Charge-discharge Performance Research Articles

Excellent Energy Storage and Charge-Discharge Performance in (Pb1-xCax)(Zr0.55Sn0.45)O3 Antiferroelectric Ceramics.

Lead-based antiferroelectric (AFE) ceramics have the advantages of high power density, fast charge and discharge speed, and the electric-field-induced AFE-FE phase transition, making them one of the potential dielectric energy storage materials. However, the energy storage density still needs to be improved. In this work, (Pb1-xCax) (Zr0.55Sn0.45)O3 (PCZS, x = 0.01, 0.02, 0.03 and 0.04) antiferroelectric ceramics were successfully prepared using the solid-state reaction and two-step sintering methods. The results showed that as the Ca2+ content increased, the average grain size decreased from 1.38 ± 0.42 to 1.06 ± 0.35 μm and the dielectric breakdown strength increased from 270 to 325 kV/cm for ceramics with 80 μm in thickness. Two kinds of superlattice structures (F-point with 1/2{ooo} patterns and incommensurate modulation structure (IMS) pattern with 1/n{110} patterns) were observed, indicating the typical octahedral tilting-related AFE structure. The (Pb0.98Ca0.02) (Zr0.55Sn0.45)O3 bulk ceramics, due to the refined polarization-electric field hysteresis loop of the IMS, achieved a maximum recoverable energy storage density (Wrec) of 6.61 J/cm3 with an efficiency (η) of 84.01%. In the circuit of charge-discharge to a load, an ultrahigh power density (PD) of 276.67 MW/cm3 and a discharged energy density (Wdis) of 6.24 J/cm3 were obtained in PCZS2 bulk ceramics at 290 kV/cm. The high Wrec and Wdis indicate that PCZS ceramics offer potential applications in the field of pulse-power electric devices.

In Situ Electron Tomography Insights into the Curvature Effect of a Concave Surface on Fe Single Atoms for Durable Oxygen Reaction.

Curvature-induced interfacial electric field effects and local strain engineering offer a powerful approach for optimizing the intrinsic catalytic activity of single-atom catalysts (SACs). Investigations into the surface curvature on SACs are still ongoing, and the impact of the concave surface is often overlooked. In this work, theoretical calculations indicate that curved surfaces, particularly those with concavity, can optimize the electronic structures of single Fe sites and facilitate the reductive release of *OH. A carbon sphere featuring uniformly oriented channels and a chiral multi-shelled carbon hollow nanosphere are selected as carbon matrices due to their accessible concave and/or convex surfaces. After loading Fe species, the resulting catalysts with Fe SA in curved surfaces exhibit excellent oxygen reduction reaction activity (E1/2 = ≈0.89V), strong methanol tolerance, and favorable long-term stability. Impressively, a solid-state flexible Zn-air battery based on this catalyst exhibits a remarkable durability over 40h with a high peak power density of 122.1mW cm-2 and excellent charge-discharge performance at different bending angles. This work offers in-depth insights into the rational design of carbon supports with highly curved surfaces, offering new opportunities for the microenvironmental regulation of SACs at the atomic level.

Promising honeycombed cork activated carbon for high desalination performance brackish water treatment

Cork activated carbon (CAC), derived from natural cork, was successfully prepared through two steps of carbonation and activation, and used for desalinating brackish water. The CAC presents a uniform honeycomb structure composed of porous carbon nanoflakes (200–300 nm) and large specific surface area (SSA) (2680 m2 g−1), offering transport channels and a large number of adsorption sites to NaCl solution. The CAC showed excellent capacitance (116 F g−1), small internal resistance and better charge-discharge performance. Moreover, the optimized CAC showed high desalting capacity (9.44 mg g−1), charge efficiency (46.72 %), and lower energy consumption (54.19 Wh m−3) in the desalination process, superior to that of the reported biomass-based activated carbons, which can be attributed to the stable honeycomb structure, high microporous volume (0.86 cm3·g−1) and large pore size (2.43 nm). This investigation demonstrates the potential application of cork granules-based CAC electrodes in the field of desalination.

Fluoroethylene Carbonate Electrolyte Additive for Improved Charge-Discharge Performance of Co-free High Entropy Spinel Oxide Anodes for Lithium-Ion Batteries

High entropy spinel oxide (HESO) materials have attracted interest as promising anode candidates for lithium-ion batteries (LIBs). Increasing the initial Coulombic efficiency (ICE), longevity, and rate capability of HESO is crucial. The performance of LIBs is heavily influenced by the characteristic of the solid-electrolyte interphase (SEI) formed on the electrode surface, which depends on the electrolyte composition. This study explores how modulating the concentration of fluoroethylene carbonate (FEC) in carbonate-based electrolyte affects the electrochemical properties of (MnFeNiCrCu)3O4 HESO anodes. Notably, the addition of 10 wt% FEC in the electrolyte significantly enhances HESO performance. With 10 wt% FEC, the electrode achieves impressive capacities of 806 and 630 mAh g–1 at 50 and 2000 mA g–1, respectively, with no noticeable capacity degradation after 400 cycles at 500 mA g–1. X-ray photoelectron spectroscopy (XPS) analysis indicates that 5 wt% FEC resulted in inferior passivation, leading to satisfactory performance. However, incorporating optimal FEC (10 wt%) achieves a balance of inorganic and organic SEI components, resulting in superior electrochemical properties. While the inorganic component provides great passivation, an excessive amount of LiF from higher FEC content (15 wt%) makes the SEI brittle and resistive, leading to its breakage during cycling and subsequent capacity decay. Our study offers important insights for improving the performance of HESO anodes for LIBs through electrolyte optimization.

