Cathode Electrolyte Research Articles

Rapid Desolvation and Anti-Reduction Electrolyte Enables High-Performance Lithium Metal Batteries

Lithium metal batteries (LMBs) have attracted widespread attention due to their potential for high-energy-density storage applications. However, the sluggish kinetics of traditional carbonate electrolytes at the electrode interface and severe side reactions between electrodes and electrolytes impedes the practical implementation of LMBs. Herein, we design a fast desolvation and anti-reduction electrolyte to achieve high-performance LMBs by tuning the solvation structure of Li+. The incorporation of bis(trifluoromethanesulfonyl)imide (TFSI−) and difluorophosphate (DFP−) anions into the solvation structure of Li+ mitigates the reactivity of the electrolyte with Li metal, promoting the anti-reduction capability of the electrolyte. In addition, the interaction between Li+ and solvent molecules as well as anions is weakened, which reduces the desolvation energy of Li+. Furthermore, the proposed anions can be preferentially sacrificed to form an inorganic-rich cathode electrolyte interphase (CEI), thereby inhibiting the oxidative decomposition of the electrolyte and the dissolution of transition metal (TM) elements. Therefore, the reversibility of the Li anode is improved to 97.8% and the Li||NCM622 cell exhibits a capacity retention of 78.3% after 250 cycles at 1 C. Even at a high loading or 3 C rate, the Li||NCM622 cells also demonstrate exceptional electrochemical performance.

New information about the cyclable capacity fading process of a pouch cell with Li-rich layered oxide cathodes.

Most studies investigate the cyclable capacity fading mechanism of Li-rich layered oxides (LLOs) from the microscopic structure level, lacking discussions about how the structure degradation influences the performance of the pouch cell precisely and quantitatively. Based on the analysis of the evolution of key parameters during the whole cycling period, a new transition-type fading mechanism is proposed. From the early-to-middle stage of the cycling period, polarization increases, most of which is interface-related, causing about 67% of the whole capacity loss. From the middle-to-late stage of the cycling period, active material losses turn out to be the dominating factor, inducing about 61% of the total capacity loss. Diffusion-related polarization, replacing the interface type, is responsible for most of the increased overpotential. Relative analysis confirms that during the early stage, the increase of the charge transfer resistance, induced by CEI (cathode electrolyte interface) growth and initial surface layered-structure degradation, is the main source of interface polarization. As the cycling evolves to the late stage, severe bulky structure degradation, including lattice-oxygen release, Li/Ni mixture and generation of a new spinel phase, turns out to be the major factor, causing further capacity fading.

Mechanically and Thermally Stable Cathode Electrolyte Interphase Enables High‐temperature, High‐voltage Li||LiCoO2 Batteries

AbstractThe development of high‐energy‐density Li||LiCoO2 batteries is severely limited by the instability of cathode electrolyte interphase (CEI) at high voltage and high temperature. Here we propose a mechanically and thermally stable CEI by electrolyte designing for achieving the exceptional performance of Li||LiCoO2 batteries at 4.6 V and 70 °C. 2,4,6‐tris(3,4,5‐trifluorophenyl)boroxin (TTFPB) as the additive could preferentially enter into the first shell structure of PF6− solvation and be decomposed on LiCoO2 surface at low oxidation potential to generate a LiBxOy‐rich/LiF‐rich CEI. The LiBxOy surface layer effectively maintained the integrity of CEI and provided excellent mechanical and thermal stability while abundant LiF in CEI further improved the thermal stability and homogeneity of CEI. Such CEI drastically alleviated the crack and regeneration of CEI and irreversible phase transformation of the cathode. As expected, the Li||LiCoO2 batteries with the tailored CEI achieved 91.9 % and 74.0 % capacity retention after 200 and 150 cycles at 4.6 and 4.7 V, respectively. Moreover, such batteries also delivered an unprecedented high‐temperature performance with 73.6 % capacity retention after 100 cycles at 70 °C and 4.6 V.

Toward a high-voltage practical lithium ion batteries with ultraconformal interphases and enhanced battery safety

Nickel-rich layered lithium transition metal oxides, LiNixCoyMn1-x-yO2, are key cathode materials for high-energy lithium–ion batteries owing to their high specific capacity. However, the commercial deployment of nickel-rich oxides is hampered by their parasitic reactions and the associated safety issues at high voltages. Developing a stable cathode–electrolyte interphase (CEI) is a promising strategy to overcome this problem. Herein, we report a novel approach, based on the in situ polymerization reaction, to build a protective polymer skin on LiNi0.6Co0.2Mn0.6O2 (NCM622) cathode materials. The artificial CEI skin was found to drastically improve the intrinsic thermal stability, mitigate the evolution of phase transition, and effectively inhibit the associated parasitic reactions between cathodes and the electrolyte in the high-charge states. This coating approach leads to enhanced capacity retention and battery safety under high-voltage operations. The CEI design concept offers a promising strategy for develop advanced nickel-rich cathodes for batteries.

