Looking to overcome the challenges of liquid lithium-ion batteries, an MIT team has probed the mechanical properties of a sulphide-based solid electrolyte material.
“Batteries with components that are all solid are attractive options for performance and safety, but several challenges remain,” Professor Krystyn Van Vliet says.
The big question regarding the use of such all-solid batteries is what kinds of mechanical stresses might occur within the electrolyte material as the electrodes charges and discharges repeatedly.
In a stiff electrolyte, the dimensional changes can lead to high stresses. If the electrolyte is also brittle, that constant changing of dimensions can lead to cracks that rapidly degrade battery performance, and could even provide channels for dendrites.
Until now, lithium-conducting sulphide’s sensitivity to normal lab air has posed a challenge to measuring its mechanical properties, including fracture toughness.
To circumvent this problem, members of the research team conducted the mechanical testing in a bath of mineral oil, protecting the sample from any chemical interactions with air or moisture.
The team used a fine-tipped probe to poke into the material and monitor its responses, giving a complete picture of its properties.
The researchers found that when subjected to stress, the material could deform, but at sufficiently high stress it would crack.
According to Prof Van Vliet, even though the material turns out to be more brittle than ideal, it may still be possible to design battery systems with that information in mind.