Inactive Material Research Articles

About the Consideration of the Inactive Materials and the Meshing Procedures in Computational Models of Lithium Ion Battery Electrodes

AbstractLithium‐ion batteries (LIBs) constitute a crucial technology in the ongoing energy transition. Still, the composite porous electrodes in LIBs remain complex systems which still need optimization to meet the requirements from the applications, e. g., high energy density for the automotive sector. To achieve well‐designed LIB electrodes, computational continuum modeling with three‐dimensional (3D) resolution constitutes a powerful tool to gain insights on the working principles of these electrodes. However, due to the complexity of the material properties and geometrical features within the electrodes, until mid‐2010’s such type of models had to make numerous assumptions, especially regarding the carbon additive and binder (all together standing for the so called inactive phase), that was not explicitly resolved in 3D. Recently, the battery modeling field has undergone tremendous progress which allowed the emergence of a new generation of models, more accurate and realistic than ever before. This review presents the latest developments through the prism of the consideration of the inactive phase in these models, and also provides recommendations on how to design modeling studies in order to minimize numerical errors originated by the meshing procedures of the materials and electrode volumes, a crucial step when a continuum model is set.

Practical Approaches to Apply Ultra-Thick Graphite Anode to High-Energy Lithium-Ion Battery: Carbonization and 3-Dimensionalization.

Lithium-ion batteries with ultra-thick electrodes have high energy density and low manufacturing costs because of the reduction of the inactive materials in the same battery volume. However, the partial usage of the full capacity and the low rate capability are caused by poor ionic and electronic conduction. In this work, the effects of two approaches, such as electrode binder carbonization by heat treatment and 3-dimensionalization by the laser structuring of ultra-thick graphite anodes to lithium-ion batteries for high energy density, are investigated. During the heat treatment, the polyvinylidene fluoride (PVDF) binder is carbonized to form fluorinated graphitic carbons, thereby increasing the number of lithium-ion storage sites and the improvement of the electrode capacity by 14% (420 mAh g−1 and 20 mAh cm−2). Further, the carbonization improves the rate capability by 31% at 0.1 C by simultaneously reducing the ionic and electronic resistances. Furthermore, after the laser structuring of the carbonized electrode, the areal discharge capacity increases to 50% at the increasing current rates, resulting from drastically improved ionic conduction. In addition to the electrochemical characteristics, these two approaches contribute considerably to the fast wetting of the electrolyte into the ultra-thick electrode. The carbonization and laser structuring of the ultra-thick graphite anodes are practical approaches for high-energy batteries to overcome the thickness limitation.

Regulating the Polarization of Lithium Metal Anode via Active and Inactive 3D Conductive Mesh Structure

Lithium is spotlighted as the next‐generation battery anode owing to its low potential and high theoretical capacity. However, the volume changes and dendrite issues hinder its practical use as an anode material. Several metallic protective layers are used to overcome these problems. However, a comprehensive understanding of the material properties and structure of protective layers within an electric field is required to determine their suitability as protective layers. Herein, the reactivity with the Li of copper and stainless steel (SS) meshes within the electric field is compared, which are active and inactive protective layers, respectively. As inactive materials do not influence the Li‐ion chemistry, the protective layer minimizes Li consumption. These characteristics lead to reducing the anodic polarization because of stable solid electrolyte interface (SEI) layer formation and effective utilization of the host space. A Li–Li symmetric cell configuration containing SS mesh as a protective layer exhibits stable cycling performance with a low overpotential (20 mV) for over 800 h at a current density of 1 mA cm−2. Furthermore, the SS mesh inhibits the galvanic corrosion between the Li metal anode and mesh layer because of its low reactivity with lithium.

