Investigation of the mechanical behaviour of lithium-ion batteries by an indentation technique

• Indentation tests on Lithium-ion battery components to evaluate their elastic and plastic behaviour individually.
• Micro-tensile test were performed to verify the obtained plastic behaviour by indentation.
• The elastic modulus of the components was evaluated by analyzing the indentation results considering substrate effect.
• An optimization approach has been followed to obtain representative stress–strain curves.

Indentation is an alternative technique for the measurement of a material׳s elastoplastic properties. It can be used when the classical tensile test approach is not feasible (thin film, very small components, etc.). This paper presents the results of experiments in which this technique has been exploited to investigate the mechanical properties of the multi-layered structure of lithium-ion batteries with the aim of gaining a better understanding of their mechanical integrity. Indentation tests were performed separately on different layers of a lithium-ion battery using a Berkovich indenter. In order to perform the tests, fused silica substrate (which has well-known mechanical properties) was used to constrain the samples. The elasticity of the anode and the current collectors were obtained from the unloading curve of the measured indentation load–displacement data. Also, the individual stress–strain curves were calculated through reverse engineering of the loading curve. A commercial finite element software (ABAQUS) was used to perform numerical simulations comprising axisymmetric elements representing the Al and Cu foil current collectors. Micro-tensile tests were also carried out on these foils. Agreement was obtained between the outcomes of the micro-tensile and the results of the reverse engineering of the indentation tests. A micro-structure analysis was also performed to give an insight into the structure of the battery components which is necessary for small scale mechanical characterization.