ZIF-67-derived FeCoNi-LDH with a 3D nanoflower hierarchical structure for highly efficient oxidation of 5-Hydroxymethylfurfural and coupling seawater splitting hydrogen production

To achieve clean and sustainable energy development, the thermodynamically favourable electrocatalytic oxidation reaction of biomass derivatives can be combined with electrolysis for hydrogen production. This process simultaneously generates high-value 2,5-furandicarboxylic acid and green energy (i.e., hydrogen). The present thesis focuses on the synthesis of a novel Fe-Co-Ni nanosheet catalyst foam using impregnation methods and one-pot hydrothermal techniques. Subsequently, the 3D nanoflower FeCoNi-S@NF catalysts are subsequently prepared by sulfurizing the FeCoNi-LDH@NF precursors. These catalysts were then employed for electrolytic seawater hydrogen production coupled with the electrocatalytic oxidation of 5-hydroxymethylfurfural (HMFOR). This strategy is expected to address the slow kinetics of the oxygen evolution reaction (OER). The 3D nanoflower structure of the FeCoNi-S@NF catalyst enhances the exposure of catalytically active sites, while sulfur doping further improves the electron transfer ability. At a low reaction potential of 1.45 V vs. RHE, FeCoNi-S@NF exhibited remarkable performance with a 95.68 % conversion rate for 5-hydroxymethylfurfural (HMF), a 94.83 % yield for 2,5-furandicarboxylic acid (FDCA), and a Faraday efficiency of 94.71 %. Furthermore, FeCoNi-S@NF exhibits a remarkable response in terms of hydrogen evolution in seawater. By utilizing HMFOR as the anodic reaction and low-cost seawater as the cathodic electrolyte for the hydrogen evolution reaction (HER), simultaneous biomass upgrading and hydrogen production can be achieved. Incorporating HMFOR into a two-electrode system for the electrolytic seawater hydrogen production process significantly reduces the needed voltage (1.70 V@10 mA cm−2), thereby potentially decreasing the cost of this process.

Polycarbonate-Based Solid-Polymer Electrolytes for Solid-State Sodium Batteries.

Solid-polymer electrolytes comprised of polypropylene carbonate (PPC) and varied sodium bis(fluorosulfonyl)imide (NaFSI) salt concentrations are investigated for implementation as a conductive solid polymer electrolyte into solid-state cathode composites utilizing a sodium-layered oxide active material. The ionic conductivity generally increases with NaFSI salt content, reaching ≈1mScm-1 at 80°C at the highest salt concentration (PPC:NaFSI = 0.5:1). Through an all-in-one slurry casting method, Na2/3Ni1/3Mn2/3O2 cathode composites are fabricated in which the dispersed PPC electrolyte acts as the primary binder. Enabled by a bilayer polymer electrolyte system, cycling performance with the PPC cathode electrolyte is optimized with respect to salt concentration and anode material. The best cyclability is achieved with a moderate salt concentration electrolyte (PPC:NaFSI = 5:1), showcasing an initial capacity of 83mAhg-1 with a remarkable 80% capacity retention after 150 cycles at C/5 rate and 60°C. The superior performance of the lower salt concentration electrolyte is attributed to better electrochemical stability, as confirmed by linear sweep voltammetry and online electrochemical mass spectrometry measurements. These results underscore the potential of carbonate-based polymer electrolytes and the importance of balancing electrolyte conductivity and stability in cell design.

