Recent Progress in Amorphous Carbon‐Based Materials for Anodes of Sodium‐Ion Batteries: Synthesis Strategies, Mechanisms, and Performance

Abstract

Sodium‐ion batteries (SIBs) are gaining renewed interest as a promising alternative to the already commercialized lithium‐ion batteries. The large abundance, low cost, and similar electrochemistry of sodium (compared with lithium) is attracting the attention of the research community for their deployment in energy storage devices. Despite the fact that there are adequate cathode materials, the choice of suitable anodes for SIBs is limited. Graphite, the most versatile anode for LIBs, exhibits poor performance in case of SIBs. Amorphous or disordered carbons (hard and soft carbon) have been the most promising and cost‐effective anode materials for SIBs. This Review discusses the recent advances of various forms of amorphous or disordered carbons used in SIBs with emphasis on their synthesis processes and relationship between microstructure, morphology, and performance. A profound understanding of the charge storage mechanisms of sodium in these carbon materials has been deliberated. The performance of these anode materials also depends upon electrolyte optimization, which has been aptly conferred. However, these anodes are often plagued with large voltage loss, low initial coulombic efficiency, and formation of solid electrolyte interphase. In order to overcome these challenges, several mitigation strategies have been put forward in a concise way to offer visions for the deployment of these amorphous carbon materials for the progress and commercial success of SIBs.

Synthesis Strategies and Applications for Pitch‐Based Anode: From Industrial By‐Products to Power Sources

“…In addition, the imperfect crystallite structure will lead to low conductive ability [93] . As a result, it is crucial to control the degree of activation [32] …”

“…SC, derived from coal, petroleum, and pitch, has higher carbon content, lower prices, easier graphitization, and better conductivity than HC. Meanwhile, it still exhibits a larger theoretical capacity than graphite, [28–30] making it promising for high‐performance electrode precursors [31,32] . SC's molecules have low van der Waals forces, [33–35] and its degree of graphitization and the distance between carbon layers can be adjusted by heat treatment [36–39] …”

In‐situ nano‐engineering of amorphous MoS 2 nanosheets with carbon dots for enhanced supercapacitor performances

“…It is thus interesting to develop amorphous 2D electrode materials for energy applications. Although the 2D amorphous carbon, 13 amorphous phosphorous, 14 etc., for energy storage and conversion applications are reported in literature, very few reports are available for other amorphous materials. [15][16][17] According to the theoretical prediction, depending upon the arrangement of "S"-atoms, MoS 2 exists in two different symmetries that is, 2H and 1T having trigonal prismatic (D 3h ) and octahedral (O h ) geometry, respectively.…”

“…It is thus interesting to develop amorphous 2D electrode materials for energy applications. Although the 2D amorphous carbon, 13 amorphous phosphorous, 14 etc., for energy storage and conversion applications are reported in literature, very few reports are available for other amorphous materials 15‐17 …”

Investigation of pyrolysed anthracite as an anode material for sodium ion batteries

“…20 However, graphite shows electrochemical inactivity in SIBs due to the large radius and low diffusion kinetics of Na + . 21,22 In order to solve this problem, a large number of carbon materials have been studied for SIBs in recent years, such as amorphous carbon (soft carbons, 23 hard carbons 24 and hybrid carbons 25 ), doping heteroatoms (sulfur-doped carbon 26 and N-doped carbon 27 ), and diversified shapes (carbon nanotubes, 28 expanded graphite 29 and porous carbon 30 ). Since the first report, hard carbon materials have attracted much attention due to their high specific capacity, sodium intercalation at voltages below 0.1 V and excellent cycling performance.…”