Rechargeable Lithium Batteries Research Articles

Mechanisms of Enhanced Electrochemical Performance by Chemical Short-Range Disorder in Lithium Oxide Cathodes.

LiCoO2 has been one of the dominant cathode materials commercially used in rechargeable lithium-ion batteries, while the performance is severely limited by its low reversible capacity (∼140 mAh/g), primarily due to the destructive phase transitions at high voltages (>4.2 V vs Li/Li+), leading to structural degradation and rapid decay of capacity. A recent experimental study [Wang et al. Nature 2024, 629, 341] showed that chemical short-range disorder (CSRD) in LiCoO2 can effectively prevent phase transitions and structural deterioration. To better understand the underlying mechanisms, we carry out a theoretical study on CSRD-based LiCoO2 by performing ab initio molecular dynamics simulations accelerated by machine learning and find that CSRD effectively suppresses phase transitions from hexagonal to monoclinic at Li0.5CoO2 and from O3 to H1-3 at Li0.25CoO2. The enhanced phase stability is attributed to the reduced lattice variation in the c-axis, the increased oxygen vacancy formation energies, the higher oxygen dimer formation energies, and the stabilization of Co atoms in the Li layers during delithiation. The high Li+ diffusion coefficients are found to arise from the low-barrier 0-TM diffusion channels and an expanded diffusion network from 2D to quasi-3D induced by CSRD. Furthermore, CSRD narrows the band gap of LiCoO2 with enhanced electronic conductivity, driven by the changes in the Co valence state and the introduction of linear Li-O-Li configurations. Equally important, CSRD can also enhance the stability of Li-rich cathode Li1.2Co0.8O2 for high capacity and excellent cycling performance. This work provides theoretical insights into the effects of CSRD on LiCoO2 and Li-rich cathodes for rational design and synthesis.

Self-Regulatory Lean-Electrolyte Flow for Building 600Wh Kg-1-Level Rechargeable Lithium Batteries.

Reducing excess electrolytes offers a promising approach to improve the specific energy of electrochemical energy storage devices. However, using lean electrolytes presents a significant challenge for porous electrode materials due to heterogeneous wetting. The spontaneous wetting of nano- or meso-pores within particles, though seldom discussed, adversely affects wetting under lean electrolyte conditions. Herein, this undesired wetting behavior is mitigated by enlarging the pore-throat ratio, enabling Li-rich layered oxide to function effectively at very low electrolyte/capacity (E/C) ratio of 1.4g Ah-1. The resulting pouch cell achieves 606Wh kg-1 and retains 80% capacity (75% energy) after 70 cycles. Through imaging techniques and molecular dynamics simulations, it is demonstrated that the pore-throat ratio effectively determines the permeability of electrolyte within particles. By elucidating pore-relating mechanisms, this work unveils promising potential of manipulating pore structures in porous electrode materials, an approach that can be applied to improve the specific energy of other devices including semi-solid-state lithium batteries.

Insights into Homogeneous Bulk Boron Doping at the Tetrahedral Site of NCM811 Cathode Materials: Structure Stabilization by Inductive Effect on TM-O-B Bonds.

Rechargeable lithium-ion batteries (LIBs) are critical for enabling sustainable energy storage. The capacity of cathode materials is a major limiting factor in the LIB performance, and doping has emerged as an effective strategy for enhancing the electrochemical properties of nickel-rich layered oxides such as NCM811. In this study, boron is homogeneously incorporated into the tetrahedral site of NCM811 through co-precipitation, leading to an inductive effect on transition metal (TM)-O-B bonds that delayed structural collapse and reduced oxygen release. Consequently, these changes culminate in an enhancement of cycling performance, translating to an initial specific capacity of 210mAh g-1 and a 95.3% capacity retention after 100 cycles. These interesting findings deepen the understanding of boron doping and shed light on the design of better lithium cathode materials on an applicable scale.

