Charge-discharge Process Research Articles

Enabling High-Voltage and Long Lifespan Sodium Batteries via Single-Crystal Layer-Structured Oxide Cathode Material.

Manganese-based layer-structured transition metal oxides are considered promising cathode materials for future sodium batteries owing to their high energy density potential and industrial feasibility. The grain-related anisotropy and electrode/electrolyte side reactions, however, constrain their energy density and cycling lifespan, particularly at high voltages. Large-sized single-crystal O3-typed Na[Ni0.3Mn0.5Cu0.1Ti0.1]O2 was thus designed and successfully synthesized toward high-voltage and long-lifespan sodium batteries. The grain-boundary-free single-crystal structure and unidirectional Na+ diffusion channels enable a faster Na+ diffusion rate and high electronic conductivity. Meanwhile, the large-area exposed (003) crystal plane can not only exhibit a higher energy barrier for electrode-electrolyte side reactions but also alleviate the interlayer sliding and structural collapse during charge-discharge processes. The lattice oxygen in contact with the electrolyte was stabilized, and the TMO6 octahedral structure integrity was maintained as well. A high specific capacity of 160.1 mAh g-1 at a current density of 0.1 C was demonstrated. Coupled with hard carbon as the anode, the full cell can also demonstrate an excellent capacity and cycling stability, achieving a high specific capacity of 141.1 mAh g-1 at 0.1 C. After 100 cycles at 2 C, the capacity retention rate is 97.3%.

Research Progress of Silicon/Carbon Anodes in Lithium-Ion Batteries

Lithium-ion batteries (LIBs) have garnered attention because of their high energy density and lightweight properties. However, LIBs typically use graphite for the anode material, which shows a relatively low specific capacity that can hardly meet the growing energy storage demands. Compared with traditional graphite anodes, silicon anodes have already been proven to possess higher specific capacities. Additionally, silicon is abundant and relatively inexpensive. Nonetheless, silicon anodes undergo significant volume expansion during the charge-discharge process, generating mechanical stress that can lead to potential cracking and capacity loss. Moreover, they exhibit relatively low initial coulombic efficiency, causing a considerable amount of lithium to be irreversibly consumed during the initial cycles. To address these issues, various nanotechnology-based strategies have been developed, including silicon/carbon (Si/C) composite anodes and the development of other nanostructured materials. These approaches aim to optimize interface structure, particle structure, and composite structure design to enhance battery performance and durability. This paper provides a comprehensive review of the application of nanotechnology in silicon anodes, focusing on the advancements in silicon/carbon composites and their effects on mitigating volume expansion, improving initial coulombic efficiency, and maintaining capacity retention. Additionally, it analyzes the impact of different nanostructure designs on battery performance.

Studies on Multifunctional Nanostructured Materials

Multifunctional materials are of today’s quest. Miniaturization, i.e. development of these materials in the form of nanomaterials is of primary need considering their application in devices. Moreover, if these are obtained in nanostructured form, they can bring wonders. We have adopted a method for developing multiferroic BiFeO3 (BFO) with simultaneous antiferromagnetic, ferroelectric & ferroelastic behaviour in form of nanostructures like nanorods, nanowire etc. by employing Anodised Alumina (AAO) template with various pore sizes from 20nm with solution route followed by controlled vacuum filtration and sintering. Diameters of nanorods are in the range of 20-100 nm as observed by FESEM. Capacitance assayed by cyclic voltammetry (CV) and charge discharge processes reveals a very high value of specific capacitance of 450F/gm. Capacitance has been estimated by extrapolating the charge collected at the electrode to that at scanning rate of infinity which is relevant for the charge collected at the nanorods protruding out of the template. Charging and discharging times are quite constant over a large number of cycles. This large value of specific capacitance can be attributed to the nanostructure form of BFO nanorod. The high value of specific capacitance of BFO nanorods brings forth its use as electrode in storage energy devices. Also, a high value of polarization as well as a significant magnetic susceptibility are observed in multiferroic Bismuth Ferrite (BFO) in the form of nanorods protruding out. The high values of polarization and magnetic susceptibility are attributed to the structured form of BFO nanorods giving rise to the directionality. There is no leakage current in P-E loop examined at various fields and frequencies. Magnetocapacitance measurements reflect a significant enhancement in magnetoelectric coupling also.

Exploring the Enhanced Zinc Storage Performance of α-MnSe Polyhedral Microspheres and H+/Zn2+ Co-Insertion Mechanism.

