Cobalt-iron oxides have attracted much attention as electrode materials for supercapacitors. Graphene loaded with cobalt ferrite (CoFe2O4) nanoparticles can exhibit enhanced specific capacitance. Here, we present three-dimensional (3D) crumpled graphene (CGR) loaded with CoFe2O4 nanoparticles. The CoFe2O4-graphene composites were synthesized from a colloidal mixture of GO, FeCl3•6H2O, and CoCl2•6H2O by one step aerosol spray pyrolysis. The CoFe2O4-GR composites displayed a morphology resembling a crumpled paper ball, and the size of the CoFe2O4 and CGR in the composites was around 5 nm and 500 nm, respectively. The highest specific capacitance of the CoFe2O4-graphene composites was 253 F g–1.

A multiwall carbon nanotube/graphene (MWCNT/GR) composite was synthesized for an enhanced supercapacitor. Aerosol spray drying (ASD) was used to synthesize the MWCNT/GR particles using a mixture of graphene oxide (GO) solution and MWCNT. The effect of the MWCNT/GO ratio on the properties of the composite, including its shape and structure, was investigated. The composite particles were generally shaped like a crumpled paper ball, with an average diameter of approximately 5 µm. The MWCNTs, which were uniformly dispersed among the graphene sheets, not only increased the basal spacing of the sheets but also bridged the wide gaps between them, thereby improving electron transfer between the layers. Thus, the MWCNTs increased the contact area of the electrolyte/electrode and facilitated the transportation of electrons and electrolyte in the electrode. Using a two-electrode testing system, the electrochemical results demonstrate that the MWCNT/GR (weight ratio = 0.1) electrode has a capacitance of 192 F g–1 and an excellent rate of capacity retention (88

The conditions for efficient lithium extraction from lepidolite were studied. The experiments indicated that the best molar ratio of Li in lepidolite to Na2SO4 mass ratio during roasting was 1:6. The extraction of Li was >90% after 0.5 h of roasting at 750 degrees C. The extraction of Li was essentially constant when roasted at temperatures over 700 degrees C. With smaller particle sizes of lepidolite (in the range of 100-200 mu m), it is possible to achieve a high efficiency of Li extraction even at a low temperature of 700 degrees C and a short holding time of 30 min. The efficient roasting condition is easily adapted in industrial application.

As the energy transition era begins, securing minerals is becoming critical, and countries worldwide are highly interested in "critical minerals," which have a supply risk associated with them.Major countries have newly prepared or updated the list of critical minerals, where battery minerals such as lithium, nickel, cobalt, and graphite typically find a place.The demand for these four critical minerals is expected to increase 3 to 42 folds by 2040 in comparison to 2020 owing to the increasing demand for eco-friendly vehicles and energy storage systems.Recently, the supply risk of the four minerals has increased significantly, as commercial products manufactured using these minerals are generally produced in a specific country; furthermore, the prices of the minerals are constantly increasing.In this study, the current status of the production, markets, and relevant technologies of the four critical minerals was investigated, and some recommendations for securing them were presented.

Recently, high electrochemical performance anode materials for lithium ion secondary batteries are of interest. Here, we present silicon-carbon-graphene (Si-C-GR) composites for high performance anode materials of lithium ion secondary battery (LIB). Aerosol process and heat-treatment were employed to prepare the Si-C-GR composites using a colloidal mixture of silicon, glucose, and graphene oxide (GO) precursor. Fabrication of the Si-C-GR composites was composed of two stages. The first stage was formation of Si-glucose-GO composites by co-assembly of Si and GO while the sprayed droplets of the colloidal mixture went through the pre-heated aerosol reactor, and the second stage was carbonization of glucose and thermal reduction of GO by heat treatment. Morphology of as-fabricated Si-C-GR composites was generally the shape of a crumpled paper ball and the Si particles were well wrapped in carbon and graphene. The effects of the size of the silicon particles in Si-C-GR composites on the material properties including the morphology and crystal structure were investigated. Silicon particles ranged from 50 nm to 1 µm in average diameter were employed while concentration of silicon, graphene oxide and glucose was fixed in the aerosol precursor. The size range of composites was about from 2.2 to 2.9 µm. The composites including silicon particles larger than 200 nm in size exhibited higher performance as LIB anodes such as capacity and coulombic efficiency than silicon particles less than 100 nm, which were about 1500 mAh g–1 at 100 cycles in capacity and 99

