Li metal is highly sought after as a negative electrode material due to its high specific capacity and low electrode potential. However, the brittle solid electrolyte interphase and undesirable coulombic efficiency have severely hindered its commercial application. Here we propose a formation mechanism of stable solid electrolyte interphase based on the de-solvation of heteroalkali cations rather than the simple electrostatic shielding effect. Cesium trifluoroacetate (CsTFA), characterized by high electron-donor anion and weak solvent-binding heteroalkali cation, was incorporated into commercial electrolytes to foster an inorganic-rich solid electrolyte interphase. The de-solvation of absorbed Cs+ dominates the initial solid electrolyte interphase formation on the Li surface. Simultaneously, the preferential reduction of TFA- promotes the enrichment of LiF within the solid electrolyte interphase. Owing to the synergistic effect of CsTFA, Li | |Cu half cells deliver a high CE of 99.77%, and Li | |LFP full cells exhibit satisfactory stability over 300 cycles with a 94.3% capacity retention at a negative/positive electrode capacity ratio of 1.36. Moreover, the added CsTFA in conventional ester electrolyte demonstrates improved stability of Li | |NCM811 full cells with an 80% capacity retention over 222 cycles at a negative/positive electrode capacity ratio of 1.

In the Bianchini group at the Bavarian Center for Battery Technology materials for Na-ion batteries are being investigated both in the context of the ERC project 4SBATT (Sustainable Solid State Sodium Batteries) as well as in the recent SIB:DE consortium, funded by the BMBF and aimed at developing sodium-ion batteries made in Germany.In this presentation, I will give an overview of our recent findings in the field of both positive and negative electrode materials. Concerning cathodes our recent attention has been on layered oxides (NaxTMO2, TM = transition metal). P2 and O3 are two of the most studied structures in the NaxTMO2 system. Regarding Na+ conductivity, P2 is believed to be preferable over O3 as it provides open prismatic pathways with a lower energy barrier for Na diffusion.[1] However, a drawback for P2 materials is that they are typically synthesized with low Na content, usually not beyond x = 3/4, which is not ideal when building full cells.[2] The other major issue of P2 is the P2–O2 phase transition taking place at high voltage during electrochemical cycling, which is irreversible and limits cycling stability and capacity retention.[3] We tackle both issues by doping inactive elements in the pristine materials without excessively compromising specific discharge capacity. We focused on a family of Li-doped P2 materials with nominal compositions of Na5/6LiyNi5/12-3y/2Mn7/12+y/2O2 (y = 2/18, 3/18, 4/18, 5/18). We reported on the characterizationsof the crystal structures of these materials, as well as the temperature-resolved in situ XRD during their solid-state synthesis[4]. Structurally, honeycomb ordering is observed in all samples, while Li induces the loss of Na+/vacancy ordering. Electrochemically, the materials exhibit an increasing trend of polarized hysteresis in the 1st cycle. Semi-simultaneous operando x-ray absorption and diffraction are coupled to appreciate the structural evolution and redox behavior during this process. Li in the transition metal site eliminates phase transitions at high voltage and modifies the activation of O-redox. All samples show anionic redox: as confirmed computationally, in the Li-free sample this is rooted in Ni─O hybridized states, while in the Li-containing samples in O non-bonding states. Composition Na0.745(6)Li0.164(4)Ni0.238(1)Mn0.599(3)O2 proves to have the least O-redox among all, coupled with reduced phase transitions, disordered occupancy of Na sites, and small volume change during cycling, leading to the best balance of cycling stability, capacity and rate capability.Concerning our work on negative electrode materials, we aim to address the low volumetric capacity of hard carbons compared to graphite. Our strategy to overcome these issues is mixing HC with a denser element, that has an active role in sodium storage. For our composites we employ tin, that has a high theoretical gravimetric capacity (847 mAh/g) [5]. The main issue linked to alloying materials is the high-volume expansion after discharge (420 % for tin), leading to fast capacity fade because of the solid electrolyte interphase (SEI) continuous destruction in carbonated electrolytes. For this reason, we prepared HC/Sn composites able to mitigate the expansion and avoid tin aggregation. In our work HC/Sn composites are prepared by spray drying synthesis and analyzed through spectroscopic, scattering, and electrochemical techniques. We investigated the evolution of the system by operando XRD carried out at low current rate (coulometric titration), to confirm the expected phases based on the phase diagram are indeed observed. Experimental data and theoretical information from literature are used to identify crystalline and amorphous phases[6]. The morphology of all the materials is investigated by SAXS, so the nature of the meso and micro structure is elucidated. The results are corroborated by the electrochemical tests. Our materials show better gravimetric and volumetric performances than HC (closer to graphite in LIBs) and therefore they are a valid alternative for next generation Na-based batteries[7].

