Conversion Reaction Mechanism of Ultrafine Bimetallic Co‐Fe Selenides Embedded in Hollow Mesoporous Carbon Nanospheres and Their Excellent K‐Ion Storage Performance

Abstract

Potassium‐ion batteries (KIBs) are considered as promising alternatives to lithium‐ion batteries owing to the abundance and affordability of potassium. However, the development of suitable electrode materials that can stably store large‐sized K ions remains a challenge. This study proposes a facile impregnation method for synthesizing ultrafine cobalt–iron bimetallic selenides embedded in hollow mesoporous carbon nanospheres (HMCSs) as superior anodes for KIBs. This involves loading metal precursors into HMCS templates using a repeated “drop and drying” process followed by selenization at various temperatures, facilitating not only the preparation of bimetallic selenide/carbon composites but also controlling their structures. HMCSs serve as structural skeletons, conductive templates, and vehicles to restrain the overgrowth of bimetallic selenide particles during thermal treatment. Various analysis strategies are employed to investigate the charge–discharge mechanism of the new bimetallic selenide anodes. This unique‐structured composite exhibits a high discharge capacity (485 mA h g−1 at 0.1 A g−1 after 200 cycles) and enhanced rate capability (272 mA h g−1 at 2.0 A g−1) as a promising anode material for KIBs. Furthermore, the electrochemical properties of various nanostructures, from hollow to frog egg‐like structures, obtained by adjusting the selenization temperature, are compared.

N‐doped carbon‐coated CoSe 2 nanocrystals anchored on two‐dimensional MXene nanosheets for efficient electrochemical sodium‐ and potassium‐ion storage

“…These results are consistent with those of previous studies. 32,33 The Se 3d spectrum (Figure 4F) exhibits two deconvoluted peaks at 54.2 and 55.6 eV, which correspond to Se 3d 5/2 and Se 3d 3/2 , respectively. The multiple peaks observed in the range of 57 to 64 eV are related to Co 3p and Se─O bonding.…”

Investigation of the potassium‐ion storage mechanism of nickel selenide materials and rational design of nickel selenide‐C yolk‐shell structure for enhancing electrochemical properties

“…The slight weight increase of bare NiSe x until 500 C was due to the oxidation of nickel selenide to the nickel selenite phase. 49 The following weight decline step of bare NiSe x was relevant to the evaporation of the selenium oxide component formed by the decomposition of nickel selenite and direct transformation into nickel oxide under air. Conversely, NiSe x @C showed an additional weight decline step, corresponding to the combustion of the carbon component at approximately 400 C. NiSe x @C and bare NiSe x were expected to have different ratios of NiSe 2 and Ni 0.85 Se because a more inert atmosphere could be formed when they are heat treated while impregnated with hollow and porous carbon nanospheres.…”

Role of binary metal chalcogenides in extending the limits of energy storage systems: Challenges and possible solutions

“…For example, the porous Co 8 FeS 8 /N-C dodecahedral nanocages were fabricated by employing ZIF-67 as a template followed by pyrolysis and sulfuration routes, in which Co 8 FeS 8 nanoparticles were embedded into N-doped carbon matrix [113]. Recently, hollow mesoporous carbon spheres (HMCSs) as templates have been proposed for the impregnation/infiltration method to obtain BMCs/carbon hybrids [115,116]. Yang et al [115] proposed a novel impregnation approach for the fabrication of ultrafine cobalt-iron selenides embedded in HMCSs.…”

“…Recently, hollow mesoporous carbon spheres (HMCSs) as templates have been proposed for the impregnation/infiltration method to obtain BMCs/carbon hybrids [115,116]. Yang et al [115] proposed a novel impregnation approach for the fabrication of ultrafine cobalt-iron selenides embedded in HMCSs. In this strategy, HMCSs acting as substrates were first prepared by the templating process that produced several mesopores in the shell and a huge void space (Fig.…”

“…For example, hollow mesoporous carbon nanospheres embedded with ultrafine cobalt iron selenides were reported as an anode material for PIBs. The as-made hybrid structure showed a high specific capacity (485 mA h g −1 after 200 cycles at 100 mA g −1 ) and excellent rate performance (272 mA h g −1 at 2000 mA g −1 ) [115]. The ultrafine bimetallic selenides confined within abundant pores not only mitigate the volume expansion but also prohibit the aggregation of nanoparticles, whereas hollow mesoporous carbon nanospheres act as conductive templates and structural skeletons.…”