UNIVERSITY PARK, Pa. — Despite lithium-ion (Li) batteries' role as one of the most widely used forms of energy storage, they struggle to operate at full power in low temperatures and sometimes even explode at high temperatures. Researchers at Penn State, however, have proposed a design that could hold the key to effective and stable power storage in a variety of climates.
The research, which was published today (Nov. 5) in Joule , investigated a state-of-the-art Li battery design known as an all-climate battery (ACB). Previous design approaches have proven incapable of simultaneously improving efficiency at lower temperatures and increasing stability at higher temperatures — there has always been a tradeoff. Refining and building upon a decade of battery research, the team devised a novel development method that allows ACBs to offer stable and efficient performance over a wide range of temperatures.
According to Chao-Yang Wang , professor of mechanical engineering, of chemical engineering and principal investigator on the project, Li batteries were never intended to operate in the wide range of applications they support today. The devices were originally designed for personal electronics at moderate temperatures, specifically around 25 degrees Celsius (C), or slightly above room temperature.
"Now that these batteries have been integrated into electric vehicles, data centers and large-scale systems that can run very hot, this stable operational temperature has become awkward for manufacturers to work around," Wang said. "To continue enhancing society with the large-scale systems powered by Li batteries, we need to address this fundamental design flaw."
Although external heating or cooling mechanisms are used to help keep the batteries operational today, these bulky, power-intensive systems are inefficient and require frequent maintenance, according to Wang. Even with external temperature management, Li batteries lose performance at cold temperatures and experience reduced capacity and stability at high temperatures — maintaining reliable operation only at external temperatures ranging from -30 to 45 C, which severely limits their implementation into devices stationed in extreme environments, like satellites or solar farms in deserts.
To address this issue, the team improved the traditional battery design used in the previous ACB research, proposing the implementation of a heating element inside an ACB. This novel approach optimizes the materials in battery construction for high stability and safety in hot environments, while using the internal heating to support battery operation in cold environments. According to Wang, this synergy, which is supported by observations made from existing research, will allow researchers to avoid compromising stability and safety in one climate to improve performance in another.
"This is the key aspect of our research — other teams have approached improving performance in both hot and cold environments solely by adjusting the materials used," Wang explained. "By optimizing the materials used for hot temperatures and implementing an internal heater to warm the battery, in turn improving performance at low temperatures, you can address this thermal roadblock."
The researchers will adjust the material makeup of the electrodes and electrolytes in the ACB — the mechanisms that facilitate the movement of electricity internally — to better handle hot environments, with Wang noting how the liquid electrolyte used in traditional Li batteries, while efficient, is simply too volatile to reliably operate at high temperatures. The internal heating structure the team plans to implement is composed of a thin film of nickel foil, only about 10 microns thick — slightly larger than a red blood cell, according to Wang. This structure, which is powered entirely by the battery, will allow the system to self-regulate temperature, while adding virtually no weight or volume to the ACB.
Wang said this synergy will increase the number of environments batteries can reliably operate in, widening their operational temperature range to -50 to 75 C and allowing researchers to implement ACBs into applications that previously proved infeasible for traditional Li batteries. In addition to improved versatility, Wang explained how removing external thermal management systems offers performance benefits.
"By incorporating thermal management into the battery itself, we significantly cut down on both the space the batteries take up, as well as the other variables associated with external heating or cooling," Wang said. "The cost, power consumption and need for maintenance are significantly reduced, which translates to incredible savings in systems like data centers that utilize thousands of Li batteries."
Looking forward, Wang said the team plans to deploy their ACBs. According to Wang, ACBs could be further optimized to operate at temperatures as high as 70 to 85 C with proper development and testing, which will be necessary to support the growing scale of systems that rely on batteries for power storage.
"Our society is only growing more power-dependent, and shows no sign of slowing down," Wang said. "As we continue to develop technology like artificial intelligence data centers or highly advanced drones and electric vehicles that require tons of power, we will have to continue improving the batteries that power them."
Additional members of the research team include Kaiqiang Qin, a postdoctoral student at Penn State, and Nitesh Gupta, a mechanical engineering doctoral candidate at Penn State. This research is supported by the William E. Diefenderfer Endowment.
