Structural Analysis of Sucrose-Derived Hard Carbon and Correlation with the Electrochemical Properties for Lithium, Sodium, and Potassium Insertion

Abstract

Hard carbon possesses the ability to store Li, Na, and K ions between stacked sp 2 carbon layers and voids (micropores). We have explored hard carbon as a candidate for negative electrode materials for Li-ion, Na-ion, and K-ion batteries. Hard carbon samples have been prepared by carbonizing sucrose at different heat treatment temperatures (HTTs) in the range of 700−2000 °C to make them structurally suitable for reversible Li, Na, and K insertion. Structures and particle morphology of the hard carbon samples synthesized at different HTTs were systematically characterized using X-ray diffraction, small-angle X-ray scattering, pair distribution function analysis, electron microscopy, Raman spectroscopy, and electron spin resonance spectroscopy. All these characterizations of hard carbon samples have revealed advanced ordering of carbons and reduction of carbon defects with increasing HTT. Thus, the average stacked carbon interlayer distance decreases, the number of the stacking layers increases, the layered domains grow in the in-plane direction, and interstitial voids enlarge. Electrochemical properties of the hard carbons were examined in nonaqueous Li, Na, and K cells. Potential profiles and reversible capacities upon galvanostatic charge/discharge processes in nonaqueous cells are significantly different depending on HTTs and different alkali metal ions. On the basis of these findings, strategies to design high-capacity hard carbon negative electrodes for high-energy-density Li-ion, Na-ion, and K-ion batteries are discussed.

Na‐Ion Batteries—Approaching Old and New Challenges

“…[ 26 ] Recently, Komaba's group has reported a 480 mAh g −1 specific capacity value for a hard carbon prepared by using a MgO template. [ 28,29 ] In any case, for both HCs and SCs, improving the FCCE is still a challenge related to specific surface area and the choice/formulation of the electrolyte.…”

Emerging Potassium‐ion Hybrid Capacitors

“…A comprehensive understanding of hard carbon structures is still a debatable topic because the fact that the disordered structure of hard carbon highly depends on the synthesis conditions such as carbon sources and heat treatment temperatures [91] . The electrochemical potassium insertion highly depends on the microstructural parameters of hard carbon including stacking of carbon layers, micropores, residual heteroatoms, and their defects in the bulk.…”

Impact of Preoxidation Treatments on Performances of Pitch-Based Hard Carbons for Sodium-Ion Batteries

“…63 This is partly the cause of a high irreversibility at first cycle in sodium-ion batteries. 49,63,64 Dangling bonds are also likely inclined to lead to binding with other graphene sheets and therefore to reticulate the structure. 63 We hypothesize that this phenomenon is presumably occurring with the help of the pre-oxidation process which already reticulates the structure by incorporation of oxygen.…”