Amphiphilic Bottlebrush Polymeric Binders for High‐Mass‐Loading Cathodes in Lithium‐Ion Batteries

Abstract

high-voltage requirements. [1][2][3][4] However, the advancements of cathode active materials are overshadowed by the slow development of cathode binders, which should not be underestimated in terms of enabling practical cathode sheets. This issue becomes more stringent for the development of high-mass-loading cathode sheets, which have garnered considerable attention as a facile and scalable way to construct high-energy-density Li-ion batteries. [5][6][7] Major challenges facing the high-massloading cathode sheets include nonuniform electron/ion conduction networks in their through-thickness direction, [8][9][10][11][12] insufficient adhesion (between electrode active layers and current collectors) under electrolyte-soaked states, [13][14][15] and dissolution of transition metal (TM) ions from cathode active materials. [8,16,17] Notably, these challenges are closely dependent on cathode binders. Several previous studies on cathode binders have focused on the synthesis and engineering of new materials, with particular attention to replacing polyvinylidene fluoride (PVdF) binders that have been predominantly used in commercial cathodes. For example, gum materials [18,19] such as xanthan and guar gums with hydroxyl groups enhance the structural stability and electrochemical performance of overlithiated layered oxide (OLO) cathodes by chelating the dissolved TM ions. Carboxymethyl cellulose (CMC) exerted a strong binding force on OLO and mitigated the phase transition of OLO during cycling. [20,21] Owing to its hydroxyl groups, lignin enhanced the adhesion between LiNi 0.5 Mn 1.5 O 4 (LNMO) active materials and current collectors, and contributed to the formation of uniform cathode-electrolyte interphase (CEI). [22] In addition to these biomaterials, polyacrylic acid (PAA) [23] and Li-PAA [24] were explored as binders for the OLO and LNMO cathodes, which formed stable CEI layers and suppressed the dissolution of TM ions.However, these cathode binders were only suitable for aqueous slurry-based cathode fabrication processes due to their hydrophilic functional groups. More notably, these aqueous binders were not suitable for moisture-sensitive Ni-rich cathode active materials, which have gained considerable attention for high-energy-density Li-batteries used in long-range electric vehicles. The Ni-rich cathode active materials often undergo structural disruption when exposed to water molecules, [25] thus generating unwanted residual Li compounds such as LiOH and In contrast to noteworthy advancements in cathode active materials for lithium-ion batteries, the development of cathode binders has been relatively slow. This issue is more serious for high-mass-loading cathodes, which are preferentially used as a facile approach to enable high-energy-density Li-ion batteries. Here, amphiphilic bottlebrush polymers (BBPs) are designed as a new class of cathode binder material. Using poly (acrylic acid) (PAA) as a sidechain, BBPs are synthesized through ring-opening metathesis polymerization. The BBPs are amphiphilic in nature...

Solution NMR of Battery Electrolytes: Assessing and Mitigating Spectral Broadening Caused by Transition Metal Dissolution

“…We also note that compounds other than Li 3 PO 4 may be used to complex or chelate dissolved Mn 2+ and reduce its effect on NMR spectra without causing HF consumption. The Mn-chelating abilities of various compounds (typically polymers) have been explored in electrolyte solutions with an aim toward reducing metal dissolution and deposition ,− and may be suitable for use in mitigating peak broadening, as long as 1 H signals from the chelating agent do not overlap with 1 H signals of interest.…”

From macromonomers to bottlebrush copolymers with sequence control: synthesis, properties, and applications

“…As another example of functional additives, it has been recently reported that BBPs can act as a new class of cathode binders. 289 In this case, the amphiphilicity from hydrophobic PNB backbones and hydrophilic PAA sidechains can allow a uniform dispersion of cathode slurries. The prevalence of carboxylic acid groups in PAA sidechains provides a strong adhesion between the active materials and current collectors, leading to high-energy density Li-ion batteries.…”

Microbial-Copolyester-Based Eco-Friendly Binder for Lithium-Ion Battery Electrodes

“…The cycling stability was maintained at a binder content of 1 wt %, which is lower than that of typical batteries (10 wt %), and a high areal loading of 5.2 mA h cm –2 was achieved. This indicates that this binder allows for stable cycling, which is difficult to achieve with previously reported binders . In addition, polymers with electrochemical stability comparable to commercial binders, such as CMC, polyolefin, polyurethane, and polyimide, have been studied as binders.…”

“…This indicates that this binder allows for stable cycling, which is difficult to achieve with previously reported binders. 36 In addition, polymers with electrochemical stability comparable to commercial binders, such as CMC, polyolefin, polyurethane, and polyimide, have been studied as binders.…”