40 research outputs found
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 templateāfree 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 chargeātransfer 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 (1547āmAhāgā1) at 0.1āAāgā1 and an excellent restoring capability (ā91%); it retains 88% of the initial capacity with a coulombic efficiency of ā99% even after 250 dischargeācharge cycles. The superior lithiumāion energy storage performance of this anode is due to its electrochemically favorable porous 2D morphology with large BrunauerāEmmettāTeller (BET) specific surface area and pore volume, resulting in enhanced Li+ storage and intercalation property
Facile electrodeposition of high-density CuCo2O4 nanosheets as a high-performance Li-ion battery anode material
High-density CuCo2O4 nanosheets are grown on Ni foam using electrodeposition followed by air annealing for a Li-ion battery anode. The anode exhibits a high discharge capacity of 1244 mAh/g at 0.1 A/g (82% coulombic efficiency) and excellent high-rate performance with 95% capacity retention (1100 mAh/g after 200 cycles at 1 A/g). The outstanding battery performance of the CuCo2O4 anode is attributed to its binder-free direct contact to the current collector and high-density nanosheet morphology. The present experimental findings demonstrate that the electrodeposited binder-free CuCo2O4 material may serve as a safe, low-cost, long-cycle life anode for Li-ion batteries
Observation of Kondo condensation in a degenerately doped silicon metal
When a magnetic moment is embedded in a metal, it captures itinerant
electrons to form the Kondo cloud1,2, which can spread out over a few
micrometres3,4. For a metal with dense magnetic impurities such that Kondo
clouds overlap with each other, correlated ground states are formed. When the
impurities form a regular lattice, the result is a heavy fermion or
anti-ferromagnetic order depending on the dominant interaction5,6. Even in the
case of random impurities, overlapping Kondo clouds are expected to form a
coherent ground state. Here, we examine this issue by performing electrical
transport and high-precision tunnelling density-of-states (DOS) spectroscopy
measurements in a highly P-doped crystalline silicon metal where
disorder-induced localized magnetic moments exist7. We detect the Kondo effect
in the resistivity of the Si metal below 2 K and an exotic pseudogap in the DOS
with gap edge peaks at a Fermi energy below 100 mK. The DOS gap and peaks are
tuned by applying an external magnetic field and transformed into a metallic
Altshuler-Aronov gap8 in the paramagnetic disordered Fermi liquid (DFL) phase.
We interpret this phenomenon as the Kondo condensation, the formation of a
correlated ground state of overlapping Kondo clouds, and its transition to a
DFL. The boundary between the Kondo condensation and DFL phases is identified
by analysing distinct DOS spectra in the magnetic field-temperature plane. A
detailed theoretical analysis using a holographic method 9 , 10 , 11 reproduces
the unusual DOS spectra, 1, supporting our scenario. Our work demonstrates the
observation of the magnetic version of Bardeen-Cooper-Shrieffer (BCS) pair
condensation and will be useful for understanding complex Kondo systems.Comment: 34 pages,5+6 figures, accepted in nature physic
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 Fgā1 at a current rate of 1 Agā1 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 āāÆ5 and 55āÆĀ°C and in this work its sustainability is discussed in terms of storage performance. It delivered a discharge capacity of 181.3āÆmAāÆhāÆgā1 at 25āÆĀ°C, which increased to 227.3āÆmAāÆhāÆgā1 at 40āÆĀ°C and 131.2āÆmAāÆhāÆgā1 at āāÆ5āÆĀ°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 107āÆmAāÆhāÆgā1, the LZTO anode was sustainable over 100 charge-discharge cycles at an ultra-high charging rate of 10āÆAgā1. The reaction kinetics estimated from a cyclic voltammetry analysis at high scan rates revealed a capacitive-type storage mechanism
Stabilization of halide perovskites with silicon compounds for optoelectronic, catalytic, and bioimaging applications
Silicon belongs to group 14 elements along with carbon, germanium, tin, and lead in the periodic table. Similar to carbon, silicon is capable of forming a wide range of stable compounds, including silicon hydrides, organosilicons, silicic acids, silicon oxides, and silicone polymers. These materials have been used extensively in optoelectronic devices, sensing, catalysis, and biomedical applications. In recent years, silicon compounds have also been shown to be suitable for stabilizing delicate halide perovskite structures. These composite materials are now receiving a lot of interest for their potential use in various realāworld applications. Despite exhibiting outstanding performance in various optoelectronic devices, halide perovskites are susceptible to breakdown in the presence of moisture, oxygen, heat, and UV light. Silicon compounds are thought to be excellent materials for improving both halide perovskite stability and the performance of perovskiteābased optoelectronic devices. In this work, a wide range of silicon compounds that have been used in halide perovskite research and their applications in various fields are discussed. The interfacial stability, structureāproperty correlations, and various application aspects of perovskite and silicon compounds are also analyzed at the molecular level. This study also explores the developments, difficulties, and potential future directions associated with the synthesis and application of perovskiteāsilicon compounds. imag
Optimal rule-of-thumb design of NickelāVanadium 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 OHā ions in an alkaline KOH electrolyte. A specific capacity of 2403 F gā1, a coloration efficiency of 63.18 cm2 Cā1, 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 chargeādischarge 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
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, compactāgranular, 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 gā1 at 1 A gā1 with excellent restoring capability of ā99% at 2 A gā1 and superior energy density of 132.64 Wh kgā1 at a power density of 0.72 kW kgā1. The CuCo2O4 electrode also exhibits excellent endurance performance with capacity retention of 90% and coulombic efficiency of ā99% after 5000 charge/discharge cycles. The best OER activity is obtained from the CuCo2O4 nanosheet sample with the lowest overpotential of ā290 mV at 20 mA cmā2 and a Tafel slope of 117 mV decā1. 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
Nanoporous CuCo2O4 nanosheets as a highly efficient bifunctional electrode for supercapacitors and water oxidation catalysis
Efficient and lowācost 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 1473āÆFāÆgā1 at 1āÆAāÆgā1 with a capacity retention of ā¼93% after 5000 cycles in 3āÆM KOH solution. It also works well as an efficient oxygen evolution reaction electrocatalyst, demonstrating an overpotential of 260āÆmV at 20āÆmAāÆcmā2 with a Tafel slope of ā¼64āÆmVāÆdecā1. in 1āÆM KOH solution, which is the lowest reported among other copper-cobalt based transition metal oxide catalysts. The catalyst is very stable at >20āÆmAāÆcmā2 for more than 25āÆh. 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