Charge Cycles Research Articles

In-Situ and in-Operando Li-Ion Batteries for Materials Science Education

Electrochemical energy storage systems, particularly Li-ion rechargeable batteries (LiRB), have a key role to play in fortifying US energy generation, decarbonizing the electricity sector, and limiting anthropogenic climate change. LiRBs suffer from limited lifetimes, insufficient energy densities, and fire risks, which are all materials science and engineering challenges stemming from various irreversible degradation processes occurring at nano and micro-scales. These batteries function via the reversible diffusion of Li ions from a Li-rich cathode to a Li-poor anode, each of which undergo various levels of volumetric phase changes, plastic deformation, and microcracking with each charging cycle, thereby compromising subsequent battery performance. Therefore, it is imperative to understand the nano-mechanical processes associated with LiRB degradation and predict transformative material designs that can lead to manufacturing cheaper, denser, and safer LiRBs. Such understanding and design would be instrumental to achieving the US 2050 Net Zero Goal. Additionally, the US lags 10x behind China in terms of Li battery manufacturing capability, and thus a LiRB-aware Research and Development workforce is paramount for continued US energy security. In this context, we propose a new design for in-situ and in-operando Li-ion battery research and education. This battery design will be used in a classroom/lab setting to discuss fundamental materials science concepts such as diffusion, grain-boundaries, and fracture. This activity will be used to broaden "missing millions" student participation in a crucial area of energy research at a minority serving institution.

Title: Investigation of Kinetically Favorable Chromium Speciation Distribution for Iron Chromium Redox Flow Batteries

Chromium is a promising active material for redox flow battery (RFB) electrolytes due to its low cost and reduction potential very near the negative limit of the electrochemical window of water. However, many challenges exist with the performance of the Cr3+/2+, most notably sluggish electron-transfer kinetics and parasitic hydrogen evolution during the charge cycle. This presentation will focus on our recent efforts to overcome these challenges by understanding the interplay between electrolyte composition, speciation, and electron-transfer kinetics for the aqueous Cr3+/2+ redox couple.Among the earliest published work on flow batteries was a program based at NASA introducing the iron chromium redox flow battery (ICRFB) [1,2]. These studies were valuable in demonstrating both the promise and the complications of chromium for flow battery electrolytes. The NASA team went to great lengths to enhance chromium redox kinetics and suppress the hydrogen evolution via extensive modification of the carbon negative electrode with Au, Pb, and Bi additives. The present study is based on a key observation from this early work that the electron-transfer rates for Cr-chloride complexes depend strongly on the inner-sphere coordination environment, and specifically the number of chloride ions directly bound to the Cr center.Extensive prior studies from the inorganic coordination chemistry literature further demonstrate that Cr(III) chloride complexes undergo slow equilibration in aqueous solutions to form distributions of four species where the coordination environment around the metal center can be described generally as [CrClx(H2O)6-x](3-x)+ with 0 < x < 3 [3,4]. Each of these species yields a distinct optical absorption signature, enabling quantification of the composition with UV-VIS spectroscopy. Our overarching hypothesis, based on the early NASA work, was that increased chloride coordination (i.e., higher values of x in CrClx(H2O)6-x) would yield enhanced electron-transfer kinetics by reducing inner-sphere reorganization barriers associated with aquo ligands, or by enhancing catalytic mechanisms mediated by chloride surface adsorbates. Thus, we measured optical absorbance and electrochemical reversibility for Cr(III) chloride solutions with HCl, NaCl, and LiCl supporting electrolytes over a range of total chloride concentration from 0.1 to ~10 mol/L.Representative results are summarized in Figure 1 for 0.1 M CrCl3 in aqueous LiCl. Notably, at Au electrodes the reversibility of the Cr3+/2+ redox feature increases dramatically as chloride concentration increases above 5 mol/L (Figure 1a). This shift in reversibility is broadly correlated with UV-VIS results (Figure 1b) demonstrating that the primary Cr(III) species present initially remains the predominant species in the aqueous environment for high concentrations of chloride over time, but the predominant species shifts significantly at lower concentrations of LiCl. Ongoing work, which will be discussed in this presentation, is focused on full quantification of the relationship between speciation and electron-transfer kinetics as well as performance properties for ICRFBs with a range of supporting electrolyte concentrations. We anticipate that understanding the most kinetically favorable speciation distribution will allow us to develop improved electrolytes for functional ICRFBs.

