Environmentally Friendly Water-Based Carbon Slurry with Carboxylated Carbon Nanosheets for Optimizing the Electrode–Collector Interface in Lithium-Ion Batteries

Coating a carbon layer on the surface of the current collector can enhance the performance of lithium-ion batteries by improving the interfacial conductivity and the adhesion of the active material. However, traditional carbon-coated copper foil uses hydrophobic graphite as the conductive material, which has poor dispersion and adhesion to the binder, and the preparation process requires the use of environmentally harmful organic solvents. In this work, carboxylated carbon nanosheets (CCN) are synthesized via a simplified ball-milling method utilizing graphite and dry ice as starting materials, and a water-based carbon slurry is formulated, employing environmentally friendly deionized water as the solvent. By coating the CCN-coated copper foil surface with a commercially proportioned graphite slurry, we fabricate electrodes that exhibit exceptional rate performance and cycle stability. In situ impedance combined with the distribution of relaxation times analysis reveals that the CCN layer between the active material and the copper foil not only ensures a stable and fast conductive connection but also reduces side reactions caused by uneven lithiation. This work provides insights into the rational design of battery structures and the preparation of environmentally friendly carbon slurries.