Graphite In Li-ion Batteries Research Articles

Microfluidic Shape Analysis of Non-spherical Graphite for Li-Ion Batteries via Viscoelastic Particle Focusing.

The size and shape of graphite, which is a popular active anode material for lithium-ion batteries (LIBs), significantly affect the electrochemical performance of LIBs and the rheological properties of the electrode slurries used in battery manufacturing. However, the accurate characterization of its size and shape remains challenging. In this study, the edge plane of graphite in a cross-slot microchannel via viscoelastic particle focusing is characterized. It is reported that the graphite particles are aligned in a direction that shows the edge plane by a planar extensional flow field at the stagnation point of the cross-slot region. Accurate quantification of the edge size and shape for both spheroidized natural and ball-milled graphite is achieved when aligned in this manner. Ball-milled graphite has a smaller circularity and higher aspect ratio than natural graphite, indicating a more plate-like shape. The effects of these differences in graphite shape and size on the rheological properties of the electrode slurry, the structure of the coated electrodes, and electrochemical performance are investigated. This method can contribute to the quality control of graphite for the mass production of LIBs and enhance the electrochemical performance of LIBs.

Li-Ion Battery Material Impedance Analysis II: Graphite and Solid Electrolyte Interphase Kinetics

Li-ion battery graphite electrodes form a solid-electrolyte-interphase (SEI) which is vital in protecting the stability and efficiency of the cell. The SEI properties have been studied extensively in the context of formation and additives, however studying its kinetic features after formation have been neglected. In this study we show the dynamic resistive behavior of the SEI after formation. Via electrochemical impedance spectroscopy measurements on Cu-foil after SEI formation we show how the SEI shows a potential-dependent resistance which can be explained by a change in charge carriers (Li+) in the SEI. Additional measurements on graphite exhibit a similar behavior and allow us to separate the charge transfer kinetics from the SEI resistance, showing that the SEI resistance is the dominating resistance in the graphite kinetics. Measurements on pre-formed electrodes also show how the SEI resistance changes when in contact with electrolyte of different LiPF6 salt concentrations, with the resistance decreasing for increasing salt concentrations. Ultimately, we show that the SEI resistance affects Li-plating by acting as an offset to the plating reaction but does not affect the nucleation overpotential itself.

(Battery Division Student Research Award Sponsored by Mercedes-Benz Research & Development) Quantitative SEI-Based Descriptors for Li metal Liquid Electrolyte Design

Energy density requirements for next-generation batteries make the Li metal anode a key candidate to replace graphite in Li-ion batteries due to Li’s improved capacity (3,860 mAh/g vs. 372 mAh/g). However, Li anodes display lower Coulombic efficiency (CE, <99.9%) than graphite (>99.95%), resulting in faster loss of reversible Li over cycling. This shortfall derives from parasitic Li-electrolyte reactions that lead to accumulation of inactive Li0 and electrolyte-derived byproducts, which result in the formation of a native solid electrolyte interphase (SEI) on Li. Despite the importance of the SEI, its properties and composition are challenging to probe experimentally due to its exceedingly low amount (sub-μmolLi/cm2/cycle at >99% CE). Consequently, the framework on which the understanding of SEI composition and function was built has largely been qualitative, and descriptors to CE have overwhelmingly focused on electrolyte-, as opposed to SEI-based, metrics.To bridge this gap, this collective work focuses on advancing experimental methodologies to precisely quantify (1) functional properties of native SEIs on Li and (2) their chemical composition, both in order to explore their relationships with CE. First, we use a combination of self-consistent measurements involving EIS and CV to measure rates of Li+ exchange across these native interfaces, revealing that this functional property varies across electrolytes, increasing from low to high CE. These experiments further reveal an evolution of Li+ exchange with cycling unique to high-CE electrolytes and that is tightly linked to rate capability. In particular, we find that SEIs of high-CE electrolytes can support Li+ exchange rates in excess of 1 mA/cm2, and increasing to >>10 mA/cm2 after SEI formation and cycling. In order to (2) explore which SEI phases tend to be favored at high CE, we leveraged the quantitative power of analytical tools such as GC, NMR and ICP-AES to measure byproducts of SEI formation. We developed a custom operando GC experiment to measure and chemically-resolve gas evolution in situ during Li cycling. With sub-nmol/min resolution, these revealed, quantitatively, that SEI formation reactions that release CO or CO2, thus leaving behind a decarbonylated/decarboxylated byproduct in the SEI are associated with higher CE. We also expanded our chemical quantification studies to postmortem cells using a titration scheme that was capable of quantifying with ~nAh resolution SEI phases such as ROCO2Li, Li2C2, Li2C2, LiF and P-containing phases, in addition to the inactive Li0 that accumulates on the anode after cycling. In carbonate-based electrolytes, it was found that salt-derived phases (LiF and P) comprised only ~5% of the SEI, with solvent-derived products being the majority of the SEI. Furthermore, it was found that Li2C2, a previously-unmeasured phase on Li, shows a strong anti-correlation with CE. More recently, we further expanded our titration strategy to include other previously-unmeasured phases in leading high-CE electrolytes. Altogether, chemical quantification of the SEI reveals quantitative “SEI fingerprints” that are unique to each electrolyte. Taken together, these quantitative SEI-based descriptors enable a new avenue for electrolyte engineering, informed by a fundamental understanding of the “optimal” Li SEI and their associated capacity loss mechanisms at high CE.

