Biotemplated synthesis of three-dimensional porous MnO/C-N nanocomposites from renewable rapeseed pollen: An anode material for lithium-ion batteries

Lithium-ion batteries (LIBs) are currently recognized as one of the most popular power sources available. To construct advanced LIBs exhibiting long-term endurance, great attention has been paid to enhancing their poor cycle stabilities. As the performance of LIBs is dependent on the electrode materials employed, the most promising approach to improve their life span is the design of novel electrode materials. We herein describe the rational design of a three-dimensional (3D) porous MnO/C-N nanoarchitecture as an anode material for long cycle life LIBs based on their preparation from inexpensive, renewable, and abundant rapeseed pollen (R-pollen) via a facile immersion-annealing route. Remarkably, the as-prepared MnO/C-N with its optimized 3D nanostructure exhibited a high specific capacity (756.5 mAh·g^?1 at a rate of 100 mA·g^?1), long life span (specific discharge capacity of 513.0 mAh·g^?1, ~95.16% of the initial reversible capacity, after 400 cycles at 300 mA·g^?1), and good rate capability. This material therefore represents a promising alternative candidate for the high-performance anode of next-generation LIBs.

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Flower-like NiCo2S4 nanosheets with high electrochemical performance for sodium-ion batteries

A three-dimensional flower-like NiCo₂S₄ formed by two-dimensional nanosheets is synthesized by a facile hydrothermal method and utilized as the anode for sodium-ion batteries. Studies have shown that materials can achieve the best performance under the ether-based electrolyte system with voltage ranging from 0.3 to 3 V, which could effectively avoid the dissolution of polysulfides and over-discharge of the material. Here, sodium storage mechanism and charge compensation behaviors of this ternary metal sulfide are comprehensively investigated by ex situ X-ray diffraction. Moreover, ex situ Raman spectra, ex situ X-ray photoelectron spectroscopy and transmission electron microscopy measurements are used to related tests for the first time. Additionally, quantitative kinetic analysis unravels that sodium storage partially depends on the pseudocapacitance mechanism, resulting in good specific capacity and excellent rate performance. The initial discharge capacity is as high as 748 mAh·g⁻¹ at a current density of 0.1 A·g⁻¹ with the initial coulomb efficiency of 94%, and the capacity can still maintain at 580 mAh·g⁻¹ with the Coulomb efficiency close to 100% after following 50 cycles. Moreover, by the long cycle test at a high current density of 2 A·g⁻¹, the capacity can still reach at 376 mAh·g⁻¹ after over 500 cycles.

     

Ultra-stable K metal anode enabled by oxygen-rich carbon cloth

The K metal batteries are emerged as promising alternatives beyond commercialized Li-ion batteries. However, suppressing uncontrolled dendrite is crucial to the accomplishment of K metal batteries. Herein, an oxygen-rich treated carbon cloth (TCC) has been designed as the K plating host to guide K homogeneous nucleation and suppress the dendrite growth. Both density function theory calculations and experimental results demonstrate that abundant oxygen functional groups as K-philic sites on TCC can guide K nucleation and deposition homogeneously. As a result, the TCC electrode exhibits an ultra-long-life over 800 cycles at high current density of 3.0 mA·cm⁻² for 3.0 mA·h·cm⁻². Furthermore, the symmetrical cells can run stably for 2,000 h with low over-potential less than 20 mV at 1.0 mA·cm⁻² for 1.0 mA·h·cm⁻². Even at a higher current of 5.0 mA·cm⁻², the TCC electrode can still stably cycle for 1,400 h.

