We present a modular instrument for dispersive X-ray absorption spectroscopy (DXAS) developed for the Advanced Spectroscopy Beamline at Sector 25 of the Advanced Photon Source. The setup employs a double-multilayer monochromator to provide X-rays with a broad energy bandwidth, Kirkpatrick–Baez mirrors for focusing, a convexly bent Bragg-crystal polychromator for energy dispersion, and a pixel-array detector to resolve all X-ray energies and collect their intensity simultaneously, thereby enabling acquisition of a full X-ray absorption spectrum in a single shot. The use of separate optics for X-ray focusing and energy dispersion provides high spatial resolution and avoids chromatic aberrations inherent in focusing bent-crystal optics, and a modular design makes implementation of the technique at other beamlines possible without requiring modifications to the upstream beamline configurations. Theoretical calculations are performed to determine optimal instrument operating parameters and demonstrate that an energy resolution better than the K-edge core-hole lifetime broadening can be maintained while providing a sufficient bandwidth for X-ray absorption near-edge structure spectroscopy through the full operating range of 5–11 keV. Additionally, instrument design, data analysis methods, and initial DXAS results on lithium–manganese–nickel oxide laminates are presented.

X-ray absorption near edge structure (XANES) spectroscopy is a powerful technique for characterizing the chemical state and symmetry of individual elements within materials, but requires collecting data at many energy points which can be time-consuming. While adaptive sampling methods exist for efficiently collecting spectroscopic data, they often lack domain-specific knowledge about the structure of XANES spectra. Here we demonstrate a knowledge-injected Bayesian optimization approach for adaptive XANES data collection that incorporates understanding of spectral features like absorption edges and pre-edge peaks. We show this method accurately reconstructs the absorption edge of XANES spectra using only 15–20% of the measurement points typically needed for conventional sampling, while maintaining the ability to determine the x-ray energy of the sharp peak after the absorption edge with errors less than 0.03 eV, the absorption edge with errors less than 0.1 eV; and overall root-mean-square errors less than 0.005 compared to traditionally sampled spectra. Our experiments on battery materials and catalysts demonstrate the method’s effectiveness for both static and dynamic XANES measurements, improving data collection efficiency and enabling better time resolution for tracking chemical changes. This approach advances the degree of automation in XANES experiments, reducing the common errors of under- or over-sampling points near the absorption edge and enabling dynamic experiments that require high temporal resolution or limited measurement time.

Lead acid batteries (LABs) are widely used in SLI (Starting, Lighting, and Ignition) and stationary applications due to their low cost, high recyclability, and robust safety. However, their operational challenges-low specific capacity, limited cycling life, and active material degradation-continue to constrain long-term performance. In this study, we employed synchrotron X-ray microtomography and energy dispersive diffraction (EDD) to investigate the chemo-mechanical evolution of LAB cells during formation and cycling. Our custom-designed cells mimic actual LAB structures while enabling operando analyses. The observed decrease in utilization after each cycle is consistent with both electrochemical tests and EDD patterns, and this degradation is further confirmed by tomographic imaging. The positive and negative electrodes undergo distinct active materials conversion and gas evolution, resulting in different void evolution behaviors. Additionally, the positive electrode's current collector develops a corrosion layer, whereas the negative electrode exhibits a volume increase. These findings underscore the complex interplay of active materials conversion, gas evolution, and electrode morphology in determining LAB performance, offering new insights into degradation mechanisms and informing strategies for improved LAB design.

