As lithium-ion batteries (LIBs) face growing demands for sustainability and resource efficiency, Cu-free, lightweight current collectors have become increasingly important. Ni and Al metal thin films (<= 1 mu m), deposited onto polymer substrates via electron beam evaporation, were investigated as alternatives to conventional Cu and Al foils. Prototype LIBs employing these thin-film collectors demonstrated a stable electrochemical performance, confirming their practical feasibility. Characterization using sheet resistance measurements, scanning electron microscopy, and electrochemical impedance spectroscopy revealed an increase in interfacial resistance, which was attributed to a decreased electrical conductivity and weakened adhesion arising from the surface characteristics of the thin-film current collectors. Nevertheless, the observed reduction in discharge rate performance remained within an acceptable range. Peel strength tests and ultrasonic delamination experiments further indicated the markedly enhanced separability of electrode composites, particularly in Al-based thin films. These findings demonstrated a rational design trade-off: a moderate reduction in electrical performance was balanced by significant gains in the gravimetric energy density, material efficiency, and recyclability. Overall, metal thin-film current collectors represent a promising strategy for advancing sustainable and resource-conscious LIB technologies.

The cost benefits of recycling graphite electrodes are low; therefore, studies are few on graphite electrode recycling despite the need for lithium-ion battery electrode recycling in achieving efficient carbon neutrality. Here, we investigated the physical properties and battery performance of a composite material exfoliated from a foil during battery production. The surfaces of the exfoliated graphite particles contained binder components, which decreased the charge/discharge capacity and increased the charge-transfer resistance (R ct) of the material. The binder content had a significant effect on the R ct, and carboxymethyl cellulose was more sensitive to an increase in the R ct than styrene-butadiene rubber. When the exfoliated graphite composite was heat-treated, the binder components were removed, and the surface of the graphite particles was modified. The higher the heat treatment temperature, the lower the R ct; after heat treatment at 600 degrees C, the R ct was 45% lower than that of pristine graphite. In contrast, the cycle durability of exfoliated graphite treated at 600 degrees C was reduced due to the exposure of excessively active graphite surfaces. Heat treatment at intermediate temperature (450 degrees C) provided the graphite surface structure whereby both R ct reduction and durability could be achieved.

The combination of scanning electron microscopy (SEM) images and energy-dispersive X-ray spectroscopy (EDS) maps (SEM-EDS analysis) enables the analysis of the relationship between the microstructures and elemental compositions of the surfaces of materials. However, conventional SEM-EDS analyses lack comprehensiveness and quantitativeness, resulting in potential inaccuracies in reflecting the properties of the entire sample and variations in the results depending on the analyst. Therefore, herein, we propose an objective SEM-EDS analytical process that addresses the aforementioned issues. Comprehensiveness was addressed by acquiring large volumes of SEM images through automated capturing, whereas quantitativeness was addressed through microstructural analysis of the SEM images based on image features, model-based dimension reduction and clustering methods, and similarity analysis of the elemental distribution in EDS maps based on statistical distances. The proposed method was used to analyze the degradation of lithium-ion battery electrodes, affording objective results that align with subjective insights into the changes in the morphology and composition of solid electrolyte interphase (SEI) films accompanying degradation.

The edge plane exposed on the surface of carbon materials is the active site that determines their properties. When graphite is used as the negative electrode in lithium-ion batteries, the edge plane acts as an access point for lithium insertion/desorption. However, because of the low specific surface area and amorphous carbon coating of graphite particles, accurately estimating the number of edge planes is challenging. Therefore, we propose a technique for determining graphite edge planes based on the stepwise adsorption of Kr onto the hexagonal carbon network surface. Graphite particles with highly modified surface structures were prepared by controlling the particle size, heat treatment temperature, and amorphous carbon coating. Electrochemical evaluation revealed significant differences in charge-transfer resistance, an indicator of edge planes. The edge plane determination results obtained using conventional methods such as X-ray diffractometry and Raman spectroscopy did not correlate well with charge-transfer resistance. Meanwhile, Kr adsorption measurements revealed that the stepwise adsorption behavior, because of the interaction of Kr with the energetically homogenous surface, varied significantly depending on the surface properties of graphite particles. The number of edge planes estimated by gas adsorption strongly correlated with charge-transfer resistance. Consequently, we determined that the graphite edge plane tied to the electrochemical index can be derived using gas adsorption analysis. This edge plane determination technique would be applicable not only to graphite but also to highly crystalline carbon materials with an exposed hexagonal carbon network surface.

