Rolandi Ana Clara, Pozo-Gonzalo Cristina, de Meatza Iratxe, Casado Nerea, Forsyth Maria, Mecerreyes David
Institute for Frontier Materials, Deakin University, Melbourne 3125, Australia.
CIDETEC Basque Research and Technology Alliance (BRTA), Paseo Miramon 196, 20014 Donostia-San Sebastian, Spain.
ACS Appl Energy Mater. 2023 Aug 14;6(16):8616-8625. doi: 10.1021/acsaem.3c01662. eCollection 2023 Aug 28.
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 -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 () biopolymers were investigated, with one, two, or three sulfonate groups (SO), 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 binder with 3SO groups (3SO) exhibited the highest discharge capacities, delivering 133.1 mAh g at 3C and 105.0 mAh g at 5C, which was similar to the organic-based PVDF electrode (136.1 and 108.7 mAh g, respectively). Furthermore, 3SO 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 vs 0.3 ± 0.1 N m for PVDF), and reduced charge-transfer resistance. Postmortem analysis unveiled good preservation of the NMC811 particles, while the 1SO and 2SO electrodes showed damaged morphologies.
聚偏氟乙烯（PVDF）是锂离子电池中最常用的阴极电极粘合剂。然而，PVDF是一种含氟化合物，在浆料制备过程中需要有毒的N-甲基-2-吡咯烷酮（NMP）作为溶剂，这使得电极制造过程对环境不友好。在本研究中，我们提出使用角叉菜胶生物聚合物作为高压NMC811阴极的可持续水可加工粘合剂来源。研究了三种类型的角叉菜胶生物聚合物，分别具有一个、两个或三个磺酸根基团（SO₃⁻），即κ-角叉菜胶、ι-角叉菜胶和λ-角叉菜胶。除了角叉菜胶的性质外，本文还报道了阴极配方的优化，该配方是通过使用5 wt%的粘合剂到较低的2 wt%来制备的。还研究了水性浆料的加工以及粘合剂的性质对电极形态和电化学性能的影响。具有3个SO₃⁻基团（3SO₃⁻）的粘合剂表现出最高的放电容量，在3C时为133.1 mAh g，在5C时为105.0 mAh g，这与有机基PVDF电极（分别为136.1和108.7 mAh g）相似。此外，3SO₃⁻在0.5C下循环90次后达到了91%的出色容量保持率，这归因于均匀分散的NMC811和导电碳颗粒、对集流体的优异粘附强度（17.3±0.7 N m，而PVDF为0.3±0.1 N m）以及降低的电荷转移电阻。死后分析表明NMC811颗粒保存良好，而1SO₃⁻和2SO₃⁻电极显示出受损的形态。
