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Herein, we report synthesis of Co3V2O8 nanoparticles for an electrocatalyst of seawater batteries. The cell using Co3V2O8 achieves a higher voltage efficiency of ∼76% than ∼72% of the cell without catalyst. In addition, the Co3V2O8 shows a good rate capability with reduced voltage gaps and an increased power density of ∼5.9 mW cm−2. This cell is stable over 20 cycles for 400 h with reduced voltage gap of ∼0.95 V. These findings are attributed to the facilitated redox kinetics of the clustered Co3V2O8 nanoparticles arising from the optimal metal OH bond strength and large surface area.

Carbon is a simple, stable and popular element with many allotropes. The carbon family members include carbon dots, carbon nanotubes, carbon fibers, graphene, graphite, graphdiyne and hard carbon, etc. They can be divided into different dimensions, and their structures can be open and porous. Moreover, it is very interesting to dope them with other elements (metal or non-metal) or hybridize them with other materials to form composites. The elemental and structural characteristics offer us to explore their applications in energy, environment, bioscience, medicine, electronics and others. Among them, energy storage and conversion are extremely attractive, as advances in this area may improve our life quality and environment. Some energy devices will be included herein, such as lithium-ion batteries, lithium sulfur batteries, sodium-ion batteries, potassium-ion batteries, dual ion batteries, electrochemical capacitors, and others. Additionally, carbon-based electrocatalysts are also studied in hydrogen evolution reaction and carbon dioxide reduction reaction. However, there are still many challenges in the design and preparation of electrode and electrocatalytic materials. The research related to carbon materials for energy storage and conversion is extremely active, and this has motivated us to contribute with a roadmap on 'Carbon Materials in Energy Storage and Conversion'.

Monoclinic vanadium dioxide (VO2(B)) is considered as a promising cathode material for lithium ion batteries (LIBs) owing to its high capacity, short ion diffusion channel, and multiple oxidation states. However, VO2(B) is technically limited due to its low electronic conductivity and large volume expansion. In order to resolve these drawbacks, we develop a mesoporous composite of reduced graphene oxide (rGO) and VO2(B) for enhanced rate capability and cycle life of LIB cathode. The uniform deposition of VO2(B) nanorods onto the mesoporous surface of the rGO architecture provides a facile access of Li ions to the storage site, large accessible area, short diffusion pathway, and chemical and mechanical stabilities. The VO2(B)/rGO composite electrode achieves a high capacity of 226 mA h g−1 at current density of 50 mA g−1 and superior capacity retention of 67.5% even at 40 times increase in current density up to 2000 mA g−1. In addition, this composite electrode demonstrates long cyclic stability of 88.5% after 500 cycles at 1000 mA g−1. In situ synchronous X-ray absorption spectroscopic data confirms a reversible change of the local structure and valence state evolution during a charging and discharging process.

Sodium ion batteries are an emerging candidate to replace lithium ion batteries in large-scale electrical energy storage systems due to the abundance and widespread distribution of sodium. Despite the growing interest, the development of high-performance sodium cathode materials remains a challenge. In particular, polyanionic compounds are considered as a strong cathode candidate owing to their better cycling stability, a flatter voltage profile, and stronger thermal stability compared to other cathode materials. Here, we report the rational design of a biomimetic bone-inspired polyanionic Na3V2(PO4)3-reduced graphene oxide composite (BI-NVP) cathode that achieves ultrahigh rate charging and ultralong cycling life in a sodium ion battery. At a charging rate of 1 C, BI-NVP delivers 97% of its theoretical capacity and is able to retain a voltage plateau even at the ultra-high rate of 200 C. It also shows long cycling life with capacity retention of 91% after 10 000 cycles at 50 C. The sodium ion battery cells with a BI-NVP cathode and Na metal anode were able to deliver a maximum specific energy of 350 W h kg−1 and maximum specific power of 154 kW kg−1. In situ and postmortem analyses of cycled BI-NVP (including by Raman and XRD spectra) HRTEM, and STEM-EELS, indicate highly reversible dilation–contraction, negligible electrode pulverization, and a stable NVP-reduced graphene oxide layer interface. The results presented here provide a rational and biomimetic material design for the electrode architecture for ultrahigh power and ultralong cyclability of the sodium ion battery full cells when paired with a sodium metal anode.