Voltammetric Study of Phase Separating Anode Materials in Li-Ion Battery Using Phase Field Model

The increasing demand for higher energy capacity in lithium-ion batteries has underscored the significance of modeling lithiation with alternative electrode materials, such as silicon (Si) and tin (Sn). This research addresses the need for comprehensive insights into the (dis)charging process, particularly focusing on the intricate phase transformations in the anode. Phase-field modeling has proven effective in capturing these transformations [2], revealing volumetric deformations of up to 300% during (dis)charging cycles [1]. Unfortunately, these deformations compromise material integrity, leading to reduced battery cycle life and reliability.To address these challenges, our work presents a novel framework for modeling lithiation in materials exhibiting two-phase diffusion using phase field modeling. Unlike previous models limited to single-phase diffusion, our framework provides a more realistic representation of the diffusion process. This realism is achieved by incorporating the time-dependent voltage applied to the anode, a crucial factor in understanding the electrochemical response during lithiation [3].Furthermore, we leverage the currents generated during the lithiation and delithiation processes to conduct a comprehensive voltammetric study. This study goes beyond existing research by considering the impact of phase separation on the currents developed during Li-ion battery operation. Our findings aim to contribute valuable insights into optimizing battery performance and addressing challenges associated with phase transformations, ultimately advancing the development of high-capacity anodes for lithium-ion batteries. REFERENCES [1] McDowell M. T., Lee S. W., Nix W. D., Cui Y. 25th Anniversary Article: Understanding the Lithiation of Silicon and Other Alloying Anodes for Lithium-Ion Batteries. Adv. Mater., Vol. 25 (36), pp. 4966–4985, 2013.[2] Chen L., Fan F., Hong L., Chen J., Ji Y. Z., Zhang S. L., Zhu T., Chen L. Q. A Phase-Field Model Coupled with Large Elasto-Plastic Deformation: Application to Lithiated Silicon Electrodes. J. Electrochem. Soc., Vol. 161 (11), pp. F3164–F3172, 2014.[3] Swaminathan, N., Balakrishnan, S., & George, K. Elasticity and Size Effects on the Electrochemical Response of a Graphite, Li-Ion Battery Electrode Particle. Journal of The Electrochemical Society, 163(3), A488–A498, 2016. Figure 1

Current-Dependent Lithium Metal Microstructure in ‘Anode-Free’ Solid-State Batteries at the Steel|LPSCI Interface

Further improvement of energy densities of state-of-the-art batteries could be achieved with the utilization of lithium metal anodes.1 Due to the reactivity of the alkali metal, the fabrication process needs to be monitored carefully. To circumvent degradation during storage as well as the handling of lithium metal, reservoir-free cells (RFCs) are investigated.2 Using accessible lithium stored within lithiated cathode materials, the lithium anode is formed in a formation step during the first charging cycle. The electrochemical properties of the electrodeposited lithium film are strongly dependent on its microstructure, and can, for example, influence the resoluble amount of lithium during subsequent cycling.3,4 Until now, the microstructure of electrodeposited lithium and how to control it is elusive.To observe and characterize the microstructure of electrodeposited lithium at the stainless steel|LPSCl interface, a combination of electrochemical impedance spectroscopy, focused ion beam and scanning electron microscopy as well as electron backscatter diffraction was used. With this setup, the correlation between deposition current density and resulting microstructure of the lithium film was investigated. For higher current densities, a twenty times smaller grain size was observed, while the grain density showed a twelvefold increase, which could have a major influence on the subsequent dissolution of lithium. Furthermore, the microstructural evolution during prolonged lithium deposition was investigated.1 J. Janek and W. G. Zeier, Nat. Energy, 2016, 1, 16141.2 M. J. Wang, E. Carmona, A. Gupta, P. Albertus and J. Sakamoto, Nat Commun., 2020, 11, 1–9.3 S. E. Sandoval and M. T. McDowell, Matter, 2023, 6, 2101–2102.4 D. K. Singh, T. Fuchs, C. Krempaszky, B. Mogwitz, S. Burkhardt, F. H. Richter and J. Janek, Adv. Funct. Mater., 2023, 33, 2211067.

Characterization of Degradation Mechanisms of Alternative Electrolytes Solutions in Fast Charging Li-Ion Batteries

