Researchers have been edging closer to having their energy storage cake and eating it, too, by merging the attractively powerful charge-discharge rate of supercapacitors with rechargeable lithium battery technology. Here’s an interesting angle from the University of Illinois College of Engineering based on lithium cobalt oxide (LiCoO2), which just released its findings this morning.
The Engineering LiCoO2 experiment is the first to demonstrate that the thermal conductivity (aka heat transfer) properties of LiCoO2 modulate over a wide range, both coming and going, without the need for an extreme high pressure environment. There are potentially many applications, but of course we’re most interested in the implications for energy storage and electric vehicles.
Reversible Thermal Conductivity And LiCoO2
The really big deal about the Engineering study (for those of you keeping score at home, it’s “Electrochemically Tunable Thermal Conductivity of Lithium Cobalt Oxide,” in the journal Nature Communications), is that apparently until now, there was little or no understanding that the thermal conductivity of cathode materials in batteries could change significantly, depending on the battery’s state of charge.
Typically, a material will have either a high or low thermal conductivity. Materials that can modulate back and forth are rare, and prior research only detected small variations.
That’s a key gap in the knowledge chain because the generation and dissipation of heat in rechargeable batteries is a critical factor in their efficiency and durability.
The cathode is the part of the battery that attracts positive charge, and LiCoO2 is a fairly common compound used in cathodes for rechargeable batteries. For its experiment, the Engineering team used time-domain thermoreflectance to measure the thermal conductivity of a thin film of LiCoO2 on a metal-coated electrode in a conventional electrolyte.
The team was able to observe the state of thermal conductivity directly during the lithian (discharge) cycle. Other parts of the study examined both the lithiated and delithiated (discharge) states without the electrolyte.
LiCoO2 could be just the first of many metal oxides that could be analyzed for thermal conductivity using Engineering’s process, since the research team anticipates that its findings will prove to have general application.
We Built This LiCoO2 And Next-Generation EV Batteries!
With a better understanding of the thermal conductivity process, here’s the implications for electric vehicles according to Engineering’s press materials:
A better understanding of the thermal properties of battery electrodes may help in the design of batteries that can be charged more rapidly, deliver more power, and operate with a greater margin of safety, since the heat generated during fast cycling and temperature variations in general are very detrimental to lithium-ion batteries.
What does that mean? For one thing, check out the upcoming inaugural edition of Formula E (yep, that’s E, not 1) racing, which hits ten major cities across the globe this fall. For this first series only, Formula organizers have ruled that the racing teams can switch out their batteries to extend the duration of the race. If not by next fall then certainly in the near future, organizers expect to eliminate the switchout due to range improvements.
We’ve been having quite a discussion over here at CleanTechnica about battery EVs versus fuel cell EVs, so if the research progresses it looks like you can chalk up another one for the BEV side in terms of improving range and power.
It’s still worth noting that due to the still-prevalent use of fossil fuels in the US grid mix, both BEVs and FCEVs are not necessarily “clean” at the far end of the supply chain (yes, we mean you too, natural gas). They are only as clean as their electricity source goes.
However, that situation is quickly tilting in favor of renewable energy, with a major boost from advanced energy storage solutions). Though fossil fuels are still going to play a role in the future (look at how long firewood has lasted, for example), it is going to be a marginal one.
Meanwhile, let’s all give ourselves a nice US-taxpayers pat on the back for chipping in with Engineering’s groundbreaking research, which was supported partly by the Air Force Office of Scientific Research.