Electrochemical Insertion of Sodium into Carbon

Synthetic Metals, 1997

Electrochemical intercalation of sodium ions into poly(para-phenylene) (PPP) has been carried out in NaCIO4-carbonate electrolytes (EC, PC and their mixture in the volumic ratio of 1 / 1). The same electrochemical behavior has been observed in the three electrolytes. The galvanostatic curves exhibit potential slope changes which are characteristic of multiphase system; this behavior is confirmed by cyclic voltammetry. Our experimental conditions allow the obtainment of lich compounds Nao.5(CdH4) which do not contain co-inserted solvent molecules. This is due to a passivating layer formed at the electrode surface during the first dischapge that prevents the co-insertion of solvent. Analysis of this layer by transmission electron microscopy reveals the presence of Na2CO3 at potentials higher than 0.75 V and sodium alkylcarbonates at potentials lower than 0.75 V. A two-step mechanism of electrolyte decomposition is proposed by analogy with the case of the reduction of graphite in carbonate electrolytes containing LiC10., salt.

Journal of materials chemistry. A, Materials for energy and sustainability, 2017

Physical Chemistry Chemical Physics, 2014

The present study compares the physico-chemical properties of non-aqueous liquid electrolytes based on NaPF 6 , NaClO 4 and NaCF 3 SO 3 salts in the binary mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). The ionic conductivity of the electrolytes is determined as a function of salt concentration and temperature. It is found that the electrolytes containing NaClO 4 and NaPF 6 exhibit ionic conductivities ranging from 5 mS cm À1 to 7 mS cm À1 at ambient temperature. The electrochemical stability window of the different electrolytes is studied by linear sweep voltammetry (LSV) and cyclic voltammetry (CV) measurements with respect to a variety of working electrodes (WE) such as glassy carbon (GC), graphite and a carbon gas diffusion layer (GDL). Electrolytes containing NaPF 6 and NaClO 4 are found to be electrochemically stable with respect to GC and GDL electrodes up to 4.5 V vs. Na/Na + , with some side reactions starting from around 3.0 V for the latter salt. The results further show that aluminium is preferred over different steels as a cathode current collector. Copper is stable up to a potential of 3.5 V vs. Na/Na +. In view of practical Na-ion battery systems, the electrolytes are electrochemically tested with Na 0.7 CoO 2 as a positive electrode. It is inferred that the electrolyte NaPF 6-EC : DMC is favorable for the formation of a stable surface film and the reversibility of the above cathode material.

Energy & Environmental Science, 2020

Sodium filling inside hard carbon pores demonstrates increasingly metallic character with increasing pore size.

Advanced Materials, 2019

and Technology. His research focuses on designing carbon materials for electrochemical applications such as fuel cells, capacitive deionization, supercapacitors, and batteries.

Israel Journal of Chemistry, 2015

Energy Materials, 2025

With the advantages of simple preparation, cost-effectiveness, abundant raw materials, and environmentally friendly properties, hard carbon is the only commercially available anode material for sodium-ion batteries. However, its unstable capacity is attributed to the complex physicochemical characteristics of the precursors, the intricate and difficult-to-control microstructure, and the debated mechanisms of sodium storage. Although recent reports have revealed a strong correlation between closed pores and the capacity of hard carbon in the low-voltage plateau region, systematic overviews of this relationship remain scarce. This review examines the microstructural properties and precursor selectivity of hard carbon materials and outlines the strategies for the research and development of closed pores, including design theory and characterization. Finally, it summarizes the technical bottlenecks faced by the closed pore research and looks forward to the future development directions.

Journal of Energy Chemistry, 2020

Carbon-based materials have attracted much interest as one of the promising anodes for sodium-ion batteries. However, low utilization of electrolyte and slow ion-transfer rate during electrochemical process hinder the further application of traditional bulk carbon. In order to enhance the diffusion kinetics and maintain the reversibility, hierarchical hollow carbon microbox was successfully prepared through a tunable bottom-up self-template routine for sodium-ion batteries. During annealing process, the morphology construction and activation happened synchronously. Based on that, a range of cross-linked porous nanosheet and hollow microbox were attained by manipulating reactant condition. The generation of texture and physical property are analyzed and are established linkages related to the electrochemical behavior. As results depicted in kinetic exploration and simulation based on cyclic voltammetry, the surfacecontrolled electrochemical behavior gradually turns to be the diffusion-controlled behavior as the hollow microbox evolves to porous nanosheet. The probable reason is that the rational microstructure/texture design leads to the accelerated diffusion kinetic procedure and the reduced concentration difference polarization. Sodium storage mechanism was deduced as reversible binding of Na-ions with local defects, including vacancies on sp 2 graphitic layers, at the edges of flakes and other structural defects instead of intercalation. Bestowed by the morphology design, the broad pore width distribution, abundant defects/active sites and surface functionality, hollow microbox electrode delivers great electrochemical performances. This work is expected to propose a novel and effective strategy to prepare tunable hierarchical hollow carbon microbox and induce the fast kinetic of carbon anode material.

Chemistry of Materials, 2018

This paper utilizes density functional theory calculations to explore amorphous carbon materials, and concludes that the theoretical capacity is between 300 and 400 mAh g -1 , depending on the degree of defects. This conclusion arises from a comprehensive number of simulations used to validate the experimentally determined storage mechanism, with these results then being extrapolated to elucidate a theoretical capacity limit. Through investigating the breadth of structures, with multiple Na configurations, the studies lead to four major conclusions. First, we found that the nature of Na storage in carbon materials changes with increasing Na concentrations in a continuum from ionic storage to metallic plating. Second, we revealed the critical role of the intersheet spacing, stacking misalignment, and effects of spacing expansion on the feasibility of Na intercalation into graphitic structures. This leads to the third and fourth conclusion, which stipulates that the results provided here offer compelling support towards an earlier experimentally derived Na ion storage for hard carbon materials, along with the existence of a theoretical limit of sodium ion storage in hard carbon materials. Moreover, the techniques and scope of the work involved are highly relevant to future simulations exploring amorphous carbon as an active material, whether it should be for Li-ion battery anodes, supercapacitors, or catalysts.

Advances in physics research, 2022

This study investigated the properties of mesocarbon anodes in the half-cell of sodium-ion batteries. The behavior of mesocarbon was examined using electrochemical methods. Cyclic voltammetry (CV) was applied with various scan rates to reveal the anodic-cathodic voltage and peak current. The CV profile allowed for predicting the energy storage mechanism of sodium ions in mesocarbon. The CV measurement of the half-cell Na | mesocarbon demonstrated the intercalation and de-intercalation of sodium ions in the graphene interlayer at 0.01 V and 0.12 V, respectively. Based on the Power law, the kinetics of sodium ion movement was controlled by the diffusion-dominant reaction. After 25 cycles, the electrochemical impedance spectroscopy (EIS) spectra exhibited increasing resistances in the solid-electrolyte interface (R SEI ) and charge transfer (Rct), ranging from 53.8 to 65.6 and 42.6 to 229 , respectively. Considering the charge/discharge rate capability in the first five cycles, the mesocarbon could deliver a specific capacity of discharge of 42 mAh/g at 0.1 C and retain 73% of its capacity after 25 cycles.