NiCo2S4 multi-shelled hollow polyhedrons as high-performance anode materials for lithium-ion batteries

Catalytic chemistry inspired hollow carbon nanofibers loaded with NiS/Ni as high-performance and safe Li+ reservoir

Transition metal sulfides (TMSs) based anodes hold a very broad application prospect in lithium ion batteries (LIBs). In this work, the catalytic effect of metallic nickel at high temperature was used to generate hollow carbon nanofibers loaded with NiS and Ni (denoted as NiS/Ni@HCNF). The heteroatoms doped carbon fibers buffer the huge volumetric change of NiS during the discharge/charge process, and enhance the ion transport efficiency and electrical conductivity. In addition, the high specific surface area brought by the hollow carbon nanofibers can accelerate the electrolyte penetration and speed up the transport of ions as well as electrons. When used as anode of half cell, this electrode gives 958.5 and 612.9 mAh/g after running 1000 cycles under 1 and 2 A/g, showing the extremely-low attenuation rates of 0.0483 % per cycle and 0.0643 % per cycle, respectively. Impressively, NCM//NiS/Ni@HCNF battery shows the discharge capacity of 187.6 mAh/g at 1st cycle. Regarding the next 100 cycles, the relatively-high discharge capacities (>110 mAh/g) and coulombic efficiency (CE) values (>96 %) are discerned. It is noted that the usage of NiS/Ni@HCNF electrode improves the activation energy for thermal runaway, corroborating the elevated thermal safety of battery.

Synthesis and Characterization of MnIn2S4/Single-Walled Carbon Nanotube Composites as an Anode Material for Lithium-Ion Batteries

In this study, we synthesized a transition metal sulfide (TMS) with a spinel structure, i.e., MnIn2S4 (MIS), using a two-step hydrothermal and sintering process. In the context of lithium-ion battery (LIB) applications, ternary TMSs are being considered as interesting options for anode materials. This consideration arises from their notable attributes, including high theoretical capacity, excellent cycle stability, and cost-effectiveness. However, dramatic volume changes result in the electrochemical performance being severely limited, so we introduced single-walled carbon nanotubes (SWCNTs) and prepared an MIS/SWCNT composite to enhance the structural stability and electronic conductivity. The synthesized MIS/SWCNT composite exhibits better cycle performance than bare MIS. Undergoing 100 cycles, MIS only yields a reversible capacity of 117 mAh/g at 0.1 A/g. However, the MIS/SWCNT composite exhibits a reversible capacity as high as 536 mAh/g after 100 cycles. Moreover, the MIS/SWCNT composite shows a better rate capability. The current density increases with cycling, and the SWCNT composite exhibits high reversible capacities of 232 and 102 mAh/g at 2 A/g and 5 A/g, respectively. Under the same conditions, pristine MIS can only deliver reversible capacities of 21 and 4 mAh/g. The results indicate that MIS/SWCNT composites are promising anode materials for LIBs.

Designing of trimetallic-phase ternary metal sulfides coupled with N/S doped carbon protector for superior and safe Li/Na storage

Traditional transition metal sulfides (TMSs) have shown favorable potentials in energy storage. Nevertheless, its further usage is plagued by the issues of particle breakage and large volume change. In this work, the nanostructured ternary TMSs coupled with N/S doped carbon protector (NiCoFe-S@NSC) is delicately designed via compositional regulation and spatial structure protection strategies. As lithium ion batteries anode, this electrode gives an impressive capacity of 995.7 mAh/g after running 1000 cycles at 1 A/g. More importantly, NiCoFe-S@NSC electrode still shows a discharge capacity of 221.94 mAh/g after running 20,000 cycles at 10 A/g, reflecting an extremely-low capacity decay rate of 0.0377 ‰ per cycle. As sodium ion batteries anode, a high initial discharge capacity of 896.4 mA h g^-1 can be found. Even after running 400 cycles at 5 A/g, the electrode still displays a reversible capacity of 334.5 mAh/g with outstanding coulombic efficiency above 98.0 %. Impressively, LiNi_xCo_yMn_1-x-yO₂//NiCoFe-S@NSC full cell gives incipient discharge/charge capacities of 186.89/240.18 mAh/g. Moreover, the discharge capacities for the following 100 cycles remain above 150 mAh/g. Thermal runaway tests also demonstrate the higher thermal safety of cells with NiCoFe-S@NSC electrode, accompanying with the promoted activation energy.

