Solvent-Free Lithium-Ion Batteries to High Volumetric Capacity via Carbon Nanotube-Coated Ni-Rich Cathodes

Abstract

Until now, lithium-ion battery production technology relied on a slurry-based process using organic solvents (NMP), which is hazardous and is a major contributor to high cost and energy consumption in battery manufacturing processes. Among many studies to reduce battery costs, the dry electrode process that does not use organic solvents is attracting attention as a rising star. Dry electrode technology is one of the most promising processes for next-generation energy storage systems due to their eco-friendly production and lowering energy costs (US$ kWh−1). However, when nano-sized carbon black (CB) is used in a dry electrode process, electrochemical performance deteriorates due to insufficient conductivity in the electrode due to pin-point contact with the nickel-rich cathode. In addition, when CNTs used in the conventional wet process are applied to a dry electrode process, it is still difficult to prepare a dry electrode that is uniformly distributed within the electrodes due to its very high aggregation properties. Despite having innovative advantages, solvent-free processing remains a challenge due to these critical issues. Here, we fabricated a dry-type electrode by using poly-crystalline Ni-rich cathodes uniformly coated with CNTs (Carbon nanotubes), resulting in higher electrical conductivity than the electrodes prepared with the conventional wet process including carbon black (CB). In addition, as a result of minimizing the amount of PTFE binder in the electrode by eliminating the mixing of existing carbon black (CB), dry electrode manufacturing was enabled without crushing the Ni-rich cathodes even the fabrication of dense cathodes with extremely high active material content (99.7%) and high electrode density (4.0 g cm-3). The CNT-coated dry electrodes show a high Qvol of ~860 mAh cm-3 at a current rate of 0.2 C (~1.0 mA cm-2) compared to the conventional wet-process electrodes (98 wt% Ni-rich cathode; ~3.6 g cm-3). Furthermore, to demonstrate the practical LiBs operation, a 12cm2-sized pouch cell (>60mAh) was fabricated via dry process and exhibited excellent cycle performance (up to 80% after 400 cycles). We believe that this solvent-free lithium-ion battery via carbon nanotube-coated Ni-rich cathodes approach would be feasible and bring a new electrode design paradigm to the lithium-ion battery market. Figure 1