The newly emerged Mn-based selenides as cathodes for aqueous Zn-ion batteries (ZIBs) have drawn researchers' interest because of their lower electronegativity and better electronic conductivity compared with the corresponding Mn-based oxides. Nevertheless, the energy storage mechanism of Mn-based selenides still needs to be further clarified. Herein, the MnSe/Se and MnSe polyhedral microspheres are reported as cathodes for ZIBs, and the MnSe cathode achieves significantly enhanced specific capacity, rate performance, and cycling stability. In-depth kinetic analysis confirms that the MnSe cathode presents better kinetic behavior and density functional theory (DFT) calculations verify the fast diffusion kinetics of the MnSe cathode. More importantly, systematic ex situ characterizations reveal that the microstructured MnSe can exist stably during the charge-discharge process and store energy with H+/Zn2+ co-insertion mechanism, which is greatly different from the phase transformation of the nanostructured α-MnSe reported in the literature. Additionally, it is verified that the different types of separators exhibit remarkably different zinc storage performance of the MnSe cathode. This study not only offers a good guidance for developing high-performance ZIBs Mn-based cathode materials and explores the effect of separators on the zinc storage performance, but also provides new insights into the energy storage mechanism of the MnSe cathode.

Iron complex with multiple negative charges ligand for ultrahigh stability and high energy density alkaline all-iron flow battery

Alkaline all-iron flow batteries (AIFBs) are highly attractive for large-scale and long-term energy storage due to the abundant availability of raw materials, low cost, inherent safety, and decoupling of capacity and power. However, a stable iron anolyte is still being explored to address complex decomposition, ligand crossover, and energy density to improve battery performance. Herein, a promising metal-organic complex, Fe(NTHPS), consisting of FeCl3 and 3,3',3''-nitrilotris(2-hydroxypropane-1-sulfonate) (NTHPS), is specifically designed for alkaline all-iron flow battery. The NTHPS exhibits strong binding strength with iron ions, resulting in ultrahigh stability during the charge-discharge process. AIFB based on the [Fe(CN)6]4- catholyte and Fe(NTHPS) showcases an exceptionally high capacity retention of 97.8% after 2000 cycles (0.0011% per cycle), maintaining high coulombic efficiency near 100%. Furthermore, with a solubility as high as 1.82 mol L-1, the Fe(NTHPS) anolyte demonstrates an ultra-high theoretical capacity of 47.23 Ah L-1. This multiple negative charges ligand not only resolves existing barrier associated with AIFBs, but also provides valuable insight for their commercial application.

Incorporating MXene with Redox Carriers on Capacitive Carbon Cloth-Based Freestanding Electrodes for Power Applications

Abstract Battery-like organic materials including quinone-based electrodes with electrochemical activity have been extensively investigated for their use as electrode materials in energy storage devices due to their economic competitiveness and sustainable benefits. However, the intrinsic electrical insulating nature of organic quinones and their electrochemical reactivity limit power capability and stability upon charge/discharge cycling, respectively. Here, we report the preparation of a concentric layered architecture, MXene/Anthraquinone/Carbon Cloth (M/AQ/CC), by physisorption of anthraquinone onto the surface of carbon cloth via non-covalent π–π interactions, followed by dipping in exfoliated MXene suspension. The M/AQ/CC electrode, with a high mass loading (18.2 mg cm-2), delivered a capacity of 46 mAh g-1 (about 1 mAh cm-2 areal capacity or 6 mAh mL-1 volume) at 0.5 A g-1, with good rate performance and an enhanced cyclability over 5k cycles. This simple preparation method can also be applied to incorporate MXene with a series of alternative organic redox carriers on freestanding carbon cloth, including thionin acetate and anthraquinone-2-sulfonate. The improvement in electrochemical performance highlights an efficient approach to store more charges via redox reactions from organic quinones pi-stacked at carbon surfaces, thanks to a protective MXene shield that stabilizes the Faradaic behavior of quinones over repetitive charge-discharge processes. The simplicity and versatility of this method should enable design of many advanced electrode materials based on MXene/quinones/carbon cloth for power devices

Investigation of Stable Structures, Electronic States and Mechanism of Mg Intercalation of MgCo2−ZNi0.5MnAlzO4 (z = 0, 0.3) during Charge and Discharge Process as Cathode Materials for Magnesium Rechargeable Batteries Using First-Principles Calculations

