Stabilizing Co3O4 nanorods/N-doped graphene as advanced anode for lithium-ion batteries

Tricobalt tetroxide (Co₃O₄) is one of the promising anodes for lithium-ion batteries (LIBs) due to its high theoretical capacity. However, the poor electrical conductivity and the rapid capacity decay hamper its practical application. In this work, we design and fabricate a hierarchical Co₃O₄ nanorods/N-doped graphene (Co₃O₄/NG) material by a facile hydrothermal method. The nitrogen-doped graphene layers could buffer the volume change of Co₃O₄ nanorods during the delithium/lithium process, increase the electrical conductivity, and profit the diffusion of ions. As an anode, the Co₃O₄/NG material reveals high specific capacities of 1873.8 mA·h·g⁻¹ after 120 cycles at 0.1 A·g⁻¹ as well as 1299.5 mA·h·g⁻¹ after 400 cycles at 0.5 A·g⁻¹. Such superior electrochemical performances indicate that this work may provide an effective method for the design and synthesis of other metal oxide/N-doped graphene electrode materials.     

FeS2@C nanorods embedded in three-dimensional graphene as high-performance anode for sodium-ion batteries

FeS₂ has drawn tremendous attention as electrode material for sodium-ion batteries (SIBs) due to its high theoretical capacity and abundant resources. However, it suffers from severe volume expansion and dull reaction kinetics during the cycling process, leading to poor rate capacity and short cyclability. Herein, a well-designed FeS₂@C/G composite constructed by FeS₂ nanoparticles embedded in porous carbon nanorods (FeS₂@C) and covered by three-dimensional (3D) graphene is reported. FeS₂ nanoparticles can shorten the Na⁺ diffusion distance during the sodiation–desodiation process. Porous carbon nanorods and 3D graphene not only improve conductivity but also provide double protection to alleviate the volume variation of FeS₂ during cycling. Consequently, FeS₂@C/G exhibits excellent cyclability (83.3% capacity retention after 300 cycles at 0.5 A·g⁻¹ with a capacity of 615.1 mA·h·g⁻¹) and high rate capacity (475.1 mA·h·g⁻¹ at 5 A·g⁻¹ after 2000 cycles). The pseudocapacitive process is evaluated and confirmed to significantly contribute to the high rate capacity of FeS₂@C/G.     

Double core---shell nanostructured Sn---Cu alloy as enhanced anode materials for lithium and sodium storage

Sn-based alloy materials are considered as a promising anode candidate for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs), whereas they suffer from severe volume change during the discharge/charge process. To address the issue, double core–shell structured Sn–Cu@SnO₂@C nanocomposites have been prepared by a simple co-precipitation method combined with carbon coating approach. The double core–shell structure consists of Sn–Cu multiphase alloy nanoparticles as the inner core, intermediate SnO₂ layer anchored on the surface of Sn–Cu nanoparticle and outer carbon layer. The Sn–Cu@SnO₂@C electrode exhibits outstanding electrochemical performances, delivering a reversible capacity of 396 mA·h·g⁻¹ at 100 mA·g⁻¹ after 100 cycles for LIBs and a high initial reversible capacity of 463 mA·h·g⁻¹ at 50 mA·g⁻¹ and a capacity retention of 86% after 100 cycles, along with a remarkable rate capability (193 mA·h·g⁻¹ at 5000 mA·g⁻¹) for SIBs. This work provides a viable strategy to fabricate double core–shell structured Sn-based alloy anodes for high energy density LIBs and SIBs.     

A novel and simple nitrogen-doped carbon/polyaniline electrode material for supercapacitors

We demonstrated a simple and environment-friendly method in thepreparation of N-doped carbon/PANI(NCP)composite without binder.The structureand the property of NCP have been characterized by XPS,IR,XRD,SEM,CV,GCD and EIS.The results reveal that NCP has high capacitance performance of up to 615 F·g^-1at 0.6A·g^-1.Additionally,the asymmetric NCP₃₀₀/lcarbon supercapacitor delivers a highcapacitance(111 F·g^-1at 1A·g^-1)and a capacity retention rate of 82%after 1200 cyclesat 2A·g^-1.The ASC cell could deliver a high energy density of 39.1 W·h·kg^-1at a powerdensity of 792.6 W·kg^-1.     

