When oxygen atoms escape, they change the local electronic structure and cause the voltage to fade in a next-generation battery, according to theoreticians at Pacific Northwest National Laboratory and University College London, UK. A lithium, manganese, nickel cathode has a high energy density and charges and releases energy quickly, but it fades too soon for commercial use. The team found the release of oxygen leaves vacancies throughout the structure along with stray electrons. The vacancies promote structural disorder that reduces the energy barrier for lithium ions to leave the cathode and reduces the battery’s voltage, just as seen in earlier experiments.
“Our simulated voltage curves respond like those seen in real experimental situation,” said Dr. Maria Sushko, the materials scientist at PNNL who led the study. “We are modeling the material using a realistic structure with defects and disorder rather than some idealized material.”
Lithium-ion batteries fade, releasing less energy each time the battery is charged. Over time, the battery’s voltage declines to the point that it is no longer viable and has to be replaced, at both an environmental and financial cost. This study answers decades-old questions about the underlying microscopic processes. The team shows how the loss of oxygen atoms and the formation of nickel- and magnesium-rich areas cause fading. This new information assists in the knowledge-based design of longer lasting materials for cell phones, laptop computers, and electric cars.
Read more at: Phys.org