     

High N-doped hierarchical porous carbon networks with expanded interlayers for efficient sodium storage

Sodium-ion batteries (SIBs) have been attracting considerable attention as a promising candidate for large-scale energy storage because of the abundance and low-cost of sodium resources. However, lack of appropriate anode materials impedes further applications. Herein, a novel self-template strategy is designed to synthesize uniform flowerlike N-doped hierarchical porous carbon networks (NHPCN) with high content of N (15.31 at.%) assembled by ultrathin nanosheets via a self-synthesized single precursor and subsequent thermal annealing. Relying on the synergetic coordination of benzimidazole and 2-methylimidazole with metal ions to produce a flowerlike network, a self-formed single precursor can be harvested. Due to the structural and compositional advantages, including the high N doping, the expanded interlayer spacing, the ultrathin two-dimensional nano-sized subunits, and the three-dimensional porous network structure, these unique NHPCN flowers deliver ultrahigh reversible capacities of 453.7 mAh·g⁻¹ at 0.1 A·g⁻¹ and 242.5 mAh·g⁻¹ at 1 A·g⁻¹ for 2,500 cycles with exceptional rate capability of 5 A·g⁻¹ with reversible capacities of 201.2 mAh·g⁻¹. The greatly improved sodium storage performance of NHPCN confirms the importance of reasonable engineering and synthesis of hierarchical carbon with unique structures.

     

Exploiting oleic acid to prepare two-dimensional assembly of Si@graphitic carbon yolk-shell nanoparticles for lithium-ion battery anodes

Carbon coating has been a routine strategy for improving the performance of Si-based anode materials for lithium-ion batteries. The ability to tailor the thickness, homogeneity and graphitization degree of carbon-coating layers is essential for addressing issues that hamper the real applications of Si anodes. Herein, we report the construction of two-dimensional (2D) assemblies of interconnected Si@graphitic carbon yolk-shell nanoparticles (2D-Si@gC) from commercial Si powders by exploiting oleic acid (OA). The OA molecules act as both the surface-coating ligands for facilitating 2D nanoparticle assembly and the precursor for forming uniform and conformal graphitic shells as thin as 4 nm. The as-prepared 2D-Si@gC with rationally designed void space exhibits excellent rate capability and cycling stability when used as anode materials for lithium-ion batteries, delivering a capacity of 1,150 mAh·g⁻¹ at an ultrahigh current density of 10 A·g⁻¹ and maintaining a stabilized capacity of 1,275 mAh·g⁻¹ after 200 cycles at 4 A·g⁻¹. The formation of yolk-shell nanoparticles confines the deposition of solid electrolyte interphase (SEI) onto the outer carbon shell, while simultaneously providing sufficient space for volumetric expansion of Si nanoparticles. These attributes effectively mitigate the thickness variations of the entire electrode during repeated lithiation and delithiation, which combined with the unique 2D architecture and interconnected graphitic carbon shells of 2D-Si@gC contributes to its superior rate capability and cycling performance.

     

Multi-redox phenazine/non-oxidized graphene/cellulose nanohybrids as ultrathick cathodes for high-energy organic batteries

Various redox-active organic molecules can serve as ideal electrode materials to realize sustainable energy storage systems. Yet, to be more appropriate for practical use, considerable architectural engineering of an ultrathick, high-loaded organic electrode with reliable electrochemical performance is of crucial importance. Here, by utilizing the synergetic effect of the non-covalent functionalization of highly conductive non-oxidized graphene flakes (NOGFs) and introduction of mechanically robust cellulose nanofiber (CNF)-intermingled structure, a very thick (≈ 1 mm), freestanding organic nanohybrid electrode which ensures the superiority in cycle stability and areal capacity is reported. The well-developed ion/electron pathways throughout the entire thickness and the enhanced kinetics of electrochemical reactions in the ultrathick 5,10-dihydro-5,10-dimethylphenazine/NOGF/CNF (DMPZ-NC) cathodes lead to the high areal energy of 9.4 mWh·cm?2 (= 864 Wh·kg?1 at 158 W·kg?1). This novel ultrathick electrode architecture provides a general platform for the development of the high-performance organic battery electrodes.     

