The presence of co-occurring ions poses a key challenge in solution purification for the conventional production of battery-grade lithium hydroxide, whether from hard rock minerals, brines, or end-of-life lithium-ion batteries. The production of battery-grade lithium hydroxide by electrodialysis is no exception. In this study, co-occurring ions, namely potassium (K), sodium (Na), and calcium (Ca), were investigated to determine their impact on lithium hydroxide production by electrodialysis. Lithium liquors studied include lithium sulfate and lithium carbonate. At impurity concentrations below 250 mg/L, the current efficiency across both systems remained stable, with no significant variation. However, as impurity concentrations increased, process performance declined below baseline levels due to increased competition between the impurity ions and lithium. Therefore, low levels of Na, K, or Ca impurities have minimal impact on process performance; nonetheless, product purity was negatively affected. Scaling of the cation-exchange membranes was observed in the lithium carbonate system. This was mainly driven by the interfacial precipitation of lithium carbonate, not the impurities, at the membrane surface. Electron-dispersive X-ray spectroscopy (EDS) results showed no detectable impurity peaks on the membrane surface, confirming that the scales were not caused by impurities.