Recycling graphite from end-of-life lithium-ion batteries presents challenges beyond economic considerations. Graphite is difficult to separate in high purity from battery waste streams and is therefore rarely targeted as a dedicated recycling product. Conventional purification approaches often involve aggressive leaching or high-temperature treatments, which alter particle surface chemistry and reduce lithium-ion intercalation performance at high C-rates as well as initial formation efficiency. Surface remodification with amorphous carbon offers a promising route to enable the reuse of recycled graphite in high-performance battery applications. As recycled graphite is not yet widely available due to the absence of large-scale recycling processes, unmodified natural graphite with comparable surface properties can be used as a model material for process development.

Recycled graphite was obtained from aged battery cells through comminution, classification, pyrolysis, leaching, and high-temperature regraphitization. Despite improving material purity, the reconditioning steps reduced the density of lithium-ion intercalation-active sites, resulting in diminished fast-charging performance. To address this issue, a simple and scalable dry process was developed in which graphite is dry-mixed with pitch, carbonized in a rotating tube furnace, and subsequently sieved to remove aggregates.

The coating process was optimized using natural graphite by varying the pitch-to-graphite ratio and the pyrolysis temperature. At 10 wt.% pitch and a pyrolysis temperature of 900 °C, the specific surface area decreased from 9.3 to 4.3 m² g⁻¹, indicating the formation of an amorphous carbon layer with an increased density of intercalation-active sites. The coated material exhibited higher initial coulombic efficiency and approximately doubled capacity at a 3C charge rate compared to uncoated graphite. Increasing the pitch content above 10 wt.% further reduced the specific surface area but also decreased overall yield due to aggregation caused by excess pitch.

The optimized 10 wt.% pitch coating was subsequently applied to recycled graphite, reducing the specific surface area from 3.1 to 1.5 m² g⁻¹ and improving the 3C fast-charge capacity from 45 to 85 mAh g⁻¹. The initial coulombic efficiency reached 93.0%, comparable to commercial graphite.

Overall, the simple pitch-derived carbon coating restores surface functionality and fast-charge capability of recycled graphite, supporting its reintegration into lithium-ion battery anodes and facilitating the development of industrial graphite recycling routes.