Copper selenide/amino hyperbranched polymer as an organic/inorganic hybrid composite cathode for rechargeable magnesium batteries

Rechargeable magnesium batteries (RMBs) are suitable energy-storage devices for large-scale applications, while the lack of cathodes is impeding the development. In the present study, an organic/inorganic hybrid composite cathode material, copper selenide with amino hyperbranched polymer (CuSe-AHP), is fabricated and investigated as a RMB cathode and compared with CuSe without AHP. Both CuSe-AHP and CuSe show microflower morphologies, but CuSe-AHP contains organic AHP additive (5.0 wt%) uniformly distributed therein, with the amino groups coordinated with the copper cations. CuSe-AHP delivers a high capacity of 227 mA h g-1 at 100 mA g-1, a good rate performance of 87.5 mA h g-1 at 1.0 A g-1, and a high-capacity retention rate of 75.4% after 200 cycles, which makes it much more advantageous than CuSe without the AHP additive. The AHP in CuSe-AHP establishes a large organic/inorganic interphase for charge transfer, thus improving the conversion reaction kinetics. The coordination of copper cations by the amino groups enhances the structural stability, and the elastic polymer matrix buffers the volume change and stress increase of conversion-type magnesium storage reactions. As a result, CuSe-AHP shows a higher structural stability and a better cyclability than CuSe. The present study suggests that using organic/inorganic hybrid materials is a feasible method to develop cathode materials for RMBs. An organic/inorganic hybrid cathode is used for rechargeable magnesium batteries. Large interphase favors charge transfer, coordination of Cu2+ by the polymer enhances cyclability, and elastic matrix buffers volume change of conversion reaction.