Disordered GaSiP solid solution anodes with liquid metal phase for high-performance Li-ion batteries

Silicon (Si) has become the most promising next-generation anode to replace commercial graphite for Li-ion batteries (LIBs) profiting from its large reversible capacity of 4,200 mA h g−1. However, its sluggish reaction kinetics and large volume effect need to be resolved. Herein, we prepare a ternary GaSiP solid solution with a disordered lattice by a facile mechanochemistry method. As anodes of LIBs, the GaSiP provides a reversible capacity of 1,527 mA h g−1 at 100 mA g−1 with an initial Coulombic efficiency (ICE) of 90.8% based on the reversible Li-storage mechanism integrated intercalation and subsequent conversion processes as confirmed by crystallography characterization and electrochemical measurements. Importantly, the GaSiP carbon composite presents a long cycling stability of maintaining 1,362 mA h g−1 after 50 cycles at 0.1 A g−1, and 75% capacity retention rate after 1,200 cycles at 2 A g−1, and a high-rate performance of remaining 440 mA h g−1 at 20 A g−1. Broadly, this work opens the door to develop ternary phosphides with disordered lattice and liquid metallic phase using for electrochemical energy conversion and storage.

A direct method to quantify lithium plating on graphite negative electrode of commercial Li-ion cells

The deposition of metallic lithium is a degradation mechanism, also known as lithium plating, that might occur at the negative electrode surface of Li-ion battery cell, especially during fast charging, low temperature charging and high state of charge. The loss of cyclable lithium may lead to irreversible capacity fade and might also bring significant safety hazards. In this context, the experimental quantification of plated lithium on the negative electrode surface could be used to accurately validate electrochemical and physical models that might be used to predict plated lithium without cell opening. Also, the determination of plated Li may help in the evaluation of the safety and aging of commercial cells from different manufacturers for a specific application. This work shows a fast and cost-effective method that can be used to quantify plated lithium on commercial Li-ion battery graphite electrodes.

Image processing methods and light optical microscopy for in-situ quantification of chromatic change and anode dilation in Li-ion battery graphite anodes during (de-)lithiation

Abstract In Lithium-ion batteries, the graphite anode is known to undergo a noticeable chromatic change during lithiation and de-lithiation by forming graphite intercalation compounds. Additionally, the graphite anode primarily contributes to the volume change of the battery. Using a novel in-situ optical microscopy setup for imaging cross-sections of Li-ion full cells, both effects can be studied simultaneously during charging and discharging. In this work, we describe feature extraction methods to quantify these effects in the image data (3730 images in total) captured during the lithiation and de-lithiation process. Automated and manual evaluations are compared. The images show graphite anodes and NMC 622 cathodes. For colorfulness, we evaluate different methods based on classical image processing. The metrics calculated with these approaches are compared to the results of ColorNet, which is a trainable colorfulness estimator based on deep convolutional neural networks. We propose a supervised semantic segmentation approach using U-Net for the layer thickness measurement and the anode dilation derived from it.