Introduction In recent years, clean energy materials such as storage battery materials have been attracting attention in order to reduce greenhouse gas emissions. Li ion batteries (LIB) are already widely used as batteries for laptop and smartphones. However, Li metal is expensive and new storage battery materials with higher volumetric energy density are needed to be developed for application in large power supplies. Therefore, storage battery materials using Mg metal with divalent ions are currently attracting attention. Our group has been developing spinel Mg-(Co, Ni, Mn, Al)2-O4 cathode materials with three-dimensional diffusion pathways1). Spinel MgCo2-zNi0.5MnAlzO4 (z=0, 0.3) were synthesized and electrochemical tests revealed that the Al substituted material has particularly improved battery properties. Furthermore, the stable structure and electronic state of pristine MgCo2-zNi0.5MnAlzO4 (z=0, 0.3) were calculated using first principles calculations to clarify the effect of substituted species2). The results predicted that the Mg-O bonding around Al was specifically weakened, allowing Mg to diffuse easily move the crystal. In this study, we clarify the stable structure of spinel MgCo2-zNi0.5MnAlzO4 (z=0, 0.3) after discharge and charge, and clarify the electronic structure and the mechanism of Mg intercalation during charge and discharge processes. Calculation The structural relaxation calculation was performed by generalized gradient approximation (GGA) exchange-correlation potential used with a plane-wave cutoff energy of 550 eV, and 1×2×2 k-point mesh was applied, corresponding to the inverses of the lattice constants on Vienna Ab-initio Simulation Package (VASP) code. The convergence criterion for structural optimization for pristine model and during discharge and charge models was that the energy difference per iteration be less than or equal to 0.02 eV/Å. 2×1×1 supercell was created and structural relaxation calculation was performed. Result and discussion In this study, the stable structure of MgCo2-zNi0.5MnAlzO4 (z=0.3) during discharge was first obtained from the stable pristine structure. Figure 1 a) and b) show the stable structures of pristine and discharge model obtained by structural relaxation calculation, respectively. Fig. 1 b) is the stable structure after discharge in which Mg atoms are inserted into the vacancy 16c site in the stable pristine structure shown in a) (Mg insertion amount is 0.375). After insertion of Mg, the atoms on the 8a site move into the direction of the arrow in shown in b) to vacant 16c site, resulting in a vacancy at the 8a site. It is clear that the structural change from a spinel type structure to a rocksalt type structure partially occurs during the discharge.Therefore, we further show in Fig. 1 c) the stable structure of z=0.3 after charging in which the same amount of Mg insertion on the 16c site in the stable structure during discharge shown in b) is desorbed. After structural relaxation, Mg atoms on 16c site indicated by the dashed circle migrates to vacant 8a site during charge. During charging, it is apparent that the partial rock-salt type structure reverses to spinel type due to the desorption of Mg. The desorption of Mg from the 16c sites around the 8a vacancy site reduces the repulsion between cations, allowing the remaining 16c site Mg to move to the 8a site and return to the spinel type structure. Therefore, if a large structural change occurs during discharge, in which Mg insertion increases and almost all 8a site Mg becomes vacancies, it is not possible to return to the spinel type structure during charging. However, some 8a sites remain vacant in Fig. 1 c). When Co with cation mixing on the 8a site moves to the 16c site during discharge, Co cannot move to vacant 8a site because the bond between Co-O is much stronger than the bond between Mg-O. Therefore, it is clear that the Co influence at the 16c site also prevents the adjacent Mg from migrating to the 8a site, resulting in vacancies. Therefore, it is clear that due to the influence of Co at the 16c site, Mg adjacent to Co also cannot migrate to the 8a site. The cation mixing between Mg and transition metals is suppressed, and the change to a rocksalt type structure during discharge is suppressed during the charge-discharge process. Acknowledgement This research was financially supported by JST, GteX Program Grant Number JPMJGX23S1, Japan.1) Y. Hirata, Y. Idemoto et al., ECS Meeting s, MA2020-02 , 3451 (2020)2) C. Ishibashi, R. Takeuchi, N. Kitamura, Y. Idemoto, J. Phys. Chem. C., 127, 10470-10489 (2023). 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

Cathode Properties Crystal and Electronic Structures of αLi2MnO3-(1-α)Li(Mn10/24Ni7/24Co7/24)O2 in Li Ion Batteries with TiNb2O7 anode

