Researchers at Shanghai Jiao Tong University (SJTU) have developed a polymer binder—PAA-P(HEA-co-DMA)—for use with silicon microparticle (SiMP) anodes. Its network structure and special self-healing capability not only provides enough mechanical support but also buffers the strain caused by the volume change of SiMPs.
Thus, the cycle stability and rate performance are remarkably improved under high reversible capacity or electrode loading. A paper on their work is published in the journal Joule.
Si has been regarded as the most promising candidate for the next generation of Li-ion batteries (LIBs), because of its high theoretical capacity, abundant natural sources, and low electrochemical potential. Nonetheless, several technical challenges still limit its commercialization. The major problem of Si anodes is their drastic volume changes during deep cycling, which often leads to the severe pulverization, electrical contact loss, unstable solid-electrolyte interphase (SEI), and subsequent poor electrochemical cycling reversibility.
To address the aforementioned stability issue, large numbers of nanostructured Si-based materials from zero- to three-dimensional Si, especially the hierarchical constructions (porous or hollow structures, core-shell, yolk-shell, etc.), have been developed to improve the cycle performance. However, most of the material preparations are too complicated and infeasible to scale up. In addition, these modified nanostructured or porous-structured materials often possess large specific surface area and interparticle resistance, and low tap density. These features usually lead to low initial coulombic efficiency (ICE) and small volumetric capacity, which is unsuitable for practical application.
Si microparticle (SiMP) powder is inexpensive and commercially available. … SiMP is a more promising anode material for practical industrial applications. However, since SiMPs possess a much bigger size change (micrometer-level) and stronger pulverization tendency during cycling as compared with their nanoparticle counterparts (nanometer-level), stabilizing the cycle stability of SiMP electrodes is a tough challenge.
… The aforementioned SiMP-based electrodes mostly adopt the binders that are soluble in organic solvents. In view of the low cost and high safety of water solvent, here we design and easily prepare a water-soluble and rigid-soft modulated polymer binder, poly(acrylic acid)-poly(2-hydroxyethyl acrylate-co-dopamine methacrylate) (denoted PAA-P (HEA-co-DMA) hereafter), which in situ forms self-healing multiple network structures during the electrode preparation. It can accommodate the dramatic volume changes, prevent disintegration of SiMPs and electrodes, and improve the electrode wettability to electrolyte solution, resulting in excellent cycling and rate performances even under high areal capacities.—Xu et al.
The binder has self-healing capability and excellent tensile property. It can buffer the strain caused by the volume change of SiMPs and hinder the pulverization of Silicon particles during cycling.
The SiMP electrode with the binder offers specific capacity is approximately 1850 mAh/g under 5A/g and features exceptional electrochemical reversibility. Moreover, the binder can also be applied to micron SiO₂ negative electrode and can cycle reversibly under high areal capacities of 9 mAh/cm2.
Zhixin Xu, Jun Yang, Tao Zhang, Yanna Nuli, Jiulin Wang, Shin-ichi Hirano (2018) “Silicon Microparticle Anodes with Self-Healing Multiple Network Binder,” Joule doi: 10.1016/j.joule.2018.02.012