While the idea that fast charging batteries could be utilized in electric vehicles is enticing, current fast charging batteries face significant challenges that must be mitigated before this application is realized. Fast charging batteries currently suffer from capacity loss and degradation over time which not only affects battery life but poses a safety hazard. The current electrolyte, 1.2 M LiPF6 in 3:7 wt.% EC/EMC (Gen2), contains the salt LiPF6 that when exposed to moisture can form dangerous hydrofluoric acid and contains a carbonate-based solvent that when exposed to oxygen can ignite. In addition, batteries experience degradation over many cycles of fast charging which results in capacity fade and poor battery performance. However, previous studies have shown the potential for other electrolyte systems to mitigate these problems, specifically by using highly concentrated electrolytes1. These studies claim that using these electrolytes results in the formation of a solid electrolyte interphase (SEI) that passivates Li ions better than the Gen2 electrolyte. The SEI is a layer that forms on the anode within the battery and serves as a protective layer that allows for Li intercalation into graphite and can therefore protect against degradation. By using different electrolytes, a different SEI is formed, and different degradation mechanisms are observed. In this way, the SEI can be tuned to improve Li passivation and ionic conductivity by changing the electrolyte’s composition and concentration2. This research focuses on such alternative electrolyte systems and aims to characterize the different degradation mechanisms corresponding to each electrolyte. Favorable performance has been observed using 1.2 M LiFSI in 3:7 wt.% EC/EMC as an electrolyte. We are studying LiFSI in acetonitrile (AN) at higher concentrations than traditional Gen2 to quantify the SEI. We expect AN to form an anion derived SEI, a composition of which results in improved passivation of Li ions1. In this study, we characterize degradation of alternative electrolyte systems through x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Through these methods we can observe and quantify both crystalline, amorphous degradation products due to loss of Li inventory and loss of active material. XPS allows quantification of compositional changes in the SEI layer at the surface of the electrode. The SEM provides qualitative information on degradation such as visualizing lithium plating and dendrite formation. We implement quantitative XRD to measure the crystalline phases of the graphite anode, showing the degree of lithium intercalation and further quantifying degradation such as Li plating. Putting the results of these three characterization techniques together in tandem with electrochemical cycling data paints a picture of the degradation that happens on the anode of a fast-charging lithium-ion battery with respect to electrolyte composition.[1] Yamada, Y., Wang, J., Ko, S., Watanabe, E., & Yamada, A. (2019). Advances and issues in developing salt-concentrated battery electrolytes. Nature Energy. [2] Logan, E. R., & Dahn, J. R. (2020). Electrolyte Design for Fast-Charging Li-ion Batteries. Trends in Chemistry.

Cyclability Improvement of Recycled Graphite Materials in Lithium-Ion Batteries Via Conductive Polymer Coating

In recent years, lithium-ion batteries have been widely adopted in electric vehicles and electronics. However, the growing number of retired lithium-ion batteries poses a significant environmental challenge, generating substantial material waste and potential pollution. In most commercial batteries, graphite is the prevalent choice for anode material, owing to its high electrical conductivity and mechanical stability. Therefore, recycling graphite from spent lithium-ion batteries is a potential solution to eliminate the waste and meet the increasing demand.While considerable attention has been directed toward recovering metallic components of the spent lithium-ion batteries, limited effort has been dedicated to recycling graphite. Some previously developed methods include the pyrometallurgy process and hydrometallurgy process. However, due to high energy consumption and environmental pollutions, these methods have not been applied in large scales. Additionally, graphite particles have experienced various aging mechanisms during charge and discharge cycles, such as the formation of a solid electrolyte interface (SEI) and the intercalation of solvent molecules, potentially leading to structural alterations and degradation. Hence, it is advisable to implement surface treatment to enhance capacity stability if the recycled graphite does not perform optimally following the recovery treatment.In this study, we developed a simple process to recycle spent graphite utilizing aqueous and organic wash with N-Methylpyrrolidone (NMP) and toluene, followed by surface coating with the conductive polymer poly(9,9-dioctylfluorene-co-fluorenone-co-methylbenzoic ester) (PFM). The surface coating served as a protective layer of graphite particles and a charge transport agent to enhance conductivity. The morphologies and structures of the pristine, recycled, and PFM-coated recycled graphite samples were measured by X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis.To investigate the impact of employing PFM as a binder, electrochemical tests were done using anodes with both recycled graphite and PFM-coated recycled graphite. In recycled-graphite||NMC532 full cell testing, cells with PFM-coated recycled graphite exhibits higher coulombic efficiency (>99.90%) than cells without PFM coating at a rate of 0.33 C. A capacity retention of 77.49% was achieved for PFM-coated cells after 300 cycles, whereas the ones without coating have a capacity retention of 70.21% in average. Rate tests were also conducted on both the cells with and without PFM-coating. It shows that both types of cells support high-rate cycling. About 85% of charge capacity was delivered for cycling at 1 C for both cells with and without PFM-coating.Overall, the recycling method can be easily operated with minimal waste production, low energy consumption, and low economical costs. The PFM coating on the recycled graphite particles leads to enhancement of mechanical strength and efficiency in battery cycling.Fig. A, The process scheme of recycling graphite; B, Pictures of an electrode from spent lithium-ion batteries (left) and an electrode fabricated with recycled graphite (right); C, Capacity retention of recycled graphite without PFM coating (blue) and with PFM coating (green); D, Coulombic Efficiency of recycled graphite without PFM coating (blue) and with PFM coating (green). Figure 1

