Effect of the Chemical and Macromolecular Structure of Polyacrylate Binders on the Cyclability of Silicon-Rich Anodes for Lithium-Ion Batteries
Abstract: The increase in the energy density of lithium-ion batteries requires the development of anode electrodes with a higher capacity than graphite. SiOₓ/graphite composites show promise, but volume changes in SiOₓ during cycling cause mechanical stress, a loss of electronic connectivity, and continuous growth of the solid electrolyte interphase (SEI). In this context, the polymer binder is essential, as it controls the electrode’s shape, cohesion, adhesion, and stability. This thesis investigates the influence of the chemical and macromolecular structure of polyacrylate binders on silicon-rich SiOₓ/graphite anodes. The parameters studied include the acrylic acid/ethyl acrylate (AA/AE) ratio, the incorporation of 2-acrylamido-2-methylpropanesulfonic acid (AMPS), pH, the neutralizing cation, molar mass, and the addition of styrene-butadiene rubber (SBR). The electrodes were characterized by rheology, SEM, resistivity, residual water content analysis, mechanical testing, half-cell cycling, and post-mortem solid-state NMR.
The results show that the carboxylic/carboxylate groups derived from AA are critical for interactions with SiOₓ. The sodium-neutralized 85% AA–15% AE copolymer appears to be the best compromise, with performance close to that of 100% AA, better adhesion, lower water content, and a more robust formulation. Its suitability was confirmed under more application-oriented conditions: high SiOₓ content, calendering, alternative collectors, temperature, pre-upscaling, and exploratory recycling.
Keywords: Lithium-ion batteries, SiOx/graphite electrodes, formulation, polyacrylate binders
Influence of the Chemical and Macromolecular Structure of Polyacrylate Binders on the Cyclability of Silicon-Rich Negative Electrodes for Li-ion Batteries
Abstract: Increasing the energy density of lithium-ion batteries requires negative electrodes with higher capacity than graphite. SiOₓ/graphite composites are promising candidates, but volume changes in SiOₓ during cycling induce mechanical stress, loss of electronic connectivity, and continuous solid-electrolyte interphase (SEI) growth. In this context, the polymer binder is a key component because it governs electrode processing, cohesion, adhesion, and cycling stability. This thesis investigates the influence of the chemical and macromolecular structure of polyacrylate binders on silicon-rich SiOₓ/graphite anodes. The parameters studied include the acrylic acid/ethyl acrylate ratio (AA/AE), incorporation of 2-acrylamido-2-methylpropane sulfonic acid (AMPS), neutralization cation, formulation pH, molar mass, and addition of styrene-butadiene rubber (SBR).
The electrodes were characterized using rheology, SEM-EDX, resistivity measurements, residual water quantification, mechanical testing, half-cell cycling, and post-mortem solid-state NMR. The results show that acrylic acid-derived carboxylic/carboxylate groups are essential for maintaining interactions with SiOₓ particles. Among the investigated compositions, the sodium-neutralized 85%AA-15%AE copolymer provides the best overall balance, with electrochemical performance close to that of 100%AA, improved adhesion, lower residual water content, and better formulation robustness. Its practical relevance was further confirmed under more application-oriented conditions, including higher SiOₓ content, calendering, alternative current collectors, cycling temperature, preliminary scale-up, and exploratory electrode-scrap recycling.
Keywords: lithium-ion batteries, SiOₓ/graphite electrodes, formulation, polyacrylate binders
