Replacement For Graphite Research Articles

Heterogeneous Engineering Strategy Derived In Situ Carbon-Encased Nickel Selenides Enabling Superior LIBs/SIBs with High Thermal Safety.

Nowadays, the extended usage of lithium/sodium ion batteries (LIBs/SIBs) encounters nerve-wracking issues, including a lack of suitable reservoirs and high thermal runaway hazards. Although using TiO2 and Li4Ti5O12 has been confirmed to be effective in improving battery safety, their low theoretical capacities inevitably cause damage to the electrochemical performance of the battery. Achieving win-win results has become an urgent necessity. This study designed a metal-organic framework (MOF)-derived in situ carbon-coated metal selenide (Ni-Se@G@C) as the anode. When the current density is 0.1-0.3 A g-1, the initial capacity of LIBs reaches 993.2 mAh g-1, which increases to 1478.9 mAh g-1 after running 800 cycles. When running at 2 A g-1, the cell also offers a relatively high capacity of 458.3 mAh g-1 after 1500 cycles. After the replacement of graphite with Ni-Se@G@C, the self-heating temperature (T0) and thermal runaway triggering temperature (T1) of half and full cells are significantly increased. Meanwhile, the maximum thermal runaway temperature (T2) and maximal heating release rate (HRRmax) are significantly reduced. Of note, the usage of Ni-Se@G@C enables the battery with superior cycling and rate performance. When used in SIBs, the cell gives an initial discharge capacity of 624.9 mAh g-1, which still remains at 269.4 mAh g-1 after running 200 cycles at 1 A g-1. Notably, Ea of the Ni-Se@G@C cell is 5.6 times higher than that of the graphite cell, corroborating the promoted safety performance. This work provides a new paradigm for MOF-derived micro/nanostructures, enabling the battery with an excellent electrochemical and safety performance portfolio.

Optimization of Si-containing and SiO based Anodes with Single-Walled Carbon Nanotubes for High Energy Density Applications

Lithium-ion batteries require a high energy density when being used in applications such as electric vehicles or portable electronics. This can be achieved on a large scale by improving packaging and implementation, or on a material scale by selecting more energy dense electrode active material. Silicon can be used as a replacement for graphite in negative electrodes if the detrimental volume expansions can be contained. These volume expansions cause continuous mechanical degradation capacity loss leading to short lifetimes that do not meet industry standards. These high-capacity high volume expansion materials such as silicon and SiO must be used in conjunction with more stable electrode materials like graphite to reduce the mechanical degradation caused by volume change. Single-walled carbon nanotubes are shown to be a simple yet effective drop in addition to improve electrical connectivity and increase capacity retention in these silicon-based composite negative electrodes. This added particle interconnectivity from the high tensile strength carbon nanotubes allows for the use of simple binders such as CMC/SBR to create composite electrodes with competitive performance without the use of expensive polymers or complex nanostructures.

Reactor Performance and Safety Characteristics of Beryllium-Based Composite Moderators as Replacements for Graphite in mHTGRs

This study evaluates beryllium-based two-phase composite moderators as an alternative to graphite in an evaluation of reactor performance and safety characteristics. Historically, modular high-temperature gas-cooled reactors (mHTGRs) use graphite as a moderator because of its high moderating ratio and reasonable thermal properties; however, graphite has unfavorable properties under irradiation, which can require component replacement and a significant radioactive waste burden. In this assessment, we explore advanced moderators comprised of magnesium oxide (MgO) as the host matrix and beryllium metal and/or beryllium oxide (Be and/or BeO) as the entrained moderating phase. For the reactor performance and thermal-hydraulic safety analysis, the core design model of the General Atomics mHTGR-350 was used to demonstrate the feasibility of a “drop-in” replacement of graphite using the beryllium-based moderators. We employed the neutronics code Serpent to analyze the moderating behavior of the composite moderators with comparisons drawn to graphite. We performed a scoping analysis of accidents for mHTGRs using RELAP to show that these moderators do not present impediments to safety and are expected to stay within temperature limits. Measured thermophysical properties of the composite moderators are used in the thermal-hydraulic assessments. Our analysis reveals that the two-phase composite MgO-matrix beryllium-based moderators are a suitable replacement for graphite.