Sodium ion hybrid capacitor (SIHC) has much attention because of abundance of sodium source and low cost. To improve the performance of SIHC stability, the poly-Acrylic Acid (PAA) cross-linked with Vinyl Silica Nano Particle (VSNP) was used as gel electrolyte. The VSNP was used as cross-linker and synthesized by Sol-Gel method with Vinyltriethoxysilane (VTES) to improve the mechanical strength of gel. Fourier-Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscope (SEM) was used to analyze C=C bond and morphology of VSNP. PAA gel was polymerized by radical polymerizaiotn with VSNP cross-linker. To measure electrochemical property, SIHC was fabricated with Na3V2(PO4)3 (NVP) cathode material and Activated Carbon (YP50F) anode material. Electrochemical Impedance Spectroscopy (EIS) was used to analyze interfaces-contact with electrode and electrolyte. After measure electrochemical property, X-ray Diffraction was measured to characterize the NVP crystallinity. By this research, It can propose the way how apply to flexible sodium ion hybrid capacitor and gel electrolyte SIHC

Due to high ionic conductivity of Na3V2(PO4)3 (NVP), stable three-dimensional structure and high theoretical capacity, NVP is attracting much attention as cathode material of Na-ion system. However, NVP has poor electronic conductivity which causes poor rate capability and cycle stability. The aim of this research is to further improve electronic conductivity and structural stability, thereby improving the rate capability and cycle stability. rGO has the characteristics of excellent electronic conductivity, large surface area, which make rGO a suitable material for the conductive network. Electrochemical tests show that NVP/rGO composites has much more excellent cycle stability and rate capability than pristine NVP. The results show that NVP/rGO can be considered as a candidate for cathode materials with high rate capability and stability in sodium ion storage systems and that forming a composite with rGO can improve rate & cycle performance of electrode materials.

Among vanadium-based materials, VO2(B), sharing octahedral VO6 structure with cavities, are considered as cathode materials due to their high capacity and multiple oxidation state. However, it has its own limitations such as low cyclic stability and sluggish charge storage kinetics arising from large structural deformation and poor electrical conductivity. In order to resolve these problems, we report a microsphere of thread like structured VO2(B) consisting of interconnected particles each other, providing continuous and facile electron and ion transport pathway. The robust internetworked microspherical structure leads to prevent the drastic volume variation during Li insertion/de-insertion process. More specifically, the as-synthesized VO2(B) displays high capacity of 225.6 mAh g−1 at 50 mA g−1 with a Columbic efficiency of 98%, high rate retention of 70% at 300 mA g−1, and good cycle stability of 72% after 350 cycles at 300 mA g−1. In addition, their structural and phase reversibility are confirmed by the in-situ XRD of VO2(B), where position of crystalline (002) peak after several electrochemical processes nearly returns on the origin position during Li insertion/de-insertion.

Two-dimensional (2D) transition metal carbides (MXenes) have been considered a promising electrode material in energy storage devices due to their outstanding electrical conductivity, excellent electrochemical performance and unique surface terminations. Herein, with inspiration from the interesting functional structure of layered MXene, we report an efficient and facile sonochemical method to synthesize an anode material; functionally activated titanium carbide nanorods grown on Ti3C2 MXene nanosheets (FTCN-MXene) in deionized water and dimethylformamide mixture. In a striking contrast to pristine Ti3C2Tx MXene, FTCN-MXene exhibits outstanding specific anode capacity of 1,034 mAh/g, high coulombic efficiency (98.78%) after 250 cycles, and excellent reversible cyclic stability (retention of 96.05%). Functionalized nanorods grown on metallic conducting Ti3C2 sheets create more active sites and surface area, improving Li ion insertion/extraction capability. This study opens new avenues for developing functionalized MXene-based electrode materials with enhanced performance for electrochemical energy storage devices and systems.