A class of Ga-Al-P-based compounds with disordered lattice as advanced anode materials for Li-ion batteries

Phosphides possess large reversible capacity, small voltage hysteresis, and high energy efficiency, thus promising to be new anode candidates to replace commercial graphite for Li-ion batteries (LIBs). Through a facile mechanochemistry method, we prepare a novel ternary phosphide of Ga0.5Al0.5P whose crystalline structure is determined to be a cation-disordered cubic zinc sulfide structure according to XRD refinement. As an anode for LIBs, the Ga0.5Al0.5P delivers a reversible capacity of 1,352 mA h g−1 at 100 mA g−1 with an initial Coulombic efficiency (ICE) up to 90.0% based on a reversible Li-storage mechanism integrating intercalation and subsequent conversion processes as confirmed by various characterizations techniques including in-situ XRD, ex-situ Raman, and XPS and electrochemical characterizations. Graphite-modified Ga0.5Al0.5P exhibits a long-lasting cycling stability of retaining 1,182 mA h g−1 after 300 cycles at 100 mA g−1, and 625 mA h g−1 after 800 cycles at 2,000 mA g−1, and a high-rate performance of remaining 342 mA h g−1 at 20,000 mA g−1. The outstanding electrochemical performances can be attributed to enhanced reaction kinetics enabled by the capacitive behaviors and the faster Li-ion diffusion enabled by the cation-mixing. Importantly, by tuning the cationic ratio, we develop a novel series of cation-mixed compounds of Ga1/3Al2/3P, Ga1/4Al3/4P, Ga1/5Al4/5P, Ga2/3Al1/3P, Ga3/4Al1/4P, and Ga4/5Al1/5P, which demonstrate large capacity, high ICE, and suitable anode potentials. Broadly, these compounds with disordered lattices probably present novel physicochemical properties, and high electrochemical performances, thus providing a new perspective for new materials design.

Mesoscale Machine Learning Analytics for Electrode Property Estimation

The development of next-generation batteries with high areal and volumetric energy density requires the use of high active material mass loading electrodes. This typically reduces the power density, but the push for rapid charging has propelled innovation in microstructure design for improved transport and electrochemical conversion efficiency. This requires accurate effective electrode property estimation, such as tortuosity, electronic conductivity, and interfacial area. Obtaining this information solely from experiments and 3D mesoscale simulations is time-consuming while empirical relations are limited to simplified microstructure geometry. In this work, we propose an alternate route for rapid characterization of electrode microstructural effective properties using machine learning (ML). Using the Li-ion battery graphite anode electrode as an exemplar system, we generate a comprehensive data set of ∼17 000 electrode microstructures. These consist of various shapes, sizes, orientations, and chemical compositions, and characterize their effective properties using 3D mesoscale simulations. A low dimensional representation of each microstructure is achieved by calculating a set of comprehensive physical descriptors and eliminating redundant features. The mesoscale ML analytics based on porous electrode microstructural characteristics achieves prediction accuracy of more than 90% for effective property estimation.

Impact of Laser Structuring and Calendering on Electrode Characteristics and Cell Performance of Li-Ion Battery Graphite Anodes

The strong compression of electrode coatings is a common approach to enhance the volumetric energy density of Li-ion batteries (LIBs). However, it results in a deterioration of the charge and discharge performance due to an increase in the ionic resistance of the electrodes. This conflict can be addressed by microscopic ion diffusion channels in the electrode coatings, which reduce the ionic resistance and thus enhance the performance of a LIB.In this study, the impact of laser micro structuring on different electrode properties was experimentally investigated for graphite anodes with varying initial porosities. All electrodes showed higher porosities after laser structuring, which can be attributed to an increase in the electrodes’ thicknesses and the removal of material. An equivalent circuit was fitted to the electrochemical impedance spectra of symmetric coin cells consisting of structured and pristine graphite anodes, respectively, to determine the ionic resistances, MacMullin numbers and tortuosities. The values were found to increase for decreasing initial porosities. Laser structuring significantly reduced the ionic resistances, MacMullin numbers and tortuosities of the electrodes in comparison to their pristine counterparts. Furthermore, the different graphite anode configurations were paired with NMC cathodes in coin cells and examined in a discharge rate test. At rates over 1 C, a significant increase in the discharge capacity through laser structuring was observed especially for cells with highly compressed anodes. Conclusively, this study empirically quantifies how laser structuring and calendaring influence different electrode characteristics of graphite anodes and the respective performance in LIBs.