Ceramic composite moderators as replacements for graphite in high temperature microreactors

Engineered composites composed of a radiation stable continuous matrix containing a highly moderating entrained phase are attractive candidates for the realization of bulk materials that are structurally and neutronically superior to nuclear graphite. Here, we explore neutronics driven selection of entrained moderating phases in MgO-based ceramic composites with a focus on the MgO-BeO system given its exceptional moderating power and high temperature stability. Using lithium-bearing salts as sintering aids, fully dense MgO-BeO composites with BeO loading up to 40 vol.% are produced through direct current sintering at markedly reduced temperatures relative to phase-pure MgO. Thermophysical properties mapped as a function of the BeO concentration are shown to align with various composite models, thus revealing the influence of underlying defects on the thermophysical property trends. From microreactor neutronics and thermal hydraulic calculations, the MgO-40BeO moderator is shown to increase both cycle length and fuel utilization relative to graphite and with steady-state temperature distributions remaining within specification. The ceramic composite moderators outperform graphite for all metrics considered with significant potential demonstrated for reducing energy costs while enabling novel microreactor designs through the replacement of graphite.

Effect of vinylene carbonate electrolyte additive and battery cycling protocol on the electrochemical and cyclability performance of silicon thin-film anodes

The use of silicon as a replacement for graphite, the commonly utilised anode material, would help increase the energy density of lithium-ion batteries, as it has a significant specific capacity of 4200 mAh/g compared to only 372 mAh/g for graphite. However, the high electronic resistivity and low mechanical stability of silicon have hindered its commercial uptake. In this contribution, we have employed a multifaceted approach in order to enhance the capacity retention of pure silicon anodes. The effect of adding 5 vol. % vinylene carbonates to a standard electrolyte has been examined with respect to the performance of physical vapour deposited pure Si thin films. Changes in battery cycling parameters (i.e., lower and upper cut-off voltages and depth of discharge were examined using charge/discharge cycling, cyclic voltammetry, and electrochemical impedance spectroscopy, indicating that cycling stability and electrochemical performance of the anodes were heavily influenced by these changes. The effect of each procedure (i.e., electrolyte additive and battery cycling protocol) on the initial discharge capacity, initial coulombic efficiency, initial irreversible capacity, capacity retention, and the lithium-ion diffusion coefficient into the silicon anode was examined. The Si film with optimised: deposition conditions, electrolyte additives, and battery testing protocol had a discharge capacity of 1740 mAh/g and capacity retention of 92 % at a charge/discharge rate of C/2 after 1000 cycles.

