Ultra-thin lithium offers a solid platform for high-capacity batteries
Scientists in South Korea have made a breakthrough in battery research that could help us bust through a key bottleneck in energy storage. The team's advance overcomes a technical issue that has held back highly promising lithium-metal battery architecture and could pave the way for batteries with as much as 10 times the capacity of today's devices.
The reason lithium-metal batteries hold so much promise is because of the excellent energy density of pure lithium metal. Scientists hope to swap out the graphite used for the anode in today's lithium batteries for this "dream material," though this comes with some complicated problems to solve.
One of the key issues relates to needle-like structures called dendrites, which form on the anode surface as the battery is charged. These penetrate the barrier between the anode and the battery's other electrode, the cathode, and quickly cause the battery to short-circuit, fail, or even catch fire.
Much research in this area therefore centers on preventing the formation of dendrites, and we've seen some promising and creative solutions. Many of these focus on the formation of a protective interface between the anode and the battery's electrolyte, which carries the charge back and forth between the electrodes as it cycles. A "battery butter," special additives or even batteries that build their own protective layers are a few notable examples.
"Lithium dendrite formation is strongly dependent on the surface nature of lithium anodes," says study author Professor Yong Min Lee from South Korea's Daegu Gyeongbuk Institute of Science and Technology (DGIST). "A crucial strategy for LMBs (lithium-metal batteries), therefore, is to build an efficient solid-electrolyte interface (SEI) at the lithium surface."
Lee and his colleagues have approached this problem by using lithium metal powder as a starting point, which creates a higher surface area and enables the creation of thin and wide electrodes. One shortcoming of this technique, however, has been the uneven nature of the surface, which again leads the battery to failure.
The solution, the DGIST scientists have found, may lie in the addition of lithium nitrate. Pre-planting the compound during the fabrication process allowed the team to create ultra-thin lithium-metal anodes with a smooth and uniform interface layer on the surface. This proved to keep the battery stable over 450 charging cycles, in which it retained 87 percent of its capacity and exhibited a coulombic efficiency of 96 percent.
"We expect that pre-planting lithium stabilized additives into the LMP electrode would be a stepping-stone towards the commercialization of large-scale lithium-metal, lithium-sulfur, and lithium-air batteries with high specific energy and long cycle life," says Lee.
The research was published in the journal Advanced Energy Materials.