A vanadium electrolyte for energy storage is generally prepared by dissolving vanadium pentoxide (V2O5) in sulfuric acid using oxalic acid ((COOH)(2)) as a reducing agent. However, there is a disadvantage that the dissolution rate in the sulfuric acid solution of V2O5 is very slow. In this study, a new process for producing vanadium dioxide (VO2), which has the faster dissolution rate than V2O5 in sulfuric acid solution, was developed. Vanadium dioxide (VO2) could be used in the production of a vanadium electrolyte for energy storage. The process developed in the study has the advantages of being economical and simple as compared to the existing process for producing VO2 from V2O5 using hydrogen or carbon monoxide as a reducing agent.

본 연구에서는 VRFB용 고순도 오산화바나듐을 제조하기 위한 불순물 분리 정제 공정에서 킬레이트제(EDTA)의 영향을 조사하였다. 저순도 바나듐 원료를 이용하여 제조된 바나듐 용액으로부터 NH4VO3 을 침전 회수하여 제조된 최종 V2O5 분말의 순도는 99.7%로 분석되었지만 NH4VO3 침전 회수 공정에서 킬레이트제를 첨가한 경우 최종 V2O5 분말 순도가 99.9% 이상으로 향상되었다. 이러한 결과는 첨가된 킬레이트제가 불순물 이온과 반응하여 complex를 형성하고 불순물 이온이 안정화되기 때문에 침전 회수 공정에서 바나듐에 대한 선택성이 향상된 것으로 판단된다. 하지만 제조된 V2O5 분말내에는 불순물 규격 대비 K, Mn, Fe, Na 및 Al 함유량이 높아 추가적인 불순물 정제 연구가 필요하였다. 고순도 V2O5 분말을 새롭게 개발된 직접 전해공정에 적용하여 바나듐 전해액을 제조하였고 이의 특성을 상용 전해액과 비교 분석하였다. 제조된 바나듐 전해액의 순도는 불순물 K, Ca, Na, Al, Mg 및 Si 성분의 높은 함량으로 인하여 상용 전해액의 순도 99.98%보다 낮은 99.97%로 분석되었다. 따라서 고순도 V2O5 분말 및 전해액 제조 공정의 불순물 분리 정제에 대한 추가적인 최적화 연구가 수행된다면 상용화가 가능한 공정이 개발될 것으로 기대된다.

본 연구에서는 VRFB의 고순도 바나듐 전해액을 제조하기 위해 저순도 오산화바나듐의 고순도화 공정으로 가수분해 침전 공정을 적용하였다. 상용 바나듐 전해액 순도 분석을 통하여 검토한 VRFB용 바나듐 전해액 및 오산화바나듐의 최저 순도는 각각 99.98% 및 99.8%로 확인되었다. 초기 순도가 99.7% 및 98.3%인 오산화바나듐에 가수분해 침전 공정을 적용할 경우 99.8% 이상의 고순도 오산화바나듐이 제조되었지만 Fe, Ga 성분이 불순물로 함유되었다. 추가적인 순도 향상을 위해 red cake 침전 단계를 포함하는 2단계 공정을 적용하였으나 바나듐 회수율이 감소하는 단점이 확인되었다. 따라서 향후 단일 공정으로 구성되어 높은 바나듐 회수율을 얻을 수 있는 고순도 바나듐 정제 공정 개발이 필요하다.

