Donor-Acceptor Porous Aromatic Framework Cathode with Fast Redox Kinetics for Ultralow-Temperature (-70 °C)...

Low-temperature rechargeable batteries are essential for cryogenic energy storage. However, lowering the working temperature will exacerbate the disadvantages of slowed reaction kinetics and mechanical instability of inorganic electrode materials, thus causing severe capacity degradation. In this work, for the first time, we demonstrated that constructing a donor-acceptor (D-A) porous aromatic framework (PAF-310) using p-type phenazine (PZ) and n-type hexaazatrinaphthylene (HATN) as storage blocks can accelerate charge transport and thus facilitate the reaction kinetics even at low-temperature conditions. When employed as the cathode of potassium ion batteries (PIBs), PAF-310 possesses higher electrochemical performance than its counterparts, including impressive discharge specific capacity (215.6 mAh g^-1 at 0.2 A g^-1) and outstanding rate performance (77.8 mAh g^-1 at 50 A g^-1) at 25 °C. Furthermore, PAF-310 also delivers impressive specific capacities in low-temperature conditions (168.2 mAh g^-1 at -20 °C and 130.1 mAh g^-1 at -40 °C at 0.2 A g^-1). Even at -70 °C, PAF-310 still exhibits good specific capacity (102.2 mAh g^-1 at 50 mA g^-1). Moreover, various in/ex-situ spectral characterizations and theoretical calculations were employed to elucidate the continuous co-storage mechanism of K⁺ and PF₆ ^- in PAF-310. This contribution sheds a feasible molecular design strategy towards low-temperature stabilized PIBs.