Polyaniline/Polyoxometalate Hybrid Nanofibers as Cathode for Lithium Ion Batteries with Improved Lithium Storage Capacity

Hybrid nanofibers of polyaniline/polyoxometalate are synthesized via a facile interfacial polymerization method for the first time, and evaluated as a cathode material for lithium ion batteries. The hybrid nanofibers with 100 nm diameter consisted of phosphomolybdic acid polyanion, [PMo₁₂O₄₀]^3–, and polyaniline matrix. Their 1D geometry improves the utilization of electrode materials and accommodates the volume change during cycling, which enables the significant improvement in lithium storage capacity and capacity retentions. The phosphomolybdic acid polyanions not only exhibit a large theoretical capacity of about 270 mAh g^–1, but also reduce the charge transfer resistance of electrode leading to the enhanced reversible capacity and rate capability. The polyaniline/polyoxometalate nanofibers delivered a remarkably improved electrochemical performance in terms of lithium storage capacity (183.4 mAh g^–1 at 0.1C rate), cycling stability (80.7% capacity retention after 50 cycles), and rate capability (94.2 mAh g^–1 at 2C rate) compared to polyaniline nanofibers and bulk polyaniline/polyoxometalate hybrid.