Could plentiful and inexpensive potassium replace lithium in a future generation of batteries? Researchers from Rensselaer Polytechnic Institute have proposed a design for a potassium battery that prevents performance- and durability-destroying metal dendrites from forming.
Scientists in many fields are working around the clock to improve on and replace lithium-ion battery technology. In this case, the researchers are seeking a specific kind of battery holy grail: a metal battery that keeps the recharge-ability and longer life of the lithium compound and graphite anode. In practice, metal batteries can develop the same destructive dendrites that plague some lithium-ion designs.
In addition, simply swapping lithium for potassium doesn’t work; the resulting battery isn’t nearly as good, and for a lithium-ion killer to compete, it will need to be at least nearly as good. As they iterated combinations of materials, these researchers realized they could get high performance by replacing the anode and cathode with potassium. Furthermore, that solution addressed the dendrite problem.
“We demonstrate that the K-metal anode can be coupled with a potassium cobalt oxide cathode to achieve dendrite healing in a practical full-cell device,” the scientists write.
How does dendrite healing work? Well, the potassium content of the battery ends up working in its favor for this job. Typically, dendrites grow and have sharp ends that pierce vital and volatile battery parts, causing chemical leaks or fire risk. Lithium atoms have low surface mobility, meaning the ones that coalesce to form dendrites end up piling into each other, like the drips that form huge icicles on the corner of a house’s roof.
Potassium has higher surface mobility, meaning the atoms accumulate, but then spread themselves out. While the researchers compare it to a pile of snow that’s reduced by the it’s really like any kind of erosion, or the way sand pours into a broad circle that continues to spread. Duller, shallower dendrites don’t pierce the battery and cause fires.
This mechanism is enabled partly by the heat of the battery itself, which makes the potassium battery design kind of a self-healing closed system. The researchers say the heat is just enough that it keeps the surface atoms very mobilized and ready to redistribute, never enough that it will damage the battery or fully melt the potassium.
This isn’t this team’s first exploration of self-healing batteries, nor was that the only research on self-healing technologies in lithium-ion batteries. Many of the fatal flaws in lithium are related to the same dendrite problem. A potassium battery that replaces lithium with something cheaper and more plentiful and is able to heal itself from dendrites is a stable and powerful dream come true.
