For many years, scientists have wanted to develop lighter, more compact and safer rechargeable lithium batteries.
If the electrolyte between the positive and negative electrodes of the battery can be replaced by a lighter and thinner solid ceramic material, replacing one of the electrodes with lithium metal may effectively reduce the size and weight of the battery, and also eliminate the safety risks associated with flammable electrolytes.
However, there is an important obstacle on this path, which is the formation of dendrites in lithium batteries, which can accumulate on the lithium surface and penetrate into the electrolyte, leading to a short circuit in the battery, and the principle behind this is not yet clear.
A recent study published in the journal Joule describes the reasons for dendrite formation.
In early research, MIT scientists found that lithium ions traveling back and forth during charging and discharging can cause changes in the volume of the electrode.
This can create stress in the solid electrolyte material.
To deposit this metal, the researchers say, extra mass needs to be added and the volume inevitably increases.
And now the team has found that if the material has tiny defects, the stress can cause cracks to develop, which can lead to the formation of dendrites.
They designed a transparent electrolyte to observe this process and demonstrated that applying pressure can manipulate the formation of dendrites so that the direction of dendrite growth coincides with the direction of the force.
Applying mechanical stress does not prevent dendrite formation, but it does control the direction, which means the scientists can guide the dendrites to stay parallel to the two electrodes to avoid damage to the cell.