In laboratory tests, the coating significantly extended the battery’s life and prevented the generation of dendrites that cause internal short circuits. Previous coatings have used boron nitride to boost solid state lithum metal battery development.
The Stanford team used an artificial solid-electrolyte interphase (SEI) to provide fast ion transport and conformal protection while reducing the dendrite development. The dynamic single-ion-conductive network (DSN) developed by the team incorporates a tetrahedral aluminium oxide with a soft fluorinated linker that provide ion mobility and electrolyte-blocking.
“We’re addressing the holy grail of lithium metal batteries,” said Zhenan Bao, a professor of chemical engineering. Dendrites had prevented lithium metal batteries from being used in what may be the next generation of electric vehicles. “The capacity of conventional lithium-ion batteries has been developed almost as far as it can go,” said researcher David Mackanic, co-lead author of the study. “So, it’s crucial to develop new kinds of batteries to fulfill the aggressive energy density requirements of modern electronic devices.”
The team from Stanford and SLAC tested their coating on the anode of a standard lithium metal battery, which is where dendrites typically form. This was combined with other commercially available components to create a fully operational battery. After 160 cycles, their lithium metal cells still delivered 85 percent of the power that they did in the first cycle. Current lithium metal cells deliver about 30 percent after that many cycles.
The coating prevents dendrites from forming by creating a network of molecules that deliver charged lithium ions to the electrode uniformly. It prevents unwanted chemical reactions typical for these batteries and also reduces a chemical buildup on the anode. “Our new coating design makes lithium metal batteries stable and promising for further development,” said researcher Zhiao Yu.
The group is now refining their coating design to increase capacity retention and testing cells over more cycles.
“While use in electric vehicles may be the ultimate goal,” said Yi Cui, professor of materials science and engineering