Prediction of Lithium Deposition By Electrochemical Noise Method in Li-Ion Batteries

Electrochemical noise measurement methods have established a significant presence in corrosion literatures and through these measurements, it becomes feasible to discern the corrosion mode and make a clear distinction between localized and uniform corrosion types, particularly when examined alongside post-mortem studies.In recent years, the increase in the use of lithium-ion batteries demands that the tests to be performed on the batteries are faster, easier, cheaper and, if possible, non-destructive and non-perturbing. While some electrochemical noise studies on batteries have commenced, the existing literature on this subject is limited and questionable. Electrochemical noise measurement, in Lithium based batteries has the potential to serve as a non-invasive diagnostic tool for assessing battery health. One of our previous studies has demonstrated an increased voltage noise in non-rechargeable batteries with Li/MnO2 chemistry upon exposure to a short circuit, indicating detectable morphological changes in metallic lithium due to non-homogenous depletion of lithium anode through electrochemical noise measurement.In Lithium-Ion batteries, lithium deposition refers to the undesired formation of metallic lithium, commonly in the form of dendrites, on the battery’s anode during charge and discharge cycles. This phenomenon is a consequence of uneven lithium-ion plating and stripping, leading to localized overplating. This growth of lithium dendrites poses significant risk, including internal short circuits, compromised battery integrity, and the potential for thermal runaway. These issues can result in reduced battery performance, safety concerns, and shortened cycle life. Effectively addressing lithium deposition is essential for enhancing the safety and reliability of lithium-ion batteries in various applications.Similarly to our previous publication, the electrochemical noise method shows promise as a non-invasive approach to investigate the understand deposition of metallic lithium by monitoring the voltage noise during charge and discharge cycling of batteries. For this purpose, NMC/Graphite pouch and coin cells are employed. In this presentation, we will delve into the details of electrochemical noise in lithium-based batteries, discussing the method’s reliability in assessing lithium deposition in NMC/Graphite lithium-ion batteries and presenting preliminary results. Figure 1

Current Collector Primers with Improved Physical and Electrochemical Properties

Lithium-ion batteries are the dominant technology for powering the growing markets of electric vehicles, consumer electronics, and grid storage. However, to meet the increasing demands for higher energy density, faster charging, lower cost, and longer cycle life, continued research of new materials and designs are required. One of the key components that affects the performance and durability of lithium-ion batteries is the current collector, which provides a conductive substrate for active materials. The interfacial conductivity, adhesion, and corrosion resistance of these foils is largely dictated by their native oxide surface layer. To improve any of these features, specialized primers may be applied prior to electrode manufacturing, presenting a unique electrode/active material interface. For instance, carbon-coatings may be applied to aluminum to improve the conductivity and adhesion of lithium iron phosphate (LFP) formulations. These carbon coatings are limited in their cost, thickness, and performance, particularly in next generation cell designs and application methods. PPG is exploring novel current collector coating technologies addressing the physical, electrochemical, and stability requirements of these chemistries and manufacturing process. In this presentation, we will elaborate on coatings development and the effect that novel primer layers have on mechanical properties and single-layer pouch cell cycle life.

Amorphous Cobalt Tin Oxide/Reduced Graphene Oxide Decorated on Graphite Felt as Positive Electrode for Vanadium Redox Flow Battery

The Vanadium Redox Flow Battery (VRFB) stands out as one of the most promising large-scale energy storage systems. Nevertheless, the graphite electrode materials commonly used in VRFBs often exhibit drawbacks such as limited electrochemical activity and insufficient conductivity, ultimately resulting in suboptimal performance for the VRFB. In this study, we utilized highly conductive reduced graphene oxide (rGO) as a carrier for cobalt tin oxide (CoSnO3), aiming to enhance their catalytic capability towards vanadium ions. CoSnO3/rGO composite was confirmed using XRD and TEM, revealing nanoboxes morphology and amorphous structure. XPS and EPR analysis showed an increase in oxygen vacancies after composite formation. In order to further prove the effect of CoSnO3/rGO composite catalyst modified graphite felt, the modified graphite felt electrode was applied to the positive electrodes of VRFB, and the charge and discharge tests at different current densities were carried out. At a current density of 160 mA/cm², the composite demonstrated a voltage efficiency of 74.22%, surpassing the heat treated graphite felt by 2.69%. Noteworthy enhancements in capacitance were also evident at this specific current density. Furthermore, stability testing over 50 cycles revealed no significant degradation, underscoring the superior performance and outstanding durability of the CoSnO3-rGO modified graphite felt throughout charge and discharge cycling. The result of this study highlight the promising potential of CoSnO3-rGO composites as efficient catalysts for vanadium redox flow batteries, providing improvements in electrochemical performance and long-term stability.