The lifespan of a battery in a battery electric vehicle (BEV) is affected by various user-related and environmental factors. Real-world driving experiences differ from driver to driver, with conditions that can vary significantly1,2. This study investigates the combined impact of the various state-of-charge (SoC) cycling windows and real-world fast charging on battery performance and aging. Departing from the conventional constant-current constant-voltage (CC-CV) fast charging protocol, a scaled-down equivalent of a 150kW real-world BEV fast charging profile for an NCA/graphite lithium-ion 18650 cylindrical cell was adopted for this study. Unlike the broader SoC range (0 to 100%) of high current charging typical in CC-CV protocol, the real-world BEV protocol employs peak power or peak current only in a narrow ΔSoC (10%-40%) and then tapers down. Cycling tests were conducted for three sets of ΔSoC: partial-cycle aging (0%-50% and 0%-80%) and full-cycle aging (0%-100%). In addition to the above tests, a full-cycle aging test with a standard CC-CV charging protocol was also conducted. The capacity fade trends reveal a clear correlation between partial-cycle aging and better cycle life. Notably, despite different charging protocols, full-cycle aging exhibited similar capacity fade trends. The degradation pathway of these cells was monitored by non-destructive electrochemical methods, including differential voltage and incremental capacity analysis (DVA-ICA) and electrochemical impedance spectroscopy (EIS). Cell impedance increased for all the cycling conditions, with full-cycle aging tests showing a higher impedance increase than partial-cycle aging tests. Loss of lithium inventory (LLI) combined with the loss of active positive (LAMPE) and negative electrode material (LAMNE) were found to be the prominent degradation modes. The full-cycle aging cells experienced a more significant loss of activated electrode material, with LAMPE being the more substantial contributor towards battery degradation than LAMNE.The results of this study provide insights into the distinct, cycling window-dependent degradation patterns observed in the cells, forming a foundation for understanding the implications of user behavior on battery degradation. It highlights the importance of optimized battery usage to extend lifespan and improve economics, thereby contributing to the growth of the sustainable BEV market.

Silicon (Si) has attracted much attention as an emerging negative electrode material for all-solid-state lithium-ion batteries (ASSLIBs) because of the considerably high theoretical energy-density. However, its notorious volume changes during charge/discharge cycles often cause the rapid capacity fading. Thus, investigations into physicochemical and mechanical phenomena in Si electrodes during electrochemical lithiation/delithiation under ASSLIB configurations are of great importance. Single-crystal Si (sc-Si) is an excellent subject of research to understand the anisotropic lithiation/delithiation characteristics by using different face orientations. Nevertheless, the available studies to date are mainly focused on the conventional-type LIB systems, which employ liquid organic-compounds as the main electrolyte components 1,2.We have previously revealed the nanomechanical phenomena in a thin-film amorphous Si (a-Si) electrode assembled in an ASSLIB configuration during the first electrochemical lithiation/delithiation using our newly constructed operando bimodal atomic force microscopy (AFM) system for solid-state batteries 3. A steep elastic modulus decrease was observed at the initial stage of the lithiation, due to the formation of lithium silicide (Li x Si), followed by a gradual modulus reduction up to the completion of the first lithiation 3. Likewise, operando X-ray photoelectron spectroscopy (XPS) analysis of the a-Si electrode indicated a steep binding energy shift of the bulk Si0 peak to form Li x Si in the initial stage of lithiation, followed by the monotonic shift in response to the increase of Li content x in Li x Si 4-6. Interestingly, a drastic peak shift associated with the phase transformation from crystalline Li15Si4 (c-Li15Si4) into a-Li x Si was detected at Li content x = 1.6 – 2.0 in Li x Si during the subsequent delithiation, which caused the significant capacity loss probably due to the mechanical phenomena 4-6.Electrochemical lithiation of sc-Si electrodes is known to be anisotropic 1,2, and thus, a guideline to mitigate the rapid capacity fading due to the mechanical phenomena can be obtained by understanding the lithiation/delithiation mechanism of sc-Si electrodes, leading to the development of the long-lived Si-based negative electrode materials. In this study, we investigate the anisotropic electrochemical lithiation behaviors in sc-Si electrodes with different surfaces of (110), (100), and (111), evaluated using a variety of techniques including transmission electron microscopy (TEM), scanning electron microscopy (SEM), and XPS.ASSLIB half-cells with a configuration of sc-Si working electrode/lithium phosphorous oxynitride (LiPON) solid-electrolyte/Li metal counter electrode (sc-Si/LiPON/Li) were fabricated from commercially available sc-Si wafers by sputter-deposition of a LiPON layer, followed by incorporation of a piece of Li metal foil. After the electrochemical lithiation, the sc-Si/LiPON/Li cells were cleaved to expose their cross-sections in an inert Ar-filled glove box, transported via a sealed transfer vessel, and analyzed by the above-mentioned techniques.At all the surface orientations (110), (100) and (111), the formation of a-Li x Si layer was clearly observed between the LiPON layer and sc-Si electrode. However, the Li content x in a-Li x Si layer was significantly different depending on the surface orientations, confirming the anisotropic lithiation reaction and Li-ion diffusion. The details including chemical species and nanomechanical properties will be discussed at the meeting as well as the anisotropic reaction mechanism. References (1) Aoki, N.; Omachi, A.; Uosaki, K.; Kondo, T., ChemElectroChem 2016, 3 (6), 959.(2) Omachi, A.; Aoki, N.; Uosaki, K.; Kondo, T., ECS Trans. 2017, 75 (52), 67.(3) Putra, R. P.; Matsushita, K.; Ohnishi, T.; Masuda, T., J. Phys. Chem. Lett. 2024, 15 (2), 490.(4) Endo, R.; Ohnishi, T.; Takada, K.; Masuda, T., J. Phys. Chem. Lett. 2020, 11 (16), 6649.(5) Endo, R.; Ohnishi, T.; Takada, K.; Masuda, T., J. Phys. Commun. 2021, 5 (1), 015001.(6) Endo, R.; Ohnishi, T.; Takada, K.; Masuda, T., J. Phys. Chem. Lett. 2022, 13 (31), 7363.