The evolution of chemical phenomena induced by high-temperature cathode synthesis significantly impacts cathode performance and stability. Reliable methods to measure and quantify heterogeneous elemental and oxidation states within battery cathodes are essential to ensure that process conditions yield the desired architectures. In this talk, we present two investigations where nondestructive three-dimensional transmission X-ray microscopy (TXM) was employed to examine cathodes synthesized with full compositional gradients (FCG) for surface and structural stabilization, as well as direct recycling processes involving relithiation and upcycling. By integrating TXM with differential X-ray absorption spectroscopy (XAS) and Ni X-ray Absorption Near Edge Spectroscopy (XANES), we fully quantified the relationship between particle location and elemental content, demonstrating high statistical significance. In the first study, FCG materials were designed with gradients of increasing manganese content and decreasing nickel content from the secondary particle core to the surface. After high-temperature lithiation, elemental compositions evened out due to elemental diffusion, but gradients remain. In the direct recycling study, cathode materials from manufacturing scrap and end-of-life batteries were recovered intact. Relithiation processes were employed to resolve lithium deficiencies and rejuvenate the material for reuse. Cathode upcycling through Ni addition was also performed to produce cathodes with higher energy density. The desired end products for both relithiation and upcycling are cathodes with homogeneous elemental content; however, limitations in elemental diffusion can cause inefficient conversion. The methodology presented should be used to guide synthesis while ensuring that electrochemical performance is linked to precise elemental distributions at the nanoscale.

A deeper understanding of the thermodynamics and kinetics governing the lithiation and layering mechanisms of NMC cathode materials (LiNi x Mn y Co z O2, where x + y + z = 1) offers valuable insights for enhancing synthesis methods and improving cathode performance. By employing atomistic and mesoscale approaches informed by in situ powder X-ray diffraction (PXRD) experiments, critical parameters for comprehending lithiation and layering processes and reaction rates were identified. The mesoscale approach captured the evolution of the phases and crystallite size observed in the in situ PXRD, revealing the differences in reaction rates with the use of different lithium salts and starting precursors. Ab initio molecular dynamics (AIMD) underscored the importance of vacancies and structural defects in promoting ion mobility and facilitating the nucleation of a layered domain. This nucleation disrupts the symmetry of disordered phases, ultimately creating a strained phase that serves as a buffer between layered and disordered regions. The lithiation and layering processes reflect a dynamic balance between the thermodynamic drive for a low-energy layered structure and the kinetic of diffusion, which is influenced by temperature and lithium vacancy concentration. Overall, reaction mechanisms are driven by the inherent defects of the intermediate phase that differ for NMC cathode materials. The lithium salts impact the rates of lithiation and layering, with a much slower process for Li2CO3.

Adoption of dense and homogeneous solid electrolytes can possibly mitigate the propagation of lithium dendrites and enable lithium metal anodes. Application of external pressure helps to minimize the sintering temperature in oxide ceramics and can potentially densify softer sulfide electrolytes even under room temperature conditions. A previously developed phase field-based computational scheme for predicting the high-temperature sintering-induced densification of oxide ceramic solid electrolytes is extended in the present context to capture the influence of external pressure for densifying solid electrolytes. Two different bulk deformation mechanisms, namely, “reorganization” and “creep deformation,” are dominant under external pressure, which is different from the surface and grain-boundary diffusion-induced densification of solid electrolytes that occurs during high temperature sintering. External pressure also increases the points of contact between the particles, which further enhances the propensity of diffusion-induced sintering process. Results obtained from simulations indicate that densification under external pressure is independent of the solid electrolyte particle morphology. Finally, a phase map is generated between applied pressure and temperature for achieving complete densification of oxide ceramics, which can possibly guide the synthesis of thin and dense solid electrolyte separators.

Minimization of bulk and surface free energy acts as the driving force for precipitation of transition metal carbonates. Thermodynamically dominated precipitates form single crystals, and kinetically controlled deposits show spherical morphology.

Heterogenous architectures with elemental gradients tailored within particles have been pursued to combat the instabilities limiting Ni-rich cathode materials for lithium-ion batteries. The growth of different compositional layers is accomplished during the synthesis of hydroxide precursors. However, the extent to which these concentration gradients are modified during high-temperature reactions is difficult to establish in their intact, spherical form. Here, we show the entire three-dimensional structure of a secondary particle can be resolved nondestructively with differential X-ray absorption spectroscopy (XAS) through transmission Xray microscopy (TXM). The relationship between particle location and elemental content was fully quantified, with high statistical significance, for heterostructures possessing different compositional gradients in the precursors with 90:5:5 Ni:Mn:Co core compositions. Reduced elemental heterogeneity was observed after high-temperature synthesis, but gradients remained. The methodology presented should be used to guide synthesis while assuring that gains in electrochemical performance are linked to precise elemental distributions at the nanoscale.

