Organic cathodes offer great promise for rechargeable magnesium batteries (RMBs) owing to their structural tunability and fast Mg^2+ transport, yet their dissolution in ether-based electrolytes leads to rapid capacity fading and poor rate performance. Herein, we design a high-performance sulfur-containing heterocyclic quinone cathode, benzobnaphtho2′, 3′: 5, 61, 4dithiino2, 3-ithianthrene-5, 7, 9, 14, 16, 18-hexone (BNDTH), coupled with a functional carbon-coated separator composed of graphene oxide (GO) and carboxylated multi-walled carbon nanotubes (MWCNTs−COOH) at an optimized 1: 9 mass ratio. In this architecture, GO provides physical confinement to suppress BNDTH diffusion, while MWCNTs−COOH offer abundant chemical adsorption sites to immobilize soluble species. This synergistic confinement–adsorption mechanism effectively mitigates active-material loss and promotes charge transfer. As a result, the Mg//BNDTH cell exhibits significantly improved rate capability, delivering cathode capacities rising from 153 to 261 mAh g^−1 at 1 C and from 26 to 100 mAh g^−1 at 10 C over 500 cycles, along with cell-level power and energy densities of 4517 W kg^−1 and 222 Wh kg^−1, respectively—surpassing most reported RMBs employing organic cathodes. This work presents a viable separator-engineering strategy for achieving stable and high-rate operation of soluble organic cathodes in RMBs.
Qi et al. (Thu,) studied this question.