Nanoarchitectonics for a long-life and robust Na-ion battery at low temperature with Prussian blue cathode and low-concentration electrolyte

Na-ion batteries are considered as promising battery systems for large-scale energy storage. Although Na-ion batteries exhibit enhanced low-temperature cycling performance compared with lithium-ion batteries, there is still a great challenge to overcome for practical low-temperature applications. In this work, we propose a low-performance Na-ion battery composed of FeNi co-doped Mn-based Prussian cathode (FeNi-MnHCF) and a low-concentration electrolyte (0.5 mol L−1) containing a small amount of 2,2,2-trifluoroethyl acetate (ETFA, 1 wt%). The introduction of ETFA could decrease the viscosity, increase ionic conductivity and change the solvation structure of the electrolyte at low temperature. ETFA could also participate in constructing a uniform, stable, and Na-ion conductive CEI layer, enabling rapid Na-ion transport and effective protection of FeNi-MnHCF. The cells with the ETFA-contained electrolyte and FeNi-MnHCF cathode exhibit excellent rate capability and long cycle life at low temperature. When being cycled at −20 °C, the cell with ETFA could retain 92.1 % of the capacity after 1120 cycles at 1 C. The cell could also show stable cycling after overcharge to 4.8 V or overdischarge to 1.2 V at −20 °C. This work sheds light on the design of long-life and robust Na-ion batteries for sustainable energy storage at low temperature.

Modifying Surface Chemistry to Enhance the Electrochemical Stability of Nickel‐Rich Cathode Materials

AbstractResidual impurities such as lithium carbonate and hydroxide are a major concern for accelerating parasitic reactions at the cathode electrolyte interface of lithium‐ion batteries. Removal of these lithium‐bearing species becomes a necessity for high‐performance nickel‐rich cathode materials. Instead of directly removing these impurities through washing steps, a wet impregnation process is employed to convert these detrimental surface impurities into beneficial surface coating on nickel‐rich cathode materials. Specifically, the pristine cathode material is treated with Al(H2PO4)3 solution to convert undesired compounds into Li3PO4 and AlPO4, both of which are considered positive surface coating materials for high‐voltage cathodes. It is found that the introduced modification greatly suppresses the interfacial impedance hike and improves the capacity retention of the cathode material after repeating charging/discharging. It is believed that these benefits are realized through the modification of the surface chemistry of the cathode material, which helps to slow down the parasitic reactions and reduce the damage to the cathode material.

Blended Salt Electrolyte Design for Enhanced NMC811||Graphite Cell Performance

The high energy density, nickel‐rich layered cathode material LiNi0.8Mn0.1Co0.1O2 (NMC811) is recognized as a promising candidate for next‐generation battery chemistries. However, due to their structural and interfacial instability, nickel‐rich NMC cathodes still face a number of challenges in practical application. For this reason, the design and development of novel electrolyte formulations, able to stabilize the nickel‐rich cathode|electrolyte interface, are highly demanded. In this work, a novel electrolyte is developed using lithium (difluoromethanesulfonyl) (trifluoromethanesulfonyl)imide (LiDFTFSI) and lithium hexafluorophosphate (LiPF6) as salt blend in an organic carbonate‐solvent based solvent mixture. The presence of LiDFTFSI notably enhances the electrochemical performance of the resulting NMC811||graphite cells. Further advancement of the considered cell chemistry is achieved by introducing the well‐known functional electrolyte additive vinylene carbonate (VC), which was found to feature a synergistic effect with LiDFTFSI. The formation of a homogenous, effective, and robust solid electrolyte interphase (SEI) as well as cathode electrolyte interphase (CEI) on the corresponding electrodes resulted in superior electrochemical performance.

Evolution Process of the Interfacial Chemical Reaction in Ni-Rich Layered Cathodes for All-Solid-State Batteries.

All-solid-state batteries (ASSBs) have attracted much attention in the fields of energy storage, electric vehicles, and portable electronic devices due to their safety and high energy density. Ni-rich layered ternary materials (LiNi1-y-zCoyMnzO2, 1 - y - z ≥ 0.7) are considered to be among the most promising candidates for cathode materials in ASSBs due to their unique advantages. Nevertheless, the interfacial chemical reaction between the ternary cathode (NCM) and solid-state electrolytes (SSEs) has become the main issue to limit the long-cycle stability of the cathode. Relative studies have shown that when NCM materials are in direct contact with sulfide-based SSEs, byproducts generated by the interfacial chemical reaction accumulate at the interface, resulting in increasing interfacial impedance. However, up to now, the formation mechanism of the NCM/SSE interfacial chemical reaction, as well as its properties and evolution process, still lacks detailed characterization. In this paper, batteries at different stages during the long-cycling process are characterized to reveal the dynamic evolution process of the chemical reaction from the cathode-electrolyte interface to the interior of the particle and to determine the chemical reaction effect on the irreversible degradation of the battery capacity. On this basis, a surface coating of LiNbO3 is adopted to establish a passivation protection layer at the cathode-electrolyte interface. The coated battery has been subjected to 2000 charge/discharge cycles at a rate of 1 C and achieved a capacity retention rate of up to 82%.

