Despite nearly 14 million electric cars being sold globally, battery charging remains a major choke point for mass EV adoption. Despite upgrades like fast charging, most EVs still take 30 minutes to an hour to charge to 80%.
Also, while public charging infrastructure has expanded by 40%, only 35% of chargers globally offer ultrafast capabilities.
This major gap underscores the importance of breakthroughs like sulfur-doped materials, which deliver 80% battery charging in just 9 minutes!
Let’s explore the developments in Sulfur-Doped technology, its challenges, ongoing developments, and its potential impact on the feasibility of EV batteries.
Research Developments in Lithium-Sulfur Batteries
In 2017, researchers from Oxford University, the University of Michigan, and the Army Research Laboratory collaborated to explore the use of solid electrolytes for lithium-sulfur batteries in electric vehicles (EVs).
They focused on how solid electrolytes could enable the use of metallic lithium anodes, which can potentially boost energy density – exceeding 1000 Wh/L.
Challenges
One of the key challenges was how microstructural defects within the solid electrolyte impacted the critical current density (CCD), which defines the maximum tolerable current without causing battery failure.
This is crucial because defects can lead to the propagation of lithium metal, which can harm the battery’s stability and overall performance.
Findings
To address this, the team partnered with Oak Ridge National Laboratory (ORNL). Together, they identified which defects had the most profound impact on CCD. They gained insights into how defects influence the battery’s safety and efficiency.
Promising Results and Future Goals
- The research revealed that controlling microstructural defects is necessary to integrate solid electrolytes into lithium-sulfur batteries for EVs.
- The team is working towards achieving a CCD greater than 1 mA/cm², making the technology viable for practical use in electric vehicles.
- The research findings show promise for solid-state batteries, leading to safer and more efficient lithium-sulfur battery technology in the EV industry.
How Sulfur-Doping Reduces Battery Charging Times
Sulfur-doping is a key advancement in enhancing EV battery performance, particularly in reducing charging times.
Researchers in China and California developed this technology in 2024 by applying “heteroatom-doping” during an electrocatalysis process. This technique allows sulfur-doped materials to reduce EV battery charging times.
When sulfur is added to the battery materials, it modifies the electrode structure, enhancing its conductivity.
This structural adjustment allows electrons and lithium ions to move quickly through the battery, dramatically lowering internal resistance and accelerating the battery charging process.
Some key benefits of sulfur-doped materials include:
- Faster energy storage and release: Sulfur-doping creates pathways for ions to travel, facilitating energy transfer.
- Enhanced battery charging speed: The improved ion flow boosts the overall performance of the battery.
- Increased durability: Sulfur-doped electrodes reduce wear, extending battery life and stability.
Sulfur-Doped Cell vs Tesla’s Panasonic 21700 Cell
Compared to standard lithium-ion batteries, such as Tesla’s Panasonic 21700 cell, which offers an energy density of 253Wh/kg and takes 25 minutes to charge to 80%, sulfur-doped batteries demonstrate clear improvements.
A sulfur-doped phosphorus anode coupled with a lithium cobalt oxide cathode enables the battery to achieve an energy density of 302Wh/kg while reducing charging time to 80% in just 9 minutes.
Despite these improvements, some technical challenges, such as the shuttle effect, still need to be addressed in lithium-sulfur batteries.
Addressing the Shuttle Effect in Lithium-Sulfur Batteries
The S-doped mesoporous graphene (SMG) modified separator improves lithium-sulfur battery performance by tackling the “shuttle effect,” a major issue that lowers battery efficiency.
The shuttle effect occurs when lithium polysulfides migrate between the electrodes, leading to capacity loss.
SMG Production via Chemical Vapor Deposition (CVD)
The Chinese researchers produced SMG using the Chemical Vapor Deposition (CVD) method. They prepared a silica substrate and introduced sulfur and carbon-containing gases into the CVD chamber.