Deep eutectic electrolytes (DEEs) are a combination of two or more components, usually solid powders, that when mixed exhibit significantly lower melting points than the pure materials due to hydrogen bonding, Lewis acid-base, and other intermolecular interactions. Since DEEs have unique properties and can be prepared using low-cost materials, they have attracted attention as new electrolytes for Li-ion batteries (LIBs) .1, 2 Earlier this year, we reported the preparation of DEEs containing lithium bis(fluorosulfonyl)amide (LiFSA) and urea-derivatives, and tested them with positive and negative electodes.3 However, we found the range of concentrations that form liquid phase DEEs with urea was quite limited. In this study, we explored the usage of urea with an alternative electrolyte salt, lithium (fluorosulfonyl)(trifluoromethanesulfonyl)amide (LiFTFSA), and a binary salt of LiFSA and lithium bis(trifluoromethanesulfonyl)amide (LiTFSA), which show lower melting points than LiFSA. The physicochemical and electrochemical properties of these electrolytes were thoroughly investigated for application in lithium-ion batteries.To prepare the DEEs, a 6:4 (mol/mol) mixture of LiFSA and LiTFSA (LiFSA0.6TFSA0.4) or LiFTFSA was mixed with urea at room temperature. Compared to the previously reported LiFSA:urea (1:3.8) – (1:4.2),3 the composition range for forming room temperature liquids was extended to LiFSA0.6TFSA0.4:urea (1:2.5) – (1:4) and LiFTFSA:urea (1:1.5) – (1:4). The oxidation and reduction stability was evaluated by voltammetry (LSV or CV) using Pt foil or Al foil as the working electrode, respectively. All electrolytes showed good reduction stability and reversible Li-Al alloying or Li plating reactions (Fig. 1). Furthermore, DEEs prepared with higher Li salt concentrations exhibited higher oxidation stability.Galvanostatic charge-discharge tests were performed in three-electrode cells with LiTi4O5 (LTO) or LiFePO4 (LFP) working electrodes. For LTO negative electrodes (Fig. 2), capacity fading and low average Coulombic efficiencies below 80% were observed after 50 cycles in the LiFSA0.6TFSA0.4:urea (1:2.5) and LiFTFSA:urea (1:4) electrolytes. The cell containing LiFSA0.6TFSA0.4:urea (1:4) achieved the highest capacity retention of ~90% and average Coulombic efficiency of 85% after 50 cycles. In contrast to LTO, LFP positive electrodes exhibited stable charge/discharge behavior and achieved nearly 100% capacity retention in early cycles using LiFSA0.6TFSA0.4:urea (1:2.5) and (1:4) electrolytes (Fig. 3). These results indicate some of the DEEs are compatible for both practical positive and negative electrode materials and could be candidates for new electrolytes for LIBs. The impact of these new electrolyte salts on LIB performance, as well as the thermal stability and solution structure of DEEs will be discussed.