Study on structure and electrical properties of BNBT-La2/3ZrO3 ceramic

BNT-based energy storage dielectric material is a new type of multifunctional material with environmental friendliness, high energy storage density, and excellent temperature stability. It is a research hotspot where different components are introduced into BNT-based ceramics to obtain ceramic materials with high energy storage density. In this study, 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (BNBT) was selected as the substrate and doped with La2/3ZrO3 (LZ). Through the modification of La3+/Zr4+ at A/B sites, wider optical bandgap and finer grains with exceptionally large electrical breakdown strength and relatively strong relaxation behaviors in the appropriate range were obtained. Ultimately, an ultra-high energy storage density of 6.48 J/cm3 was attained at 480 kV/cm with a La2/3ZrO3 concentration of 0.07 mol%. In addition, the BNBT-LZ ceramics exhibited a good frequency-stabilized dynamic range (Wrec = 3.29 ± 6.7 % J/cm³, 10–200 Hz) and temperature stability (Wrec = 3.63 ± 9.9 % J/cm³, 20–160 °C), together with excellent charge-discharge performance(t0.9 = 3.36 μs). All these characteristics demonstrate that the modification of BNT-based ceramics by La3+/Zr4+ has a significant effect on the energy storage density. The results show that the BNBT-LZ system can be used as a promising dielectric material for high energy storage density capacitors.

Effect of Cell Diameter on Charge-Discharge Performance in All-Solid-State Batteries

All-solid-state batteries are expected to offer high safety and energy density. The discovery of solid electrolytes with high ionic conductivity has accelerated development toward practical applications. However, high performance has only been demonstrated in small cells at the laboratory level and has not yet been introduced in larger all-solid-state batteries that can be used in electric vehicles and energy storage systems. To the best of our knowledge, no studies have been reported on all-solid-state batteries when large cells are used. To elucidate the factors required for large-scale all-solid-state batteries, we fabricated all-solid-state battery cells with various diameters and compared their charge-discharge performance.Composite electrode was prepared by mixing the cathode active material Nb-coated LiNi1/3Mn1/3Co1/3O2, the solid electrolyte Li6PS5Cl, and the conductivity aid acetylene black in a weight ratio of 1:1:0.1 in an argon atmosphere. In-Li alloy was used for the counter electrode. Electrodes and electrolytes were placed in ceramic tubes with inner diameters of 10 and 30 mm with a fabrication pressure of 188 MPa and a stack pressure of 40 MPa. Galvanostatic charge-discharge measurements were performed between 2.0 and 4.0 V. AC impedance measurements were also carried out.The initial discharge capacities of the cells with the diameters of 10 and 30 mm were both 140 mA h g-1 at a 0.1C rate. From the test of the rate capability, no clear difference was observed between the two cells. Nyquist plot from the AC impedance measurements exhibited one semicircle assigned to charge transfer resistance. The area specific resistance also did not show the difference in the cell diameter. These results imply that the size of the cell diameter does not affect the charge-discharge performance in cells capable of holding high pressures.

Rutile TiO2 As a Negative Electrode Material for Proton Rechargeable Batteries

With the increasing importance of rechargeable batteries, the use of monovalent alkali metal ions such as Na and K ions has been actively investigated. However, there have been relatively few research reports on proton rechargeable batteries. When using protons as a carrier ion, there are concerns about irreversible H2 evolution due to the poor electrochemical stability of aqueous electrolytes. If the fast proton conduction originating from Grötthuss mechanism can be utilized, the rechargeable batteries with water-based electrolytes including protons as carrier ions that combine safety and rapid charge–discharge performance is expected.1−3 On the other hand, it is required that negative electrodes operate at a lower potential to improve battery voltages. Although anatase TiO2 have been reported as the host material for protons to show a reversible capacity, H2 evolution remains an unavoidable issue. In this study, we focused on the energy level of the conduction band of rutile TiO2, which is more positively located than anatase TiO2. It is expected that the positively located conduction band reduce irreversible HER and achieve a long-cycle life. The influence of crystal structures and particle sizes on battery performances of rutile, anatase, and brookite TiO2 were systematically examined. To investigate the effect of crystal structure on the electrochemical protonation of TiO2 with as little influence of particle size as possible, TiO2 was synthesized by different preparation methods for each structure (Figure 1a). The electrolyte used in this study is the citric buffer solution consisting of 1 M citric acid and 1 M trisodium citrate. The electrochemical protonation/deprotonation was investigated using three-electrode type cell with the counter electrode of activated carbon and the reference electrode of Ag/AgCl in sat. NaCl.Figure 1b shows galvanostatic charge–discharge properties of several TiO2 synthesized by the hydrothermal method. The reaction potentials of TiO2 with protons are rutile, brookite, and anatase, in that order, reflecting the more positive conduction band level of the rutile. The XRD measurements revealed that the rutile TiO2 uptakes/releases protons while maintaining the parent phase without any phase transitions (Figure 1c). The lattice parameters, a and c reversibly and slightly expanded/contracted (Figure 1d), but did not change as much as during the insertion/extraction of alkali metal ions such as Li+ and Na+.4,5 The fact that lattice expanded and contracted clearly reveals that protons were inserted into the rutile TiO2 bulk. Meanwhile, the larger particles showed little protonation and H2 evolution was dominant regardless of the crystal structures. The particle size is an influential factor, and smaller sizes are advantageous in the electrochemical protonation.6 AcknowledgementThis work was supported by a Grant-in-Aid for Scientific Research (B) (20H02840, 24K01601) from the Japan Society for the Promotion of Science (JSPS).References Wang, Y. Xie, K. Tang, C. Wang, C. Yan, Angew. Chem. Int. Ed., 57 (2018) 11569.B. Mitchell, W. C. Lo, A. Genc, J. LeBeau, V. Augustyn, Chem. Mater., 29 (2017) 3928.Makivić, J.-Y. Cho, K. D. Harris, J.-M. Tarascon, B. Limoges, V. Balland, Chem. Mater., 33 (2021) 3436.Usui, S. Yoshioka, K. Wasada, M. Shimizu, H. Sakaguchi, ACS Appl. Mater. Interfaces, 7 (2015) 6567.Usui, Y. Domi, S. Ohnishi, N. Takamori, S. Izaki, N. Morimoto, K. Yamanaka, K. Kobayashi, H. Sakaguchi, ACS Mater. Lett., 3 (2021) 372.Shimizu, D. Nishida, A. Kikuchi, S. Arai, J. Phys. Chem. C, 127 (2023) 17677. Figure 1