VO2·0.2H2O nanocuboids anchored onto graphene sheets as the cathode material for ultrahigh capacity aqueous zinc ion batteries

Aqueous Zinc-ion batteries (ZIBs), using zinc negative electrode and aqueous electrolyte, have attracted great attention in energy storage field due to the reliable safety and low-cost. A composite material comprised of VO₂·0.2H₂O nanocuboids anchored on graphene sheets (VOG) is synthesized through a facile and efficient microwave-assisted solvothermal strategy and is used as aqueous ZIBs cathode material. Owing to the synergistic effects between the high conductivity of graphene sheets and the desirable structural features of VO₂·0.2H₂O nanocuboids, the VOG electrode has excellent electronic and ionic transport ability, resulting in superior Zn ions storage performance. The Zn/VOG system delivers ultrahigh specific capacity of 423 mAh·g⁻¹ at 0.25 A·g⁻¹ and exhibits good cycling stability of up to 1,000 cycles at 8 A·g⁻¹ with 87% capacity retention. Systematical structural and elemental characterizations confirm that the interlayer space of VO₂·0.2H₂O nanocuboids can adapt to the reversible Zn ions insertion/extraction. The as-prepared VOG composite is a promising cathode material with remarkable electrochemical performance for low-cost and safe aqueous rechargeable ZIBs.

     

Graphene oxide-decorated Fe<Subscript>2</Subscript>(MoO<Subscript>4</Subscript>)<Subscript>3</Subscript> microflowers as a promising anode for lithium and sodium storage

Mixed transition metal oxides (MTMOs) have received intensive attention as promising anode materials for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). In this work, we demonstrate a facile one-step water-bath method for the preparation of graphene oxide (GO) decorated Fe₂(MoO₄)₃ (FMO) microflower composite (FMO/GO), in which the FMO is constructed by numerous nanosheets. The resulting FMO/GO exhibits excellent electrochemical performances in both LIBs and SIBs. As the anode material for LIBs, the FMO/GO delivers a high capacity of 1,220 mAh·g^–1 at 200 mA·g^–1 after 50 cycles and a capacity of 685 mAh·g^–1 at a high current density of 10 A·g^–1. As the anode material for SIBs, the FMO/GO shows an initial discharge capacity of 571 mAh·g^–1 at 100 mA·g^–1, maintaining a discharge capacity of 307 mAh·g^–1 after 100 cycles. The promising performance is attributed to the good electrical transport from the intimate contact between FMO and graphene oxide. This work indicates that the FMO/GO composite is a promising anode for high-performance lithium and sodium storage.

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Infiltrating lithium into carbon cloth decorated with zinc oxide arrays for dendrite-free lithium metal anode

Lithium metal anode for batteries has attracted extensive attentions, but its application is restricted by the hazardous dendritic Li growth and dead Li formation. To address these issues, a novel Li anode is developed by infiltrating molten Li metal into conductive carbon cloth decorated with zinc oxide arrays. In carbonate-based electrolyte, the symmetric cell shows no short circuit over 1,500 h at 1 mA·cm⁻², and stable voltage profiles at 3 mA·cm⁻² for ∼ 300 h cycling. A low overpotential of ∼ 243 mV over 350 cycles at a high current density of 10 mA·cm⁻² is achieved, compared to the seriously fluctuated voltage and fast short circuit in the cell using bare Li metal. Meanwhile, the asymmetric cell withstands 1,000 cycles at 10 C (1 C = 167 mAh·g⁻¹) compared to the 210 cycles for the cell using bare Li anode. The excellent performance is attributed to the well-regulated Li plating/stripping driven from the formation of LiZn alloy on the wavy carbon fibers, resulting in the suppression of dendrite growth and pulverization of the Li electrode during cycling.

     

Dandelion-Like Bi2S3/rGO hierarchical microspheres as high-performance anodes for potassium-ion and half/full sodium-ion batteries

Sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) have been considered as attractive alternatives for next-generation battery systems, which have promising application potential due to their earth abundance of potassium and sodium, high capacity and suitable working potential, however, the design and application of bi-functional high-performance anode still remain a great challenge up to date. Bismuth sulfide is suitable as anode owing to its unique laminar structure with relatively large interlayer distance to accommodate larger radius ions, high theoretical capacity and high volumetric capacity etc. In this study, dandelion-like Bi₂S₃/rGO hierarchical microspheres as anode material for PIBs displayed reversible capacity, and 206.91 mAh·g⁻¹ could be remained after 1,200 cycles at a current density of 100 mA·g⁻¹. When applied as anode materials for SIBs, 300 mAh·g⁻¹ could be retained after 300 cycles at 2 A·g⁻¹ and its initial Coulombic efficiency is as high as 97.43%. Even at high current density of 10 A·g⁻¹, 120.3 mAh·g⁻¹ could be preserved after 3,400 cycles. The Na₃V₂(PO₄)₃@rGO//Bi₂S₃/rGO sodium ion full cells were successfully assembled which displays stable performance after 60 cycles at 100 mA·g⁻¹. The above results demonstrate that Bi₂S₃/rGO has application potential as high performance bi-functional anode for PIBs and SIBs.