IntroductionLithium ion batteries (LIBs) are currently used in many small devices due to their high energy density. The solid solution material αLi2MnO3-(1-α)Li(Mn10/24Ni7/24Co7/24)O2 (α = 0.5, 0.4) has attracted attention as a cathode material because it exhibits high energy density and high capacity of 200 mAh/g or more when charged to 4.6 V vs. Li/Li+ or higher. However, there are some problems such as irreversible capacity due to oxygen desorption during initial charging and degradation of cycle characteristics. In our previous research, Li metal has been used for the anode1). However, it is desirable to develop a new oxide anode material with high safety and high capacity for practical use. In this study, we focused on αLi2MnO3-(1-α)Li(Mn10/24Ni7/24Co7/24)O2 cathode and used TiNb2O7 (TNO) anode2), which is one of the candidates for an anode material, in addition to Li metal to evaluate battery characteristics of LIB. In addition, the purpose of this study was to investigate the relationship between battery properties and changes in average and electronic structure due to different anodes by examining the changes in average and electronic structure during the charge-discharge process. ExperimentsαLi2MnO3-(1-α)Li(Mn10/24Ni7/24Co7/24)O2 (α = 0.5 and 0.4) were synthesized by a coprecipitation method. The precursor was obtained by adding 1 mol/L of each metal nitrate to lithium hydroxide monohydrate dissolved in distilled water and then drying the precipitate. Lithium hydroxide monohydrate corresponding to the amount of lithium deficient in the precursor was added, and the samples were obtained by calcining (600°C, Air, 15 h) and firing (950°C, Air, 15 h). The obtained samples were subjected to powder X-ray diffraction to identify the phases and ICP to determine the metal composition. Charge-discharge tests using Li metal as the anode (2.0~4.8 V vs. Li/Li+, 0.1C) and TNO as the anode (0~3.3 V, 0.1C) were conducted using an HS cell to investigate battery characteristics. The powder before charging and discharging and after 5 cycles of charging and discharging of these batteries were analyzed by synchrotron X-ray diffraction measurements (BL19B2, SPring-8) and neutron diffraction measurements (iMATERIA, J-PARC) using Rietveld method (RIETAN-FP, Z-Code) for average structure analysis. In addition, electronic and local structures were analyzed by XAFS (BL14B2, SPring-8). The battery characteristics and changes in average and electronic structure after charge-discharge were discussed for the batteries using TNO and Li as anode. Results and DiscussionThe sample was synthesized by the coprecipitation method, and the phase was identified by powder X-ray diffraction measurement, and it was found to have a monoclinic C2/m structure. The composition was confirmed to be controlled by ICP measurement. From the results of charge-discharge tests, it was indicated that when the anode was TNO, the capacities of the samples with α = 0.5 and 0.4 tended to increase with the number of cycles in both cases. In order to clarify the cause of this, synchrotron X-ray diffraction measurements were performed to analyze the crystal structures. The samples with α=0.5 and 0.4 were also analyzed using Rietveld analysis to determine the average structures after discharge (Fig.1). The results showed mixing of Ni in the samples. The crystal structures were examined in detail by comparing the distortion parameters calculated by the metal-oxygen bond lengths and bond angles, and by calculating the BVS. As a result, it was found that an increase in distortion due to discharge was observed. Furthermore, XAFS was used to examine the relationship between the battery properties and the electronic and local structures before and after charging and discharging. References1) Y. Kiribayashi, N. Ishida, N. Kitamura, Y. Idemoto, s of the 59th Battery Symposium, 1C13 (2018).2)N. Takami, et al., J. Power Sources, 396, 429-436 (2018) Figure 1

Development of a Resilient Binder for Stable Cycling of High Sulfur Loading Lithium-Sulfur Batteries

Lithium-sulfur battery (LSB) is considered one of the most promising alternatives to modern lithium-ion batteries (LIBs) due to its high theoretical energy density (2600 Wh kg–1) – five times higher than that of LIBs. Despite its high theoretical energy density, the path to deployment of LSBs has not been paved due to its poor cycle life. One of the root causes of capacity decay in LSBs is the significant volume change of sulfur during lithiation and delithiation, which results in severe structural damage, thus cathode degradation and capacity loss. Such an effect is amplified in electrodes with high sulfur loadings, which typically involve thicker electrodes.Over the years, a substantial number of studies have reported various approaches to address the challenges in LSBs. Novel structural sulfur hosts are predominantly used to accommodate sulfur volume expansion. However, the excessive hollow spaces in those host structures decrease the practical energy density of sulfur cathode. Therefore, other approaches to improve mechanical integrity of sulfur cathode during lithiation-delithiation cycles, without compromising the LSB energy density is imperative.Binder plays a critical role in sulfur cathode by glueing the active material and conductive carbon together and to the current collector and thereby, maintaining the mechanical framework of the electrode.1 Accordingly, modifying binders to provide desired structural and mechanical characteristics is a promising approach to enhance longevity of LSBs, while preserving the high energy density of the battery. PVDF is a widely used binder in battery electrodes, due to its excellent chemical, electrochemical, and thermal stability in wide ranges of voltage and temperature. However, its adhesive properties are insufficient to withstand the significant stresses that highly loaded sulfur cathodes experience during both the electrode preparation (due to shrinkage of thick electrode film after slurry deposition), and battery cycling (due to volume variation of sulfur). These stresses further result in the formation of cracks and subsequently an increase in electrode impedance and ultimately, cell failure.2 Among various approaches to alleviate the insufficient adhesion and mechanical properties of PVDF, crosslinking is considered a potential solution. Cross-linked PVDF can provide a more stable framework for the active material and conductive agents through a covalently bonded 3D nanonet structure. To date, electromagnetic beam radiation has been the most common technique to crosslink PVDF.3,4 However, crosslinking through radiation is impractical for batteries on an industrial scale due to its complicated, expensive, and safety-demanding process. On the contrary, chemical methods can be simple and scalable, thus are highly preferred to cross-link PVDF for battery electrodes. However, cross-linking PVDF through chemical methods is known to be challenging due to its high thermal stability, which requires temperatures above 250°C for its effective cross-linkage. This is while most chemical crosslinking agents are unstable at such high temperatures. To the best of our knowledge, there has been no report on cross-linking PVDF through simple and scalable chemical methods for battery applications. In this work we present a simple chemical process in solution phase at room temperature for rapid crosslinking of PVDF, making it a promising method to produce crosslinked PVDF binder for high sulfur loading cathodes. Through this method, in addition to the adhesive properties of PVDF, the ionic conductivity of PVDF is also improved. The process involves the controlled addition of organically dissolved PVDF to an aqueous basic solution containing Li ions. Chemical evaluations are conducted using electron paramagnetic resonance (EPR), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) to confirm the cross-linkage of PVDF. The formation of a resilient structure of the crosslinked PVDF is ascertained by tensile measurement. Moreover, electrochemical measurements are carried out to study the ionic conductivity, charge-discharge process, and cycle performance of the cross-linked PVDF. The cathode with cross-linked PVDF binder at an areal sulfur loading of 4mg cm-2 remained stable for 200 cycles at 0.1 C-rate. Further post-cycling characterizations show improved structural uniformity of the electrodes using cross-linked PVDF. The obtained results suggest cross-linked PVDF as a promising binder for LSBs with high energy density and longevity.References(1) Kannan, S. K.; Joseph, J.; Joseph, M. G. Energy Fuels 2023, 37 (9), 6302–6322. https://doi.org/10.1021/acs.energyfuels.3c00155.(2) Zou, F.; Manthiram, A. Advanced Energy Materials 2020, 10 (45), 2002508. https://doi.org/10.1002/aenm.202002508.(3) Gao, Y.; Tan, Z.; Song, Z.; Qian, J.; Fu, C.; Nie, W.; Ran, X. Polymer Testing 2021, 99, 107202. https://doi.org/10.1016/j.polymertesting.2021.107202.(4) Fan, K.; Liu, C.; Zeng, H.; Li, J. H. High Energy Chem 2021, 55 (6), 436–441. https://doi.org/10.1134/S0018143921060059.

