Excessive heat, as we know all too well by now, is the enemy of batteries. It speeds the chemical reactions inside them, shortening their operating life as they degrade faster. An abnormally warm battery is also a warning of imminent failure. But scientists at China’s Ningbo Institute of Materials Technology and Engineering (NIMTE) have found a way of turning the tables on battery heat.
Disorder to Order: Rejuvenating Batteries With Heat
NIMTE scientists have developed a zero thermal expansion material, in collaboration with University of Chicago. This new substance facilitates near 100% voltage recovery in lithium-ion batteries, when used as a cathode, according to the research report we link to below.
This could be a significant contribution to the future success of these batteries, which are so essential in electric transportation. Their lithium-rich layered oxide cathodes deliver over 300 milliamp hours per-gram capacity, thanks to their unique oxygen-redox chemistry.
However, and here’s the catch with this remarkable chemistry, lithium-ion batteries are fundamentally unstable”:
- Their unique oxygen-redox chemistry may well deliver 30% more energy density.
- However, this chemistry also triggers asymmetric lattice distortion and voltage decay.
- This combination speeds battery aging, according to the report by the NIMTE scientists.
Turning the Tables on Thermal Expansion
Thermal expansion caused by heat can compromise material performance. The NIMTE scientists found negative thermal expansion behaviour in lithium-rich layered oxide cathode materials. These contracted in the temperature range 150–250°C, leading to structural disorder.
The scientists found a way of turning the tables on battery heat, that we find most interesting. The key lies in regarding structural disorder as a reversible phenomenon, not a lasting defect. When they applied 4 volt pulses to their used zero thermal expansion cathode, the material returned to its original state.
“By tuning reversible oxygen-redox activity,” the lead author of the report explains, “the thermal expansion coefficient can be precisely switched among positive, zero, and negative states.” This sounds like a good idea!
More Information
Battery Internal Resistance and Performance
Lithium-Ion Battery Decline and Reasons For It
Preview Image: Negative And Positive Thermal Expansion
