ABSTRACT Natural graphite is classified as a strategic critical raw material by the European Union due to its strategic significance. The demand is steadily increasing, but the current purification methods are not environmentally sustainable, highlighting the need for greener alternatives. This study investigates the effects – sulfuric acid (H2SO4) leaching, thermal treatment, and their combination – on natural graphite from a flotation pilot plant. In the sulfuric acid leaching, the influences of reaction time (60–300 min), temperature (70–100°C), sulfuric acid concentration (0.5–3 mol/L), and liquid-to-solid ratio (10–20 mL/g) were systematically studied using experimental design. Leaching effectively removed 91.4% iron and 52.9% aluminum, but was ineffective against silicon-containing phases. A short 15 min thermal treatment at 2400°C in an argon atmosphere using induction annealing eliminated most silicon phases and other impurities, although residual 2.65 mg/g iron and 1.27 mg/g silicon remained. The combined approach reduced iron and silicon contents to 0.24 and 0.25 mg/g, respectively, and increased the carbon content from 78.4 to 97.6 wt% to near commercial battery-grade levels (98.0 wt%). Additionally, the combination-treated graphite exhibited the lowest degree of structural defects, offering a more sustainable route for purifying natural graphite to high-purity levels compared to conventional halogen-containing techniques.

Abstract Graphite, primarily composed of carbon, is a valuable industrial material renowned for its exceptional thermal conductivity, high melting point, and resistance to thermal shock and corrosion. It exists in two forms: natural graphite, a mineral, and synthetic graphite, produced from coal and oil. As the costs of these materials rise and their industrial uses expand, researchers are exploring sustainable ways to produce graphite. This study assessed the possibility of making graphite from poplar wood, waste tires, and wheat straw through pyrolysis at temperatures from 500 to 800°C. Results showed that higher temperatures resulted in lower bio‐char yields, with the best efficiency at 500°C due to increased bio‐char breakdown. Elemental analysis revealed that the carbon content increased while the levels of hydrogen, nitrogen, and oxygen decreased as the temperature rose. FT‐IR analysis detected both aromatic and aliphatic compounds, with a higher ratio of aromatics at higher temperatures, indicating dehydrogenation. The specific surface area of bio‐char samples was highest at increased pyrolysis temperatures and varied among the materials. XRD analysis confirmed that the crystalline structure of graphite improved with rising temperature, while SEM images showed better porosity and surface area. TGA analysis revealed that all samples experienced less weight loss and greater thermal stability at higher temperatures.

Generation of endohedral metallofullerene ions of Ca1-4C2n+ (44 ≤ 2n ≤ 132) by laser ablation of natural graphite sheets without pretreatment

The extraction of titanium (Ti) from ilmenite (FeTiO₃) using carboiodination offers a potential method for selective and environmental green processing, especially when employing renewable carbon sources. This study examines the reduction behaviour and kinetics of ilmenite using carboiodination, with graphite and palm-based char serving as the carbonaceous reductants. The experimental procedure was conducted in a vertical tube furnace maintained at 1000 °C under an inert argon atmosphere to ensure controlled reaction conditions. The reaction kinetic analysis was calculated based on first-order kinetic reduction from the gas produced [ carbon monoxide (CO) and carbon dioxide (CO2)] during the reduction process by the gas analyser, while Scanning Electron Microscopy/ Energy-Dispersive X-ray Spectroscopy (SEM/ EDS) analysed the reduction mechanism. Palm char (PC-I) obtained the greatest reaction rate constant (0.002298 moles/s) and yielded 35.7 mass% Ti at 1000 °C, contrary to graphite (G-I), which produced 27.6 mass% Ti. The carboiodination reaction involves the formation of volatile titanium tetraiodide (TiI₄) via the reaction of titanium dioxide (TiO₂) with carbon (C) and iodine (I₂). PC-I’s enhanced performance compared to G-I is attributed to its high surface area, porosity, and catalytic mineral content, which facilitate redox reactions and lower activation energy. The findings indicate palm char’s promise as a sustainable alternative to fossil-based reductants in ilmenite reduction.