Peroxymonosulfate activation through ferromagnetic bimetallic spinel sulfide composite (Fe3O4/NiCo2S4) for organic pollutant degradation

Spinel sulfides are a good candidate as heterogeneous catalysts for wastewater treatment through peroxymonosulfate (PMS) activation. In this paper, magnetic Fe₃O₄/NiCo₂S₄ composite was successfully synthesized by hydrothermal method. Catalyst screening displayed that the composite catalyst with a Fe₃O₄:NiCo₂S₄ molar ratio of 1:3 (i.e.,0.33-Fe₃O₄/NiCo₂S₄) is the most optimal. The results showed that 0.33-Fe₃O₄/NiCo₂S₄ composite catalyst had superior catalytic activity, achieving 99.8%,65.1% and 40.7% of RhB, COD and TOC removals within 30 min with 180 m g/L PMS and 75 mg/L catalyst. We proposed a potential catalytic mechanism of PMS activation by Fe₃O₄/NiCo₂S₄ in two aspects. On the one hand, sulfur species such as S^2- and S₂^2- enhance the Co³⁺/Co²⁺, Ni³⁺/Ni²⁺ and Fe³⁺/Fe²⁺ cycles on Fe₃O₄/NiCo₂S₄ surface. On the other hand, there is the synergistic effect of Co³⁺/Co²⁺, Ni³⁺/Ni²⁺ and Fe³⁺/Fe²⁺ cycles in activating PMS. Overall, owing to its excellent catalytic activity, reusability, and easy recovery, Fe₃O₄/NiCo₂S₄ is a potentially useful catalyst for remediation of contaminated water.

Anthozoan-like porous nanocages with nano-cobalt-armed CNT multifunctional layers as a cathode material for highly stable Na–S batteries

Co-armed CNTs as a unique physicochemical adsorption fence relieve the shuttle effect. The Co-armed CNT catalytic factory accelerates long-chain polysulfide conversion.

Preparation of heterogeneous NiCo2S4/Ru composite electrode materials and their electrocatalytic properties for hydrogen evolution

Nano-porous NiCo2S4 was prepared in situ. Ru nanoparticles were loaded onto a NiCo2S4 substrate by a solvothermal method to form the NiCo2S4/Ru composite electrode material and further vulcanized by CVD to obtain NiCo2S4/RuS2 as the contrast.

Template-free synthesis of β-NiS ball-in-ball microspheres for a high-performance asymmetrical supercapacitor

While significant advances have been made in the synthesis of core-/multi-shell materials, the synthetic process usually involves a soft/hard template and complicated procedures. In particular, it is extremely difficult to fabricate single-component core-shell structures for nickel sulfides (NSs) with a controlled phase. In this work, we demonstrate a novel facile method to synthesize a single-component β-NiS ball-in-ball microsphere. The ball-in-ball structure is easily obtained by uniquely employing 2-mercaptopropionic acid (2-MPA) as the sulfur source and ethanol as the solvent based on the Ostwald ripening process. In particular, our work demonstrates that the chemical structure of sulfur sources and solvents plays a key role in the formation of the pure β-NiS ball-in-ball structure. When used as an electrode active material, the β-NiS ball-in-ball microspheres exhibit two times stronger specific capacity and three times higher rate performance than NSs produced by a hydrothermal method. The fabricated NS-2//rGO asymmetrical supercapacitor (ASC) displays an energy density of 46.4 W h kg^-1 at a power density of 799.0 W kg^-1 and good cycling performance. Thus, this study provides a new method for controlling the phase and morphology of NSs.

Stacked Cu2-xSe nanoplates with 2D nanochannels as high performance anode for lithium batteries

Transition metal chalcogenides are considered as promising alternative materials for lithium-ion batteries owing to their relatively high theoretical capacity. However, poor cycle stability combined with low rate capacity still hinders their practical applications. In this work, the Cu-N chemical bonding directed the stacking Cu_2-xSe nanoplates (DETA-Cu_2-xSe) is developed to solve this issue. Such unique structure with small nanochannels can enhance the reactive site, facilitate the Li-ion transport as well as inhibit the structural collapse. Benefitting of these advantages, the DETA-Cu_2-xSe exhibits high specific capacity, better rate capacity and long cyclability with the specific capacities of 565mAhg^-1 after 100 cycles at 200 mA g^-1 and 368mAhg^-1 after 500 cycles at 5000 mA g^-1. This novel DETA-Cu_2-xSe structure with nanochannels is promising for next generation energy storage and the synthetic process can be extended to fabricate other transition metal chalcogenides with similar structure.

