Reducing the overall vehicle weight is an efficient, system-level approach to increase the drive range of electric vehicle, for which structural parts in auto-frame may be replaced by battery modules. Such battery modules must be structurally functional, e.g., energy absorbing, while the battery cells are not necessarily loading–carrying. We designed and tested a butterfly-shaped battery module of prismatic cells, which could self-unfold when subjected to a compressive loading. Angle guides and frictionless joints were employed to facilitate the large deformation. Desired resistance to external loading was offered by additional energy absorption elements. The battery-module behavior and the battery-cell performance were controlled separately. Numerical simulation verified the experimental results.