Proton batteries are attracting increasing attention as an innovative and sustainable alternative in the energy sector. These batteries are recognized as one of the promising solutions for next-generation energy storage technologies. For instance, Nickel-Metal Hydride (Ni-MH) batteries are well-known for their excellent recyclability, competitive energy density, minimal memory effect, wide operating temperature range, affordability, and environmental sustainability [1]. However, their practical application is limited by their low specific energy density, high self-discharge rate, and electrode aging [2,3].Our investigation is focused on the negative electrode of the Ni-MH battery and its interaction with the electrolyte. Our objective is to enhance the performance of the negative electrode of Ni-MH batteries by substituting the conventional water-based 8.7 M KOH electrolyte with a Protic Ionic Liquid (PIL) in order to overcome the aforementioned drawbacks [4]. PILs have the capacity to exchange a labile proton, thereby supporting the main redox reaction, hydrogenation, at the negative electrode of Ni-MH batteries. The proton exchange between the PIL and the electrode material is considered a key step that must be thoroughly understood to optimize battery performance. Several mechanisms may govern this exchange process. Among them, a desired multi-step mechanism leads to the formation of a metal hydride, which is essential for efficient energy storage. However, side reactions may also occur, similar to those observed in aqueous media, such as hydrogen gas evolution. These parasitic processes likely follow classical pathways such as Volmer-Tafel or Volmer-Heyrovsky mechanisms.In order to understand how protons are exchanged between the PIL electrolyte and the negative electrode materials, electrochemical impedance spectroscopy (EIS) measurements were performed. The experimental results were modeled using a model inspired by a single particle approached proposed by Meyers et al. [5]. Our model enables the consideration of a porous electrode structure, with a kinetic description of the electrochemical reactions occurring at the solid–electrolyte interface, thereby providing a more realistic interpretation of the impedance spectra as previously reported for Li-batteries [6]. We successfully fitted the experimental results for both KOH and PIL at various states of charge.The authors gratefully acknowledge financial support from the ANR through the H-BAT project (ANR-21-CE50-0030). This work was also supported by the Doctoral School of Physical and Analytical Chemistry of Paris Centre (ED388).[1] M.A. Hannan, M.M. Hoque, A. Mohamed, and A. Ayob, Renew. Sustain. Energy Rev. 69 (2017) 771–789.[2] B. Puga et al., ChemElectroChem, 2 (2015) 1321–1330.[3] J. Matsuda, Y. Nakamura, E. Akiba, J Alloys Compd, 509 (2011) 7498–7503.[4] N. Chaabene, et al., J. Power Sources 574 (2023) 233176.[5] J.P. Meyers, M. Doyle, R.M. Darling, J. Newman, J. Electrochem. Soc., 147 (2000) 2930-2940.[6] D. Gruet et al., Electrochim. Acta, 295 (2019) 787-800.

Silicon (Si) is a promising negative electrode material for high-energy automotive batteries, but its significant volume changes during cycling cause rapid degradation, limiting its loading to just 10 wt.% in commercial graphite/Si composite negative electrodes as a compromise between energy density and cycle life. Overcoming this threshold requires evidence-based design of advanced electrodes. Here we combine operando optical microscopy, synchrotron X-ray CT 4D imaging, digital image/volume correlation and machine learning-assisted image processing techniques, to elucidate the multiscale electro-chemo-mechanical processes in graphite/µ-Si composite negative electrode. Presented with multimodal high-resolution videos, here we show the expansion of porous µ-Si particles strongly depend on the morphology of the intra-particle porosity. One dimensional tubular porosity is conducive to suppressed volume expansion and cracking compared to planar porosity, which incurs highly anisotropic particle strain and crack. Moreover, the encapsulation and loss of active Si particles result in excessive charging current being directed to the graphite particles, thereby increasing the risk of premature lithium plating—an overlooked safety concern. Surprisingly, the electrode expansion is not necessarily governed by Si; rather, its influence only becomes pronounced at high SOCs during the first lithiation cycle but is dominated by graphite in the subsequent cycles. Severe thickness expansion (20%) and reduction in nano-pores (from 43% to 21%) are observed in the CBD, undermining accessible capacity and fast charging capability. Finally, in response to the five identified major challenges in graphite/µ-Si composite electrodes, we develop a double-layered graphite/µ-Si composite negative electrode, which demonstrates significantly lower polarization and mitigated capacity decay compared to its homogeneous counterparts. Overall, this study provides a comprehensive framework for advancing Si-based negative electrodes through hierarchical engineering, from particle level to the 3D architecture of the electrode. Figure 1

