Morphology engineering of self-assembled nanostructured CuCo2O4 anodes for lithium-ion batteries

The electrochemical kinetics and output capacity of active electrode materials are significantly influenced by their surface structure. Herein, the template‐free morphological evolution of CuCo2O4 is reported, which is achieved by controlling the nucleation and growth rate during the hydrothermal process and evaluating its anode performance. The charge‐transfer resistance and specific surface area of the fabricated CuCo2O4 anode films are influenced by the viscosity of the solvent used. The optimized mesoporous nanosheet anode exhibits a high specific discharge capacity (1547 mAh g–1) at 0.1 A g–1 and an excellent restoring capability (≈91%); it retains 88% of the initial capacity with a coulombic efficiency of ≈99% even after 250 discharge–charge cycles. The superior lithium‐ion energy storage performance of this anode is due to its electrochemically favorable porous 2D morphology with large Brunauer–Emmett–Teller (BET) specific surface area and pore volume, resulting in enhanced Li+ storage and intercalation property

Optimal rule-of-thumb design of Nickel–Vanadium oxides as an electrochromic electrode with ultrahigh capacity and ultrafast color tunability

The use of electrodes capable of functioning as both electrochromic windows and energy storage devices has been extended from green building development to various electronics and displays to promote more efficient energy consumption. Herein, we report the electrochromic energy storage of bimetallic NiV oxide (NiVO) thin films fabricated using chemical bath deposition. The best optimized NiVO electrode with a Ni/V ratio of 3 exhibits superior electronic conductivity and a large electrochemical surface area, which are beneficial for enhancing electrochemical performance. The color switches between semitransparent (a discharged state) and dark brown (a charged state) with excellent reproducibility because of the intercalation and deintercalation of OH– ions in an alkaline KOH electrolyte. A specific capacity of 2403 F g–1, a coloration efficiency of 63.18 cm2 C–1, and an outstanding optical modulation of 68% are achieved. The NiVO electrode also demonstrates ultrafast coloration and bleaching behavior (1.52 and 4.79 s, respectively), which are considerably faster than those demonstrated by the NiO electrode (9.03 and 38.87 s). It retains 91.95% capacity after 2000 charge–discharge cycles, much higher than that of the NiO electrode (83.47%), indicating that it has significant potential for use in smart energy storage applications. The superior electrochemical performance of the best NiVO compound electrode with an optimum Ni/V compositional ratio is due to the synergetic effect between the high electrochemically active surface area induced by V-doping-improved redox kinetics (low charge-transfer resistance) and fast ion diffusion, which provides a facile charge transport pathway at the electrolyte/electrode interface

Nanoflake NiMoO4 based smart supercapacitor for intelligent power balance monitoring.

A supercapacitor is well recognized as one of emerging energy sources for powering electronic devices in our daily life. Although various kind of supercapacitors have been designed and demonstrated, their market aspect could become advanced if the utilisation of other physicochemical properties (e.g. optical) is incorporated in the electrode. Herein, we present an electrochromic supercapacitor (smart supercapacitor) based on a nanoflake NiMoO4 thin film which is fabricated using a facile and well-controlled successive ionic layer adsorption and reaction (SILAR) technique. The polycrystalline nanoflake NiMoO4 electrode exhibits a large electrochemically active surface area of ~ 96.3 cm2. Its nanoporous architecture provides an easy pathway for the intercalation and de-intercalation of ions. The nanoflake NiMoO4 electrode is dark-brown in the charged state and becomes transparent in the discharged state with a high optical modulation of 57%. The electrode shows a high specific capacity of 1853 Fg–1 at a current rate of 1 Ag–1 with a good coloration efficiency of 31.44 cm2/C. Dynamic visual information is obtained when the electrode is charged at different potentials, reflecting the level of energy storage in the device. The device retains 65% capacity after 2500 charge-discharge cycles compared with its initial capacity. The excellent performance of the nanoflake NiMoO4 based smart supercapacitor is associated with the synergetic effect of nanoporous morphology with a large electrochemically active surface area and desired chemical composition for redox reaction

