Carrageenans as Sustainable Water-Processable Binders for High-Voltage NMC811 Cathodes

Abstract

Poly(vinylidene fluoride) (PVDF) is the most common binder for cathode electrodes in lithium-ion batteries. However, PVDF is a fluorinated compound and requires toxic N-methyl-2-pyrrolidone (NMP) as a solvent during the slurry preparation, making the electrode fabrication process environmentally unfriendly. In this study, we propose the use of carrageenan biopolymers as a sustainable source of water-processable binders for high-voltage NMC811 cathodes. Three types of carrageenan (Carr) biopolymers were investigated, with one, two, or three sulfonate groups (SO3 –), namely, kappa, iota, and lambda carrageenans, respectively. In addition to the nature of carrageenans, this article also reports the optimization of the cathode formulations, which were prepared by using between 5 wt % of the binder to a lower amount of 2 wt %. Processing of the aqueous slurries and the nature of the binder, in terms of the morphology and electrochemical performance of the electrodes, were also investigated. The Carr binder with 3SO3 – groups (3SO3 – Carr) exhibited the highest discharge capacities, delivering 133.1 mAh g–1 at 3C and 105.0 mAh g–1 at 5C, which was similar to the organic-based PVDF electrode (136.1 and 108.7 mAh g–1, respectively). Furthermore, 3SO3 – Carr reached an outstanding capacity retention of 91% after 90 cycles at 0.5C, which was attributed to a homogeneous NMC811 and a conductive carbon particle dispersion, superior adhesion strength to the current collector (17.3 ± 0.7 N m–1 vs 0.3 ± 0.1 N m–1 for PVDF), and reduced charge-transfer resistance. Postmortem analysis unveiled good preservation of the NMC811 particles, while the 1SO3 – Carr and 2SO3 – Carr electrodes showed damaged morphologies.

Current Trends and Perspectives of Polymers in Batteries

“…However, the water processing of new high-voltage cathodes such as NMC-type materials is still challenging due to their low stability in water. Here, some recent successes have been reported with NMC 811 with the use of ionic polymers such as anionic carrageenan biopolymers or water-soluble phosphate–poly(ionic liquid)s. 17 …”

Recyclable Fluorine‐Free Water‐Borne Binders for High‐Energy Lithium‐Ion Battery Cathodes

“…If directly compared to published research in the field of aqueous cathode binders the presented materials are highly competitive with published capacity retentions of 80% -90% with similar charge rates and cycles. [24][25][26] Thus, the polymer binder P1 is the first time polymers with surfactant-like sidechains are successfully utilized as LIBC binders. The binders are also useable up to 4.3 V versus Li/Li + , which opens up many more use cases, for instance in the wellestablished and less demanding LiFePO 4 cathodes and even in sodium-ion batteries.…”

“…Current research in the field of LIBC binders mostly uses already widely available commercial polymers such as polyacrylic acid, [23,24] numerous biopolymers, [25][26][27][28] or their composites. [29,30] We describe a family of novel purpose-built multifunctional fluorine-free binders based on polymerizable surfactants.…”

Unlocking sustainable power: advances in aqueous processing and water-soluble binders for NMC cathodes in high-voltage Li-ion batteries

“…131 Carrageenan is considered an interesting option as a binder due to its high viscosity, natural availability, low cost, and molecular interactions given by the presence of sulfonate groups that can also enhance lithium diffusion. 132–134…”

“…131 Carrageenan is considered an interesting option as a binder due to its high viscosity, natural availability, low cost, and molecular interactions given by the presence of sulfonate groups that can also enhance lithium diffusion. [132][133][134] 3 Performance of aqueous binders in NMC electrodes: electrochemical performance, rate capability, cycling stability and capacity retention, effects on NMC particle degradation…”