Chestnut shell-like N-doped carbon coated NiCoP hollow microspheres for hybrid supercapacitors with excellent electrochemical performance

In this work, transition metal phosphides (TMPs) were reinforced by a solvothermal synthesis method and in situ polymerization in dopamine with one-step phosphating and carbonizing process to form chestnut shell-like N-doped carbon coated NiCoP (NiCoP@N-C) hollow microspheres. Excellent morphologic structure is still reflected in NiCoP@N-C, which is suitable for rapid electron and electrolyte transfer. Benefiting from the excellent structure, the coating of N-doped carbon, and the synergistic effect of Ni and Co, NiCoP@N-C reveals excellent electrochemical properties (high specific capacitance of 1660 F·g⁻¹ (830 C·g⁻¹) at 1 A·g⁻¹). In addition, a NiCoP@N-C//carbonization HKUST-1 (HC) achieves high specific energy of 51.8 Wh·kg⁻¹, ultrahigh specific power of 21.63 kW·kg⁻¹, and excellent cycling stability up to 10000 cycles (a capacitance retention of 96.7%). The results show that the NiCoP@N-C electrode material has a wide application in supercapacitors and other energy storage devices.     

Superior performance for lithium storage from an integrated composite anode consisting of SiO-based active material and current collector

Silicon-based material is considered to be one of the most promising anodes for the next-generation lithium-ion batteries (LIBs) due to its rich sources, non-toxicity, low cost and high theoretical specific capacity. However, it cannot maintain a stable electrode structure during repeated charge/discharge cycles, and therefore long cycling life is difficult to be achieved. To address this problem, herein a simple and efficient method is developed for the fabrication of an integrated composite anode consisting of SiO-based active material and current collector, which exhibits a core–shell structure with nitrogen-doped carbon coating on SiO/P micro-particles. Without binder and conductive agent, the volume expansion of SiO active material in the integrated composite anode is suppressed to prevent its pulverization. At a current density of 500 mA·g⁻¹, this integrated composite anode exhibits a reversible specific capacity of 458 mA·h·g⁻¹ after 200 cycles. Furthermore, superior rate performance and cycling stability are also achieved. This work illustrates a potential method for the fabrication of integrated composite anodes with superior electrochemical properties for high-performance LIBs.     

Electrochemical performances of NiO/Ni2N nanocomposite thin film as anode material for lithium ion batteries

Despite the high specific capacities, the practical application of transition metal oxides as the lithium ion battery (LIB) anode is hindered by their low cycling stability, severe polarization, low initial coulombic efficiency, etc. Here, we report the synthesis of the NiO/Ni₂N nanocomposite thin film by reactive magnetron sputtering with a Ni metal target in an atmosphere of 1 vol.% O₂ and 99 vol.% N₂. The existence of homogeneously dispersed nano Ni₂N phase not only improves charge transfer kinetics, but also contributes to the one-off formation of a stable solid electrolyte interphase (SEI). In comparison with the NiO electrode, the NiO/Ni₂N electrode exhibits significantly enhanced cycling stability with retention rate of 98.8% (85.6% for the NiO electrode) after 50 cycles, initial coulombic efficiency of 76.6% (65.0% for the NiO electrode) and rate capability with 515.3 mA·h·g⁻¹ (340.1 mA·h·g⁻¹ for the NiO electrode) at 1.6 A·g⁻¹.     

Facile solvothermal synthesis of NiFe2O4 nanoparticles for high-performance supercapacitor applications

We report a green and facile approach for the synthesis of NiFe₂O₄ (NF) nanoparticles with good crystallinity. The prepared materials are studied by various techniques in order to know their phase structure, crystallinity, morphology and elemental state. The BET analysis revealed a high surface area of 80.0 m²·g⁻¹ for NF possessing a high pore volume of 0.54 cm³·g⁻¹, also contributing to the amelioration of the electrochemical performance. The NF sample is studied for its application in supercapacitors in an aqueous 2 mol·L⁻¹ KOH electrolyte. Electrochemical properties are studied both in the three-electrode method and in a symmetrical supercapacitor cell. Results show a high specific capacitance of 478.0 F·g⁻¹ from the CV curve at an applied scan rate of 5 mV·s⁻¹ and 368.0 F·g⁻¹ from the GCD analysis at a current density of 1 A·g⁻¹ for the NF electrode. Further, the material exhibited an 88% retention of its specific capacitance after continuous 10000 cycles at a higher applied current density of 8 A·g⁻¹. These encouraging properties of NF nanoparticles suggest the practical applicability in high-performance supercapacitors.     

