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Assorted nanoclay composites with sustainable, safer features and innovations are described for multifaceted applications.

A suitable interface between the electrode and electrolyte is crucial in achieving highly stable electrochemical performance for Li-ion batteries, as facile ionic transport is required. Recently, intriguing research and development have been carried out to form a stable interface between the electrode and electrolyte. Therefore, it is essential to investigate emerging knowledge and contextualize it. The nanoengineering of the electrode-electrolyte interface has been actively researched both at the electrode/electrolyte and interphase levels, which calls for significant attention. This review presents and summarizes some recent advances aimed at nanoengineering approaches to build a more stable electrode-electrolyte interface and assess the impact of each approach adopted. Furthermore, future perspectives on the feasibility and practicality of each approach will also be reviewed in detail. Finally, this review aids in projecting a more sustainable research pathway for a nanoengineered interphase design between electrode and electrolyte, which is pivotal for high-performance, thermally stable Li-ion batteries.

Attributed to its high safety and fast charging capabilities, supercapacitor is one of the most widely active research fields in the energy storage for last several decades. Recently, with the significant advances on the internet-of-things (IoT) technologies as well as growing market demands for wearable electronics, not only the electrochemical performance but also visual aspects of the devices become increasingly important. In this aspect, electrochromic supercapacitor has garnered significant attention in the last decade, which exhibits both color transition and reversible charge/discharge. So far, although some works have been devoted to investigating on the materials and/or components of electrochromic supercapacitor, none of the works have carefully investigated and analyzed the history, research progress, and future directions for electrochromic supercapacitor. In this review, the research progress and advances in the electrochromic supercapacitor are summarized, as well as suggestion for future directions for the electrochromic supercapacitor, which makes an early projection for future research on electrochromic supercapacitor.

The fibrous supercapacitor is a promising candidate for wearable energy-storage systems due to excellent mechanical reliability under deformation. In this study, a mechanically reliable fibrous supercapacitor with high volumetric power density and energy density was developed using fiber electrodes composed of multilayered active materials coated on silk yarns. The conductive silk yarn electrodes are fabricated via a sequential dip-coating process of silver nanowires, multi-walled carbon nanotubes (MWCNT, three to seven walls), and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The composite-coated silk yarn electrodes were stable under cyclic bending as well as under washing in water. Due to the synergetic effect of the three conducting materials, an excellent electrochemical performance was obtained resulting in high volumetric energy and power densities of 8–13 mWh cm−3 and 8–19 W cm−3, respectively. A yarn-type supercapacitor was demonstrated by integrating composite-coated silk yarn electrodes with a hydrogel electrolyte, showing a promising stability as evidenced by the retention of over 94% and 93% of the specific capacitance after 90-degree bending and stretching.

Graphene liquid cell electron microscopy (GLC-EM), a cutting-edge liquid-phase EM technique, has become a powerful tool to directly visualize wet biological samples and the microstructural dynamics of nanomaterials in liquids. GLC uses graphene sheets with a one carbon atom thickness as a viewing window and a liquid container. As a result, GLC facilitates atomic-scale observation while sustaining intact liquids inside an ultra-high-vacuum transmission electron microscopy chamber. Using GLC-EM, diverse scientific results have been recently reported in the material, colloidal, environmental, and life science fields. Here, the developments of GLC fabrications, such as first-generation veil-type cells, second-generation well-type cells, and third-generation liquid-flowing cells, are summarized. Moreover, recent GLC-EM studies on colloidal nanoparticles, battery electrodes, mineralization, and wet biological samples are also highlighted. Finally, the considerations and future opportunities associated with GLC-EM are discussed to offer broad understanding and insight on atomic-resolution imaging in liquid-state dynamics.

Organic carbonyl compounds have achieved great success as prospective electrodes for rechargeable metal-ion batteries for the replacement of commercial inorganic electrodes, since the extensive chemistry of organics allows to vary the structure in an eco-friendly manner to tune electrochemical properties. However, the ease of dissolution in electrolyte, intrinsically poor electronic conductivity, and low volumetric energy density greatly restrict their long-term cyclability and rate capability, impeding their widespread usage, especially for practical battery systems. Considering this, a great number of molecular engineering strategies have been proposed to overcome the above obstacles. In this review, we have summarized several commonly used molecular engineering approaches to reinforce the electrochemical performance of carbonyl organic compounds and simultaneously generalized the advantages and disadvantages of each strategy. Some recent key investigations on the reaction mechanism of carbonyl organic electrodes by using operando and ex situ techniques as well as theoretical calculations have also been highlighted. More importantly, different from most of the previous reviews focused on materials design, some critical challenges and future perspectives of carbonyl organic electrodes for practical battery systems have been evaluated in more depth. Therefore, this review will offer fundamental and useful guidance not only for the rational design of carbonyl electrodes but also for practical carbonyl-based battery systems applicable in the foreseeable future.

