Researchers at Stanford University and SLAC National Accelerator Laboratory have found that mechanically compressing solid-state batteries can prevent lithium dendrites from causing short circuits. The findings could help engineers develop reliable batteries with higher energy density, longer lifetimes, and faster charging.
Solid-state batteries replace the liquid electrolyte found in conventional lithium-ion batteries with a solid ceramic material. They could potentially provide twice the energy density of current batteries. However, lithium can accumulate inside tiny defects in the ceramic electrolyte during charging. These deposits form dendrites that can propagate through the material and eventually connect the electrodes, short-circuiting the battery.
Researchers have debated whether dendrites originate at the electrolyte surface or within the material. The Stanford and SLAC team provided direct evidence that dendrites can begin at internal defects, including pores and grain boundary junctions.
To control their growth, the researchers placed a shape-memory alloy ring around the solid electrolyte. Heating the ring to 170°C caused it to shrink and compress the battery. Under this mechanical pressure, dendrites continued to form but grew horizontally rather than vertically toward the electrodes. This redirection prevented immediate short circuits.
The results were striking. Batteries subjected to compression continued operating through thousands of charging cycles despite accumulating numerous internal dendrites. X-ray measurements at SLAC’s Stanford Synchrotron Radiation Lightsource helped researchers examine the internal structures and understand where the dendrites formed.
The findings reveal a close connection between mechanical forces and electrochemical behavior. Engineers could use this knowledge to design batteries that maintain constant compression during operation. Another approach would involve developing solid electrolytes with smoother surfaces, minimal electronic leakage, and fewer internal defects.
The researchers will next investigate interfaces between electrodes and solid electrolytes, seeking to improve contact between materials and move solid-state batteries closer to practical applications.