본 연구에서는 오산화바나듐(V2O5)로부터 불순물을 제거하기 위한 건식정제 공정법 중의 하나인 휘발정제 방법에 대한 기초연구를 수행하였다. 열역학적 분석결과 오산화바나듐에 함유된 P2O5 불순물은 300°C 이상에서 NaOH와 KOH 같은 불순물은 600°C 이상에서 증기압이 높아 기상으로 휘발 제거가 가능할 것으로 분석되었다. 실험은 대기 분위기와 감압 분위기에서 휘발온도 600 – 1000°C, 유지시간 15 – 60분으로 변화시키면서 수행되었다. 감압은 아르곤 분위기에서 7.9×10-2 – 1.1×10-1 기압으로 조절하였다. 열역학적 분석결과와 실험 결과를 비교함으로써 SO3, P2O5, NaOH, KOH 같은 불순물이 로내 압력 조건에 상관없이 효과적으로 오산화바나듐으로부터 제거된다는 것이 확인되었다. 최적 조건에서 99.6 wt% 순도를 갖는 오산화바나듐이 99.2 wt% 순도를 갖는 오산화바나듐으로부터 제조되었다.

Recently, there is a growing concern for high performance energy storage devices in many applications where a lot of energy needs to be either stored or delivered. Here, we introduce a facile strategy to fabricate effectively combined 3D structured composites of crumpled graphene (CGR), polyaniline (PANI) and molybdenum disulfide (MoS2) for potential application to high performance alkali metal ion storage such as sodium and lithium ion storage. 2D graphene oxides, polyaniline, and physically exfoliated 2D MoS2 were combined to fabricate 3D structured CGR/PANI/MoS2 composites by aerosol self-assembly process and post heat treatment. Overall morphology of composites looked like crumpled paper ball with an average diameter of similar to 5 mu m. MoS2 and PANI were attached on the surface of the graphene, which supported an accessible surface area and provided a path for electron transfer. Synergistic effect by the combination of the three functional materials resulted in outstanding electrochemical performance as sodium-ion storage in terms of storage capacity (328 F g(-1) at 1 A g(-1)), good rate capability (282 F g(-1) at 10 A g(-1)), and cycle performance (95%, after 1000 cycles). Even lithium-ion storage application, the CGR/PANI/MoS2 also delivered a high specific capacity of 470 mAh g(-1) after 100 cycles. (c) 2021 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

The surface and internal deoxidation behavior of hydrogenation-dehydrogenation titanium alloy powder deoxidized by Ca vapor was investigated. Comparison of the deoxidation behavior of solid solution and intermetallic alloys was performed by calculating the surface and internal oxygen concentrations. The surface O concentration of the Ti alloy powders depended on the specific surface area and the thickness of the surface oxide layer. The removed surface O concentration of the solid solution alloy increased significantly with decreasing particle size. However, the removed surface O concentration of the intermetallic alloy increased slightly as the particle size decreased. The difference in the deoxidation behavior of the surface O of the solid solution alloy and the intermetallic compound alloy occurred owing to the difference in the tendency of the specific surface area to increase with the particle size and the thickness of the reduced surface oxide layer. The internal O concentration of the Ti alloy powder was uniformly reduced regardless of the particle size, and a larger amount of O was removed from the inside of the particles than from the surface.

최근 미세플라스틱의 발생 측면에서 폐플라스틱의 친환경적 처리에 대한 관심이 증대하고 있다. 이에, 폐플라스틱의 재활용이 폐기물 간소화, 이산화탄소 배출 감소 및 부가가치 제품 재생산의 이점을 제공하기 때문에 매우 중요하다고 할 수 있다. 특히, 친환경적인 폐플라스틱의 재활용을 위해서는 물리적 선별방법을 통해야 하며, 그 중에서도 폐플라스틱내의 재질별 분리가 가능한 부유선별이 물질재활용 측면에서 매우 효과적인 분리방법으로 잘 알려져 있다. 따라서, 본 총설에서는 혼합 폐플라스틱의 효과적인 재질 분리를 하기 위한 부유선별의 연구 동향을 조사하였다. 추가적으로 보고된 연구결과들을 통하여 플라스틱의 원재료인 폴리머로부터 기능성 신소재로서의 활용에 대한 접근방법을 요약 정리하였다.

