Hard Carbon Anodes for Na‐Ion Batteries: Toward a Practical Use

Abstract

Hard carbons have immense potential as anode materials for Na‐ion batteries, because the expanded graphene interlayers and nanovoids between randomly stacked aromatic fragments can accommodate a substantial amount of sodium. However, the large irreversible capacity in the first cycle still remains as a significant issue in terms of a practicable battery technology. Here, we show that hard carbon electrodes derived from a common phenol resin deliver a high reversible capacity within the narrow potential range of 0.1–0.005 V (vs. Na+/Na) and an excellent initial coulombic efficiency up to 95 %. The former allows the sustainable high voltage, whereas the latter minimizes the amount of unavailable Na+ in a closed cell. The findings in this work put forward a guideline for manufacturing hard carbon electrodes, which goes against the current trend of nanostructuring and downsizing.

Structural and Electrochemical Properties of Hard Carbon Negative Electrodes for Sodium Secondary Batteries Using the Na[FSA]–[C₃C₁pyrr][FSA] Ionic Liquid Electrolyte

“…The comparison of d 002 and Q slope values naturally leads to the conclusion that HC with a larger d 002 value shows a higher capacity. 19 Concerning the plateau region, larger D pore gives higher Q plateau values, which is consistent with the previous studies conducted in organic solvent-based electrolytes. 20 Moreover, HC-1 has smaller pores of D pore < 0.5 nm (See Fig.…”

“…5,6 For example, several positive electrode materials like We have also investigated the charge-discharge behavior of hard carbon (HC) negative electrodes in this ionic liquid at 363 K. 10,11 HC is mainly composed of two structural domains, i.e., randomly-arranged graphene domains and their interstitial sites (pores), and its charge-discharge behavior as a negative electrode material for sodium secondary batteries has been well investigated in organic solvent electrolytes. [12][13][14][15][16][17][18][19][20] However, there have been few studies on the correlation of HC structure and its electrochemical behavior in ionic liquid electrolytes.…”

Extended “Adsorption–Insertion” Model: A New Insight into the Sodium Storage Mechanism of Hard Carbons

“…[58,65,66] To illustrate these phenomena, we propose an extended "adsorption-insertion" model to comprehensively understand the sodium storage mechanism of HCs. For example, the highly disordered GL-600 with d 002 > 0.40 nm exhibits only sloping capacity.…”

Microsized Sn as Advanced Anodes in Glyme‐Based Electrolyte for Na‐Ion Batteries

“…Developing high performance anodes are urgently required for Na-ion batteries in order to catch up the energy density of Li-ion batteries. At this stage, research efforts are devoted to two directions: one is aiming at increasing the capacity and decreasing the average potential of hard carbon by tailoring its microstructure, [9][10][11][12] while considerable work are also conducted on searching for new candidates among which alloy anodes are most attractive.…”