A Hauser-base modulated boron-based electrolyte empowering superior interfacial chemistry in rechargeable magnesium batteries

Electrolytes with superior Mg plating/stripping performance and cathode compatibility through a simple synthetic pathway and affordable raw materials have become a long-term pursuit of rechargeable magnesium batteries (RMBs). Herein, an efficient Hauser-base modulated boron-based electrolyte TMPLB is proposed via a facile in-situ one-pot method that involves mixing intrinsic LiCl-containing Hauser-base TMPL (2,2,6,6-tetramethylpiperidinylmagnesium chloride lithium chloride complex) and Lewis acid B(Otfe)3 (tris(2,2,2-trifluoroethyl)borate) in tetrahydrofuran (THF). Nuclear magnetic resonance (NMR) results reveal that the TMPLB electrolyte is mainly composed of active cation [Mg2(μ-Cl)3·6THF]+ and anion [(TMP)B(Otfe)3]−. In addition to a conducive solid electrolyte interphase (SEI) formed on Mg, the in-situ generated robust cathode electrolyte interphase (CEI) on cycled Mo6S8 jointly endows excellent Mg2+ transfer kinetics and cycling stability. Specifically, Mo6S8||Mg full cells can be cycled for over 3000 cycles with a superior capacity retention of 88.2 mAh g−1 under 5 C. The TMPLB electrolyte paves an avenue for the building of stable electrode/electrolyte interfaces in future practical long-life RMBs.

(Invited) First Principles Examination of Multiple Criteria of Organic Solvent Oxidative Stability in Batteries

Oxidative instability of the liquid electrolyte at or near battery cathode oxide surfaces has significant detrimental effects on batteries. Organic solvent molecules are often the fuel and precurors of such degradation processes, releasing electrons and protons that react with cathode oxides and electrolyte anions. These reactions contribute to cathode electrolyte interphase (CEI) film formation, transition metal ion dissolution, and phase transformation of the surface regions of the cathode. Here we apply Density Functional Theory calculations to examine four criteria of oxidative stability (oxidation potential, hydrogen removal energies, and initial reactivity on two types of oxide facets) using four different solvent/additive molecules (ethylene carbonate, fluoroethylene carbonate, 1,3-dioxolane, and dimethyl ether). The ranking of molecular stability differs with each criterion. Surprisingly, the all-oxygen terminated basal planes of layered oxides exhibit lower reaction barriers than spinel surface facets with exposed transition metal cations, especially for ether solvents; the calculations also suggest basal planes contribute to the dissolution of transition metal ions. The structure-degradation relation complexity underscores the challenge of understanding the function of the CEI, but also offers a guide to future degradation-mitigation strategies including facet-engineering. Our predictions and models help establish a framework for future studies relevant to high voltage conditions.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. This paper describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the document do not necessarily represent the views of the U.S. Department of Energy or the United States Government.

Exploring Battery Materials for Ca Batteries

Rechargeable calcium (Ca) batteries have the prospects of high energy, low-cost and sustainability. Ca metal has a low reduction potential of -2.9 V vs. NHE (close to that of lithium -3.0 V)) and a high capacity, and thus the voltage and energy density of Ca batteries is potentially comparable with lithium-ion batteries. However, divalent Ca-ions and reactive Ca metal strongly interact with cathode materials and electrolyte solutions, leading to high charge-transfer barriers at the electrode-electrolyte interfaces and consequently low electrochemical performance. Herein, we will present the recent progress in the development of stable calcium tetrakis(hexafluoroisopropyloxy) borate Ca[B(hfip)4]2 (hfip = CH(CF3)2) electrolytes and the search for suitable cathode materials. We will discuss the interfacial properties of Ca anodes in liquid electrolytes and the chemistry of sulfur conversion electrodes in Ca batteries. References Li, O. Fuhr, M. Fichtner, Z. Zhao-Karger, Towards stable and efficient electrolytes for room-temperature rechargeable calcium batteries.Energy Environ. Sci. 12, 3496 (2019).Li, Z. M. Fichtner, Z. Zhao-Karger, Rechargeable Calcium–Sulfur Batteries Enabled by an Efficient Borate-Based Electrolyte. Small 16, 1–6 (2020).Zhao-Karger, Y. Xiu, Z. Li, A. Reupert, T. Smok, M. Fichtner, Calcium-tin alloys as anodes for rechargeable non-aqueous calcium-ion batteries at room temperature, Nature Comm. 13, 3849 (2022).