Pomegranate-like C@TiO2 mesoporous honeycomb spheres for high performance lithium ion batteries

Pomegranate-like C@TiO₂ mesoporous honeycomb spheres have been synthesized through two simple steps: formation of TiO₂ mesoporous honeycomb spheres and the coating of polypyrrole followed by carbonization. TiO₂ mesoporous honeycomb spheres are of large specific surface area of 153 m² g^-1 and contain abundant mesopores, which leads to high electrochemical activity and good kinetic performance of TiO₂. A layer of amorphous carbon shell with the thickness of 30-40 nm tightly encapsulates a TiO₂ mesoporous honeycomb sphere, forming a novel pomegranate-like small sphere, which significantly improves electronic conductivity and structural stability of TiO₂. Benefiting from the unique pomegranate-like structure, C@TiO₂ mesoporous honeycomb spheres exhibit high specific capacity, stable long-term cycling performance and good rate capability as an anode material for lithium ion batteries (LIBs). After 500 cycles at 1 C, the discharge capacity still reaches 184 mAh g^-1. The electrochemical performance is superior to pure TiO₂ mesoporous honeycomb spheres and most of the reported high-performance TiO₂-based composites. This work provides a new high-performance TiO₂-carbon-based composite material for LIBs as well as a new valuable research strategy.

Watermelon-like TiO2 nanoparticle (P25)@microporous amorphous carbon sphere with excellent rate capability and cycling performance for lithium-ion batteries

To overcome the inferior rate capability and cycling performance of TiO₂ nanomaterials as an anode material of lithium-ion batteries, we encapsulate TiO₂ nanoparticles (P25) in carbon spheres through a facile pyrrole polymerization and carbonization. Material characterization demonstrates TiO₂ nanoparticles are uniformly embedded in microporous amorphous carbon spheres, forming a watermelon-like structure. P25@C exhibits excellent high rate capability with average discharge capacity of 496, 416, 297, 240, 180, 99, 49 and 25 mAh g^-1 at current rate of 0.5C, 1C, 5C, 10C, 20C, 50C, 100C and 200C, which shows superior long-term cycling performance with discharge capacity of 106.9 mAh g^-1 at 20C after 5000 cycles. The capacity loss rate is only 0.008% per cycle. The outstanding lithium storage performance is ascribed to the watermelon-like composite structure, which remarkably improves electronic conductivity and structure stability of TiO₂ nanoparticles. More importantly, the agglomeration of TiO₂ nanoparticles is eliminated, and the entire surface of every TiO₂ nanoparticle participates in the electrochemical reaction, which brings about an intense capacitive Li storage effect and leads to the high specific capacity and excellent rate capability of P25@C. This is confirmed through qualitative and quantitative analysis of the contributions from surface capacitive storage and bulk intercalation storage to the total capacity of the composite.

3D porous framework of ZnO nanoparticles assembled from double carbon shells consisting of hard and soft carbon networks for high performance lithium ion batteries

Low electronic conductivity and large volume variation result in inferior lithium storage performance of ZnO. To overcome these shortcomings of ZnO, herein ZnO nanoparticles are encapsulated in resorcinol-formaldehyde resin-derived hard carbon and then further assembled into a 3-dimensional mesoporous framework structure using a polyvinyl pyrrolidone-derived soft carbon network. The synthesis methods include the polymerization of resorcinol-formaldehyde resin and a polyvinyl pyrrolidone-boiling method. ZnO@dual carbon has af large specific surface area (153.7 m² g^-1) and high porosity. It exhibits excellent cycling performance and high rate capability. After 350 cycles at 500 mA g^-1, the ZnO@dual carbon still delivers a discharge capacity of 701 mAh g^-1 while the actual discharge capacity of ZnO reaches 950.9 mAh g^-1. At 2 A g^-1, ZnO@dual carbon delivers the average discharge capacity of 469.6 mAh g^-1. The electrochemical performance of ZnO@dual carbon is remarkably superior to those of ZnO@single carbon, pure carbon and pure ZnO nanoparticles, demonstrating the superiority of the dual carbon-assembly structure. This composite structure greatly improves the structural stability of ZnO, enhances its electron conductivity and overall electron transport capacity; which facilitates electrolyte penetration and Li ion diffusion, leading to improved cycling stability and good rate capability.

Dual-functional NiCo2S4 polyhedral architecture with superior electrochemical performance for supercapacitors and lithium-ion batteries

Dual-functional NiCo₂S₄ polyhedral architectures with outstanding electrochemical performance for supercapacitors and lithium-ion batteries (LIBs) have been rationally designed and successfully synthesized by a hydrothermal method. The as-synthesized NiCo₂S₄ electrode for supercapacitor exhibits an outstanding specific capacitance of 1298Fg^-1 at 1Ag^-1 and an excellent rate capability of ~80.4% at 20Ag^-1. Besides, capacitance retention of 90.44% is realized after 8000 cycles. In addition, the NiCo₂S₄ as anode in LIBs delivers high initial charge/discharge capacities of 807.6 and 972.8mAhg^-1 at 0.5C as well as good rate capability. In view of these points, this work provides a feasible pathway for assembling electrodes and devices with excellent electrochemical properties in the next generation energy storage applications.