(Invited) Development of Deep Eutectic Electrolytes Using Urea Derivatives Toward Safe, High Voltage Lithium-Ion Batteries

Deep eutectic solvents are mixtures that exhibit melting points much lower than those of the end members due to various intermolecular interactions. Deep eutectic solvents have attracted attention because the utilized high melting point compounds can act as flame-resistant solvents.1 However, the stable operation of Li-ion batteries (LIBs) with deep eutectic electrolytes (DEEs) is still challenging, likely due to their high protonic nature and consequent narrow potential window.2 To develop Li-ion DEEs with a wide potential window, we investigated DEEs based on lithium bis(fluorosulfonyl)amide (LiFSA) and a series of urea derivatives to clarify the correlation between compound structure and electrolyte properties. Furthermore, we examined the electrode performances of the Li4Ti5O12 (LTO) negative electrode and LiFePO4 (LFP) positive electrode in the DEEs.To prepare the DEEs, urea derivatives such as urea, 1-methylurea, 1,3-dimethylurea, 1,1-dimethylurea, and tetramethyl urea were mixed with LiFSA at molar ratios of 1:2 or 1:4 at room temperature. The oxidation and reduction stability were evaluated by linear sweep voltammetry (LSV) in three-electrode cells with Pt foil as the working electrode. Galvanostatic charge-discharge tests were also performed in three-electrode cells with LTO or LFP working electrodes and activated carbon counter electrodes.The prepared LiFSA:urea derivative (1:4) mixtures (LiFSA:urea, LiFSA:1,3-dimethylurea, and LiFSA:tetramethylurea) became transparent liquids at room temperature. Moreover, LiFSA:1,3-dimethylurea and LiFSA:tetramethylurea were clear liquids even in more concentrated 1:2 mixtures. Using the five DEEs, we evaluated their electrolyte properties. Figure 1 shows the LSV curves of the DEEs. Among the five deep eutectic liquids, LiFSA:1,3-dimethylurea (1:2) exhibited the widest potential window of 4.49 V, showing an even wider potential window than electrolytes with non-protonic tetramethyl urea.Figure 2a displays the charge-discharge performances of LTO electrodes in the DEEs. Reversible charge-discharge was confirmed for all DEEs, and the Coulombic efficiency (urea; 92%, 1,3-DMU; 98%) and capacity retention (urea; 88%, 1,3-DMU; 87% after 50 cycles) were higher than tetramethylurea (74% and 22%, respectively). The excellent cycling properties of LiFSA:urea (1:4) may be attributed to its high ionic conductivity, while in LiFSA:1,3-dimethylurea (1:2) a stable film may be formed on the electrode. The LiFSA:tetramethylurea cell showed lower cycle stability than the LiFSA:1,3-dimethylurea cell, possibly due to electrolyte precipitation during cycling because LiFSA:tetramethylurea (1:2) electrolyte is an almost saturated solution. We further focused on the 1:2 LiFSA:1,3- dimethylurea and 1:4 LiFSA:urea and followed similar methods to how the LTO electrodes were tested. Within both of these DEE, the charge-discharge of LFP showed excellent performance with high capacity retention and CEs near 100% (Figure 2b). The plateau potential of LFP does not approach the decomposition limit of either DEE, which likely encourages good performance. Moving to a higher voltage cathode, LiMn2O4 (LMO), we also observed relatively stable charge-discharge cycling with these DEEs.In total, these results demonstrate the potential applicability of the DEE to 3 V-class LIBs. In the presentation, we will also discuss the passivation films on the electrodes and solvation structure in DEEs.

An SEI-Forming Fluorophosphate Solvent for High-Temperature Lithium-Ion Batteries

