Electronic delocalization in polyoxometalates creates electron highways for ultrastable lithium storage

Polyoxometalates (POMs) combine low cost with rich multielectron redox chemistry, positioning them as viable anode materials for lithium-ion batteries (LIBs). However, their advancement is impeded by poor intrinsic electronic conductivity and scarce lithium storage sites. In this study, the Preyssler-type polyoxotungstate (K_12.5Na_1.5[NaP₅W₃₀O₁₁₀]·15H₂O, denoted as P₅W₃₀) is employed as a model system to investigate and enhance the electrochemical performance of POM-based LIB anodes. Through precisely incorporating transition metal (TM) atoms at the linkage sites of the P₅W₃₀ units (denoted as TM-P₅W₃₀, TM = Mn or Cu), we elucidate the mechanism underlying the improved electron transport, which establishes "electron highways" with the P₅W₃₀-TM framework, analogous to the π-electron delocalization in aromatic systems. Combine in-suit XRD, in-suit EIS, ex-suit IR, ex-suit TEM and theoretical calculations collectively reveal that the "TM bridge" architecture formed in TM-P₅W₃₀ provides efficient dual pathways for electron and ion transfer, thereby enabling reversible lithium insertion/extraction and substantially improving cycling stability. As a result, the Mn-P₅W₃₀ delivers a high capacity of 558 mAh g^-1 and maintains splendid stability over 1500 cycles. This work offers atomic-level insights into the relationship between electronic structure and electrochemical performance, providing a theoretical basis for guiding the design of high-performance LIB anodes.