CNTs@NC@CuCo2S4 nanocomposites: An advanced electrode for high performance lithium-ion batteries and supercapacitors

Bimetallic sulfides based hybrid anodes are constructed for high-performance lithium ion batteries

Transition metal sulfides (TMSs) are considered as one of the most promising anode materials for lithium-ion batteries (LIBs) in virtue of their high theoretical specific capacity, low cost and environmental friendliness. However, the intrinsic poor electron/ion transport, large volume change and the shuttle effect of polysulfides hinder their achievement of superb rate capability and cycle performance. Compared with the monometallic sulfides, bimetallic sulfides have superior electron transport capability and higher electrochemical activity. In this work, bimetallic CuCo2S4 nanomaterial is in-situ synthesized on copper foam (CF) substrate by a facile hydrothermal method. Benefiting from the introduction of heteroatoms and the construction of integrated hybrid structure, the bimetallic CuCo2S4/CF anode delivers a high specific capacity of ∼1707 mAh g-1 at 0.1 C and maintains ∼84 % of the initial capacity after 1000 cycles at 1.6 C (1 C = 1 A g-1). This work provides a strategy to utilize bimetallic sulfides as well as construct hybrid electrode of sulfides and conductive metallic frameworks.

Synergistic CuCoS-PANI materials for binder-free electrodes in asymmetric supercapacitors and oxygen evolution

In advanced electronics, supercapacitors (SCs) have received a lot of attention. Nevertheless, it has been shown that different electrode designs that are based on metal sulfides are prone to oxidation, instability, and poor conductance, which severely limits their practical application. We present a very stable, free-standing copper-cobalt sulfide doped with polyaniline as an electrode coated on nickel foam (CuCoS/PANI). The lightweight nickel foam encourages current collection as well as serving as a flexible support. The CuCoS-PANI electrode had a substantially greater 1659 C g-1 capacity at 1.0 A g-1. The asymmetric supercapacitor (ASC) can provide an impressive 54 W h kg-1 energy density while maintaining 1150 W kg-1 power. Additionally, when employed as an electrocatalyst in the oxygen evolution reaction, CuCoS/PANI exhibited a 200 mV overpotential and 55 mV dec-1 Tafel slope, demonstrating its effectiveness in facilitating the reaction.

Highly uniform platanus fruit-like CuCo2S4 microspheres as an electrode material for high performance lithium-ion batteries and supercapacitors

Platanus fruit-like CuCo₂S₄ microspheres were fabricated by using a facile hydrothermal method followed by a sulfidation process. As a lithium storage material, they deliver an outstanding initial specific capacity of 1119.3 mA h g^-1 at 0.05 A g^-1 and a high reversibility of 954 mA h g^-1 over 200 cycles even at 1 A g^-1. In addition, when applied in supercapacitors they display a superb specific capacitance of 824 F g^-1 at 1 A g^-1, even over 10 000 cycles and they can also maintain 75% retention at 5 A g^-1 and exhibit good reversibility. Furthermore, an advanced asymmetric supercapacitor (ASC) exhibits an advantageous energy density of 36.67 W h kg^-1 when the power density increases up to 750 W kg^-1. Additionally, the assembled device can easily light a 1.5 V bulb for several minutes. The excellent performance of CuCo₂S₄ is due to the bimetallic synergistic effect and the unique platanus fruit-like microsphere architecture, which can limit the restacking of the structure and provide suitable voids. This excellent performance confirms that platanus fruit-like CuCo₂S₄ microspheres are a promising electrode material for energy storge. This work will provide a new strategy to prepare high-performance bimetallic sulfide anode materials by a facile method.

Facile Preparation of CuCo2 S4 /Cu7.2 S4 Nanocomposites as High-Performance Cathode Materials for Rechargeable Magnesium Batteries*

Rechargeable magnesium batteries (RMBs) have been considered a promising energy-storage device due to their high energy density and high safety, but they still suffer from a lack of high-rate performance and cycle performance of the cathode. Nanosized CuCo₂ S₄ /Cu_7.2 S₄ composites have been synthesized for the first time by a facile solvothermal method. Herein, the magnesium ion storage behavior when applied in the cathode for RMBs is discussed. Electrochemical results demonstrated that the CuCo₂ S₄ /Cu_7.2 S₄ composites exhibit a high initial discharge capacity of 256 mAh g^-1 at 10 mA g^-1 and 123 mAh g^-1 at 300 mA g^-1 at room temperature and an outstanding long-term cyclic stability over 300 cycles at 300 mA g^-1 . Furthermore, the electrochemical storage mechanism demonstrated that the storage process of magnesium ion in the CuCo₂ S₄ /Cu_7.2 S₄ cathode is mainly driven by strong pseudocapacitive effects.

p-n Heterojunction Photocatalyst Mn0.5Cd0.5S/CuCo2S4 for Highly Efficient Visible Light-Driven H2 Production

