Structural dynamics of lithium-ion cells – Part I: Method, test bench validation and investigation of lithium-ion pouch cells. (December 2019)

• Record Type: Journal Article
• Authors: Berg, Philipp; Soellner, Jonas; Jossen, Andreas
• Is Part Of: Journal of energy storage. Volume 26(2019)
• Publication Date: 2019-12
• Subjects: Lithium-ion cell -- Experimental modal analysis -- Vibration -- Structural dynamics -- Vibration durability -- NVH; BEV battery electric vehicle -- CC constant current -- CC-CV constant current-constant voltage -- CID current interrupt device -- CT computer tomography -- DOF degree of freedom -- DPM driving point measurement -- EMA experimental modal analysis -- FEM finite element model -- FRF frequency response function -- HEV hybrid electric vehicle -- IR infrared -- LSCF least square complex frequency -- LSE least square error -- MD machine direction -- MDOF multi degree of freedom -- MIF mode indicator function -- NMC nickel manganese cobalt -- RMS root mean square -- SDOF single degree of freedom -- SEI solid electrolyte interface -- SNR signal to noise ratio -- SOC state of charge -- SOH state of health -- SUT structure under test -- TD transversal direction -- TM transfer measurement; Energy storage -- Periodicals; Energy storage -- Research -- Periodicals; 621.3126
• DOI: 10.1016/j.est.2019.100916
• Languages: English
• ISSNs: 2352-152X

Abstract

Highlights: A test bench for modal analysis of lithium-ion cells is built and validated. The structural dynamics of pouch cells show high sensitivity to temperature and SOH. The structural dynamics of pouch cells show very low sensitivity to the SOC. Lithium-ion pouch cells show nonlinear stiffness and damping behavior. Interfaces and boundaries inside the cell strongly determine the dynamic behavior. Abstract: The failure mechanisms that govern the durability of lithium-ion cells under vibration loading are inadequately investigated. It is inevitable for effective durability testing to understand what might determine damage and fatigue. Experimental modal analysis is used to unveil the structural dynamics of lithium-ion pouch cells in terms of natural frequencies, damping ratios, and mode shapes. A test bench for free-free testing has been developed and validated and is presented in this work. Sensitivities from cell parameters such as state of charge, state of health and temperature and from excitation amplitude are revealed. Strong sensitivity of the structural response from excitation amplitude due to nonlinear softening and nonlinear damping was found. Significant softening for increasing temperature with a linear regime, most probably due to changes in the visco-elasticity of the separator, was also observed, while the state of charge showed minor sensitivity. In contrast, cyclic aging caused strongly increased stiffness of the cells. The results can be used for finite element model building to accompany vibration durability research with simulations, to define which parameter sensitivities might determine the level of fatigue during vibration testing and to test the impact of high dynamic stress on lithium-ion pouch cells through resonance excitation.