Advanced carbon as emerging energy materials in lithium batteries: A theoretical perspective

AbstractLithium batteries are becoming increasingly vital thanks to electric vehicles and large‐scale energy storage. Carbon materials have been applied in battery cathode, anode, electrolyte, and separator to enhance the electrochemical performance of rechargeable lithium batteries. Their functions cover lithium storage, electrochemical catalysis, electrode protection, charge conduction, and so on. To rationally implement carbon materials, their properties and interactions with other battery materials have been probed by theoretical models, namely density functional theory and molecular dynamics. This review summarizes the use of theoretical models to guide the employment of carbon materials in advanced lithium batteries, providing critical information difficult or impossible to obtain from experiments, including lithiophilicity, energy barriers, coordination structures, and species distribution at interfaces. Carbon materials under discussion include zero‐dimensional fullerenes and capsules, one‐dimensional nanotubes and nanoribbons, two‐dimensional graphene, and three‐dimensional graphite and amorphous carbon, as well as their derivatives. Their electronic conductivities are explored, followed by applications in cathode and anode performance. While the role of theoretical models is emphasized, experimental data are also touched upon to clarify background information and show the effectiveness of strategies. Evidently, carbon materials prove promising in achieving superior energy density, rate performance, and cycle life, especially when informed by theoretical endeavors.image

Enhancing the durability of aluminium-foil anodes in rechargeable lithium batteries via uniformly distributed alloy addition in the matrix phase

Uniformly distributed Si in the Al matrix as a solid solution induces a pinning effect, prevents cracking of the Al grains, suppresses pulverization and improves the cycling stability of Al-foil anodes in rechargeable lithium batteries.

Interfacially-localized high-concentration electrolytes for high-performance rechargeable aqueous lithium-ion batteries

Interfacially-localized high-concentration electrolytes were developed using an anionic surfactant and a magnesium(ii) salt to achieve selective Li ion transport, high electrochemical stability and superior SEI formation in aqueous electrolytes.

Optimizing Si─O Conjugation to Enhance Interfacial Kinetics for Low-Temperature Rechargeable Lithium-Ion Batteries.

With the growing demand for high-voltage and wide-temperature range applications of lithium-ion batteries (LIBs), the requirements for electrolytes have become increasingly stringent. While fluorination engineering has enhanced the performance of traditional solvent systems, it has also raised concerns regarding cost, environmental hazards, and low reduction stability. Through strategic molecular bond design, a novel class of low-temperature (LT) solvents-siloxanes-is identified, meeting the demands of LT and high-voltage applications in LIBs. The d-p conjugation of the Si─O bond enhances voltage resistance and weakens the Li+-solvent interactions. By modulating the number of Si─O conjugated bonds, the type of anion clusters in the solvation structure can be controlled, ultimately leading to the formation of a LiF and Si─O-rich interfacial layer and facilitating rapid Li+ conduction. Consequently, the graphite||NCM811 pouch cell (2.3 Ah, 4.45 V) with a siloxane-based electrolyte retains 75.1% of room temperature capacity (RTC) at -50°C. The rapid interface kinetics allow a superior reversible charging capacity retention of 67.6% at -40°C, with good cycle stability at -20°C. This study provides new insights into solvent design to fortify LIB performance in harsh conditions.

Smart Shoe Using Peizo Electric Sensors

Abstract: In this article, a piezoelectric shoe system that stores and harnesses walking kinetic energy to generate electric current for cell measurement and charging a smartphone is designed and constructed. It captures the forces exerted by walking, utilising mechanical stress through piezoelectric sensors, into electrical energy by means of a 27mm piezoelectric disk. Main components include: piezoelectric sheets, silicone adhesives, 1N4007 diodes, and a 3.7V rechargeable lithium-ion battery. This intelligent shoe therefore has the potential of being used independently without much effort towards its maintenance. Preliminary tests promise that the smart shoes would really be able to provide their users with a source of sustainable power, particularly in remote or outdoor settings.