     

A phenazine anode for high-performance aqueous rechargeable batteries in a wide temperature range

Aqueous rechargeable batteries are a possible strategy for large-scale energy storage systems. However, limited choices of anode materials restrict their further application. Here we report phenazine (PNZ) as stable anode materials in different alkali-ion (Li⁺, Na⁺, K⁺) electrolyte. A novel full cell is assembled by phenazine anode, Na_0.44MnO₂ cathode and 10 M NaOH electrolyte to further explore the electrochemical performance of phenazine anode. This battery is able to achieve high capacity (176.7 mAh·g^?1 at 4 C (1.2·Ag^?1)), ultralong cycling life (capacity retention of 80% after 13,000 cycles at 4 C), and excellent rate capacity (92 mAh·g^?1 at 100 C (30 A·g^?1)). The reaction mechanism of PNZ during charge—discharge process is demonstrated by in situ Raman spectroscopy, in situ Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. Furthermore, the system is able to successfully operate at wide temperature range from ?20 to 70 °C and achieves remarkable electrochemical performance.

     

Unveiling nanoplates-assembled Bi2MoO6 microsphere as a novel anode material for high performance potassium-ion batteries

Bismuth (Bi)-based electrode has aroused tremendous interest in potassium-ion batteries (PIBs) on account of its low cost, high electronic conductivity, low charge voltage and high theoretical capacity. However, the rapid capacity fading and poor lifespan induced by the normalized volume expansion (up to ~ 406%) and serious aggregation of Bi during cycling process hinder its application. Herein, bismuth molybdate (Bi₂MoO₆) microsphere assembled by 2D nanoplate units is successfully prepared by a facile solvothermal method and demonstrated as a promising anode for PIBs. The unique microsphere structure and the self-generated potassium molybdate (K-Mo-O species) during the electrochemical reactions can effectively suppress mechanical fracture of Bi-based anode originated from the volume variation during charge/discharge of the battery. As a result, the Bi₂MoO₆ microsphere without hybridizing with any other conductive carbon matrix shows superior electrochemical performance, which delivers a high reversible capacity of 121.7 mAh·g⁻¹ at 100 mA·g⁻¹ over 600 cycles. In addition, the assembled perylenetetracarboxylic dianhydride (PTCDA)//Bi₂MoO₆ full-cell coupled with PTCDA cathode demonstrates the potential application of Bi₂MoO₆ microsphere. Most importantly, the phase evolution of Bi₂MoO₆ microsphere during potassiation/depotassiation process is successfully deciphered by ex situ X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS), and transmission electron microscopy (TEM) technologies, which reveals a combination mechanism of conversion reaction and alloying/dealloying reaction for Bi₂MoO₆ anode. Our findings not only open a new way to enhance the performance of Bi-based anode in PIBs, but also provide useful implications to other alloy-type anodes for secondary alkali-metal ion batteries.

     

Hydrogenated vanadium oxides as an advanced anode material in lithium ion batteries

Current research on vanadium oxides in lithium ion batteries (LIBs) considers them as cathode materials, whereas they are rarely studied for use as anodes in LIBs because of their low electrical conductivity and rapid capacity fading. In this work, hydrogenated vanadium oxide nanoneedles were prepared and incorporated into freeze-dried graphene foam. The hydrogenated vanadium oxides show greatly improved charge-transfer kinetics, which lead to excellent electrochemical properties. When tested as anode materials (0.005–3.0 V vs. Li/Li⁺) in LIBs, the sample activated at 600 °C exhibits high specific capacity (～941 mA·h·g^?1 at 100 mA·g^?1) and high-rate capability (～504 mA·h·g^?1 at 5 A·g^?1), as well as excellent cycling performance (～285 mA·h·g^?1 in the 1,000^th cycle at 5 A·g^?1). These results demonstrate the promising application of vanadium oxides as anodes in LIBs.