Structural and Electrochemical Analysis of Thick Laser Patterned Electrodes for Fast Charging Batteries

For widespread adoption of electric vehicles, lithium-ion batteries need to achieve energy densities of around 350 Wh/kg, cost less than $100/Wh, and be able to charge quickly within 15 minutes. The production of most inactive materials within modern Li-ion cells (e.g. separator, current collector, packaging) have already undergone tremendous optimization but many opportunities remain for improving the performance of the electrodes and reducing the cost and time of wetting, formation and aging processes. By increasing the thickness of electrodes clear opportunities exist for enhancing the energy densities of conventional cell materials and reducing cost. For example, doubling the thickness of electrodes in full cells from 50 μm to 100 μm can increase the energy density of the cell by about 16% and reduce the cost of the cell by 50% (from $249/kWh to $172/kWh)1. These benefits arise from increasing the ratio of electrode active material to inactive material within cells; however, increased thickness is often accompanied by reduced rate performance and increasingly difficult electrolyte wetting and formation processes due to the challenge of infiltrating the electrode pore structure with electrolyte and displacing gases during formation2. One emerging electrode processing technology involves the laser-ablation of small micro pores or channels into Li-ion battery electrodes to enhance their electrolyte wetting and rate performance. Pulsed lasers are increasingly being used in advanced manufacturing processes due to their ability to weld, sinter, or remove materials quickly and with very high precision. When applied to high energy density thick electrodes, micro-structuring by laser patterning has been shown to improve the rate capabilities of cells while maintaining high capacity retention3. These laser ablated pores or channels provide low tortuosity paths for lithium ions to reach deeper regions in the thick electrodes more quickly than before, limiting concentration gradients and thus reducing unwanted lithium plating at elevated rates. Despite these benefits, the utilization of ultrafast lasing ablation systems as an in-line technique to selectively remove patterned regions of active material from lithium-ion battery electrodes during production has not yet been widely adopted by the industry. In this work, we identify and manufacture laser-ablated 3D electrode architectures for enhanced Li+ transport and electrochemical performance with the hope of inspiring confidence in the benefits, practicality and cost effectiveness of the laser patterning technique. Preliminary modelling work at NREL has explored the limitations of planar electrodes for fast charge performance and the importance of microscale features for improving ion-transport4-8. With the correct pore/channel geometry, the energy density of ablated electrodes can be significantly improved compared to traditional architectures. We have combined simulation models and experimental data to optimize the 3-D laser patterning of our electrodes. Modelling elucidated the electrodes baseline transport limitations and quickly identified the most promising electrode architectures for favorable cost, energy- and power-density. Next, we used our benchtop ultrafast femtosecond laser ablation system to pattern our thick (ca. 100 µm) electrodes. After processing, the electrodes were inspected using cross-section scanning electron microscopy (SEM) so that ablation parameters such as laser wavelength, power and repetition rate could be optimized and distributions of feature sizes could be identified giving insight into the limitations of the laser system. We observed that the anode and cathode materials responded significantly different to the laser ablation process and that this must be considered during electrode preparation. Next, scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and x-ray diffraction (XRD) were used to probe for local chemical or structural changes in the electrodes’ with patterning to determine if the remaining active materials experienced permanent laser-induced damages. Once successful achievement of the target electrode architecture was confirmed, the benefits of the achieved 3-D patterning were investigated by cycling the electrodes in full cell coin cells and comparing their performance against standard cells with unmodified electrodes (benchmark). Cycling data clearly shows improved rate performance and capacity retention derived from the patterning of the thick graphite and NMC electrodes. Direct structuring of the electrodes has improved their ion transport and reduced lithium concentration gradients (cell polarization) resulting in high specific energy- and high power-density. While clear evidence of rapid lithium plating was observed in the standard benchmark cells at rates exceeding 1C, this has been largely mitigated in the laser ablated electrodes. Lastly, we probed the wetting of these electrodes with electrochemical impedance spectroscopy to map in real time the improved rate and extent of wetting achieved through the adoption of our 3-D laser patterns. Achieving shorter wetting times will correspond to reductions in cell manufacturing costs and is expected to present a significant market advantage. Figure 1

(Invited, Digital Presentation) Zinc-Based Energy Storage System Deployments and Developments for Transition to a Clean Energy Future