Synthesis of the cathode materials used in lithium ion batteries involve the two steps, coprecipitation and calcination, where in the first step cathode precursors are formed, and later in the second step lithium ions are inserted into these cathode particles through chemical routes. During calcination, the cathode precursors obtained from the coprecipitation is mixed with lithium salt (LiOH or Li 2 CO 3 ) and heated at high temperatures (~ 650°C – 1000°C) where oxidation and lithiation of the cathode particles take place. Calcination is considered to be of major significance in determining the final state of the cathode particles because it not only determines the extent of oxidation and lithiation experienced by the cathodes, but also substantially influences its morphology (for example, primary particle size, internal porosity, etc.). Significant surface modification of the cathode particles is also possible during calcination, which can impact its charge transfer resistance. Before the oxidation and lithiation of the cathode precursors, removal of water or CO 2 is observed. All these chemical changes within the cathode precursors lead to change in its lattice volume, which is reflected as variation in the size of the primary particles. Apart from this, sintering induced change in particle size is also observed during the calcination process. In order to decipher the structural and morphological variations that occur during the calcination of cathode precursors, detailed experimental characterization is conducted in the present context using in situ X-ray diffraction (XRD) and thermogravimetric analysis (TGA) techniques. Atomistic simulations are conducted to decipher the feasibility of different chemical reactions that can possibly occur under elevated temperatures. Impact of reaction rate constant and mass transport in determining the extent of the oxidation and lithiation experienced by the cathode particles is analyzed by using a mesoscale level computational technique. Sintering induced grain growth experienced by the cathode primary particles is also investigated at the mesoscale level, which is demonstrated in Figure 1. Overall, a thorough understanding of the various physicochemical phenomena that occur during the calcination of cathode precursors has been developed using a combination of experimental and computational techniques, which will be discussed in detail. Figure 1

Most research on the electrochemical dynamics in materials for high-energy Li-ion batteries has focused on the global behavior of the electrode. This approach is susceptible to misleading analyses resulting from idiosyncratic kinetic conditions, such as surface impurities inducing an apparent two-phase transformation within LiNi 0.8Co0.15Al0.05O2 . Here, we use nano-focused X-ray probes to measure delithiation operando at the scale of secondary particle agglomerates in layered cathode materials during charge. After an initial latent phase, individual secondary particles undergo rapid, stochastic, and largely uniform delithiation, which is in contrast with the gradual increase in cell potential. This behavior reproduces across several layered oxides. Operando X-ray microdiffraction (µ-XRD) leverages the relationship between Li content and lattice parameter to further reveal that rate acceleration occurs between Li-site fraction (xLi) ~0.9 and ~0.4 for LiNi0.8Co0.15Al0.05O2 . Physics-based modeling shows that, to reproduce the experimental results, the exchange current density (i0) must depend on xLi , and that i0 should increase rapidly over three orders of magnitude at the transition point. The specifics and implications of this jump in i0 are crucial to understanding the charge-storage reaction of Li-ion battery cathodes.

Increasing the capacity of cathode materials used for lithium-ion batteries is desirable, as it ultimately enhances the energy density. Due to their lower cost and reversible cycling capacity of 250 – 300 mAh/g, Li- and Mn-rich LMR-NMC oxides are strong candidates as next generation cathodes used in lithium-ion batteries. Apart from the atomic structure, morphology of the cathode particles also influence their performance. LMR-NMC cathode particles are usually constructed through a two-step cathode fabrication process, which involves initial coprecipitation of the Mn-rich carbonate based cathode precursors, and later calcination of these precursors with a lithium salt at elevated temperatures. The secondary particles generally maintain their as precipitated precursor morphologies even after high temperature calcination. Even though the primary particles do change their size during calcination, the rate of oxidation and lithiation experienced by the transition metal precursors depend substantially on the primary particle morphology. Hence, it is critical to understand and control both the primary and secondary particle morphologies obtained after the coprecipitation process. In the present context, carbonate based NMC cathode precursors containing only Mn, only Ni and only Co, is precipitated, along with equal amount of the transition metals (Ni 0.33 Mn 0.33 Co 0.33 CO 3 ), using conventional batch reactors. NH 4 HCO 3 is used as the source of carbonate anions during the coprecipitation process, and the entire reaction is conducted at 50°C. The obtained particle morphologies for different transition metals are shown in Figure 1(a) as visualized using high resolution TEM techniques. Except MnCO 3 , all other transition metals demonstrate aggregated morphologies, which most probably form through surface growth mechanisms. Competition between growth rate and surface energies that leads to the formation of single crystalline particles for MnCO 3 , and particulate features for other transition metals, are demonstrated in Figure 1(b). Multiscale computational methodologies are developed to elucidate the impact of reaction kinetics and thermodynamics on determining the overall primary and secondary particle morphologies. Influence of transition metal content and ammonia concentration in determining the final particle size and size distribution will be discussed as part of this study. Figure 1