Feather-like NiCo2O4 self-assemble from porous nanowires as binder-free electrodes for low charge transfer resistance

The unique feather-like arrays composing of ultrathin secondary nanowires are fabricated on nickel foam (NF) through a facile hydrothermal strategy. Thus, the enhancement of electrochemical properties especially the low charge transfer resistance strongly depends on more active sites and porosity of the morphology. Benefiting from the unique structure, the optimized NiCo₂O₄ electrode delivers a significantly lower charge transfer resistance of 0.32 Ω and a high specific capacitance of 450 F·g⁻¹ at 0.5 A·g⁻¹, as well as a superior cycling stability of 139.6% capacitance retention. The improvement of the electrochemical energy storage property proves the potential of the fabrication of various binary metal oxide electrodes for applications in the electrochemical energy field.     

Crystalline and amorphous MnO2 cathodes with open framework enable high-performance aqueous zinc-ion batteries

Currently, δ-MnO₂ is one of the popularly studied cathode materials for aqueous zinc-ion batteries (ZIBs) but impeded by the sluggish kinetics of Zn²⁺ and the Mn cathode dissolution. Here, we report our discovery in the study of crystalline/amorphous MnO₂ (disordered MnO₂), prepared by a simple redox reaction in the order/disorder engineering. This disordered MnO₂ cathode material, having open framework with more active sites and more stable structure, shows improved electrochemical performance in 2 mol·L⁻¹ ZnSO₄/0.1 mol·L⁻¹ MnSO₄ aqueous electrolyte. It delivers an ultrahigh discharge specific capacity of 636 mA·h·g⁻¹ at 0.1 A·g⁻¹ and remains a large discharge capacity of 216 mA·h·g⁻¹ even at a high current density of 1 A·g⁻¹ after 400 cycles. Hence disordered MnO₂ could be a promising cathode material for aqueous ZIBs. The storage mechanism of the disordered MnO₂ electrode is also systematically investigated by structural and morphological examinations of ex situ, ultimately proving that the mechanism is the same as that of the δ-MnO₂ electrode. This work may pave the way for the possibility of using the order/disorder engineering to introduce novel properties in electrode materials for high-performance aqueous ZIBs.     

Amine-assisted synthesis of FeS@N-C porous nanowires for highly reversible lithium storage

Iron sulfide is an attractive anode material for lithium-ion batteries (LIBs) due to its high specific capacity, environmental benignity, and abundant resources. However, its application is hindered by poor cyclability and rate performance, caused by a large volume variation and low conductivity. Herein, iron sulfide porous nanowires confined in an N-doped carbon matrix (FeS@N-C nanowires) are fabricated through a simple amine-assisted solvothermal reaction and subsequent calcination strategy. The as-obtained FeS@N-C nanowires, as an LIB anode, exhibit ultrahigh reversible capacity, superior rate capability, and long-term cycling performance. In particular, a high specific capacity of 1,061 mAh·g^?1 can be achieved at 1 A·g^?1 after 500 cycles. Most impressively, it exhibits a high specific capacity of 433 mAh·g^?1 even at 5 A·g^?1. The superior electrochemical performance is ascribed to the synergistic effect of the porous nanowire structure and the conductive N-doped carbon matrix. These results demonstrate that the synergistic strategy of combining porous nanowires with an N-doped carbon matrix holds great potential for energy storage.