Introduction It is essential that captured CO2 will be utilized as high-value products to achieve the carbon neutral by 2050. Electrochemical reduction of CO2 using molten salt is drawing attention as a part of carbon capture and utilization (CCU) technology because CO2 can be completely reduced to carbon allotropes [1]. In particular, demand for graphite, which is used for negative electrode material of lithium-ion batteries (LIB), is expected to increase in the future.Furthermore, molten salt electrolysis can be utilized as in-situ resource utilization (ISRU) on the Mars since this method is able to generate O2 and carbon material from CO2.In this study, the effects of electrolysis conditions on carbon electrodeposition have been investigated by varying the electrolysis potential and temperatures in molten NaCl–KCl–BaCl2–BaCO3. Selection of molten salt To obtain graphite, it is necessary to choose the suitable salt that is possible to use for carbon deposition at higher temperature since it is advantageous to form graphite [2]. Fig.1 shows theoretical decomposition voltages of Li2CO3, CaCO3, and BaCO3 into carbon or carbon monoxide (CO) that is calculated by HSC Chemistry [3]. This graph elucidates that decomposition into carbon is preferred for Li2CO3 and BaCO3 even at 1173 K. On the other hand, CaCO3 is decomposed to CO over 1073 K. In addition, Li2CO3 begins to thermally decompose gradually above its melting point of 996 K.Therefore, BaCl2 is selected as the main constituent salt, and BaCO3 is selected as the source of CO3 2 － in this work. Moreover, NaCl and KCl were added to BaCl2 system to decrease melting point. Herein, it is presumed that there is no harmful effect on carbon electrodeposition since the calculated theoretical decomposition voltages of Na2CO3 and K2CO3 into carbon are larger than that of BaCO3. Experimental Carbon electrodeposition was carried out in eutectic NaCl–KCl–BaCl2 (35.0:37.2:27.8 mol%) molten salt with 2.0 mol% BaCO3 added under an Ar atmosphere. A Ni plate and a graphite rod were used as the working and counter electrodes, respectively. As the reference electrode, an Ag+/Ag electrode was used, and the potential was calibrated by Na metal deposition potential. Potentiostatic electrolysis was conducted for 30 min at various potentials of 0.4, 0.6, 0.8 V (vs. Na+/Na) and temperatures of 873, 973, 1073 K. The obtained samples were washed thoroughly with distilled water and 1 M HCl aqueous solution, and subsequently dried them. Raman spectroscopy and XRD analysis were conducted on the samples on the Ni electrode. Results and Discussion Fig.2 shows the optical images of the sample obtained at 0.4 V and 873 K before and after washing. The black deposits were obtained, and a part of the deposits was removed from the Ni electrode during washing. The same situation was observed in the other samples.Fig.3 shows Raman spectra for deposits on the Ni electrodes electrodeposited at 0.4 V at temperatures of 873 K, 973 K, and 1073 K. In the 873 K and 973 K samples, spectra characteristic of amorphous carbon was observed, while in the 1073 K sample, the G band (around 1580 cm−1) and 2D band (around 2700 cm−1) characteristic of graphite were observed. The results above show that higher temperatures contribute to the electrodeposition of graphite. In the presentation, further detailed and other experimental results will be presented. Acknowledgment A part of this study was conducted in collaboration with Cosmo Oil Co., Ltd.

The simultaneous achievement of fast-charging and high specific capacity remains a critical challenge for lithium-ion battery negative electrodes. Here we report a layered manganese-based Prussian blue analogue, synthesized through vacancy control and subsequent thermal transformation. As a conversion-type negative electrode, this material exhibits high-rate performance, delivering a specific capacity of 510 mAh g−1 at a specific current of 8 A g−1, and operates at a moderate average voltage of approximately 1.2 V vs. Li/Li+, which mitigates lithium plating risks. This high-rate capability stems from the analogue’s specific linkage configurations, which facilitate a high content of active transition metal and strong Li+ adsorption at nitrogen sites. The high transition metal content enables a high reversible capacity, while strong Li+ adsorption promotes an efficient initial crystalline-to-amorphous transformation. This process induces dynamically reversible component migration during subsequent cycling, thereby enhancing conversion reaction kinetics. Our findings provide insights into the application of Prussian blue analogues as fast-charging negative electrode materials.

