To predict the cyclic stability of secondary battery electrodes, the mechanical behaviors of polymer binders and conductive composites (BCC) is of great significance. In terms of uniaxial tension, tensile stress relaxation, and bonding strength tests, the present study encompasses a systematic investigation of the mechanical properties of two typical aqueous binders with different contents of Super-S carbon black (SS) under a liquid electrolyte. Meanwhile, the microstructure of cured film and the surface morphology of the bonding interface are investigated in detail. When the weight ratio of SS increases from 0% to 50%, the cured BCC films manifest a higher ratio of tensile strength to modulus and a shorter characteristic relaxation time. Moreover, suitable loadings of SS can improve the tensile shear strength and remarkably reduce the percentage of interface failure of aqueous polymer-bonded Cu current collector. Nevertheless, an excess of carbon black amount cannot maintain its enhancing effect and can even impair the adhesive layer. Finally, a sodium alginate-based polymer composite holds much more superior mechanical properties than the mixture of sodium carboxymethyl cellulose and styrene-butadiene rubber at the same content of carbon black. Noticeably, the two kinds of aqueous polymer doped by 50 wt % of SS exhibit the best adhesive properties.
Continuous production of conductive hydrogel fibers has received extensive interests due to their wide application in strain sensors. In this paper, we report on the fabrication of continuous alginate/polyaniline/graphene hydrogel fibers by the in situ polymerization and wet spinning methods. The obtained hydrogel fiber with good flexibility, high water absorbability (11.37 g/g), proper resistivity (220 Ω·m ) and stable resistance changes at both low strain (10%) and high strain (20% and 50%) could be used as a working strain sensor for a wearable human movements monitor. The conductive alginate/polyaniline/graphene hydrogel fiber shows highly sensitive, flexible, and recoverable (90% retention after five cycles) properties when monitoring palm, elbow, and knee movements. This kind of hydrogel with high elasticity and high sensitivity provides a possibility for the preparation of electromechanical sensors.
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.
The secondary flow driven by the primary vortex in a cylinder, generating the so called “tea leaf paradox”, is fundamental for understanding many natural phenomena, industrial applications and scientific researches. In this work, the effect of wettability on the primary vortex and secondary flow is investigated by the three-dimensional multiphase lattice Boltzmann method based on a chemical potential. We find that the surface wettability strongly affects the shape of the primary vortex. With the increase of the contact angle of the cylinder, the sectional plane of the primary vortex gradually changes from a steep valley into a saddle with two raised parts. Because the surface friction is reduced correspondingly, the core of the secondary vortex moves to the centerline of the cylinder and the vortex intensity also increases. The stirring force has stronger effects to enhance the secondary flow and push the vortex up than the surface wettability. Interestingly, a small secondary vortex is discovered near the three-phase contact line when the surface has a moderate wettability, owing to the interaction between the secondary flow and the curved gas/liquid interface.
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