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

In-Situ Charging-Discharging SEM Observation and Analysis for Si Anode in a Solid-State Battery~ Cross-Section Preparation and in-Situ SEM Observation By Stack Pressure Holder ~

Next-generation solid-state batteries are expected to offer improved capacity and safety. The increase in capacity depends on the negative electrode material, and high-capacity materials such as Si, which can absorb large amounts of Li, are the subject of research. The amount of Li transferred can be measured electrically. However, it has not been possible to visualize where Li is distributed within the anode particles or to analyze the chemical state of the anode particles in real-time.In-situ observation and analysis of sample cross sections using a scanning electron microscope (SEM) are effective in analyzing the behavior and chemical state of Li introduced into the Si anode and the interface state between the solid electrolyte and the anode during charge-discharge. During charging and discharging, the Si anode undergoes a threefold or greater volume expansion and contraction due to Li absorption and desorption, cutting off the ionic conduction path, so it is necessary to apply a sample stacking pressure to suppress the volume expansion. A stack pressure holder is designed for operando experiments of solid-state batteries in an SEM. This holder enables smooth cross-sectioning using a broad Ar ion beam and in-situ SEM observation while applying uniform pressure which minimizes the resistance across interfacial boundaries. It also reduces the risk of specimen breakage because it fixes the sample throughout the entire air-isolated workflow, from cross-section preparation to real-time observation in the SEM.Si anode composites were made by mixing Si particles, argyrodite sulfide solid electrolyte (SSE), and acetylene black (AB). The cathode composite was made by mortar mixing the ternary oxide cathode material LiNi1/3Mn1/3Co1/3O2 (NMC), SSE, and AB. Each component was put into a pelletizer, stacked, and pressurized at about 500 MPa to produce a full cell pellet. The pellet was cut into 4.8 mm squares using a precision punching tool for highly brittle materials (NOGAMIGIKEN, NC-CE-SS) and placed on the stack pressure holder, where a pressure of 25 MPa was applied. The cross-sections were prepared with an Ar ion beam (acceleration voltage: 5 kV, cooling temperature: -120 °C, processing time: 5 hr) using a cross-section preparation system (JEOL, Cooling Cross Section PolisherTM, IB-19520CCP) while applying stack pressure. In order to minimize sample deterioration due to exposure to the atmosphere, glove boxes and transfer vessels that can be closed to the atmosphere were used for the entire process from pretreatment to processing to observation. Samples transported to the SEM in the stack pressure holder were charged and discharged at 0.2C (SOC vs. NMC reference) by a charge/discharge device (MEIDEN HOKUTO, Hz-Pro).The observation results of the charge-discharge process on a cross-sectional sample under stack pressure using this holder are shown in Fig. 1. (a) shows the backscattered electron (BSE) composition image near the interface between the Si anode and SSE and the interface and Si anode particles are clearly observed. (b) shows the charge-discharge curve in this experiment, and (c) shows the BSE composition image after 30 minutes of charging (SOC 10% vs. NMC reference), in which the composition contrast of the Si negative electrode particles gradually changes from the solid electrolyte side due to Li absorption during charging. In the experiment, the sample was maintained at a fixed holding pressure from the time of CP cross-section processing to the SEM observation without changing the holder, and it can be assumed that the observed behavior is similar to the actual behavior. Energy dispersive X-ray spectroscopy (EDS) and soft X-ray spectroscopy (SXES) can also be performed during in-situ charge-discharge observations to obtain elemental distribution and chemical state analysis of lithium and Si. The changes in microstructure of the battery cross-section can also be captured, and the chemical state analysis and the evaluation of the optimum stack pressure at the pressures up to 50 MPa can be expected.AcknowledgmentsWe would like to thank Professor Nobuya Machida of Konan University for cooperation in some of the battery sample preparation. Figure 1

