Hyperbranched β-Cyclodextrin Polymer as an Effective Multidimensional Binder for Silicon Anodes in Lithium Rechargeable Batteries

Abstract

Polymeric binders play an important role in electrochemical performance of high-capacity silicon (Si) anodes that usually suffer from severe capacity fading due to unparalleled volume change of Si during cycling. In an effort to find efficient polymeric binders that could mitigate such capacity fading, herein, we introduce polymerized β-cyclodextrin (β-CDp) binder for Si nanoparticle anodes. Unlike one-dimensional binders, hyperbranched network structure of β-CDp presents multidimensional hydrogen-bonding interactions with Si particles and therefore offers robust contacts between both components. Even the Si nanoparticles that lost the original contacts with the binder during cycling recover within the multidimensional binder network, thus creating a self-healing effect. Utilizing these advantageous features, β-CDp-based Si electrode shows markedly improved cycling performance compared to those of other well-known binder cases, especially when combined with linear polymers at an appropriate ratio to form hybrid binders.

The emerging era of supramolecular polymeric binders in silicon anodes

“…7) provides a good platform to form intimate adhesion with Si surface and preserve the mechanical integrity of the Si electrode, resulting in a stable cycle life. 60 Compared to Alg as a linear polymeric binder, a higher amount of b-CDp remained on the Si surface after washing with water, reflecting the strong adhesion of b-CDp. 1801 peeling test also proved that hyperbranched b-CDp has strong adhesion due to its multidimensional contacts with Si particles.…”

Metal-assisted chemical etching of silicon and the behavior of nanoscale silicon materials as Li-ion battery anodes

“…When examined as a binder for Si anodes, the β-CDp was found to have a self-healing effect where even Si particles that lost contact with the anode could be recovered by the binder. These particles could then contribute to the capacity of the anode again [221].…”

Recent Progress on Polymeric Binders for Silicon Anodes in Lithium-Ion Batteries

“…To improve the interactions between nano-Si particles and a binder, they proposed hyperbranched polymeric binders with an increased number of contacts between the nano-Si particles and the binders, as shown in Fig. 17(a) [40]. A β-CDp binder with a hyperbranched main backbone creates a fractal-like structure-based network in the Si anode; its various bulky side groups are physically entangled with each other via hydrogen bonding and van der Waals force, as displayed in Fig.…”

“…17(b). It was reported that this polymeric network created by the β-CDp binder accommodates a large volume expansion of Si during Li insertion and assists in the recovery of the interactions with Si after it loses contact with the binder at certain points during the Li extraction processs [40]. In addition, a further improvement of the electrochemical performance of Si anodes could be realized with a hybrid of the hyperbranched β-CDp binder and a one-dimensional (D) alginate binder.…”

“…In addition, a further improvement of the electrochemical performance of Si anodes could be realized with a hybrid of the hyperbranched β-CDp binder and a one-dimensional (D) alginate binder. They noted that the introduction of the 1D alginate binder into β-CDp reduces the agglomeration of β-CDp and leads to a more uniformly distributed polymeric network through the neutralization of electrostatic repulsion between the carboxylate groups in 1D alginate by β-CDp [40].…”