Facile Fabrication of Co₉S₈ Embedded in a Boron and Nitrogen Co‐Doped Carbon Matrix as Sodium‐Ion Battery Anode

Abstract

A unique composite (Co 9 S 8 @BNC) consisting of cobalt sulfide (Co 9 S 8 ) embedded in a boron and nitrogen co-doped carbon matrix (BNC) is successfully synthesized as anode material for sodium-ion batteries (SIBs). The BNC matrix was demonstrated to improve the electronic and ion diffusion speed, as well as help buffer the dramatic volumetric expansion during the repeated cycling processes. Benefited from the advantages of BNC matrix, Co 9 S 8 @BNC delivered a high initial reversible capacity of 494 mAh · g À 1 at 100 mA · g À 1 and could remain 388 mAh · g À 1 after 100 cycles. Apart from that, it exhibited an excellent rate performance (258 mAh · g À 1 at the current density of 2 A · g À 1 ) and was demonstrated as pseudocapacitive charge storage. As a consequence, the as-prepared Co 9 S 8 @BNC possesses an exceptional electrochemical performance and could be utilized as a potential anode material candidate for SIBs.[a] T.issues during repeated sodiation processes. The as-made Co 9 S 8 @BNC composite delivered an ultrahigh reversible capacity of 387.8 mAh · g À 1 after 100 cycles, which was better than other materials of Co 9 S 8 combined with another carbon matrix. The present work opens up an efficacious avenue for designing stable B/N co-doped carbon with metal sulfide hybrids for the potentially high-performance SIBs materials combining high energy storage capacity and stability.

Stabilising Cobalt Sulphide Nanocapsules with Nitrogen-Doped Carbon for High-Performance Sodium-Ion Storage

“…The obtained electrode material (hereafter designated as Co 9 S 8 @NC) was used as anode for sodium-ion storage. It delivered a specific capacity as high as 705 mAh g −1 at 100 mA g −1 and exhibited an excellent rate performance (613 mAh g −1 at 4000 mA g −1 ), which is among the highest in all reported Co 9 S 8 electrodes for NIBs [4,5,[19][20][21][22]. Insight into sodium storage mechanism in Co 9 S 8 @NC is systematically studied and discussed via multiple analytical methods.…”

Optimization of Sodium Storage Performance by Structure Engineering in Nickel‐Cobalt‐Sulfide

“…When the current density was returned to 200 mA g −1 , the 3 % Mn‐NCS@GNs electrode retained a capacity of 310.5 mAh g −1 after 200 cycles. This superior rate performance of the 3 %Mn‐NCS@GNs electrode is better than that of previously reported electrodes in ether electrolyte for SIBs, as shown in Figure 3g [45–49] . Additionally, the 3 % Mn‐NCS@GNs electrode maintained a small R ct of 8.52 Ω and faster D $${{_{{\rm Na}{^{+}}}}}$$ (1.79×10 −11 cm 2 s −1 ) after the rate performance test (Figure S12), indicating the 3 % Mn‐NCS@GNs electrode provides better diffusion kinetic during charging and discharging, thus ensuring excellent rate performance.…”

“…This superior rate performance of the 3 %Mn-NCS@GNs electrode is better than that of previously reported electrodes in ether electrolyte for SIBs, as shown in Figure 3g. [45][46][47][48][49] Additionally, the 3 % Mn-NCS@GNs electrode maintained a small R ct of 8.52 Ω and faster D Na þ (1.79 × 10 À 11 cm 2 s À 1 ) after the rate performance test (Figure S12), indicating the 3 % Mn-NCS@GNs electrode provides better diffusion kinetic during charging and discharging, thus ensuring excellent rate performance. Structural engineering was also found to be beneficial in maintaining the structural stability of the electrode material during the charging and discharging process, as shown in Figure S13.…”

Nitrogen and Sulfur Vacancies in Carbon Shell to Tune Charge Distribution of Co6Ni3S8 Core and Boost Sodium Storage

“…[5] However, Co 9 S 8 usually suffers from inferior electronic conductivity and severe volume expansion, resulting in unsatisfactory actual specific capacity and cycling performance. [6] Various approaches have been proposed to address these issues, such as building carbon-based composites, [7,8] optimization of the electrolytes, [9,10] innovative design of material microstructures. [11,12] Among these methods, porous carbon host have considerable potential because they cannot only restrain the volume expansion, but also keep Co 9 S 8 electrically connected.…”

“…[13,14] However, the cycling life is still dissatisfactory (typically <100 cycles) and does not meet the requirements of industrial practical application. [7,8,13,14] In order to improved cycling performance in sodium storage, two key factors need to be considered: 1) the poor interaction between highly polar hydrophilic Co 9 S 8 and intermediate product of polysulfides on nonpolar hydrophobic carbon matrix expedites the capacity fading; 2) the severe volume expansion of Co 9 S 8 crystal during repeated cycling also leads to poor cycling stability. For the first point, nitrogen-doped carbon materials have been proved to have strong chemisorption capacity for Li 2 S and polysulfides.…”