The rapid growth of electric vehicle (EV) adoption in the United States is creating an unprecedented challenge in managing end-of-life lithium-ion batteries. While EV batteries typically retain substantial residual capacity after automotive use, inadequate recycling and reuse infrastructure risks environmental harm, resource inefficiency, and missed economic opportunities. This article examines the technical, economic, regulatory, and environmental dimensions of battery recycling and second-life applications within the U.S. EV ecosystem. It reviews current and emerging recycling technologies, evaluates second life use cases across grid, commercial, and residential energy storage, and analyzes economic viability, policy frameworks, and circular economy business models. The study situates battery lifecycle management within the broader EV and energy transition, highlighting the roles of grid integration, digital tracking, and artificial intelligence in enabling scalable solutions. The findings suggest that coordinated investment, regulatory harmonization, technological innovation, and stakeholder collaboration are essential to transforming retired EV batteries from waste liabilities into strategic assets. Establishing a robust circular battery economy is critical for long-term EV sustainability, resource security, and grid resilience in the United States.