Rechargeable zinc-based alkaline batteries are an attractive electrochemical energy storage option with zinc anode costs of $3/kWh at full (theoretical) 2 electron capacity. When paired with high-capacity, inexpensive cathodes like manganese dioxide, and accounting for incomplete utilization of the active materials capacities, inactive materials costs (like for current collectors etc.) and manufacturing costs, rechargeable zinc-manganese dioxide batteries costing about $20-30/kWh appear to be within reach. The challenges to meeting these cost targets, and the current status of such rechargeable zinc alkaline batteries will be discussed. The first generation of rechargeable zinc-manganese dioxide batteries are now being deployed in residential, commercial, and utility-scale energy storage applications. In some cases, the applications require several thousand cells to meet the power and capacity requirements. Even such large systems do not require battery management systems at the cell level, being remarkably resilient to overcharging, without flammability and thermal runaway issues, and passing UL 9540A certification requirements without any protective measures being necessary. However, operation of these early deployments, indicate that to optimize systems performance and durability, energy management systems to manage overall systems charge-discharge protocols, taking the specific cell electrochemical characteristics, are desirable. The lessons learned and desirable innovations in designing and managing such large assemblies of cells will also be discussed.

(Digital Presentation) Understanding the Impact of Process Conditions on Manufacturing Thick Cathodes By Systematically Reducing Inactive Material Percentages

With the lithium-ion battery industry moving to high energy density anode materials such as silicon and lithium metal as a substitute for lower specific capacity carbon-based materials like graphite, cathode energy density can become a bottleneck. Typical cathodes have less than 10% practical specific capacity compared to both pure lithium metal and silicon. For these anodes, cathodes with higher active material loadings per unit area would be needed to produce matching electrode pairs. However, cathode thickness cannot indefinitely be increased, as doing so leads to issues with electrolyte transportation, conductivity, and mechanical properties [1,2].Increasing the loading of the cathode could also be done by reducing the amounts of inactive components, such as the binder and the conductive additive, in the electrode. To achieve this, understanding the role of each component is important. The most important role of the binder is to act as an adhesive among particles and the current collector. But most binders are electronically insulating. The main role of the conductive additive, such as carbon black, is to improve the conductivity of the overall system [1].As the inactive material percentages are decreased, the distribution of these components in the electrode domain becomes more important to both the electrochemical and mechanical performance of the electrode. The distribution changes with the different process conditions used, such as mixing techniques, order, speeds, times, slurry viscosity, drying conditions, etc. This research consists of a systematic study to understand the effects of the aforementioned process conditions on the particle and polymer distribution as well as its contribution to the mechanical and electrochemical performance. With the use of the current findings, the active material percentage was increased up to 98% in electrodes with 5 mAh/cm2 loading, retaining similar performance to electrodes with 92.8% active material, as shown in figure 1. Some contribution of the capacity fade was found to be due to the lithium counter electrode used.The goal of this ongoing project is to produce a model that could be applied to different materials to identify the best process conditions for thick electrode manufacturing.References F. Ma, Y. Fu, V. Battaglia, R. Prasher, Microrheological modeling of lithium-ion battery anode slurry, J. Power Sources, 438 (2019), p. 226994Wen Yu, Nanping Deng, Lin Tang, Kewei Cheng, Bowen Cheng, Weimin Kang, Roles of metal element substitutions from the bimetallic solid-state electrolytes in lithium batteries, Particuology, 65 (2022), p. 51-71 Figure 1

Inhomogeneous degradation induced by lithium plating in a large-format lithium-ion battery

With the demand for high-energy-density power sources for electric vehicles, large-format lithium-ion batteries are widely applied, considering their advantages in reducing the weight of inactive materials. However, large-format cells suffer from internal inhomogeneities, which become the bottleneck limiting their performance. Here, the inhomogeneous degradation in a large-format pouch cell is comprehensively investigated using a series of (non-)destructive techniques. Spatial-resolved deformation detection and ultrasonic diagnostics are utilized to study the evolution of inhomogeneity inside the large-format battery. Localized deformation and deposits are found to firstly appear at the tab-near regions and then propagate into central regions, which is identified by characterization tests to be induced by lithium plating. The inhomogeneous degradation mechanism inside the battery is summarized as an initiation-propagation process. During the process, lithium deposit is initiated by a local high current density, resulting in the local separator pore closure. Pore closure in the separator in return creates a high current density and overpotential in the adjacent area, leading to a continuous propagation of the lithium deposition area. Finally, an effective indicator—peak height in the differential voltage curve is proposed to detect the inhomogeneity in the battery, and thus offers guidance to the design and management of large-format cells.