LIOVIX® Printable Lithium Technology for Lithium Anode Manufacturing at Scale

The commercialization of lithium metal batteries requires the mass production of cost-effective thin lithium metal foil with thickness less than 30 µm. However, today’s known technologies are not yet commercially available. For example, thin lithium metal foil can be produced by hydraulic extrusion followed by a rolling process. This process usually requires a delicate balance between the pressure and tension created by both extruder and winder, so that the resulting foil is not torn or stretched, retaining all the dimensional characteristics required. This process can be extremely challenging when making lithium metal films with thickness less 20 µm due to the poor mechanical properties of lithium metal. Lithium metal foil can also be produced by physical vapor deposition (PVD). Lithium metal foil produced by PVD process are generally homogenous and have good control in thickness. However, PVD technology requires high vacuum chamber and is slow in the deposition rate, typically in the range of 0.1 to 100 nm s−1, making industrial scale of 20 µm lithium foil very challenging1.Livent has developed LIOVIX®printable lithium technology, a proprietary formulation that combines Stabilized Lithium Metal Powder (SLMP®), rheology modifiers and solvent to produce a stable suspension that can be printed on most common substrates. LIOVIX®printable lithium technology is an enabling technology that can produce thin lithium foil with thickness of 5 µm to 50 µm with no limitation in width, length and at high deposition speed. LIOVIX®enables pattern printing and can be applied to any substrate, for example a prefabricated anode, cathode, current collector, separator, and solid or polymer electrolyte. This technology enables 3D battery printing in a custom form factor shape.In this presentation, we will cover thin lithium foil manufacturing processes using standard industrial equipment and electrochemical performance results.References Acebedo, Begoña, et al. "Current Status and Future Perspective on Lithium Metal Anode Production Methods." Advanced Energy Materials (2023): 2203744.

Transition-Metal Interdiffusion in Solid-State Batteries Revealed By Cryo-TEM

Solid-state lithium-ion batteries are being considered as a future energy-storage technology, with superior energy/power density and improved safety over conventional lithium-ion batteries. However, their commercial implementation is hampered by side reactions and electro-chemo-mechanical degradation occurring during cycling (mostly at the positive electrode side). Many efforts have been made to reveal the underlying mechanisms in order to alleviate such problems.In the current study, the Thermo Scientific IGST workflow solution was used to enable a DualBeam to TEM workflow by protecting both bulk sample and prepared lamella under argon atmosphere with a CleanConnect transfer module. Because of the beam and temperature sensitivity of the superionic lithium thiophosphate solid electrolyte and the cathode interphases formed during cycling, the lamella preparation process (incl. bulk milling, lift out, attachment to the TEM grid, and final thinning) was carried out at cryogenic temperature (−178 °C). The lamella was then transferred to a Talos F200X CFEG for TEM analysis using an inert gas sample transfer workflow.STEM and EELS investigations revealed Ni, Co, and Mn dissolution from a Ni-rich cathode and subsequent solid electrolyte poisoning. Transition-metal dissolution/migration during cycling operation has previously only been reported for conventional (liquid-electrolyte-based) batteries.

Rechargeable Zn−MnO2 Batteries: Progress, Challenges, Rational Design, and Perspectives

AbstractAs a new type of secondary ion battery, aqueous zinc‐ion battery has a broad application prospect in the field of large‐scale energy storage due to its characteristics of low cost, high safety, environmental friendliness, and high‐power density. In recent years, manganese dioxide (MnO2)‐based materials have been extensively explored as cathodes for Zn‐ion batteries. Based on the research experiences of our group in the field of aqueous zinc ion batteries and combining with the latest literature of system, we systematically summarize the research progress of Zn−MnO2 batteries. This article first reviews the current research progress and reaction mechanism of Zn−MnO2 batteries, and then respectively expounds the optimization of MnO2 cathode, Zn anodes, and diverse electrolytes and their effects on battery performance. Additionally, primary challenges related to different components and their respective strategies for mitigating them are discussed, with the ultimate objective of offering comprehensive guidance for the design and fabrication of high‐performance Zn−MnO2 batteries. Finally, the future research and development direction of aqueous Zn−MnO2 batteries with high energy density, high safety and long life is envisioned.