Novel Way to Turn Spent Li-Ion Battery Graphite into Valuable and Active Catalyst for Electrochemical Oxygen Reduction

Battery technology has been recognized as one of the main driving forces and key technologies required to create a carbon-neutral economy and, therefore, batteries are currently one of the most rapidly growing technology sectors due to the rapid rise in the number of electric vehicles (EV´s). Additionally, the employment of Li-ion batteries (LIBs) in portable electronics has become a necessity in the modern world. This produces spend Li-ion batteries (SLIBs) in substantial volumes, it was estimated that in 2019 188,000 tonnes of SLIBs were available for recycling and it is expected that this number will rise to 125 million in 2030.1,2 To obtain the full benefits of electrification the value chain associated with batteries needs to become more sustainable, which strongly depends on the ability of SLIBs recycling to maximize the components return back to materials circulation. However, current SLIBs recycling strategies has been focused on cathode materials alone while largely overlooking the anode of the battery. In turn, anode recycling has so far concentrated mostly on the metal in the electrode and only very recently has the focus shifted towards the recycling of graphite powders.In this work, a novel strategy for recycling SLIB graphite and reforming it as a valuable catalyst material for electrochemical oxygen reduction reaction (ORR) is proposed. A modified Hummers method was applied to fabricate graphene oxide (GO) from SLIB graphite powder. The GO reduction and doping with nitrogen was achieved by pyrolyzing sample at 800 °C in the presence of DCDA. The prepared nitrogen-doped graphene (NG-Bat) was characterised by various physicochemical (SEM, TEM, XRD, Raman and XPS) and electrochemical characterization methods (LSV, EIS, chronoamperometry). For electrochemical characterisation RDE setup with the glassy carbon working electrode, modified with studied catalyst, in 0.1 M KOH solution was used. The physical and electrochemical characteristics of NG-Bat were compared with commercially available nitrogen doped graphene (NG-Com) sample.Based on XRD and Raman data, SLIB-derived graphite maintains its high quality, even after intense exploitation in the batteries and is therefore a valuable material that is worth recycling.3 Homogeneous distribution of carbon, nitrogen, and oxygen in NG-Bat sample was achieved and the overall nitrogen content was found to be 18.4 at%, based on XPS analysis. The onset potential of the ORR for the NG-Bat catalyst material is 0.867 V, and for the NG-Com catalyst 0.797 V. The NG-Bat shows a larger oxygen reduction current and higher electrocatalytic activity than the catalyst based on NG-Com (Figure 1). Based on EIS fitting very different charge transfer resistance and double-layer capacitance values are found, probably caused by different conductivities of the catalyst materials. NG-Bat showed much high electrocatalytic activity towards the ORR than commercial NG-Com based-catalyst material, caused probably by a higher content of active nitrogen species and the presence of carbon vacancies on the surface of graphene, as confirmed by XRD, Raman and XPS experiments.The findings demonstrate that SLIB graphite is still a valuable material and a promising precursor for GO fabrication. One of the potential applications of the SLIB-derived graphene could be the production of catalyst material for the oxygen reduction reaction (ORR), thereby open new avenues to the fuel cell, metal-air battery, and sensor industries.

Investigating the Perovskite Ag1-3xLaxNbO3 as a High-Rate Negative Electrode for Li-Ion Batteries.

The broader development of the electric car for tomorrow's mobility requires the emergence of new fast-charging negative electrode materials to replace graphite in Li-ion batteries. In this area, the design of new compounds using innovative approaches could be the key to discovering new negative electrode materials that allow for faster charging and discharging processes. Here, we present a partially substituted AgNbO3 perovskite material by introducing lanthanum in the A-site. By creating two vacancies for every lanthanum introduced in the structure, the resulting general formula becomes Ag1-3xLax□2xNbO3 (with x ≤ 0.20 and where □ is a A-site vacancy), allowing the insertion of lithium ions. The highly substituted Ag0.40La0.20□0.40NbO3 oxide shows a specific capacity of 40 mAh.g-1 at a low sweep rate (0.1mVs-1). Interestingly, Ag0.70La0.10□0.20NbO3 retains 64% of its capacity at a very high sweep rate (50mVs-1) and about 95% after 800 cycles. Ex situ 7Li MAS NMR experiments confirmed the insertion of lithium ions in these materials. A kinetic analysis of Ag1-3xLax□2xNbO3 underlines the ability to store charge without solid-state ion-diffusion limitations. Furthermore, in situ XRD indicates no structural modification of the compound when accommodating lithium ions, which can be considered as zero-strain material. This finding explains the interesting capacity retention observed after 800 cycles. This paper thus demonstrates an alternative approach to traditional insertion materials and identifies a different way to explore not-so common electrode materials for fast energy storage application.