Li-O-2 batteries suffer from large charge overpotentials due to the high charge transfer resistance of Li2O2 discharge products. A potential solution to this problem is the development of LiO2-based batteries that possess low charge overpotentials due to the lower charge transfer resistance of LiO2. In this report, IrLi nanoparticles were synthesized and implemented for the first time as a LiO2 battery cathode material. The IrLi nanoparticle synthesis was achieved by a temperature-and time-optimized thermal reaction between a precise ratio of iridium nanoparticles and lithium metal. Li-O-2 batteries employing the IrLi-rGO cathodes were cycled up to 100 cycles at moderate current densities with sustained low cell charge potentials (< 3.5 V). Various characterization techniques, including SEM, DEMS, TEM, Raman, and titration, were used to demonstrate the LiO2 discharge product and the absence of Li2O2. On the basis of first-principles calculations, it was concluded that the formation of crystalline LiO2 can be stabilized by epitaxial growth on the (111) facets of IrLi nanoparticles present on the cathode surface. These findings demonstrate that, in addition to the previously studied Ir3Li intermetallic, the IrLi intermetallic also provides a means by which LiO2 discharge products can be stabilized and confirms the importance of templating for the formation process.

Nanoscale morphology has a direct impact on the performance of materials for electrochemical energy storage. Despite this importance, little is known about the evolution of primary particle morphology nor its effect on chemical pathways during synthesis. In this study, operando characterization is combined with atomic‐scale and continuum simulations to clarify the relationship between morphology of cathode primary particles and their lithiation during calcination of LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC‐811). This combined approach reveals a key role for surface oxygen adsorption in facilitating the lithiation reaction by promoting metal diffusion and oxidation, and simultaneously providing surface sites for lithium insertion. Furthermore, oxygen surface termination is shown to increase the activation energy for sintering, leading to smaller primary particle sizes at intermediate temperatures. Smaller particles provide both shorter diffusion lengths for lithium incorporation and increased surface site density for lithium insertion. These insights provide a foundation for more tailored syntheses of cathode materials with optimized performance characteristics.

Identifying irreversible phenomena at single particles of battery cathode materials is an important step to understanding degradation pathways upon cycling. LiNi0.33Mn0.33Co0.33O2 (LiNMC(111)) single particles of size 200 x 300 nm were studied before and after cycling using Scanning X-ray Diffraction Microscopy (SXDM) and ptychographic microscopy. With resolutions of 30 and 5 nm, respectively, it was possible to map the (003) reflection and nickel oxidation state changes in single particles at different states of charge. While the compositions measured by the c lattice parameter from SXDM were found to be homogeneous, mapping at higher resolution using ptychography revealed that Ni oxidation states decrease sharply 0-25 nm from the edge, then trail into a steady oxidation state toward the interior of the particle. Within the 30 nm length scale, we conclude that LiNi(0.33)Mn(0.33)Co(0.33)O(2 )single particles are highly structurally reversible.