Stable SEI Formation on Al-Si-Mn Metallic Glass Li-Ion Anode

Alloying anodes are of great interest as a replacement for graphite in lithium-ion batteries (LIBs) since they can store one or more Li atoms per host atom. Si has received the most attention in this regard due to its very high theoretical specific capacity (3579 mAh/g, ~8300 mAh/cm3)1 and relatively low cost. However, the durability of batteries with high Si content is limited due to the unstable solid-electrolyte interphase (SEI) on Si2 and its large volume change upon lithiation and delithiation which leads to cracking and pulverization3, 4. Among alloying anodes, amorphous materials generally outperform crystalline materials5, 6. The absence of grain boundaries can improve passivity7-9, and amorphous materials generally lithiate in a continuous manner, which eliminates phase boundaries and the mechanical strains associated with them. In addition, amorphous materials composed solely of metals and/or metalloid elements, termed metallic glasses, have been shown to exhibit exceptional hardness, yield strength, and fracture toughness7-9.This study explores an Al-Si-Mn glass as an alternative LIB anode. Si-based metallic glasses are appealing because they maintain Si, which can alloy with up to 3.75 Li6, 10, as the main Li-binding element, but distribute it homogeneously within an amorphous matrix. A dense amorphous Al64Si25Mn11 metallic glass (a-AlSiMn) was successfully produced via splat quenching, a rapid cooling technique that is scalable and commonly used to produce amorphous materials for a variety of applications. This process is shown schematically in the figure below. The a-AlSiMn glass exhibits greater specific capacity (>900 mAh/g) than graphite and a low lithiation potential, making it suitable for high-energy density LIBs. The glass remains amorphous throughout cycling, maintaining any improved mechanical properties conferred by the amorphous structure.Crucially, parasitic electrolyte reduction is found to be much reduced in comparison to pure Si or Al, and comparable to that on Cu. The charge consumed by electrolyte reduction in each cycle is given in the figure below for a-AlSiMn and an amorphous Si reference anode. The resulting SEI on a-AlSiMn is very thin, and rich in fluorinated species such as LiF, F-P-O groups, and fluorinated oxides of silicon and aluminum, whereas very few organic species are present. In particular, lithium ethylene decarbonate (LiEDC), which plays a large role in SEI formation on Si, is entirely absent, and a thinner, more stable SEI results. This study shows that metallic glasses can become a viable new class of alloying anode materials for LIBs with improved surface passivity. Li, J.; Dahn, J. R., An In Situ X-Ray Diffraction Study of the Reaction of Li with Crystalline Si. Journal of The Electrochemical Society 2007, 154 (3), A156.Yin, Y.; Arca, E.; Wang, L.; Yang, G.; Schnabel, M.; Cao, L.; Xiao, C.; Zhou, H.; Liu, P.; Nanda, J.; Teeter, G.; Eichhorn, B. W.; Xu, K.; Burrell, A. K.; Ban, C., Non-Passivated Silicon Anode Surface. ACS applied materials & interfaces 2020.Kasavajjula, U.; Wang, C.; Appleby, A. J., Nano- and bulk-silicon-based insertion anodes for lithium-ion secondary cells. Journal of Power Sources 2007, 163 (2), 1003-1039.Liang, B.; Liu, Y.; Xu, Y., Silicon-based materials as high capacity anodes for next generation lithium ion batteries. Journal of Power Sources 2014, 267, 469-490.Beaulieu, L. Y.; Hatchard, T. D.; Bonakdarpour, A.; Fleischauer, M. D.; Dahn, J. R., Reaction of Li with Alloy Thin Films Studied by In Situ AFM. Journal of The Electrochemical Society 2003, 150 (11), A1457.Hatchard, T. D.; Topple, J. M.; Fleischauer, M. D.; Dahn, J. R., Electrochemical Performance of SiAlSn Films Prepared by Combinatorial Sputtering. Electrochemical and Solid-State Letters 2003, 6 (7), A129.Chen, M., A brief overview of bulk metallic glasses. NPG Asia Materials 2011, 3 (9), 82-90.Jafary-Zadeh, M.; Praveen Kumar, G.; Branicio, P. S.; Seifi, M.; Lewandowski, J. J.; Cui, F., A Critical Review on Metallic Glasses as Structural Materials for Cardiovascular Stent Applications. Journal of Functional Biomaterials 2018, 9 (1), 19.Telford, M., The case for bulk metallic glass. Materials Today 2004, 7 (3), 36-43.Fleischauer, M. D.; Dahn, J. R., Combinatorial Investigations of the Si-Al-Mn System for Li-Ion Battery Applications. Journal of The Electrochemical Society 2004, 151 (8), A1216. Figure 1

Evidence for stepwise formation of solid electrolyte interphase in a Li-ion battery

Replacement of graphite with alloying and conversion materials, having high specific capacity, has emerged as versatile route to increasing the energy density of Li-ion batteries. A key challenge is the large volume change in these materials, which leads to an unstable solid electrolyte interphase (SEI). The use sacrificial electrolyte additives, such as fluoroethylene-carbonate (FEC), has been established as an effective strategy for considerably improving cycling stability, but a mechanistic understanding of the underlying processes has been lacking so far. Here, we present an in-depth chemical and morphological study of the FEC-based interphase on graphite and SnO2–graphite model electrodes. We found that the FEC decomposition products aggregate first into spherical particles, whose growth depends on the cell medium and follows the laws of crystal-growth theory, before forming a continuous carbonate-rich film. The discrimination of the chemical composition of the FEC-derived particles from the rest of the electrode was obtained by X-ray photoemission electron microscopy (XPEEM) due to the high lateral resolution of this technique. The obtained understanding of SEI formation in fluorine-rich electrolytes should help to guide future designs of sacrificial fluorine-based additives.

