Mitigating Dissolution to Enhance the Performance of Pillar[5]quinone in Sodium Batteries

Sodium-ion batteries using organic electrode materials are a promising alternative to state-of-the-art lithium-ion batteries. However, their practical viability is hindered by challenges such as a low specific capacity of the organic electrode materials, or their dissolution in the electrolyte. We herein present a double mitigation strategy to enhance the performance of pillar[5]quinone (P5Q) as positive electrode material in sodium batteries. Using 5 m sodium bis(fluorosulfonyl)imide in succinonitrile as highly concentrated electrolyte, as well as encapsulating P5Q in CMK-3 (Carbon Mesostructured by KAIST with hexagonally ordered rod-like carbon domains) as templated ordered mesoporous carbon, we achieve a record cycling performance with improved cycling stability even at elevated temperature (40 °C). The P5Q@CMK-3 composite electrode delivers 430 mAh g⁻¹ specific discharge capacity at 0.2 C rate with 90 % retention over 200 cycles. This corresponds to an energy density of 831 Wh kg⁻¹ (based on P5Q mass) and surpasses previous reports on pillarquinones. When operated at 40 °C, the P5Q@CMK-3 composite electrodes deliver a specific discharge capacity of 438 mAh g⁻¹ with 88 % capacity retention over 500 cycles (0.02 % per cycle). This study underscores the crucial role the electrolyte plays in advancing organic sodium batteries, offering a promising avenue for the future of sustainable energy technologies.