Matrix and interface microcracking in carbon fiber/polymer structural micro-battery

Abstract

In this paper, the propagation of radial matrix cracks and debond cracks at the coating/matrix interface in unidirectional carbon fiber structural micro-battery composite are studied numerically. The micro battery consists of a solid electrolyte-coated carbon fiber embedded in an electrochemically active polymer matrix. Stress analysis shows that high hoop stress in the matrix during charging may initiate radial matrix cracks at the coating/matrix interface. Several 2-D finite element models of the transverse plane with different arrangements of fibers and other matrix cracks were used to analyze the radial matrix crack growth from the coating/matrix interface of the central fiber in a composite with a square packing of fibers. Energy release rates of radial cracks along two potential propagation paths are calculated under pure electrochemical loading. The presence of a radial matrix crack imposes changes in the stress distribution along the coating/matrix interface, making debonding relevant for consideration. Results for energy release rates show that the debond crack growth is governed by mode II.

Polymer reinforced carbon fiber interfaces for high energy density structural lithium-ion batteries

“…As the carbon bercomposite interfacial structure is critically important for structural composites, the ber-matrix interphase requires chemical or mechanical linkage for the best performance. 56 In the case of a structural battery, the active battery materials coated onto the carbon ber current collector directly make up this interphase region and, in turn, determine the mechanical properties of the composite. Failure occurs at the weakest point in this matrix, which will always be at this interphase region due to the lack of chemical or mechanical binding of the active materials to the carbon ber.…”

Structural Batteries: A Review

“…The matrix shrinkage had instead a positive effect in reducing the possibility of damages in the coating, but it also induced tensile hoop and axial stress that can lead to matrix cracking. In the follow-up work, Xu and Varna [ 100 ] made a detailed numerical analysis of the stress field and crack propagation in unidirectional carbon fiber structural 3D batteries during the lithiation and delithiation phases ( Figure 26 and Figure 27 ). A battery with a capacity ratio of positive- to-negative electrode R PN of 0.92 and a fiber volume fraction of 0.338 was analyzed.…”

“… Stress distribution during discharging: ( a ) radial stress; ( b ) hoop stress; ( c ) axial stress from Xu et al [ 100 ]. …”

Structural battery composites: a review

“…The insertion expansion-induced stresses in the transversely isotropic carbon fibres are calculated through a thermo-mechanical analogy (Xu et al 2018a, 2018b, Xu and Varna 2019, Carlstedt and Asp 2019. Figure 12 shows the stress distributions in the fibre (F), coating (C) and matrix (M) at four instants in time at 1 C-charging in absence of mechanical loads.…”