Introduction Recently, there has been an increasing demand for high-energy-density lithium-ion batteries (LIBs) that operate under broad temperature conditions (–40 to 70°C). As an electrolyte solvent, ethylene carbonate (EC) has been essential to form a solid electrolyte interphase (SEI), which effectively suppresses side reactions such as graphite exfoliation and continuous electrolyte decomposition on negative electrodes(1). However, EC is not only flammable but also susceptible to severe oxidative and reductive decomposition at high temperatures, thereby limiting the operational temperature of LIBs to around 55°C(2). There has been no alternative solvent that has (i) SEI-forming ability, (ii) nonflammability, and (iii) high-temperature stability. Hence, it has been challenging to realize the high-temperature and safe operation of LIBs.In this study, we designed and synthesized a novel phosphate solvent, FDPO, which is nonflammable and can form stable SEI on graphite. FDPO has a structural feature similar to LiPO2F2, which can improve SEI properties and high-temperature performance of batteries(3-4). We investigated the charge-discharge performances of negative and positive electrodes for LIBs with FDPO-based electrolytes at high temperature. Experimental methods Electrolytes were prepared by mixing LiPF6, FDPO, and methyl 2,2,2-trifluoroethyl carbonate (FEMC), which is known as a low viscous and flame-retardant solvent. Charge-discharge tests were conducted using coin cells with the natural graphite|Li cell configuration. The current density of 186 mA g-1 (2C) was applied from the 4th cycle after pre-conditioning three cycles at a current density of 37.2 mA g-1 (10C). The cut-off voltage range was set to 2.5 V – 0.01 V. Results and discussion Figure 1 shows the charge-discharge performances of natural graphite|Li coin cells at 70°C. The cell with the commercial electrolyte exhibited severe capacity decay to ca. 142 mAh g-1 after 50th cycles. On the other hand, the cell with FDPO-based electrolyte retained a high reversible capacity of ca. 343 mAh g-1. In addition, the charge-discharge efficiency was over 99.6% in the FDPO-based electrolyte, indicating suppressed electrolyte decomposition even at 70°C. Based on these results, the FDPO itself is thermally stable and also forms a thermally stable SEI on graphite, thereby suppressing capacity degradation under high-temperature conditions. In the presentation, the results of X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry analyses for the SEI derived from FDPO-based electrolytes, along with the charge-discharge performances of positive electrodes, will be discussed. References (1) Wang, A. et al., npj Computational Materials, 2018, 4, 15.(2) Lu, L. et al., J. Power Sources, 2013, 226, 272.(3) Yang, G. et al., RSC Adv, 2017, 7, 26052.(4) Kuang, S. et al., ACS Appl. Mater. Interfaces, 2022, 14, 19056-19066. Acknowledgment A part of this work was supported by JST GteX (JPMJGX23S3). Figure 1

High Charge-Discharge Performance of Stacking-Sequence Disordered SiC as Anode Material for Lithium-Ion Battery

Much attention has been paid on Si, SiO and the composites with graphite as anode materials for lithium-ion battery. The issue of huge volume change in lithiation and delithiation which leads the less reversible capacity retention is serious and most of the efforts to overcome it has been directed to insert any kinds of buffers including the mechanical into the negative electrode material. Another attractive candidate as the anode material is β-SiC. One of major problems to develop the semiconductive β-SiC as the anode material is the loss of conduction pass inside the materials just like Si and SiO. β-SiC possesses zinc blend type of cubic structure with regularly stacked three close packed layers.We found that stacking-sequence disordered SiC (SD-SiC), not the three dimensionally ordered crystal like cubic β-SiC, with amorphous carbon as conduction pass worked as the anode material with the high discharge capacity of 1490mAh/g-Si (or 1040mAh/g-SiC) at 50mA/g after 14 cycles in the half-cell with Li as the counter electrode. In this work, the synthesis of SD-SiC with amorphous carbon, the discharge rate property and the cycle performance in the half-cell will be described.

Printable Liquid Metal Electrodes for Lithium Ion Battery

Recent developments in the Internet of Things (IoT) technology led to research on flexible devices for next-generation wearable devices.[1,2] As devices advance, the Lithium ion batteries (LIBs) used to operate them are also being actively researched to make them flexible. The battery electrode contains a reaction layer and a current collector layer. Flexible battery electrodes, in which these layers are integrated, are fabricated in a single process, simplifying the electrode fabrication process. However, to date, integrated electrodes have lower conductivity than conventional two-layer electrodes, and the process that maintains conductivity has not been simplified. This study proposes a liquid metal electrode ink that simultaneously plays the role of the reaction and current collector layers with high conductivity and can be formed in a single process via printing(Figure 1 a, b, c). It employs a Gallium (Ga) alloy liquid metal with high conductivity and high deformability containing Ni powder added for viscosity adjustment,[3] embedded with Li4Ti5O12 (LTO) or Li2TiS3 (LTS) as active materials. These liquid metal electrodes have high electronic conductivity and can function as cathode and anode electrodes for lithium flexible batteries on various substrates such as polyethylene terephthalate (PET) and polypropylene (PP), which have insulating properties, by simply applying the material to the substrate without the need for solvent vaporization. In this study, we evaluated the printing characteristics of the developed liquid metal electrode and its electrochemical properties in a half-cell using a gel electrolyte as a separator with a Li foil as a reference electrode. As printing characteristics, the desired thickness can be controlled by screen printing at a film thickness of 50 μm or more (Fig. 2a), and patterns can be successfully printed by applying mask printing (Fig. 2b). This is effective for the future practical use of flexible batteries with multi-pixel electrodes. Fig. 2c indicates the results of laser microscope measurements of the surface of the printed liquid metal electrode (LTO), and Fig. 2d shows the results of elemental analysis using SEM-EDX. From these results, it was observed that Ga and Sn, which are liquid metal components, Ni from the added Ni powder, and Ti, which is a component of the active material LTO, are dispersed on the surface. As electrochemical characteristics, it was confirmed that the printed liquid metal electrode has conductivity of about 104 S cm-1, and can exhibit charge-discharge performance regardless of the conductivity of the substrate (Fig. 3a). In a demonstration using a PP cup, it was demonstrated that LEDs can be turned on as a power source by constructing liquid metal electrodes on a curved surface (Fig. 3b). In charge-discharge tests using laminated cells with a Li reference electrode, both LTO and liquid metal electrodes with LTS exhibited Coulomb efficiencies close to 100 % (Figure 3c). In a dynamic bending test using the fabricated laminated cell, the LEDs stably emitted light even when the cell was bent up and down from a flat state (Figure 3d). This demonstrates the robustness of the LEDs against deformation. The liquid metal electrode we have developed can be used directly for simple printing techniques, and is expected to be applied to complex construction using the dispensing method [4] and mass production technology by Roll-to-Roll printing [5] in the future. Our concept of fabricating new printable liquid metal electrodes by mixing active materials with liquid metal expands the possibilities of lithium-ion battery research, simplifies the LIB manufacturing process, and contributes to efficient electrode production methods in future LIBs.[1] T. Yokota, P. Zalar, M. Kaltenbrunner, H. Jinno, N. Matsuhisa, H. Kitanosako, Y. Tachibana, W. Yukita, M. Koizumi, T. Someya, Sci Adv 2016, 2, DOI 10.1126/sciadv.1501856[2] K. Takei, W. Honda, S. Harada, T. Arie, S. Akita, Adv Healthc Mater 2015, 4, 487.[3] M. D. Dickey, Advanced Materials 2017, 29, DOI 10.1002/adma.201606425.[4] A. Cook, D. P. Parekh, C. Ladd, G. Kotwal, L. Panich, M. Durstock, M. D. Dickey, C. E. Tabor, Adv Eng Mater 2019, 21, DOI 10.1002/adem.201900400.[5] R. Abbel, Y. Galagan, P. Groen, Adv Eng Mater 2018, 20, DOI 10.1002/adem.201701190. Figure 1

