Mechanical Integrity Degradation and Control of All-Solid-State Lithium Battery with Physical Aging Poly (Vinyl Alcohol)-Based Electrolyte

Abstract

Ensuring the material durability of an electrolyte is a prerequisite for the long-term service of all-solid-state batteries (ASSBs). Herein, to investigate the mechanical integrity of a solid polymer electrolyte (SPE) in an ASSB upon electrochemical operation, we have implemented a sequence of quasi-static uniaxial tension and stress relaxation tests on a lithium perchlorate-doped poly (vinyl alcohol) electrolyte, and then discussed the viscoelastic behavior as well as the strength of SPE film during the physical aging process. On this basis, a continuum electrochemical-mechanical model is established to evaluate the stress evolution and mechanical detriment of aging electrolytes in an ASSB at a discharge state. It is found that the measured elastic modulus, yield stress, and characteristic relaxation time boost with the prolonged aging time. Meanwhile, the shape factor for the classical time-decay equation and the tensile rupture strength are independent of the aging history. Accordingly, the momentary relaxation modulus can be predicted in terms of the time–aging time superposition principle. Furthermore, the peak tensile stress in SPE film for the full discharged ASSB will significantly increase as the aging proceeds due to the stiffening of the electrolyte composite. It may result in the structure failure of the cell system. However, this negative effect can be suppressed by the suggested method, which is given by a 2D map under different lithiation rates and relative thicknesses of the electrolyte. These findings can advance the knowledge of SPE degradation and provide insights into reliable all-solid-state electrochemical device applications.

Investigation on the mechanical integrity of a PEO-based polymer electrolyte in all-solid-state lithium batteries

“…The stress in a viscoelastic material is determined by its entire strain history, and its stress–strain relationship can be described using the Riemann–Stieltjes convolution form 20 where and are the spherical strain tensor and the deviatoric strain tensor, respectively, K is the bulk modulus, and Γ ( t ) is the stress relaxation modulus function. Their values can be obtained by performing stress relaxation experiments on the LFP cathode.…”

“…Taking this into account, we have reported the physical aging and viscoelastic behavior of a poly(vinyl alcohol) electrolyte and further investigated its potential impact on the mechanical stability of an in-service cell system. 20 Sultanova et al discussed the effect of the viscoplastic behavior of PEO-based electrolytes on damage at the active particle/SE interface in ASSLBs at ambient temperature using the traction–separation law under the assumption of interfacial contact parameters. 21 Although the above studies and the results are fascinating, it is still important to note that experiments on the adhesion performance of PEO–LiX electrolytes and electrodes have rarely been reported so far.…”