Chloride Adsorption on Au (111) Electrodes

There are still numerous open questions with regards to adsorption phenomena and partial charge transfer at electrode interfaces. The dynamic nature electrode structure and adsorbate ordering makes an analysis solely based on thermodynamic considerations limited. Here we present recently collected data with such an analysis, using different concentrations of chloride anions in both acidic and neutral electrolytes, for well-defined Au (111) electrodes. Cyclic voltammograms and charge density data is obtained. Then the electrocapillary equation: "-dγ = σMdE + ΓCl-RTdln(cKCl)" is used to get the relative interfacial tension plot and later the electrosorption valency. In the future we will improve on this by more accurately placing the PZC of charge density measurements, using laser induced temperature jump transients and combining our interpretation with state-of-the-art molecular-dynamics using ground state machine learned potentials. Figure 1

(Invited) Enhanced Catalysis of Surface-Activated Metallic WSe2 Nanosheets By Single-Atom Pt for High-Performance Li-O2 Battery

Layered materials, such as TMDCs, exhibit various electronic structures attributed to their polymorphism and can be further modificated at the atomic level through chemical treatments. TMDCs in the metallic phase (1T or 1T’ phase) have gained attention as efficient electrocatalystic materials, due to their exceptional transport properties compared to TMDCs in the semiconducting phase (2H phase). TMDCs with the metallic phase have been prepared by atomic-scale post-treatments, such as an intercalation and single-atom doping. However, the precise role of these post-treatments in the catalytic performance of TMDCs is still ambiguous, as it is uncertain whether the enhanced properties arise from charge transfer kinetics in metallic phase or electrochemical properties induced by the post-treatment.Herein, we present a straightforward approach fabrication for fabricating metallic WSe2 nanosheets, which serve as an excellent support for single-atom Pt doping. The incorporation of single-atom Pt into WSe2 nanosheets was achieved using a simple solution method at room temperature. Extensive measurements were conducted, including XAS, XPS, and XPDF to investigate the local coordination structure of Pt-WSe2. These measurements confirmed the presentce of single-atom Pt doping within WSe2 layers. The introduction of single-atom Pt significantly enhanced the kinetics of the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), leading to improved performance of Li-O2 batteries. Experimental measurements and DFT calculations provided evidence that the enhanced catalytic abilities of Pt-WSe2 originated from the improved interaction between oxygen and the Se vacancy on basal planes of WSe2. Consequently, the Li-O2 battery incorporating the Pt-WSe2 catalyst exhibited a stable discharge and charge cycle for up to 350 cycles, demonstrating its superior durability.

Correlating Gas Composition and Electrochemical Data from First Formation Cycle of Lithium-Ion Batteries