Roles of the Polymer Backbone for Sulfurized Polyacrylonitrile Cathodes in Rechargeable Lithium Batteries.

Sulfurized polyacrylonitrile (SPAN) has emerged as a highly promising cathode material for next-generation lithium-sulfur (Li-S) batteries primarily due to its non-polysulfide dissolution and excellent cycle stability. Nevertheless, the specific roles and impacts of the pyrolyzed polyacrylonitrile, which constitutes the polymer backbone of SPAN, remain inadequately understood. In this study, comprehensive investigations from multiple aspects, including electrochemistry, spectroscopy, electron microscopy, and theoretical calculations, were conducted on a series of SPAN materials with various sulfur contents. The results reveal that the polymer backbone serves at least four critical functions. First, during the synthesis of SPAN, the polymer backbone provides reactive sites for the incorporation of sulfur through chemical bonding. Second, it establishes an extensive π-conjugated network via a dehydrogenation reaction by sulfur and serves as a conductive framework for SPAN. The chemically bonded sulfur atoms dope the polymer backbone, which narrows the highest occupied molecular orbitals-lowest unoccupied molecular orbitals (HOMO-LUMO) energy gap. Third, the polymer backbone plays an essential role in determining the first Coulombic efficiency, and the irreversibly inserted Li atoms further dope the polymer backbone and reduce the HOMO-LUMO energy gap. Lastly, the pyridine nitrogen within the polymer backbone exhibits an adsorption effect on lithium sulfide (Li2S) species, which stabilizes the cycling performances of the SPAN cathode. It is worth noting that the polymer backbone hardly contributes reversible capacity for the SPAN cathode in carbonate electrolytes within the 1 to 3 V operating voltage range. This study enhances our understanding of SPAN and may provide valuable guidance for the development of better SPAN materials and rechargeable batteries.

Hierarchically Porous Carbon Microspheres Coated with MnO2 Nanosheets as the Sulfur Host for High-Loading Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have emerged as a promising candidate for next-generation high-energy rechargeable lithium batteries, but their practical application is impeded by the sluggish redox kinetics and low sulfur loading. Here, we report the in situ growth of δ-MnO2 nanosheets onto hierarchical porous carbon microspheres (HPCs) to form an HPCs/S@MnO2 composite for advanced lithium-sulfur batteries. The delicately designed hybrid architecture can effectively confine LiPSs and obtain high sulfur loading up to 10 mg cm-2, in which the inner carbon microspheres with a large pore volume and large specific surface area can encapsulate high sulfur content, and the outer MnO2 nanosheets, as a catalytic layer, can improve the conversion reaction of LiPSs and suppress the shuttle effect. The thick HPCs/S@MnO2 electrode with 7 mg cm-2 sulfur loading delivers an areal capacity of 4.0 mAh cm-2 at 0.1 C and provides stable cycling stability with a low-capacity decay rate of 0.063 % per cycle after 200 cycles at 0.1 C. Furthermore, a Li-S pouch cell with a capacity of 2.5 A h is fabricated and demonstrates high cycling stability. This work offers a feasible method to build advanced sulfur electrodes with high areal loading and sheds light on their commercial application in high-performance Li-S batteries.

Beyond Organic Electrolytes: An Analysis of Ionic Liquids for Advanced Lithium Rechargeable Batteries

