The high performance of a pseudocapacitor electrode relies largely on a scrupulous design of nanoarchitectures and smart hybridization of bespoke active materials. We present a powerful two-step ...solution-based method for the fabrication of transition metal oxide core/shell nanostructure arrays on various conductive substrates. Demonstrated examples include Co(3)O(4) or ZnO nanowire core and NiO nanoflake shells with a hierarchical and porous morphology. The "oriented attachment" and "self-assembly" crystal growth mechanisms are proposed to explain the formation of the NiO nanoflake shell. Supercapacitor electrodes based on the Co(3)O(4)/NiO nanowire arrays on 3D macroporous nickel foam are thoroughly characterized. The electrodes exhibit a high specific capacitance of 853 F/g at 2 A/g after 6000 cycles and an excellent cycling stability, owing to the unique porous core/shell nanowire array architecture, and a rational combination of two electrochemically active materials. Our growth approach offers a new technique for the design and synthesis of transition metal oxide or hydroxide hierarchical nanoarrays that are promising for electrochemical energy storage, catalysis, and gas sensing applications.
We report a procedure to fabricate nanostructured Ni films via programmed electrochemical deposition from a choline-chloride-based ionic liquid at a high temperature of 90 °C. Three electrodeposition ...modes using constant voltage, pulse voltage, and reverse pulse voltage produce a variety of nanostructured Ni films with micro/nanobinary surface architectures, such as nanosheets, aligned nanostrips, and hierarchical flowers. The nanostructured Ni films possess face-centered cubic crystal structure. Amazingly, it is found that the electrodeposited Ni films deliver the superhydrophobic surfaces without any further modifications by low surface-energy materials, which might be attributed to the vigorous micro/nanobinary architectures and the surface chemical composition. The electrochemical measurements reveal that the superhydrophobic Ni film exhibit an obvious passivation phenomenon, which could provide enhanced corrosion resistance for the substrate in the aqueous solutions.
Silicon (Si) is promising for high capacity anodes in lithium‐ion batteries due to its high theoretical capacity, low working potential, and natural abundance. However, there are two main drawbacks ...that impede its further practical applications. One is the huge volume expansion generating during lithiation and delithiation progresses, which leads to severe structural pulverization and subsequently rapid capacity fading of the electrode. The other is the relatively low intrinsic electronic conductivity, therefore, seriously impacting the rate performance. In the past decades, numerous efforts have been devoted for improving the cycling stability and rate capability by rational designs of different nanostructures of Si materials and incorporations with some conductive agents. In this review, the authors summarize the exciting recent research works and focus on not only the synthesis techniques, but also the composition strategies of silicon nanostructures. The advantages and disadvantages of the nanostructures as well as the perspective of this research field are also discussed. We aim to give some reference for engineering application on Si anodes in lithium ion batteries.
The authors summarize the strategies that developed lately for improving the electrochemical performance of Si materials. Special focus in this review is the recent progresses in the rational fabrication of Si nanostructures with multiple morphologies, including nanoparticles, nanowires, thin films, and porous structures. Moreover, further improvement tactics, such as collaborating with carbonaceous materials, conductive polymers, and alloy materials are also discussed.
Electrochromism refers to the persistent and reversible change of optical properties by an applied voltage pulse.Electrochromic（EC）devices have been extensively studied because of their commercial ...applications in smart windows of green buildings,display devices and thermal control of equipments.In this review,a basic EC device design is presented based on useful oxides and solid-state electrolytes.We focus on the state-of-the-art research activities related to the structures of tungsten oxide（WO3）and nickel oxide（NiO）,summarizing the strategies to improve their EC performances and further applications of devices.
An elastic and safe electrolyte is demanded for flexible batteries. Herein, a stretchable solid electrolyte comprised of crosslinked elastic polymer matrix, poly(vinylidene ...fluoride‐hexafluoropropylene) (PVDF‐HFP), and flameproof triethyl phosphate (TEP) is fabricated, which exhibits ultrahigh elongation of 450%, nonflammability and ionic conductivity above 1 mS cm−1. In addition, in order to improve the interface compatibility between the electrolyte and Li anode and stabilize the solid‐electrolyte interphase (SEI), a protecting layer containing poly(ethylene oxide) (PEO) is designed to effectively prevent the anode from reacting with TEP and optimize the chemical composition in SEI, leading to a tougher and more stable SEI on the anode. The LiFePO4/Li cells employing this double‐layer electrolyte exhibit an 85.0% capacity retention after 300 cycles at 1 C. Moreover, a flexible battery based on this solid electrolyte is fabricated, which can work in stretched, folded, and twisted conditions. This design of a stretchable double‐layer solid electrolyte provides a new concept for safe and flexible solid‐state batteries.
A stretchable polymer electrolyte is fabricated based on resilient copolymer and poly(vinylidene fluoride‐hexafluoropropylene) (PVDF‐HFP) with ultrahigh elasticity, nonflammability, and good ionic conductivity. A protective layer containing poly(ethylene oxide) (PEO) is designed to protect the electrolyte against the anode and stabilize the solid‐electrolyte interphase (SEI) during cycling. A flexible solid‐state battery is prepared using this double‐layer electrolyte, which can light a light emitting diode (LED) bulb under different deformed conditions.