(Battery Division Early Career Award Sponsored by Neware Technology Limited) Spin Probes and Materials Design for Next-Generation Batteries

While batteries have become ubiquitous in our daily lives, rapid growth in demand requires the development of higher energy density devices, and lower cost and more sustainable battery chemistries. When it comes to Li-ion batteries, despite significant research efforts over decades, we continue to rely on a limited subset of cathode materials that derive from LiCoO2 developed in 1980. The main bottleneck to advancing cathodes is the exceptional complexity of charge-discharge processes. This is compounded by the dearth of experimental techniques capable of bridging atomic-level phenomena and electrode-level performance. In the first part of this talk, I will present our work combining advanced ex situ and operando characterization and first principles calculations to better understand the working principles and sources of irreversibility in LiNiO2. [1, 2] The second part of this talk will focus on alternatives to the current Li-ion technology, including Na-based and solid-state batteries. In particular, solid electrolyte development has been hampered by the difficulty to identify materials that are chemically and electrochemically stable during normal battery operation, while also exhibiting a high ionic conductivity. I will present our recent work investigating chloride-based solid electrolytes for Li- and Na-based solid-state devices. [3-6] A common theme throughout is the combined use of solid-state NMR, magnetometry, X-ray diffraction, and first principles calculations to better understand the links between synthesis, composition/structure and electrochemical properties.[1] Nguyen, H., Kurzhals, P., Bianchini, M., Seidel, K., Clément, R., “New insights into aging in LiNiO2 cathodes from high resolution paramagnetic NMR spectroscopy”, ChemComm, 60(35), 4707-4710 (2024).[2] Nguyen, H., Silverstein, R., Zaveri, A., Cui, W., Kurzhals, P., Sicolo, S., Bianchini, M., Seidel, K., Clément, R., “Twin Boundaries Contribute to The First Cycle Irreversibility of LiNiO2”, Adv. Funct. Mater., 2306168 (2023).[3] Sebti, E., Evans, H., Chen, H., Richardson, P., White, K., Giovine, R., Koirala, K., Xu, Y., Gonzalez-Correa, E., Wang, C., Brown, C., Cheetham, A., Canepa, P., Clément, R., "Stacking Faults Assist Lithium-Ion Conduction in a Halide-Based Superionic Conductor", J. Am. Chem. Soc., 144, 5795 (2022).[4] Wu, E., Banerjee, S., Tang, H., Richardson, P., Doux, J.-M., Qi, J., Zhu, Z., Grenier, A., Li, Y., Zhao, E., Deysher, G., Sebti, E., Nguyen, H., Stephens, R., Verbist, G., Chapman, K., Clément, R., Banerjee, A., Meng, Y. S., Ong, S. P., "A Stable Cathode-Solid Electrolyte Composite for High-Voltage, Long-Cycle-Life Solid-State Sodium-Ion Batteries", Nat. Commun., 12(1), 1256 (2021).[5] Sebti, E., Qi, J., Richardson, P., Ridley, P., Wu, E., Banerjee, S., Giovine, R., Cronk, A., Ham, S.-Y., Meng, Y. S., Ong, S. P., Clément, R., “Synthetic control of structure and conduction properties in Na-Y-Zr-Cl solid electrolytes“, J. Mater. Chem. A, 10 (40), 21565-21578 (2022).[6] Ridley, P., Nguyen, L. H. B., Sebti, E., Duong, G., Chen, Y.-T., Sayahpour, B., Cronk, A., Deysher, G., Ham, S.-Y., Oh, J. A. S., Wu, E., Tan, D., Doux, J.-M., Clément, R., Jang, J., Meng, Y. S., “Amorphous and Nanocrystalline Halide Solid Electrolytes with Enhanced Sodium-ion Conductivity”, Matter, 7(2), 485-499 (2024).

(Invited) Controlled Large-Area Lithium Deposition to Reduce Swelling of High-Energy Lithium Metal Pouch Cells in Liquid Electrolytes

Lithium (Li) metal battery technology, renowned for its high energy density, faces practical challenges, particularly concerning large volume change and cell swelling. Despite the profound impact of external pressure on cell performance, there is a notable gap in research regarding the interplay between external pressure and electroplating behaviors of Li+ in large-format pouch cells. Here we delve into the impact of externally applied pressure on electroplating and stripping of Li in 350 Wh/kg pouch cells. Employing a hybrid design, we monitor and quantify self-generated pressures, correlating them with observed charge-discharge processes. A two-stage cycling process is proposed, revealing controlled pouch cell swelling of less than 10%, comparable to state-of-the-art Li-ion batteries. The pressure distribution across the cell surface unveils a complex Li+ detour behavior during electroplating, highlighting the need for innovative strategies to address uneven Li plating and enhance Li metal battery technology.