In order to examinethe impact of phenolic vinyl resin contentson the performance of composite bipolar plates (BPs), we manufactureda sample of graphite composite BPs for proton exchange membrane fuelcells (PEMFCs) utilizing phenolic vinyl resin as a binding agent byusing a hot press molding procedure. Composite BPs were mixed by dryball milling, with natural graphite and expanded graphite (EG) asconductive fillers and carbon fiber and graphene as additives. Theresults showed that the composite BP with different resin contentshad good hydrophobicity and thermal stability, which met the operatingtemperature conditions of fuel cells. An elevation in the phenolicvinyl resin content resulted in a decreased conductivity of the graphitecomposite BP material, increased contact resistance, and enhancedflexural strength. When the content of phenolic vinyl resin reached38%, composite BPs showed the best overall performance. The resinwas most uniformly distributed in the BP, and the conductivity wasabove 100 S/cm and the flexural strength was greater than 40 MPa,which meet the U.S. Department of Energy (DOE) indicators.

The article presents a method of measurement and a test stand for determining the specific electrical resistivity of granular carburizing materials most commonly used in foundry practice. The research was conducted for synthetic graphites (GS) and petroleum cokes (KN) using a test stand proposed by the authors of the study and protected by a patent. It was shown that this measurement method allows for a clear distinction between the tested materials. For synthetic graphites, specific resistivities in the range of 35.9–144.5 μΩ·m were obtained, while for petroleum cokes the range was 172.1–1390 μΩ·m. The main aim of the study was to determine whether there is a correlation between the measured electrical resistivity of the tested materials and the carburization efficiency obtained in melting experiments. Therefore, the article also presents the course and results of studies on the process of cast iron melting in laboratory induction furnaces, where the carburizing material was introduced into the induction furnace with a fixed charge. Carburization efficiencies obtained for synthetic graphite ranged from 86.6% to 94.4%, and from 65.5% to 85.31% for petroleum coke. Based on the measurement results, a statistical analysis was carried out, yielding a relationship with a coefficient of determination R2 = 0.92. The research confirmed the possibility of a quick assessment of carburizers in terms of their assimilation degree by molten metal. This is valuable information both for scientific research and industrial applications. The presented results form part of ongoing studies aimed at explaining the differences occurring within a given group of materials (petroleum cokes and synthetic graphites).

Increasing the yields of natural flake graphite spheronization with the NARA Hybridization System

Natural flake graphite as an affordable dosimeter for clinical X ray application at dose ranges between 2-20 mGy

Synergistic effect of dual-enzyme-induced carbonate precipitation and modified plant fibers on the bio-cementation of graphite tailings.

Supercritical CO2-assisted pressure homogenization for exfoliating natural graphite toward high-performance graphene cathodes in aluminum-ion batteries

ABSTRACT For decades, the industry has believed that spherical graphite (SG) yield correlates strongly with graphite flake size. To clarify natural graphite (NG) spheroidization mechanisms, a comprehensive evaluation was conducted by extracting intermediate products from an industrial production line and utilizing separated jet mills to simulate continuous processing in the study. Focused ion beam‐scanning electron microscope (FIB‐SEM) cross‐sectional analysis and nanocomputed tomography (Nano‐CT) imaging revealed that flakes of different thicknesses underwent distinct morphological changes (folding, bending, or fragmentation) under mechanical force, with only flakes above a critical thickness (∼2 μm) forming SG cores. Statistical correlation between thickness (measured via statistical method under SEM) and yield demonstrated that thickness—not only size—is the dominant factor, redefining “effective SG flakes” to include small but thick flakes. Therefore, prioritizing thickness protection over size preservation in grinding‐flotation and spheroidization processes increased SG yield by 7% in industrial validation. The work provides new insights for high‐efficiency SG production.