Natural gas, a versatile fossil fuel composed primarily of methane, is sourced from conventional reservoirs and unconventional deposits such as shale, coal beds, and marine sediments. Despite its abundance and cleaner combustion profile, methane's utility as a chemical feedstock is constrained by its exceptional chemical stability—a consequence of its symmetrical tetrahedral structure, strong C–H bonds, and low polarizability. Conventional conversion methods like steam methane reforming face challenges due to high energy demands and CO2 emissions. In contrast, methane pyrolysis offers a promising alternative by producing hydrogen and carbon materials without direct greenhouse gas emissions. However, commercialization has been hampered by catalyst degradation and extreme operating conditions.In this presentation, I introduce an innovative approach leveraging molten halide salt electrolysis to decompose methane efficiently under moderate temperatures (400–660 °C).[1] This hybrid electrochemical-thermochemical process builds on established metallurgical molten salt electrolysis technology. Within the molten salt electrolyte, chloride ions (Cl⁻) oxidize at the anode to form chlorine gas (Cl2), while sodium ions (Na⁺) reduce to metallic sodium (Na) at the cathode. A fraction of the sodium dissolves into the molten salt, generating highly reactive solvated electrons. When methane is introduced, it reacts with chlorine at the anode to produce chlorinated hydrocarbons (e.g., CH3Cl) and hydrogen chloride (HCl). As these intermediates migrate toward the cathode, they interact with solvated electrons or metallic sodium, yielding hydrogen (H2), ethylene (C2H4), and solid carbon. The majority of the chloride ions are regenerated and recycled within the electrolyte, creating a closed-loop system.Laboratory-scale trials using a LiCl-NaCl-KCl ternary molten salt system demonstrated a methane conversion of 30% at 550 °C, with 70% hydrogen selectivity and 5.3% ethylene selectivity. Increasing the temperature within the range of 400–550°C enhances the selectivity of hydrogen and ethylene, while increasing the current boosts the rate of NaCl electrolysis, producing more sodium and chlorine gas and thus improving methane conversion and hydrogen selectivity. Alkali metal bromides and alkaline earth metal chlorides can also be used as molten electrolytes for methane decomposition.Compared to traditional pyrolysis, this method operates at lower temperatures with enhanced stability. The solid carbon byproduct, which achieves ~99.66% purity after simple water washing and drying, shows promise as a battery negative electrode material. By leveraging the formation and reduction of halogenated intermediates, this strategy not only enables efficient methane conversion but also extends to other hydrocarbons, offering a versatile platform for sustainable chemical synthesis. This approach combines environmental benefits—avoiding CO₂ emissions—with economic advantages through high-value outputs, positioning it as a promising scalable pathway for decarbonizing hydrocarbon utilization.

Lithium-ion batteries (LIBs) are widely used due to their high energy density and versatile applicability. However, a growing demand for LIBs raises concerns for the sustainable supply chains of Li resources. As a complementary energy storage technology to LIBs, proton batteries, which utilize protons as charge carriers, have gained significant attention. Protons are promising charge carries owing to their widespread availability and high ionic mobility, enabling cost-effective and high-power battery systems. Nickel-metal hydride (Ni-MH) batteries are typical examples of proton batteries, but they depend on the use of electrode materials containing nickel and rare earth metals. Furthermore, the relatively low operating voltage limits energy density. To address these challenges, titanium-based layered oxides are examined as negative electrode materials for aqueous proton batteries. In this study, H2Ti3O7 was synthesized via hydrothermal treatment of rutile-type TiO2 in a 10 M NaOH aqueous solution at 170 oC for 20 hours, followed by thorough rinsing with deionized water.1 The electrochemical properties of the synthesized H2Ti3O7 were evaluated in various buffered/unbuffered aqueous electrolytes. H2Ti3O7 exhibits reversible redox reactions with buffered solutions. Furthermore, the combination of H2Ti3O7 and Ni(OH)2 achieves a higher operating voltage compared to conventional Ni-MH batteries. To further improve the battery performance, optimal buffer solutions with higher ionic conductivity and superior interfacial functionalities are explored. These findings contribute to the development of next-generation aqueous proton batteries with high energy density and superior sustainability.

