Influence of Janus Green and Its Compound Additives on Microstructure and Properties of Electrolytic Copper Foil

LIU Jialiang; LI Yongle; LIAO Jiena; ZHANG Yunpeng; LIU Jun; HUANG Jian; QI Liang; YANG Hongguang; QI Sujie; FAN Xiaowei

doi:10.16490/j.cnki.issn.1001-3660.2026.14.020

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Surface Technology ›› 2026, Vol. 55 ›› Issue (14) : 224-233. DOI: 10.16490/j.cnki.issn.1001-3660.2026.14.020

Functional Surfaces and Technology

Influence of Janus Green and Its Compound Additives on Microstructure and Properties of Electrolytic Copper Foil

LIU Jialiang^1a,1b,2, LI Yongle^1a,1b, LIAO Jiena^1a,1b, ZHANG Yunpeng^1a,1b,2, LIU Jun^1a,1b,2, HUANG Jian^1a,2, QI Liang^1c,2, YANG Hongguang³, QI Sujie³, FAN Xiaowei^1a,1b,2,*

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Abstract

Copper foil is a conductor material for the negative electrode current collector of lithium batteries. Its mechanical properties and surface quality are directly affected by the additives in the electrolyte. A complex additive system containing Janus green is developed. Low-profile lithium battery copper foils are prepared by direct current electroplating, and the tensile strength is enhanced to meet the high mechanical property requirements of lithium batteries. The experiment studies the microstructure of copper foils electrodeposited with Janus green (JGB) through Molecular energy level calculation, LSV, SEM, CLSM, XRD, EBSD analysis and mechanical tensile tests. The depolarization of single JGB transforms into polarization with adding Cl^-, which is manifested by the initial deposition potential shifting from -0.22 V to -0.25 V negatively, and the overpotential increases by 0.03 V. Through density functional theory (DFT) calculation, the LUMO energy level of JGB is mainly distributed on the N atom and the N atom connected to the benzene ring, making these regions the preferred sites for electrophilic reactions. The HOMO energy level is concentrated on the N and C atoms coordinated with Cl^-, indicating that this area is the preferred site for nucleophilic reactions and is prone to preferential adsorption. Due to the small energy level difference ΔE (1.14 eV) of JGB, the electronic structure is more prone to orbital interaction, demonstrating a stronger ability for strong coordination and interface adsorption. It hinders the reduction of Cu²⁺ and thereby suppresses the rapid deposition of copper. Adding 1 mg/L of JGB reduces the surface roughness of the electrodeposition copper foils to as low as 1.25 μm, and the texture T_c with diffraction peaks showing a preferred orientation of the crystal plane (220) is 81.10%. Adding thiourea (TU), the initial deposition potential further shifts negatively to -0.27 V. The overpotential increases by 0.02 V, which is less than the influence of JGB. Because the energy level difference ΔE of TU is as large as 6.02 eV. Meanwhile, the LUMO energy levels of TU are uniformly distributed across the molecule, while the HOMO energy levels are mainly concentrated on the S atom. The sulfur atom in the thiourea molecule has lone pairs of electrons, which preferentially adsorb at the high-energy active sites on the copper deposition surface, inhibiting the rapid growth of the deposited grains. So the added thiourea (TU) molecule which containing —NH₂ and C==S groups, coordinates with Cu²⁺, and generates an electrochemical antagonistic synergistic effect with JGB, and both the additives enhance cathodic polarization. The result is promoting a smooth surface of the deposition, and reducing the roughness. Compared with the large grain size of 0.97 μm in the base solution (VMS) that only contains Cl^-, the electrocrystallization crystal structure of plating solution containing additives transforms into a dense crystal plane (111) with directional growth, and forms a fine-grained strengthening mechanism. Finally, the VMS+Cl^-+JGB+TU system is implemented to obtain high-performance copper foils, which include a roughness of 1.17 μm, a grain size of 0.56 μm, a tensile strength of 607 MPa, and an elongation of 2.1%.

Key words

additive / cathodic polarization / crystal plane orientation / roughness / tensile strength

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LIU Jialiang, LI Yongle, LIAO Jiena, ZHANG Yunpeng, LIU Jun, HUANG Jian, QI Liang, YANG Hongguang, QI Sujie, FAN Xiaowei. Influence of Janus Green and Its Compound Additives on Microstructure and Properties of Electrolytic Copper Foil[J]. Surface Technology. 2026, 55(14): 224-233

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Funding

Key Research and Development project of Jiangxi Province (20244BBG7300, 20244BDD40005, 20252BCE310021); Key Research and Development of Gannan Laboratory (2025GNZD002); Key Research and Development of Jiujiang (ZD2025001437)