Lithium- and manganese-rich layered oxides (LMR) stand out as next-generation lithium-ion cathode chemistries, which harness both transition-metal and lattice-oxygen redox processes to deliver exceptional capacity and energy density. However, their full potential is hindered by intrinsic oxygen instability and structural degradation, resulting in pronounced voltage fade and capacity decay. Here, we present a complex-concentrated anion-doping paradigm in which multiple anions, F, Br, and S, are incorporated into the oxygen sublattice to enhance oxygen-redox and structural stability. X-ray absorption spectroscopy and aberration-corrected scanning transmission electron microscopy confirm ultra-stable local oxygen coordination environments during long-term cycling, with detrimental phase transformations and oxygen-loss-induced cavitation dramatically inhibited. Notably, we show that the characteristic LiTM6 transition metal (TM) honeycomb ordering is preserved even after electrochemical cycling. Concurrently, this strategy yields an unprecedented volume change of only 0.63% upon charging to 4.8 V vs. Li+/Li, achieving the first zero-strain LMR cathode. The resulting LMR cathode delivers ultralow voltage fade (1 mV per cycle during the first 100 cycles and becomes negligible in subsequent cycles) and outstanding energy retention (93% after 200 cycles) in a pouch cell configuration. Our complex-concentrated anion-doping concept establishes a broadly applicable strategy for resolving chemo-mechanical failure mechanisms in ceramic intercalation electrodes for next-generation energy storage.

Silicon-containing lithium-ion batteries can exhibit capacity gain early in life, which makes forecasting future cell behavior difficult. We have observed these anomalous trends even in conditions where known mechanisms, such as overhang equalization and excessive electrolyte oxidation, are unlikely to be significant. Here, we combine simulations and experiments to analyze four cases that can produce increased capacity in Si cells. Three of these pathways relate to break-in processes, where improved mass and charge transport can lead to increased access to active electrode domains and decreased cell impedance. The fourth case occurs at high levels of prelithiation, when the positive electrode (PE) is completely replenished with Li+ at the end of cell discharge. We show that the commonality among these mechanisms is that the underlying transformations change the potentials experienced by electrodes at the end of half-cycles, increasing the Li+ inventory available to the cell. A quantitative framework to describe these effects is presented, enabling these ideas to be extended to other battery systems.

Manganese-rich oxides are attractive options as next-generation, earth-abundant cathodes and significant efforts are being directed toward commercial implementation. We report here an updated techno-economic analysis of the lithium- and manganese-rich (LMR) class of earth-abundant cathodes for electric vehicle applications. BatPaC modeling was used to define the cell-level metrics that must be met for these materials to be cost and energy competitive with the current commercial earth-abundant benchmark, LiFePO4, as well as anticipated variations such as LiMn0.8Fe0.2PO4. The model was used to evaluate a high-performance material from the literature and subsequently define R&D targets as the likely limits of practical performance for similar LMR systems. Experimental validation and BatPaC evaluation of an advanced, cobalt-free LMR cell system was also conducted. Results show that the advanced LMR cells come within similar to 5% of the defined limits and exceed the energy of LiFe(Mn)PO4 cells at a similar cost. Excellent cycle-life, low impedance, and low impedance rise were also achieved under the conditions tested and reveal that cobalt is not necessary to achieve high-performance LMR oxides. Although the analysis conducted herein reports on LMR cell systems, the methodology and target values defined for performance metrics easily extend to the evaluation of other systems under consideration as earth-abundant options.

Electrodes containing SiOx/graphite (Gr) materials are attractive as anodes for high-energy lithium-ion batteries. However, their mechanical deformation, electrochemical response, and impedance evolution during long-term cycling are strongly coupled, complicating accurate diagnosis of performance fade mechanisms. In this work, the behavior of electrochemically prelithiated SiOx/Gr anodes paired with NMC811 cathodes is systematically investigated using techniques that include in-situ dilatometry, three-electrode electrochemistry, and multiscale post-cycling microscopy. The SiOx/Gr electrode exhibits a maximum expansion of 49% upon lithiation to 10 mV vs Li+/Li, with 84% of the expansion and 91% of the capacity being reversible. In full cells, relatively stable cycling with only 12% capacity fade over 500 cycles is observed. Three-electrode experiments reveal cell-level impedance growth, which is dominated by the NMC811 cathode: the SiOx/Gr anode exhibits minimal net impedance rise and an initial impedance decrease at low potentials. Despite this apparent electrochemical stability, cross-sectional SEM, PFIB tomography, and cryo-STEM reveal irreversible anode thickening caused by the accumulation of an inorganic-rich solid electrolyte interphase (SEI) permeating the anode bulk. Electrode potential-shift analysis further demonstrates that Li+ ions released from lithium reservoirs in the prelithiated anode mask true lithium inventory loss during aging. These results demonstrate that low-expansion SiOx/Gr anodes can simultaneously exhibit favorable cycling and impedance metrics while undergoing substantial, hidden degradation, underscoring the importance of electrode-resolved diagnostics for evaluating prelithiated silicon-based anodes.

