One-dimensional Fe7S8@C nanorods as anode materials for high-rate and long-life lithium-ion batteries

Kong

et al. 2019

Adv Elect Materials

nevertheless, they usually put undue emphasis on the capacity of the positive electrode, instead. There are few reports that discuss the negative electrode materials relatively. As a result, the capacity of the negative electrodes is much lower than that of the positive electrodes, and the capacity mismatch between the positive and negative electrodes is more serious. [6] As a matter of fact, similar to "cask effect," the capacity of the negative electrode is the shortest plank for supercapacitor, which decides how much energy capacity the supercapacitor can store. In other words, the way that can increase the capacity of the negative electrode materials, can remedy the low energy density deficiency of supercapacitor. [7] Looking at what predecessors have been developed for constructing the supercapacitor negative electrode, carbon and Fe-based materials are two major electrodes that can be utilized. [8][9][10] Due to the redox characteristic of Fe-based materials, it is believed to have the higher theoretical capacity compared with carbon materials that presents double layer capacitance characteristics. [11] To our disappointment, the poor electrical conductivity, which affects the efficiency of electronic transmission, resulted in low supercapacitor performance embodiment, far less than what was expected. [12,13] Therefore, how to improve the electrical conductivity to enhance the efficiency of electron transfer is the most important factor when designing and fabricating an Fe-based negative electrode material. [14] To address this challenge, one of the strategies is to fabricate composites with carbon materials. [4,15] On account of the excellent electrical conductivity of carbon materials, the Fe-based compand/carbon composites show good electrical conductivity. However, the low theoretical capacity of carbon materials limits the capacity promotion of Fe-based compand/ carbon composites. Another method is to rationally design a hierarchical nanostructure. [5,14,16,17] Core-shell structure is believed to be a good choice, where materials with good electrical conductivity are used as the core and materials with high theoretical capacity are used as the shell. [13,[18][19][20] Therefore, the good electrochemical performance has been ascribed to its unique structure, which endows the electrode with large specific area and facilitates the contact between the electrode and The shortcoming of Fe-based materials, their poor electron transfer efficiency, restricts their electrochemical performance severely. An electric field (E) is induced by an Fe 7 S 8 /α-FeOOH nano-heterostructure (SACF) via two simple immersion steps at room temperature. The charge transfer from α-FeOOH to Fe 7 S 8 spontaneously establishes an intrinsic electric field at the Fe 7 S 8 /α-FeOOH nano-heterostructure boundary. Additionally, the relationship between structure and property is investigated by structural characterization and density functional theory calculations that are used to explain the electron transfer mechanism and good wettabilit...

Section: Resultssupporting

confidence: 77%

Electric‐Field‐Assisted Enhanced Electron Transfer to Boost Supercapacitor Negative Electrode Performance for a Fabricated Fe₇S₈/α‐FeOOH Nano‐Heterostructure

Kong

et al. 2019

Adv Elect Materials

Chemistry An Asian Journal

“…So far, many strategies including downsizing the particle size to fabricate hierarchical nanostructures, constructing composites with conductive carbon matrix, and integration with heterogeneous hybrids to shorten electronic and ionic transport paths, alleviate the internal strain, improve the electrical conductivity, and accommodate the volume changes during cycling, have been devoted to promote the lithium storage performance of metal sulfides. Among these effective approaches, construction of heterostructures consisted of different components with bandgaps difference, is an effective way to promote the electrochemical performance, which could generate a strong built‐in electric field ( E ‐field), promote interface charge transport of ions and electrons, thus improving the reaction kinetics .…”

Section: Introductionmentioning

confidence: 99%

Bimetal‐organic Framework‐derived Co₉S₈/ZnS@NC Heterostructures for Superior Lithium‐ion Storage

Duan

Wang

et al. 2020

Heterostructure engineering of electrode materials, which is expected to accelerate the ion/electron transport rates driven by a built-in internal electric field at the heterointerface, offers unprecedented promise in improving their cycling stability and rate performance. Herein, carbon nanotubes with Co 9 S 8 /ZnS heterostructures embedded in a N-doped carbon framework (Co 9 S 8 /ZnS@NC) have been rationally designed via an in-situ vapor chemical transformation strategy with the aid of thiophene, which not only acted as carbon source for the growth of carbon nanotubes but also as sulfur source for the sulfurization of metal Zn and Co. Density functional theory (DFT) calculation shows an about 3.24 eV electrostatic potential difference between ZnS and Co 9 S 8 , which results in a strong electrostatic field across the interface that makes electrons transfer from Co 9 S 8 to the ZnS side. As expected, a stable cycling performance with reversible capacity of 411.2 mAh g À 1 at 1000 mA g À 1 after 300 cycles, excellent rate capability (324 mAh g À 1 at 2000 A g À 1 ) and a high percentage of pseudocapacitance contribution (87.5% at 2.2 mv/s) for lithium-ion batteries (LIBs) are achieved. This work provides a possible strategy for designing multicomponent heterostructural materials for application in energy storage and conversion fields.[a] Prof.

Advanced Sustainable Systems

“…Meanwhile, the deconvoluted peaks at 163.40, 162.25, and 161.24 eV are assigned to S 2− . [ 42 ] Thus, the XPS result further confirms that the composition (Fe 2 O 3 and Fe 7 S 8 ) of OV‐Fe‐DES, agreeing well with the XRD and energy dispersive spectroscopy (EDS) mapping result.…”

Section: Resultsmentioning

confidence: 99%

Deep Eutectic Solvent‐Mediated Construction of Oxygen Vacancy‐Rich Fe‐Based Electrocatalysts for Efficient Oxygen Evolution Reaction

Liu

Chen

Hao

et al. 2020

Fe‐based catalysts are promising candidates for water splitting due to the abundant reserves of Fe. However, their electrocatalytic performance toward the oxygen evolution reaction (OER) is still unsatisfactory. Herein, a new hybrid catalyst of Fe7S8/Fe2O3 is designed via a deep eutectic solvent (DES)‐based strategy. The Fe7S8/Fe2O3 particles are in a porous nanosheet structure and possess oxygen vacancy‐rich characteristics. The porous nanosheet structure and oxygen vacancy‐rich Fe2O3 in the Fe7S8/Fe2O3 significantly improves the electrocatalytic activity toward the OER. The as‐prepared Fe7S8/Fe2O3 nanosheets demonstrate a small overpotential of 229 mV at a current density of 10 mA cm−2 with a small Tafel slope of 49 mV dec−1, which outperform most of the state‐of‐the‐art Fe‐based catalysts. This work not only reports a new Fe‐based electrocatalyst with an improved performance toward the OER but also provides a rational DES‐based strategy for construction of advanced catalysts.