The development of high-tap density electrode materials that can simultaneously achieve stable electrochemical performance at high charge/discharge rates is critically in demand. Herein, we propose an innovative material design that can offer high tap density and excellent rate capabilities by using Co3O4 nanograin-interconnected secondary particles (Co3O4 NISPs). By taking advantage of a conversion reaction that forms Co from Co3O4, we demonstrate that Co3O4 NISPs are capable of creating a number of metallic Co sites along with a number of vacant sites in-between nanograins. Electrochemical tests that reveal reduced internal cell resistance and more accessible Li diffusion are achieved for Co3O4 NISPs compared with Co3O4 nanoparticles (NPs). Additionally, in situ X-ray diffraction (XRD) analyses, electron energy loss spectroscopy (EELS), and density functional theory (DFT) calculations reveal that the insulating intermediate product (CoO) is formed less on the Co3O4 NISPs, which can enhance the charge transport. Attributed to the combinatorial effects of Co3O4 nanograins that form metallic Co upon conversion and secondary particles that enable high tap density, Co3O4 NISPs show the most outstanding volumetric capacity (2167.3 mA h cm−3 at a current density of 500 mA g−1) among spinel-type metal oxide electrode materials researched so far.

It is evident that the exhaustive use of fossil fuels for decades has significantly contributed to global warming and environmental pollution. To mitigate the harm on the environment, lithium-oxygen batteries (LOBs) with a high theoretical energy density (3458 Wh kg-1Li2O2) compared to that of Li-ion batteries (LIBs) have been considered as an attractive alternative to fossil fuels. For this purpose, porous carbon materials have been utilized as promising air cathodes owing to their low cost, lightness, easy fabrication process, and high performance. However, the challenge thus far lies in the uncontrollable formation of Li2CO3 at the interface between carbon and Li2O2, which is detrimental to the stable electrochemical performance of carbon-based cathodes in LOBs. In this work, we successfully protected the surface of the free-standing carbon nanofibers (CNFs) by coating it with a layer of iridium metal through direct sputtering (CNFs@Ir), which significantly improved the lifespan of LOBs. Moreover, the Ir would play a secondary role as an electrochemical catalyst. This all-in-one cathode was evaluated for the formation and decomposition of Li2O2 during (dis)charging processes. Compared with bare CNFs, the CNFs@Ir cathode showed two times longer lifespan with 0.2 VLi lower overpotentials for the oxygen evolution reaction. We quantitatively calculated the contents of CO32- in Li2CO3 formed on the different surfaces of the bare CNFs (63% reduced) and the protected CNFs@Ir (78% reduced) cathodes after charging. The protective effects and the reaction mechanism were elucidated by ex situ analyses, including scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy.

A relatively low compressive strength significantly limits the practical application of sponges made from electrospun fibers because of an ultralow density

The disposal of natural wastes has become a global problem and the use of lower-grade gums is very limited owing to their impurities as well as sticky nature. Rather than disposing these wastes, nanoporous carbon (nC) has instead been synthesized by carbonization and exfoliation. The synthesized nC exhibits a substantially high surface area along with abundant micro/mesopores. This desirable and useful nature of nC is well-suited for water-driven effective electrical energy conversion, which enables the fast evaporation of water via a capillary action through nanopores. Under asymmetric wetting in a water container and ambient conditions, the nC-based energy harvesters showed high capability of electricity production and reliable output generation, easily turning on a blue light-emitting diode (2.5 V and 20 mA) using a stored power source. In summary, many energy harvesters can be manufactured for the scale-up of electricity, and the suitability of regenerated carbon nanomaterials for green energy harvesting can contribute toward alleviating chronic environmental issues.

To reduce the dependency on petro-based conventional plastics, research focusing on bioplastics derived from biological origin has gained precedence. Herein, we report an ecofriendly and a facile s...