A Spherical LiFePO4/Carbon Nanotubes/Binder Composite as a Cathode Material for High Performance of Lithium-Ion Batteries

As the global demand for electric vehicles continues to rise, the safety of electric vehicles, particularly concerning the risk of fires induced by battery degradation, is increasingly recognized as a critical issue. Current production batteries utilize cathode materials with high nickel content (>80%) in order to develop electrodes with high-energy-density. However, these NCM cathode materials, due to their structural instability, can undergo changes during the charge-discharge processes of the battery, making them susceptible to degradation in high-temperature environments or during charging-discharging, thereby posing a fire risk. Therefore, many battery companies are currently focusing on advancing research into utilizing LiFePO4 (LFP) cathode materials. LFP possesses a stable olivine structure, resulting in fewer structural changes during charge and discharge compared to NCM cathode materials. Consequently, LFP batteries offer high durability and a lower risk of fires, enhancing the safety of electric vehicle batteries. Additionally, the raw materials used in LFP production are relatively cost-effective, contributing to lower battery manufacturing costs.However, LFP has relatively lower energy density and smaller particle sizes than NCM, limiting its ability to increase battery capacity. It also exhibits lower electrical conductivity, which can have disadvantages in terms of electrochemical properties including battery resistance and rate capability. To overcome these limitations, various research studies have been conducted, such as controlling particle size and applying surface coatings to the active material.In this study, spherical LFP/carbon nanotubes (CNTs)/binder composites were developed to improve cell performance. We synthesized LFP/CNTs/binder composites through the spray-drying method and studied the morphologies of granules according to spray drying conditions. We particularly focused on achieving a well-distributed spherical microstructure to improve the electrode modulus, including electrode density and tortuosity. LFP with well-embedded CNTs and binder exhibited excellent cell lifespan characteristics even at high energy density and showed good performance at high C-rates.

A Sandwich-structured EVA/Cu2O/Cu Composite Current Collector to Suppress the Lithium Dendrite Growth.

The proliferation of lithium dendrites has long posed a formidable hurdle in the widespread adoption of lithium metal batteries, thereby necessitating the urgent resolution of how to effectively mitigate their growth as the paramount challenge in the realm of energy storage. Herein, we have crafted a novel sandwich-structured current collector comprising an ethylene-vinyl acetate polymer (EVA)/Cu2O/Cu configuration, where the EVA thin film acts as a protective barrier, passivating the lithium metal anode, while the Cu2O layer fosters lithiophilic sites conducive to uniform lithium nucleation. Our experiments reveal that the EVA thin film adeptly prevents direct contact and subsequent reactions between the lithium metal and the electrolyte, enhancing the ion mobility of Li+ ions, ultimately leading to a even distribution of lithium deposition. In a Li-Cu half-cell, the incorporation of the EVA film increases the nucleation potentials but dramatically reduces polarization potentials after 50 cycles of charge-discharge processes. Remarkably, the Li-Cu half-cells equipped with EVA-coated current collectors exhibit lower electrochemical resistances, translating into significantly extended cycle lives. This work indicates the sandwich architecture (thin film/lithium metal/lithiophilic compounds) is a promising contender for achieving long-lasting, stable lithium anodes.

Zn-Doped Hollow Cubic MnO2 as a High-Performance Cathode Material for Zn Ion Batteries.

Manganese-based compounds have the characteristics of high theoretical capacity, low cost and stable performance, thus become a research hotspot for cathode materials of zinc-ion batteries (ZIBs). However, in the process of charging and discharging, it is accompanied by problems such as structural collapse and low conductivity, which resulted in severe capacity degration during cycles. In this paper, a kind of Zn2+ doped MnO2 hollow cube cathode material (Zn-MnO2) was prepared by self-sacrificing template method. The Zn2+ doped in MnO2 crystals can induce oxygen vacancies in the structure, thereby improving the structural stability ion diffusion coefficient and electrical conductivity of the material. After 100 cycles at 0.3 A g-1, the high specific capacity of 281.2 mA h g-1 is still maintained. Through ex-situ XPS and ex-situ XRD tests, the mechanism of charge-discharge process was discussed. The results show that the storage mechanism of Zn-MnO2 is H+ and Zn2+ insertion/removal and Mn3+/Mn2+ two-electron reaction pathway. The total state density (TDOS) and partial state density (PDOS) of Zn-MnO2 and MnO2 further demonstrated that the doping of Zn2+ enhanced the electron conductivity and is beneficial to the electron transfer during the electrochemical reaction.