Toxicity of the polymeric excipients in geriatric polypharmacy

Geriatric polypharmacy is already a complicated issue in pharmacotherapy as multiple biological and pharmaceutical factors are involved. Given the fact that the geriatric population, in general, takes more than five medications for multiple diseases and most likely takes several supplements, there is a hidden issue with the types and amounts of the pharmaceutical inactive ingredients (polymers in particular) as they, as well as their impurities, may build up in an ill-performing body beyond their safety levels. In this commentary, we impart on biological factors, the importance of polymers, and the types and amounts of the impurities within each polymeric excipient that can potentially lead to severe pharmacological and biological impacts. Given the complex safety and toxicity issues in polypharmacy, we may need to revisit the safety standards and regulations on the inactive materials that are widely used in geriatric medications.

Application of Poly-L-Lysine for Tailoring Graphene Oxide Mediated Contact Formation between Lithium Titanium Oxide LTO Surfaces for Batteries.

When producing stable electrodes, polymeric binders are highly functional materials that are effective in dispersing lithium-based oxides such as Li4Ti5O12 (LTO) and carbon-based materials and establishing the conductivity of the multiphase composites. Nowadays, binders such as polyvinylidene fluoride (PVDF) are used, requiring dedicated recycling strategies due to their low biodegradability and use of toxic solvents to dissolve it. Better structuring of the carbon layers and a low amount of binder could reduce the number of inactive materials in the electrode. In this study, we use computational and experimental methods to explore the use of the poly amino acid poly-L-lysine (PLL) as a novel biodegradable binder that is placed directly between nanostructured LTO and reduced graphene oxide. Density functional theory (DFT) calculations allowed us to determine that the (111) surface is the most stable LTO surface exposed to lysine. We performed Kubo–Greenwood electrical conductivity (KGEC) calculations to determine the electrical conductivity values for the hybrid LTO–lysine–rGO system. We found that the presence of the lysine-based binder at the interface increased the conductivity of the interface by four-fold relative to LTO–rGO in a lysine monolayer configuration, while two-stack lysine molecules resulted in 0.3-fold (in the plane orientation) and 0.26-fold (out of plane orientation) increases. These outcomes suggest that monolayers of lysine would specifically favor the conductivity. Experimentally, the assembly of graphene oxide on poly-L-lysine-TiO2 with sputter-deposited titania as a smooth and hydrophilic model substrate was investigated using a layer-by-layer (LBL) approach to realize the required composite morphology. Characterization techniques such as X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), Kelvin probe force microscopy (KPFM), scanning electron microscopy (SEM) were used to characterize the formed layers. Our experimental results show that thin layers of rGO were assembled on the TiO2 using PLL. Furthermore, the PLL adsorbates decrease the work function difference between the rGO- and the non-rGO-coated surface and increased the specific discharge capacity of the LTO–rGO composite material. Further experimental studies are necessary to determine the influence of the PLL for aspects such as the solid electrolyte interface, dendrite formation, and crack formation.

Exceptional points and pseudo-Hermiticity in real potential scattering

We employ a recently-developed transfer-matrix formulation of scattering theory in two dimensions to study a class of scattering setups modeled by real potentials. The transfer matrix for these potentials is related to the time-evolution operator for an associated pseudo-Hermitian Hamiltonian operator \widehat{\mathbf{H}}𝐇̂ which develops an exceptional point for a discrete set of incident wavenumbers. We use the spectral properties of this operator to determine the transfer matrix of these potentials and solve their scattering problem. We apply our general results to explore the scattering of waves by a waveguide of finite length in two dimensions, where the source of the incident wave and the detectors measuring the scattered wave are positioned at spatial infinities while the interior of the waveguide, which is filled with an inactive material, forms a finite rectangular region of the space. The study of this model allows us to elucidate the physical meaning and implications of the presence of the real and complex eigenvalues of \widehat{\mathbf{H}}𝐇̂ and its exceptional points. Our results reveal the relevance of the concepts of pseudo-Hermitian operator and exceptional point in the standard quantum mechanics of closed systems where the potentials are required to be real.