Elucidation of the Li Storage State and Dynamics in Various Carbon Electrodes by Using 7Li NMR

In recent years, both soft carbons and hard carbons have been considered as potential anode materials for lithium-ion batteries (LIBs) and lithium-ion capacitors (LICs) because of their high capacity and superior rate performance compared to graphite electrodes. To design high power carbon anode, revealing the Li storage state and dynamics in carbon electrodes is required. However, the effect of carbon microstructure on the Li storage state remains unclear because of the complex microstructures of these carbon materials, which consist of a mixture of graphitic and amorphous domains. 7Li NMR is a useful measurement to know the Li storage state because it provides direct observation of Li atoms in carbon microstructures and has the advantage of seeing the dynamics of Li without the process of de-solvation on the electrode-electrolyte interface, compared to electrochemical measurements. In this study, we investigated the Li storage state in soft and hard carbons with different graphitization degrees using 7Li NMR. We obtained information about the Li species, domain size of Li sites, and motion properties by comparing temperature-dependent NMR spectra and spin relaxation time.Graphite, soft carbon (SC), and hard carbon (HC), as well as their graphitized samples by heat treatment at 1500, 2000, and 2500°C, denoted as SCX or HCX (X: Heat treatment temperatures/°C, HTTs), were prepared. The crystallinity of the carbon materials was evaluated using X-ray diffraction (XRD). These carbon samples were electrochemically lithiated by applying a constant current of 50 mA/g to 0.002 V vs. Li/Li+, followed by keeping the potential until a cut-off current of 5 mA/g. The lithiated carbon samples were characterized using 7Li NMR spectroscopy and spin relaxation measurements at different temperatures (103-353 K). The Li self-diffusion coefficient in SC at 343 K was measured by pulsed gradient spin-echo (PGSE) NMR.The 7Li NMR spectrum of lithiated SC was assigned to Li in the turbostratic structure. As the SC heat-treatment temperature increased, the NMR spectra corresponding to the shrinkage of the carbon layer spacing were obtained. The Li in SC2500 was predominantly stored in a graphitic structure and partially in amorphous structures. On the other hand, the Li state in HC showed intercalated Li in the turbostratic layers and quasi-metallic Li clusters. As the HC heat-treatment temperature increased, the peak of quasi-metallic Li clusters disappeared, and the peak of Li in the turbostratic structures remained. Only HC2500 showed a small peak assigned to Li in the graphitic structure, indicating that HC2500 has a distinct graphitic layer structure, as measured by XRD. The average diffusional displacement in the measurement timescale was estimated to be approximately 1 nm below 200 K 1. The chemical exchange occurring at the temperature suggests that the domain size of the Li sites are a few nanometers.The spin-lattice relaxation time (T1) was measured at different temperatures, and the activation energy of each Li species for motion in carbon electrodes were estimated. Li species intercalated in the turbostratic layers indicated similar activation energy for all amorphous carbons, providing an evidence that these Li species in various carbon electrodes have similar restriction and motion properties. Li in graphitic structures on HC2500 showed higher activation energy than amorphous structures and is considered unsuitable for high-rate charge-discharge performance. Y. Fang, K. Peuvot, A. Gratrex, E. V. Morozov, J. Hagberg, G. Lindbergh, and I. Furó, J. Mater. Chem. A, 10, 10069–10082 (2022). Figure 1

Improvement of LiNi0.8Co0.1Mn0.1O2 Positive-Electrode Properties by Introducing Fluorinated Propionic Acid Ester-Based Solvent to Highly Concentrated Lin(SO2F)2 Electrolyte Solutions

