Hydrogen-bond relay enables grotthuss-like hopping in polymer-pillared V6O13 tunnel anode

Aqueous ammonium-ion batteries (AAIBs) offer a sustainable energy storage pathway but are limited by sluggish ion transport and structural instability. Here, we report a polymer-functionalization strategy by intercalating poly(2-ethyl-2-oxazoline) (EtOx) into tunnel-structured V 6 O 13 to form EtOx-V 6 O 13 . The intercalated polymer not only expands and stabilizes diffusion channels but also introduces abundant carbonyl groups that form N–H···O=C hydrogen bonds with . These interactions establish a dynamic hydrogen-bond network that enables relay-like transport via continuous bond breaking and reformation, thereby significantly lowering migration barriers and facilitating rapid ion conduction. Notably, this process involves the coordinated movement of intact ions through successive docking at carbonyl sites, distinguishing it from classical proton hopping. The synergistic effects of structural expansion and hydrogen-bond-mediated transportation also buffer lattice strain and enhance structural integrity during cycling. As a result, EtOx-V 6 O 13 -0.4 delivers 227.8 mAh g −1 at 1 A g −1 , retains 102.6 mAh g −1 at 20 A g −1 , and achieves 90.2% capacity retention over 5000 cycles. A full cell with MnO 2 exhibits 146.9 mAh g −1 at 0.1 A g −1 and an energy density of 110.2 Wh kg −1 . This work highlights polymer-functionalized tunnel oxides as an effective platform for hydrogen-bond-mediated ion transport in AAIBs.