A Stochastic Microstructure Reconstruction-Based Mechanical and Transport Modeling Approach for Learning the Microstructure-Property Relationship of Li-Ion Battery Graphite Anodes

Understanding the relationships between microstructural characteristics and multiphysics properties is key to designing battery electrode materials for desired properties. Significant efforts have been made to achieve a quantitative understanding of the relationship between mass transport properties and Li-ion microstructure characteristics [1-3] in literature, but it is still challenging to predict the coupled mechanical and electrochemical behaviors based on microstructure characteristics.We seek to further this understanding through an investigation of how deformation affects the transport properties of the Li-ion battery graphite anode microstructure, which features packed particles and irregular pore networks. We propose a statistical Microstructure Characterization and Reconstruction (MCR) approach to characterize statistical microstructure features from 2D microscopic images and then reconstruct 3D stochastic microstructures. MCR is an effective tool for material property prediction [4] and microstructure-mediated material design [5]. The proposed MCR approach generates microstructure designs that are beyond the scope of empirical data.By exploring the input microstructure feature space, 3D microstructure samples are reconstructed and simulated to investigate relationships between the microstructural characteristics and properties of Li-ion battery graphite anodes. The selection of microstructure characteristics is informed by an external open access battery microstructures library. For each microstructure reconstruction, compression and transport simulations are conducted to determine the Young’s modulus and to understand the transport properties (e.g. diffusivity) of the undeformed and deformed microstructures. Convergence studies are conducted to establish a Representative Volume Element (RVE) size. With the simulation dataset, the microstructure-property relationship is examined. A feature selection algorithm is used to examine the size of the effects of microstructural characteristics on multiphysics properties. Machine learning models are established to predict the microstructure-property relationship.

First-Principles Analysis for Phase Stability of Li-Intercalated Graphite in Li-Ion Battery