IntroductionFurther improvement in energy density and safety of lithium-ion batteries is required to expand the spread of EVs. A LiNi0.8Co0.1Mn0.1O2 (NCM811) positive-electrode is drawing attention because it can deliver a high discharge capacity of about 220 mAh g-1 or more by raising the charging upper limit potential to 4.6 V (vs. Li/Li+). In general, however, the electrolyte solution is oxidized and decomposed at about 4 V (vs. Li/Li+) or more, and cracks of the NCM811 particles occur, which results in a significant decrease in charge and discharge performance. Accordingly, highly concentrated electrolyte solutions are attracting attention because of their high stability against oxidation and thermal stability1, while the problem is that the viscosity is high and the ion conductivity is low.In this study, flame-retardant tris (2,2,2-trifluoroethyl) phosphate (TFEP)-based electrolyte solutions containing high concentrations of LiN(SO2F)2 (LiFSI) were prepared, and methyl 2,3,3,3-tetrafluoropropionate (4FMP) as a co-solvent and methyl perfluoropropionate (5FMP) as a diluent were introduced to reduce the viscosity and improve the ion conductivity. The charge-discharge characteristics of NCM811 positive-electrodes were investigated by conducting charge-discharge tests over 100 cycles in a voltage range of 3.0-4.6 V using a half-cell with an NCM811 working electrode and a lithium metal counter electrode.ExperimentalThe nearly saturated 2.2 M LiFSI/TFEP (TFEP/Li+=1.7 by mol) electrolyte solution, and the highly concentrated LiFSI/TFEP+4FMP (TFEP:4FMP=1:1 and 2:1 by vol.) and LiFSI/TFEP+5FMP (TFEP/Li+=1.7 by mol, TFEP:5FMP=1:1, 2:1 and 3:1 by vol.) electrolyte solutions were prepared. An NCM811 composite electrode (13 mmf) was used as a working electrode and a Li foil (14 mmf) was used as a counter electrode, and each electrolyte solution was used to prepare a Li|NCM811 cell. Charge-discharge tests were conducted between 3.0 and 4.6 V. The charge/discharge rate in the first cycle was set to C/10, which corresponds to a current that can theoretically complete each charge (discharge) process in 10 h under the presumption that the theoretical specific capacity of NCM811 is 278 mAh/g. In addition, the NCM811 working electrode after 100 cycles was washed with dimethyl carbonate, dried, and then analyzed by a field emission scanning electron microscope (FE-SEM)/energy dispersive X-ray spectroscopy (EDX). To evaluate the oxidation resistance of the electrolyte solutions, linear sweep voltammetry (LSV) was performed by using three-electrode cell having a Pt working electrode (12 mmf).Results and DiscussionFigure 1 shows the changes in discharge capacity of Li|NCM811 cells in 100 cycles. 2.1 M LiFSI/TFEP+4FMP (TFEP: 4FMP=2:1 by vol., (TFEP+4FMP)/Li+=2.3 by mol., 4FMP electrolyte) and 1.6 M LiFSI/TFEP+5FMP (TFEP: 5FMP=2:1 by vol., 5FMP-diluted electrolyte) showed the highest performance among the 4FMP- and 5FMP-diluted electrolyte solutions, respectively. After 100 cycles, the discharge capacity retention was 92.5% and 93.1% in the 4FMP- and 5FMP-diluted electrolytes, respectively. In addition, the average Coulomb efficiency reached 99.0% and 99.3%, respectively. The 4FMP electrolyte showed the highest discharge capacity in the 100th cycle (209.0 mAh/g), and the 5FMP-diluted electrolyte showed the highest discharge capacity retention and average Coulomb efficiency. After the 100 charge-discharge cycles, the F atomic concentrations on the surface of NCM811 were 11.6% and 10.1% in 4FMP- and 5FMP-diluted electrolytes, respectively, which was the lowest among the 4FMP and 5FMP-diluted electrolyte solutions. LSV of Pt showed a large anodic current due to the oxidative decomposition of the 4FMP electrolyte, suggesting that the charge-discharge performance of NCM811 is improved by forming a thin and uniform protective film on it. On the other hand, since the oxidation decomposition current of the 5FMP-diluted electrolyte was kept at the lowest level, the charge-discharge performance of NCM811 should be improved by the high stability against oxidation of the electrolyte solution. Figure 1

Polysaccharide-Based Hydrogel Electrolyte Membranes for Quasi-Solid-State Rechargeable Alkaline Zinc Batteries

Introduction Rechargeable zinc battery is a promising energy device because of its advantages such as high safety, low cost, environmental friendliness etc. However, the reduction in discharge capacity due to hydrogen evolution reaction and short circuits caused by dendrite growth during charging hinder the practical application of rechargeable zinc battery. We have demonstrated the effectiveness of crosslinked polyacrylate-based hydrogel electrolytes (HEs) as an alternative to aqueous alkaline solutions to improve these issues.1 We have recently become interested in physical gels in which the host polymer is cross-linked by intermolecular interactions such as hydrogen bonding and ionic bonding, and prepared new HEs by mixing xanthan gum (XG), one of polysaccharides, as host polymer and aqueous KOH solutions. The XG-based HEs showed ionic conductivity comparable to the corresponding alkaline aqueous solutions. However, we have not succeeded in producing self-standing XG-based HE membranes under alkaline conditions yet. In this study, we have used another polysaccharide, starch, to prepare and characterize self-standing HE membranes under alkaline conditions. Moreover, we fabricated quasi-solid-state Zn/HE/positive electrode cell and evaluated charge-discharge performances. Experimental Commercial starch powder was mixed with (4 M KOH-0.3 M ZnO) aqueous solution with stirring to obtain a homogeneous sol, and then dried to prepare starch-based HE. The prepared starch-based HE membrane was soaked in the electrolyte solution before fabricating cells. Results and Discussion The photos of prepared starch-based HE membrane are shown in Fig. 1. As can be seen from these figures, the HE membrane was able to stretch and contract without tearing, suggesting that it exhibited high physical strength. The ionic conductivity of the HE membrane was a little lower than that of electrolyte solution. Using a Cu/HE membrane/Zn cell, the redox waves due to Zn deposition/dissolution at a Cu electrode were observed by cyclic voltammetry. Charge-discharge measurements using a Zn/HE membrane/Zn symmetrical cell showed an overpotential of about 50 mV for Zn deposition/dissolution, which was almost the same as a cell using a (4 M KOH-0.3 M ZnO) aqueous solution. In charge-discharge test using a γ-MnO2/HE membrane/Zn cell at 2 C-rate between 0.8 and 1.8 V, the initial discharge capacity was 253 mAh g-1, which was ca. 82 % of the theoretical capacity. However, the discharge capacity decreased to ca. 70 mAh g-1 by the 50th cycle.This work is based on results obtained from a project, JPNP21006, commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Reference C. Iwakura, H. Murakami, S. Nohara, N. Furukawa, H. Inoue, J. Power Sources, 152, 291 (2005). Figure 1

