A Pouch‐Cell Low‐Temperature All‐Organic Sodium‐Ion Battery

Sodium‐ion batteries (SIBs) are promising for low‐temperature applications compared with commercial lithium‐ion batteries, because of the weaker solvation and higher conductivity of Na + in electrolytes. However, the large size of Na + leads to slow ionic transport and sluggish reaction kinetics in the electrodes, which is more severe after the lattice shrinks under low temperatures. Herein, a conjugated coordination polymer (CCP) is reported as a cathode for low‐temperature SIBs, by using naphthazarin (DHNQ) as the ligands and Ni 2+ as the metal centers. Benefiting from the π‐d conjugation, the Ni‐DHNQ exhibits a high electrical conductivity of 69.7 mS/m and maintains both structural integrity and efficient electron and ion transport even at −40°C. These characteristics collectively enhance the reaction kinetics and cycling stability. The Ni‐DHNQ cathode enables ultrafast charging to 52% state‐of‐charge (SOC) in 90 s and exhibits an ultralow capacity decay rate of 0.0028% per cycle over 5000 cycles. When paired with an organic anode, the pouch full‐cell could reach 87% of its SOC even at −40°C, far higher than the commercial lithium‐ion batteries (12%) and reported alkali‐metal‐ion batteries. This work demonstrates the promise of CCPs for high‐performance sustainable energy storage under extreme conditions.