Anode-free lithium metal batteries (AFLMBs), which are manufactured without anode active material, offer great potential for high-energy-density, low-cost energy storage. However, AFLMBs face a long-standing challenge of short lifespan because of the harsh conditions of lacking excess Li resource and an anode host1–8. This issue is associated with uneven Li deposition and dissolution, rooted in the micro-heterogeneity and mechanical fragility of solid electrolyte interphase (SEI)9. Here we report a practical 500 Wh kg–1-level AFLMB with enhanced lifespan, achieved using a crossover-coupled electrolyte. The electrolyte triggers crossover-coupled interfacial reactions that generate a B–F-based polymer-rich SEI at the anode while suppressing gas evolution at the cathode. The resulting SEI exhibits sub-nanometre homogeneity, high flexibility and rapid Li-ion transport, and it spontaneously develops a self-adaptive mesh-film structure that ensures uniform ion flux and large-volume-change accommodation, thereby realizing reversible planar Li deposition and dissolution of 5.6 mAh cm–2. Consequently, a 2.7 Ah AFLMB (508 Wh kg–1, 1,668 Wh l–1) without any host-material coating demonstrates stable cycling for 100 cycles at 100% depth of discharge (DOD) and 250 cycles at 80% DOD, with 80% capacity retention and a high-power output of 2,650 W kg–1 at 96 Wh kg–1. These findings establish crossover-coupled interphase chemistry and address the inherent structural instability of host-free electrodes, advancing the practical implementation of AFLMBs.