Synthesis, Characterization, and Lib Cell Performance of Chemically-Derived Pure Crystalline Fullerene C60

Buckminsterfullerene (C60), as an allotrope of carbon, is regarded as a potential anode material for lithium-ion batteries(LIBs). However, the poor crystallinity, low electrochemical reaction activity, and poor reversibility of lithium storage of C60 make it challenging to design efficient anode materials, and the relevant electrochemical reaction mechanisms still require in-depth study. Currently, many researches have been devoted to polymerized C60 and further modification through doping, hybridization, and derivatization to obtain high-performance C60-based anode materials. However, application of high crystallinity C60 nanomaterials in the anode materials of LIBs is rarely reported. Nanocarbon materials have high specific surface area, which can provide more lithium storage sites for lithium ions, shorten the transmission path of lithium ions, and make the diffusion and deintercalation of lithium ions in electrode materials faster. At the same time, nanocarbon materials have excellent conductivity which can increase the electron transfer rate in carbon materials, thereby improving the charge -discharge performance and cycle stability of the battery. Therefore, the development of C60 nanomaterials with high crystallinity and regular morphology as anode materials is extremely attractive and profound.In this work, one-dimensional C60 nanorods(C60 NRs) with regular shape and high crystallinity were prepared through liquid-liquid interface precipitation(LLIP) method and low-temperature annealing process, to be served as anode material of LIBs. 1 M LiPF6 solution in ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1 vol%) with 10% fluoroethylene carbonate (FEC) was used as electrolyte. Electrochemical performance tests show that C60 NRs is a high-rate performance and long-cycle life anode material for LIBs. Maintaining a discharge-specific capacity of 603 mAh g−1 after 2,000 cycles at a current density of 2 A g−1. Even at a high current density of 10 A g−1, C60 NRs could still achieve a discharge-specific capacity of 228 mAh g−1 after 5,000 cycles. The chemical changes of the electrode surface components and the SEI layer formation mechanism during the electrochemical reaction were explored through XPS experiments. The results confirmed the reversible storage of lithium ions and the existence of inorganic components such as LiF, Li2CO3, Li2O and oligomer based organic materials in SEI film. All account for the excellent charge-discharge performance and cycle stability of C60 NRs anode. Furthermore, Galvanostatic intermittent titration technique(GITT) and potentiostat intermittent titration technique(PITT) tests were conducted to calculate diffusion coefficient of lithium ion during charge-discharge process, the obtained high diffusion coefficient demonstrated fast lithium diffusion and stable cycle performance of C60 NRs anode. This work proved the feasibility of C60 nanomaterials as high-performance energy storage anode materials and will help to promote the design of new C60-based nanomaterials for LIBs.This research was supported by the NRF funded by the MSIT and MEST (grant numbers NRF-2021R1A4A1022198, NRF-2022R1A2B5B01001943, and NRF-2018R1A5A1025594). Figure 1

Development of High-Areal-Capacity Electrodes for Sulfide-Based All-Solid-State Batteries

All-solid-state batteries using sulfide-based solid electrolytes with high lithium-ion conductivity equivalent to that of organic electrolyte solution are attracting attention as a next-generation battery with excellent safety. The sulfide-based all-solid-state batteries are especially expected to be used as a power source for electric vehicles, and high-capacity batteries are needed to realize such applications. Increasing in the areal capacity of the electrode by increasing the thickness of the electrode is one of the effective approaches to increasing the capacity of the batteries. Coating metal foils with slurry containing binders used in the fabrication of electrodes for the conventional electrolyte-solution-based lithium-ion batteries is effective for mass production processes, but it causes cracking and delamination in the coating layer when the electrode is made too thick. In addition, the addition of binder to the slurry increases the internal resistance of the battery resulting in lower battery performance. In this study, we developed a fabrication technique for the binder-free and a high areal capacity electrode by vacuum filtration of a slurry containing carbon nanotubes (CNTs) in order to realize high-capacity sulfide-based all-solid-state batteries, and evaluated the charge-discharge performance of the cell. Lithium nickel cobalt manganese oxide (LiNi0.5Co0.2Mn0.3O2, NCM) and artificial graphite (Gr) were used as active materials for the cathode and anode, respectively, and a slurry was prepared by mixing them with an argyrodite-type sulfide solid electrolyte (SE, A-SOLiD®, Mitsui Mining & Smelting Co., Ltd.) and CNTs. The slurry was vacuum filtered and then vacuum dried to obtain cathode and anode. The NCM cathode with a high areal capacity of 4 mAh cm-2 without cracking was obtained by vacuum filtration of the CNT-containing slurry, although it contained no binder. As with the cathode, the Gr anode was also crack-free and had a high areal capacity of 5 mAh cm-2. The NCM cathode and Gr anode thus obtained and the solid electrolyte sheets prepared using the argyrodite-type sulfide solid electrolyte were punched to 13 mm and 14 mm diameters, respectively. A full cell of NCM cathode/SE sheet/Gr anode was fabricated by pressing these staked materials, and the cell performance was evaluated in a coin cell (CR2032 type). The full-cell consisting of NCM cathode and Gr anode prepared by vacuum filtration of CNT-containing slurry showed a stable cycling performance of over 50 cycles.