Graphite is used as an anode material in nearly all commercial Li-ion Batteries (LIBs). To increase energy density, Si and Sn-based materials (including SiOx) are intensively being investigated as anode materials. If used to their full theoretical extent, they could increase LIB energy density by as much as 20%.1 However, the widespread application of these elements is impeded due to their large volume change and unstable solid electrolyte interphase (SEI) formation that leads to capacity fade. A variety of design approaches have been taken to make alloy anodes compatible with commercial cells.2-4 However, in most cases, the preparation procedures are complex, give low yields, and require expensive chemicals, making their large-scale production prohibitively expensive.Recently, we have shown that mechanofusion can be used to embed natural graphite (NG) with Si-nanoparticles (Si-NP).5 In this process, the Si-NPs filled voids in the NG that had connections to the NG particle surface. The resulting Si-NP/NG composite particles had increased capacity and capacity retention even when no electrolyte additives were used. These results were highly promising. However, many unknowns remain, including: how the composite morphology and microstructure depend on the mechanofusion conditions, how many NPs can be inserted into NG, and how this process depends on the NP size.In this study, TiO2-NPs (rutile phase) were used as model guest particles to make TiO2-NP/NG composites and study the embedding process of NP into graphite. TiO2 was selected for this study, since it is available in NPs of many different sizes and it has low electrochemical activity, allowing the electrochemistry of the NG to be studied after the embedding process.Fig. 1(a) and 1(b) show cross-section SEM images of NG embedded with 100 nm and 300 nm TiO2-NPs, respectively. It was found that mechanofusion conditions and NP size have a profound effect on the final composite morphology and microstructure. Importantly, the host graphite was found to retain high crystallinity under mechanofusion conditions that induce TiO2 guest particle embedding, resulting also in good electrochemical performance of the host graphite. Moreover, the NP size was found to determine the porosity in the loading of the composites, with smaller NP size leading to increased NP loading and reduced internal porosity.These results demonstrate design strategies to NP/NG composite particles that can lead to new high energy density anode materials. Moreover, the dry processing method is cheap, scalable, and does not produce waste. Acknowledgements The authors acknowledge funding from NSERC and NOVONIX Battery Technology Solutions under the auspices of the NSERC Alliance grants program.

Lithium-ion batteries (LIBs) have become a cornerstone of modern energy storage, powering everything from smartphones and laptops to electric vehicles (EVs) and renewable battery energy storage systems (BESS). Their widespread use is attributed to their high energy density, long cycle life as well as fast charge capabilities. The demand for LIBs is projected to increase significantly in the coming years, rising from about 150 GWh in 2020 to more than 3000 GWh in 2030 [1] mainly driven by electric mobility in the form of EVs. As a consequence of this growing demand and due to the limited lifespan of LIBs (5-8 years), the amount of spent batteries is also expected to rise from 150 kt in 2020 to about 4000 kt in 2030 [2].In this context, recycling of spent LIBs must be considered for both economic and environmental perspectives since it plays a crucial role in reducing greenhouse gas emissions and energy consumption, and in establishing a circular battery supply chain. Currently, the most established industrial-scale recycling methods are hydrometallurgy and pyrometallurgy, primarily targeting the recovery of valuable metals like cobalt and nickel from cathode active materials. However, progress in efficient recycling of graphite anodes from spent LIBs remains slower compared to cathode recycling.Alongside the recycling of LIBs, recent research efforts have been focused on designing battery materials from sustainable sources, with low critical raw material (CRM) content and improved recyclability (e.g., biomass-derived carbon), with the aim to further enhance the sustainability of LIBs.The graphite anode material typically makes up about 25 wt.% of the composition in various cells configurations, contributing to about 10% of the cell’s cost, estimated at around 10 $/kWh [3]. Additionally, even though in smaller amounts, graphite is also commonly used as a conductive additive in cathode electrodes further contributing to the cost of the LIBs. Graphite in LIBs can be either natural or synthetic and each type has its drawbacks. Natural graphite is classified as a critical raw material (CRM) and must be mined from mineral deposits, while synthetic graphite is produced from petroleum coke through an energy-intensive process, resulting in higher energy consumption and higher CO₂ emissions compared to natural graphite. Consequently, advanced technological solutions are needed to improve the sustainability of graphite.In our work, we propose and investigate two sustainable approaches for obtaining graphite: (i) direct recycling of graphite from spent LIBs, and (ii) production of graphite from biochar. Both processes have been developed at a pilot scale and are capable of producing tens to hundreds of kilograms of graphite per lot. In the first method, the recycled graphite is suitable for direct use as an anode material, whereas in the second method, its physical properties make it ideal as a conductive additive for cathode electrodes.For the direct recycling method, end-of-life cells were first discharged and mechanically disassembled. The graphite was then liberated from the Cu current collector with a recovery rate > 99%. Subsequently, the graphite underwent a thermal purification step and a re-spheroidization step, achieving battery-grade purity of greater than 99.95 wt.%C. Electrochemical tests confirmed the successful regeneration of the graphite, which delivered a specific capacity of 350 mAh/g and maintained a cycling stability of > 99% over 300 cycles.In the second approach, biochar served as the starting material to produce graphite as a conductive additive. This biochar—a by-product from the pyrolysis of biomass (e.g., wood)—initially contained about 86-91 wt.% carbon. The biochar underwent a series of processing steps including continuous hammer milling circuit to reduce granule dimension, air milling to further reduce particle size, calcination to remove moisture and volatile species, graphitization to form the graphite structure and at the same time reduce the particle size and surface area. The process successfully produced graphite with a purity >99.99%, a d90 < 6µm and a surface area of around 20 m2/g. The graphite was tested as a conductive additive in both NMP and water-based NMC811 electrodes and the performance compared with electrodes incorporating only standard Super C45 conductive additive. The NMC811 electrodes containing biochar—derived graphite showed similar electrochemical performance to the baseline with an initial capacity of 190 mAh/g and a capacity retention of 95% after 100 cycles in half cells vs Li metal.[1] S. Annegret et al., “Alternative Battery Technologies Roadmap 2030 + ” Fraunhofer ISI, no. September, 2023.[2] Y. Qiao et al., “EcoMat, vol. 5, no. 4, pp. 1–27, 2023[3] M. Greenwood, et al. J. Power Sources Adv., vol. 9, no. March, p. 100055, 2021

