A revised mechanistic model for sodium insertion in hard carbons
A revised mechanistic model for sodium insertion in hard carbons
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DOI：
10.1039/d0ee01363c
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发表时间：
2020-10-01
影响因子：
32.5
通讯作者：
Titirici, Maria-Magdalena
中科院分区：
文献类型：
--
作者：
Au, Heather;Alptekin, Hande;Titirici, Maria-Magdalena
硬碳作为新兴钠离子电池技术的阳极已显示出巨大的前景。目前对硬碳中钠存储行为的理解将其归因于石墨夹层和孔隙的填充以及缺陷处的吸附，尽管关于这些机制发生的电压仍然存在相当大的争议。在这里，对一系列系统调谐的硬碳进行的异位 (23)Na 固态核磁共振和全散射研究表明，金属钠簇的形成与孔径的增大直接相关，仅发生在表现出低电压平台的样品中。将实验结果与 DFT 计算相结合，我们提出了一种修正的机制模型，其中钠离子首先同时连续地存储在缺陷处、夹层内和孔隙表面上。一旦这些较高能量的结合位点被填充，孔隙填充就会发生在平台区域，其中密集限制的钠呈现出更高程度的金属丰度。
Hard carbons have shown considerable promise as anodes for emerging sodium-ion battery technologies. Current understanding of sodium-storage behaviour in hard carbons attributes capacity to filling of graphitic interlayers and pores, and adsorption at defects, although there is still considerable debate regarding the voltages at which these mechanisms occur. Here,ex situ(23)Na solid-state NMR and total scattering studies on a systematically tuned series of hard carbons revealed the formation of increasingly metallic sodium clusters in direct correlation to the growing pore size, occurring only in samples which exhibited a low voltage plateau. Combining experimental results with DFT calculations, we propose a revised mechanistic model in which sodium ions store first simultaneously and continuously at defects, within interlayers and on pore surfaces. Once these higher energy binding sites are filled, pore filling occurs during the plateau region, where the densely confined sodium takes on a greater degree of metallicity.