How does city-level differentiated pricing improve electric vehicle battery recycling efficiency? Evidence from dual-price signals of China

China's rapid adoption of New Energy Vehicles (NEVs) is creating a surge of end-of-life traction batteries. We study how dual prices from an annual minimum-cost flow model can guide capacity planning and dispatch in a three-layer reverse logistics network covering 54 major cities (≥58% of national NEV demand) during 2025–2035. We interpret the dual variables as managerial signals, including the collection price (θ), marginal dismantling congestion (ξ), and downstream capacity scarcity premium (ψ), and we quantify regional bottlenecks. By 2035, 57.1% of cities in both the Yangtze River Delta (YRD) and the Shandong–Henan (LuYu) exceed the extreme scarcity threshold (ψ > 4532 Chinese yuan (CNY) per kWh), while severe dismantling congestion (ξ > 300) affects 66.7% of Beijing–Tianjin–Hebei (BTH) cities. Recycling prices exhibit a stable state-of-health (SOH) gradient (∼42.26 CNY per kWh between 30% and 70% SOH), with regional heterogeneity mainly in baseline levels. Along optimized routes, process-stage carbon emissions rise from ∼0.220 megatonnes (Mt) in 2025 to ∼23.00 Mt in 2035 and are dominated by dismantling and recycling (97–98%). We translate these signals into trigger rules for operational control and capacity expansion, providing actionable thresholds and explicit exit criteria for place-based, city-level governance.