The solid electrolyte interface (SEI) plays a crucial role for the performance and lifetime of lithium-ion batteries. It consists of decomposition products from electrolyte components (salt, solvent and additives) and is initially formed during the first charging process called the formation cycle. The chemical processes creating the SEI are a matter of current research. A better understanding of these reactions and their implications on cell performance can provide new ways to optimise the formation process. This can help reducing costs while increasing lifetime and performance of lithium-ion batteries.In this contribution we apply statistical correlation analysis on a large set of cells to gain new insights on the connection between formation and cell-performance. Cells (NMC622|Graphite, 1 Ah, ordered from LiFun) are divided in three groups. The groups differ only by the electrolyte. An electrolyte solution with EC:EMC (3:7 by wt.) and 1 M LiPF6 serves as a baseline. The other two groups use the same solvent and salt concentration but contain an additional 5% fluor ethylene carbonate and vinylene carbonate, respectively.All cells underwent the same formation procedure. It consists of a formation cycle with C/5 at 80°C, followed by a degassing-step and 9 subsequent cycles with the same current rate at 45°C. After these ten cycles a reference performance test (RPT) is conducted, including qOCV, capacity and pulse-resistance tests. During the degassing step gas samples from half of the cells were analysed using GC-MS.An incremental capacity analysis of the formation cycle shows clear distinctions between the three different electrolytes. Distinct peaks below 3 V are found for each group. The gas composition demonstrates that cells containing additives contain a higher share of carbondioxide and carbonmonoxid amid a substantially lower share of ethylene, compared to the cells without additives.The large number of over 100 cells in total enables a systematic correlation analysis. We investigated the correlation between features extracted from the first formation cycle and the RPT. In addition, correlations between electrical data from the first cycle and the relative amount of carbon-containing gasses in the samples are analysed.Correlations differ for the three groups of cells, however some common trends were observed. We found a negative correlation between the average voltage during formation and the difference between the capacity of the first discharge and the capacity measured in the RPT. This difference represents the loss over the 9 cycles at 45°C. It is positively correlated with the first discharge capacity indicating that lower lithium-losses in the first cycle are countered by higher losses in subsequent cycles.Correlations between gasses and electrical data from the formation cycle provide new insights into the chemical processes. If the shares of two gasses are positively correlated, we assume that the reactions producing these gasses are linked. We found such strong positive correlations for the shares of CH4, C2H6, C2H4 and CO in the case of VC-containing electrolyte. In this group the share of carbondioxide is negatively correlated to these gas-shares.Correlating the different gas-shares with the charge throughput in different voltage windows (during wetting at 1.5V, during the formation charge cycles from 1.5 to 3V, 3 to 3.8V, and 3.8 to 4.2 V, respectively), we found very different patterns for the three groups. VC-containing cells show weak or very weak correlations with all four charge-throughput values, with the exception of a moderate negative correlation between CO. Cells without additives show a moderate correlation between the wetting charge and the CO2-share. Cells containing FEC exhibit a moderate positive correlation between the share of CO2 and the charge throughput between 1.5 and 3.8 V.The combination of electrical data with the gas composition and statistical analysis provides a new way to improve our understanding of the SEI formation and the complex chemical reactions. Our results indicate that gasses generated by the decomposition of VC are not influenced by small changes of charge throughput during formation, whereas a higher charge-throughput at lower voltages in cells containing FEC correlates with an increased share of CO2.

Stable Hydroborate Solid-State Lithium Battery with High-Voltage NMC811 Cathode

Hydroborate solid electrolytes offer high ionic conductivity and are stable in contact with alkali metal anodes, but are challenging to integrate into batteries with high-voltage cathodes [1-3]. Here, we demonstrate stable dis-/charge cycling of solid-state lithium-ion batteries combining a Li3(CB11H12)2(CB9H10) hydroborate electrolyte with a 4 V-class LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode, exploiting the enhanced kinetic stability of the LiCB11H12-rich and LiCB9H10-poor electrolyte composition [4]. Cells with lithium metal and indium/lithium anodes achieve a discharge capacity at C/10 of ~145 mAh g–1 at room temperature and ~175 mAh g–1 at 60 °C. Indium/lithium cells retain 98% of their initial discharge capacity after 100 cycles at C/5 and 70% after 1000 cycles at C/2. Capacity retention of 97% after 100 cycles at C/5 and 75% after 350 cycles at C/2 is also achieved with a graphite anode without any excess lithium. The energy density per cathode composite weight of 460 Wh kg–1 is on par with the best solid-state batteries reported to date.[1] L. Duchêne, A. Remhof, H. Hagemann, D. Battaglia, Energy Storage Materials, 2020, 225, 782[2] L. Duchêne, R.-S. Kühnel, E. Stilp, E. Cuervo Reyes, A. Remhof, H. Hagemann, C. Battaglia, Energy & Environ. Science, 2017, 10, 2609[3] R. Asakura, D. Reber, L. Duchêne, S. Payandeh, A. Remhof, H. Hagemann, C. Battaglia, Energy & Environ. Science, 2020, 13, 5048[4] H. Braun, Ryo Asakura, A. Remhof, C. Battaglia, ACS Energy Lett. in press

(Invited) Evolution of the Solid Electrolyte Interphase in Si Nanoparticle Based Li-Ion Battery Anodes: Insights from Ab Initio Simulations of Core-Level Spectroscopies

Silicon nanoparticles (c-Si NPs) are considered promising candidates for the active material in Si-based anodes, offering high gravimetric capacity and helping to mitigate volume expansion effects. However, the formation of an unstable Solid Electrolyte Interphase (SEI) around the nanoparticles leads to increased irreversible lithium consumption, resulting in reduced capacity and poor cycling stability. In this context, core-level spectroscopies are established techniques to assess the evolution and composition of the SEI. While X-ray spectroscopies provide valuable insights into atomic and electronic structures, interpreting them in complex systems could be challenging, highlighting the need of theoretical insights from ab-initio approaches. Our study focuses on the changes occurring in c-Si NPs and the SEI during the initial charge cycle, leveraging post-mortem core-level spectra at various states of charge (SOC). We employ a multi-edge analysis coupled with a fitting approach based on known experimental references and theoretical simulations. Additionally, we demonstrate how comparing experimental spectra with theoretical references allows tracking changes at the NP level, including amorphization and surface oxidation. Finally, we discuss some of the limitations of our theoretical description and propose addressing them through machine learning approaches. This work is supported by the European Union’s Horizon 2020 research and innovation program (BIG-MAP, Grant No. 957189, also part of the BATTERY 2030+ initiative, Grant No. 957213).