Ion transport in solid-state cathode materials prescribes a fundamental limit to the rates batteries can operate; therefore, an accurate understanding of ion transport is a critical missing piece to enable new battery technologies, such as magnesium batteries. Based on our conventional understanding of lithium-ion materials, MgCr2O4 is a promising magnesium-ion cathode material given its high capacity, high voltage against an Mg anode, and acceptable computed diffusion barriers. Electrochemical examinations of MgCr2O4, however, reveal significant energetic limitations. Motivated by these disparate observations; herein, we examine long-range ion transport by electrically polarizing dense pellets of MgCr2O4. Our conventional understanding of ion transport in battery cathode materials, e.g., Nernst-Einstein conduction, cannot explain the measured response since it neglects frictional interactions between mobile species and their nonideal free energies. We propose an extended theory that incorporates these interactions and reduces to the Nernst-Einstein conduction under dilute conditions. This theory describes the measured response, and we report the first study of long-range ion transport behavior in MgCr2O4. We conclusively show that the Mg chemical diffusivity is comparable to lithium-ion electrode materials, whereas the total conductivity is rate-limiting. Given these differences, energy storage in MgCr2O4 is limited by particle-scale voltage drops, unlike lithium-ion particles that are limited by concentration gradients. Future materials design efforts should consider the interspecies interactions described in this extended theory, particularly with respect to multivalent-ion systems and their resultant effects on continuum transport properties.

The crystallographic structure and microstructure of solid electrolytes, such as Li7La3Zr2O12 (LLZO), have a profound impact on their reactivity, conductivity, and stability toward dendrites in solid-state batteries. Controlling the material's structure and morphology requires fine control during the synthesis process, where multiple conditions (precursor particle size/distribution, calcination/sintering temperature, ramp rate, etc.) influence performance. This paper describes, for the first time, the operando characterization of the calcination process using synchrotron X-ray diffraction combined with a mesoscale model of grain growth during the calcination and densification of LLZO. The model is then used to guide synthesis conditions to enhance the densification process. The X-ray data reveal significant coarsening of the initial nanophase lanthanum zirconate precursors during conversion to LLZO. The mesoscale model shows that the activation energy for diffusion during calcination is lower than that during sintering, indicating the inherent coupling between the chemical reaction and grain growth processes. Simulations suggest that particles with small and bimodal size distribution experience better densification, as does precise grading (smaller particles near the surface and larger particles at the center) of different-sized particles. The approach described here can be adapted to understand and guide the synthesis of other materials that undergo calcination and sintering (e.g., transition metal oxide cathodes).

Lead acid batteries are often portrayed as a mature technology with limited capacity and room for innovation. In reality, lead batteries have significant room for growth since they only utilize a fraction of their active material and have been engineered for SLI applications that lack a battery management system for controlled charge and discharge. In large part these issues are related to chemical heterogeneity that exists at both the pack level and within the battery electrode microstructure. Unlike a lithium ion battery, lead acid electrodes are typically larger laterally and millimeters thick with significant porosity to allow acid penetration. At the particle level, the growth and dissolution of PbSO4 during discharge from the Pb and PbO2 charge species also leads to significant volume change and swings in local acid concentration within the electrode pores. Recently, we have begun analyzing the spatial variation of charge acceptance in lead acid cells using high energy x-ray diffraction. At energies approaching the lead K-edge (88 keV), x-rays can penetrate through several millimeters of active material. This allows chemical mapping across 2 V cells during formation and cycling and even depth profiling on miniaturized batteries. In situ diffraction provides valuable new information on microstructural changes in phase and crystallite size during these precipitation and growth reactions. Surprisingly, scatter from noncrystalline phases – i.e. the electrolyte – can also be measured by analyzing changes in the broad background underlying the strong Bragg peaks. While the average state of charge (SOC) computed from diffraction species closely matches the electrochemistry, diffraction mapping shows that the charge state and the degree of charge acceptance can vary substantially throughout each electrode. In general, we find strong gradients in SOC and electrolyte concentration that grow from the lead current collector during formation and initial cycling. In larger cells, we also find vertical heterogeneity that develops over repeated cycling. Combined with ongoing electrochemical modeling and innovations in electrode architectures, these results are helping improve utilization and cyclability, developing lead acid into a stronger contender for emerging stationary storage applications.