Here, we advance electrode-omics to identify evolutionary bursts by which ethereal mixed-salt locally superconcentrated electrolytes (LSCE) containing lithium bis(fluorosulfonyl)imide (LiFSI) and LiClO4 mitigate silicon anode degradation through its epochs of electrochemical and chemical reactions.

The substrate and reaction atmosphere govern impurity incorporation and defect formation during hard-carbon synthesis, thereby strongly influencing its electrochemical Na-storage performance.

Silicon (Si) is a promising lithium-ion battery anode material due to its high specific capacity but suffers from poor calendar lifetime. The mechanisms behind Si anode’s poor calendar lifetime are dictated by the interactions between the solid electrolyte interphase (SEI) and the electrolyte; however, the roles of electrolyte constituents in aging performance are not well understood. In this study, we evaluate the electrolyte formulation-dependent Si calendar lifetime with a multi-component approach on 20 electrolyte formulations with varying lithium hexafluorophosphate (LiPF 6 ), ethyl methyl carbonate (EMC), and vinylene carbonate (VC) mole fractions alongside a voltage-hold calendar aging protocol. From the voltage-hold protocol, the LiPF 6 content does not play a role in the calendar aging performance. In contrast, increasing and decreasing the EMC and VC mole fractions drastically lowers the Si aging performance by up to 98% when compared to the baseline composition (0.1:0.72:0.17 LiPF 6 :EMC:VC (mol:mol)). These aging results align with molecular dynamics simulation-derived EMC coordination numbers (N EMC ) such that electrolyte compositions with N EMC greater than 3.4 lead to the 98% drop in aging performance. This implies the formulation-dependent solvation structure dictates the SEI-electrolyte interactions that occur during aging and accelerates the aging degradation of Si-based anodes. In summary, we connect the silicon surface passivity to the electrolyte coordination structure to reveal a complex link between calendar aging and electrolyte components. This research was supported by U.S. Department of Energy, Vehicle Technologies Office (DOE-VTO) under the Silicon Consortium Project, directed by Nicolas Eidson, Carine Steinway, Thomas Do, and Brian Cunningham, and managed by Anthony Burrell. This manuscript has been authored in part by UT-Battelle, LLC, under contract DE-AC05–00OR22725 with the US Department of Energy (DOE). The publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doepublic-accessplan). Argonne National Laboratory (“Argonne”) is operated by UChicago Argonne LLC, and is a U.S. Department of Energy Office of Science laboratory, operated under Contract No. DE-AC02 – 06CH11357. National Laboratory of the Rockies, operated by Alliance for Sustainable Energy, LLC, for the U. S. Department of Energy (DOE) under Contract No. DE-AC36- 08GO28308.

Adoption of Behind-the-Meter Storage (BTMS) requires design of batteries that enable high safety, long cycle life, and low cost at the system level. Pairing Li4Ti5O12 (LTO) with LiMn2O4 (LMO) achieves targets related to safety and cycle life, but these materials' low energy densities contribute to higher cost at the system scale. Increasing electrode loading is a simple approach to improve energy density, but comes with a trade-off in electrode utilization due to long, tortuous Li+ diffusion pathways. Here, laser ablation is used to microstructure (pattern) high-loading electrodes to enhance electrode performance through improved Li+ diffusion pathways. Four cell types, comprising combinations of standard or patterned anode and cathode, were prepared to evaluate the effects of laser ablation at each electrode. A rate test shows that patterning electrodes enhances active material utilization at greater than or similar to 1C rates. Patterning the cathode yields the most benefit, as cells with a patterned cathode demonstrate a similar to 20% higher accessible capacity than those without at 1.4C. Additionally, 1C capacity retention of cells with patterned cathode (91% through 3000 cycles) is significantly improved over cells with only the anode patterned (64%) and non-patterned electrodes (50%). Characterization of post-mortem cells before and after refreshing their electrolyte suggests that 1C capacity retention is improved by mitigation of electrode "dry-out". We hypothesize that the microstructure acts as a reservoir of additional electrolyte, or a path for gas to escape, so that active material remains wetted throughout long-term cycling, and/or the microstructure may reduce localized, gas-forming overpotentials in the high-loading electrode.