Coaxial-fibers bundled batteries in which the negative electrode made of carbon fibers, separator and positive electrode are formed in this order from the inside are proposed to be used as a framework and power source for the future applications.

Lithium-ion batteries use spheroidized graphite coated with amorphous carbon as the negative electrode material. In this study, we measured the physical properties of spheroidized graphite with varying amounts of an amorphous carbon coating to elucidate its effect on the battery performance. To this end, electrochemical evaluation and surface analysis of the graphite electrode were performed. The specific surface area was significantly reduced by the amorphous carbon coating because the pores, including the surface inside the spheroidized graphite particles, were occluded by the coating layer. By contrast, the capacitance at the graphite electrode/electrolyte interface did not correspond to the specific surface area, indicating that the amorphous carbon coating served as an edge plane. Consequently, efficiency at the initial charging-discharging cycle was improved, inducing a reduction in the charge-transfer resistance of lithium insertion/desorption. The solid electrolyte interphase formed on graphite was homogenized by the amorphous carbon coating, and the thickness was significantly reduced. The amorphous carbon coating suppressed the reductive decomposition of the electrolyte and increased the number of active sites for lithium insertion/desorption by reducing the number of bare overactive edges present on the surface of the spheroidized graphite particles. The results confirm that the design of an amorphous carbon coating that suppresses the overactivity of the edge during the reductive decomposition of electrolyte components while increasing the active points for lithium insertion and desorption is crucial for enhanced battery performance.

Lithium-ion batteries experience complex reactions between the electrodes and the electrolyte under nonstandard conditions. Investigating these reactions is crucial for ensuring battery durability and safety. In this study, we develop an electrochemical cell capable of controlled overcharging and temperature regulation between 30 and 100 degrees C. The charge-discharge performance of the cell is evaluated after overcharging. By utilizing synchrotron radiation for X-ray diffraction and absorption fine structure analysis, we track the electronic state of the positive electrode and the crystal structure of the negative electrode during heated overcharging. Our results reveal increased side reactions in the positive electrode at higher temperatures during overcharging, while the negative electrode displays a gradual increase in side reactions in the normal charge-discharge region with increasing temperature. Specifically, at 100 degrees C, side reactions in the overcharging regions consume 86.5% and 66.1% of the current at the positive and negative electrodes, respectively. These side reactions are induced by the electrolyte oxidative decomposition at the positive electrode. Moreover, they initiate Joule heating during battery overcharging, promoting side reactions and leading to exothermic reactions between the electrodes and electrolyte.

Disordered rock‐salt (DRS) type active materials are highly significant because of their large reversible capacities, which are due to their unique Li + diffusion pathway and the redox capabilities of cationic transition metals (TMs) and anionic O ions. Loosely crystalline DRS materials have weak covalent bonds between TMs and O, increasing the O redox contribution and thereby enhancing their capacities. In this study, Mn‐based positive electrode materials with DRS structures are activated and stabilized by mechanochemical doping of nonmetallic elements P and B into interstitial sites. Synthesized Li 0.90 Mn 0.84 P 0.04 O 2 (LMPO5) exhibits an initial discharge capacity of 346 mAh g −1 (1050 Wh kg −1 ) during charging/discharging. Li 0.91 Mn 0.83 B 0.10 O 2 (LMBO5) has a moderately expanded lattice size, which facilitates high‐capacity retention during cycling (≈284 mAh g −1 at the 30th cycle). The structural properties of the synthesized active materials are extensively characterized. By introducing nonmetallic elements into the interstitial sites of Mn‐based materials, inexpensive, high‐capacity, and long‐cycling/calendar‐life Co/Ni‐free monometallic positive electrode materials may be further developed.

