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Researchers at Oak Ridge National Laboratory (ORNL) have developed an innovative type of solid-state battery that could double the energy density of electric vehicles.
The range of electric vehicles (EVs), the distance they can travel between charges, has increased significantly over the past decade, falling from 80 miles (129 kilometers) in 2010 to 220 miles (354 kilometers) in 2021.
However, there is a limit to how efficient these devices can be, due to the characteristics of the liquid-electrolyte lithium-ion (Li-ion) batteries currently used in electric vehicles, as well as their weight. As the 2023 Heatmap explains: “Lithium-ion batteries for electric vehicles represent the pinnacle of current technology… But their energy density is still significantly lower than that of gasoline. So achieving a range of hundreds of miles requires a bulky, heavy battery to be installed in the bottom of the car.”
But a recent advance in solid-state batteries, described in a study published May 10 in the journal ASC Energy Letters, could change that.
This is based on storing energy in flexible and durable sheets of solid-state electrodes 30 micrometers thick – about the same thickness as a human hair. If the technology is successfully developed, it could double energy storage, increasing the current maximum energy density of electric vehicle batteries to 500 watt-hours per kilogram, the scientists said in a statement.
Problem with solid state
While solid-state batteries aren’t a new concept, ORNL researchers began laying the groundwork for their creation and use in the 1990s. Over the years, they’ve been used in small devices like pacemakers, RFID tags — like those used to prevent loss in stores — and wearables.
However, when it comes to powering electric vehicles, they have not shown sufficient durability or scalability. In addition, the plastic polymers used in most existing solid-state batteries are less conductive than liquid electrolytes, reducing their efficiency.
Scientists have found a solution to these problems by using a polymer to create a “strong but flexible thin film” that could allow solid-state batteries to achieve significantly higher energy density. This outperforms both the current best solid-state batteries and liquid lithium-ion technology, the scientists say.
The sheets effectively separate the negative and positive electrodes, avoiding short circuits while providing highly conductive pathways for ion movement. Sulfide solid-state electrolytes are also used, which exhibit similar conductivity to the liquid electrolytes used in lithium-ion batteries and therefore provide comparable performance levels.
“We want to minimize the amount of polymer binder because it does not conduct ions,” said lead author Guan Yang, a research scientist at ORNL. “The main function of the binder is to hold the electrolyte particles in the film. Using more binder improves the film quality but reduces the ion conductivity. Conversely, using less binder improves the ion conductivity but reduces the film quality.”
High-performance and safe battery for electric vehicles
The next step for the scientists is to create a device that will allow them to test their findings in a real battery in a lab setting. They will also collaborate with researchers in academia and industry to expand the testing.
The scientists stressed in their statement that if the research leads to a new generation of batteries for electric vehicles, it would not only increase the range that electric vehicles can travel, but also make them safer.
Lithium-ion batteries have volatile characteristics and, although fires are rare, they are extremely toxic and difficult to extinguish. According to the UK’s Institution of Fire Engineers (IFE), an electric vehicle fire releases more than 100 organic chemicals
Sourse: www.livescience.com
