Isotropic Structure and Polymer Interface Intensified Lithium-Ion Transmission in Spherical Graphite Tailings/Coke Composite Anode

Abstract

Spherical graphite tailings (SGT) as the anode electrode for a lithium-ion battery not only improves the utilization value of SGT as solid waste, but also demonstrates the cleaner production of natural flake graphite (NG) compared with artificial graphite. However, SGT anodes present issues regarding rate performance and cycle stability due to the anisotropy structure and the instability of the solid electrolyte interface (SEI). In this work, a composite anode with isotropic structure was prepared by granulation of high-sulfur coal (HSC) and SGT, while an artificial SEI was prepared utilizing polyether amine/polyvinyl pyrrolidone (PEA/PVP) crosslinked polymer. Results showed that the coke from HSC pyrolysis enhanced the isotropy of the composite anode and improved its rate performance. Compared with SGT, the capacity retention rate of the sample (OSGT-50%OHSC) after oxidation - pyrolysis at a high current density of 5.0 A g−1 increased from 7.2% to 25.8%. Additionally, the PEA/PVP artificial SEI strengthened the cycle stability of the anode. After 1000 cycles, the capacity retention rate increased from 22.5% to 70.3%. The artificial SEI effectively avoided direct contact between the anode and the electrolyte, increasing the initial coulombic efficiency from 70.3% to 77.1%.