Structural fabrication and modification are the effective approaches to regulate the electrochemical performances of anatase TiO2. Herein, the template-annealing-etching processes are carried out to ...synthesize inverse opal TiO2 with N-doped carbon layer and oxygen vacancies surface as an anode material for advanced lithium ion batteries and sodium ion batteries. These structural features not only shorten the diffusion paths and enhance the electronic conductivity, but also induce the dominant pseudocapacitive contribution. As a result, the as-prepared electrode exhibits the excellent Li+/Na+ storage performances, including a high capacity retention (462 mAh g−1 after 300 cycles at 0.5 A g−1) and a fast cycling capability (180 mAh g−1 after 3500 cycles under 10 A g−1) for lithium storage; a reversible capacity of 140 mAh g−1 after 400 cycles under 1 A g−1 for sodium storage. Revealed by cyclic voltammetry, the pseudocapacitive contribution is as high as 74.49% and 73.38% at 1 mV s−1 for lithium ion batteries and sodium ion batteries, respectively. This work may promise a general approach to synthesize metal oxides anode materials for advanced energy storage devices.
Cerium fluoride (CeF3) coated lithium-rich layered Li1.2Mn0.54Ni0.13Co0.13O2 particles are synthesized using a facile chemical deposition route. The structural and electrochemical properties of ...pristine and CeF3-coated electrodes are investigated by X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), galvanostatic charge/discharge tests, electrochemical impedance spectra (EIS) and cyclic voltammetry (CV). The results indicate that the cathode particles are uniformly covered with a CeF3 layer (∼10 nm thick) after 2 wt.% CeF3 surface coating. The coated electrode shows an enhanced initial coulombic efficiency of 80.8% compared to 75.2% for the pristine electrode. Moreover, the coated electrode demonstrates better cyclic performance, which exhibits capacity retention of 91.7% after 50 cycles compared with only 82.1% for the pristine one. Furthermore, the CeF3-coated electrode delivers a superior high-rate capacity of 103.1 mAh g−1 at 5C, higher than 82.2 mAh g−1 for the pristine one. The remarkably improved cycling stability and high-rate capacity of the surface-modified electrode is ascribed to the presence of a stable and thin CeF3 coating layer which effectively reduces the damage of electrode structure and suppresses the increase of impedance during cycling by preventing direct contact of electrode with electrolyte.
•Cerium fluoride is used as a novel coating material for Li-rich layered cathode.•Coated cathode displays enhanced high-rate capability and cycling stability.•Coating layer suppresses the increase of electrochemical impedance of electrode.
Few layer 2D MoS2 vertical grown on biomass-based hollow carbon fibers showed excellent lithium and sodium storage performance.
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•Porous, hollow, individual carbon fibers are prepared ...by processing the palm silk.•Fewer layer 2D MoS2 are vertically grown on BHCFs via a facile hydrothermal method.•The MoS2@BHCF electrodes display excellent lithium and sodium storage performance.•DFT calculations verify an optimized structure of MoS2 vertically grown on BHCF.•A lower energy barrier of Li diffusing through MoS2 crystals than Na is testified.
2D MoS2 sheets have been extensively served as the anode materials for lithium and sodium ion batteries (LIBs, SIBs) due to its high theoretical capacity. However, its low electrical conductivity and large volume change during cycles impair the rate performance and lifespan of the electrodes. Herein, few layer MoS2 nanosheets vertically grown on biomass-based hollow carbon fibers (BHCFs) derived from palm silk are prepared via a facile hydrothermal method. The density functional theory (DFT) calculations verify an optimized structure of MoS2 vertically grown on BHCF surface and the strong interaction between the S edges of MoS2 and the carbon surface. The few layer nanosheets structure and the enhanced conductivity of MoS2 by biomass derived hollow BHCF ameliorate the diffusion of both Li and Na ions and electrons, as well as the electrode reaction kinetics. Deservedly, the MoS2@BHCF electrodes display excellent lithium and sodium storage performance, especially remarkable high-rate capabilities in LIBs. The higher reversible capacity in LIBs than in SIBs reflects the better kinetics of MoS2@BHCF in LIBs, owing to a much lower energy barrier of Li atoms diffusing through MoS2 crystals than the Na counterparts.