Sulfide-based all-solid-state batteries (ASSBs) are regarded as promising next-generation energy storage systems due to their high energy density and improved safety. To enhance the cycling stability of ASSBs, the selection of suitable anode materials is critical. Among various candidates, graphite widely used in conventional lithium-ion batteries is considered a strong contender due to its structural integrity and favorable electrochemical performance. Graphite can be classified into artificial graphite and natural graphite, each exhibiting distinct mechanical and electrochemical characteristics stemming from their different fabrication methods. However, research on the applicability of graphite in sulfide-based ASSBs remains limited. In this study, we systematically investigated the mechanical and electrochemical properties of composite anodes prepared with different types of graphite. These composite anodes were integrated into full all-solid-state lithium-ion batteries (graphite/LiNixCoyMn1-x-yO₂), and their electrochemical performance was comparatively evaluated. The results offer insights into the impact of graphite type on the performance and cycling stability of sulfide-based ASSBs, and the optimal graphite selection strategy is discussed.

Abstract Relying on lithium-ion batteries may impede the faster adoption of alternative energy storage technologies. This study defines foreign direct investment as a foreign investor’s ownership stake in a mining project and examines how it affects diversification and supply risks of critical materials for emerging energy storage. Here we propose the supply risk index and maps global production of natural graphite, manganese, sulfur, molybdenum, and vanadium across 205 regions/territories globally. Results reveal that among material production in 2020, foreign direct investment controlled 31.3% of manganese, 27% of natural graphite, 29% of molybdenum, 27.3% of vanadium, and 14% of sulfur. The proposed index treats foreign direct investment-controlled production as investors’ domestic production and reveals that increasing foreign direct investment reduces supply risks. The findings highlight the importance of diversifying material production via foreign direct investment to reduce dependency on a few dominant countries and strengthen supply chains of critical materials.

