3D Meshlike Polyacrylamide Hydrogel as a Novel Binder System via in situ Polymerization for High‐Performance Si‐Based Electrode

Abstract

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. 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. 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. 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. 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. In addition, the effect of the chemical/mechanical properties of PAM gel on the electrochemical properties of Si is adequately elucidated. 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.

Advances of polymer binders for silicon‐based anodes in high energy density lithium‐ion batteries

“…In situ polymerization of crosslinkable monomers can be an effective method to fabricate the crosslinked polymer binders for Si‐based anodes 149‐152 . Liu et al introduced a highly stretchable crosslinked polyacrylamide (PAM) hydrogel binder for Si anodes by in situ free radical polymerization of acrylamide monomer and bifunctional N,N‐methylenebisacrylamide (MBAA) monomer (Figure 15A).…”

Metal‐Coordination Mediated Polyacrylate for High Performance Silicon Microparticle Anode

“…[2,3] The initial Coulombic efficiency (ICE) of electrodes with the PANa 0.8 Fe y binder is the highest (92.3 %) at 1 mol % Fe, and less surface area of Si-MP than Si-NP gives rise to more than 90 % of ICE. [26][27][28][29][30][31][32][33][34][35][36] The cyclic voltammograms of PAA/CB and PANa 0.8 Fe y / CB composites show little sign of side reactions ( Figure S8). Regardless of the Fe 3 + compositions, similar shapes are shown with a reduction of fluoroethylene carbonate (FEC) at 1.5 V (vs. Li/Li + ) during the first scan.…”

“…In the early stage of binder research, Si-nanoparticle (Si-NP) electrode has achieved great enhancement by using polymers with abundant polar functional groups, such as carboxymethyl cellulose (CMC), [24] alginate (Alg), [25] and polyacrylic acid (PAA). [26] The polymer architectures were also modified to improve the adhesion of electrode by branching [27][28][29] or cross-linking via covalent bonds [30][31][32][33] and non-covalent interactions. [34][35][36][37][38] In addition, chemical structure of the polymer has been varied to make a multi-functional binder with acceptable flexibility and electronic conductivity.…”

A Four‐Armed Polyacrylic Acid Homopolymer Binder with Enhanced Performance for SiOx/Graphite Anode

“…Among them, polyacrylic acid (PAA) polymer and its modifications or derivatives have been intensively studied due to its abundant carboxyl groups, water solubility, etc. [ 21–27 ] To further improve the binder performance, binders with the 3D network provided by host–guest chemistry, [ 28,29 ] self‐healing chemistry, [ 30–32 ] grafting chemistry, [ 33–35 ] and cross‐linking chemistry [ 36–40 ] have been introduced since the 3D network can effectively enhance the binding force. For example, Yang and his team innovatively developed a self‐healing multiple‐network binder, consisting of traditional PAA and another soft polymer to reduce the brittleness of PAA, which prominently improved the cycling performance of micro‐Si and SiO x anodes.…”

“…Among them, polyacrylic acid (PAA) polymer and its modifications or derivatives have been intensively studied due to its abundant carboxyl groups, water solubility, etc. [21][22][23][24][25][26][27] To further improve the binder performance, binders with the 3D network provided by host-guest chemistry, [28,29] self-healing chemistry, [30][31][32] grafting chemistry, [33][34][35] and cross-linking chemistry [36][37][38][39][40] have been introduced since the 3D…”