Influence of operating temperature on Li2ZnTi3O8 anode performance and high-rate charging activity of Li-ion battery

The temperature-dependent performance of a Li2ZnTi3O8 (LZTO) anode and the ultrafast-charging activity of a Li-ion battery were investigated. The LZTO anode operates at different temperatures between − 5 and 55 °C and in this work its sustainability is discussed in terms of storage performance. It delivered a discharge capacity of 181.3 mA h g−1 at 25 °C, which increased to 227.3 mA h g−1 at 40 °C and 131.2 mA h g−1 at − 5 °C. The variation in the discharge capacity with temperature is associated with the reaction kinetics and the change in internal resistance. It showed a capacity retention of 64% and a coulombic efficiency of 98% over 500 cycles. Exhibiting a discharge capacity of 107 mA h g−1, the LZTO anode was sustainable over 100 charge-discharge cycles at an ultra-high charging rate of 10 Ag−1. The reaction kinetics estimated from a cyclic voltammetry analysis at high scan rates revealed a capacitive-type storage mechanism

Self-assembled nanostructured CuCo2 O4 for electrochemical energy storage and the oxygen evolution reaction via morphology engineering

CuCo2O4 films with different morphologies of either mesoporous nanosheets, cubic, compact‐granular, or agglomerated embossing structures are fabricated via a hydrothermal growth technique using various solvents, and their bifunctional activities, electrochemical energy storage and oxygen evolution reaction (OER) for water splitting catalysis in strong alkaline KOH media, are investigated. It is observed that the solvents play an important role in setting the surface morphology and size of the crystallites by controlling nucleation and growth rate. An optimized mesoporous CuCo2O4 nanosheet electrode shows a high specific capacitance of 1658 F g−1 at 1 A g−1 with excellent restoring capability of ≈99% at 2 A g−1 and superior energy density of 132.64 Wh kg−1 at a power density of 0.72 kW kg−1. The CuCo2O4 electrode also exhibits excellent endurance performance with capacity retention of 90% and coulombic efficiency of ≈99% after 5000 charge/discharge cycles. The best OER activity is obtained from the CuCo2O4 nanosheet sample with the lowest overpotential of ≈290 mV at 20 mA cm−2 and a Tafel slope of 117 mV dec−1. The superior bifunctional electrochemical activity of the mesoporous CuCo2O4 nanosheet is a result of electrochemically favorable 2D morphology, which leads to the formation of a very large electrochemically active surface area

A robust nonprecious CuFe composite as a highly efficient bifunctional catalyst for overall electrochemical water splitting

To generate hydrogen, which is a clean energy carrier, a combination of electrolysis and renewable energy sources is desirable. In particular, for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) in electrolysis, it is necessary to develop nonprecious, efficient, and durable catalysts. A robust nonprecious copper–iron (CuFe) bimetallic composite is reported that can be used as a highly efficient bifunctional catalyst for overall water splitting in an alkaline medium. The catalyst exhibits outstanding OER and HER activity, and very low OER and HER overpotentials (218 and 158 mV, respectively) are necessary to attain a current density of 10 mA cm−2. When used in a two‐electrode water electrolyzer system for overall water splitting, it not only achieves high durability (even at a very high current density of 100 mA cm−2) but also reduces the potential required to split water into oxygen and hydrogen at 10 mA cm−2 to 1.64 V for 100 h of continuous operation

Self-assembled two-dimensional copper oxide nanosheet bundles as an efficient oxygen evolution reaction (OER) electrocatalyst for water splitting applications

A high activity of a two-dimensional (2D) copper oxide (CuO) electrocatalyst for the oxygen evolution reaction (OER) is presented. The CuO electrode self-assembles on a stainless steel substrate via chemical bath deposition at 80 °C in a mixed solution of CuSO4 and NH4OH, followed by air annealing treatment, and shows a 2D nanosheet bundle-type morphology. The OER performance is studied in a 1 M KOH solution. The OER starts to occur at about 1.48 V versus the RHE (η = 250 mV) with a Tafel slope of 59 mV dec−1 in a 1 M KOH solution. The overpotential (η) of 350 mV at 10 mA cm−2 is among the lowest compared with other copper-based materials. The catalyst can deliver a stable current density of >10 mA cm−2 for more than 10 hours. This superior OER activity is due to its adequately exposed OER-favorable 2D morphology and the optimized electronic properties resulting from the thermal treatment