All-solid-state batteries (ASSBs) face critical mechanical challenges, particularly when employing Li-metal, Si-based, or initially anode-free configurations, due to significant negative electrode volume changes within rigid cell architectures during cycling. Such fluctuations generate considerable mechanical stress, which can lead to both bulk and interfacial degradation, posing serious risks to long-term stability. This problem is further amplified in stacked cell configurations, where mechanical integrity is critical.Metal-organic frameworks (MOFs), present a potential solution to these challenges. MOFs, a class of hybrid materials composed of metal ions and organic ligands, have been extensively explored for energy storage applications owing to their mechanical stability, adjustable pore structure, and high specific capacity. Their high degree of customizability allows precise tailoring of pore size, shape, and chemical composition by altering the metal ions and organic ligands used in their synthesis. These features make MOF materials an ideal choice for low-strain negative electrodes tailored for various applications. For instance, in a study by Chen et al., a ZIF-8 MOF-derived carbon matrix was utilized as a 3D host for Si nanoparticles (SiNPs). This significantly reduced strain compared to conventional SiNP-based electrodes, effectively mitigating the volume changes during cycling in LIBs. Similarly, Zhang et al. demonstrated that Sn-MOF-derived Sn3(PO4)2 nanocrystal confined in an interlinked carbon network functioned effectively as a negative electrode in both potassium-ion batteries (PIBs) and sodium-ion batteries (SIBs), exhibiting high strain tolerance during potassiation/sodiation and maintaining stable cycling performance. Despite these advantages, the application of MOFs and their derivatives has largely been limited to LE-based battery systems. Particularly, the direct use of pure MOFs as low-strain materials in sulfide-based ASSBs, along with comprehensive electrochemo-mechanical analysis during the lithiation/delithiation process, remains underexplored. Therefore, detailed electrochemical and structural investigations are imperative to fully harness their potential and establish design protocols for high-performance MOF electrodes in ASSBs.In this work, we present a systematic screening of various 3d transition metal ions to identify the most promising MOF candidates for negative electrode applications in sulfide-based ASSBs. From these tests, we use two representative organic ligands, heterocyclic thiophenedicarboxylic acid (TPDC) and homocyclic benzenedicarboxylic acid (BDC), as model systems to elucidate the interplay between metal ions and organic ligands on the electrochemical performance of MOF in sulfide-based ASSBs. Our findings reveal that the Co-TPDC-MOF, featuring a thiophene group, exhibits better cyclability and a more reversible discharge/charge process compared to its benzene-based counterpart. We attribute this to the electronegative sulfur atom in the thiophene group facilitates a reversible charging/discharging process by providing favorable Li-ion migration pathways and minimizing Li-ion trapping within its organic matrix. To verify this, we investigate the lithiation/delithiation mechanisms of these MOF through a combination of X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and density functional theory (DFT) calculations. Furthermore, we perform a comparative mechanical analysis against conventional negative electrode materials (Li, Si, and Gr) via operando electrochemical pressiometry (OEP) and operando displacement measurement (ODM) to examine the near strain-free properties of the reported MOF electrodes during the cell operation. This is further validated by cross-sectional focused ion beam-scanning electron microscope (FIB-SEM), which reveals negligible volume change during the lithiation/delithiation process. Finally, using full cells, comprising the Co-TPDC-MOF, argyrodite Li6PS5Cl0.5Br0.5 (LPSClBr) SE, and LiNbO3-coated NCM811, we assess their electrochemical performance under practical conditions such as high loading capability, room temperature operation, and low stack pressure. These combined mechanical strain and mechanistic studies demonstrate the origin of their low mechanical strain properties and establish the groundwork for the practical application of MOF negative electrodes in sulfide-based ASSB systems.

ABSTRACT Due to their distinctive electronic configuration and chemical characteristics, transition metal ions exhibit a unique mechanism in the alteration of composite materials, making it a focal point in the study of lithium-ion battery anode materials. In this study, four kinds of transition metal ions doped graphite anode materials were prepared by rotating evaporation method using different kinds of transition metal ions and graphite as raw materials. The composites were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) for their structure and morphology. The influences of transition metal ions to the electrochemical properties of the composites have been examined by means of, electrochemical impedance test (EIS) and galvanostatic charge discharge test. The experimental results show that the electrochemical properties of transition metal ion doped composites are better than those of untreated graphite materials, and the electrochemical properties of nickel ion doped composites are significantly better than those of other materials, thus it is very promising application as anode materials for high-power lithium-ion batteries.

Negative electrode materials with high specific energy, such as SiGr, are essential to decrease battery cell weight and volume while allowing improved range and design flexibilities for electric vehicles. Among different SiGr anode prelithiation methods, the use of passivated lithium metal powder is discussed in terms of cell impedance and its effects on the interphase film formation on SiGr and LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC‐811) electrodes with high mass loadings. Electrochemical impedance spectroscopy analyses show that a less resistive and more effective solid electrolyte interphase (SEI) forms upon prelithiation which also benefits the charge transfer at the SiGr electrode. Scanning electron microscopy images show a thicker interphase layer with less interstitial porosity on the prelithiated SiGr electrodes and a thinner cathode electrolyte interphase on NMC‐811 electrode as a result of the lower average cathode potential attained throughout cycling, in comparison with the cells without prelithiation. A more diverse SEI layer, richer in beneficial components such as LiF, is promoted by the prelithiation method as shown by X‐ray photoelectron spectroscopy with a sputtering depth of 100 nm. Finally, it is shown that the more robust SEI layer forming upon prelithiation requires less electrolyte consumption for repairing the SEI layer throughout long‐term cycling.