In Ukrainian

Even partial replacement of graphite in the anode of lithium-ion batteries with silicon can significantly increase their specific energy. But the issue is the insufficient life cycle of such batteries due to the accelerated degradation of the liquid organic electrolyte with traditional lithium hexafluorophosphate, especially at elevated temperatures. The subject of discussions and further research are the processes involving a natural oxide layer on the surface of silicon in the manufacture and electrochemical litiation–delitiation of Si-containing electrodes. Among the most promising areas for solving the issues of practical application of silicon are new additives to the electrolyte and polymeric binders for electrode masses. This paper demonstrates the capability of trimethylsilylisocyanate (with aminosilane and isocyanate functional groups) as an additive to a liquid organic electrolyte (LiPF6 / fluoroethylene carbonate + ethyl methyl carbonate + vinylene carbonate + ethylene sulfite) to scavenge the reactive HF and PF5 species that alleviates the thermal decomposition of fluoroethylene carbonate at elevated temperatures. This makes it possible to increase the electrochemical parameters of half-cells with a hybrid graphite–nanosilicon working electrode when using water-based binders – carboxymethylcellulose and styrene-butadiene rubber. The addition of trimethylsilylisocyanate in the electrolyte significantly improves the reversible capacity of hybrid electrodes and reduces the accumulated irreversible capacity during prolonged cycling at normal temperature and after exposure at 50 °C, therefore to be effective for use in high-energy lithium-ion batteries.

Replacement of Graphite by Petroleum Coke in Rail Lubricants

The replacement of graphite by petroleum coke in lubricants for railroad lines is considered. The lubricant consists of petroleum coke, spent diesel oil, and low-molecular polyethylene. On mixing, these components form a system that is stable on storage. The particle size of the petroleum coke is selected so as to minimize wear of the metal. The hydrocarbons employed are biodegradable; that minimizes their environmental impact. The proposed lubricant has been successfully used by the East Siberian Railroad on curved track and at switches. It is easy to apply, does not drip, and is transferred by the wheels of rail cars to ensure uniform distribution over the rail’s lateral surface.

Anode material firm raises $18 million

Washington State–based Group14 Technologies has raised $18 million from investors to scale up output of its silicon-based anode material, which it says could significantly enhance the performance of lithium-ion batteries. The investors are the industrial companies Amperex Technologies, BASF, Cabot, and Showa Denko, as well as the venture capital firm OVP Venture Partners. Group14 says its anode material, composed of nanostructured porous carbon and silicon, is a drop-in replacement for graphite.

Wacker invests again in battery materials firm

The silicon maker Wacker Chemie is taking a 25% stake in Nexeon, a British company that is developing a silicon-based replacement for graphite as the anode of lithium-ion batteries. Wacker already has a research pact with Nexeon and bought a stake of undisclosed size in the firm in 2013. A Nexeon competitor, Sila Nanotechnologies, raised $70 million from investors last year.

Free Standing Silicon Microparticle and Self-Healing Polymer Composite for High-Energy Lithium-Ion Anode Applications

Developing a commercially viable silicon anode as a replacement for graphite has been the topic of intense research and discussion. Numerous attempts have been made including the use of nanoscale structures smaller than silicon’s critical fracture size (e.g. nanoparticles, nanowires, nanotubes, etc.). However, nanoscale structures, while sufficiently effective in lab scale, are difficult and expensive to scale up. To address this issue, applying a thin coat of polymer with self-healing chemistries has been reported as an effective remedy to enhance the cycle life of the silicon microparticle anode. The self-healing chemistry enabled mechanical fractures generated during the cycling process to self-heal. As a result, excellent cycle life was obtained compared to conventional microscale anodes. However, there still is room to improve the mechanical and electrochemical performances of the anode, most notably areal capacity and flexibility, while using large scale processes. In this study, a free standing silicon microparticle and self-healing polymer (SiSHP) composite is fabricated demonstrating long cycle life while still retaining high capacity (up to ~2,800mAhg-1 and ~3.5mAhcm-2) without a metal foil current collector. SiSHP composite is prepared by simple, inexpensive, and scalable approach. The SiSHP composite consists of silicon microparticles embedded within a self-healing polymeric matrix providing sufficient space for volume expansion during lithiation. The self-healing chemistry reduces irreversible loss of electric contact due to mechanical degradation prevalent in conventional slurry cast silicon electrode design. In addition, because the SiSHP composite eliminates the need for a metal current collector, adhesion issues between the electrode and current collector that arise with repeated bending are eliminated, thereby ensuring minimal loss in mechanical and electrochemical properties even after undergoing repeated bending. We found that a 1:1 Si/SHP weight ratio with 10 wt. % carbon conductive additive exhibits the optimal balance between high capacity and providing sufficient polymer matrix for stable cycling behavior. The fabricated SiSHP composite is moldable into the required shape and dimension ranging from millimeter to tens of centimeter-scale. The freestanding feature of the SiSHP composite anode eliminates the need for a metal foil current collector thereby reducing the non-active mass, which is beneficial to enhancing capacity and energy density of Lithium-ion cells.