The fast-growing area of battery technology requires the availability of highly stable, energy-efficient batteries for everyday applications. This, in turn, calls for research into new battery materials, especially with regard to a battery’s main component: the electrolytes. Besides the demands associated with solid ionic conduction and appropriate electrochemical behaviour, considerable effort will be necessary to thoroughly reduce safety risks in terms of flammability, leakage, and thermal runaway. Consequently, completely new classes of electrolytes need to be developed that are compatible with energy storage systems. Despite the progress made in solid polymer electrolytes, such materials have suffered from limitations to their real-world application. Now, ionic liquids are considered a class of electrolytes with the most potential for the creation of more advanced and safer lithium–ion batteries. In recent decades, ILs have been widely explored as potential electrolytes in the search for new breakthroughs in the ESS field, such those associated with fuel cells, lithium–ion batteries, and supercapacitors. The present review will discuss ILs that present high ionic conductivity, a lower melting point below 100 °C, and which feature up to 5–6 V wide electrochemical potential windows vs. Li+/Li. Furthermore, ILs exhibit good thermal stability, non-flammability, and low volatility—all of which are attributes realized by appropriate cation–anion combinations. This paper seeks to review the status of research concerning ILs, along with the advantages and challenges yet to be overcome in their development.

Electrostatic Aspect of the Proton Reactivity in Concentrated Electrolyte Solutions.

Water-in-salt electrolytes with a surprisingly large electrochemical stability window of ≤3 V have revived interest in aqueous electrolytes for rechargeable lithium-ion batteries. However, recent reports of acidic pH measured in concentrated electrolyte solutions appear to be in contradiction with the suppressed activity of the hydrogen evolution reaction (HER). Therefore, the fundamental thermodynamics of proton reactivity in concentrated electrolyte solutions remains elusive. In this work, we have used density functional theory-based molecular dynamics (MD) simulations and the proton insertion method to investigate how the HER potential shifts in concentrated LiCl solutions under both acidic and alkaline conditions. Our results show that the intrinsic HER activity increases significantly with the salt concentration under acidic conditions but remains relatively constant under alkaline conditions. Moreover, by leverage over finite-field MD simulations, it is found that a determining factor for the HER activity is the Poisson potential of the liquid phase, which increases in concentrated electrolyte solutions with comparable values from both density functional theory and point-charge models.

Photoemission spectroscopy of battery materials

Recognized by the 2019 Nobel Prize in Chemistry, rechargeable lithium-ion battery (LIB) has become a world-revolutionary technology. Further developments of LIB-based and “beyond LIBs” regarding capacity, cycle life, and safety are intimately associated with the fundamental understanding of chemical compositions, structures, physical properties of electrodes and electrolytes, and other related components. The time-evolving snapshots of the dynamical processes occurring during the battery operation can help design better strategies to prevent the formation of uncontrolled interphase layers, dendrites, electrode/electrolyte decompositions, and generation of gases. Photoemission spectroscopy (PES) has become one of the important techniques for understanding the aforementioned aspects. However, many potential pitfalls and cautions need to be considered from sample preparation, during PES measurements, to data analyses. Although the primary focus of this article is not to evaluate the PES technique itself, we first introduce a minimal set of fundamental concepts to minimize misinterpretation arising from the physics of PES. Subsequently, we examine studies that utilize PES techniques to determine chemical compositions of solid- and liquid-state battery materials, energy level diagrams that bridge different terminologies between PES and electrochemistry, along with the theoretical aspects of PES evolving from first-principle calculations to machine learning. Toward the end of this review, we outline potential future research directions.

Hydrogen Production and Li-Ion Battery Performance with MoS2-SiNWs-SWNTs@ZnONPs Nanocomposites.