Vanadium pentoxide is considered as a candidate of cathode material for lithium-ion batteries owing to its high specific capacity, large potential window, and short diffusion pathway. However, vanadium pentoxide has its own limitations such as insufficient electronic conductivity, sluggish ion diffusion, and volume expansion. In order to resolve these problems, we demonstrate spray frozen assembly into hierarchically structured open-porous vanadium pentoxide/reduced graphene oxide composite microballs for high performance lithium-ion battery cathodes. The uniform distribution of vanadium pentoxide particles immobilized onto the open-porous surface of reduced graphene oxide microballs is associated with the short ion diffusion pathway, the percolated electronic conduction, and the buffering space. Accordingly, vanadium pentoxide/reduced graphene oxide composite microballs achieve the initial discharge capacity of 273 mAh g−1 at 100 mA g−1 which is higher than those of reduced graphene oxide (78 mAh g−1) and vanadium pentoxide (214 mAh g−1). When the current density increases from 100 to 1000 mA g−1, the capacity retention of vanadium pentoxide/reduced graphene oxide composite microballs is 51.3%, much greater than 36.4% of vanadium pentoxide particles. The capacity retention of 80.4% with the Coulombic efficiency of 97.1% over 200 cycles is twice greater than that of V2O5 particles, indicating improved cyclic stability.

Electrochemical sodium storage and capture are considered an attractive technology owing to the natural abundance, low cost, safety, and cleanness of sodium, and the higher efficiency of the electrochemical system compared to fossil-fuel-based counterparts. Considering that the sodium-ion chemistry often largely deviates from the lithium-based one despite the physical and chemical similarities, the architecture and chemical structure of electrode materials should be designed for highly efficient sodium storage and capture technologies. Here, the rational design in the structure and chemistry of carbon materials for sodium-ion batteries (SIBs), sodium-ion capacitors (SICs), and capacitive deionization (CDI) applications is comprehensively reviewed. Types and features of carbon materials are classified into ordered and disordered carbons as well as nanodimensional and nanoporous carbons, covering the effect of synthesis parameters on the carbon structure and chemistry. The sodium storage mechanism and performance of these carbon materials are correlated with the key structural/chemical factors, including the interlayer spacing, crystallite size, porous characteristics, micro/nanostructure, morphology, surface chemistry, heteroatom incorporation, and hybridization. Finally, perspectives on current impediment and future research directions into the development of practical SIBs, SICs, and CDI are also provided.

This study was carried out for the purpose of obtaining basic data to utilize the AMD sludge as sorbent for heavy metal ions.The sludge from the treatment process of Acid Mine Drainage mainly consists of fine iron hydroxide or iron oxide hydrate andcalcite, and the fine iron hydroxide or iron oxide hydrate has a property of adsorbing heavy metal ions. In this study, we inves-tigated the physical property of the AMD sludge like as mineral composition, particle size and shape and chemical compositionand also investigated the influence of dosage of sludge, adsorbing time, pH, initial concentration and sintering temperature onthe adsorption of heavy metal ions.key worlds : AMD, sluge, utilize, heavy metal, sorbent 1. 서론 2006년 한국광해방지공단에서 수행한 조사에 의하면우리나라에서는 150여개의 폐탄광으로부터 매일 10만톤 이상의 산성광산배수가 발생하고 있으며 이들의 환경에 미치는 악영향을 최소화하기 위하여 이들을 처리하기 위한 시설물의 1)설치를 계획하고 있다. 산성광산배수의 처리를 위하여 고려되고 있는 기술들은 2)소석회 중화법, 전기정화법, SAPS(SuccessiveAlkalinity Producing System)등이 있으며 이들은 모두철수산화물(또는 철산화물의 수화물)을 주로 하는 슬러지를 발생시키는 공통점을 갖는다. 이들 슬러지는 지금까지는 매립시설에서 매립처리하거나 시멘트 부원료로만 활용되고 있으나 발생 슬러지를 보다 고부가가치의 용도로 재활용하고자 하는 연구들이 3-7)진행되고 있다.본 연구에서는 소석회 중화법을 사용하는 함태탄광