Al and Cu Oxalates in Li‐Ion Battery Electrolytes: Comparative Observations and Recycling Consequences

Given that Li‐ion batteries are rapidly increasing in their spread, effective recycling approaches and thus contamination management of the recycled material have become essential. We investigated oxalate‐based recycling options using metal oxalates (focusing on Al and Cu) as model impurities in graphite || LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) full cells. Fresh 1 M LiPF 6 in 50/50 v/v ethylene carbonate/dimethyl carbonate (LP30) electrolytes without and with contaminants at their maximum solubility were compared with aged electrolytes. Electrochemical testing revealed that aged LP30‐based contaminated electrolytes matched cells with freshly contaminated electrolytes: they retain the same capacity and have matching impedance spectra. In the absence of vinylene carbonate (VC), neither is time‐dependent degradation detectable nor does metal oxalate contamination impair cell performance. Chemical analyses confirmed that no detectable chemical reactions occurred between any metal oxalate and the VC‐free electrolyte during the 30‐day aging period. In contrast, when VC was present, adding Al or Cu oxalate to the electrolyte increased internal cell resistance and accelerated capacity fade during cell cycling. Post‐mortem analyses revealed Al‐containing surface layers on graphite electrodes, indicating that performance decreases because Al oxalate‐derived films are formed. These results highlight the complex interplay between electrolyte additives and impurity specification in battery aging.