode, lithium. This 2 to 1 ratio overcomes the limitation of lithium storage and offers a promising combination for an ultra-high capacity lithium anode, with a capacity of 3860 mAh g-1. The energy density of the Lithium-Sulfur system is determined by the theoretical capacity of sulfur (1675 mAh g-1) and its potential of 2.15 V versus Li/Li+, resulting in an estimated energy density of around 2,500 Wh kg-1.

Despite the fact that the new technology provides a gravimetric energy density that is up to six times higher than current batteries, it is important to consider the practical implications. Taking into account the significant progress made by our research group and the advancements in this field, it is reasonable to anticipate a four-fold increase in energy density at the battery pack level when it is initially introduced to the market.

The Updated Design Protects Lithium-Sulfur Batteries from Deterioration

The primary obstacle to the widespread adoption of Lithium-Sulfur batteries has been the excessive storage capacity of the sulfur electrode, causing it to succumb to stress and break apart. This progressive breakdown results in damaged electrical connections throughout the electrode, leading to a rapid decline in overall energy performance. However, with this new approach, a conventional binding agent is utilized but processed differently to establish exceptionally robust bonds between the carbon matrix and sulfur particles. These enhanced bonds provide additional room for expansion as the battery charges. Moreover, graphene nanofibers will be incorporated into the design to create space for sulfur particles under heavy cycling loads.

Due to the anticipated reduction in costs, the primary focus currently lies in conducting extensive testing of the new battery in large-scale applications such as electric vehicles and electric grids. It is crucial to emphasize that innovative and environmentally friendly energy storage technologies are urgently required to combat climate change. Prolonged climate change could result in severe consequences not only for ecosystems but also for human lives, making the Lithium-Sulfur system a potentially viable solution.

 

 

The practical energy density of Lithium-Sulfur batteries is typically estimated to range from 200 to 500 Wh/kg. This lower limit falls within the existing values achieved by high-performance battery packs.

In addition to their improved capacity, Lithium-Sulfur cells can operate across all State of Charge (SOC) ranges from 0% to 100%. This presents a valuable chance to utilize the full capacity, whereas Lithium-Ion cells need to maintain a safety margin, limiting their operation window by about 20% of SOC.

Furthermore, our team of scientists has achieved notable advancements in creating a cost-effective battery through a straightforward liquid phase method utilizing active sulfur material and carbon nanofiber. As a result, solid-state batteries can now store higher energy capacities and exhibit enhanced stability. The latest battery, made with the material developed by researchers, has the ability to store more energy in a given volume. This means that the batteries can hold more power without needing to increase in size. Furthermore, these batteries demonstrate improved stability during charging cycles.

Our team of researchers has discovered an exciting breakthrough in battery technology. By utilizing a catholyte with the assistance of carbon's graphene nanofibers, the cycle life of Lithium-Sulfur batteries can be significantly enhanced. In fact, our latest prototype exhibited an impressive 85% capacity retention after 350 cycles of testing.

Encouraging Outcomes

The idea has the potential to reduce the weight of the battery, while also providing quicker charging and improved power capabilities. Currently, researchers are working on a graphene aerogel, a concept that has shown promise and delivered encouraging outcomes. Graphene is a unique form of carbon composed of a single layer of carbon atoms arranged in a hexagonal lattice with one atom at each vertex.

The sponge-like structure of the graphene aerogel is crucial. It absorbs a large amount of the catholyte, enabling high sulfur loading to make the concept worthwhile. This type of semi-liquid catholyte is extremely important as it facilitates seamless cycling of sulfur without any losses. The sulfur does not get lost through dissolution because it is already dissolved in the catholyte solution. Based on recent tests, some of the catholyte solution is also applied to the separator - an internal physical barrier that prevents electrode contact - fulfilling its electrolyte role and maximizing battery sulfur content.

 

 

A new application of graphene could potentially address the limitations of Lithium-Sulfur batteries. Unlike current commercial Lithium-Ion batteries, Lithium-Sulfur batteries boast numerous benefits, such as significantly higher energy density. While top-performing Lithium-Ion batteries typically operate at approximately 300 watt-hours per kg and have a theoretical maximum of around 350, the theoretical energy density of Lithium-Sulfur batteries ranges from about 1000 to 1300 watt-hours per kg – roughly four times greater than that of Lithium-Ion ones.

The ExtraLiS Battery - the Leading Candidate for the Battery of the Future

Solid-state batteries are poised to become a viable alternative to current battery technology, and may even surpass them in the future. The completely solid Lithium-Sulfur material has shown an impressive ability to store energy four times more effectively than traditional batteries. However, the main challenge lies in addressing the insulating nature of sulfur, which needs preparation to facilitate ionized and electron-conducting pathways.

