Abstract:
Rapid growth of the new-energy vehicle industry has significantly increased the demand for high-performance batteries. Among various energy storage technologies, lithium-ion batteries (LIBs) have become the dominant choice owing to their high energy density, long cycle life, and environmental advantages. Graphite, a critical component of LIBs, has been widely adopted as the primary anode material in commercial batteries because of its low cost, high energy density, excellent electrical conductivity, and superior cycling stability. However, as LIBs undergo repeated charge-discharge cycles, the graphite anode gradually degrades. This degradation primarily results from the formation of a solid electrolyte interphase (SEI) layer and the growth of lithium dendrites on the graphite surface. The SEI layer, though initially necessary for battery operation, becomes excessively thick over time, thereby impeding lithium-ion transport. Simultaneously, lithium dendrites can penetrate the separator, causing internal short circuits and safety hazards. These issues lead to structural damage in the graphite anode, reducing its electrochemical performance and ultimately resulting in battery failure. Consequently, large quantities of spent graphite anodes are discarded, leading to resource wastage and environmental concerns. To address these challenges and promote the sustainable use of graphite, researchers have focused on developing techniques to restore failed graphite anodes. Among various regeneration strategies, material coating technology has emerged as highly effective. By applying a protective or functional layer onto the degraded graphite surface, structural defects can be repaired and the electrochemical performance can be restored. This article reviews the recent advancements in material coating techniques for regenerating failed graphite anodes. First, we discuss the necessary pretreatment steps, including impurity removal methods, such as acid leaching, thermal treatment, and solvent extraction, essential for preparing degraded graphite for regeneration. Next, this study examines three key coating strategies: (1) Asphalt coating – asphalt, a carbon-rich material, is carbonized at high temperatures to form a conductive layer that repairs surface cracks and enhances electrical conductivity. (2) Metal oxide coating materials, such as Fe
2O
3, TiO
2 and TiNb
2O
7 have been applied to stabilize the SEI layer and suppress lithium dendrite growth. (3) Polymer coating: conductive polymers and functional polymers (e.g., biofilms) improve the mechanical strength and interfacial stability. These coating methods have proven effective in restoring the structural integrity and electrochemical performance of graphite anodes, thereby enabling their reuse in LIBs. However, some challenges remain, including the need for scalable production methods, cost optimization, and long-term stability under high-voltage conditions. Future research should focus on developing multifunctional composite coatings that combine the advantages of different materials as well as exploring green and low-cost coating techniques to improve sustainability. Additionally, integrating advanced process control methods, such as artificial intelligence and automation, can enhance the consistency and efficiency of graphite regeneration. In conclusion, the material coating technology offers a promising solution for the regeneration of failed graphite anodes, contributing to the sustainable development of the LIB industry. By refining these techniques and addressing existing limitations, we can improve resource utilization, reduce environmental impact, and support the continued growth of the new energy sector.