07 March 2018
Lithium-metal batteries are among the most promising candidates for high-density energy storage technology. However, their potential is tempered with the uncontrolled lithium dendrite growth which results in poor recharging capability and safety hazards.
Used a 3D layer of Polydimethylsiloxane (PDMS), or silicone, as the substrate of lithium metal anode, the Arizona State University said they were able to mitigate dendrite formation.
According to Professor Hanqing Jiang from Arizona State University, these findings have relevance for both lithium-ion and lithium-air batteries, as well as implications for other metal-anode-based batteries.
“Almost all metals used as battery anodes tend to develop dendrites,” explained Prof Jiang. “For example, these findings have implications for zinc, sodium and aluminum batteries as well.
“We already know that tiny tin needles or whiskers can protrude out of tin surfaces under stress, so by analogy we looked at the possibility of stress as a factor in lithium dendrite growth.”
The first round of research involved adding a layer of PDMS to the bottom of battery anode, which resulted in ‘remarkable reductions in dendrite growth’.
According to the team, this is directly related to the fact that stress accumulated inside the lithium metal is relieved by the deformation of the PDMS substrate in the form of wrinkles.
“This is the first time convincing evidence has shown that residual stress plays a key role in the initiation of lithium dendrites,” continued Jiang.
The researchers added that they have also developed a ‘smart’ way to utilise the phenomenon to extend the life of lithium-metal batteries while maintaining their high energy density. This was done by giving PDMS substrate a 3D form with a lot of surface.
“Envision sugar cubes that contain a lot of small internal pores,” explained Jiang. “Inside these cubes, the PDMS forms a continuous network as the substrate, covered by a thin copper layer to conduct electrons. Finally, lithium fills the pores. The PDMS, which serves as a porous, sponge-like layer, relieves the stress and effectively inhibits dendrite growth.
“By synergistically combing with other lithium dendrite suppression methods, such as new electrolyte additives, the finding has broad implications for making lithium-metal batteries a safe, high-density, long-term energy storage solution,” added Professor Ming Tang, a research team member at Rice University. “Potential applications range from personal electronic devices to powering electric cars for exceptionally longer periods to being the back-up electric supply for solar power grids.”