Method for testing at least one battery cell stack with regard to the position of battery cell layers
A method for testing a stack of multiple battery cells, each comprising an anode, a cathode, and a separator as types of battery cell layers, wherein the separator is arranged between the anode and the cathode. In a first test step, it is checked whether the edges of the battery cell layers are within a first tolerance range, wherein the battery cells to which this applies are determined to be usable battery cells. Several of the usable battery cells are stacked to the battery cell stack. The battery cell stack is irradiated by X-rays. Via the X-rays, positions of those edges of a type of battery cell layers are determined which delimit at least two of the corners of these battery cell layers, checking whether the greatest distance between the equally located edges of each of the battery cell layers of the selected type is within a second tolerance range.
1 . A method for testing a battery cell stack of at least two battery cells, each of the at least two battery cells comprising an electrode designed as an anode, an electrode designed as a cathode and at least one separator as different types of plate-shaped battery cell layers, the separator being arranged between the electrodes, and each of the different types of plate-shaped battery cell layers having polygonal surface areas of different sizes and each of the different types of plate-shaped battery cell layers are stacked in a direction perpendicular to the surface areas, the method comprising:
determining, in a first test step, the positions of the plate-shaped battery cell layers of each of the at least two battery cells and checking whether edges of the plate-shaped battery cell layers of each of the at least two battery cells are within a first tolerance range, wherein when the plate-shaped battery cell layers of the at least two battery cells are within the first tolerance range, the at least two battery cells are determined to be usable battery cells;
stacking the at least two battery cells determined to be usable battery cells in the first step to make the battery cell stack;
irradiating, in a second test step, the battery cell stack via X-rays emitted by an X-ray emitter and detecting the emitted X-rays via an X-ray detector, the X-rays being directed substantially perpendicular with respect to the surface areas of the plate-shaped battery cell layers; and
determining, via the detected X-rays, the positions of edges that delimit at least two corners of plate-shaped battery cell layers of a selected type of the different types of plate-shaped battery cell layers, and checking whether a greatest distance determined between the edges of all of the plate-shaped battery cell layers of the selected type is within a second tolerance range, wherein when the greatest distance determined between the edges of all of the plate-shaped battery cell layers of the selected type is within the second tolerance range, the battery cell stack is determined to be a usable battery cell stack.
2 . The method according to claim 1 , wherein the plate-shaped battery cell layers are immovably connected to each other.
3 . The method according to claim 1 , wherein the surface areas of the anodes are larger than the surface areas of the cathodes.
4 . The method according to claim 1 , wherein the surface areas of the separators are larger than the surface areas of the cathodes and/or the anodes.
5 . The method according to claim 1 , wherein the anode is the selected type of the plate-shaped battery cell layers, such that the positions of the edges of the anodes are determined.
6 . The method according to claim 1 , wherein the positions of the plate-shaped battery cell layers of each of the at least two battery cells are determined based on an image of an optical camera system.
7 . The method according to claim 6 , wherein the image of the optical camera system is taken in incident light.
8 . The method according to claim 6 , wherein when the image is taken, the cathode is closer to the camera of the optical camera system than the anode.
9 . The method according to claim 1 , wherein the second tolerance range is determined in each case by adjusting a defined output tolerance range based on a distance of the edges determined in the first test step.
10 . The method according to claim 1 , wherein the X-ray detector comprises at least two line detectors arranged substantially perpendicular to each other.
11 . The method according to claim 10 , wherein the battery cell stack is moved relatively at least once in a substantially perpendicular direction by a line detection area of each of the at least two line detectors.
12 . The method according to claim 1 , wherein the usable battery cells are stacked into at least two battery cell stacks, which are simultaneously irradiated by X-rays in the second test step.
13 . The method according to claim 1 , further comprising:
stacking the usable battery cells in a traced order to form the battery cell stack; and
performing the second test step at least twice in different positions of the battery cell stack relative to the X-ray emitter, and by comparing the results of the at least two second test steps, the determined positions of the edges are assigned to the at least two battery cells.