Introduction The rechargeable Li-ion battery (LIB) is a successful energy storage device because of its high energy density and long cycle life. In order to improve its performance, quantitative understanding of elementary reactions in the LIB such as the reaction of Li intercalation from electrolyte solution into graphite and crystal structure change in graphite during the reaction must be a great help. Structure change of Li-intercalated graphite during the charge/discharge processes was recently observed by operando X-ray diffraction measurements using a synchrotron radiation at SPring-8.1 The operando XRD data at LiC18 charge/discharge state exhibited two peaks corresponding two different C-C grid distances in the same plane of graphite, while no change in interlayer distance was detected during the appearance and disappearance of these peaks; it implies only in-plane structure transition such as Li/6C layer to Li/9C layer changes.1 An AA to AB stack transition in graphite was characterized by (101) peak disappearance in the XRD data at the composition between LiC63–LiC72.2 To interpret and discuss these experimental results, we conduct first-principles calculations for the phase stability of graphite. Methods and Models The formation enthalpy ∆H f of Li-intercalated graphite is defined as∆H f (Li n C m ) = ( E DFT(Li n C m ) − nE DFT(Li) − mE DFT(C) ) / (m+n) (1),where E DFT are the total energies of Li-intercalated graphite Li n C m , simple metal Li, and AB stacked graphite C from density functional theory (DFT) calculations. Formation enthalpy as a function of C-ratio, x C = m / (m + n) (2),was used to investigate the phase stability of Li n C m . Quantum ESPRESSO with a plane-wave basis3 and van der Waals functional4 was used to obtain DFT energies. Our previous study using this functional well reproduced the experimental lattice constants and electromotive forces (EMFs) of Li-intercalated graphite.5 It is known that Li-intercalated graphite exhibits stages from 1 to 8. These stages may take different combination of in-plane configurations and interlayer configurations. In-plane configurations considered are Li/6C, Li/9C, Li/18C, and Li/24C, which means the ratios of Li/C atoms are located on a single layer as shown in Fig. 1 (a). Three interlayer structures are considered here; (1) graphite layers stacked with AA overlap, (2) with AB, and (3) mixed (Li including layers are AA stacked, the other layers are AB stacked). Conventional LiC6 intercalated phase corresponds to the stage 1 of Li/6C AA stack structure (denoted as s1-Li/6C-AA, here s1, s2, s3, ... represents stage 1, stage 2, stage 3, ..., respectively). Results The calculated formation enthalpies ∆H f are plotted as a function of x C in Fig. 1 (b). At the composition of LiC6 (x C = 0.857), LiC12 (x C = 0.923), and C (x C = 1), respective most stable phases are s1-Li/6C-AA, s2-Li/6C-AA, and AB stack graphite ones as we could expect. At the composition of LiC18 (x C = 0.947), s2-Li/9C-AA structure is more stable than the s3-Li/6C-AA structure, which is consistent with the experimental observation.1 AB stack structures are more stable than AA at x C > 0.97 from the theoretical calculation, while the AA-AB transition has been observed at 0.984 < x C < 0.986 by experiments. At higher stages (x C > 0.94), mixed stack structure is predicted to be more stable than simple AA and AB structures. The formation enthalpies of s2-Li/9C-mixed and s3-Li/6C-mixed are almost the same (within 0.01 meV/atom) and these configurations are predicted to be the most stable at LiC18. However, these mixed stackings have not been detected by experiments. In the presentation, we will also present the theoretical EMF values of the Li-intercalated graphite electrode and compare them with experimental results. Acknowledgments This work was supported in part by the Research and Development Initiative for Scientific Innovation of New Generation Batteries 2 Project (RISING2) administrated by the New Energy and Industrial Technology Development Organization (NEDO). References S. Takagi, K. Shimoda, H. Fujimoto, H. Kiuchi, T. Naka, T. Murata, K.-I. Okazaki, T. Fukunaga, E. Matsubara, Z. Ogumi, and T. Abe, “Operando Structure Analysis of Graphite Electrode by Synchrotron Radiation Diffraction” The 60th Battery Symposium, 1B20 (2019).H. Fujimoto , S. Takagi , H. Kiuchi , K. Shimoda , K.-I. Okazaki, T. Murata , T. Abe, Z. Ogumi, and E. Matsubara, “Operando analysis of charge/discharge reaction mechanism of graphite anode of Li ion battery using synchrotron radiation diffraction, Second report”, The 59th Battery Symposium, 2E16 (2018).P. Giannozzi et al., J. Phys.: Condens. Matter 21, 395502 (2009); ibid. 29, 465901 (2017).I. Hamada, Phys. Rev. B 89, 121103(R) (2014).J. Haruyama, T. Ikeshoji, and M. Otani, J. Chem. Phys. C 122, 9804 (2018). Figure 1

Novel Way to Turn Spent Li-Ion Battery Graphite into Valuable and Active Catalyst for Electrochemical Oxygen Reduction

