Lithium ion batteries are used in everything from cell phones to laptops (chances are you’re reading this article on a lithium-ion powered device!). They are the stand-out energy storage technology for portable electronics. However, to fit our growing needs, we need stronger batteries that can power new applications like fueling long-distance electric vehicles. To do this, new cutting-edge batteries will need energy storage capacities beyond what is currently possible.
Increasing battery energy capacity is a considerable scientific challenge, and the hunt for improved batteries is one of the most active fields of research today. Scientists don their detective hats as they look for breakthroughs, pairing scientific intuition with advanced instrumentation to study exciting new battery materials.
Today, lithium ion batteries are the gold-standard for rechargeable batteries. Their job is to store and release energy through a chemical reaction. Using lithium in the reaction makes it highly reversible. As a result, the battery in your phone can be recharged hundreds of times. Lithium is also a very small atom, so batteries can hoard a wealth of lithium in a small space without weighing much.
Inside each lithium ion battery is a cathode, an anode, and an electrolyte. The anode and cathode work together to house all the lithium atoms in the battery. Different combinations of materials determine how much energy is stored. To make batteries that can store more energy means making new anode and cathode materials that can stockpile more lithium. And to successfully design new ones, scientists need to understand the complex inner workings of these materials with exquisite detail.
Scientists start the design process by experimenting with the atomic structure and composition of the anode and cathode materials. For any new material, they need to figure out how much energy it stores. It’s also crucial to know how the new material is affected by the battery’s energy-storing chemical reaction. That requires quite a bit of scientific sleuthing. Just like a detective carefully inspects every inch of a crime scene, reviews security footage, and interviews eyewitnesses, researchers must conduct an examination to determine changes in the materials after the reaction.
This is tough detective work since researchers will never find eyewitnesses capable of seeing changes at the atomic scale. Fortunately, researchers aren’t stuck using an old-fashioned detective’s magnifying glass—they are armed with a transmission electron microscope, or TEM. The TEM takes images of incredibly tiny things like lithium atoms with ease. This will help researchers get to the bottom of their battery mystery.
Often, researchers use the TEM to examine simplified batteries that mimic the operation of a real battery. With this in-situ approach, scientists can observe atomic scale changes in materials during the battery reaction. By observing the scene in action, they act as their own eyewitnesses.
The in-situ experiment begins when scientists trigger the battery reaction in the TEM. In the process, lithium atoms are transported from the cathode into the anode. As this happens, researchers carefully look for any changes in the atomic composition and structure of the anode and cathode. The researchers also try to see how the lithium atoms move between the cathode and anode, and if the lithium atoms reorganize or cluster in previously unforeseen ways.
These observations can give scientists clear clues to what would happen if they use new materials inside an actual battery. If a new anode or cathode material stores more lithium and improves the battery’s chemical reaction, then researchers have a potential breakthrough on their hands.
Now, sometimes a detective follows every lead and the case still goes cold. This can happen in materials research, too. Frequently, the TEM does not provide enough answers to battery researchers, no matter how powerful in-situ tests might be. This is one reason the research environment is always highly collaborative: many different investigators need to contribute their own pieces of evidence to solve the scientific puzzle.
The investigation into battery materials has been one of the great scientific endeavors of the 21st century. And the mystery of supreme battery design will only deepen as society calls for more advanced energy storage solutions for their portable devices, completely electric vehicles, and beyond.