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Supersaturated bridge-sulfur and vanadium co-doped M0S2 nanosheet arrays with enhanced sodium storage capability

The low specific capacity and sluggish electrochemical reaction kinetics greatly block the development of sodium-ion batteries (SIBs). New high-performance electrode materials will enhance development and are urgently required for SIBs. Herein, we report the preparation of supersaturated bridge-sulfur and vanadium co-doped MoS₂ nanosheet arrays on carbon cloth (denoted as V-MoS_2+x/CC). The bridge-sulfur in MoS₂ has been created as a new active site for greater Na⁺ storage. The vanadium doping increases the density of carriers and facilitates accelerated electron transfer. The synergistic dual-doping effects endow the V-MoS_2+x/CC anodes with high sodium storage performance. The optimized V-MoS_2.49/CC gives superhigh capacities of 370 and 214 mAh·g⁻¹ at 0.1 and 10 A·g⁻¹ within 0.4−3.0 V, respectively. After cycling 3,000 times at 2 A·g⁻¹, almost 83% of the reversible capacity is maintained. The findings indicate that the electrochemical performances of metal sulfides can be further improved by edge-engineering and lattice-doping co-modification concept.

     

Walnut-inspired microsized porous silicon/graphene core–shell composites for high-performance lithium-ion battery anodes

Silicon is considered an exceptionally promising alternative to the most commonly used material, graphite, as an anode for next-generation lithium-ion batteries, as it has high energy density owing to its high theoretical capacity and abundant storage. Here, microsized walnut-like porous silicon/reduced graphene oxide (P-Si/rGO) core–shell composites are successfully prepared via in situ reduction followed by a dealloying process. The composites show specific capacities of more than 2,100 mAh·g^?1 at a current density of 1,000 mA·g^?1, 1,600 mAh·g^?1 at 2,000 mA·g^?1, 1,500 mAh·g^?1 at 3,000 mA·g^?1, 1,200 mAh·g^?1 at 4,000 mA·g^?1, and 950 mAh·g^?1 at 5,000 mA·g^?1, and maintain a value of 1,258 mAh·g^?1 after 300 cycles at a current density of 1,000 mA·g^?1. Their excellent rate performance and cycling stability can be attributed to the unique structural design: 1) The graphene shell dramatically improves the conductivity and stabilizes the solid–electrolyte interface layers; 2) the inner porous structure supplies sufficient space for silicon expansion; 3) the nanostructure of silicon can prevent the pulverization resulting from volume expansion stress. Notably, this in situ reduction method can be applied as a universal formula to coat graphene on almost all types of metals and alloys of various sizes, shapes, and compositions without adding any reagents to afford energy storage materials, graphene-based catalytic materials, graphene-enhanced composites, etc.

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Ultrasonication-assisted and gram-scale synthesis of Co-LDH nanosheet aggregates for oxygen evolution reaction

Electrochemical water splitting (EWS) is a highly clean and efficient method for high-purity hydrogen production. Unfortunately, EWS suffers from the sluggish and complex oxygen evolution reaction (OER) kinetics at anode. At present, the efficient, stable, and low-cost non-precious metal based OER electrocatalyst is still a great and long-term challenge for the future industrial application of EWS technology. Herein, we develop a simple and fast approach for gram-scale synthesis of flower-like cobalt-based layered double hydroxides nanosheet aggregates by ultrasonic synthesis, which show outstanding electrocatalytic performance for the oxygen evolution reaction in alkaline media, such as preeminent stability, small overpotential of 300 mV at 10 mA·cm⁻² and small Tafel slope of 110 mV·dec⁻¹.