High Energy Lithium Ion Batteries Based on Cobalt Rich Composite Cathode and Silicon Anode

Batteries are the main limitation to the wide spread adoption of electric vehicles and plug in hybrids. Battery energy density must be improved to increase EV driving range and lower battery cost. State of the art high energy lithium batteries use NCA cathode and graphite anode e.g. cylindrical 18650 cells that can provide specific energy up to 250 Wh/kg. Replacement of graphite with silicon based anode is mandatory to further boost specific energy. However, cells with silicon based anode have poor cycle life and very high swelling. Proper selection of cathode is also important to attain high energy density when paired with Silicon based anode. Although the capacity of Si-based anode materials are high, their intercalation potential is much higher than that of Li or graphite which translates to a lower overall cell voltage (at least 0.4V lower) resulting in lower energy density. A high capacity and high average voltage cathode is required to compensate the overall drop in the average voltage. In this work, Cobalt-Rich Composite (CRC) cathode has been developed that also contains significant amount of Nickel and Manganese. The resulting CRC cathode shows stable high voltage performance compared to LCO. Traditionally the structure of LCO cathode degrades at high charge voltages (>4.4V) when >0.5 moles of Li are extracted from the structure. The CRC cathode enables high electrode active content (>97%) and high electrode density (>4.0g/cc), high average voltage (3.95V) and high specific capacity (>190 mAh/g in half cell). Most importantly, CRC cathode does not exhibit any voltage fade upon cycling at higher voltages (>4.45V) as observed in lithium rich manganese rich composite cathode. CRC cathode has been complemented with a high capacity SiOx-based anode electrode in a high energy cell. Typical commercially available Si-based materials suffer from large volume expansion resulting in pulverization and poor cycle life. We present high capacity SiOx-based anode (>1400 mAh/g) electrodes with high percent active content (>80%) that has shown to cycle over 500 times. A novel anode fabrication approach has been used taking advantage of a high strength binder, carbon nanotube network and pre-lithiation. Swelling, cycling and abuse testing results of the cells will be presented. Figure 3 shows 10Ah capacity pouch cells integrating CRC cathode and SiOx anode with specific energy of ~350Wh/Kg. The cells show excellent rate capability as required for automotive and drone applications. There is significant energy above lower cut off voltage 3.0V required by consumer electronic devices. This presentation will also cover remaining challenges associated with CRC cathode and SiOx anode with respect to synthesis, performance and cell manufacturing. Figure 1

Study of the Expansion/Contraction Behavior of Si-Based Electrodes By Electrochemical Dilatometry

