Two highly promising pathways in the pursuit of next-gen battery technology involve using solid-state electrolytes rather than liquid ones, and adding silicon to the anode component to boost energy density. A newly developed architecture places these two innovations within one device to form a solid-state battery that is safe, long-lasting and has the potential to store vast amounts of energy.
For many years, scientists have been allured by the game-changing energy density silicon promises next-generation batteries, but bringing it into the mix has its challenges. The idea is to incorporate or entirely replace the graphite used as the anode with silicon to potentially store as much as 10 times the lithium ions. The trouble is silicon causes the liquid electrolyte to quickly degrade and the battery to quickly fail, but the authors of this new study believe the solution may lie in using a solid-state electrolyte instead.
Like silicon anodes, solid-state electrolytes are another branch of battery research that could open up some exciting possibilities. The conventional liquid electrolyte that carries the lithium ions back and forth between the anode and a battery's other electrode, the cathode, is highly volatile, which limits compatibility with other prospective, high-performance materials such as lithium metal. Solid-state electrolytes shape as a promising solution to this problem.
Engineers at the University of California, San Diego suspected a solid-sate electrolyte might bring some similar advantages to silicon anodes. Efforts to incorporate silicon into the anodes of lithium batteries have been plagued by fluctuations in the size of the silicon particles, which expand and contract as the device charges and discharges. This combines with unstable interactions between the silicon anode and liquid electrolyte to drive severe capacity losses as the battery is cycled.
“As battery researchers, it’s vital to address the root problems in the system," says Shirley Meng, the corresponding author. "For silicon anodes, we know that one of the big issues is the liquid electrolyte interface instability. We needed a totally different approach."
This new approach involved making some tweaks to the way the silicon anode is put together, with the scientists eliminating carbon and binders that are normally used, and opting for a cheaper form of micro-silicon that undergoes less processing. A sulfide-based solid electrolyte was then introduced to carry the charge, and the resulting battery proved extremely stable, by avoiding the damaging interactions at the anode.
The novel silicon all-solid-state battery is described as safe, long-lasting and energy dense. A lab-scale full cell was shown to be capable of 500 charge and discharge cycles while retaining 80 percent of its capacity, demonstrating the stabilizing effects of the new design.
“The solid-state silicon approach overcomes many limitations in conventional batteries," says Darren H. S. Tan, first author and CEO of startup UNGRID Battery, which has licensed the technology. "It presents exciting opportunities for us to meet market demands for higher volumetric energy, lowered costs, and safer batteries especially for grid energy storage."
The research was published in the journal Science, while the video below provides an overview of the breakthrough.
Source: UC San Diego
