Abstract A graphene coated coal liquefaction residue (CLR) derived hard carbon (HC@G) composite anode for sodium ion batteries was prepared by thermal annealing the mixture of the chemically modified hard carbon with graphene oxide. The irregular shaped hard carbon particles were coated uniformly by wrinkled graphene sheets. Both HC and HC@G possess large inter-layer spacing and poor porosity, but a richer pore structure that facilitating ion transport was generated after graphene coating. Because poor conductive hard carbon particles are bridged by graphene sheets, a better conductivity of HC@G is detected by voltammetry test and the EIS analysis. Graphene coating contributes little to the sodium storage capacity. However, HC@G exhibits a much better rate performance and a dramatic improvement of cycling capability with the capacity retention 83% after 2000 cycles at a high current density of 2 A·g −1 . The impressing rate and cycle performances of HC@G anode are attributed to the hierarchical structure with rich ion diffusion channels and extensive electronic conduction path.

中文翻译：

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石墨烯包覆的煤液化残渣衍生硬碳作为钠离子电池负极材料的电化学性能增强

摘要 通过将化学改性的硬碳与氧化石墨烯的混合物进行热退火，制备了用于钠离子电池的石墨烯包覆煤液化残渣（CLR）衍生的硬碳（HC@G）复合负极。不规则形状的硬碳颗粒被起皱的石墨烯片均匀地包覆。HC 和 HC@G 均具有较大的层间距和较差的孔隙率，但在石墨烯涂层后产生了更丰富的孔结构，有利于离子传输。由于导电性较差的硬碳颗粒被石墨烯片桥接，因此通过伏安法测试和 EIS 分析检测到 HC@G 具有更好的导电性。石墨烯涂层对钠存储容量的贡献很小。然而，HC@G 表现出更好的倍率性能和循环能力的显着提高，在 2 A·g -1 的高电流密度下循环 2000 次后容量保持率为 83%。HC@G 阳极令人印象深刻的速率和循环性能归因于具有丰富离子扩散通道和广泛电子传导路径的分层结构。