Engineering B₄O₇2−-cross-linked double‑carbon layer separators for mitigating molecular shuttle in rechargeable small-molecule batteries

Organic electrode materials are considered as a promising alternative to conventional transition metal-based electrodes because of their low cost, adjustable structure, high specific capacity, and good sustainability. However, many organic molecule electrodes and their corresponding discharge products can be easily dissolved in liquid electrolytes, leading to severe shuttle effect and performance decay. Here, we designed a separator with double carbon layer modification. The first layer is a B 4 O 7 2− cross-linked GO layer, which serves as a barrier to prevent organic small molecules from passing through the separator attributed to physical blocking and electrostatic repulsion. The second layer is a carbon nanotube layer, which mainly acts as an absorbing layer and upper current collector attributed to porous structure and good conductivity. The synergistic effect of double carbon layer enables the GO-B 4 O 7 2− @CNT-modified separator to effectively inhibit the shuttling of small molecules while maintaining their intrinsic electrochemical performance. Three soluble organic electrode materials with different molecular sizes, including 2,3,5,6-tetraamino-benzoquinone (TABQ), 9,10-anthraquinone (AQ), and 3,4,9,10-perylenetetracarboxylic diimide (PTCDI), were used as model molecules to validate the availability of modified separator, and the results shows that their cycling stability, specific capacity and rate capability were enhanced significantly after using the separator. Such simple cost-effective separator modification method will substantially promote the battery performance and facilitate the application of organic small molecule electrodes for energy storage.