When a battery is used, electrically charged ions travel between electrodes, causing those electrodes to shrink and swell. For some time, researchers have wondered why the electrode materials – which are fairly brittle – don’t crack in the expansion and contraction styles.
Now, a team of researchers from MIT, led by ECS member Yet-Ming Chiang, may have found the answer to this mystery.
This from MIT:
While the electrode materials are normally crystalline, with all their atoms neatly arranged in a regular, repetitive array, when they undergo the charging or discharging process, they are transformed into a disordered, glass-like phase that can accommodate the strain of the dimensional changes.
The research focused on the inner workings of sodium-ion batteries. Those involved in the study believe that this work could affect future battery design and possibly lead to new kinds of actuators.
“We know that brittle compounds like this would normally fracture with less than a one percent volume change,” says Chiang, who won the 2012 ECS Battery Division Technology Award. “So how does this material accommodate such large volume changes? What we found, in a sense, is that the crystal gives up and forms a disordered glass.”
Chiang states that these findings could provide a new tool to develop longer lasting, high-capacity batteries.