Our researchers have successfully addressed this challenge by employing electrostatic bonding to combine sulfur-active material with carbon nanofiber (CNF) material. This method involves merging substances that would not typically mix within a solution. As a result, they transformed solid sulfur-CNF alloy into Li2S-P2S5-Li, which exhibits electrochemical stability.

New High-Performance Compound

To create high-performance solid Lithium-Sulfur batteries, the right mix of sulfur active material and carbon material is crucial. A new method has been developed recently which involves using low-cost electrostatic adsorption to ensure that sulfur is fully utilized. This method utilizes larger main particles and smaller electrostatic particles that adhere to a surface through polyelectrons, revealing an electrostatic interaction. Once this cost-effective and efficient method proves successful for battery production, it could pave the way for larger capacity devices in the EV industry as well as more advanced electronic devices with diverse features.

 

Chemistry

The Lithium-Sulfur cell undergoes chemical processes such as the dissolution of lithium from the anode surface (and its integration into alkali metal polysulfide salts) during discharge, as well as the deposition of lithium back onto the anode during charging.

 

Anode

At the positive electrode, metallic lithium dissolves and produces electrons and lithium ions during discharge. Electrodeposition takes place during charging. Similar to lithium batteries, this dissolution/electrodeposition reaction can lead to unstable growth of the solid-electrolyte interface (SEI) over time, creating active sites for nucleation and dendritic growth of lithium. The formation of dendrites causes internal short circuits in lithium batteries, ultimately leading to battery failure.

Cathode

In Lithium-Sulfur batteries, energy is stored in the sulfur electrode as S8. When discharged, lithium ions from the electrolyte move to the cathode where sulfur transforms into lithium sulphide (Li2S). The process of reducing sulfur to lithium sulphide involves a complex reaction that forms various lithium polysulphides (Li2Sx, 8 < x < 1) at decreasing chain length. Then during the recharging phase, the sulfur gets reoxidized back to S8.

The final product is not just pure Li2S, but a combination of Li2S2 and Li2S due to the slow reduction kinetics at Li2S. This differs from traditional lithium-ion cells, where the lithium ions are inserted in the anode and cathodes. Each sulfur atom has the capacity to hold two lithium ions. In regular cases, only 0.5–0.7 lithium ions can be accommodated per host atom in lithium-ion batteries. As a result, with Lithium-Sulfur technology we can achieve much higher storage density for lithium. During discharge, polysulfides are successively reduced on the surface of the cathode:

S₈ → Li₂S₈ → Li₂S₆ → Li₂S₄ → Li₂S₃

Upon charging, sulfur polymers develop at the cathode separated by a porous diffusion barrier:

Li₂S → Li₂S₂ → Li₂S₃ → Li₂S₄ → Li₂S₆ → Li₂S₈ → S₈

 

 

The latest electric vehicles currently offer a range of 300 – 450 km, but with the new ExtraLiS batteries, they could potentially extend this to an additional 160 – 300 km per charge.

Currently, the Lithium-Sulfur system has the most potential to rival Lithium-Ion batteries in terms of volumetric energy density (Wh L-1). However, there is even greater promise due to this system's higher gravimetric energy density and its projected lower cost. These factors can significantly impact the mileage range of electric vehicles. Lighter batteries would lead to an increased EV range, while a low-cost lighter battery could enable EV manufacturers to consider new concepts that allocate more space within the car for the battery pack without concerns about cost or weight.

Presently, batteries account for a substantial portion of both total EV costs (ranging from 35% - 50%) and vehicle weight (approximately 25% - 30%). Therefore, it does not make sense economically or practically to incorporate additional heavy and costly batteries into cars. The affordable and lightweight ExtraLiS battery holds great potential to overcome this obstacle if manufacturers are open to exploring innovative car designs. Moreover, researchers need only increase the life span of a Lithium-Sulfur battery up until it meets the required levels for use in EVs.

Once the ExtraLiS battery is ready for commercialization, the patents will be made available for licensing to other participants in the industry.

Due to the abundance of sulfur, future technology advancements in EV batteries are expected to lead to lower production costs and increased energy capacities. Currently, the main challenge lies in extending the lifespan of Lithium-Sulfur batteries as much as possible. This promising battery technology also requires improvements for stabilizing the Li metal anode in order to achieve a 1,500-cycle performance target. Progress is already underway with some positive results achieved thus far, but further exploration of key factors is necessary for significant advancements anticipated soon.

Additionally, our researchers anticipate that once these new batteries complete their use in electric vehicles; there is a high likelihood of repurposing exhausted Lithium-Sulfur batteries for grid applications.

The production of Lithium-Ion batteries for electric vehicles is responsible for almost half of the total environmental impact of the EV manufacturing process. During the use phase, the environmental impact of the EV largely depends on the electricity mix of the country where batteries are used as well as the lifespan of the battery. To reduce the environmental impact, Lithium-Sulfur batteries are being developed as they use sulphur, which is a non-toxic and relatively inexpensive material that is abundantly available on Earth.