In-Situ Confocal Microscopy to Analyze Volume Expansion of Solid State Microbatteries

The rise of embedded objects put great interests in miniaturized power supply solutions. Solid State Microbatteries (SSM) are the most promising, as they can safely store high energy and power density. SSM have the advantage of being all-solid (no liquid leakage and flammability), to have low self-discharge and good cyclability. Despite the strong interest in the field, the mechanisms of Li plating and stripping at the anode are not well observed and not yet fully understood [1]. The study of these phenomena would bring new insights to mechanical behavior during cycling and therefore may lead to optimization approaches at the cycle life level. In this purpose, we investigated the morphological change of SSM during the charge/discharge cycle. We looked at the influence of the cathode thickness and the packaging. Thick LiCoO2 layers were used for the study with thickness from 5 to 30 µm. Volume variations upon cycling were followed thanks to a Neox microscope 3D (Sensofar) and were correlated to charge/discharge capacity.Microbatteries are consisting of LiCoO2 (LCO) cathode and LiPON electrolyte. The anode-free configuration was adopted for integration compatibility. The anode is formed in-situ during the first charge operation. Wafers with different LCO thickness and back end level have been carried out. Confocal microscope was setup in Ar-filled glovebox to monitor the volume expansion during the charge and discharge operations. SSM cycling was operated through Biologic instruments. Figure 1 depicts a schematic representation of the SSM and the setup. Images were acquired during chrono-amperometric full charge at 4.2 V and galvanostatic full discharge at Idischarge = -3.5 µA within 3-4.2 V.Charge/discharge operations and corresponding in-situ thickness variations are presented in Figure 2 for the samples with different LCO thickness. The complete charge is achieved when current reaches a threshold of 0.5 µA. Charge capacity linearly increased with cathode thickness: Qcharge = 2.0 µA.h for the 5-µm-LCO and Qcharge = 9.6 µA.h for the 30-µm-LCO. Thickness variation increase follows the same evolution as capacity during charge and discharge. Regardless of the cathode thickness, same plating and stripping speed are observed during charge and discharge operation, respectively. According to the Qcharge and the volume variation, a theoretical lithium density at the anode side has been observed for all LCO thickness.Figure 3 depicts 2D images of 5-µm-LCO SSM at the onset of the charge. Pristine SSM presents a smooth surface (Fig. 3.a). Li plating is initiated with nucleated grains (Fig. 3.b). Then, grains grow and tend to coalesce with each other, forming a uniform and smooth Li layer (Fig. 3.c). Figure 4 reports 2D images of 30-µm-LCO SSM at different states of cycling. Bumps at the edge formed during the charge are due to SSM device architecture: electric field bends and the increased ion flux induces a more important Li accumulation on the edge. Otherwise, a uniform and fully dense Li metal deposition is realized in solid-state configuration under zero external pressure [2]. At the end of discharge, the battery thickness is higher than the pristine one (+ 3.7 µm). The Li plating non-reversibility phenomena after the first charge is due to low diffusion coefficient at low state-of-charge [3].Figure 5 shows the electrical behavior (Fig 5.a) and the volume expansion (Fig 5.b) of a SSM over 10 cycles. After the first cycle, cycling is performed at ≈100% coulombic efficiency, demonstrating high reversibility of the phenomena and so high cyclability of SSM [3].Finally, we followed the influence of the encapsulation layers on the volume variation. 2D images of the SSM reveals same volume variation for both samples. Those observations suggest that the encapsulation layers has no significant mechanical effect on the Li plating.In-situ confocal microscopy under Ar atmosphere has been proved efficient to study the volume expansion of SSM upon cycling and is a promising technique to investigate failure mechanisms of SSM.[1] J. Park et al., « In situ atomic force microscopy studies on lithium ( de ) intercalation-induced morphology changes in Li x CoO 2 micro-machined thin fi lm electrodes q », J. Power Sources, vol. 222, p. 417–425, 2013, doi: 10.1016/j.jpowsour.2012.09.017.[2] D. Cheng et al., « Freestanding LiPON: from Fundamental Study to Uniformly Dense Li Metal Deposition Under Zero External Pressure », arXiv.org, 8 août 2022. https://arxiv.org/abs/2208.04402v2.[3] J. Celè, S. Franger, Y. Lamy, et S. Oukassi, « Minimal Architecture Lithium Batteries: Toward High Energy Density Storage Solutions », Small Weinh. Bergstr. Ger., p. e2207657, janv. 2023, doi: 10.1002/smll.202207657. Figure 1

Rechargeable Zinc–Air versus Lithium–Air Battery: from Fundamental Promises Toward Technological Potentials