Employing Li-ion batteries (LIBs) in portable electronics has become a necessity in the modern world but, due to the short application time for any given battery (1-3 years) [1], the quantity of spent LIBs (SLIBs) waste is becoming substantial. As LIBs contain different valuable materials (the cathode layer holds Li, Co, Ni, Mn, Al and the anode layer graphite and Cu), the recycling of SLIBs is economically and environmentally beneficial. Additionally, the potential resource strain, as well of the geographical limitations found in the mining/production of the raw materials, will make recycling crucial for sustainable production of LIBs. However, current SLIBs recycling strategies has been focused on cathode materials alone while largely overlooking the anode of the battery [1–3]. In turn, anode recycling has so far concentrated mostly on the metal in the electrode and only very recently has the focus shifted towards the recycling of graphite powders.In this work, a novel strategy for recycling SLIB graphite and reforming it as a valuable catalyst material for electrochemical oxygen reduction reaction (ORR) is proposed. A modified Hummers method was used to fabricate graphene oxide (GO) from SLIB graphite powder. The GO doping was done by pyrolyzing at 800 °C in the presence of dicyandiamide (DCDA). The mass ratio of GO-to-DCDA was 1:20. The prepared nitrogen-doped graphene, from SLIB graphite powder, (NG-Bat) was characterised by various physical (XRD, Raman, XPS, SEM, TEM) and electrochemical characterization methods. Electrochemical properties of the catalyst material was investigated by using the rotation disc electrode voltammetry and electrochemical impedance methods. For electrochemical characterisation the glassy carbon (CG) electrodes were modified with synthesized catalyst and the experiments were carried out in 0.1 M KOH solution. The GC disc electrodes were modified with NG ethanol suspensions (4 mgcatalyst ml-1) containing 6 µl aQAPS-S14 (2%) ionomer from Hephas Energy per 1ml ethanol. The physical and electrochemical characteristics of NG-Bat were compared with commercially available nitrogen doped graphene (NG-Com).Based on XRD and Raman data, it was shown that SLIB-derived graphite maintains its high quality, even after intense exploitation in the batteries and is therefore a valuable material that is worth recycling. The homogeneous distribution of carbon, nitrogen, and oxygen in NG-Bat was demonstrated by elemental mapping. The overall nitrogen content in NG-Bat was found to be 18.4 at%, from which pyridinic N constitutes 55.5 at%, graphitic N 21.7 at%, pyrrolic N 17.8 at% and oxidized N 5.0 at%. The onset potential of the ORR for the NG-Bat catalyst material is −0.11 V, and for the NG-Com catalyst −0.18V (Figure 1). The NG-Bat shows a larger oxygen reduction current and higher electrocatalytic activity than the catalyst based on NG-Com. Based on EIS fitting results very different charge transfer resistance and double-layer capacitance values are achived, probably caused by different conductivities of the catalyst materials. Catalyst material NG-Bat showed much high electrocatalytic activity towards the ORR than did a NG-Com, caused probably by a higher content of active nitrogen species and the presence of carbon vacancies on the surface of graphene, as confirmed by XRD, Raman and XPS experiments.These findings demonstrate that SLIB graphite is still a valuable material and a very suitable precursor for GO fabrication and SLIB anode layer needs to be recycled and returned to usage in a new form. Based on the result of this work, one of the potential applications of the SLIB-derived graphene could be the production of catalyst material for the oxygen reduction reaction (ORR), thereby open new avenues to the fuel cell, metal-air battery, and sensor industries.

Engineered Particle Synthesis by Dry Particle Microgranulation

Uniform ∼10-μm particles are important in several applications, including the metal oxide and graphite active materials in Li-ion batteries. Current production methods (e.g., co-precipitation and spheronization) can be wasteful and have limited composition scope. Here, we report dry particle microgranulation (DPMG) as a method for synthesizing highly engineered particles by consolidating fine, even submicron particles into particles that are tens of microns. DPMG enables the precise control of particle internal composition variation, shape, and morphology that is not possible by previous methods and at near 100% yields with no waste. Using this method, we show that Li-ion battery graphite and metal oxide particles, including those with designed internal composition variation, can be made at 100% yield with little waste. We believe that DPMG could be used in many fields to reduce the cost and environmental impact of particle synthesis and to enable the synthesis in bulk of new, highly engineered particles.

Solvent-induced synthesis of hollow structured Fe3O4-based anode materials for high-performance Li-ion batteries

High capacity Fe3O4-based anode materials have attracted a great deal of attention as an alternative to commercial graphite in Li-ion batteries (LIBs). However, it is still a challenge to alleviate the fast capacity fading of Fe3O4 due to the intercalation of Li+. In this work, we develop a novel and effective strategy to rapidly fabricate the hollow Fe3O4 nanostructures via the solvent-induced effect. The influence of the ratio of the tert-butanol (TB) and the water on the microstructure was further discussed. As expected, when the hollow nanostructures based on the 1:1 ratio of TB and water is used as the anode material for LIBs, a high reversible capacity of 1020 mA h g−1 after 100 cycles at 1 A g−1 and 450 mA h g−1 even for 5 A g−1 after 1000 cycles can be obtained, paving a new avenue to fabricate the functionally hollow nanostructures for high-performance anode materials or other applications.