To meet the increasing demands of electric vehicle applications for long ranges, Si-based materials have been intensively investigated as promising candidates for outstanding anodes of lithium-ion ...

For the last two decades, nanostructured carbon materials have attracted significant attention, as they exhibit unusual physicochemical properties different from their bulk counterpart. Nevertheless, agglomeration and re-stacking of carbon nanostructures have always limited optimal performance, with larger loading amount. To solve this issue, porous and compressible carbon-based sponges have been researched, but most of the previously suggested carbon foams were either not very porous, synthesized at high temperature heat treatment, and/or not applicable for carbon nanoparticles. In this work, we have successfully fabricated ultra-porous (porosity about 98–99%), polyimide-carbon nanoparticle (PI–C) composites by combining Ketjen black nanoparticles with PI short fibers, by simple freeze-drying and subsequent heat treatments at low temperature (240 °C). Based on the analysis, it has been discovered that the fabricated PI-C sponges not only exhibit highly robust mechanical properties but also retain low thermal conductivity even in comparison with pristine PI sponges. This work provides a milestone in fabricating a number of C-electrospun polymeric sponges by freeze drying and subsequent heat treatments, which are expected to be utilized in various fields of research.

Natural gum derived from the natural surrounding (gum arabic, guar gum, xanthan gum, gellan gum, fenugreek gum, karaya gum, and acacia gum) is one of the most abundant polysaccharides currently present around the world. As natural gum dissolved solution can be very sticky in nature, its role as a binder for both anodes and cathodes in rechargeable batteries have been recently significantly researched. Although much research has been delved into using natural gum as a feasible binder for rechargeable batteries, little investigation so far has taken place to compile, summarize, analyze, and evaluate the current status-quo of the natural gum-based binder research, as well as understanding some of the obstacles and issues that may need to be addressed. This review gives a comprehensive review on the natural gum-based binder that was used for both anode and cathode in rechargeable batteries and how each kind of natural gum improved the electrochemical performance in terms of cycle retention and rate capabilities. Furthermore, more systematic analysis and future projections for the research on natural gum-based binders are presented, which will serve to further the promising research related to utilizing natural gum as an efficient binder for rechargeable battery systems.

As it governs the overall performance of lithium-ion batteries, understanding the reaction pathway of lithiation is highly desired. For Co3O4 nanoparticles as anode material, here, we report an initial conversion reaction pathway during lithiation. Using graphene liquid cell electron microscopy (GLC-EM), we reveal a CoO phase of the initial conversion product as well as morphological dynamics during Co3O4 lithiation. In accordance with the in situ TEM observation, we confirmed that the Co3O4 to CoO conversion is a thermodynamically favorable process by calculating the theoretical average voltage based on density functional theory. Our observation will provide a useful insight into the oxide electrode that undergoes conversion reaction.

Flexible and stretchable electrochromic supercapacitor systems are widely considered as promising multifunctional energy storage devices that eliminate the need for an external power source. Nevertheless, the performance of conventional designs deteriorates significantly as a result of electrode/electrolyte exposure to atmosphere as well as mechanical deformations for the case of flexible systems. In this study, we suggest an all-transparent stretchable electrochromic supercapacitor device with ultrastable performance, which consists of Au/Ag core–shell nanowire-embedded polydimethylsiloxane (PDMS), bistacked WO3 nanotube/PEDOT:PSS, and polyacrylamide (PAAm)-based hydrogel electrolyte. Au/Ag core–shell nanowire-embedded PDMS integrated with PAAm-based hydrogel electrolyte prevents Ag oxidation and dehydration while maintaining ionic and electrical conductivity at high voltage even after 16 days of exposure to ambient conditions and under application of mechanical strains in both tensile and bending condit...

Development of feasible electrode materials is significant to realize high energy density Li-ion batteries (LIBs). Tin(IV) oxide, in particular, has a number of merits including higher theoretical capacity compared with graphite (1493 mAh g–1), low cost, and environmental friendliness. Nevertheless, huge volume changes and subsequent pulverization usually resulted in poor capacity retention of SnO2, where various nanostructures have been adopted to overcome its intrinsic limitations. Here we introduce the new insights into employing polycrystalline dense SnO2 nanospheres (NSs), rather than its hollow structures, as high-performance electrode for LIBs. Contrary to the previous notions, polycrystalline dense SnO2 NSs can exhibit highly stable cycle retention characteristics (1009.9 mAh g–1 after 300 cycles at 0.5 A g–1) as well as considerable rate capabilities (349 mAh g–1 at 5.0 A g–1), even superior to those of polycrystalline hollow SnO2 NSs. Based on the in situ TEM analyses and electrochemical/postmor...

