Shedding light on battery materials
Understanding why certain materials work better than others when it comes to storing energy is a crucial step towards developing the batteries that will power electronic gadgets, electric vehicles and renewable power grids. Researchers at Drexel University and Delft University of Technology have developed a new technique that can track the electrolytes inside energy storage mechanisms quicky and precisely — a breakthrough that could speed the design of higher performing energy storage devices. This work is now reported in Nature Energy.
Getting a better look
Energy storage devices like batteries contain a cocktail of solvents and electrolyte ions. The movement of the electrolyte ions creates the electric current that enables the battery to power a device. However, the movement of ions is not visible, because they are too small and they move too quickly. The best researchers can do is to rely on the signals that indicate where the ions are likely present — a sort of low-resolution atomic radar, firing particles at them and recording what bounces off.
The team from Philadelphia and Delft created a method to measure and adjust how ions are arranging themselves in the electrodes of a battery, the energy storage compartments of the device. With this method, researchers could design a battery structure that can fit a lot more ions to maximise the area for energy storage inside batteries.
The three most common ways ions assemble at an electrode are within its atomic layers, on its surface, or atop other ions already on its surface. Each of these arrangements has benefits and drawbacks when it comes to performance of energy storage devices such as batteries. Entering into the electrode material’s layers allows more ions — energy — to be stored. Attaching and detaching to the surface of the material enables a quick release of energy. And perching with solvent molecules atop a layer of ions on the surface allows for a slightly larger power discharge but less energy.
Researchers can observe how long and quickly it takes a storage device to discharge and charge again, or test the electrode material at the beginning and end of a discharge cycle, to find out what the predominant storage mechanism is. But recent research suggests that these energy storage mechanisms may not always occur as ordered, separate reactions. There are a number of reactions happening in the device with mixed or intermediate mechanisms. Thus, accurately distinguishing the different mechanisms and fundamentally understanding them is important for improving the performance of energy storage devices.
Being able to precisely keep track of ions within an electrode and track them over the course of its charge-discharge cycles will help researchers to gain a better picture of all the reactions taking place — and, importantly, identify the side reactions that may occur. Armed with this information, designers could better tailor electrode materials and electrolytes to enhance performance and limit their degradation.
A winning combination
The team’s new method offers a way to monitor both the positioning and movement of ions from electrolyte to electrode within an energy storage device. This innovative approach combines two common and well-established procedures: one used to determine the ability of chemical compounds to absorb visible light and another that measures the electrical current of energy storage devices like batteries.
Yury Gogotsi, professor in Drexel’s College of Engineering: “Our method provides an efficient process, using readily available equipment, that can quickly and accurately categorise how materials are interacting with ions in electrochemical systems. Using this to chart our course toward better energy storage materials and devices could help to avoid any number of missteps.”
Source: Drexel University