Rational Design of a Multifunctional Binder for High-Capacity Silicon-Based Anodes

Abstract

Although several principles have been recognized to fabricate a nominal "better" binder, there continues to be a lack of a rational design and synthesis approach that would meet the robust criteria required for silicon (Si) anodes. Herein, we report a synthetic polymer binder, i.e., catechol-functionalized chitosan cross-linked by glutaraldehyde (CS-CG+GA), that serves dual functionalities: (a) wetness-resistant adhesion capability via catechol grafting and (b) mechanical robustness via in situ formation of a three-dimensional (3D) network. A SiNP-based anode with a designed functional polymer network (CS-CG10%+6%GA) exhibits a capacity retention of 91.5% after 100 cycles (2144 ± 14 mAh/g). Properties that are traditionally considered to be advantageous, including stronger adhesion strength and higher mechanical robustness, do not always improve the binder performance. A clear relationship between these properties and ultimate electrochemical performance is established by assessing the rheological behavior, mechanical property, adhesion force, peel stress, morphology evolution, and semiquantitative evaluation. This study provides a clear path for the rational design of high-performance functional polymer binders for not only Si-based electrodes but also other types of alloy and conversion-based electrodes.

Room‐Temperature Crosslinkable Natural Polymer Binder for High‐Rate and Stable Silicon Anodes

“…As expected, the higher concentration of the solution featured much stiffer property with only 0.3% of the difference in the concentration, which suggests the formation of large amounts of boronic ester bonds and accordingly is suited for properly investigating the effect of the BC‐derived crosslinking on the structural stability of Si electrodes. Besides, in the battery system, particularly for the Si anodes, typical covalent crosslinking binders (e.g., PAA/CMC, chitosan/citric acid, polyvinyl alcohol/polyethyleneimine, and catechol‐functionalized chitosan crosslinked by glutaraldehyde) enhance the electrode stability to a certain extent but eventually ruptured because it cannot be recovered upon the severe stress from large expansion of Si. The reversibility of such a strong covalent network like a dynamic covalent bonding prevents the delamination of Si particles from the current collectors or electrical isolation of Si particles.…”

Silicon Anodes for High‐Performance Storage Devices: Structural Design, Material Compounding, Advances in Electrolytes and Binders

“…Polyvinylpyrrolidone (PVP) and polyacrylonitrile (PAN) blend polymers and high‐stretching polyacrylamide (c‐PAM) binders all have excellent adhesion to silicon anodes (reversible capacity of 2736 mAh g −1 after 600 cycles at a current density of 3 A g −1 and 753 mAh g −1 at current density of 0.2 C) . Conjugated polymers comprising of cyclopentadithiophene and dimethyl terephthalate or terephthalic acid, the graft copolymer GC‐g‐LiPAA with GC as backbone and LiPAA as side chains or catechol‐functionalized chitosan cross‐linked by glutaraldehyde (CS‐CG+GA) both have high mechanical strength and adhesion, and they show extremely great potential in silicon‐based lithium‐ion battery applications . In addition, a new type of stretchable conductive adhesive (CG) polymer binder which is used as a binder for Si‐CG anodes and with extremely high reversible capacity (after 700 cycles at a current density of 840 mA g −1 , a large reversible capacity remains at 1500 mAh g −1 ) .…”

Highly Energy‐Dissipative, Fast Self‐Healing Binder for Stable Si Anode in Lithium‐Ion Batteries

“…reported a cross‐linked catechol‐functionalized chitosan network binder to balance the stress relaxation and the polymer stiffness for the optimized electrochemical performance. [ 13 ] Hirano et al. designed a multiple network binder [ 10 ] which resembles a spring model to accommodate the dramatic volume change of SiMPs, achieving the cycle stability and rate performance under high areal capacities.…”