Stable electrode materials with guaranteed long-term cyclability are indispensable for advanced lithium-ion batteries. Recently, delafossite CuFeO2 has received considerable attention, due to its relative structural integrity and cycling stability. Nevertheless, the low conductivity of delafossite and its relatively low theoretical capacity prevent its use as feasible electrodes for next-generation batteries that require higher reversible capacities. In this work, we suggest a simple and straightforward approach to prepare CuFeO2–NiFe2O4 by introducing Ni precursor into Cu and Fe precursor to form NiFe2O4, which exhibits higher capacity but suffers from capacity fading, through sol–gel process and subsequent heat treatments. The presence of both NiFe2O4 and CuFeO2 is apparent, and the heterostructure arising from the formation of NiFe2O4 within CuFeO2 renders some synergistic effects between the two active materials. As a result, the CuFeO2–NiFe2O4 hybrid sample exhibits excellent cycling stability and improved rate capability, and can deliver stable electrochemical performance for 800 cycles at a current density of 5.0 A g−1. This work is an early report on introducing a foreign element into the sol–gel process to fabricate heterostructures as electrodes for batteries, which open up various research opportunities in the near future.

Recently, quantum dots (QDs) have often garnered significant attention and have been employed for various applications. Nevertheless, most conventional devices utilize a glass substrate and/or brittle substrate, which is not compatible with next-generation wearable electronics. A suitable method for devising conductive and flexible free-standing platforms that can be combined with various kinds of QDs is thus in great need for next-generation wearable electronics. In this work, we introduce a universal and simple method to coat QDs on carbon nanofibers (CNFs) by a dip-coating process, where many kinds of QDs can be well decorated on the surface of CNFs. As one potential application among many, QD-coated CNFs were examined for their photocatalytic applications and characterization. As a result, it was found that the best performance of CdSe QD-coated CNFs for hydrogen production was 3.8 times higher than that of only QDs with the same 1 mg of QDs. This is an early report on fabricating various kinds of QD-coated CNFs, which can be extended to a myriad set of applications.

The fusion of different electroactive components of lithium-ion batteries (LIBs) sometimes brings exceptional electrochemical properties. We herein report the reduced graphene-oxide (rGO)-coated Zn2SnO4z@NiO nanofibers (ZSO@NiO@G NFs) formed by the synergistic fusion of three different electroactive components including ZnO, SnO2, and NiO that exhibit exceptional electrochemical properties as negative electrodes for LIBs. The simple synthetic route comprised of electrospinning and calcination processes enables to form porous one-dimensional (1D) structured ZSO, which is the atomic combination between ZnO and SnO2, exhibiting effective strain relaxation during battery operation. Furthermore, the catalytic effect of Ni converted from the surface-functional NiO nanolayer on ZSO significantly contributes to improved reversible capacity. Finally, rGO sheets formed on the surface of ZSO@NiO NFs enable to construct electrically conductive path as well as a stable SEI layer, resulting in excellent electrochemical performances. Especially, exceptional cycle lifespan of more than 1600 cycles with a high capacity (1060 mAh g-1) at a high current density (1000 mA g-1), which is the best result among mixed transition metal oxide (stannates, molybdates, cobaltates, ferrites, and manganates) negative electrodes for LIBs, is demonstrated.

Electrospinning has garnered significant attention in view of its many advantages such as feasibility for various polymers, scalability required for mass production, and ease of processing. Extensive studies have been devoted to the use of electrospinning to fabricate various electrospun nanofibers derived from carbohydrate gum polymers in combination with synthetic polymers and/or additives of inorganic or organic materials with gums. In view of the versatility and the widespread choice of precursors that can be deployed for electrospinning, various gums from both, the plants and microbial-based gum carbohydrates are holistically and/or partially included in the electrospinning solution for the preparation of functional composite nanofibers. Moreover, our strategy encompasses a combination of natural gums with other polymers/inorganic or nanoparticles to ensue distinct properties. This early established milestone in functional carbohydrate gum polymer-based composite nanofibers may be deployed by specialized researchers in the field of nanoscience and technology, and especially for exploiting electrospinning of natural gums composites for diverse applications.