This study explores the hydrogen generation potential via water-splitting reactions under UV-vis radiation by using a synergistic assembly of ZnO nanoparticles integrated with MoS2, single-walled carbon nanotubes (SWNTs), and crystalline silicon nanowires (SiNWs) to create the MoS2-SiNWs-SWNTs@ZnONPs nanocomposites. A comparative analysis of MoS2 synthesized through chemical and physical exfoliation methods revealed that the chemically exfoliated MoS2 exhibited superior performance, thereby being selected for all subsequent measurements. The nanostructured materials demonstrated exceptional surface characteristics, with specific surface areas exceeding 300 m2 g-1. Notably, the hydrogen production rate achieved by a composite comprising 5% MoS2, 1.7% SiNWs, and 13.3% SWNTs at an 80% ZnONPs base was approximately 3909 µmol h-1g-1 under 500 nm wavelength radiation, marking a significant improvement of over 40-fold relative to pristine ZnONPs. This enhancement underscores the remarkable photocatalytic efficiency of the composites, maintaining high hydrogen production rates above 1500 µmol h-1g-1 even under radiation wavelengths exceeding 600 nm. Furthermore, the potential of these composites for energy storage and conversion applications, specifically within rechargeable lithium-ion batteries, was investigated. Composites, similar to those utilized for hydrogen production but excluding ZnONPs to address its limited theoretical capacity and electrical conductivity, were developed. The focus was on utilizing MoS2, SiNWs, and SWNTs as anode materials for Li-ion batteries. This strategic combination significantly improved the electronic conductivity and mechanical stability of the composite. Specifically, the composite with 56% MoS2, 24% SiNWs, and 20% SWNTs offered remarkable cyclic performance with high specific capacity values, achieving a complete stability of 1000 mA h g-1 after 100 cycles at 1 A g-1. These results illuminate the dual utility of the composites, not only as innovative catalysts for hydrogen production but also as advanced materials for energy storage technologies, showcasing their potential in contributing to sustainable energy solutions.

Ultra-lightweight rechargeable battery with enhanced gravimetric energy densities >750 Wh kg−1 in lithium–sulfur pouch cell

Lithium–sulfur (Li–S) rechargeable batteries have been expected to be lightweight energy storage devices with the highest gravimetric energy density at the single-cell level reaching up to 695 Wh kg(cell)−1, having also an ultralow rate of 0.005 C only in the first discharge. Sulfurized polyacrylonitrile (SPAN) is one of the sulfur-based active materials, which allows more freedom in the Li–S cell design because it shows no undesirable reactions with electrolyte solutions. Here we present an original Li–S pouch cell construction, ADEKA’s Lithium–Sulfur/Pouch Cell (ALIS-PC). It is an ultra-lightweight rechargeable battery cell, which is designed by combining the SPAN cathode and effective ten technologies involving chemical engineering. As a result, the highest gravimetric energy densities of 713 and 761 Wh kg(cell)−1 after some charge-and-discharge cycles, which were based on the total mass of all cell components, were achieved with successful operating at 0.1 and 0.05C-rates, respectively, significantly exceeding those of commercial lithium-ion and next-generation rechargeable batteries in development.

Li Concentration Change Around Cu/Lipon Interface Measured By Time of Flight Elastic Recoil Detection Analysis