The aluminothermic process is used for producing ferrotitanium alloy (FeTi) from an ilmenite concentrate. In this study, based on thermodynamic calculations and experiments, we investigated the effects of adding varying amounts of exothermal agent (NaClO3), slag-forming agent (CaO), and reducing agent (Al) on the recovery ratio of Ti in the aluminothermic process. The thermodynamic calculations suggested that the exothermal agent plays a crucial role in producing the FeTi alloy from the ilmenite concentrate and the maximum Ti grade in the FeTi alloy was approximately 30 wt %. Experimentally, it was verified that the FeTi alloy obtained under the optimum mixing conditions contained 30.2–30.8 wt % Ti, 1.1–1.3 wt % Si, 9.5–11.2 wt % Al, and 56.9–58.0 wt % Fe, along with trace impurities and small amounts of gases such as oxygen (0.35–0.66 wt %) and nitrogen (0.01–0.02 wt %). At the optimum mixing conditions, the recovery ratio of Ti into the obtained FeTi alloy phase was 60.6–68.9%. These results matched closely with the thermodynamic calculations. Therefore, the thermodynamic calculations performed herein are expected to significantly contribute toward the development of new processes and improvement in conventional processes for producing various ferroalloys including the FeTi alloy through the aluminothermic process.

Recently, many researchers have developed advanced energy storage and energy conversion systems to address the increased demand for energy resources. The performance of these electrochemical energy storage and conversion devices depends considerably on the properties of their unique electrode materials. Among electrode materials, graphene (GR) has attracted much attention due to its unique properties of high flexibility, a large specific surface area, and superior electric conductivity rates that are well-suited to energy storage systems. Specifically, aerosol-made 3D GR composites are known to be more resistant to compressive forces such as paper balls owing to their stronger and harder compressive tolerance levels and higher and more stable surface areas compared to 2D GR sheets. These unique properties of 3D GR composites result in enhanced electrochemical performances for energy storage systems. This review focuses on recent studies of aerosol-made 3D GR-based composites for energy storage systems such as supercapacitors, lithium-ion batteries, and sodium-ion batteries.

In recent years, supercapacitors have received considerable research attention for energy storage systems due to their high-power density, fast charge-discharge processes, and long cycle life. The superior performance of supercapacitors is considerably dependent on the electrode materials. Among electrode materials, graphene balls (GBs) and their composites have recently attracted strong interest. They are considered ideal for the fabrication of electrode materials because of their unique characteristics of large specific surface area and superior electric conductivity, which should make them very effective for use in supercapacitors. In particular, GBs and their microstructured composites have recently been proven promising candidates for supercapacitor electrodes. Their unique 3D morphology provides highly porous graphene structures for decoration with active materials. In this perspective, recent studies were highlighted and discussed that focus on GBs and their composites for the potential energy storage devices called supercapacitors, (i.e., electric double layer capacitors and pseudocapacitors). (C) 2019 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

Graphene (GR) has excellent physical and chemical properties, making it promising for application in supercapacitors. In this study, we report the synthesis of spherical GR (SGR) composed of tens of GR sheets and its application in supercapacitors. Graphene oxide (GO) was first reduced in the liquid phase by using L-ascorbic acid (L-AA), an environmentally friendly reducing agent, and then SGR was prepared using the reduced GO colloid by aerosol spray drying. The reduction of GO in the liquid phase was completed in 1 h. The SGR fabricated by the aerosol process ranged from 2 to 4 mu m in diameter. The as-prepared SGR fabricated from GO at pH 2 showed a densely packed spherical morphology and porous structure with a specific surface area of 150 m(2)/g. The SGR fabricated from the GO colloid at pH 10 showed an improved specific surface area (216 m(2)/g) and a higher specific capacitance (182 F/g) than the SGR fabricated at pH 2. Considering the environmentally friendly process, the as-prepared SGR is a highly promising material for supercapacitors. (C) 2018 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan.