NiS2 nanoparticles anchored on open carbon nanohelmets as an advanced anode for lithium-ion batteries

Low intrinsic conductivity and large volume expansion seriously restrict the efficient lithium storage performance of metal sulfides. Here, we fabricate a hybrid material of NiS2 nanoparticles/carbon nanohelmets (NiS2/CNHs) to address the above issues. As an anode material in lithium-ion batteries, NiS2/CNHs exhibit excellent cycling stability (490 mA h g-1 after 3000 cycles at 5 A g-1) and rate properties (412 mA h g-1 at 10 A g-1), outperforming other NiS x -based anode materials. These remarkable performances originate from the three-dimensional helmet-like integrated architecture of NiS2/CNHs, which reduces the electrode resistance due to the tight combination between NiS2 and CNHs, provides efficient diffusion paths for the electrolyte and Li+ owing to the amorphous nanoporous carbon structure, and significantly mitigates the aggregation and buffers the large volumetric expansion of NiS2 nanoparticles upon long-term cycling thanks to the open three-dimensional architecture and well-dispersed NiS2 nanoparticles on it.

NiMoS4 nanocrystals anchored on N-doped carbon nanosheets as anode for high performance lithium ion batteries

Owing to the excellent electrical conductivity and high theoretical capacity, binary transition metal sulfides have attracted extensive attention as promising anodes for lithium ion batteries (LIBs). However, the relatively poor electrical conductivity and serious capacity fading originated from large volume change still hinder their practical applications. Herein, binary NiMoS₄ nanoparticles are deposited on N doped carbon nanosheets (NC@NiMoS₄) through a facile hydrothermal method. The N doped carbon nanosheets and the strong chemical bonding between NC and NiMoS₄ can accommodate the volume change, keep the structural integrity and promote the ion/electron transfer during electrochemical reaction. The extra voids between NiMoS₄ nanoparticles enlarge the contact area and reduce the lithium migration barriers. As anode for LIBs, the NC@NiMoS₄ exhibits the excellent cycle stability with 834 mAh g^-1 after 100 cycles at the current density of 100 mA g^-1. Even at high rate of 2000 mA g^-1, the specific capacity of 544 mAh g^-1 can be achieved after 500 cycles.

Construction of Co3O4 three-dimensional mesoporous framework structures from zeolitic imidazolate framework-67 with enhanced lithium storage properties

High-porosity mesoporous framework structures are attractive for electrochemical energy storage and other applications. Herein we demonstrate a novel synthesis strategy to make zeolitic imidazolate framework-67 oxidize to a Co₃O₄ three-dimensional mesoporous framework structure. This strategy relies on the oxygen-limitation effect of the closed nanocage and the affinity effect of polyvinylpyrrolidone towards zeolitic imidazolate framework-67. Several TiO₂ nanospheres, as the unique structure junctions, are uniformly embedded within the Co₃O₄ framework to enhance the framework strength. The TiO₂/hydrous titania polyhedron nanocage, as the protecting shell, further encapsulates the Co₃O₄ framework, forming a perfect capsule-type hybrid. As anode materials for lithium-ion batteries, TiO₂@Co₃O₄ framework capsules show superior lithium storage performance with high reversible capacity, stable cycling life and good rate capability. A reversible capacity of 1042 mAh g^-1 can be delivered after 200 cycles at a current density of 300 mA g^-1. The average discharge capacity over 200 cycles reaches 926 mAh g^-1. This demonstrates the superiority of this material structure and its great potential as an anode for high-performance lithium-ion batteries. This work indicates a new strategy to take advantage of metal-organic frameworks to synthesize their mesoporous framework derivatives.

Co3O4 hollow nanospheres/carbon-assembled mesoporous polyhedron with internal bubbles encapsulating TiO2 nanosphere for high-performance lithium ion batteries

Co₃O₄ hollow nanospheres 15 nm in the diameter were assembled to the mesoporous polyhedron together with carbon. Within the Co₃O₄ polyhedrons, the bubbles 300-500 nm in diameter were uniformly generated. Every bubble further encapsulated one TiO₂ nanosphere, forming a unique sphere-bubble structure. The specific surface area and the pore volume were calculated to be 97.85 and 0.31 cm³ g^-1. When evaluated as anode material for lithium ion batteries, the as-prepared material exhibited superior lithium storage properties with high specific capacity, excellent cycling stability and good rate capability. After 400 cycles, the discharge capacity of 609 mAh g^-1 was still delivered at current density of 335 mA g^-1. Even at a high current density of 2000 mA g^-1, the reversible capacity reached 296 mAh g^-1. The outstanding electrochemical performance was attributed to the unique hybrid structure, which avoids nanomaterial aggregation, promotes ion diffusion and electron transfer, accommodates volume change of Co₃O₄ during (de)lithiation process, enhances structure strength, cycling stability and space utilization ratio of the hollow material.