All-solid-state rechargeable lithium (Li) batteries (ASSBs) utilizing inorganic lithium-ion (Li+) conductive solid electrolytes (SEs) are gathering significant interest as a next-generation battery. To enhance the energy density of ASSBs, employing a Li metal anode is crucial due to its substantially higher capacity (3860 mAh g-1) compared to conventional graphite anodes (372 mAh g-1). Among various SEs compatible with Li metal anodes, lithium phosphorus oxynitride glass electrolyte (LiPON) stands out as an especially promising material for stabilizing the Li/SE interface [1]. This is evidenced by the fact that thin-film-type ASSBs employing LiPON and Li metal anodes demonstrate stable charge-discharge cycles over ten thousand cycles without capacity degradation [2].Regarding the Li/LiPON interface in thin-film ASSBs, it is observed that Li plating-stripping reactions occur stably. Yet, advanced analyses indicate the formation of a reaction layer at this interface. Cheng et al. utilized Cryo-STEM analysis to investigate the Li/LiPON interface, revealing the generation of by-products like Li2O, Li3N, and Li3P within an 80 nm thickness range from the interface [3]. Similarly, Sicolo et al. conducted XPS measurements on the LiPON surface before and after Li deposition, confirming the formation of a reaction layer immediately following Li layer deposition [4]. Theoretical calculations have suggested that LiPON reacts with Li metal and the thermodynamical stability of LiPON is estimated to be 0.68 V vs. Li/Li+ [5]. On the other hand, Schwietert et al. have reported that LiPON does not undergo reductive decomposition less than 0.68 V by taking a metastable state because an activation barrier for the decomposition can retard reductive decomposition [6]. Clarifying this interphase phenomenon is essential for the development of ASSBs with Li metal anodes.In this study, focusing on the increase in Li content with the reductive decomposition of LiPON, we investigate Li concentration changes around the Cu/LiPON interface by time-of-flight elastic recoil detection analysis (TOF-ERDA) [7]. TOF-ERDA needs no sample pretreatment for the detection of Li and then it can effectively observe Li concentration changes induced by electrochemical reactions around the interface. We confirmed that Li concentration increased around the interface within 30 nm thickness when maintained at 0.006 V vs. Li/Li+ before the Li plating voltage at 0 V vs. Li/Li+. This means that a decomposed region of LiPON forms around the interface within 30 nm thickness in this situation. Electrochemical analysis suggests one of the decomposed materials to be Li3P [4]. These findings basically align with TEM-EELS data, underscoring the utility of TOF-ERDA in analyzing Li concentration changes around interfaces.Reference Chung K, Kim WS, Choi YK (2004) Lithium phosphorous oxynitride as a passive layer for anodes in lithium secondary batteries. J Electroanal Chem 566:263-267 Wang B, Bates JB, Hart FX, Sales BC, Zuhr RA, Robertson JD (1996) Characterization of thin‐film rechargeable lithium batteries with lithium cobalt oxide cathodes. J Electrochem Soc 143:3203-3213 Cheng D, Wynn TA, Wang X, Wang S, Zhang M, Shimizu R, Bai S, Nguyen H, Fang C, Kim M, Li W, Lu B, Kim SJ, Meng YS (2020) Unveiling the stable nature of the solid electrolyte interphase between lithium metal and LiPON via cryogenic electron microscopy. Joule 4:2484-2500 Sicolo S, Fingerle M, Hausbrand R, Albe K (2017) Interfacial instability of amorphous LiPON against lithium: A combined Density Functional Theory and spectroscopic study. J Power Sources 354:124-133 Zhu Y, He X, Mo Y (2015) Origin of outstanding stability in the lithium solid electrolyte materials: insights from thermodynamic analyses based on first-principles calculations. ACS Appl Mater Interfaces 7:23685-23693 Schwietert TK, Vasileiadis A, Wagemaker M (2021) First-Principles prediction of the electrochemical stability and reaction mechanisms of solid-state electrolytes. JACS Au 1:1488-1496 Yasuda K (2020) Time-Of-Flight ERDA for depth profiling of light elements. Quantum Beam Sci 4:40 AcknowledgementThis work was supported by JSPS KAKENHI “Interface IONICS” (JP19H05813, 20H05293, and 22H04617) and by JST GteX, JPMJGX23S2.

Lithium Batteries Operating at Wide Temperatures: Opportunities and Challenges

AbstractThe development of rechargeable lithium batteries (RLBs) has made a great contribution in solving the problems in the current era, such as energy shortage and climate change. With the expanding of application field of RLBs from portable device to large‐scale electric equipment, it is an urgent demand for RLBs to operate in a wide range of temperature. More and more attention has been paid to the design of wide‐temperature RLBs. Therefore, a timely and critical overview of the latest development in the field of RLBs operating at wide temperatures is needed. In this review, an in‐depth understanding on how the temperature affects the thermodynamics of lithium‐ion transport at electrodes, electrolytes, and electrode/electrolyte interfaces is emphasized. Recent progress in probing the temperature effects on electrochemical performance fading is comprehensively discussed. Different strategies to widen the working temperature of RLBs, including regulating the electrode degradation, interface evolution, and electrolyte solvation chemistry are also reviewed. Finally, an outlook of potential future research directions is also proposed, which sheds light on the design of novel electrodes and electrolytes for next‐generation RLBs operating at wide temperatures.