Ultrafast Tailoring Amorphous Zn0.25V2O5 with Precision‐Engineered Artificial Atomic‐Layer 1T′‐MoS2 Cathode Electrolyte Interphase for Advanced Aqueous Zinc‐Ion Batteries

AbstractVanadium (V)‐based oxides as cathode materials for aqueous zinc‐ion batteries (AZIBs) still encounter challenges such as sluggish Zn2+ diffusion kinetics and V‐dissolution, thus leading to severe capacity fading and limited life span. Here, we designed an ultrafast and facile colloidal chemical synthesis strategy based on crystalline Zn0.25V2O5 (c‐ZVO) to successfully prepare a‐ZVO@MoS2 core@shell heterostructures, where atomic‐layer MoS2 uniformly coats on the surface of amorphous a‐ZVO. The tailored amorphous structure of a‐ZVO provides more isotropic pathways and active sites for Zn2+, thus significantly enhancing the Zn2+ diffusion kinetics during charge–discharge processes. Meanwhile, as an efficient artificial cathode electrolyte interphase, the precision‐engineered atomic‐layer MoS2 with semi‐metallic 1T′ phase not only contributes to improved electron transport but also effectively inhibits the V‐dissolution of a‐ZVO. Therefore, the prepared a‐ZVO@MoS2 and conceptually validated a‐V2O5@MoS2 derived from commercial c‐V2O5 exhibit excellent cycling stability at an ultralow current density (0.05 A g−1) while maintaining good rate capability and capacity retention. This research achievement provides a new effective strategy for various amorphous cathode designs for AZIBs with superior performance.

Ultrafast Tailoring Amorphous Zn0.25V2O5 with Precision-Engineered Artificial Atomic-Layer 1T'-MoS2 Cathode Electrolyte Interphase for Advanced Aqueous Zinc-Ion Batteries.

Vanadium (V)-based oxides as cathode materials for aqueous zinc-ion batteries (AZIBs) still encounter challenges such as sluggish Zn2+ diffusion kinetics and V-dissolution, thus leading to severe capacity fading and limited life span. Here, we designed an ultrafast and facile colloidal chemical synthesis strategy based on crystalline Zn0.25V2O5 (c-ZVO) to successfully prepare a-ZVO@MoS2 core@shell heterostructures, where atomic-layer MoS2 uniformly coats on the surface of amorphous a-ZVO. The tailored amorphous structure of a-ZVO provides more isotropic pathways and active sites for Zn2+, thus significantly enhancing the Zn2+ diffusion kinetics during charge-discharge processes. Meanwhile, as an efficient artificial cathode electrolyte interphase, the precision-engineered atomic-layer MoS2 with semi-metallic 1T' phase not only contributes to improved electron transport but also effectively inhibits the V-dissolution of a-ZVO. Therefore, the prepared a-ZVO@MoS2 and conceptually validated a-V2O5@MoS2 derived from commercial c-V2O5 exhibit excellent cycling stability at an ultralow current density (0.05 A g-1) while maintaining good rate capability and capacity retention. This research achievement provides a new effective strategy for various amorphous cathode designs for AZIBs with superior performance.

Origin of the High Catalytic Activity of MoS2 in Na-S Batteries: Electrochemically Reconstructed Mo Single Atoms.

Room-temperature sodium-sulfur (RT Na-S) batteries with high energy density and low cost are considered promising next-generation electrochemical energy storage systems. However, their practical feasibility is seriously impeded by the shuttle effect of sodium polysulfide (NaPSs) resulting from the sluggish reaction kinetics. Introducing a suitable catalyst to accelerate conversion of NaPSs is the most used strategy to inhibit the shuttle effect. Traditional catalytic approaches often want to avoid the irreversible phase transition of the catalyst at a deep discharge. On the contrary, here, we leverage the intrinsic structural tunability of the MoS2 catalyst in the opposite direction and innovatively propose a voltage modulation strategy for in situ generation of trace Mo single atoms (MoSAC) during the first charge-discharge process, leading to the formation of highly active catalytic phases (MoS2/MoSAC) through the self-reconstruction. Theoretical calculations reveal that the incorporation of MoSAC modulates the electronic structure of the Mo d-band center, which not only effectively promotes the d-p orbital hybridization but also accelerates the catalytic intermediate desorption by the bonding transition, the dynamic single-atom synergistic catalytic mechanism enhances the adsorption response between the metal active site and NaPSs, which significantly improves the sulfur redox reaction (SRR), and the initial capacity of the MoS2/MoSAC/CF@S cell at 0.2 A g-1 is increased by 46.58% compared to that of the MoS2/CF@S cell. The discovery of the MoS2/MoSAC/CF catalyst provides new insights into adjusting the structure and function of transition metal disulfide catalysts at the atomic scale, offering hope for the development of high-specific-energy RT Na-S batteries.