Purpose <p>Environmental trade-offs of EV battery second-life strategies were quantified by comparing lithium nickel cobalt manganese oxide (NMC-811) and lithium iron phosphate (LFP) across the full life cycle. The research was directed to how chemistries differ across production, use, second-life processing, and recycling, and how electricity mix shapes outcomes. It was also tested whether refurbishment or remanufacturing reduces cradle-to-grave burdens and how benefits shift with grid carbon intensity and material-recovery value.</p> Methods <p>A cradle-to-grave life cycle assessment was conducted covering production, use, second-life processing (refurbishment/remanufacturing), and end-of-life recycling for NMC-811 and LFP. Impact categories were evaluated for global warming, particulate matter formation, terrestrial acidification, photochemical ozone formation, water consumption, and fossil versus mineral resource scarcity. Electricity sensitivity was explored using regional mixes: Thailand (baseline), fossil-heavy ASEAN, OECD low-carbon, and PV-coupled charging. Second-life burdens were parameterized from chemistry-specific materials and processing intensity; recycling credits were assigned from recovered metals. The functional unit was defined as one kWh of delivered traction energy over first life plus second-life service, with total energy throughput held constant to enable cross-chemistry comparison.</p> Results and discussion <p>Lower cradle-to-grave burdens were observed for LFP due to simpler composition and absence of Ni/Co, whereas higher recycling value but higher production and second-life processing burdens were associated with NMC-811. In use, 20% higher energy efficiency was achieved by NMC-811, conferring advantages on fossil-dominated grids. Use-phase burdens scaled near-linearly with grid carbon intensity: relative to Thailand, fossil-heavy ASEAN increased global warming by 27–28%; OECD low-carbon reduced it by 73%; PV-coupled charging rendered it near-negligible. Other categories tracked electricity effects emissions and water demand were reduced on cleaner grids, while mineral resource pressures tended to rise (e.g., PV and storage supply chains).</p> Conclusions <p>A trade-off was identified between energy efficiency and material sustainability: NMC-811 was favored on high-carbon grids for efficiency, whereas LFP was favored for lower material and processing burdens. Although premature waste is mitigated by second-life pathways, net benefits were shown to hinge on local electricity mix and achievable recycling credits. Alignment of chemistry and second-life use with regional grid decarbonization was found essential for minimizing total impacts.</p>