The global energy transition is increasingly reliant on lithium-ion batteries for electric transportation and renewable energy integration. To reduce the EU's reliance on imported battery materials, the study investigates the potential of vehicle-to-grid (V2G) and second-life (SLB) batteries to provide energy and material security. Using dynamic material flow analysis, the research shows that equipping 50% of electric vehicles with V2G or reusing 40% of EV batteries for SLB could fully cover the EU's stationary storage needs by 2040, reducing primary material demand by up to 7.5% from 2020 to 2050. This could ease geopolitical risks and enhance energy and material security. The study also explores the competition between V2G and SLBs, finding that V2G can reduce peak and cumulative primary material use more effectively than SLBs. The findings highlight the importance of considering both electric transportation and grid storage when assessing future resource needs for lithium-ion batteries, emphasizing the need for policies that balance self-sufficiency and resource efficiency.The global energy transition is increasingly reliant on lithium-ion batteries for electric transportation and renewable energy integration. To reduce the EU's reliance on imported battery materials, the study investigates the potential of vehicle-to-grid (V2G) and second-life (SLB) batteries to provide energy and material security. Using dynamic material flow analysis, the research shows that equipping 50% of electric vehicles with V2G or reusing 40% of EV batteries for SLB could fully cover the EU's stationary storage needs by 2040, reducing primary material demand by up to 7.5% from 2020 to 2050. This could ease geopolitical risks and enhance energy and material security. The study also explores the competition between V2G and SLBs, finding that V2G can reduce peak and cumulative primary material use more effectively than SLBs. The findings highlight the importance of considering both electric transportation and grid storage when assessing future resource needs for lithium-ion batteries, emphasizing the need for policies that balance self-sufficiency and resource efficiency.