The replacement of graphite by silicon as the active material in negative electrodes of Li-ion batteries is very attractive since the specific capacity of Si is 10 times higher than that of graphite. However, Si suffers from huge volume variation (up to ~300% vs 10% for C) during its lithiation. This leads to the electrode/particle cracking which induces electrical disconnections in addition to cause an instability of the solid electrolyte interface (SEI), resulting in poor cycle life and low coulombic efficiency. A precise evaluation of the expansion/contraction behavior of the Si-based electrodes upon cycling is thus highly relevant to develop more efficient electrode formulations. For this purpose, a simple and efficient method consists of integrating a contact displacement transducer to the electrochemical cell, which permits a measurement of any thickness change of the working electrode upon its charge and discharge as shown hereafter. In the present study, electrochemical dilatometry experiments are performed on silicon/carbon/carboxymethylcellulose (Si/C/CMC) composite electrodes. It is shown that the pH of the slurry (pH 7 vs. buffered pH 3) and the size of the Si particles (1-5 µm vs. 85 nm) have a major impact on their electrochemical performance (Fig. 1) and their expansion/contraction behavior (Fig. 2a-c). During the first discharge (lithiation), a maximum electrode thickness expansion of ~130% is observed for the pH3-micro Si electrode (Fig. 2b). compared to ~330% for the pH7-micro Si electrode. (Fig. 2a). A lower irreversible expansion is also observed at the end of the 1st cycle (~50% compared to ~180% for the pH7 electrode). It can be explained by the the formation of more cohesive (covalent) bonds between the Si particles and the CMC chains when the electrode is prepared with a slurry buffered at pH 3, increasing the mechanical strength of the composite electrode and its ability to reversibly sustain the volume variations of the silicon particles. 1,2 However,when the 1-5µm Si is replaced by 85 nm Si, a very large and abrupt expansion/contraction of the electrode is observed (up to 500%, see Fig. 2c), resulting in a significant decrease of the electrode cycle life (Fig. 1). It may be related to the higher specific surface area and/or lower surface oxidation state of the nanosized Si powder, inducing a less efficient grafting of the CMC binder at the surface of the Si particles. 3 Additionaldilatometric experiments with oxidized Si nanoparticles and with different CMC amounts will be presented to address this issue. 1. D. Mazouzi, B. Lestriez, L. Roué, D. Guyomard. Silicon composite electrode with high capacity and long cycle life. Electrochem. Solid State Let. 12 (2009) A215-A2182. 2. A. Tranchot, P-X. Thivel, H. Idrissi, L. Roué. Impact of the slurry pH on the expansion/contraction behavior of silicon/carbon/carboxymethylcellulose electrodes for Li-ion batteries. J. Electrochem. Soc., submitted. 3. N. Delpuech, D. Mazouzi, N. Dupré, P. Moreau, M. Cerbelaud, J. S. Bridel, J.-C. Badot, E. De Vito, D. Guyomard, B. Lestriez, and B. Humbert. Critical Role of Silicon Nanoparticles Surface on Lithium Cell Electrochemical Performance Analyzed by FTIR, Raman, EELS, XPS, NMR, and BDS Spectroscopies. J. Phys. Chem. C 118 (2014) 17318−17331. Figure 1

Metal Oxide/Reduced Graphene Oxide Anodes for Lithium-Ion Batteries

Lithium-Ion Batteries (LIBs) have completely conquered the portable electronic devices market due to their high energy density and cycle life. However, in order to make them suitable for grid-scale or long-range automotive applications, it is necessary to find new materials with higher intrinsic energy density than the state-of-the-art. Metal oxides (MOs) have received considerable attention in recent years as a replacement for graphite at the anode. MOs can provide on average a theoretical capacity around double that of graphite (ca. 700 mAh/g versus 372 mAh/g) and recent studies have shown that acceptable capacity retention can be achieved. Though morphology certainly plays a role in the performance of MO anodes, conductivity is likely the determining factor that dictates material cycleability. Replacement of traditional carbon additives with non-dilutive, high conductive carbons has the potential to yield very high capacity electrodes with excellent capacity retention.

Characterisation of Si-Based Anodes for Li-Ion Batteries By Operando Dilatometry and Acoustic Emission Measurements

The replacement of graphite by silicon as the active material in negative electrodes of Li-ion batteries is very attractive since the specific capacity of Si is 10 times higher than that of graphite. However, Si suffers from huge volume variation (up to ~300% vs 10% for C) during its lithiation. This leads to the electrode cracking which induces electrical disconnections in addition to cause an instability of the solid electrolyte interface (SEI), resulting in poor cycle life and low coulombic efficiency. A precise evaluation of the electrode volume variation and cracking upon cycling is thus crucial to develop more efficient Si-based anodes. To date, the study of their morphological changes is usually limited to post mortemexaminations by microscopy. This does not allow a detailed analysis of the morphological degradation process, which can significantly vary depending on the electrode composition and processing, and the charge/discharge conditions. In the present study, the volume change with cycling of Si-based anodes is monitored by operando dilatometry experiments. For that purpose, a specific displacement transducer is used, which allows measuring expansion or shrinkage of the electrode during cycling down to the sub-micrometer range. Operando acoustic emission (AE) measurements are also performed to study the electrode cracking [1]. The AE technique is based on the detection and analysis of transient elastics waves generated by stress events. The influence of the cycling conditions and electrode formulation on the volume variation and cracking of Si-based electrodes is highlighted, and correlated to their electrochemical performance. [1] A. Tranchot, A. Etiemble, P-X. Thivel, H. Idrissi, L. Roué In-situ acoustic emission study of Si-based electrodes for Li-ion batteries, J. Power Sources 279 (2015) 259-266.

