Hard Carbon Microsphere with Expanded Graphitic Interlayers Derived from a Highly Branched Polymer Network as Ultrahigh Performance Anode for Practical Sodium-Ion Batteries

Abstract

Growing attention has been attached to hard carbon in sodium-ion batteries (SIBs). However, hard carbon from individual precursors tends to exhibit an inferior rate capability due to its limited interlayer distance. Here, a coupled strategy is designed to prepare hard carbon microspheres (HCMSs) via the pyrolysis of a highly branched polymer network formed instantaneously between two interactive precursors during the atomization of the spray drying process. The combined precursors with a tunable cross-linked structure prefer to generate a large interlayer spacing (0.399 nm) and abundant closed pore structure by suppressing the graphitization of precursors during the carbonization, relative to the individual precursor, which contributes greatly to the ion diffusion kinetics. Benefiting from the unique structure, HCMS exhibits an impressively high reversible specific capacity of 373.4 mA h g–1 in SIBs and high initial Coulombic efficiency of 88%, retaining 90.2% of the initial capacity even after 150 cycles, which presented comparable capacities with commercial graphite in lithium-ion batteries. Besides, excellent rate capability was also demonstrated with HCMSs (250 and 117 mA h g–1 at 300 and 600 mA g–1). Notably, the interlayer distance and closed pore structure are tunable just by adjusting the ratio of the two precursors. The tunable and extendable fabrication process, together with its amazing high carbon yield of 48 wt % (1400 °C) and high tap density close to 0.8 g cm–3, makes this strategy promising in the practical application for SIBs.

Microstructure regulation of resin-based hard carbons via esterification cross-linking for high-performance sodium-ion batteries

“…All samples show two obvious peaks near 1350 cm −1 and 1600 cm −1 , corresponding to the D peak and G peak of carbon materials, respectively. 29 The integral area ratio of the two peaks ( I D / I G ) could be used to quantitatively analyze the structure disordering of carbon materials. In the case of PFC and PC, the I D / I G values were determined to be 1.63 and 1.69, respectively, which then significantly increased to 1.89 for PPFC-1–10–1200 and 1.91 for PPFC-1–6–1200.…”

Unlocking the local structure of hard carbon to grasp sodium-ion diffusion behavior for advanced sodium-ion batteries

“…Moreover, it is noteworthy that sodium ions exhibit the same special diffusion behavior in this voltage region according to reported studies, regardless of the intercalation process or the pore filling process. 26,27 Namely, the sharp drop of the Na + diffusion coefficient and then rise may correspond to another special microstructure in HCs. Therefore, to obtain high plateau capacity, it is particularly important to explore the local microstructure of HCs and reveal Na + diffusion behavior in the low voltage plateau region.…”

Preparation of Hard–Soft Carbon via Co-Carbonization for the Enhanced Plateau Capacity of Sodium-Ion Batteries

“…Recently, resin microspheres with well-ordered microstructures obtained by a ZnO-assisted bulk etching strategy were reported, resulting in an improvement of the reversible capacity to 501 mAh g –1 . Additionally, an economical method combining a highly branched polymer network from resin with lignin was presented, yielding a compound with a high ICE of 88% . Nevertheless, the low plateau capacity of resin-based hard carbon as the anode of SIBs impedes its availability in the commercial market.…”