Limiting the metal species present in the battery, such as the metal foils used for current collection, is an effective strategy to reduce the cost of recycling lithium-ion batteries (LIBs). This study elucidates the performances of LIBs without metal foils by investigating LIBs using self-standing electrodes with an edge or full contact at the current terminals. Although the Cu foil on the negative electrode had little effect on battery performance, the Al foil on the positive electrode was critical in determining the characteristics of the battery, especially its rate properties. The low electronic conductivity of the positive electrode resulted in the localization of the reaction area at the electrode edge, as predicted by simulations. The rate characteristics were significantly improved by inserting a non-metallic graphite sheet into the back of the positive electrode. Thus, LIBs without metal foils can be obtained by ensuring the electrical resistance of the positive electrode.

Spinel-related 5 V positive electrode materials LiNi1/2Mn3/2O4 (LNMO), Fe-Ti-co-doped LNMO (LNMO-FT), and LiCoMnO4 (LCMO) were prepared, and their reaction kinetics were examined by a galvanostatic intermittent titration technique (GITT) measurement to understand the factors affecting the reaction kinetics for enhancing the power capability and the energy density. X-ray diffraction (XRD), Raman, and X-ray absorption near-edge structure (XANES) measurements of LNMO-FT indicate that Fe3+ and Ti4+ ions are substituted for Ni and Mn ions and the transition metal ions are randomly distributed at the 16(d) sites in a space group symmetry of Fd3 lithium insertion/extraction process of LNMO proceeds in two-phase reactions, and LNMO-FT exhibits single-phase reactions with two-phase ones in a limited region. Single-phase reactions of these materials give smaller polarizations associated with mass transfer by the GITT than those of two-phase ones, and there is one-to-one correspondence between the polarization increase and the state of charge (SOC) at which the two-phase reaction proceeds. LCMO, which proceeds in a single-phase reaction, gives small and moderate polarizations throughout the charge and discharge operations. Basic functions and energy densities of spinel-related 5 V materials are compared with those of layered materials. The operating voltage of 4.7 V, which is lower than 5 V, and the highly crystallized octahedral primary particles for LNMO-FT are appropriate for high-voltage stability in nonaqueous electrolytes. All-solid-state lithium-ion batteries may enable us to introduce LCMO because of the small change in the lattice parameter of about 0.7% during the operation and the high operating voltage of above 5 V. Although the energy densities of LNMO-FT and LCMO of 598 and 618 Wh kg-1, respectively, in lithium cells are lower than those of layered materials, the single-phase reactions of spinel-related materials are for the and the m. The

Coating graphite negative electrodes of lithium-ion batteries with amorphous carbon layer can significantly improve the battery performance. We investigated the effect of amorphous carbon coating on the formation of a solid electrolyte interphase (SEI) on the graphite surface by performing gas adsorption measurements, surface analysis, and electrochemical impedance measurements. The specific surface area of graphite particles uniformly coated with amorphous carbon is reduced by almost a factor of two, and the irreversible capacity at the first charge/discharge cycle significantly decreases. The SEI film consists of LiF in particulate and O-based coating uniformly distributed at the edges. Hence, the amorphous carbon coating increases the amounts of F and O atoms on the SEI surface and reduces capacitance C ' and the Faraday current at high temperatures. Although the C ' value decreases by approximately 80% after SEI formation, the graphite electrode with an amorphous carbon coating exhibits enhanced C' retention properties. Because the frequency and temperature dependences of the electrode capacitance are strongly affected by the amorphous carbon coating, an electric double layer is likely formed at the graphite/SEI interface. The difference in capacitive behavior can be attributed to the activity of Li insertion/desorption reaction and capacity fading during storage at elevated temperatures.

