Sliz Rafal, Valikangas Juho, Silva Santos Hellen, Vilmi Pauliina, Rieppo Lassi, Hu Tao, Lassi Ulla, Fabritius Tapio
Optoelectronics and Measurement Techniques Unit, University of Oulu, 90570 Oulu, Finland.
Research Unit of Sustainable Chemistry, University of Oulu, 90570 Oulu, Finland.
ACS Appl Energy Mater. 2022 Apr 25;5(4):4047-4058. doi: 10.1021/acsaem.1c02923. Epub 2022 Mar 29.
-methyl-2-pyrrolidone (NMP) is the most common solvent for manufacturing cathode electrodes in the battery industry; however, it is becoming restricted in several countries due to its negative environmental impact. Taking into account that ∼99% of the solvent used during electrode fabrication is recovered, dimethylformamide (DMF) is a considerable candidate to replace NMP. The lower boiling point and higher ignition temperature of DMF lead to a significant reduction in the energy consumption needed for drying the electrodes and improve the safety of the production process. Additionally, the lower surface tension and viscosity of DMF enable improved current collector wetting and higher concentrations of the solid material in the cathode slurry. To verify the suitability of DMF as a replacement for NMP, we utilized screen printing, a fabrication method that provides roll-to-roll compatibility while allowing controlled deposition and creation of sophisticated patterns. The battery systems utilized NMC (LiNi Mn Co O) chemistry in two configurations: NMC523 and NMC88. The first, well-established NCM523, was used as a reference, while NMC88 was used to demonstrate the potential of the proposed method with high-capacity materials. The cathodes were used to create coin and pouch cell batteries that were cycled 1000 times. The achieved results indicate that DMF can successfully replace NMP in the NMC cathode fabrication process without compromising battery performance. Specifically, both the NMP blade-coated and DMF screen-printed batteries retained 87 and 90% of their capacity after 1000 (1C/1C) cycles for NMC523 and NMC88, respectively. The modeling results of the drying process indicate that utilizing a low-boiling-point solvent (DMF) instead of NMP can reduce the drying energy consumption fourfold, resulting in a more environmentally friendly battery production process.
N-甲基-2-吡咯烷酮（NMP）是电池行业制造阴极电极最常用的溶剂；然而，由于其对环境的负面影响，在一些国家正受到限制。考虑到电极制造过程中约99%使用的溶剂会被回收，二甲基甲酰胺（DMF）是替代NMP的一个相当不错的选择。DMF较低的沸点和较高的着火温度使得电极干燥所需的能耗大幅降低，并提高了生产过程的安全性。此外，DMF较低的表面张力和粘度能够改善集流体的润湿性，并提高阴极浆料中固体材料的浓度。为了验证DMF替代NMP的适用性，我们采用了丝网印刷，这是一种制造方法，它提供了卷对卷的兼容性，同时允许可控沉积并创建复杂的图案。电池系统在两种配置中采用了NMC（LiNi Mn Co O）化学组成：NMC523和NMC88。第一种是成熟的NCM523，用作参考，而NMC88用于展示该方法在高容量材料方面的潜力。这些阴极被用于制造硬币型和软包型电池，并进行了1000次循环。所取得的结果表明，在NMC阴极制造过程中，DMF能够成功替代NMP，且不影响电池性能。具体而言，对于NMC523和NMC88，经过1000次（1C/1C）循环后，NMP刮刀涂布的电池和DMF丝网印刷的电池分别保留了其容量的87%和90%。干燥过程的模拟结果表明，使用低沸点溶剂（DMF）而非NMP可将干燥能耗降低四倍，从而实现更环保的电池生产过程。