An efficient and versatile biopolishing strategy to construct high performance zinc anode

Conventional strategies for highly reversible Zn anodes usually involve complex and time-consuming production processes of current collectors, expensive and toxic electrolyte additives, or the introduction of inactive materials in protective layer. Here, we develop a fast, facile, and environmentally friendly biopolishing method to prepare dendrite-free Zn anodes, which merely involves the simple immersion of Zn foil in a biocompatible cysteine aqueous solution. The ravine structure formed by sulfhydryl etching for 30 min not only increases the electroactive area of Zn anode but also regulates the distribution of electric field and Zn ions, ensuring the homogeneous deposition and stripping of Zn ions. The biopolished Zn anode can be operated steadily for 2,000 h with a low voltage hysteresis at a current density of 1 mA·cm−2. In addition, Zn anodes with a cycle life of 500 h can be built by soaking for only 5 min, proving the high efficiency of the proposed method. This strategy is generalized to substances with sulfhydryl groups for polishing Zn electrodes with improved performance. The cysteine-polished Zn//activated carbon supercapacitor can stably run for 20,000 cycles without obvious capacity attenuation. The proposed strategy shows potential for producing advanced Zn anodes.

Comprehensive Characterization of Shredded Lithium-Ion Battery Recycling Material.

Herein we report on an analytical study of dry‐shredded lithium‐ion battery (LIB) materials with unknown composition. Samples from an industrial recycling process were analyzed concerning the elemental composition and (organic) compound speciation. Deep understanding of the base material for LIB recycling was obtained by identification and analysis of transition metal stoichiometry, current collector metals, base electrolyte and electrolyte additive residues, aging marker molecules and polymer binder fingerprints. For reversed engineering purposes, the main electrode and electrolyte chemistries were traced back to pristine materials. Furthermore, possible lifetime application and accompanied aging was evaluated based on target analysis on characteristic molecules described in literature. With this, the reported analytics provided precious information for value estimation of the undefined spent batteries and enabled tailored recycling process deliberations. The comprehensive feedstock characterization shown in this work paves the way for targeted process control in LIB recycling processes.

Ultrahigh active material content and highly stable Ni-rich cathode leveraged by oxidative chemical vapor deposition

Despite the huge achievements that have been made in developing lithium-ion batteries, there remain gaps between the existing demands and the current battery performance. As one of the key components, cathode needs to adopt a further enhanced design to realize a high energy density and long useful life battery. Here we report a cathode tailoring strategy, exploiting multi-functional conformal coatings that are mechanically flexible, thickness controllable at the nanometer scale, electronically conductive, and selectively permeable. We demonstrate a gas phase polymerization technique that successfully enhances the energy density and the lifespan of the battery, particularly for a Ni-rich cathode (LiNi0.8Co0.1Mn0.1O2, NCM811). Oxidative chemical vapor deposition (oCVD) yielded an extremely conformal polymer layer of poly (3,4-ethylene dioxythiophene) (PEDOT) that is chemisorbed on both primary and secondary particles in NCM811 with identified S-O bonds. The chemo-physical adhesion between the cathode particles and the highly conductive nature of oCVD PEDOT permit a significant reduction of inactive materials inclusion in the cathode and enable a noticeable high active materials content (up to 99% in weight percentage). ToF-SIMS results identified that the formation of cathode electrolyte interphases, especially between primary particles, has been eliminated in the PEDOT coated sample. As a result, the cathode enabled by multi-functional oCVD PEDOT exhibited much higher capacity retention (about 80% after 300 cycles) compared with the pristine sample (about 6% only after 200 cycles). These results offer a single-step rational cathode design strategy that ensures high-energy density, long-life, and safe lithium-ion batteries.