Improved Wide Temperature and Rate Performance in Li-Ion Batteries with Fluorinated Electrolyte Solvents

Commercial electrolytes include organic solvents unable to withstand the conditions required for the rapidly growing Li-ion battery industry, such as extreme temperatures and charge rates. The thermal and electrochemical stability limits of these solvents restrict the development of Li-ion batteries needed to sustain automotive electrification and other industrial applications. Further efforts are needed to enable electrolyte formulations suited for the operational demands in the market.Koura has designed a series of fluorinated materials for use in Li-ion electrolytes that demonstrate improved performance and safety over conventional commercial electrolytes. The impact of Koura’s fluorinated solvents on performance in 4.3V Gr/NMC811 was examined, with a particular focus on benefits seen on extreme temperature and rate performance. Testing included cycling and rate performance across a range of temperatures from -20 °C to 45 °C and cycling conditions from C/2 to 4C. It has been found that these materials improve low temperature performance and reduce gassing and increase capacity retention during high-temperature and fast charge cycling. Where appropriate, performance of Koura materials is compared to common commercial solvents.To elucidate the mechanisms responsible for the observed improvements, comprehensive post-test analysis has been conducted, including gas composition analysis and quantification via gas chromatography, bulk electrolyte composition analysis via NMR spectroscopy, and surface layer characterization via XPS and SEM. Bulk transport properties of the materials and electrolytes, including conductivity, viscosity, and Li+ solvation, are correlated to performance benefits.This presentation will show Koura’s efforts to fill a major gap in the demands of the Li-ion battery industry today through the design of fluorinated materials and optimization of advanced electrolyte formulations. Specifically, we will present data highlighting the performance of fluorinated compounds on improving battery performance under strenuous conditions with respect to both temperature and cycling rate. Results from fundamental mechanistic studies will be discussed to highlight the mechanisms underlying the observed performance improvements.

Particle Shape Resilient Framework for Long-Lasting Li-Ion Batteries

The lattice structural dynamics of active materials within Li-ion batteries, contingent upon their state of charge (SoC), introduce challenges associated with volume expansion or contraction in a both particle and electrode levels1-2. This phenomenon induces mechanical fractures and alters electrode thickness, particularly problematic for high-Ni cathodes characterized by pronounced c-lattice changes during cycling, leading to substantial mechanochemical degradation and hindrance to long-term cycle retention3-4. This study proposes a resilient framework employing multi-wall carbon nanotubes to decorate the surface of active particles, imparting recoverable characteristics to high-Ni cathode materials. This surface framework, endowed with the capacity to absorb mechanical energy, effectively preserves the original secondary particle shape throughout multiple charge cycles, mitigating the serve propagation of cracking. Additionally, the control of particle shape alterations results in a noteworthy reduction of over 50% in electrode thickness changes. The consequential impact of this elastic framework particle engineering is exemplified by outstanding performance, even in a carbon-additive-free electrode with a density of 20 mg/cm². The battery exhibits superior cycle life, retaining 85% of its initial capacity after 500 cycles in a pouch cell. This advancement establishes a universal paradigm for the systematic design of Li-ion batteries with markedly extended cycle life, presenting a transformative prospect for robust and enduring energy storage W. Li, E. M. Erickson, A. Manthiram, Nat. Energy 5 , 26-34 (2020). J. Langdon, A. Manthiram, Energy Stor. Mater. 37 , 143-160 (2021). W. Li, H. Y. Asl, Q. Xie, A. Manthiram, J. Am. Chem. Soc. 141 , 5097-5101 (2019). X.-H. Meng, T. Lin, H. Mao, J.-L. Shi, H. Sheng, Y.-G. Zou, M. Fan, K. Jiang, R.-J. Xiao, D. Xiao, J. Am. Chem. Soc. 144 , 11338-11347 (2022).

Compression Testing of Individual Battery Electrode Particles

The friability of powder materials used to fabricate battery electrodes is an important parameter in determining battery lifetime. Particulate electrode materials are subject to significant stresses during cell fabrication. While in use, battery cyclic charging and discharging induces mechanical stresses in the electrode materials which can significantly impact long-term stability.Our presentation will describe a novel micro-compression instrument and technique for determining the compression strength of individual particles as small as 1 micron in diameter. Brief examples of the technique used to characterize and compare the hardness of battery anode materials will be discussed. Further in-depth references will also be provided.