The hierarchical nature of the cathode in Li-ion batteries can result in phenomena determining electrochemical performance occurring at different length-scales, from individual atoms to the whole electrode. In architectures designed for high density of charge storage, transport limitations can emerge at the microscale that compromise effective utilization and accelerate degradation. These limitations manifest as chemical heterogeneity within the electrode. Micro-focused diffraction mapping using a laboratory X-ray source provides maps with sub-mm resolution of a whole electrode composed of commercial LiMn2O4. Evidence of disparate local utilization both laterally and along the depth of the electrode was obtained, especially at high rates and after multiple charge-discharge cycles. As a model to study the persistence of heterogeneity due to transport limitations, lateral gradients to lithium transport were introduced by cycling against Li anodes of small diameter. The resulting maps revealed the effects of anisotropic electric migration and diffusion to be separated, confirming that diffusion is the primary limitation for long-range kinetics. Tracking of subsequent relaxation revealed that the heterogeneity was metastable despite a strong thermodynamic driving force, maintained by poor lithium transport through the solid electrode matrix. This study enriches our understanding of transport across thick electrode architectures and the imposition of unique frustrated states, away from equilibrium.

In order to improve the energy density and minimize the safety concerns associated with the liquid electrolytes used in the present day lithium ion batteries, solid electrolytes are being actively considered for use in the next generation energy storage devices.[1] Among various ceramic based solid state electrolytes being investigated, Li7La3Zr2O12 (LLZO) with a garnet crystal structure demonstrates very high ionic conductivity and is extremely stable against lithium.[2] Hence, LLZO is being actively considered as the electrolyte for next generation lithium ion batteries. However, due to poor processing of these ceramics, they contain pores and voids.[3] These open spaces within the bulk not only decrease the effective conductivity of the electrolyte, but also provides open pathways for Li dendrites to propagate. Presence of pores within the ceramic structure can be estimated from the final relative density of the solid electrolyte. High temperature sintering induced densification of the LLZO particles are conducted to improve the relative density of the final solid electrolyte, and this process helps to minimize the void space within the structure.[3, 4] Sometime external pressures are applied to further improve the relative densities.[5] Even though several experimental studies have been conducted for constructing the LLZO solid electrolytes, very little effort has been devoted to actually understand the physical mechanisms that play major role during the densification process. In the present context, a computational methodology has been developed at the mesoscale level to understand the impact of surface and grain-boundary diffusion mechanisms on the overall grain ripening and densification experienced by the LLZO solid electrolytes during the sintering process conducted at elevated temperatures. During densification, the extent of increase in relative density depends on the activation energy associated with the diffusive mass transport processes. Here, the activation energy for LLZO will be estimated from direct comparison of relative densities obtained from the developed computational model and experimental observations.[6] Some strategies, in terms of particle sizes and size distributions, that can lead to improved relative densities within the LLZO solid electrolytes, will also be discussed in this presentation. References Zhang, Z., et al., New horizons for inorganic solid state ion conductors. Energy & Environmental Science, 2018. 11(8): p. 1945-1976. Ramakumar, S., et al., Lithium garnets: synthesis, structure, Li+ conductivity, Li+ dynamics and applications.Progress in Materials Science, 2017. 88: p. 325-411. Rangasamy, E., J. Wolfenstine, and J. Sakamoto, The role of Al and Li concentration on the formation of cubic garnet solid electrolyte of nominal composition Li7La3Zr2O12. Solid State Ionics, 2012. 206: p. 28-32. Sharafi, A., et al., Controlling and correlating the effect of grain size with the mechanical and electrochemical properties of Li7La3Zr2O12 solid-state electrolyte. Journal of Materials Chemistry A, 2017. 5(40): p. 21491-21504. Dzepina, B., D. Balint, and D. Dini, A phase field model of pressure-assisted sintering. Journal of the European Ceramic Society, 2019. 39(2-3): p. 173-182. Shin, R.-H., et al., Effect of Li3BO3 additive on densification and ion conductivity of garnet-type Li7La3Zr2O12 solid electrolytes of all-solid-state lithium-ion batteries. Journal of the Korean Ceramic Society, 2016. 53(6). Figure 1