Aluminum Foil Anodes for Li-Ion Rechargeable Batteries: the Role of Li Solubility within β-LiAl

Lithium-ion battery electrodes contain a substantial amount of electrochemically inactive materials, including binders, conductive agents, and current collectors. These extra components significantly dilute the specific capacity of whole electrodes and thus have led to efforts to utilize foils, for example, Al, as the sole anode material. Interestingly, the literature has many reports of fast degradation of Al electrodes, where less than a dozen cycles can be achieved. However, in some studies, Al anodes demonstrate stable cycling life with several hundred cycles. In this work, we present a successful pathway for enabling long-term cycling of simple Al foil anodes: the β-LiAl phase grown from Al foil (α-Al) exhibits a cycling life of 500 cycles with a ∼96% capacity retention when paired with a commercial cathode. The excellent performance stems from strategic utilization of the Li solubility range of β-LiAl that can be (de-)lithiated without altering its crystal structure. This solubility range at room temperature is determined to be ∼6 at %. Consequently, this design circumvents the critical issues associated with the α/β/α phase transformations, such as volume change, mechanical strain, and formation of nanopores. Application-wise, the maturity of the aluminum industry, combined with excellent sustainability prospects, makes this anode an important option for future devices.

Aluminum Doping and Nanostructuring Enabled Designing of Magnetically Recoverable Hexaferrite Catalysts.

We demonstrate an approach based on substituting a magnetic cation with a carefully chosen isovalent non-magnetic cation to derive catalytic activity from otherwise catalytically inactive magnetic materials. Using the model system considered, the results illustratively present that the catalytically inactive but highly magnetic strontium hexaferrite (SrFe12O19; SFO) system can be transformed into a catalytically active system by simply replacing some of the magnetic cation Fe3+ by a non-magnetic cation Al3+ in the octahedral coordination environment in the SFO nanocrystals. The intrinsic SFO and Al-doped SrFe12O19 (SrFe11.5Al0.5O19; Al–SFO) nanomaterials were synthesized using a simple, eco-friendly tartrate-gel technique, followed by thermal annealing at 850 °C for 2 h. The SFO and Al–SFO were thoroughly characterized for their structure, phase, morphology, chemical bonding, and magnetic characteristics using X-ray diffraction, Fourier-transform infrared spectroscopy, and vibrating sample magnetometry techniques. Catalytic performance evaluated toward 4-nitrophenol, which is the toxic contaminant at pharmaceutical industries, reduction reaction using NaBH4 (mild reducing agent), the Al-doped SFO samples exhibit a reasonably good performance compared to intrinsic SFO. The results indicate that the catalytic activity of Al–SFO is due to Al-ions occupying the octahedral sites of the hexaferrite lattice; as these sites are on the surface of the catalyst, they facilitate electron transfer. Furthermore, surface/interface characteristics of nanocrystalline Al–SFO coupled with magnetic properties facilitate the catalyst recovery by simple, inexpensive methods while readily allowing the reusability. Moreover, the activity remains the same even after five successive cycles of experiments. Deriving the catalytic activity from otherwise inactive compounds as demonstrated in the optimized, engineered nanoarchitecture of Al-doped-Sr-hexaferrite may be useful in adopting the approach in exploring further options and designing inexpensive and recyclable catalytic materials for future energy and environmental technologies.

Recycling of Lithium‐Ion Batteries—Current State of the Art, Circular Economy, and Next Generation Recycling

AbstractBeing successfully introduced into the market only 30 years ago, lithium‐ion batteries have become state‐of‐the‐art power sources for portable electronic devices and the most promising candidate for energy storage in stationary or electric vehicle applications. This widespread use in a multitude of industrial and private applications leads to the need for recycling and reutilization of their constituent components. Improving the “recycling technology” of lithium ion batteries is a continuous effort and recycling is far from maturity today. The complexity of lithium ion batteries with varying active and inactive material chemistries interferes with the desire to establish one robust recycling procedure for all kinds of lithium ion batteries. Therefore, the current state of the art needs to be analyzed, improved, and adapted for the coming cell chemistries and components. This paper provides an overview of regulations and new battery directive demands. It covers current practices in material collection, sorting, transportation, handling, and recycling. Future generations of batteries will further increase the diversity of cell chemistry and components. Therefore, this paper presents predictions related to the challenges of future battery recycling with regard to battery materials and chemical composition, and discusses future approaches to battery recycling.

