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At least 1,711 records · Page 95
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DOE OSTI2025

Tailoring the Reaction Heterogeneity for Robust Li‐Rich Cathodes

The practical application of Li-rich Mn-based layered oxides (LLO) cathode is hindered by severe capacity and voltage degradation resulting from severe oxygen release and irreversible phase transition. In this work, the reaction heterogeneity, which describes the spatially resolved electrochemical divergence within individual cathode particles, is engineered through compositional gradient design to couple Li + transport kinetics and the anion redox activity between particle interiors and surfaces. It is revealed that Co/Mn concentration gradient within particles creates heterogeneous phase content distribution and structural ordering, inducing surface-bulk reaction heterogeneity that significantly impacts the overall electrochemical performance. Specifically, Li 2 MnO 3 -poor and Co-enriched surface effectively mitigates the oxygen loss and enhances electrochemical reaction kinetics, benefited from the reduced surface redox reactivity and induced highly ordered intra-layered cationic arrangement. Meanwhile, the Li 2 MnO 3 -enriched core with slight Li/Ni intermixing provides high reversible capacity and strong mechanical stability. Consequently, the greatly enhanced anion redox reversibility, Li + diffusion dynamics, and structure stability endow LLO with exceptional electrochemical properties, showing a capacity retention of 86.0% and a reduced voltage decay of 0.518 mV per cycle after 500 cycles at 1 C. This work provides a valuable strategy to tailor the redox chemistry and achieve robust LLO.

25 ENERGY STORAGE↗
DOE OSTI2023

Sodium Rich Vanadium Oxy‐Fluorophosphate – Na 3.2 Ni 0.2 V 1.8 (PO 4 ) 2 F 2 O – as Advanced Cathode for Sodium Ion Batteries

Abstract Conventional sodium‐based layered oxide cathodes are extremely air sensitive and possess poor electrochemical performance along with safety concerns when operating at high voltage. The polyanion phosphate, Na 3 V 2 (PO 4 ) 3 stands out as an excellent candidate due to its high nominal voltage, ambient air stability, and long cycle life. The caveat is that Na 3 V 2 (PO 4 ) 3 can only exhibit reversible capacities in the range of 100 mAh g −1 , 20% below its theoretical capacity. Here, the synthesis and characterizations are reported for the first time of the sodium‐rich vanadium oxyfluorophosphate, Na 3.2 Ni 0.2 V 1.8 (PO 4 ) 2 F 2 O, a tailored derivative compound of Na 3 V 2 (PO 4 ) 3 , with extensive electrochemical and structural analyses. Na 3.2 Ni 0.2 V 1.8 (PO 4 ) 2 F 2 O delivers an initial reversible capacity of 117 mAh g −1 between 2.5 and 4.5 V under the 1C rate at room temperature, with 85% capacity retention after 900 cycles. The cycling stability is further improved when the material is cycled at 50 °C within 2.8–4.3 V for 100 cycles. When paired with a presodiated hard carbon, Na 3.2 Ni 0.2 V 1.8 (PO 4 ) 2 F 2 O cycled with a capacity retention of 85% after 500 cycles. Cosubstitution of the transition metal and fluorine in Na 3.2 Ni 0.2 V 1.8 (PO 4 ) 2 F 2 O as well as the sodium‐rich structure are the major factors behind the improvement of specific capacity and cycling stability, which paves the way for this cathode in sodium‐ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2016

A Honeycomb-Layered Oxide Cathode for Sodium-Ion Batteries with Suppressed P3-O1 Phase Transition

Mg–substituted Na 3 Ni 2–x Mg x SbO 6 cathode materials are synthesized via a scalable high–temperature solid–state method to improve the cyclability of the honeycomb–layered oxide cathode in sodium–ion batteries. Here, the partial substitution of Ni 2+ by Mg 2+ in the transition–metal layer suppresses the electrochemically unfavorable P3–O1 transition and enlarges the lattice parameters to bring improved performance with respect to capacity retention, Coulombic efficiency, and Na (de)intercalation kinetics.

25 ENERGY STORAGE↗
DOE OSTI2018

A Lithium-Sulfur Cell Based on Reversible Lithium Deposition from a Li 2 S Cathode Host onto a Hostless-Anode Substrate

Here, the development of lithium–sulfur batteries necessitates a thorough understanding of the lithium-deposition process. A novel full-cell configuration comprising an Li 2 S cathode and a bare copper foil on the anode side is presented here. The absence of excess lithium allows for the realization of a truly lithium-limited Li–S battery, which operates by reversible plating and stripping of lithium on the hostless-anode substrate (copper foil). Its performance is closely tied to the efficiency of lithium deposition, generating valuable insights on the role and dynamic behavior of lithium anode. The Li 2 S full cell shows reasonable capacity retention with a Coulombic efficiency of 96% over 100 cycles, which is a tremendous improvement over that of a similar lithium-plating-based full cell with LiFePO 4 cathodes. The exceptional robustness of the Li 2 S system is attributed to an intrinsic stabilization of the lithium-deposition process, which is mediated by polysulfide intermediates that form protective Li 2 S and Li 2 S 2 regions on the deposited lithium. Combined with the large improvements in energy density and safety by the elimination of a metallic lithium anode, the stability and electrochemical performance of the lithium-plating-based Li 2 S full cell establish it as an important trajectory for Li–S battery research, focusing on practical realization of reversible lithium anodes.