High-Temperature Gas Decomposition
At high temperatures in the CVD chamber, the gases decomposed, allowing carbon atoms to form graphene layers on the silica template. Simultaneously, sulfur atoms were incorporated into the graphene’s structure, resulting in sulfur-doped graphene.
Creation of Mesoporous Structure
After deposition, the silica template was removed, leaving behind mesoporous sulfur-doped graphene. This process provided the graphene with a mesoporous structure and a high specific surface area.
Improving Battery Performance with High Surface Area
The high surface area and mesoporous structure of SMG offer numerous sites for physical and chemical adsorption, making it effective at stabilizing lithium-sulfur battery reactions. This enhancement helps improve battery stability and efficiency.
Companies Exploring Sulfur-Doped Technology
Many organizations are using sulfur-doping technology to overcome current battery limitations and unlock the next level of EV battery performance.
Here are some of the key players driving innovation in this space:
Lyten
Lyten, a California-based startup, raised $200 million in a Series B round and opened an automated pilot plant in San Jose, California, in 2023 to accelerate the production of lithium-sulfur batteries.
The company aims to start shipping these batteries commercially by 2024 and plans to scale up manufacturing in the US.
“Lyten’s lithium-sulfur battery… could drive mass-market EV adoption globally and help reduce vehicle weight… it is crucial for reaching carbon net zero goals.”
-Carlos Tavares, CEO of Stellantis, an auto manufacturer, and partner of Lyten
Chrysler
Chrysler introduced its concept car, the Chrysler Halcyon, featuring an 800-volt lithium-sulfur battery. It is estimated to have a 60% lower carbon footprint than the current leading EV batteries.
The battery enables the car to charge at a rate of 40 miles per minute using fast charging technology.
The concept also integrates Dynamic Wireless Power Transfer Capability, allowing the vehicle to recharge on equipped roads, further showcasing advancements in EV battery charging technology.
Tesla and other electric vehicle manufacturers are reportedly considering sulfur-doping technology to enhance EV battery performance. As this technology gains momentum, Lyten is already making notable progress.
Lyten’s Progress with Lithium-Sulfur Technology: A Case Study
Originally, lithium-sulfur batteries were not expected to be commercially viable until the 2030s due to material science challenges. However, Lyten has accelerated this timeline by using its innovative 3D Graphene material to create a sulfur-graphene composite cathode.
High Energy Density
Lyten’s lithium-sulfur technology aims to deliver twice the energy density compared to traditional lithium-ion batteries. According to Lyten’s CEO, Dan Cook, lithium-sulfur is “critical to establishing energy security and supply chain independence.”
Supply Chain Independence
Lithium-sulfur batteries can be sourced locally in the US, avoiding reliance on offshore resources.
Additionally, the US Government of Energy granted $4 million to accelerate the commercialization of sulfur-doped materials for EVs following the passage of the National Defense Authorization Act.
This law, effective in 2027, prohibits the U.S. Department of Defense from purchasing batteries from Chinese manufacturers.
Collaborations
Under the grant, Lyten is collaborating with Arcadium Lithium and top research universities, including Stanford University and the University of Texas-Austin, to accelerate the development of sulfur-graphene composite cathodes.
Final Note
While sulfur-doping results are lab-based, they have strong potential for real-world applications in EV battery charging. Sulfur is the fifth most common element on Earth and could reduce raw material costs. However, challenges do remain.
Lithium-sulfur batteries are recognized as a credible alternative to today’s lithium-ion cells. However, they require “years of steady work on the technology to create successful products, scalable manufacturing, and commercialization.”
– Haresh Kamath, director of energy storage at the Electric Power Research Institute (EPRI)
Developers must address key issues, such as the lower cell voltage and poor life cycle performance of lithium-sulfur cells, along with the unique safety considerations they present.
These factors complicate the transition from lab research to real-world applications. A systematic approach is vital for tackling these challenges and ensuring successful implementation.