Lithium Silicates in Anode Materials for Li-Ion and Li Metal Batteries

The structural and interfacial stability of silicon-based and lithium metal anode materials is essential to their battery performance. Scientists are looking for a better inactive material to buffer strong volume change and suppress unwanted surface reactions of these anodes during cycling. Lithium silicates formed in situ during the formation cycle of silicon monoxide anode not only manage anode swelling but also avoid undesired interfacial interactions, contributing to the successful commercialization of silicon monoxide anode materials. Additionally, lithium silicates have been further utilized in the design of advanced silicon and lithium metal anodes, and the results have shown significant promise in the past few years. In this review article, we summarize the structures, electrochemical properties, and formation conditions of lithium silicates. Their applications in advanced silicon and lithium metal anode materials are also introduced.

Influence of weight ratio of conductive additive to binder in an electrode on the capacity of Li-ion battery

Changes in the charge and discharge capacity of a lithium-ion battery are investigated by varying the percentage weight composition ratios of conductive additive to polymeric binder in an electrode of a lithium-ion battery. The cathode is made of active material (LiMn2O4), binder (PVDF), and conductive additive (carbon black). To investigate the effect of inactive material composition on battery performance experimentally, the weight percentage of active material in the cathode is fixed at 85 wt% and five different ratios of PVDF/carbon black are assessed by varying conductive additive from 1.5 wt% to 13.5 wt% and binder from 13.5 wt% to 1.5 wt% while fabricating lithium-ion batteries. To study particles' cohesive behaviours between inactive materials in the electrode, various SEM images are taken and analysed for five different compositions of carbon black and PVDF. As a result, the improved battery performance is observed at the ratios of 7.5 wt%-10.5 wt% carbon black and 7.5 wt%-4.5 wt% PVDF.

Studies on the effects of basalt fibres on the durability characteristics of high strength self compacting concrete

Basalt is an extrusive volcanic rock, which is easily obtainable. Basalt fibres are called biologically inactive, non-toxic and eco-friendly materials. Using fibres in concrete gives rise to fibre-reinforced concrete which is known to increase the mechanical properties and durability properties of the concrete. In this study the effect on the durability properties of High strength Self Compacting concrete are analysed by subjecting the specimens to an Acidic environment like Hydrochloric acid (HCL), Nitric acid (HNO3) and Sulfuric acid (H2SO4), and in a Base environment like Sodium Hydroxide (NaOH), Sodium Sulphate (Na2SO4), Magnesium Sulphate (MgSO4), in 5% concentration of each, with 3 different aspect ratio viz., 350, 530 and 600, with a dosage of 0.2% by the volume of concrete and then the properties such as mechanical, dimensional stability and mass loss were determined.

Chemo-mechanical model predicted critical SOCs for the mechanical stability of electrode materials in lithium-ion batteries

The electrochemical performance and capacity retention of lithium-ion batteries significantly depend on the structural integrity of electrode materials. Understanding of the mechanical failure mechanisms in the active and inactive material phases of the electrode is critical to predict safe operation conditions, and to design next generation electrodes. The mechanical failure of the electrode can be effectively avoided by tailoring the lithiation kinetics and the size of the active and inactive materials. To predict the critical state of charges (SOCs) for mechanical failures, we develop a fully coupled chemo-mechanical model, and examine the effect of stress–concentration coupling on the maximum stored capacity. We focus on three types of mechanical failures: particle fracture, binder yielding, and debonding at the particle–binder interface. The simulations show that the medium-sized particles achieve larger capacity with no mechanical failure. Moreover, the simulation results reveal that as the binder modulus and charge rates increase, the safe zone shrinks considerably, while the binder thickness imposes no significant effect. These findings provide a fundamental insight into providing optimized charging protocols for minimum capacity retention due to mechanical failures at the electrode.