19 Instead, so-called water-soluble binders have been regarded as an alternative binder system, owing to their various interactions with Si particles. However, PVDF would be inappropriate for electrodes in which whole integrity of the electrode is to be maintained by strong interactions with active materials since good wettability of the PVDF binder with organic electrolytes accelerates the loss of their binder–Si adhesive interactions with unwanted side reactions. The polyvinylidene fluoride (PVDF) binder has been widely used in Li-ion batteries due to its electrochemical stability, reasonable binding capability, and facile absorption of the electrolyte. 13- 18 Moreover, the modification of binder has been paid great attention since Si anode can be remarkably stabilized by changing only a small portion of the electrode without further modification of morphology and surface. 5, 6 In order to mitigate these problems, a lot of researches on modification of Si have been conducted in various ways: i) nanomorphological engineering of Si (e.g., nanoparticles, nanowires, hollow structures, porous structure, thin film, etc.), 7- 12 and ii) fabrication of composite materials with carbon-based materials (disordered carbon, carbon nanotube, graphene, etc.). Namely, mechanical fractures on the level of particles, which occur by the volume change of Si (≈300%) during lithiation/delithiation, lead to the mechanical failure of the electrode with the loss of conduction paths, and the formation of additional solid-electrolyte interface (SEI) layers on newly exposed surfaces. 2- 4 However, Si-based electrodes are susceptible to the degradation of capacity, due to the built-up stresses from the inevitable lattice mismatches during a number of two-phase equilibriums. 1 Application of Li-alloy-based materials having inherently high capacities is highly needed, therefore, the silicon is an attractive alternative to the graphite anode in conventional Li-ion batteries due to its high lithium storage capacity (nearly ten times higher than that of graphite). High-energy density with stable cycle-life performance is the prerequisite for Li-ion batteries to be universal power sources for future electronic devices as well as electric vehicles (EVs). The results will provide meaningful insight regarding the design of novel binders, especially in the application of the covalently crosslinked structure to Si-based electrodes. In addition, the effect of the chemical/mechanical properties of PAM gel on the electrochemical properties of Si is adequately elucidated. Through the PAM gel, the Si-based electrode exhibits a superior capacity of ≈1526 mAh g −1 at an optimized crosslinker concentration after 500 cycles. Unlike the thermal crosslinking, the abundant polar-functional groups, related to the strong interactions between Si and polymer, are not sacrificed in their network by virtue of the in situ polymerization. In this respect, the covalently crosslinked polyacrylamide (PAM) network, which effectively maintains its mechanical strength and shape, is introduced as a novel binder system for Si active materials. The molecular/structural design of polymeric binders has been pivotal in overcoming the challenges to improve the integrity of Si anode via strong interactions between active materials and binders. Silicon has been considered as a promising anode material due to its high theoretical capacity (3579 mAh g −1), however, it suffers from capacity degradation owing to the series of multiscale fractures in the electrode caused by the volume variation (≈300%) during phase transitions.
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