Sodium-ion batteries are emerging as promising alternatives to conventional lithium-based technology, offering solutions to challenges in large-scale grid storage. However, the capacity of conventional graphite-based anodes for storing Na-ions is inherently limited by suboptimal thermodynamic interactions and irreversible structural changes that occur in the anode during charge–discharge cycles. Herein, we present a computational design that explores the potential of graphullerene, a two-dimensional framework with interconnected fullerene moieties, for the reversible storage of Na-ions. A unique aspect of this design is the electron injection capacity into the graphullerene anode, reaching 15 electrons per fullerene moiety, which is the highest limit to date. This advancement enables large-scale Na-ion storage up to the stoichiometry of NaC₂, exhibiting specific capacity of 551 mAhg^–1 and averaged open circuit voltage of 0.18 V vs Na/Na⁺. In addition, the multilayered arrangement of stored Na-ions enhances the Na-ion diffusivity on the graphullerene surface, leading to rapid insertion and extraction kinetics. Thus, raising the electron injection limit offers a promising strategy to transform carbon-based anodes into suitable candidates for reversible Na-ion storage, without relying on artificial defect introduction or doping.

中文翻译：

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高效电子注入Graphullerene实现可逆NaC2钠存储


钠离子电池正在成为传统锂技术的有前途的替代品，为大规模电网存储的挑战提供解决方案。然而，传统石墨基阳极存储钠离子的能力本质上受到次优热力学相互作用和充放电循环期间阳极中发生的不可逆结构变化的限制。在此，我们提出了一种计算设计，探索石墨烯（一种具有互连富勒烯部分的二维框架）用于钠离子可逆存储的潜力。该设计的独特之处在于石墨烯阳极的电子注入能力，达到每个富勒烯部分 15 个电子，这是迄今为止的最高限制。这一进步使得大规模钠离子存储达到NaC ₂的化学计量，比容量为551 mAhg ^–1 ，平均开路电压为0.18 V vs Na/Na ⁺ 。此外，储存的钠离子的多层排列增强了石墨烯表面上的钠离子扩散率，从而导致快速插入和提取动力学。因此，提高电子注入极限提供了一种有前景的策略，可以将碳基阳极转变为可逆钠离子存储的合适候选者，而无需依赖人工缺陷引入或掺杂。