In Situ‐Formed Hierarchical Metal–Organic Flexible Cathode for High‐Energy Sodium‐Ion Batteries

Metal–organic compounds are a family of electrode materials with structural diversity and excellent thermal stability for rechargeable batteries. Here, we fabricated a hierarchical nanocomposite with metal–organic cuprous tetracyanoquinodimethane (CuTCNQ) in a 3 D conductive carbon nanofibers (CNFs) network by in situ growth, and evaluated it as flexible cathode for sodium‐ion batteries (SIBs). CuTCNQ in such flexible composite electrode is able to exhibit a high capacity of 252 mAh g−1 at 0.1 C and highly reversible stability for 1200 cycles within the voltage range of 2.5–4.1 V (vs. Na+/Na). A high specific energy of 762 Wh kg−1 was obtained with high average potential of 3.2 V (vs. Na+/Na). The in situ‐formed electroactive metal–organic composites with tailored nanoarchitecture provide a promising alternative choice for high‐performance cathode materials in SIBs with high energy.