Polyethylene oxide (PEO)-based solid electrolytes, which exhibit ideal extensibility and wide electrochemical window, are considered as one of the most promising candidates for all solid-state sodium ...batteries (ASSSBs). However, the low mechanical strength and low ionic conductivity hinder their application. Herein, electrospun MgAl
2
O
4
nanofibers are complexed with PEO/NaClO
4
to enhance the mechanical and thermal stability. Determined by
23
Na solid-state nuclear magnetic resonance spectroscopy combined with first-principle calculations, the adsorption energy of ClO
4
−
on the MgAl
2
O
4
surface is far higher than that on PEO, which facilitates the dissociation of Na
+
and ClO
4
−
, thereby enabling a fast transport of Na
+
by the introduction of MgAl
2
O
4
in the polymer electrolyte. The ionic conductivity is enhanced to 1.89 × 10
−4
S cm
−1
from 8.46 × 10
−5
S cm
−1
at 55 °C, and the Na
+
transfer number is improved to 0.55 from 0.26 in the composite electrolyte. The Na//(PEO/MgAl
2
O
4
/NaClO
4
)//Na symmetric cell can cycle for over 400 h at a current density of 0.05 mA cm
−2
and a cut-off capacity of 0.05 mAh cm
−2
while the ASSSBs incorporating the polymer composite electrolyte also exhibit notable rate and cycle performances.
Lithium ion batteries （LIBs） represent one of the most promising solutions for environmentally friendly transportation such as electric vehicles. The demand for high energy density, low cost and ...environmentally friendly batteries makes high-capacity cathode materials very attractive for future LIBs. Layered LiNixCoyMn2O2 （x＋y＋z=1）, Li-rich oxides and Li-V-O compounds have attracted much attention due to their high capacities in recent years. In this review, we focus on the state-of-the-art research activities related to LiNixCoyMn2O2, Li-rich oxides and Li-V-O compounds, including their structures, reaction mechanisms during cycling, challenges and strategies that have been studied to improve their electrochemical performances.
Electrolytic copper foil is ideal for use in the anode current collectors of lithium-ion batteries (LIBs) because of its abundant reserves, good electrical conductivity, and soft texture. However, ...electrolytic copper foil is prone to corrosion in electrolytes and weak bonding to the anode substance. Surface modification of copper foil is considered an effective method of improving the overall electrochemical performance of LIBs. In this study, a 5 nm thickness phytic acid (PA)-based film is constructed on electrolytic copper foil using a fast electrodeposition process (about 10 s). PA-treated copper foil (PA-Cu) displays an improved corrosion resistance in electrolytes because of a strong complexation between the PA and copper. It is found that PA-treated copper foil also bonds better with graphite particles compared with pristine copper foil. LIBs with PA-Cu foils as their current collectors exhibit enhanced cycling stability, improved capacity retention, and superior rate performance at both low and high current densities. Our study offers a novel avenue for the development of high-performance electrode current collector materials for LIBs.
As-prepared WO(3) nanostructure films on alumina or tungsten substrates by a facile hydrothermal method exhibit a superhydrophilic property. An effective strategy is proposed to control the ...wettability of WO(3) films in a reversible manner between superhydrophilicity and superhydrophobicity with a rapid response. By controlling the process of adsorption/desorption of n-dodecanethiol associated with the light-induced plating Ag nano-grains on WO(3) nanostructures, it only takes about 25 min to fulfill the wettability change from superhydrophilicity to superhydrophobicity, and only 30 s to finish the reversed change. Moreover, the contact angles of WO(3) surface can be tuned by controlling the etching time of superhydrophobic WO(3) surfaces in a solution of nitric acid containing 5 mM sodium dodecyl benzene sulfonate. Electrowetting process is successfully demonstrated to trap a water drop onto the superhydrophobic WO(3) surfaces. Considering WO(3) is one of typical electrochromic materials, researches on the effect of coupling between electrowetting and electrochromic properties would be more promising.
Highlights
Defect engineering for constructing Zn
2+
reservoir to anchor anions.
The quasi-solid electrolyte interphase as Zn
2+
reservoir boosting charge and mass transfer for dendrite-free zinc ...battery.
A Coulombic efficiency of 99.8% was achieved in Zn||Cu cell.
The practical applications of zinc metal batteries are plagued by the dendritic propagation of its metal anodes due to the limited transfer rate of charge and mass at the electrode/electrolyte interphase. To enhance the reversibility of Zn metal, a quasi-solid interphase composed by defective metal–organic framework (MOF) nanoparticles (D-UiO-66) and two kinds of zinc salts electrolytes is fabricated on the Zn surface served as a zinc ions reservoir. Particularly, anions in the aqueous electrolytes could be spontaneously anchored onto the Lewis acidic sites in defective MOF channels. With the synergistic effect between the MOF channels and the anchored anions, Zn
2+
transport is prompted significantly. Simultaneously, such quasi-solid interphase boost charge and mass transfer of Zn
2+
, leading to a high zinc transference number, good ionic conductivity, and high Zn
2+
concentration near the anode, which mitigates Zn dendrite growth obviously. Encouragingly, unprecedented average coulombic efficiency of 99.8% is achieved in the Zn||Cu cell with the proposed quasi-solid interphase. The cycling performance of D-UiO-66@Zn||MnO
2
(~ 92.9% capacity retention after 2000 cycles) and D-UiO-66@Zn||NH
4
V
4
O
10
(~ 84.0% capacity retention after 800 cycles) prove the feasibility of the quasi-solid interphase.
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