Rational Design of Perforated Bimetallic (Ni, Mo) Sulfides/N‐doped Graphitic Carbon Composite Microspheres as Anode Materials for Superior Na‐Ion Batteries

Abstract

Highly conductive 3D ordered mesoporous Ni7S6‐MoS2/N‐doped graphitic carbon (NGC) composite (P‐NiMoS/C) microspheres are prepared as anode materials for Na‐ion batteries. The rationally designed nanostructure comprises stable Ni7S6‐ and MoS2‐phases along with the homogeneously distributed ordered mesopores (ϕ = 50 nm) over the external and internal structures generated through thermal decomposition of polystyrene nanobeads (ϕ = 100 nm). Therefore, the P‐NiMoS/C microspheres deliver initial discharge capacities of 662, 419, 373, 300, 231, 181, and 146 mA h g−1 at current densities of 0.5, 1, 2, 4, 6, 8, and 10 A g−1, respectively. Furthermore, P‐NiMoS/C exhibits a stable discharge capacity of 444 mA h g−1 at the end of the 150th cycle at a current density of 0.5 A g−1, indicating higher cycling stability than the filled, that is, non‐mesoporous, Ni3S2‐MoS2/NGC (F‐NiMoS/C) microspheres and filled carbon‐free Ni3S2‐MoS2 (F‐NiMoS) microspheres. The superior electrochemical performance of P‐NiMoS/C microspheres is attributed to the rapid Na+ ion diffusion, alleviation of severe volume stress during prolonged cycling, and higher electrical conductivity of NGC, which results in fast charge transfer during the redox processes. The results in the present study can provide fundamental knowledge for the development of multicomponent, porous, and highly conductive anodes for various applications.

Porous Microspheres Comprising CoSe2 Nanorods Coated with N-Doped Graphitic C and Polydopamine-Derived C as Anodes for Long-Lived Na-Ion Batteries

“…In addition, the cells featuring P-CoSe 2 @NGC NR and bare CoSe 2 hollow microspheres exhibited an initial CE of 52% and 77%, respectively. During the few initial cycles, P-CoSe 2 @PDA-C NRs demonstrated an increase in the capacity mainly due to the formation of polymeric gel-like films on the microsphere surface, as reported previously [35,58,59]. However, as cycling proceeded, the P-CoSe 2 @PDA-C NR had much stable discharge capacities even after prolonged cycling than the P-CoSe 2 @NGC NR and bare CoSe 2 hollow microspheres, which exhibited constant capacity fading.…”

“…Furthermore, the Na-ion diffusion coefficient ( D Na + ) values were calculated from Fig. 7d using the following equation [35,69,70]:…”

“…4d is deconvoluted into five distinct peaks at binding energies of 284.8, 285.6, 286.9, 288.2, and 289.4 eV, corresponding to the C-C(sp 2 ), C-C/C-N, C-O, C=O, and C-O=O species, respectively [12,30,34]. The highest intensity of the C = C peak indicated the graphitic carbon formation during the selenization process [35]. In addition, the presence of C-N/C-C peaks suggested the presence of an N-doped C [8,12].…”

Achieving High-Rate and Stable Sodium-Ion Storage by Constructing Okra-Like NiS2/FeS2@Multichannel Carbon Nanofibers

“…After repeated cycling at 0.2 A g –1 for 20 cycles enabling the slow activation of active materials, the electrode of NiS 2 /FeS 2 @MCNFs presents a reversible capacity of 365 mA h g –1 in the first cycle, which rapidly decays to 346 mA h g –1 in the second cycle and gradually maintains at a level of 342 mA h g –1 with a capacity retention of 93.5% after 1100 cycles. Compared with previously reported Ni-based or Fe-based anodes, ,,− NiS 2 /FeS 2 @MCNFs demonstrates superior long-term cycling performance (Table S2). Meanwhile, NiS 2 /FeS 2 @MCNFs exhibits a reasonably high ICE of 88.5%, which increases to almost 100% in the second cycle and stabilizes at this value during the subsequent cycling process, demonstrating the robust and stable structure of NiS 2 /FeS 2 @MCNFs.…”

N-Doped Graphene Nanofibers with Porous Channel Comprising Fe x S

“…The S-O bond confirmed the surface oxidation of the nanofibers. The C 1s XPS spectrum in Figure 3(c) displays three peaks at binding energies of 284.2, 287.0 eV, and 290.9 eV, assigned to C=C, C-N/C-C, and O-C=O, respectively [14]. The high intensity of the C=C peak confirms the presence of carbon architecture in the prepared nanofibers [18].…”