Unlike lithium-ion cylindrical and prismatic cells, which have a rigid metal case, LiPo cells have a flexible, foil-type (polymer laminate) case, so they are relatively unconstrained.

Being lightweight is an advantage when the application requires minimum weight, as in the case of radio controlled aircraft.
However, it has been established that moderate pressure on the stack of layers that compose the cell results in increased capacity retention, because the contact between the components is maximised and delamination and deformation is prevented, which is associated with an increase of cell impedance and degradation.
Unlike lithium-ion cylindrical and prismatic cells, which have a rigid metal case, LiPo cells have a flexible, foil-type (polymer laminate) case, so they are relatively unconstrained. 
Being lightweight is an advantage when the application requires minimum weight, as in the case of radio controlled aircraft. However, it has been established that moderate pressure on the stack of layers that compose the cell results in increased capacity retention, because the contact between the components is maximised and delamination and deformation is prevented, which is associated with an increase of cell impedance and degradation.
Lithium polymer battery