The practical applications of metal oxides in lithium-ion batteries require the robust and fast lithium storage performance in the wide temperature range. Construction of the suitable structure is ...still considered as an important approach to address metal oxide anode issues (volume expansion and inferior conductivity). Herein, an electrostatic adsorption-carbothermic reduction process is developed to prepare 1D hierarchical CoO@N-doped graphene microrods (CoO@N-rGO). 1D hierarchical microrod-like structure coated by a uniform & tight N-doped graphene not only builds up a bifunctional conductive path for Li+ and electrons, but also enhances the ability to accommodate the volumetric change. Oxygen vacancies caused by incomplete reduction of Co3+ would accelerate the kinetic process of conversion reaction. Moreover, a dominant pseudocapacitive effect (80.06%) induced by above structural features ensures the fast lithium storage properties. When served as anode material in LIBs, the as-prepared CoO@N-rGO manifests the high reversible capacity of 1588 mAh g−1, excellent long-term cycling stability under high current density (948 mAh g−1 after 500 cycles at 2 A g−1). Particularly, due to the reduced side-reaction between electrolyte and modified electrode, the CoO@N-rGO retains a reversible capacity of 1164 mA g−1 after 1000 cycles under 1 A g−1 at 55 °C.
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•CoO@N-rGO microrods exhibit the excellent cyclic stability at 55 °C.•An electrostatic adsorption-carbothermic reduction process is presented.•Pseudocapacitive contribution is dominated in the lithium storage process.
SnS is considered as a promising anode candidate for next-generation Li- and Na-ion batteries due to its high theoretical capacity and large interlayer distance, which provides excessive space for ...intercalation of Li- and Na-ions. However, the low electronic conductivity and large volumetric changes during charge/discharge process lead to its poor rate capability and severe capacity degradation. Herein, a sandwich-like SnS/N, S co-doped rGO/SnS structure is delicately tailored by using selective vulcanization and in situ decomposition processes. The unique sandwich-like SnS/rGO/SnS structure provides open channels for ion storage and ameliorates the electrical conductivity. RGO substrate and chemical bonds between SnS and rGO improves the electronic conductivity and furnishes additional ions/electrons transport routes. Moreover, the co-doping of N and S renders abundant sites for ions adsorption, inducing a strong pseudocapacitance effect and favoring fast electrochemical kinetics. Therefore, at the current density of at 1 A g
−1
, the sandwich-like SnS/rGO/SnS electrode delivered a high reversible capacity of 797.9 mAh g
−1
and 359.2 mAh g
−1
as an anode material in Li- and Na-ion batteries, respectively.
Graphic abstract
The integration of heterostructures within electrode materials is pivotal for enhancing electron and Li-ion diffusion kinetics. In this study, we synthesized CoO/MnO heterostructures to enhance the ...electrochemical performance of MnO using a straightforward electrostatic spinning technique followed by a meticulously controlled carbonization process, which results in embedding heterostructured CoO/MnO nanoparticles within porous nitrogen-doped carbon nanofibers (CoO/MnO/NC). As confirmed by density functional theory calculations and experimental results, CoO/MnO heterostructures play a significant role in promoting Li
ion and charge transfer, improving electronic conductivity, and reducing the adsorption energy. The accelerated electron and Li-ion diffusion kinetics, coupled with the porous nitrogen-doped carbon nanofiber structure, contribute to the exceptional electrochemical performance of the CoO/MnO/NC electrode. Specifically, the as-prepared CoO/MnO/NC exhibits a high reversible specific capacity of 936 mA h g
at 0.1 A g
after 200 cycles and an excellent high-rate capacity of 560 mA h g
at 5 A g
, positioning it as a competitive anode material for lithium-ion batteries. This study underscores the critical role of electronic and Li-ion regulation facilitated by heterostructures, offering a promising pathway for designing transition metal oxide-based anode materials with high performances for lithium-ion batteries.
