Tuning Microstructures of Graphene to Improve Power Capability of Rechargeable Hybrid Aqueous Batteries

Low conductivity and structural degradation of LiMn₂O₄ lead to poor power capability and severe capacity fading of hybrid aqueous Zn/LiMn₂O₄ battery. Here, we propose an effective strategy by tuning the microstructures of graphene to optimize its electrical and interfacial properties and electrode dynamics of LiMn₂O₄/graphene cathodes, which successfully prompt significant improvements in electrical conductivity and structural stability, thus essentially leading to a promising electrochemical performance. More importantly, it reveals different electrochemical properties prompted by different conductivity, which mainly depends on the microstructures of graphene. This dependence is due to the influence of electronic channels and conductive paths on the conductivity of LiMn₂O₄/graphene electrodes. A well-designed mesoporous graphene composed of about two graphene-layers exhibits an excellent high-rate performance; even after 300 cycles, a highly reversible capacity of 75 mAh g^-1 is retained at 4C rate. The results of this study suggest that the structural tuning of electronic channels of graphene can be used as an effective means to improve the performance of LiMn₂O₄ cathodes in hybrid aqueous batteries.