AbstractAs battery technologies that can potentially increase the energy density and expand application scenarios of the lithium‐ion batteries, rechargeable metal‒air batteries have attracted extensive research interests. Among a variety types of metal anodes investigated, zinc (Zn)‒air and lithium (Li)‒air batteries hold best prospects for real‐world applications and attract the most scientific community interests. It has been more than 10 years since Cho et al. first compared Li–air and Zn–air batteries, during which great progress has been made. In this review, these two representative metal‒air battery technologies are compared in view of the most recent progresses and improvements in the last decade, especially efforts that push these technologies toward real world applications. It starts with the fundamentals of Zn–air and Li–air batteries, and discusses the progress made in electrolyte design, anode protection, and cathode catalysts development. It ends with an evaluation of the current research state along with an overall future perspective. Such a comprehensive comparison of typical non‐aqueous and aqueous battery systems with a focus on practical application criteria would be a timely review of metal‒air battery development in the last decade, which shed light for fundamental and applied research, eventually leading to real‐world application.

Synergistic Impact of Electrolyte Components: Interplay between the Novel Phosphorus-Based Additives and Conducting Salt Advancing NMC811||SiC Cell Performance

A lithium-ion battery (LIB) typically consists of an anode, a lithiated transition metal oxide cathode, and an electrolyte formulation containing inorganic lithium conducting salt in aprotic organic solvents/co-solvents, and functional additives. In-depth research is being conducted in order to develop novel chemistries for the next-generation LIBs. Within the line, silicon-based anodes and nickel-rich cathodes are recognized as two feasible next-generation electrode materials. The long-term galvanostatic cycling performance of resulting cell chemistries relies on the effectivity and robustness of solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) formed during the initial cycles and originate from the galvanostatic cycling conditions, as well as the complex interplay between electrolyte and corresponding electrodes .[1] To enhance the SEI and CEI properties, implementing functional electrolyte additives into baseline electrolyte has been shown to be one of the most effective and cost-favorable strategies. Film-forming additives sacrificially reduce and/or oxidize at corresponding electrodes to form protective layers (SEI and CEI).Previous research has shown that phosphorus-based additives improve electrode |electrolyte interfaces stability and simultaneously enhance cell flame-retardant capability advancing the overall cell performance.[2,3] In this report, we indicated part of the above-mentioned properties originate from the synergy between lithium hexafluorophosphate (LiPF6) which is the state-of-the-art (SOTA) electrolyte conducting salt in LIBs and considered functional additives. Here, we demonstrated the functionality of 2-phenoxy-1,3,2-dioxaphospholane (PhEPi) as a novel film-forming additive[4] and 2,2,4,4,6-pentafluoro-6-(2,2,2-trifluoroethoxy)-1,3,5,2λ5,4λ5,6λ5-triazatriphosphinine (CF3PFFPN) as a new flame-retardant additive, synthesized for the first time by our group. The presence of PhEPi and CF3PFPN at the optimum concentrations in the baseline electrolyte (1 M LiPF6 in EC: EMC 3:7 + 8 % VC) enhances the performance and safety of the resulting NMC811||Si-graphite (20% Si) cell chemistry. Impact of phospholane-based additive was confirmed by substituting LiPF6 with LiBF4 conducting salt and complementary post mortem analysis. This study along with improved cell chemistry, provided a better understanding and deeper insights into the synergistic interplay and impact of considered electrolyte components on the resulting NMC811||Si-graphite cell chemistry. [1] C. Wölke, B. A. Sadeghi, G. G. Eshetu, E. Figgemeier, M. Winter, I. Cekic-Laskovic, Advanced Materials Interfaces 2022, 9, DOI 10.1002/admi.202101898.[2] N. Von Aspern, D. Diddens, T. Kobayashi, M. Börner, O. Stubbmann-Kazakova, V. Kozel, G. V. Röschenthaler, J. Smiatek, M. Winter, I. Cekic-Laskovic, ACS Applied Materials and Interfaces 2019, 11, 16605–16618, DOI 10.1021/acsami.9b03359.[3] N. von Aspern, C. Wölke, M. Börner, M. Winter, I. Cekic-Laskovic, Journal of Solid State Electrochemistry 2020, 24, 3145–3156, DOI 10.1007/s10008-020-04781-1.[4] B. A. Sadeghi, C. Wölke, F. Pfeiffer, M. Baghernejad, M. Winter, I. Cekic-Laskovic, Journal of Power Sources 2023, 557, 232570, DOI 10.1016/j.jpowsour.2022.232570.

