Of course it will happen if it is bent too much. The positive and negative electrodes in the polymer lithium battery are separated by a thin layer of polymer material. The pore size of the separator only allows lithium ions to pass through. If it is bent too much, the separator will be damaged. Cracks or enlarged pores will cause the capacity to be greatly reduced or even the battery to be short-circuited. You know the consequences of short circuit. I make lithium batteries.