In-situ constructing uniform polymer network for iron oxide microspheres: A novel approach to improve the cycling stability of the conversion electrodes through chemical interaction

Abstract

Electrochemical conversion reaction provides potential high-capacity anode materials for Li-ion and Na-ion batteries. However, the inferior cyclability is seriously hindering their applications. Herein, a novel strategy is introduced to improve the performance of conversion-type Fe2O3-AHP composite by using an organic amino-hyperbranched polymer additive. The amino groups of polymers could coordinate with Fe3+ through chemical interaction, and make Fe2O3 particles self-assemble into unique microspheres in solvothermal process. Moreover, the polymer additive in-situ constructs 3D uniform elastic frame work on molecular level in Fe2O3-AHP composite, which could accommodate the volume change and stabilize the Fe2O3 structure during lithiation/delithiation or sodiation/desodiation processes. Therefore, compared with Fe2O3-AHP-500 in which AHP was removed by heat treatment, the Fe2O3-AHP microspheres exhibit excellent long-term Li-storage (98.3% capacity retention rate after 1000 cycles at 2.0 A g−1) and Na-storage cyclabilities and maintain the integrity of microsphere structure after cycling. Furthermore, the polymer additive makes the Fe2O3-AHP microsphere have plenty of nanopores, which facilitate electrolyte infiltration and ion diffusion and thus enhance the kinetic performance. The present study highlights a novel strategy of in-situ construction of stable network on molecular level using polymer additive via strong chemical interaction, which delivers inspiration optimizing the long-term cyclability of conversion-type materials.