Fe-based sulfides are a promising type of anode material for sodium-ion batteries (SIBs) due to their high theoretical capacities and affordability. However, these materials often suffer from issues ...such as capacity deterioration and poor conductivity during practical application. To address these challenges, an N-doped Fe
S
anode with an N, S co-doped porous carbon framework (PPF-800) was synthesized using a template-assisted method. When serving as an anode for SIBs, it delivers a robust and ultrafast sodium storage performance, with a discharge capacity of 489 mAh g
after 500 cycles at 5 A g
and 371 mAh g
after 1000 cycles at 30 A g
in the ether-based electrolyte. This impressive performance is attributed to the combined influence of heteroatomic doping and adjustable interface engineering. The N, S co-doped carbon framework embedded with Fe
S
nanoparticles effectively addresses the issues of volumetric expansion, reduces the impact of sodium polysulfides, improves intrinsic conductivity, and stimulates the dominant pseudocapacitive contribution (90.3% at 2 mV s
). Moreover, the formation of a stable solid electrolyte interface (SEI) film by the effect of uniform pore structure in ether-based electrolyte produces a lower transfer resistance during the charge-discharge process, thereby boosting the rate performance of the electrode material. This work expands a facile strategy to optimize the electrochemical performance of other metal sulfides.
Highlights
The process of machine learning is introduced in detail.
Recent developments in machine learning for low-dimensional electrocatalysts are briefly reviewed.
Future directions and ...perspectives for machine learning in hydrogen evolution reaction are critically discussed.
Efficient electrocatalysts are crucial for hydrogen generation from electrolyzing water. Nevertheless, the conventional "trial and error" method for producing advanced electrocatalysts is not only cost-ineffective but also time-consuming and labor-intensive. Fortunately, the advancement of machine learning brings new opportunities for electrocatalysts discovery and design. By analyzing experimental and theoretical data, machine learning can effectively predict their hydrogen evolution reaction (HER) performance. This review summarizes recent developments in machine learning for low-dimensional electrocatalysts, including zero-dimension nanoparticles and nanoclusters, one-dimensional nanotubes and nanowires, two-dimensional nanosheets, as well as other electrocatalysts. In particular, the effects of descriptors and algorithms on screening low-dimensional electrocatalysts and investigating their HER performance are highlighted. Finally, the future directions and perspectives for machine learning in electrocatalysis are discussed, emphasizing the potential for machine learning to accelerate electrocatalyst discovery, optimize their performance, and provide new insights into electrocatalytic mechanisms. Overall, this work offers an in-depth understanding of the current state of machine learning in electrocatalysis and its potential for future research.
Construction of a suitable hybrid structure has been considered an important approach to address the defects of metal sulfide anode materials. V3S4 nanosheets anchored on an N, S co-coped graphene ...(VS/NSG) aerogel were successfully fabricated by an efficient self-assembled strategy. During the heat treatment process, decomposition, sulfuration and N, S co-doping occurred. This hybrid structure was not only endowed with an enhanced capability to buffer the volume expansion, but also improved electron conductivity as a result of the conductive network that had been constructed. The dominating pseudocapacitive contribution (57.78% at 1 mV s−1) enhanced the electrochemical performance effectively. When serving as anode material for lithium ion batteries, VS/NSG exhibits excellent lithium storage properties, including high rate capacity (480 and 330 mAh g−1 at 5 and 10 A g−1, respectively) and stable cyclic performance (692 mAh g−1 after 400 cycles at 2 A g−1).
Hard carbon is regarded as one of the greatest potential anode materials for sodium-ion batteries (SIBs) because of its affordable price and large layer spacing. However, its poor initial coulombic ...efficiency (ICE) and low specific capacity severely restrict its practical commercialization in SIBs. In this work, we successfully constructed abundant oxygen-containing functional groups in hard carbon by using pre-oxidation anthracite as the precursor combined with controlling the carbonization temperature. The oxygen-containing functional groups in hard carbon can increase the reversible Na
adsorption in the slope region, and the closed micropores can be conducive to Na
storage in the low-voltage platform region. As a result, the optimal sample exhibits a high initial reversible sodium storage capacity of 304 mAh g
at 0.03 A g
, with an ICE of 67.29% and high capacitance retention of 95.17% after 100 cycles. This synergistic strategy can provide ideas for the design of high-performance SIB anode materials with the intent to regulate the oxygen content in the precursor.
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