Researchers at Virginia Tech have demonstrated a green and more sustainable manufacturing method for LIBs in which no hazardous organic solvent is used during electrode manufacturing and recycling. A paper on their work is published in the journal iScience.
The researchers found that the electrodes fabricated via water-based processing demonstrate comparable rate performance and cycle life to the ones from conventional solvent based processing. And utilization of a water-soluble binder enabled recovering the cathode compound from spent electrodes using water, which could be successfully regenerated to deliver comparable electrochemical performance to the original, pristine electrode.
Mass production of LIBs can result in environmental concerns during battery manufacturing and disposal. Conventional LIB electrodes, especially cathodes, are manufactured through a slurry processing method where N-methyl-2- pyrrolidone (NMP) is used as a solvent. In fact, it is estimated that 4.1 million kg per year of NMP is used for depositing the cathode layers for a battery manufacturing plant producing 100,000 packs per year of 60 kW, 10 kWh plug-in hybrid vehicle (PHEV) batteries. Given that the global lithium-ion battery production capability is ~400 GWh, humongous amount of NMP is needed.
NMP is expensive and reprotoxic and has been added to the restricted substances list by the European Commission in 2018. In addition, about 47% of the total process energy in LIB manufacturing is consumed in the electrode drying process for evaporation and recovery of NMP solvent, a quarter of which can be reduced when replacing NMP with water. Another 29% of total energy is consumed by the dry room facility to support slurry mixing and casting operations for moisture and temperature control. Thus, novel electrode manufacturing processes and/or a substitution of NMP need to be developed to reduce the processing cost and energy consumption.—Li et al.
The researchers replaced NMP by water in electrode fabrication and black mass (mixture of carbon black and active material) was separated from the current collector and recovered by dissolving the water-soluble binder in water. The active material was separated from carbon black and relithiated to generate battery grade material.
Excellent electrochemical performance was achieved from the water-based processed electrodes used in this work and comparable performance was obtained from the recycled materials. This methodology provides a green, sustainable process for LIB manufacturing and recycling if some underlying challenges can be resolved.—Li et al.
Jianlin Li, Yingqi Lu, Tairan Yang, Dayang Ge, David L. Wood, III, Zheng Li (2020) “Water-Based Electrode Manufacturing and Direct Recycling of Lithium-Ion Battery Electrodes—A Green and Sustainable Manufacturing System,” iScience doi: 10.1016/j.isci.2020.101081