Effect of Oxygen Functionalities inside Carbon Micropore on Lithium-Sulfur Battery Performance

Introduction Lithium-sulfur batteries (LSB) using a sulfur cathode with a high specific capacity (1672 mAh g-1) have been regarded as one of the most promising candidates for large-scale energy storage systems, while the sulfur cathode's drawback hinders the commercial application of LSB. Soluble Li2Sx (x = 4 – 8) generated during a charge-discharge process dissolves into electrolytes, which induces LSB's self-discharge and capacity decay. The main efforts to overcome this issue have been on physical confinement of sulfur in the pores of porous carbons [1,2]; however, carbon materials, being non-polar in nature, interact weakly with the polar Li2Sx, which still leads to low cycle stability of LSB. Hence, the surface modification to porous carbon, which provides polar-polar interaction between the carbon surface and Li2Sx, has been performed, suppressing the Li2Sx dissolution and improving LSB's performance [1,3].On the other hand, we reported that polar-oxygen functionalities on microporous carbon (MC), which are generated with oxidants, significantly improve the discharge capacity of LSB [4]. The formation of Li2Sx (x = 4 – 8) is inhibited in micropores (pore diameter < 2 nm) [5]; therefore, the oxygen functional groups probably improve the discharge capacity of LSB assembled with a MC-sulfur composite cathode due to factors other than the suppression effect of Li2Sx dissolution. Our previous study revealed that oxygen functionalities on the MC surface contribute to the enhanced electrochemical performance of the LSB by preventing electrolyte decomposition and thus decreasing the resistance of the cathode electrolyte interface (Rcei) [6]. However, the ratio of Rcei to the total resistance of the LSB is small; the oxygen functional groups would improve the performance of LSB by affecting other resistance. Herein, we investigate the effect of surface oxygen functionalities on charge transfer resistance (Rct) and Li+ diffusion of LSB. Our report would provide deep insight into the surface modification of carbon materials as LSB’s cathode. Method 2.1. Preparation of Oxidized MC-Sulfur composite MC was added into 69 wt.% HNO3 and refluxed at 120ºC for 2 h (Ox MC). Washed and dried Ox MC was mixed with sulfur at a weight ratio of 48: 52. The mixture was heated at 155ºC for 5 h (Ox MC-S). 2.2. Assembling of Cells To obtain the Ox MC-S cathode, the slurry prepared by mixing the Ox MC-S, acetylene black, carboxymethyl cellulose, and styrene butadiene rubber at a weight ratio of 89: 5: 3: 3 was coated on an Al foil. The cells with the Ox MC-S cathode and Li metal anode were assembled in a glove box. Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI): tetraglyme (G4): 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropylether (HFE) = 10: 8: 40 (by mol) was used as the electrolyte. 2.3. Activation Energy Measurement with Electrochemical Impedance Spectroscopy (EIS) To elucidate the effect of oxidation treatment on the Rct and Warburg impedance (Rw) of Li-S batteries, activation energy measurement was carried out at 2.5 V in the 50th charging process. The temperature range was 0 – 25°C, and the alternating current voltage amplitude was 10 mV. Rw was investigated with the calculation of the Warburg coefficient (σ). Major results and conclusion The activation energy of Rct (Ect) and σ were determined to investigate the effects of oxygen functional groups formed at MC surfaces on charge transfer processes and Li+ diffusion. While Ect increased from 0.65 to 0.72 eV by oxidation treatment, the frequency factor increased from 17.7 to 20.9; this indicates that the oxygen functional groups improve the number of reaction sites where three substances (carbon, active material, and electrolyte) come into contact with each other. The σ of MC-S and Ox MC-S were 281.2 and 178.9 Ω s-1/2, respectively. Therefore, a decrease in Rw due to oxygen functional groups was suggested.The charge transfer process and Li+ diffusion occur inside the microporous carbon particles where the confined sulfur is present. We processed the Ox MC-S particle from the cathode after the 50th charging using focused ion beam (FIB) milling to obtain a cross-section and observed it with STEM-EELS. This result will also be reported in our presentation.This work was supported by “Advanced Low Carbon Technology Research and Development Program, Specially Promoted Research for Innovative Next Generation Batteries (ALCA-SPRING [JPMJAL1301])” from JST.[1] X. Ji et al., Nat. Mater., 8 (2009) 500.[2] T. Takahashi et al., Prog. Nat. Sci., 25 (2015) 612.[3] L. Yoshida et al., Electrochim. Acta, 429 (2022) 141000.[4] S. Okabe et al., Electrochemistry, 85 (2017) 671.[5] Y. Xiao et al., RSC Adv., 10 (2020) 39875.[6] L. Yoshida et al., 242nd ECS Meeting s, Z01-2299 (2022).