It is highly important to develop efficient and cheap photocatalysts for hydrogen production. Herein, a series of p-n heterojunction Mn_0.5Cd_0.5S/CuCo₂S₄ has been successfully synthesized for the first time by the hydrothermal impregnation method. Mn_0.5Cd_0.5S/CuCo₂S₄ loading with 12 wt % CuCo₂S₄ shows the highest H₂ evolution rate of 15.74 mmol h^-1 g^-1 under visible light (λ ≥ 420 nm) irradiation, which is about 3.15 and 15.28 times higher than that of bare Mn_0.5Cd_0.5S (4.99 mmol h^-1 g^-1) and CuCo₂S₄ (1.03 mmol h^-1 g^-1), respectively. In addition, it shows a relatively good stability during the five recycle tests, with about 20% loss of reaction rate compared to that of the first cycle. The superior photocatalytic performance is attributed to the effective separation and transfer of photogenerated charge carriers because of the formation of the p-n junction. The samples are systematically characterized by X-ray diffraction, ultraviolet-visible (UV-vis), diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, X-ray photoelectron spectroscopy, photoluminescence, EIS, and so on. UV-vis and EIS show that CuCo₂S₄ can effectively improve the visible light response of Mn_0.5Cd_0.5S/CuCo₂S₄ and promote the electron transfer from CuCo₂S₄ to the conduction band of Mn_0.5Cd_0.5S, so as to improve the photocatalytic efficiency. This study reveals that the p-n heterojunction Mn_0.5Cd_0.5S/CuCo₂S₄ is a promising photocatalyst to explore the photocatalysts without noble metals.

The Progress of Cobalt-Based Anode Materials for Lithium Ion Batteries and Sodium Ion Batteries

Limited by the development of energy storage technology, the utilization ratio of renewable energy is still at a low level. Lithium/sodium ion batteries (LIBs/SIBs) with high-performance electrochemical performances, such as large-scale energy storage, low costs and high security, are expected to improve the above situation. Currently, developing anode materials with better electrochemical performances is the main obstacle to the development of LIBs/SIBs. Recently, a variety of studies have focused on cobalt-based anode materials applied for LIBs/SIBs, owing to their high theoretical specific capacity. This review systematically summarizes the recent status of cobalt-based anode materials in LIBs/SIBs, including Li+/Na+ storage mechanisms, preparation methods, applications and strategies to improve the electrochemical performance of cobalt-based anode materials. Furthermore, the current challenges and prospects are also discussed in this review. Benefitting from these results, cobalt-based materials can be the next-generation anode for LIBs/SIBs.

Supercapacitive Performances of Ternary CuCo2S4 Sulfides

Currently, ternary CuCo₂S₄ sulfides are intensively investigated as electrode materials for electrochemical capacitors due to their low cost, high conductivity, and synergistic effect. The research of CuCo₂S₄ materials for energy storage has gradually grown from 2016. The supercapacitive performances of CuCo₂S₄ electrodes for electrochemical capacitors are briefly reviewed in this work. The structure, morphology, and particle size of CuCo₂S₄ are related to the synthesis conditions and electrochemical performances. The thin films of CuCo₂S₄ nanostructures deposited on conductive substrates and their composites both show better properties than single CuCo₂S₄. CuCo₂S₄ and its composites reveal large potential for asymmetric capacitors, delivering high energy densities. However, there is still much new space remaining for future research. The possible development directions, challenges, and opportunities for CuCo₂S₄ materials are also discussed.

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.

Synthesis of single-phase CuCo2-xNixS4 for high-performance supercapacitors

Developing safe, efficient and environment-friendly energy storage systems continues to inspire researchers to synthesize new electrode materials. Doping or substituting host material by some guest elements has been regarded as an effective way to improve the performance of supercapacitors. In this work, single-phase CuCo_2-xNi_xS₄ materials were synthesized by a facile two-step hydrothermal method, where Co in CuCo₂S₄ was substituted by Ni. Cobalt could be easily substituted with Ni in a rational range to keep its constant phase. But, a high content of Ni resulted in a multi-phase composite. Among a series of CuCo_2-xNi_xS₄ materials with different Ni/Co mole ratios, CuCo_1.25Ni_0.75S₄ material presented a significantly high specific capacitance (647 F g^-1 or 272 C g^-1 at 1 A g^-1) and the best cycling stability (∼98% specific capacitance retention after 10,000 charge-discharge cycles), which was mainly due to the modified composition, specific single phase, higher electroconductivity, more electroactive sites and the synergistic effect between Ni and Co. Moreover, the assembled asymmetric capacitor using CuCo_1.25Ni_0.75S₄ as a positive electrode and activated carbon as a negative electrode delivered a high energy density of 31.8 Wh kg^-1 at the power density of 412.5 W kg^-1. These results demonstrated that ternary metal sulfides of CuCo_2-xNi_xS₄ are promising electrode materials for high-performance supercapacitors.

A bimetallic sulfide CuCo2S4 with good synergistic effect was constructed to drive high performance photocatalytic hydrogen evolution

In order to further improve the photocatalytic performance of the semiconductor photocatalyst, a photocatalytic hydrogen production performance was measured using a bimetallic sulfide photocatalyst. On this basis, the hydrogen production performance of the bimetallic sulfide CuCo₂S₄ (CCS-3) was compared with that of the single metal sulfides Cu₃₁S₁₆ and CoS₂. The results showed that the bimetallic sulfide CCS-3 significantly improved the photocatalytic hydrogen production performance. The unique structure of the bimetallic sulfide CCS-3 made the photocatalytic activity of H₂ 2.47 times and 178.08 times higher than that of Cu₃₁S₁₆ and CoS₂, respectively. In addition, the hydrogen production activity in CCS-3 was also very stable after XRD comparison before and after the reaction. The results of UV-visible diffuse reflectance spectroscopy showed that the visible light response range was significantly expanded, and the forbidden band width was smaller than that of Cu₃₁S₁₆ and CoS₂. Photoluminescence spectroscopy results showed that CCS-3 had the best quenching effect because of its unique structure, which improved the separation efficiency and electron transfer efficiency of photogenerated electrons and holes. This article demonstrated new design strategies that would bring new insights into hydrogen evolution photocatalysts.