     

Facile synthesis of porous germanium-iron bimetal oxide nanowires as anode materials for lithium-ion batteries

Germanium-based oxide has been found to be a promising high-capacity anode material for lithium-ion batteries (LIBs). However, it exhibits poor electrochemical performance because of the drastic volume change during cycling. Herein, we designed porous Ge-Fe bimetal oxide nanowires (Ge-Fe-O_x-700 NWs) by a large-scale and facile solvothermal reaction. When used as the anode material for LIBs, these Ge-Fe-O_x-700 NWs exhibited superior electrochemical performance (～ 1,120 mAh·g^?1 at a current density of 100 mA·g^?1) and good cycling performance (～ 750 mAh·g^?1 after 50 cycles at a current density of 100 mA·g^?1). The improved performance is due to the small NW diameter, which allows for better accommodation of the drastic volume changes and zero-dimensional nanoparticles, which shorten the diffusion length of ions and electrons.

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A combination of hierarchical pore and buffering layer construction for ultrastable nanocluster Si/SiOx anode

Porous Si can be synthesized from diverse silica (SiO₂) via magnesiothermic reduction technology and widely employed as potential anode material in lithium ion batteries. However, concerns regarding the influence of residual silicon oxide (SiO_x) component on resulted Si anode after reduction are still lacked. In this work, we intentionally fabricate a cauliflower-like silicon/silicon oxide (CF-Si/SiO_x) particles from highly porous SiO₂ spheres through insufficient magnesiothermic reduction, where residual SiO_x component and internal space play an important role in preventing the structural deformation of secondary bulk and restraining the expansion of Si phase. Moreover, the hierarchically structured CF-Si/SiO_x exhibits uniformly-dispersed channels, which can improve ion transport and accommodate large volume expansion, simultaneously. As a result, the CF-Si/SiO_x-700 anode shows excellent electrochemical performance with a specific capacity of ~1,400 mA·h·g⁻¹ and a capacity retention of 98% after 100 cycles at the current of 0.2 A·g⁻¹.

     

Graphitic nanorings for super-long lifespan lithium-ion capacitors

Porous graphitic carbon nanorings (PGCNs) are proposed by smart catalytic graphitization of nano-sized graphene quantum dots (GQDs). The as-prepared PGCNs show unique ring-like morphology with diameter around 10 nm, and demonstrate extraordinary mesoporous structure, controllable graphitization degree and highly defective nature. The mechanism from GQDs to PGCNs is proven to be a dissolution-precipitation process, undergoing the procedure of amorphous carbon, intermediate phase, graphitic carbon nanorings and graphitic carbon nanosheets. Further, the relationship between particles size of GQDs precursor and graphitization degree of PGCNs products is revealed. The unique microstructure implies PGCNs a broad prospect for energy storage application. When applied as negative electrode materials in dual-carbon lithium-ion capacitors, high energy density (77.6 Wh·kg⁻¹) and super long lifespan (89.5% retention after 40,000 cycles at 5.0 A·g⁻¹) are obtained. The energy density still maintains at 24.5 Wh·kg⁻¹ even at the power density of 14.1 kW·kg⁻¹, demonstrating excellent rate capability. The distinct microstructure of PGCNs together with the strategy for catalytic conversion from nanocarbon precursors to carbon nanorings opens a new window for carbon materials in electrochemical energy storage.

     

Phosphorus-doping activates carbon nanotubes for efficient electroreduction of nitrogen to ammonia

The electrochemical nitrogen reduction reaction (NRR) as an energy-efficient approach for ammonia synthesis is hampered by the low ammonia yield and ambiguous reaction mechanism. Herein, phosphorus-doped carbon nanotube (P-CNTs) is developed as an efficient metal-free electrocatalyst for NRR with a remarkable NH₃ yield of 24.4 μg·h⁻¹·mg⁻¹_cat. and partial current density of 0.61 mA·cm⁻². Such superior activity is found to be from P doping and highly conjugated CNTs substrate. Experimental and theoretical investigations discover that the electron-deficient phosphorus sites with Lewis acidity should be genuine active sites and NRR on P-CNTs follows the distal pathway. These findings provide insightful understanding on NRR processes on P-CNTs, opening up opportunities for the rational design of highly-active cost-effective metal-free catalysts for electrochemical ammonia synthesis.