Nanofilament array embedded tungsten oxide for highly efficient electrochromic supercapacitor electrodes

The high-activity of metallic nanofilament array (NFA) embedded tungsten oxide (WO3) bifunctional electrodes for electrochromism and electrochemical energy storage is presented. The NFA reduces charge transfer resistance and increases the electrochemically active surface area at the electrode–electrolyte interface. The NFA-embedded WO3 electrode exhibits a specific capacity of 214 F g−1 (pristine WO3: 133 F g−1) at 0.25 mA cm−2, excellent cycling stability with ∼92% capacitance retention after 2000 cycles (pristine WO3: ∼75% capacitance retention) and a coloration efficiency of 128 cm2 C−1 (pristine WO3: 91 cm2 C−1) with superb optical modulation. These properties are significantly more advanced compared to the pristine WO3 electrode and superior to previously reported WO3-based composites and nanostructured materials

Nanoporous CuCo2O4 nanosheets as a highly efficient bifunctional electrode for supercapacitors and water oxidation catalysis

Efficient and low‐cost multifunctional electrodes play a key role in improving the performance of energy conversion and storage devices. In this study, ultrathin nanoporous CuCo2O4 nanosheets are synthesized on a nickel foam substrate using electrodeposition followed by air annealing. The CuCo2O4 nanosheet electrode exhibits a high specific capacitance of 1473 F g─1 at 1 A g─1 with a capacity retention of ∼93% after 5000 cycles in 3 M KOH solution. It also works well as an efficient oxygen evolution reaction electrocatalyst, demonstrating an overpotential of 260 mV at 20 mA cm─2 with a Tafel slope of ∼64 mV dec─1. in 1 M KOH solution, which is the lowest reported among other copper-cobalt based transition metal oxide catalysts. The catalyst is very stable at >20 mA cm─2 for more than 25 h. The superior electrochemical performance of the CuCo2O4 nanosheet electrode is due to the synergetic effect of the direct growth of 2D nanosheet structure and a large electrochemically active surface area associated with nanopores on the CuCo2O4 nanosheet surface

Direct growth of 2D nickel hydroxide nanosheets intercalated with polyoxovanadate anions as a binder-free supercapacitor electrode

A mesoporous nanoplate network of two-dimensional (2D) layered nickel hydroxide Ni(OH)2 intercalated with polyoxovanadate anions (Ni(OH)2–POV) was built using a chemical solution deposition method. This approach will provide high flexibility for controlling the chemical composition and the pore structure of the resulting Ni(OH)2–POV nanohybrids. The layer-by-layer ordered growth of the Ni(OH)2–POV is demonstrated by powder X-ray diffraction and cross-sectional high-resolution transmission electron microscopy. The random growth of the intercalated Ni(OH)2–POV nanohybrids leads to the formation of an interconnected network morphology with a highly porous stacking structure whose porosity is controlled by changing the ratio of Ni(OH)2 and POV. The lateral size and thickness of the Ni(OH)2–POV nanoplates are ∼400 nm and from ∼5 nm to 7 nm, respectively. The obtained thin films are highly active electrochemical capacitor electrodes with a maximum specific capacity of 1440 F g−1 at a current density of 1 A g−1, and they withstand up to 2000 cycles with a capacity retention of 85%. The superior electrochemical performance of the Ni(OH)2–POV nanohybrids is attributed to the expanded mesoporous surface area and the intercalation of the POV anions. The experimental findings highlight the outstanding electrochemical functionality of the 2D Ni(OH)2–POV nanoplate network that will provide a facile route for the synthesis of low-dimensional hybrid nanomaterials for a highly active supercapacitor electrode