The lithium metal anode is considered to be the ultimate anode material for high-energy-density rechargeable batteries. However, the application of lithium metal batteries is plagued by Li dendrite growth. Here, we report a flexible polymer (polyacrylic acid–Pluronic, PAF) interface for dendrite-free lithium metal batteries. The lithiophilic groups (ester group) in PAF can coordinate with lithium ions for the uniform distribution of lithium ions at the lithium/electrolyte interface, thus achieving dendrite-free lithium deposition. Moreover, the PAF polymer interface exhibits a high stretchability (278% strain to its initial length) and can tolerate the huge volume change during the plating/stripping processes. Consequently, the symmetric cells with the PAF@Li anode deliver excellent cycling stability over 600 h (1 mA cm–2, 2 mAh cm–2) with a slight overpotential of around 76 mV. Notably, the PAF@Li|LiNi0.8Co0.1Mn0.1O2 full cell exhibits a high capacity retention of 78.5% with a high cathode mass loading (16.5 mg cm–2) even after 190 cycles at 1 C (3.5 mA cm–2).