A re-evaluation of battery-grade lithium purity reveals that a 1% Mg impurity in lithium precursors can enhance both lithium production and cathode electrochemical performance. This is attributed to increased nucleation seeds and site-selective doping effects. Industrial-scale application of low-grade lithium reduces production costs and CO₂ emissions by up to 19.4% and 9.0%, respectively. Lithium-ion batteries (LIBs) are crucial for portable electronics and electric vehicles due to their high energy density. However, the cost of LIBs, especially cathode materials, remains a barrier to affordable EVs. Recent strategies aim to replace expensive transition metals with low-cost elements, but lithium prices have surged, making lithium source costs now exceed those of transition metals. The study highlights that Mg impurities in lithium production can improve flowability, production speed, and electrochemical performance through seeding effects and site-selective doping. The inclusion of Mg impurities also reduces purification costs and CO₂ emissions. Electrochemical tests showed that Mg-doped cathodes from low-grade lithium sources outperformed conventional methods, with the LCD cathode achieving the highest capacity retention. The study also found that Mg impurities can be selectively incorporated into Li sites, enhancing cyclability and rate capability. The findings suggest that re-evaluating battery-grade lithium purity can lead to more sustainable and cost-effective LIBs. The economic and environmental impacts of using low-grade lithium with 1% Mg impurity were analyzed, showing significant reductions in costs and emissions. The study provides insights into the sustainability of lithium-ion batteries by demonstrating that impurities can be beneficial when properly managed.A re-evaluation of battery-grade lithium purity reveals that a 1% Mg impurity in lithium precursors can enhance both lithium production and cathode electrochemical performance. This is attributed to increased nucleation seeds and site-selective doping effects. Industrial-scale application of low-grade lithium reduces production costs and CO₂ emissions by up to 19.4% and 9.0%, respectively. Lithium-ion batteries (LIBs) are crucial for portable electronics and electric vehicles due to their high energy density. However, the cost of LIBs, especially cathode materials, remains a barrier to affordable EVs. Recent strategies aim to replace expensive transition metals with low-cost elements, but lithium prices have surged, making lithium source costs now exceed those of transition metals. The study highlights that Mg impurities in lithium production can improve flowability, production speed, and electrochemical performance through seeding effects and site-selective doping. The inclusion of Mg impurities also reduces purification costs and CO₂ emissions. Electrochemical tests showed that Mg-doped cathodes from low-grade lithium sources outperformed conventional methods, with the LCD cathode achieving the highest capacity retention. The study also found that Mg impurities can be selectively incorporated into Li sites, enhancing cyclability and rate capability. The findings suggest that re-evaluating battery-grade lithium purity can lead to more sustainable and cost-effective LIBs. The economic and environmental impacts of using low-grade lithium with 1% Mg impurity were analyzed, showing significant reductions in costs and emissions. The study provides insights into the sustainability of lithium-ion batteries by demonstrating that impurities can be beneficial when properly managed.