As the global need for energy increases, it is crucial to optimize the energy density and cost effectiveness of lithium-ion batteries (LIBs). Lithium manganese iron phosphate (LMFP) is a promising material for next-generation LIBs because it shares the stability of lithium iron phosphate (LFP) but has a higher energy density. LMFP has an olivine-type crystal structure, similar to lithium iron phosphate (LFP). However, the inclusion of Mn sites increases the energy density of the material, as the Mn 3+ /Mn 2+ transition occurs at a higher redox potential than the Fe 3+ /Fe 2+ transition at ~4.1 and ~3.4 V vs. Li + /Li respectively. Additionally, the two-plateau shape of the LMFP voltage profile assists in state-of-charge (SoC) estimation compared to the flat profile of LFP, a crucial capability for electric vehicle battery systems. In this work, we investigated the voltage-dependent impedance characteristics of LiMn 0.6 Fe 0.4 PO 4 ||Li 4 Ti 5 O 12 cells with a Li-metal reference electrode. Charge and discharge current pulses were applied to the cell, and the resulting voltage changes tracked to determine electrode and cell impedance across the voltage profile ( Figure 1 ). We observed that the LMFP cathode is the main contributor to cell impedance, which rises sharply during transitions between the Fe redox and Mn redox plateaus. In our presentation we will describe the effect of temperature on cell and electrode impedances. In addition, we will show data from long-term aging experiments conducted on LiMn 0.6 Fe 0.4 PO 4 ||Li 4 Ti 5 O 12 cells. Figure 1. Voltage profiles of LMFP cathode (red), LTO anode (black), and full cell (blue), with superimposed current pulses used to measure impedance. Figure 1

The volumetric changes of silicon electrodes, along with the strong adhesive properties of certain binders, can lead to plastic deformation of the current collector and create damage in the electrode coating. Here, we report a detailed study of silicon coatings on a high-tensile alloy (HTA) foil of copper with strength over twice that of conventional copper foils. The HTA current collectors with high mechanical strength can mitigate plastic deformation upon continuous cycling. At moderate areal capacities (2.5-3 mAh cm-2), conventional copper foils show significant wrinkling after only a few electrochemical cycles, whereas the HTA foils remain intact. We demonstrate viability of the HTA foils in large format xx6395 pouch cells, in which the HTA current collectors remain intact even at an areal capacity of 4.5 mAh cm-2; in contrast, wrinkles form in conventional copper current collectors increasing the likelihood of lithium plating. Computational studies show that stresses generated during cycling of silicon electrodes are very high in the current collector and at the current collector-coating interface, explaining the wrinkling of conventional Cu foils. Our studies highlight importance of current collector to solve the electrochemical and chemo-mechanical performance challenges associated with high-loading silicon electrodes.

Behind-the-Meter Storage (BTMS) systems require dedicated development of battery materials that target long cycle life and low cost at the system level. Pairing Li4Ti5O12 (LTO) and LiNi0.9Mn0.05Co0.05O2 (NMC90-5-5) shows promise to achieve targets for BTMS applications; however, minimal literature is available that discusses electrolyte solvent selection for this pairing. This study explores the role of electrolyte solvent on cycle life in LTO/NMC90-5-5 batteries. Four model electrolytes are evaluated; the baseline, Gen2, is compared with 1M LiPF6 added to each of three separate solvents: ethylene carbonate (EC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC). An additional consideration is that NMC90-5-5 undergoes an H2 -> H3 phase transition that allows for a significant increase to capacity; however, it's unclear how this phase transition impacts electrolyte stability and cycle life. Therefore, the phase transition is avoided or accessed by cycling to 2.6V or 2.7V, respectively. The cells with Gen2, cycled to 2.6V, show the highest capacity retention due to EC passivating the LTO, EMC improving stability at the NMC90-5-5, and avoiding increased degradation from the 2.7V protocol. Despite having high initial reactivity that causes Li-depletion, FEC was the only solvent to avoid increased degradation when moving to the higher termination voltage.

