Dendrites-related fires loom heavily over battery solutions for cars. Have researches at Stanford University in the USA found the answer?
Uncontrolled dendritic lithium growth can cause severe safety issues in lithium-based batteries, such as overheating and sometimes fires. New research has addressed the problems of lithium dendrites formation by using a synergetic effect of two chemicals as additives in the electrolyte. One additive is not sufficient on its own, but adding both chemicals in just the right amounts enables the formation of a stable solid interface between the lithium metal and the electrolyte that helps to stabilize the lithium metal surface, prevent the dendrites growth and protect the lithium metal from degradation.
The addition of lithium nitrate has long been regarded as a way to improve battery performance, whereas lithium polysulfide, formed when a sulfur electrode degrades, can be destructive to a lithium metal electrode. However, the research team at Stanford University looked into the possible effects of a combination of the two and discovered that together they could react with lithium metal to form a stable, solid interface between the electrode and the electrolyte.
“We believe the application is constant,” says researcher Fiona Weiyang Li of the Department of Materials Science and Engineering at Stanford University. “Our research helps to solve the problem of lithium dendrites growth, one of the major barriers holding back the development of the next generation high-energy lithium metal-based batteries, such as lithium-sulfur and lithium-air batteries that can store up to 10 times more energy per weight than current commercialized batteries.”
Deposits forming on the anode of a lithium-metal battery: When lithium nitrate is added to the electrolyte (top) dendrites, grow on the surface, but if lithium polysulfide is also added (bottom), harmless deposits form instead
The researchers are contributors towards a knowledge pool coordinated by the Joint Center for Energy Storage Research (JCESR). “JCESR seeks transformational change in transportation and the electricity grid driven by next generation high performance, low cost electricity storage,” says Li. “Our research on developing lithium metal anode with high capacity fits well with the 5-5-5 goal of JCESR, which is to develop batteries with five times greater energy density, at a fifth of the cost within five years.”
There is a wide interest across various industries in the development of batteries with higher energy densities, lighter weight, and lower cost to power consumer electronics and electric vehicles, so the research will be very welcome. Besides which, lithium metal is likely to have a marketable product of significant scale in a 5-10 year time frame, says Li, adding: “Solving the problems of lithium metal will bring a huge step forward in the commercialization of next generation high-energy lithium-metal based batteries. This will greatly extend the driving distance of electric cars and the battery life of consumer electronics.”
Battery anodes after 100 charging cycles: A combination of lithium nitrate and lithium polysulfide suppresses dendrite growth, (top). However, if only lithium nitrate, is added, dendrites cover the surface (bottom)
So what have been the principal challenges? “The challenges that hinder the practical application of high-capacity lithium metal anode are the lithium dendrites growth and low Coulombic efficiency,” Li explains. “Our breakthrough is that by simply adding two chemicals as additives to the electrolyte, we not only prevent the growth of lithium dendrites, but also achieve high Coulombic efficiency >99% over long-term cycling.”
The research promises considerable advances in the commercialization of the next generation high-energy lithium-metal based batteries. “We are currently developing new methods to further improve the safety and efficiency of lithium metal anode,” reveals Li.
September 1, 2015