All-solid-state batteries are attracting attention as next-generation energy storage systems due to their high energy density and safety; however, the limited capacity of conventional graphite anodes and interfacial instability with solid electrolytes hinder commercialization. Si offers a promising alternative with its high theoretical capacity (3,579 mAh g⁻¹) and appropriate operating voltage, but its extreme volume change (~300%) poses significant challenges. In all-solid-state batteries, Si/Gr composite anodes face three distinct challenges compared to liquid electrolyte systems: (1) the impact of Si volume expansion on Gr crystal structure, (2) Si/SSE interfacial stability, and (3) limited ion transport capabilities of solid electrolytes. This study aims to elucidate the position-specific structural changes and degradation mechanisms of Si/Gr composite anodes to propose new electrode design strategies.Si/Gr composite powders were synthesized by chemical vapor deposition using high-purity SiH4 precursors on spherical natural graphite, while argyrodite-structured sulfide-based solid electrolytes (Li6PS5S(Cl,Br)) were employed. AM+SSE|SSE|Li half-cells were evaluated at 30°C under 50 MPa pressure, with formation cycles conducted at 0.1C for the initial 1-3 cycles, followed by 0.3C for long-term stability assessment. Crystal structure changes were analyzed by μ-XRD, microstructural evolution by SEM/TEM/STEM, and chemical states by EDS/EELS/XPS.The Si/Gr composite anodes achieved 2.4 times higher initial capacity (820 mAh g-1)and superior cycle life (82% retention after 50 cycles) compared to pure Gr anodes. Microstructural analysis revealed that Si volume expansion manifested differently depending on particle position, with structural interactions between particle surface and interior contributing to electrode stability. Notably, surface Si formed stable interfaces with solid electrolytes, while inner Si served as a buffer within the graphite structure. This synergistic effect of position-dependent structural changes demonstrated that high-performance Si/Gr anodes for all-solid-state batteries could be designed without complex nanostructure engineering. This research proposes a new electrode design strategy that considers position-specific characteristics of active materials in all-solid-state battery systems, potentially contributing to the development of next-generation high-capacity all-solid-state batteries.

Onion-like carbon nanostructures (CNO-like structures) exhibit unique structural and morphological features owing to their graphitic layered structure. However, these nanostructures present limited optical activity in the visible region due to their higher degree of sp2hybridization, which results in fast recombination of charge carrier species. This necessitates structural modification of CNO-like structures to impart redshift absorption. Previously, doping of metals and non-metals has been reported for these structural modifications; however, the incorporation of metal oxides and their contribution to optical features have not been yet studied. This study specifically demonstrates the simultaneous synthesis of visible-light-driven TiO2/CNO-like nanostructures via modified flame spray pyrolysis (FSP) and provides insights about their structural and optical features. Transmission electron microscopy results show that CNO-like composites present core-to-shell morphology and TiO2particles are embedded in the carbon layered structures. The inner core of CNO-like structures is associated with organic carbon, while elemental carbon (EC) is responsible for the outer shell, which originates due to high temperature residence time and consequent formation of higher EC4-6fractions in the closed FSP. Thermal optical carbon analysis shows that the core-to-shell ratio is proportionally affected by titania concentration, leading to enhanced defect-induced structures. This is further supported by Raman spectroscopic analysis, which exhibits rise ofID/IGfrom 0.76 to 0.82 for 0.5 wt% to 5 wt% titania, respectively. In the context of Raman spectroscopic analysis,IDstands for the for the intensity of the D-band (disorded band) whileIGrepresents the intensity of the G-band (graphitic band). HigherIDshows that carbon nanostrucrure is more disorded and amorphous in nature while higher value ofIGexhibits the ordered and graphitic nature of the carbon material. These structural defects appear due to sp2disrupted domains and serve as anchoring sites for functional groups such as C=O, C-O, C-H and C=C, as evidenced by Fourier tranform infrared findings. Furthermore, titania induces a synergistic effect and promotes redshift absorption of CNO-like structures, leading to widening of the band gap from 1.55 eV to 2.04 eV. These visible-light-driven CNO-like composites can act as photocatalysts for different photocatalytic and photochemical applications.

Accurate estimation of solid-phase diffusivity in natural graphite using a voltage relaxation technique

A new application of natural rock asphalt in lithium-ion batteries as a novel coating material for natural flake graphite anode

HighlightsAn optimal particle size (approximately 20 μm with a roundness of 0.9 and a specific surface area of 6.6 m2 g−1) yields high lithium intercalation efficiency and robust coulombic efficiency.Excessive fragmentation, which results in the formation of very small particles, compromises the mechanical integrity and reduces specific capacity.A predictive model was developed linking the specific discharge capacity to both the specific surface area and the average nanocrystallite size, yielding an excellent correlation (R2 = 0.997) for spheronized particles.