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Two-step preparation of carbon nanotubes/RuO2/polyindole ternary nanocomposites and their application as high-performance supercapacitors

A ternary single-walled carbon nanotubes/RuO₂/polyindole (SWCNT/RuO₂/PIn) nanocomposite was fabricated by the oxidation polymerization of indole on the prefabricated SWCNT/RuO₂ binary nanocomposites. The nanocomposite was measured by FTIR, XRD, SEM, TEM, EDS and XPS, together with the electrochemical technique. The electrochemical results demonstrated that the symmetric supercapacitor used SWCNT/RuO₂/PIn as electrodes presented 95% retention rate after 10000 cycles, superior capacitive performance of 1203 F·g⁻¹ at 1 A·g⁻¹, and high energy density of 33 W·h·kg⁻¹ at 5000 W·kg⁻¹. The high capacitance performance of SWCNT/RuO₂/PIn nanocomposite was mainly ascribed to the beneficial cooperation effect among components. This indicated that the SWCNT/RuO₂/PIn nanocomposite would be a good candidate for high-performance supercapacitors.     

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.

     

Amorphous Sn modified nitrogen-doped porous carbon nanosheets with rapid capacitive mechanism for high-capacity and fast-charging lithium-ion batteries

Sn-based materials are considered as a kind of potential anode materials for lithium-ion batteries (LIBs) owing to their high theoretical capacity. However, their use is limited by large volume expansion deriving from the lithiation/delithiation process. In this work, amorphous Sn modified nitrogen-doped porous carbon nanosheets (ASn-NPCNs) are obtained. The synergistic effect of amorphous Sn and high edge-nitrogen-doped level porous carbon nanosheets provides ASn-NPCNs with multiple advantages containing abundant defect sites, high specific surface area (214.9 m²·g⁻¹), and rich hierarchical pores, which can promote the lithium-ion storage. Serving as the LIB anode, the as-prepared ASn-NPCNs-750 electrode exhibits an ultrahigh capacity of 1643 mAh·g⁻¹ at 0.1 A·g⁻¹, ultrafast rate performance of 490 mAh·g⁻¹ at 10 A·g⁻¹, and superior long-term cycling performance of 988 mAh·g⁻¹ at 1 A·g⁻¹ after 2000 cycles with a capacity retention of 98.9%. Furthermore, the in-depth electrochemical kinetic test confirms that the ultrahigh-capacity and fast-charging performance of the ASn-NPCNs-750 electrode is ascribed to the rapid capacitive mechanism. These impressive results indicate that ASn-NPCNs-750 can be a potential anode material for high-capacity and fast-charging LIBs.     

Honeycomb-like polyaniline for flexible and folding all-solid-state supercapacitors

Porous polyaniline (PANI) was prepared through an efficient and costeffective method by polymerization of aniline in the NaCl solution at room temperature. The resulting PANI provided large surface area due to its highly porous structure and the intercrossed nanorod, resulting in good electrochemical performance. The porous PANI electrodes showed a high specific capacitance of 480 F·g^-1, 3 times greater than that of PANI without using the NaCl solution. We also make chemically crosslinked hydrogel film for hydrogel polymer electrolyte as well as the flexible supercapacitors (SCs) with PANI. The specific capacitance of the device was 234 F·g^-1 at the current density of 1 A·g^-1. The energy density of the device could reach as high as 75 W·h·kg^-1 while the power density was 0.5 kW·kg^-1, indicating that PANI be a promising material in flexible SCs.     

CoP nanoparticles enwrapped in N-doped carbon nanotubes for high performance lithium-ion battery anodes

CoP is a candidate lithium storage material for its high theoretical capacity. However, large volume variations during the cycling processes haunted its application. In this work, a four-step strategy was developed to synthesize N-doped carbon nanotubes wrapping CoP nanoparticles (CoP@N-CNTs). Integration of nanosized particles and hollow-doped CNTs render the as-prepared CoP@N-CNTs excellent cycling stability with a reversible charge capacity of 648 mA·h·g⁻¹ at 0.2 C after 100 cycles. The present strategy has potential application in the synthesis of phosphide enwrapped in carbon nanotube composites which have potential application in lithium-ion storage and energy conversion.     