The technology of silicon anodes appears to be reaching maturity, with high-energy Si cells already in pilot-scale production. However, the performance of these systems can be difficult to replicate in academic settings, making it challenging to translate research findings into solutions that can be implemented by the battery industry. Part of this difficulty arises from the lack of access to engineered Si particles and anodes, as electrode formulations and the materials themselves have become valuable intellectual property for emerging companies. Here, we summarize the efforts by Argonne’s Cell Analysis, Modeling, and Prototyping (CAMP) Facility in developing Si-based prototypes made entirely from commercially available materials. We describe the many challenges we encountered when testing high-loading electrodes (>5 mAh cm −2 ) and discuss strategies to mitigate them. With the right electrode and electrolyte design, we show that our pouch cells containing ≥ 70 wt% SiO x can achieve 600–1,000 cycles at C/3 and meet projected energy targets of 700 Wh L −1 and 350 Wh kg −1 . These results provide a practical reference for research teams seeking to advance silicon-anode development using accessible materials.

Sodium-ion batteries (SIBs) containing layered oxides (such as NaNi x Fe y Mn z O 2 or NFM) have emerged as a promising alternative to lithium-ion batteries (LIBs). Although layered oxide cathodes include advantages such as high theoretical capacity and relative ease of synthesis, phase transitions and stress-induced mechanical degradation pose challenges toward improved electrochemical performance. The mechanical durability becomes especially crucial during cycling at high voltages to make SIB cells cost-competitive with LIB cells. Understanding and measuring the stresses generated during the (de)intercalation of sodium ions from (into) the oxide structure is critical for improving the mechanical durability and electrochemical performance of SIB cells with metal oxide cathodes. Although several methods have been used to monitor structural and oxidation-state changes in layered oxides, few techniques are available for measuring stresses during electrochemical cycling. The substrate-curvature method is one such technique that has been employed to determine diffusion-induced stresses in SIB and LIB electrodes during electrochemical cycling. From that perspective, this study focused on the real-time stress measurements on commercially relevant high-capacity NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NFM111) electrodes during electrochemical cycling using an optical-based substrate-curvature method. Preliminary measurements showed a complex stress profile during the cycling, and the peak compressive and tensile stresses experienced by the electrode in the 2.0 – 4.1 V range were found to be – 4 MPa and 2.7MPa, respectively. The correlation between the stress patterns with the complex structural transformation and volume changes of the material will be discussed in detail. Data obtained from these experiments are intended to enable design strategies for mechanically durable NFM-based cathodes and improve the cycle life of high-performance cells being developed for transportation and large-scale energy storage applications. Figure 1

LiNi 0.5 Mn 1.5 O 4 (LNMO) is a high‐voltage spinel cathode with low nickel content, making it an attractive candidate for next‐generation lithium‐ion batteries (LIBs). However, its application is limited by interfacial instability with conventional carbonate‐based electrolytes at high voltages. In this work, a localized saturated electrolyte (LSE) capable of stably operating up to 4.85 V is investigated. Molecular dynamics simulations and Fourier transform infrared spectroscopy reveal that adding “non‐solvating” 1,1,2,2‐tetrafluoroethyl‐2,2,3,3‐tetrafluoropropyl ether diluent in the saturated electrolyte, more PF 6 − anions are present in the first solvation shell of Li + , at the expense of solvent molecules. This tailored solvation environment promotes the formation of a robust, LiF‐rich cathode‐electrolyte interphase that mitigates transition metal dissolution and parasitic side reactions. The optimized LSE enables excellent cycling performance, with 95% capacity retention in Li|LNMO half‐cells after 100 cycles and 94% retention in Li 4 Ti 5 O 12 |LNMO full cells after 250 cycles, even at a practically relevant LNMO cathode loading of ≈15 mg cm −2 . These results highlight the benefits of electrolyte engineering and solvation structure control in advancing high‐voltage LIB technologies.

This work presents a computational screening approach to identify Li-rich transition-metal oxide sacrificial cathode additives and provides experimental validation of antifluorite-structured Li6MnO4 as a potential candidate. Initial attempts to synthesize this compound result in low purity (<= 40% by weight) owing to close thermodynamic competition with Li2O and MnO at low temperature. However, it is shown that a much higher purity of 85% by weight can be achieved by combining Li excess with rapid cooling from high temperature, which effectively stabilizes the Li6MnO4 phase. The synthesized product delivers a high irreversible Li release capacity that exceeds 700 mAh g(-1) by utilizing combined Mn oxidation (Mn2+/3+ and Mn3+/4+) and O oxidation. These results demonstrate that Li6MnO4 may therefore be useful as a potential sacrificial cathode additive in Li-ion batteries and motivate further investigation of other structurally-related compounds. While attempts were made to synthesize two additional compounds among computationally screened candidates, it was not successful to experimentally realize the two candidates. The difficulty of experimental realization of the newly predicted materials remains a challenge and it is suggested that more efforts need to be devoted to developing computational techniques to precisely predict synthesizability and propose potential synthetic routes of the predicted materials.

