This study re-evaluates the impact of impurity levels on the production and performance of lithium-ion batteries. The research highlights that a 1% Mg impurity in lithium precursors can enhance both the lithium production process and the electrochemical performance of resulting cathodes. This is attributed to increased nucleation seeds and unexpected site-selective doping effects. When scaled up to an industrial level, low-grade lithium reduces production costs and CO₂ emissions by up to 19.4% and 9.0%, respectively. The study provides valuable insights into the sustainability of lithium-ion batteries by demonstrating that slightly impure lithium sources can improve efficiency and reduce environmental impact.This study re-evaluates the impact of impurity levels on the production and performance of lithium-ion batteries. The research highlights that a 1% Mg impurity in lithium precursors can enhance both the lithium production process and the electrochemical performance of resulting cathodes. This is attributed to increased nucleation seeds and unexpected site-selective doping effects. When scaled up to an industrial level, low-grade lithium reduces production costs and CO₂ emissions by up to 19.4% and 9.0%, respectively. The study provides valuable insights into the sustainability of lithium-ion batteries by demonstrating that slightly impure lithium sources can improve efficiency and reduce environmental impact.