Development of Aluminum-Foil Anodes for Rechargeable Lithium Batteries

Alloy anode materials, such as silicon, tin, and aluminum, are expected to be used in rechargeable lithium batteries owing to high theoretical capacities, compared to conventional carbonaceous anodes. However, the high capacities inevitably cause drastic volume change (+100~300%) of the anode materials during battery reactions (i.e., lithium insertion and extraction), which usually leads to fatal structural degradation.[1,2] Although downsizing the anode materials into fine particles is an effective way to endure the huge volume change,[3] the complicated preparation process raise the production costs, and the indispensable supporting substance (e.g. polymer binder, current collector) for the active material particles decreases the practical capacity of the total anode. Therefore, easy-to-manufacture strategy is still strongly demanded for practical application of alloy anode materials towards high energy-density and low-cost rechargeable lithium batteries.Recently, we have reported a metallurgical approach which stabilizes the structure change of Al foils during repeated lithiation and delithiation. By adjusting the composition and hardness of the Al matrix, a homogeneous in-plane lithiation and an out-of-plane (one-dimensional) volume expansion (+100%) are achieved during lithiation.[4] Because the LiAl phase has a certain tolerance to off-stoichiometry composition, a concentration gradient can be formed from the surface to the inside of Al foils, driving the interdiffusion of Al and Li. During delithiation, the Al matrix is recrystallized and self-organized to pillar/porous structure, which can tolerant the volume changes in subsequent cycles. The reversible structure changes allow the Al foils to work as self-contained anodes. The Al-foil anodes can be divided into a surface layer that alloys Li, and a base layer that maintains the structural stability and electric conductivity. However, during cycling, the electrolyte exhibits a significant impact on the structure stability of the Al-foil anodes. The decomposition products of the conventional carbonate-based electrolytes, such as 1 M LiPF6 in EC-DMC, easily passivate the surface of Al-foil anodes. As a result, the base layer is gradually consumed during cycling accompanied with the pulverization of the surface layer. The electrolyte permeates the fresh Al surface would further passivate the Al surface. Eventually, the capacity would be vanished, when the Al-foil anodes are completely pulverized, or the electrolytes are completely decomposed.To extend the cycle life of Al-foil anodes, in this presentation, we summarize the degradation mechanism of the Al-foil anodes and introduce the improvement strategies from various perspectives, including alloy additions, electrolyte selection and the structural design. Appropriate alloy additions can moderate the surface formation of Al matrix during delithiation, which prevent the electrolyte permeation. In addition, salt concentrations, anion and solvent combinations markedly affects the electrolyte compatibility with the Al-foil anodes, where the cyclability can be significantly improved with electrolytes that are less susceptible to passivating the Al surface. Furthermore, introducing distinct thermodynamic and kinetic characteristics between the surface and base layers, such as cladding Al foils,[5] can effectively prevent the electrolyte permeation and Li penetration consume the base layer.[1] T. Ichitsubo et al, J. Mater. Chem. A 21, 2701 (2011).[2] T. Ichitsubo et al, J. Electrochem. Soc. 159, A14 (2012).[3] T. Wada, T. Ichitsubo et al, Nano Lett. 14, 4505 (2014).[4] H. Li, T. Ichitsubo et al, Nat. Commun. 11, 1584 (2020).[5] H. Li, T. Ichitsubo et al, J. Mater. Chem. A 11, 23311 (2023).