Visualization and Quantification of State of Charge-Dependent Young's Modulus of LiMn2O4 Nanosized Particles by Bimodal AFM.

Mechanical damage of LiMn2O4 active material caused by volume change, phase transition, and lithium diffusion-induced stress is the main degradation mechanism in lithium-ion batteries. Young's modulus is a key parameter of mechanical property, and its variation with lithium content x or state of charge (SOC) at the nanoscale is an important issue because such variation may have influences on the stress level and lithium-ion transport. In this study, we successfully developed bimodal atomic force microscopy (bimodal AFM) and related approaches to carry out surface topography imaging and Young's modulus mapping of LixMn2O4 nanosized particles. It was validated that the size of particles decreased with decreasing SOC due to delithiation during the charging cycle. The variation in Young's modulus with SOC was quantitatively determined using the silicon material as a reference, and the trend of the variation is consistent with the reported results of molecular dynamics simulation. Furthermore, spatially nonuniform distribution of Young's modulus on the nanosized particle surface was found even upon completion of charging. This phenomenon could be attributed to the coexistence of two phases during the charging process. Our experimental study reveals the correlation between Young's modulus of LiMn2O4 and SOC at the nanosized particle level, and we believe that the bimodal AFM will be widely used in the nanocharacterization of the electrode materials because lithium content- or SOC-dependent mechanical properties are common in battery electrode materials.

Electro-Chemo-Mechanical Evolution at the Garnet Solid Electrolyte-Cathode Interface.

Solid-state batteries promise higher energy density and improved safety compared with lithium-ion batteries. However, electro-chemomechanical instabilities at the solid electrolyte interface with the cathode and the anode hinder their large scale implementation. Here, we focus on resolving electro-chemo-mechanical instability mechanisms and their onset conditions between a state-of-the-art cathode, LiNi0.6Mn0.2Co0.2O2 (NMC622), and the garnet Li7La3Zr2O12 (LLZO) solid electrolyte. We used thin-film NMC622 on LLZO pellets to place the interfacial region within the detection depth of the X-ray characterization techniques. The experimental probes of the near-interface region included in operando X-ray absorption spectroscopy and ex situ focused ion beam scanning electron microscopy. Electrochemical degradation was not observable during cycling at room temperature with 4.3 V versus Li/Li+ charge voltage cutoff, or with stepwise potentiostatic hold up to 4.1 V versus Li/Li+. In contrast, secondary phases including reduced transition metal species (Ni2+, Co2+) were found after cycling up to 4.3 V versus Li/Li+ at 80 °C and during potentiostatic hold at 4.3 V versus Li/Li+ (Ni2+). Intergranular cracks between NMC622 grains and delamination at the NMC622|LLZO interface occurred readily after the first charge. These interface reaction products and mechanical failure lowered the capacity and cell efficiency due to partial loss of the NMC622 phase, partial loss of contact at the interface, and a higher polarization resistance. Electrochemical instability between delithiated NMC622 and LLZO could be mitigated by using a low charge voltage cutoff or cycling at lower temperature. Ways to engineer the mechanical properties to avoid crack deflection and delamination at the interface are also discussed for enhancing mechanical stability.

Advanced rigid carbazole-based membranes assembled with flexible piperidine alkyl chains for neutral aqueous organic redox flow battery

Neutral aqueous organic redox flow battery (NAORFB) represents a highly promising energy storage device. However, one of its challenges is the need for high Cl− conductivity, highly stable ion-selective membranes. In this work, N-methylpiperidine-modified carbazole-based long side chain anion exchange membranes (QPCEP-x) were designed and prepared. The rigidity and hydrophobicity provided by the carbazole on the main chain, in conjunction with the flexibility and hydrophilicity provided by the alkyl-piperidine groups on the side chains, resulted in the observed excellent microphase separation properties of the prepared membranes. The prepared membranes exhibited excellent overall performance, with QPCEP-1 achieving a Cl− conductivity of 20.33 mS cm−1 at 25 °C. In NAORFB, the energy efficiency of QPCEP-1 ranges from 91.7 % to 62.4 % at 20–160 mA cm−2, far exceeding the 89.1 %–38.4 % of commercial AMVN. Furthermore, long-term cell cycling tests demonstrate that the energy efficiency of QPCEP-1 remains unchanged at 82.7 % at 60 mA cm−2 after 10,000 complete charge and discharge cycles, exceeding the majority of cycles reported in literatures. These findings suggest that QPCEP-x has significant potential for use in NAORFB.