Nickel-decorated TiO2 nanotube arrays as a self-supporting cathode for lithium--sulfur batteries

Lithium–sulfur batteries are considered to be one of the strong competitors to replace lithium-ion batteries due to their large energy density. However, the dissolution of discharge intermediate products to the electrolyte, the volume change and poor electric conductivity of sulfur greatly limit their further commercialization. Herein, we proposed a self-supporting cathode of nickel-decorated TiO₂ nanotube arrays (TiO₂ NTs@Ni) prepared by an anodization and electrodeposition method. The TiO₂ NTs with large specific surface area provide abundant reaction space and fast transmission channels for ions and electrons. Moreover, the introduction of nickel can enhance the electric conductivity and the polysulfide adsorption ability of the cathode. As a result, the TiO₂ NTs@Ni–S electrode exhibits significant improvement in cycling and rate performance over TiO₂ NTs, and the discharge capacity of the cathode maintains 719 mA·h·g⁻¹ after 100 cycles at 0.1 C.     

Preparation of porous sea-urchin-like CuO/ZnO composite nanostructure consisting of numerous nanowires with improved gas-sensing performance

A sea-urchin-like CuO/ZnO porous nanostructure is obtained via a simple solution method followed by a calcination process. There are abundant pores among the resulting nanowires due to the thermal decomposition of copper–zinc hydroxide carbonate. The specific surface area of the as-prepared CuO/ZnO sample is determined as 31.3 m²·g⁻¹. The gas-sensing performance of the sea-urchin-like CuO/ZnO sensor is studied by exposure to volatile organic compound (VOC) vapors. With contrast to a pure porous sea-urchin-like ZnO sensor, the sea-urchin-like CuO/ZnO sensor shows superior gas-sensing behavior for acetone, formaldehyde, methanol, toluene, isopropanol and ethanol. It exhibits a high response of 52.6–100 ppm acetone vapor, with short response/recovery time. This superior sensing behavior is mainly ascribed to the porous nanowire-assembled structure with abundant p–n heterojunctions.     

Composites of graphene and encapsulated silicon for practically viable high-performance lithium-ion batteries

A facile and scalable approach to synthesize silicon composite anodes has been developed by encapsulating Si particles via in situ polymerization and carbonization of phloroglucinol-formaldehyde gel, followed by incorporation of graphene nanoplatelets. As a result of its structural integrity, high packing density and an intimate electrical contact consolidated by the conductive networks, the composite anode yielded excellent electrochemical performance in terms of charge storage capability, cycling life and coulombic efficiency. A half cell achieved reversible capacities of 1,600 mAh·g^?1 and 1,000 mAh·g^?1 at 0.5 A·g^?1 and 2.1 A·g^?1, respectively, while retaining more than 70% of the initial capacities over 1,000 cycles. Complete lithium-ion pouch cells coupling the anode with a lithium metal oxide cathode demonstrated excellent cycling performance and energy output, representing significant advance in developing Si-based electrode for practical application in high-performance lithium-ion batteries.      

One-step gas-phase construction of carbon-coated Fe3O4 nanoparticle/carbon nanotube composite with enhanced electrochemical energy storage

Carbon nanotubes (CNTs) as superior support materials for functional nanoparticles (NPs) have been widely demonstrated. Nevertheless, the homogeneous loading of these NPs is still frustrated due to the inert surface of CNTs. In this work, a facile gas-phase pyrolysis strategy that the mixture of ferrocene and CNTs are confined in an isolated reactor with rising temperature is developed to fabricate a carbon-coated Fe₃O₄ nanoparticle/carbon nanotube (Fe₃O₄@C/CNT) composite. It is found the ultra-small Fe₃O₄ NPs (<10 nm) enclosed in a thin carbon layer are uniformly anchored on the surface of CNTs. These structural benefits result in the excellent lithium-ion storage performances of the Fe₃O₄@C/CNT composite. It delivers a stable reversible capacity of 861 mA·h·g⁻¹ at the current density of 100 mA·g⁻¹ after 100 cycles. The capacity retention reaches as high as 54.5% even at 6000 mA·g⁻¹. The kinetic analysis indicates that the featured structural modification improves the surface condition of the CNT matrix, and contributes to greatly decreased interface impendence and faster charge transfer. In addition, the post-morphology observation of the tested sample further confirms the robustness of the Fe₃O₄@C/CNT configuration.