The United States houses several well-funded companies devoted to developing materials and high-energy Li-ion cells based on silicon. Many of these enterprises have invested in pilot plants in recent years, suggesting that these technologies may soon enter the market. Despite the historical struggles with the volume change of Si-based materials, multiple cell developers have now been able to demonstrate fast charging capability and extended cycle life in 2-12 Ah prototypes. While Si anodes have reached a certain level of maturity, academic research remains extremely valuable in helping diagnose and mitigate the calendar aging issues that continue to plague these technologies. 1 Inspection of the literature suggests that most research groups do not have access to high-performing electrodes and cells, which may limit the impact and transferability of their work to the challenges faced by manufacturers. Argonne National Laboratory’s Cell Analysis, Prototyping and Modeling Facility (CAMP) has over a decade of experience in working with Si anodes. This extensive expertise, built through numerous iterations of manufacturing and characterization, has enabled us to reliably develop high-energy silicon cells using commercially available materials. We have successfully demonstrated > 2 Ah pouch cells that achieve 1,000 cycles of life at a specific energy of > 340 Wh/kg (when scaled to automotive-relevant dimensions). In this presentation, we will discuss the solutions we developed to address various challenges, including strategies to mitigate mechanical issues and the critical role of inactive electrode components. Figure 1. Cycle life of a 2.3 Ah pouch cell containing a high-loading SiO x anode. Modeling from BatPaC indicated that building a 70 Ah automotive cell with these same electrodes would result in cell-level specific energy > 340 Wh/kg. References 1 McBrayer J. D. et al., Nature Energy 6, 866 (2021). Acknowledgments: This research was supported by the U.S. Department of Energy’s Vehicle Technologies Office under the Silicon Consortium Project, directed by Brian Cunningham, Thomas Do, Nicolas Eidson and Carine Steinway, and managed by Anthony Burrell. Figure 1

The novelty of this study includes correlating stress with the complex structural transformation and volume changes in sodium-ion battery cathodes.

Advanced battery characterization using in situ/operando neutron imaging is critical for uncovering degradation modes such as lithium (Li) plating in Li-ion batteries (LIBs). However, conventional LIBs hinder operando neutron radiography (NR) and in situ neutron micro-computed tomography (N-mu CT) for visualizing Li plating near the graphite-separator interface due to strong attenuation from hydrogen-rich components like PP-PE-PP separators, electrolyte, and Fe-based spacers. In this work, we designed and tested a neutron-friendly battery (NFB) optimized for in situ Li detection during extreme fast charging (XFC). Guided by neutron attenuation cross-sections and material transmission, the NFB enables clear visualization at the graphite-separator interface, which is typically opaque in standard LIBs. Electrochemical tests show the NFB exhibits voltage/current responses like standard cells for up to 50 XFC cycles. However, its lower reversibility and capacity are likely due to Cu-coated Al spacer degradation from delamination or corrosion. We propose titanium spacers as a more stable alternative, albeit requiring custom machining. Using this optimized cell, we achieved simultaneous neutron tomography of multiple cells, capturing in situ 3D images of dead Li accumulation, particularly near graphite edges. These heterogeneous deposits and disconnected Li clusters suggest localized current density hotspots during XFC.

Extreme fast charging (XFC) of commercial lithium-ion batteries (LIBs) in ≤10-15 minutes will significantly advance the deployment of electric vehicles globally. However, XFC leads to considerable capacity fade, mainly due to graphite anode degradation. Non-destructive three-dimensional (3D) investigation of XFC-cycled anodes is crucial to connect degradation with capacity loss. Here, we demonstrate the viability of simultaneous neutron and X-ray tomography (NeXT) for ex-situ 3D visualization of graphite anode degradation. NeXT is advantageous because of the sensitivity of neutrons to Li and H and X-rays to Cu. We combine the neutron and X-ray tomography with micron resolution for material identification and segmentation on one pristine and one XFC-cycled graphite anode, thereby underscoring the benefits of the simultaneous nature of NeXT. Our ex-situ results pave the way for the design of NeXT-friendly LIB geometries that will allow operando and/or in-situ 3D visualization of graphite anode degradation during XFC.