Direct Recycling at the Material Level: Unravelling Challenges and Opportunities through a Case Study on Spent Ni‐Rich Layered Oxide‐Based Cathodes

Abstract

AbstractDirect recycling is a key technology for enabling a circular economy of spent lithium ion batteries (LIBs). For cathode active materials (CAMs), it is regarded as the tightest closed‐loop and most efficient approach among current recycling techniques as it simply proceeds via re‐lithiation and reconstruction of aged CAMs instead of separating them into elemental components. In this work, spent, i.e., morphologically and structurally decomposed CAM based on LiNi0.83Co0.12Mn0.05O2 (NCM‐831205) is restored by mimicking conditions of original CAM synthesis. After evaluating and optimizing the high‐temperature duration for CAM restoration and subsequent washing procedure, the recycled CAM is shown to maintain poly‐crystallinity and tap density, successfully recover specific surface area, lithium content, crystal structure in surface and bulk, while, however, only partly the original secondary particle size and shape. Though, comparable in initial 100 charge/discharge cycles with pristine CAM in lithium ion‐cells, the subsequent increase in resistance and capacity fading remains a challenge. High temperature during recycling can be regarded as a key challenge on material level, as it not only promotes detrimental surface carbonate species from residual carbon black but also enhances cation disorder and micro‐/nanoscopic porosity through oxygen release, likely in de‐lithiated, thus less thermally stable regions of cycled NCM.