Adhesive Polymers as Efficient Binders for High-Capacity Silicon Electrodes

Abstract

The major cause for capacity fading of silicon nanoparticle (SiNP)-based electrodes is the immense pressure applied toward the conductive networks during the charge/discharge process. While numerous efforts have been devoted to investigating different types of polymer binders, the rational design of an adhesive binder with pressure sensitivity has rarely been reported. Herein, a series of pressure-sensitive adhesives (PSAs) synthesized via copolymerization of 2-ethylhexyl acrylate (2-EHA) and acrylic acid (AA) are evaluated as polymer binders for SiNP-based electrodes. The balance between the density of interaction groups and viscoelastic properties is systematically investigated for efficient binding performance. The SiNP-based electrode using PSA with 20 mol % of 2-EHA (Si-PSA-20%) exhibits excellent electrochemical performance, achieving a capacity retention of 83% at the 100th cycle compared with 54% for Si-PAA after activation. Si-PSA-20% also delivers a superior cycling performance at a high current density (1731 mAh g −1 after 350 cycles vs 719 mAh g −1 after 150 cycles for Si-PAA, 1.8 A g −1 ) and at high mass loading of active materials (capacity retention of 74 vs 38% for Si-PAA after 100 cycles, SiNP content ∼1.2 mg cm −2 ). Atomic force microscopy (AFM), peel tests, and Car−Parrinello molecular dynamics (CPMD) simulations are employed to understand their binder performance. The novel design and systematical investigation of PSAs as binders will definitely be appealing for not only the Si electrode but also for other high-energy-density electrode materials.

Challenges and Recent Progress on Silicon‐Based Anode Materials for Next‐Generation Lithium‐Ion Batteries

“…With the development of high‐performance LIBs, the role of binder gradually become main influence factor. [ 51 ] Up to now, apart from polyvinylidene difluoride (PVdF) and carboxymethyl cellulose/styrene butadiene rubber (CMC/SBR), various new polymer binders have been reported, including binding actions of volume change alleviation, [ 52 ] dispersing function, [ 53 ] SEI contribution, [ 54,55 ] electronic conduction, [ 56 ] and ionic conduction [11b,57] …”

Recent Research Progress of Silicon‐Based Anode Materials for Lithium‐Ion Batteries

“…Combining the excellent functions of instruments and equipment with the chemical properties of materials is also one of the ways to expand research ideas. In addition, the design of binders based on SiNP‐based electrodes is also a hot topic of research, and much effort has been made to use SiNPs to create adhesive materials with enhanced adhesion [34–36] . Sukkyun Ahn et al.…”

“…In addition, the design of binders based on SiNP-based electrodes is also a hot topic of research, and much effort has been made to use SiNPs to create adhesive materials with enhanced adhesion. [34][35][36] Sukkyun Ahn et al have systematically investigated the effect of mechanical properties of adhesives on electrochemical properties using a reversible addition-break chain transfer polymerization method. [37] However, these adhesives also have weak hydrogen bond force and poor toughness defects.…”

Commercialization‐Driven Electrodes Design for Lithium Batteries: Basic Guidance, Opportunities, and Perspectives

“…Enhancing the adhesion between active materials, conductive additives, and current collectors to avoid active materials peeling off from the current collector is an effective way to synthesize high mass loading electrodes. [76,196] Binders are usually made up of adhesive polymers, which play an important role in binding active species with conductive additives together and ensures the slurry intimate contact with substrate simultaneously. [197,198] Especially for the high mass loading electrode, the binders should intrinsically be mechanically robust, own high adhesion with tight particle-to-particle junctions, and can provide repaid diffusion pathways for ions/electrons, thereby maintaining the structural integrity without sacrificing the electrochemical performance.…”