Redox Reaction of Some Nitroxyl Radicals in 1-Butyl-1-Methylpyrrolidinium Bis(fluorosulfonyl)amide in the Presence and Absence of Lithium Ion

Ionic liquids composed of bis(fluorosulfonyl)amide (FSA–) have been investigated as the promising electrolytes for rechargeable lithium batteries due to their high conductivity and low viscosity dependence on the Li salt concentration. Despite many reports on FSA–-based ionic liquids as the electrolytes for rechargeable lithium and sodium batteries, a few studies have been reported on the electrode reactions of redox species. The redox reactions of Ag+/Ag and ferrocenium (Fc+)/ferrocene (Fc) were investigated in BMPFSA (BMP+ = 1-butyl-1-methylpyrrolidinium)[1]. It was reported that the donor ability of FSA– was found to be lower than that of bis(trifluoromethylsulfonyl)amide (TFSA–) from the potential difference between Ag+/Ag and Fc+/Fc. 2,2,6,6,-Tetramethylpiperidine-1-oxyl (TEMPO) is one of the typical niroxyl radicals with redox activity. In the present study, the redox reactions of TEMPO and 4-oxo-TEMPO were investigated in BMPFSA in the presence and absence of lithium ion.The redox reactions of TEMPO+/TEMPO and 4-oxo-TEMPO+/4-oxo-TEMPO were observed on a Pt electrode in BMPFSA by cyclic voltammetry. The formal potential of TEMPO+/TEMPO was lower than that of 4-oxo-TEMPO+/4-oxo-TEMPO. The formal potential of TEMPO+/TEMPO in the presence of Li+ was higher than that in the absence of Li+, suggesting that the interaction between TEMPO and Li+ affected the thermodynamic properties of the redox species. The diffusion coefficients and the standard rate constants were evaluated by chronoamperometry and electrochemical impedance spectroscopy, respectively. The diffusion coefficient and the standard rate constant were suggested to be controlled not only by the viscosity but also by the interaction between the nitroxyl radicals and Li+.Reference[1] S. Kato, N. Serizawa, and Y. Katayama, J. Electrochem. Soc., 170, 046504 (2023).

Study on High-Voltage Cathode Li-Ni-Mn Spinel Oxides with Low-Temperature Magnetism

Lithium-ion rechargeable batteries have been attracting researcher’s interest, because they are candidate to address environmental issues, especially for application to electric vehicles and stationary energy storage systems. The battery operating voltage is one of the factor affecting the energy density of battery cell, and therefore positive electrode with high operating voltage is very attracting. A typical high-voltage cathode material, LiNi0.5Mn1.5O4 is an end member of LiNixMn2-xO4 solid solution compounds (0.00<x<0.50). From the previous study, it is known that LiNi0.5Mn1.5O4 spinel is a ferri-magnetic material with large magnetic moment and high transition temperature. In this work, the compounds of LiNixMn2-xO4 (0.40<x<0.50) are studied with both low-temperature magnetism and electrochemical charge-discharging. Additionally, the correlation between electrochemical and magnetic properties is also discussed.LiNixMn2-xO4 (0.40<x<0.50) were prepared by gelation of nitrate/citrate solution, thermal decomposition at 500 ℃ and annealing under various conditions (temperature and atmosphere). Under the preparation condition at relatively low temperature (700 ℃) in oxygen atmosphere, they were single phase of cubic spinel with fine particles. The lattice parameters monotonously decreased, as x increased. The charge-discharge profiles have twin plateaus around 4.7 V, to Ni2+/Ni3+ and Ni3+/Ni4+ redox signals, with a small signal at ~4.0 V. The capacity at >4.5 V formers increased with x and that at <4.5 V was reduced. From the magnetic evaluation, the saturation magnetization at 2 K (Ms) increased with x, and simultaneously, the ferri-magnetic/paramagnetic transition temperature (Tc), evaluated from temperature dependence of the saturation magnetization, shifted higher. These results exhibited the following relation-ships (presented in Fig. 1); the capacity at >4.5 V was almost proportional to Ms, and the operating voltage was proportional to Tc. However, it was found that the magnetic response under weak magnetic field was not usual (shown in Fig. 2) and it implied two-step phase transition around Tc. The anomaly was thought to be attributed to magnetic in-homogeneity, which is very sensitive to the specimen characters. The analysis of experimental results of specimens prepared under different conditions are being carried out and then presented and discussed at the conference. Figure 1