A Comparison of Two Graphite Recycling Streams: Spent Lithium-ion Battery and Lithium-ion Battery Factory Anode Scrap

Abstract

This study investigates an efficient and clean method of recycling and purifying graphite from lithium-ion battery anode scrap, as an alternative to conventional graphite recycling methods from spent batteries. The focus of this study is contamination removal, where the concentration of elements is evaluated for the quality of final products. Graphite is recognized as a critical material due to its essential role in lithium-ion batteries and high demand in the rapid growth of energy storage industries. This research investigates spent lithium-ion battery and as two recycling streams, where the graphite recycled from anode production scraps offers superior graphite with lower concentration of contamination and minimal structural degradation. Conventional graphite recovery from spent lithium-ion batteries often exhibits degraded material properties and high impurity levels as results of electrochemical aging and complex sources of contamination. A systematic experimental approach was developed to evaluate multiple hydrometallurgical purification methods, including acid leaching, microwave-enhanced acid leaching, microwave-assisted alkaline leaching, and the combination of alkaline roasting and acid leaching. Such treatments aimed at the reduction of metallic and non-metallic impurities to battery grade level. Acid leaching with H₂SO₄ and H₂O₂ demonstrated high removal efficiencies (>95%) for transition metals such as Ni, Co, Mn, and Cu, while elements such as Ti and Si exhibited resistance. Such advanced purification techniques as microwave-enhanced acid leaching significantly increased element removal efficiency and achieved the best overall purification performance, reducing most impurity concentrations to low levels. However, elements such as Ti and Si persisted. Alkaline leaching showed strong selectivity toward amphoteric elements (e.g., Al and Si) but was ineffective for transition metals. The combination of alkaline roasting and acid leaching process demonstrated combined effects, where alkaline roasting altered impurity phases and enhanced subsequent acid leaching efficiency, resulting in substantial impurity reduction across a broad range of elements. Comparative investigation of purification methods revealed that while significant impurity reduction is achievable, such residual contaminants as Si, Ti, and Fe remain above the industrial standard required for battery-grade graphite. This study demonstrates that obtaining graphite from anode scrap rather than depleted batteries reduces the level of contamination with reduced chemical consumption, contributing to a more sustainable and energy-efficient recycling stream. Initial water leaching achieved the successful physical separation of graphite and Cu foil by exploiting the water-soluble nature of binders, preserving graphite morphology and limiting introduction of contaminations. Subsequent acid leaching successfully removed 99.9% of identified contaminate, Cu, from the graphite slurry. Further dewatering procedures obtained the graphite solid from the slurry mixture. Purified graphite concentrated from anode scrap was subjected to inductively coupled plasma mass spectrometer (ICP-MS) and particle size distribution for evaluation. Results suggested that graphite recycled from lithium-ion battery anode scrap exhibits superior property in concentration of contaminate (Fe, Ti, Cu < 10 ppm) and particle size (d₅₀ ≈ 17.99 μm). This study provides a comprehensive evaluation of graphite purification strategies and introduces anode scrap as a promising alternative stream. The proposed supply stream offers potential advantages in chemical property and complicity of recycling process, supporting the development of supply chains for critical materials in battery industries, reducing the reliance on graphite mining and conventional graphite recycling. Such findings exhibit both the technical feasibility and current limitations of graphite recycling processes.