Ion Transport and Solution Behavior of Polyanion-Type Li Salts in Nonaqueous Solvents

To achieve fast charging and discharging of Li-ion batteries, it is important to improve the ionic conductivity (σ) of the electrolyte as well as the Li-ion transference number (t Li) [1]. While nonaqueous polyelectrolyte solutions exhibit high Li-ion transference number(t Li = 0.81) upon immobilization of the anion on a polymer backbone, the ionic conductivity (σ = 1.3 mS cm-1) is inferior to that of conventional electrolytes (σ ~10 mS cm-1). One of the reasons for the low ionic conductivity is low dissociation degree caused by the counter-ion condensation on the polymer backbone. To gain an insight into a design strategy of polyelectrolyte-based liquid electrolytes for LIBs, we studied the effects of polyelectrolyte structure and solvent polarity on the transport properties and Li-ion solvation of the polyelectrolytes in carbonate solvents. Here, we employed two polyelectrolyte copolymers with different sequences; random copolymers of the Li salt of a weakly coordinating polyanion, poly[(4-styrenesulfonyl)-(trifluoromethanesulfonyl)amide] (poly(LiSTFSA)) with neutral comonomer unit, and poly[(4-maleimide-N-[(trifluoromethyl)sulfonyl]-benzenesulfonamide lithium salt] (poly(sa-PMI))-based alternating copolymers with neutral comonomer unit. For the random copolymers, the ionic conductivity increased as the ratio of the neutral comonomer increased. This was attributed to the suppression of counter-ion condensation and increased dissociation. The alternating copolymer solution showed higher dissociation than the random copolymers. The highest ionic conductivity was unexpectedly observed for the lowest polar mixture (such as a dimethyl carbonate rich mixture) at the highest salt concentration despite the low dissociation degree of the polyelectrolytes. A unique conduction resulting from the faster diffusion of transiently solvated Li ions along the interconnected aggregates of polyanion chains was suggested in the highly concentrated polyelectrolyte solutions in low polar solvents. A Li/LiFePO4 cell using the polyelectrolyte solution demonstrated a good charge-discharge performance and rate capability[2].

Bacterial Cellulose/Polyelectrolyte Complex Hydrogel Separator with Thermal and Dimensional Stabilities for Dendrite Suppression in Zinc Ion Battery.

In this study, bacterial cellulose-polyelectrolyte complex (BC/PEC) composite hydrogels were prepared for an electrode separator. First, the poly(sodium 4-styrenesulfonate)/poly(dimethyl diallyl ammonium chloride) hydrogel was prepared using NaCl as a shielding agent and a dialysis tube to control the formation of the PEC hydrogel. BC was incorporated into the supporting skeleton. The 3D BC sponge was prepared by using an alkali swollen BC gel, followed by freeze-thaw cycles to develop the porous framework. The BC backbone was then cross-linked with glutaraldehyde (GA) under acidic conditions to obtain cross-linked BC (BC-GA), resulting in the improved dimensional stability of the BC skeleton in an alkali medium. Subsequently, the PEC was introduced into the BC-GA pores, resulting in the BC-GA/PEC composite hydrogel with improved mechanical and dimensional properties and thermal stability. Electrolyte permeability tests with 6 M KOH showed that BC/PEC had lower permeability (approximately 2 × 10-2 cm2/min) compared to BC and BC-GA (1.0-1.5 × 10-1 cm2/min) compared to the ionic conductivity of BC-GA/PEC with values of 30.9-55.9 mS/cm. The charge-discharge cycling performance of BC-GA/PEC hydrogels as a zinc battery separator was evaluated using plating/stripping tests, revealing that the zinc anode surface exhibited less corrosion and slower dendrite growth. This phenomenon was due to the decrease in Zn2+ crossover by either repulsion or attraction forces between Zn2+ and BC-GA/PEC hydrogels, making them an alternative for electrode separators in place of liquid electrolyte separators.

Enhanced energy storage performance of lead-free Sr0.7Bi0.2TiO3 ceramics via tape casting

Abstract The development of pulsed power technology demands high energy storage density dielectric materials. In this study, Sr0.7Bi0.2TiO3 relaxor ferroelectric (rFE) ceramic thick films were prepared using a tape-casting process. The ceramics exhibit a dense structure and typical rFE hysteresis curves, achieving an energy storage density of 4.77 J cm−3 and efficiency of 94.4%, attributed to the high polarization intensity, low remnant polarization, and low hysteresis loss of rFE. Additionally, the material demonstrates good temperature stability. Moreover, the Sr0.7Bi0.2TiO3 ceramic thick films show advantages in charge-discharge performance, capable of discharging within hundreds of nanoseconds and achieving a power density of 137 MW cm−3. Overall, the Sr0.7Bi0.2TiO3 ceramic thick film exhibits a comprehensive performance advantage in terms of energy storage density, efficiency, and power density. Additionally, the material was fabricated using the tape-casting process, which is compatible with subsequent multilayer ceramic capacitor production, indicating potential for further performance enhancement.

Research Progress and Challenges of Carbon/MXene Composites for Supercapacitors

Carbon materials/MXenes composite materials have gained widespread attention in the field of supercapacitors due to their excellent electrochemical performance. Carbon materials are considered ideal electrode materials for supercapacitors due to their high specific surface area, good conductivity, and outstanding electrochemical stability. MXenes, as a novel two-dimensional material, exhibit prominent conductivity, mechanical properties, and ionic conductivity, thereby showing great potential for applications in energy storage devices. The combination of carbon materials and MXenes is expected to fully leverage the advantages of both, optimizing electrode conductivity, enhancing the energy density and power density, and improving the charge–discharge performance. This article reviews the key research progress of carbon/MXenes composite materials in supercapacitors in recent years, including their synthesis methods, structural tuning, and improvements in their electrochemical performance. Finally, the article looks forward to future research directions and proposes potential strategies to enhance the overall performance of the composite materials and achieve large-scale applications. By addressing the existing challenges, carbon/MXenes composite materials are anticipated to achieve higher energy and power outputs for the supercapacitor field in the future, providing strong support for the development of new energy storage technologies such as electric vehicles and wearable devices.