Encapsulating Trogtalite CoSe₂ Nanobuds into BCN Nanotubes as High Storage Capacity Sodium Ion Battery Anodes

Abstract

Trogtalite CoSe2 nanobuds encapsulated into boron and nitrogen codoped graphene (BCN) nanotubes (CoSe2@BCN‐750) are synthesized via a concurrent thermal decomposition and selenization processes. The CoSe2@BCN‐750 nanotubes deliver an excellent storage capacity of 580 mA h g−1 at current density of 100 mA g−1 at 100th cycle, as the anode of a sodium ion battery. The CoSe2@BCN‐750 nanotubes exhibit a significant rate capability (100–2000 mA g−1 current density) and high stability (almost 98% storage retention after 4000 cycles at large current density of 8000 mA g−1). The reasons for these excellent storage properties are illuminated by theoretical calculations of the relevant models, and various possible Na+ ion storage sites are identified through first‐principles calculations. These results demonstrate that the insertion of heteroatoms, B–C, N–C as well as CoSe2, into BCN tubes, enables the observed excellent adsorption energy of Na+ ions in high energy storage devices, which supports the experimental results.

Golden Bristlegrass‐Like Hierarchical Graphene Nanofibers Entangled with N‐Doped CNTs Containing CoSe2 Nanocrystals at Each Node as Anodes for High‐Rate Sodium‐Ion Batteries

“…For both samples, the cathodic peak at ≈0.78 V was assigned to the formation of metallic Co nanocrystals and Na 2 Se due to the conversion reaction between the Na + and CoSe 2 during the first discharging process. [30,43,44] In the first charging process, two anodic peaks at 1.84 and 1.96 V were observed owing to the restoration of metallic Co and Na 2 Se into CoSe 2 nanocrystals. [30,43,44] From the second cycle onward, two cathodic peaks were observed at 1.41 and 1.11 V, corresponding to the insertion of Na + into CoSe 2 .…”

“…[30,43,44] In the first charging process, two anodic peaks at 1.84 and 1.96 V were observed owing to the restoration of metallic Co and Na 2 Se into CoSe 2 nanocrystals. [30,43,44] From the second cycle onward, two cathodic peaks were observed at 1.41 and 1.11 V, corresponding to the insertion of Na + into CoSe 2 . [30,43,44] The peak shift to higher potential from the second cycle is due to the formation of ultrafine CoSe 2 nanocrystals after the first cycle.…”

“…[30,43,44] From the second cycle onward, two cathodic peaks were observed at 1.41 and 1.11 V, corresponding to the insertion of Na + into CoSe 2 . [30,43,44] The peak shift to higher potential from the second cycle is due to the formation of ultrafine CoSe 2 nanocrystals after the first cycle. [6,29] The other cathodic peak at 0.7 V was assigned to the conversion reaction with further Na + insertion.…”

“…[6,29] The other cathodic peak at 0.7 V was assigned to the conversion reaction with further Na + insertion. [30,43,44] The discharge and charge curves of the samples for the first and second cycles at a current density of 0.5 A g −1 are shown in Figure 6c,d. In the initial discharge curve, the N-CNT/rGO/CoSe 2 NF exhibited sloped charge/discharge profiles and a comparatively short plateau at ≈0.89 V compared with the bare CoSe 2 -filled NF owing to the ultrafine crystallite size of the CoSe 2 .…”

In‐Situ Fabrication of Bone‐Like CoSe2 Nano‐Thorn Loaded on Porous Carbon Cloth as a Flexible Electrode for Na‐Ion Storage

“…[14,27] The distinct anodic peaks appearing on desodiation process at 1.90 V are pertaining to the recombination of Co nanoparticles and Na 2 Se into CoSe 2 . [28,29] The first three galvanostatic charge-discharge profiles of BLÀ CoSe 2 /PCC and CoSe 2 /CC present first discharge capacity of 1259.5 and 704.7 mAh g À 1 with an initial coulombic efficiency (CE) of 43.9 and 56.9%, respectively, at a current density of 0.1 A g À 1 (Figure 5b and S12). The large capacity loss and low CE at initial cycle are primarily attribute to the formation of SEI layer and electrolyte decomposition.…”