Nanostructured graphene electrodes generally have a low density, which can limit the volumetric performance for energy storage devices. The liquid-phase mild reduction process of graphene oxide sheets is combined with the continuous aerosol densification process to produce high-density graphene agglomerates in the form of microspheres. The produced graphene assembly shows the cabbage-like morphology with a high density of 0.75 g cm-3 . In spite of such high density, the cabbage-like graphene microspheres have narrow-ranged mesopores and a high surface area. The cabbage-like graphene microsphere exhibits both high gravimetric and volumetric energy densities due to the optimized microstructure, which shows a high gravimetric capacitance of 177 F g-1 and volumetric capacitance of 117 F cm-3 in supercapacitors. As a cathode for lithium-ion capacitors, the cabbage-like graphene delivers a reversible capacity of ≈176 mAh g-1 . The stacking-control approach provides a new pathway to control the microstructure of the graphene assembly and corresponding charge storage characteristics for energy storage applications.

Silicon (Si) particles are considered as promising anode electrode materials in lithium ion batteries (LIBs) because of high theoretical energy capacity of 3579 mA h/g. However, the large volume expansion of Si during the cycling process cause structural degradation and pulverization of the electrode, and this leads to solid electrolyte interphase (SEI) film reformation. In order to solve the problem, wrapping of Si particles with carbon materials is considered as an effective solution. In this study, we report ternary silicon core-carbon nanotubes winding-graphene shell (Si-CNTs-GR) nano-structured composites, which can cushion volume change of Si core particles by carbon nanotubes (CNTs) winding and protect SEI layer by graphene (GR) shell. The composites were fabricated using a facile aerosol process followed by heat-treament for anode materials of LIBs. The average particle size of ternary Si-CNTs-GR increased with respect to concentrations of CNTs at fixed other conditions. The as-prepared composites exhibited higher performance as LIB anodes such as capacity and coulombic efficiency than commercial Si particles or SiGR composites. The ternary Si-CNTs-GR composites showed high capacity of 1700 mA h/g at 50 cycles. (C) 2018 Elsevier B.V. All rights reserved.

Asymmetric supercapacitors are considered promising energy storage devices due to their high applied voltage and corresponding high energy density. Herein, Fe-Co binary oxides nanoparticles loaded crumpled graphene (CGR) composites were prepared for use as the positive electrode material of asymmetric supercapacitors (ASC) using aerosol spray pyrolysis and post heat-treatment processes. The composites showed a crumpled paper like morphology and were around 1 mu m in average diameter. Asymmetric electrode structures were fabricated using the composites as the positive electrode and CGR as the negative electrode. Electrochemical measurement of the ASC indicated excellent capacitive performance, which resulted in high energy density (36 W h kg (1)) and long-term cycling stability after 2000 cycles at a current density of 1 A g(-1). (C) 2018 Elsevier B.V. All rights reserved.

Silicon has attracted extensive attention due to its high theoretical capacity, low discharge potential and non-toxicity as anode material for lithium ion batteries. In this study, Si-CNT-C composites were fabricated for use as a high-efficiency anode material in a lithium ion battery. Aerosol self-assembly and post-heat treatment processes were employed to fabricate the composites. The morphology of the Si-CNT-C composites was spherical and an average particle size was 2.72 mu m. The size of the composite increased as concentration of Si and CNT increased in the precursor solution. In the Si-CNT-C composites, CNT and C carbonized from glucose were attached to the surface of Si particles. Electrochemical measurement showed that the cycle performance of Si-CNT-C composites was better than that of silicon particles.