Polyethylene (PE) is one of the most widely used plastics, and vast amounts of waste PE are either buried or incinerated, leading to environmental concerns. Significant research efforts have focused on converting waste PE into carbon materials, particularly as carbon anodes for lithium-ion batteries (LIBs). However, most previously developed PE-based carbon anodes have underperformed compared to graphite-based commercial anode materials (CAM). In this study, LIB anode materials were prepared based on both commercial high-density polyethylene (CPE) and waste high-density polyethylene (WPE). Through thermal oxidative stabilization and high-temperature graphitization, both CPE and WPE were successfully transformed into highly crystalline carbon materials comparable to CAM. However, despite the high crystallinity, both CPE and WPE derived carbon contained significant number of fine particles and exhibited a broad particle size distribution. When used as an anode for LIBs, fine particles led to unwanted side reactions, resulting in an initial coulombic efficiency (ICE) of around 85%, which is lower than the ICE value of 92.5% observed in CAM. To tackle the low ICE problem, recarbonization after coal tar (CT) coating was adopted as a mean to induce secondary particle formation. After CT coating, the average particle size increased, and the size distribution became narrower. Although CT coating reduced the crystallinity slightly, the overall level remained comparable to that of CAM. As a result, the CT-coated graphitized CPE (GCPE@10CT) and CT-coated graphitized WPE (GWPE@10CT) exhibited performance comparable to CAM as LIB anodes, achieving an ICE of over 93% and a capacity of approximately 349 mAh g− 1.

A highly functional, environmentally friendly carbonaceous adsorbent material using black liquor (a by-product from the pulp manufacturing) was produced and characterized. This study showed the effect of self-chemical activation driven by inherent alkali, originated from the unique composition of black liquor. A preparation of the micropore-dominant activated carbon was made in an easy and simple manner. The specific surface areas of samples were found to be 718–1591 m2/ g variated upon heat treatment conditions. The sample activated at 850 °C (50 min as retention time) showed the maximum specific surface area of 1591 m2/ g with 13.6% as a production yield. Considering the factors influencing pore structure of activated carbon materials in this study, it was confirmed that mesopore-related surface area increased gradually as the activation temperature and retention time increased. It is noteworthy to address that economically valuable micropore-dominant activated carbon can be produced by a simple heat treatment of the waste material, black liquor. The activated carbon sample derived from black liquor can be applied to various fields, such as environment and energy storage.