A review on porous negative electrodes for high performance lithium-ion batteries

Today’s lithium(Li)-ion batteries (LIBs) have been widely adopted as the power of choice for small electronic devices through to large power systems such as hybrid electric vehicles (HEVs) or electric vehicles (EVs). However, it falls short of meeting the demands of new markets in the area of EVS or HEVs due to insufficient energy density, poor rate capability, and low cyclic life. Introduction of porous electrode materials represents one of the most attractive strategies to dramatically enhance battery performance such as capacity, rate capability, cycling life, and safety. In this paper, the applications of porous negative electrodes for rechargeable lithium-ion batteries and properties of porous structure have been reviewed. Porous carbon with other anode materials and metal oxide’s reaction mechanisms also have been elaborated. The purpose of this review is to give a broad overview of the recent scientific researches and developments of porous negative electrodes and indicate future trends in anode development of porous materials as a replacement for graphite in LIBs.

Tribological behaviour and lubrication performance of hexagonal boron nitride (h-BN) as a replacement for graphite in aluminium forming

In metal-forming processes friction leads to the generation of heat, adhesion and the pick-up of work material, tool wear, inhomogeneous deformations, defects and a poor surface quality. Therefore, the use of suitable lubricants is required, especially in the case of aluminium and aluminium alloys. With the increased complexity of the parts being formed, higher strength requirements and the introduction of new alloys, the forming lubricants are also being subjected to ever-increasing demands in terms of temperature stability, reduced friction, galling prevention and surface protection. Graphite is a well-known, solid lubricant that is successfully used in the cold and hot forming of aluminium. However, it leaves dark stains on the surface of the formed part, which means that additional grinding or polishing is required. One of the possible substitutes for graphite is hexagonal boron nitride (h-BN), also known as white graphite.In this work the possibility of replacing graphite with h-BN in Al-forming lubricants was investigated, including the influence of h-BN powder size and concentration on its tribological performance and the aluminium’s surface quality. The results of the investigation show that h-BN, as a solid lubricant, is capable of successfully replacing graphite in Al-forming processes, while at the same time maintaining a clean surface without staining. The study has shown that the tribological performance, including the friction and wear, the lubrication-film stability and the surface quality, very much depend on the powder size and the concentration. Under the investigated contact conditions, the best performance was obtained for 30-µm h-BN powder when added to the grease in a concentration between 10 and 20%.

Tin-based materials as negative electrodes for Li-ion batteries: Combinatorial approaches and mechanical methods

Graphite has been used as the negative electrode in lithium-ion batteries for more than a decade. To attain higher energy density batteries, silicon and tin, which can alloy reversibly with lithium, have been considered as a replacement for graphite. However, the volume expansion of these metal elements upon lithiation can result in poor capacity retention. Alloying the active metal element with an inactive material can limit the overall volume expansion and improve cycle life. This paper presents a summary of tin-based materials as negative electrodes. After reviewing attempts to improve and understand the electrochemical behaviour of metallic tin and its oxides, the focus turns to alloys of tin with a transition metal (TM) and, optionally, carbon. To do so, a combinatorial sputtering technique was used to simultaneously prepare many different compositions of Sn-TM-based materials. The structural and electrochemical results of these samples are presented and they show that cobalt is the preferred TM to give optimal performance. Finally, a comparison of a Sn–Co–C negative electrode material prepared by a rapid quenching method (sputtering) with a material prepared by an economical milling method (mechanical attrition) is presented and discussed. Copyright © 2010 John Wiley & Sons, Ltd.

Tungsten as first wall material in fusion devices

The observation in JET of co-deposition of tritium with carbon has led to a broad discussion on the replacement of graphite by a high- Z material for the first wall coverage. Moreover, due to the high erosion rate, carbon plasma facing components (PFCs) appear to be unacceptable for a commercial fusion reactor. Research in this area has subsequently gained increased attention. This paper describes the status of investigations on the use of tungsten as a first wall material. It discusses on the physical side the plasma wall interaction, the transport of tungsten in the plasma boundary and in the core. As an intermediate step on the technological side, graphite is often coated with tungsten layers. For highly loaded surfaces in a fusion reactor finally bulk tungsten components will have to be developed.