Small material changes could revolutionize electric vehicle batteries
Developing electric vehicle (EV) batteries that charge as quickly as filling up a car with gas is key to accelerating EV adoption.
Researchers at the Idaho National Laboratory have found that high nickel content layered oxide cathode materials, specifically NMC811 (80% nickel, 10% manganese, 10% cobalt), offer improved performance, longer life and faster charging capabilities.
Understanding the properties of these materials is crucial to realizing their potential in the manufacture of high-performance electric vehicle batteries.
This breakthrough could solve one of the biggest challenges in the electric vehicle industry – developing batteries that can be charged in just 10 to 15 minutes.
The need for fast charging
As electric vehicles become more widespread, there is an increasing demand for faster and more convenient charging solutions.
As EV sales soar, the ability to quickly charge a battery remains a significant hurdle.
Extremely fast charging places tremendous stress on battery components, and optimizing electrode chemistry, materials and construction is critical to achieving exceptional performance.
The role of the cathodes
In a lithium-ion battery, ions move through the electrolyte between the cathode and anode to provide electricity.
While researchers are beginning to understand the effects of extremely fast charging on anodes, less is known about the effects on cathodes.
The Idaho National Laboratory (INL) team led by Tanvir Tanim has published a study in Advanced Energy Materials examining how NMC811 cathodes perform under extremely fast charge conditions and how various materials degrade during the process.
The INL-led team evaluated the aging behavior of NMC811 cathodes at various fast charge rates, including conditions equivalent to driving over 200,000 miles.
Using advanced electrochemical techniques and scanning electron microscopy, they analyzed failure mechanisms and observed changes in particle architecture.
Surprisingly, NMC811 showed more subsurface degradation but demonstrated better lifetime compared to NMC532 (50% nickel, 30% manganese, 20% cobalt), the most commonly used cathode material five years ago.
Despite subsurface degradation, NMC811 showed several advantages. The arrangement of the molecules in NMC811 created more accessible pathways for lithium ion movement, resulting in improved cycle life.
NMC811 also exhibited higher electrical and ionic conductivity, which allowed the battery to hold more charge with repeated use.
In addition, NMC811 showed slower impedance growth, indicating lower internal resistance, less heating, and higher cell capacity. Its higher specific energy and electrical conductivity combined with lower cobalt content also make it a cost-effective option.
The research conducted by the INL team, which is shared with the scientific community, battery designers and the automotive industry through the US Department of Energy, is of significant importance to the electric vehicle industry. Some car manufacturers have already started using NMC811 cathodes.
Researchers conclude that NMC811 cathodes hold promise for developing EV batteries that can be charged in just 10 to 15 minutes.
They offer greater flexibility to optimize batteries in terms of energy capacity and power output.
Future research will focus on understanding the influence of grain orientation and architecture on single particle performance.
By studying these factors more deeply, scientists aim to further improve the performance of NMC811 cathodes.
Ultimately, NMC811 has the potential to revolutionize the EV industry by enabling fast charging and improving the overall efficiency and affordability of EV batteries.
Source: KSR.
