Hierarchical Hollow‐Microsphere Metal–Selenide@Carbon Composites with Rational Surface Engineering for Advanced Sodium Storage

Abstract

As a result of its high‐energy density, metal–selenides have demanded attention as a potential energy‐storage material. But they suffer from volume expansion, dissolved poly‐selenides and sluggish kinetics. Herein, utilizing' thermal selenization via the Kirkendall effect, microspheres of NiSe2 confined by carbon are successfully obtained from the self‐assembly of Ni‐precursor/PPy. The derived hierarchical hollow architecture increases the active defects for sodium storage, while the existing double N‐doped carbon layers significantly alleviate the volume swelling. As a result, it shows ultrafast rate capability, delivering a stable capacity of 374 mAh g−1, even after 3000 loops at 10.0 A g−1. These remarkable results may be ascribed to the NiOC bonds on the interface of NiSe2 and the carbon film, which leads to the faster transfer of ions, the effective trapping of poly‐selenide, and the highly reversible conversion reaction. The kinetic analysis of cyclic voltammetry (CV) demonstrates that the electrochemical process is mainly dominated by pseudocapacitive behaviors. Supported by the results of electrochemical impedance spectroscopy (EIS), it is confirmed that the solid–electrolyte interface films are reversibly formed/decomposed during cycling. Given this, this elaborate work might open up a potential avenue for the rational design of metal‐sulfur/selenide anodes for advanced battery systems.

Electrodeposited Binder‐Free Antimony−Iron−Phosphorous Composites as Advanced Anodes for Sodium‐Ion Batteries

“…The ‘b’ values of the Sb 47 Fe 39 P 14 electrode are 0.93, 0.78, and 0.85 for peaks 1, 2, and 3, respectively, which are in the range of 0.7–1.0, indicating the combination of primary pseudocapacitive and secondary solid‐state diffusion contributions. Meanwhile the ‘b’ values of the Sb 18 Fe 58 P 24 electrode are 0.63, 0.59, and 0.62 for peaks 1, 2, and 3, respectively, which are in range of 0.5–0.7, indicating the combination of primary solid‐state diffusion and secondary pseudocapacitive contributions . The rate capabilities of both Sb 47 Fe 39 P 14 and Sb 18 Fe 58 P 24 electrodes stem from the synergistic combinations of solid‐state diffusion and pseudocapacitive behavior.…”

“…Meanwhile the 'b' values of the Sb 18 Fe 58 P 24 electrode are 0.63, 0.59, and 0.62 for peaks 1, 2, and 3, respectively, which are in range of 0.5-0.7, indicating the combination of primary solid-state diffusion and secondary pseudocapacitive contributions. [49,50] The rate capabil- ities of both Sb 47 Fe 39 P 14 and Sb 18 Fe 58 P 24 electrodes stem from the synergistic combinations of solid-state diffusion and pseudocapacitive behavior. However, the pseudocapacitive contribution in the Sb 47 Fe 39 P 14 electrode is greater than that in the Sb 18 Fe 58 P 24 electrode, further confirming that the rate capability of the Sb 47 Fe 39 P 14 electrode is superior to that of Sb 18 Fe 58 P 24 electrode.…”

Hierarchical Hollow‐Nanocube Ni−Co Skeleton@MoO3/MoS2 Hybrids for Improved‐Performance Lithium‐Ion Batteries

“…The reversible specific capacity of the NCM-NC hybrids is recovered to 1002 mAh g À1 after 186 cycles.T he highly overlapping charge-discharge platforms show that the NCM-NCh ybridsh ave better reversibility and excellent electrochemical stability. [47] As shown in Figure 6a,t he NCM-NC electrode delivers an outstanding rate performance, with average discharge capacities of 1016, 930, 847, 766, 704, and 661 mAh g À1 at 0.2, 0.3, 0.4, 0.6, 0.8, and 1.0 Ag À1 ,respectively.Ifthe current density recoverst o0 .2 Ag À1 ,t he discharge specific capacity can still reach 914 mAh g À1 .C ompared with NCM-NC hybrids,t he rate capacities of M-NF and NiÀCo skeleton electrodes are relatively low.T he rate capacities of NCM-NC hybridsa re close to about 1.3 times that of M-NFs at various current densities, and the extra capacity of about 120 mAh g À1 could be assigned to the contribution of the NiÀCo skeletons (Figure6b). Additionally,t he discharge platformso ft he NCM-NC and M-NF electrodes shift to lower voltages at high current density,w hich implies that more electrons are congested on the surfaceo ft he electrode (FigureS6b,c in the Supporting Information).…”

“…[10,16] Additionally,t he peak at about 1.88 Vi s attributed to the oxidation of Mo to MoO 3 [Eq. [47] Understanding the lithium-storage mechanism of anode materials (especially hybrids) is extremelys ignificant to basic research and applicationo fL IBs. (12)].…”

“…After 200 cycles, the specific capacities of the hollow NiÀCo skeletons exhibited ac learly increasing trend (Figure S7 bi nt he Supporting Information). [47] 3) Upon reachingt oah igher lithium-ion-storage level, the partially reversible lithium alkyl carbonate of the SEI layers could be deemeda sl ithium-ion reservoirs (theoretical capacity of lithium alkyl carbonate:E tOCO 2 Li (ethyl carbonate) is 279.1 mAh g À1 ,M tOCO 2 Li (methyl carbonate)i s 326.9 mAh g À1 ). However,t he specific capacity of the NCM-NC hybrids is continuously reduced to 706.9 mAh g À1 duringt he first 80 cycles.…”