It should be pointed out that most of the existing efforts are focused on three-point bending. In our opinion, a more appropriate type of test should be four-point bending, which is also suggested by the ASTM standards , as the battery cell belongs to a composite structure.
Bending tests: three-point or four-point Bending has been extensively studied as an important scenario for the development of flexible batteries or electrodes , , . Various testing and modeling efforts , , , have been made to understand the deformation mechanisms.
Following the ASTM standards, we performed four-point bending simulations on battery cells to determine the testing specifications. The distance between the two static noses D S is 180 mm (24 times of cell thickness), and four different distances between the two loading noses D L are compared.
The volume strain induced during the battery operation leads to additional compressive forces and changes the tension and bending forces. Due to the appearance of bending stress at the winding radii, impairments of the particulate electrode layer and current collector foil composite can occur.
Three-point bending tests were firstly conducted for different pouch battery configurations to obtain force–displacement curves. A finite element model of the pouch battery under the three-point bending was then simulated employing a homogenization technique to reduce the simulation cost and time consumption significantly.
The stress components of an element are obtained from the last frame of the simulation to calculate the pressure and equivalent stress. The ( p, σ) pairs of all the elements in the deformed battery cell are plotted in the same coordinate. Here, we investigate two mechanical responses to evaluate the effectiveness of a battery test.