NaV₃O₈/poly(3,4-ethylenedioxythiophene) composites as high-rate and long-lifespan cathode materials for reversible sodium storage

Sodium-ion batteries have received a surge of interests for the alternatives to lithium-ion batteries due to their abundant reserves and low cost. The quest of reliable and high-performance cathode materials is crucial to future Na storage technologies. Herein, poly(3,4-ethylenedioxythiophene) (PEDOT) was successfully introduced to NaV₃O₈ via in situ oxidation polymerization, which can effectively enhance electron conductivity and ionic diffusion of NaV₃O₈ material. As a result, these NaV₃O₈@PEDOT composites exhibit a significantly improved electrochemical performance including cycle stability and rate performance. In particular, NaV₃O₈@20 wt% PEDOT composite demonstrates better dispersibility and lower charge transfer resistance compared with bare NaV₃O₈, which delivers the first discharge capacity of 142 mAh·g⁻¹ and holds about 128.7 mAh·g⁻¹ after 300 cycles at a current density of 120 mA·g⁻¹. Even at a high current density of 300 mA·g⁻¹, a high reversible capacity of 99.6 mAh·g⁻¹ is revealed. All these consequences suggest that NaV₃O₈@20 wt% PEDOT composite may be a promising candidate to serve as a high-rate and long-lifespan cathode material for sodium-ion batteries.