Preparation and electrochemical performance research of four different morphologies of MnO2 negative electrode materials

Abstract Aluminum-air battery is a kind of energy storage device that use aluminum metal as the negative electrode material and oxygen in the atmosphere as positive reactant, and it is also usually called a power generation device of semi-fuel cell. Among the potential next-generation candidates, Ag catalysts are promising due to their high activity and low cost, but weaker oxygen adsorption has hindered industrialization. To address this bottleneck, Ag-alloying has emerged as a principal strategy. In this work, we successfully synthesized uniformly dispersed silver-coated copper (Cu@Ag) particles with BET surface areas ranging from 0.880 to 1.489 m 2 /g using a chemical displacement method, and applied them as catalysts with inherent oxygen reduction reaction (ORR) activity in metal-air batteries. Cu@Ag particles was mixed with MnO 2 in various ratios of 10:0 to 0:10. Results showed that 5 wt% Ag content yielded optimal thermal stability, and the best Cu@Ag:MnO 2 ratio was 3:7 that demonstrated the highest ORR activity by using CV analysis, with reduction potentials of −0.121 V and −0.124 V at scan rates of 20 and 50 mV/s, respectively. These findings suggest that Cu@Ag enhances catalytic efficiency and can improve power output in metal–air batteries.

Comparison of electrochemical and hydrogen storage performance of Mg-rich alloys as negative electrode materials in Ni-MH batteries

Abstract Currently, transition metal oxides (TMOs) are increasingly recognized as viable anode materials for lithium‐ion batteries (LIBs). Among them, V 2 O 5 has become a research focus in view of its high theoretical specific capacity, but its relatively low electrical conductivity and practical cycling capacity limit its application. It is shown that the amorphous V 2 O 5 ‐P 2 O 5 negative electrode material, due to its glassy structure, on the one hand, inhibits the volume strain and particle pulverization of graphite and vanadium components during charging and discharging processes and reduces the volume expansion phenomenon in battery cycling, and, on the other hand, the formation of ion‐conducting interfacial layer (PO 4 3 with Li⁺ ‐network) to promote lithium ion transport, which has a broad application prospect. Based on this, a series of (X) graphite‐(100‐X) vanadium‐pentoxide glass composite anode materials were prepared by mechanical ball milling method in this paper. The addition of graphite provides a stable layered structure and conductive network, realizes the reversible embedding/de‐embedding of lithium ions, improves the electrical conductivity of the composite materials, and reduces the charge transfer resistance of vanadium‐phosphorus glass anode materials in the cycling process. The performance of the five groups of composite anode materials showed an increasing and then decreasing trend, with the best performance observed in the 40% graphite‐60% vanadium‐based glass composites sample. Even after undergoing 500 cycles at 500 mA·g −1 , the material maintained high discharge and charge capacities of 509.3 and 510.2 mAh·g −1 , respectively, and the electrode sheet's surface remained relatively flat after cycling, with no obvious swelling, showing excellent cycling stability.

Silicon is a promising negative electrode material for high-energy batteries, but its volume changes during cell cycling cause rapid degradation, limiting its loading to about 10 wt.% in conventional graphite/Si composite electrodes. Overcoming this threshold requires evidence-based design for the formulation of advanced electrodes. Here we combine multimodal operando imaging techniques, assisted by structural and electrochemical characterizations, to elucidate the multiscale electro-chemo-mechanical processes in graphite/Si composite negative electrodes. We demonstrate that the electrochemical cycling stability of Si particles strongly depends on the design of intraparticle nanoscale porous structures, and the encapsulation and loss of active Si particles result in excessive charging current being directed to the graphite particles, increasing the risk of lithium plating. We also show that heterogeneous strains are present between graphite and Si particles, in the carbon-binder domain and the electrode's porous structures. Focusing on the volume expansion of the electrode during electrochemical cycling, we prove that the rate performance and Si utilization are heavily influenced by the expansion of the carbon-binder domain and the decrease in porosity. Based on this acquired knowledge, we propose a tailored double-layer graphite/Si composite electrode design that exhibits lower polarization and capacity decay compared with conventional graphite/Si electrode formulations.

With the rapid development of portable electronic devices and electric vehicles, metal-ion batteries, especially lithium/sodium/potassium-ion batteries (LIBs/SIBs/PIBs), have become a research hotspot because of their high energy density and cycle stability. The battery system primarily comprises three key components: negative electrode material, positive electrode material, electrolyte, and diaphragm. The selection of the negative electrode material will directly impact the battery's energy density. Among many anode materials, CoP has received widespread attention for its high theoretical capacity (894mAh g-1). However, cobalt phosphide faces challenges related to electrochemical instability, which stems from its poor intrinsic conductivity and substantial volume expansion during charge/discharge cycling. This article reviews the progress of CoP as an anode material for metal-ion batteries over the past decade. It discusses its electrochemical performance in LIBs/SIBs/PIBs, including specific capacity, cycling stability, and rate performance. In addition, the article discusses the synthesis methods and structural regulation of CoP, as well as the strategies to improve its electrochemical performance by constructing heterostructures and compositing with carbonaceous materials. Finally, the article points out the challenges in the current research and the future development direction, to provide theoretical guidance and experimental reference for the practical application of CoP in metal-ion batteries.