Manganese (Mn)-based positive electrode materials have attracted significant attention because of their low-risk resources, high valence ranges, and their ability to form polymorphs. Loose-crystalline rock-salt LiMnO2 (LCRSLMO) synthesized via a mechanochemical method exhibited a capacity of ca. 190 mAh g-1 with a potential range of 5.0?2.0 V. The potential curve of LCRS-LMO after 11 charge/discharge cycles exhibited a characteristic 4 V signal, which is similar to the 4 V plateau observed in the transition from layered LiMnO2 or orthorhombic LiMnO2 to the spinel Li-Mn oxide. However, no diffraction peaks corresponding to a spinel-related structure were detected by X-ray diffraction (XRD) measurements of the bulk structure. Furthermore, in situ XRD revealed for the first time that the lattice size of LCRS-LMO approached that of the spinel-related oxide as the charge/ discharge process progressed. The local structural changes of LCRS-LMO examined by in situ X-ray absorption fine structure measurements suggest that the local structure around the manganese ions tends to be aligned toward the spinel-related lattice.

To examine the phase transition upon deintercalation of Li from graphite at elevated temperatures, structural changes in C6Lix (x = 0.284, 0.532, 0.666, 0.739, 0.812) samples during heating were evaluated by in situ X-ray diffraction (XRD) analysis. The diffraction patterns of the sample, in which the stage-1 and the stage-2 structures coexist, drastically converted to the profile of a Li-defect stage-1 structure at temperatures above 200 degrees C without Li intercalation and/or deintercalation. Meanwhile, the reflection peak corresponding to the stage-1 structure in the XRD patterns of C6Li0.812 continuously shifted to higher angles at temperature above 330 degrees C, which implied deintercalation of Li through reaction with the binder and the formation of the Li-defect stage-1 structure. Li deintercalated from C6Lix while maintaining the same stage structure, likely via a solid-state reaction at temperatures above 330 degrees C. The lattice misfit calculated from the difference in interlayer spacing between stage-1 and stage-2 in C6Li0.666 drastically decreased from 4.58% at 50 degrees C to 1.43% at 350 degrees C. These kinetics for Li graphite intercalation compounds at elevated temperatures are formulated for the first time and should be helpful in understanding the Li intercalation/deintercalation mechanism of the graphite electrodes used in Li-ion batteries.

Metallic Li deposited on the anode is known to induce short circuiting and degradation of the charge capacity of Li-ion batteries. However, no reliable technique is currently available to observe such Li metal without removing the case of the battery. An elemental analysis using muonic X-rays is proposed here because of its unique properties of nondestructive measurement, high sensitivity to light elements, and depth resolution. We demonstrated that this technique can be applied to detection of Li deposited on the surface of an anode containing Li ions, using a fully charged anode with Li deposited due to overcharge in an Al-laminated plastic pouch. The basis for the detection method is the difference in the atomic Coulomb capture ratio of the negative muons between the Li metal and ions. We have found, as a result, that the intensity of the muonic X-rays from metallic Li was approximately 50 times higher than that from Li ions. Consequently, the Li metal on the anode was clearly distinguishable from the intercalated Li ions in the anode. Furthermore, measurements of two overcharged anodes with 1.3 and 2.7 mg of metallic Li deposition, respectively, indicated that this technique is suitable for quantitative analysis. Distribution analysis is also possible, as shown by a preliminary observation on an overcharged anode from the back side. Therefore, this technique offers a new approach to the analysis of Li deposited on the anode of a Li-ion pouch battery.