Three-dimensional graphene networks modified with acetylenic linkages for high-performance optoelectronics and Li-ion battery anode material

Searching for three-dimensional (3D) semiconducting carbon allotropes with proper bandgaps and excellent optoelectronic properties is always the chasing goal for the new emerging all-carbon optoelectronics. On the other side, 3D carbon materials have also been recognized as promising anode materials superior to commercialized graphite in Li-ion batteries (LIBs). Here, using first-principles calculations, we propose two novel 3D carbon allotropes through acetylenic linkages modification of two structurally intimately correlated 3D carbon structures — carbon kagome lattice (CKL) and interpenetrated graphene network (IGN). The modified CKL is a truly direct-gap semiconductor and possibly possesses the strongest optical transition coefficient amongst of all semiconducting carbon allotropes. The suitable bandgap and small effective masses also imply it can be a good electron transport material (ETM) for perovskite solar cells. As for the modified IGN, it is a topological nodal line semimetal and shows greatly enhanced specific capacity as anode materials in LIBs comparing to that of IGN. Our work not only find two new 3D carbon phases with fabulous physical and chemical properties for high-performance optoelectronics and Li-ion anode material, we also offer a fresh view to create various carbon structures with versatile properties.

Confining SnSe nanobelts in 3D rGO aerogel for achieving stable and fast lithium storage

Tin selenide (SnSe) shows great potential as a promising anodic candidate of commercial graphite in Li-ion batteries (LIBs), but its practical application is hampered by huge volume change-induced poor cycle span. Herein, a gel-enabled selenization route has been developed for uniformly confining SnSe nanobelts within reduced graphene oxide aerogel (SnSe NB@rGO framework). These unique structural and compositional features make the SnSe NB@rGO framework electrode to show high revisable capacities (620 mA h g−1 after 200 cycles at 0.1 A g−1), high rate capability (626 and 551 mA h g−1 at 0.5 and 1 A g−1, respectively) and ultralong cycle span (412 mA h g−1 after 800 cycles at 1 A g−1).

Modification of natural Ukrainian graphite using nanostructured oxides. Increasing performance of anodes and cathodes of Li - ion batteries

The surface modification of natural Ukrainian graphite by the nanostructured zirconium oxide (ZrO2) developed by the authors of the article increases the specific reversible discharge capacitance and the stability of the electrode cycling in Li batteries with non-aqueous electrolyte compared with electrodes based on unmodified graphite. This applies both to anodes, based on modified graphite in Li-ion batteries, and to cathodes with modified graphite as an electrically conductive additive. Modification of graphite with zirconium oxide was carried out in solutions of isopropyl and isobutyl alcohols with subsequent heat treatment at a temperature of 120°C and 500°C. The service life of electrodes based on graphite modified in isopropyl solution was 1300 cycles, the degree of capacity decrease during the cycling process was 0.031 mA·h/g per cycle. Lithium power sources, for which the use of modified graphite is planned, are based on the following Ukrainian raw materials: graphite, manganese and zirconium.

Preparation of Composites of Nano-Silicon and Spherical Natural Graphite for Li-Ion Batteries By a Drop-in Technology

We will describe a methodology to prepare nano-Si / natural graphite composite using an established transformation manufacturing process without significant changes to the initial process flow, thus minimizing the cost of implementation. First, a baseline was established by investigating half-cells made with anode using a mixture of coated spherical natural graphite, nano-Si and LiPAA binder. Then, a composite of graphite / nano-Si was prepared by carbonizing a dry mixture of spherical graphite, nano-Si and petroleum pitch. The silicon content was below 20 wt.% toward graphite and the pitch-to-nano-Si was optimized. Following these guidelines, a series of Si/graphite composites were prepared by first performing a spheronization process to a dry mixture of natural graphite flakes, nano-Si and carbon precursors to disperse the silicon in the core and on the surface of the graphite matrix. Followed by a carbonization step to form the amorphous carbon coating simultaneously on the graphite and nano-Si surface. The morphology and chemical composition of the composites' surface was investigated using XPS, SEM and HRTEM and the possible formation of silicon oxides or carbides was evaluated by XRD. Tap density, surface area and PSD were performed to assess if the prepared powders reached the battery grade specifications. The composites show very high reversible capacity when evaluated in coin-type, Li-ion half cells.