We developed the methods to estimate the average oxidation number of Ni in a nickel oxide from the local structural information on the first nearest neighbor Ni–O shell obtained by extended X-ray absorption fine structure curve fitting analysis. The estimation method utilizes the Jahn-Teller distortion around Ni3+ sites, enabling the evaluation of local structural parameters and mole fractions for different Ni valence states. The average oxidation numbers of Ni in nickel oxides estimated by the methods proposed in this work exhibit good agreement with those reported or evaluated by a conventional method using instrumental and solution chemical analyses. It is demonstrated that the estimation methods also work well in an in situ X-ray absorption spectroscopy (XAS) study on the charge-compensating behavior of Ni in a Ni-containing battery electrode material. The estimation methods are based on Ni K-edge XAS using highly penetrating hard X-ray, and thus applicable to in situ XAS studies. The methods proposed in this work are expected to work as substitutes for the conventional empirical method using X-ray absorption near edge structure. The estimation methods would be important choices when the local environment around Ni could dramatically be changed during charge/discharge cycles, like in an overcharge condition.

We applied a positive muon spin rotation and relaxation (μ+SR) technique to battery materials research by investigating Li diffusion in cathode and electrolyte materials. Recently, we have found th ...

We examined the applicabilities of hard X-ray spectroscopic methods to understand the charge-compensation (CC) behaviors of Ni in a LiNiO2-based positive electrode (PE) material for lithium-ion batteries: Ni K pre-edge high energy resolution fluorescence detection X-ray absorption spectroscopy (XAS) and Ni 1s2p resonant X-ray emission spectroscopy (RXES). Both methods exhibited sequential changes in spectral features with the change in the state of charge of the PE material, similarly to Ni L2,3-edge XAS. This elucidates that these hard X-ray spectroscopic methods can become alternatives to soft X-ray L2,3-edge XAS with the additional ability to measure reactive samples kept in a sealed pouch. Moreover, Ni 1s2p RXES can separate the electronic transition to the unoccupied Ni orbital from those to hybridized orbitals with neighboring atoms by tuning the incident X-ray energy. In this sense, it can provide spectral information reflecting the unoccupied Ni 3d state, which could be a good oxidation-state descriptor. These methods can be done in a usual hard X-ray beamline having an appropriate crystal analyzer. The ability to offer information on the unoccupied 3d state with hard X-ray and the ubiquitous feature of these methods would prompt in situ/operando studies on CC in PE materials for rational materials development.

Trace amounts of edge sites in natural graphite, synthetic graphite and high-temperature treated coke are quantitatively analyzed from the numbers of hydrogen atoms and oxygen-containing functional groups at carbon edge sites. For the analysis of hydrogen content, a new analytical technique is developed. The oxygen-containing functional groups are analyzed with a highly sensitive temperature-programmed desorption (TPD) technique. These techniques allow us to estimate the trace amounts of edge sites in the range of 1 - 10 x 10(-4) at.% with extremely high accuracy and reveal that the concentration and the type of edges sites differ depending on the type and the particle size of these graphitized carbons. Moreover, the average sizes of graphene sheets in these carbons are estimated from the total number of edge sites. The graphene sheet size thus obtained is compared with the crystallite sizes, L-a, and the average particle size, and such comparison provides deep insight into the understanding of carbon molecular structure in the graphitized carbons. (C) 2017 Elsevier Ltd. All rights reserved.

A surface-sensitive conversion-electron-yield X-ray absorption fine structure (CEY-XAFS) detector that operates at elevated temperatures is developed to investigate the thermal decomposition of cathode materials for Li-ion batteries. The detector enables measurements with the sample temperature controlled from room temperature up to 450 degrees C. The detector is applied to the LiNi0.75Co0.15Al0.05Mg0.05O2 cathode material at 0% state of charge (SOC) and 50% SOC to examine the chemical changes that occur during heating in the absence of an electrolyte. The combination of surface-sensitive CEY-XAFS and bulk sensitive transmission-mode XAFS shows that the reduction of Ni and Co ions begins at the surface of the cathode particles at around 150 degrees C, and propagates inside the particle upon further heating. These changes with heating are irreversible and are more obvious at 50% SOC than at 0% SOC. The fraction of reduced Ni ions is larger than that of reduced Co ions. These results demonstrate the capability of the developed detector to obtain important information for the safe employment of this cathode material in Li-ion batteries. (C) 2016 Elsevier B.V. All rights reserved.