25 ENERGY STORAGE↗
DOE OSTI2018

Theoretical Investigation of 2D Conductive Microporous Coordination Polymers as Li-S Battery Cathode with Ultrahigh Energy Density

Even though tremendous achievement has been made experimentally in the performance of lithium–sulfur (Li–S) battery, theoretical studies in this area are lagging behind due to the complexity of the Li–S systems and the effects of solvent. Because of this, a new methodology is developed for investigating the 2D hexaaminobenzene-based coordination polymers (2D-HAB-CPs) as cathode candidate materials for Li–S batteries via density functional theory calculations in combination with an in-house developed charge polarized solvent model and a genetic algorithm structure global search code. With high ratios of transition metal atoms and two-coordinated nitrogen atoms, excellent electric conductivity, and structural porosity, the 2D-HAB-CP is able to address all of the three main challenges facing Li–S batteries: confining the lithium polysulfides from dissolution, facilitating the electron conductivity and buffering the volumetric expansion during the lithiation process. In addition, the theoretical energy density of this system is as high as 1395 Wh kg -1 . These results demonstrate that the 2D-HAB-CP is a promising cathode material for Li–S batteries. The proposed computational framework not only opens a new avenue for understanding the key role played by solution and liquid electrolytes in Li–S batteries, but also can be generally applied to other processes with liquids involved.

25 ENERGY STORAGE↗
DOE OSTI2018

Improved Cycling Performance of Li-Excess Cation-Disordered Cathode Materials upon Fluorine Substitution

We report the recent discovery of Li-excess cation-disordered rock salt cathodes has greatly enlarged the design space of Li-ion cathode materials. Evidence of facile lattice fluorine substitution for oxygen has further provided an important strategy to enhance the cycling performance of this class of materials. Here, a group of Mn 3+ –Nb 5+ -based cation-disordered oxyfluorides, Li 1.2 Mn 3+ 0.6+0.5x Nb 5+ 0.2-0.5x O 2-x F x (x = 0, 0.05, 0.1, 0.15, 0.2) is investigated and it is found that fluorination improves capacity retention in a very significant way. Combining spectroscopic methods and ab initio calculations, it is demonstrated that the increased transition-metal redox (Mn 3+ /Mn 4+ ) capacity that can be accommodated upon fluorination reduces reliance on oxygen redox and leads to less oxygen loss, as evidenced by differential electrochemical mass spectroscopy measurements. Furthermore, it is found that fluorine substitution also decreases the Mn 3+ -induced Jahn–Teller distortion, leading to an orbital rearrangement that further increases the contribution of Mn-redox capacity to the overall capacity.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Significantly Improved Cyclability of Conversion-Type Transition Metal Oxyfluoride Cathodes by Homologous Passivation Layer Reconstruction

Electrode stabilization by surface passivation has been explored as the most crucial step to develop long-cycle lithium-ion batteries (LIBs). In this work, functionally graded materials consisting of “conversion-type” iron-doped nickel oxyfluoride (NiFeOF) cathode covered with a homologous passivation layer (HPL) are rationally designed for long-cycle LIBs. The compact and fluorine-rich HPL plays dual roles in suppressing the volume change of NiFeOF porous cathode and minimizing the dissolution of transition metals during LIBs cycling by forming a structure/composition gradient. The structure and composition of HPL reconstructs during lithiation/delithiation, buffering the volume change and trapping the dissolved transition metals. As a result, a high capacity of 175 mAh g -1 (equal to an outstanding volumetric capacity of 936 Ah L -1 ) with a greatly reduced capacity decay rate of 0.012% per cycle for 1000 cycles is achieved, which is superior to the NiFeOF porous film without HPL and commercially available NiF 2 -FeF 3 powders. Finally, the proposed chemical and structure reconstruction mechanism of HPL opens a new avenue for the novel materials development for long-cycle LIBs.

25 ENERGY STORAGE↗
DOE OSTI2020

A Fluorination Method for Improving Cation-Disordered Rocksalt Cathode Performance

In Li-rich cation-disordered rocksalt oxide cathodes (DRX), partial fluorine substitution in the oxygen anion sublattice can increase the capacity contribution from transition-metal (TM) redox while reducing that from the less reversible oxygen redox. To date, limited fluorination substitution has been achieved by introducing LiF precursor during the solid-state synthesis. To take full advantage of the fluorination effect, however, a higher F content is desired. In the present study, the successful use of a fluorinated polymeric precursor is reported to increase the F solubility in DRX and the incorporation of F content up to 10–12.5 at% into the rocksalt lattice of a model Li-Mn-Nb-O (LMNO) system, largely exceeding the 7.5 at% limit achieved with LiF synthesis. Higher F content in the fluorinated-DRX (F-DRX) significantly improves electrochemical performance, with a reversible discharge capacity of ≈255 mAh g –1 achieved at 10 at% of F substitution. After 30 cycles, up to a 40% increase in capacity retention is achieved through the fluorination. Overall, the study demonstrates the feasibility of using a new and effective fluorination process to synthesize advanced DRX cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2021

Utilizing Oxygen Redox in Layered Cathode Materials from Multiscale Perspective

We report in high-capacity layered oxide cathode materials, utilization of lattice oxygen as a redox center is considered to be one of the most promising approaches to overcome the capacity limitation set by conventional transition metal redox centers. However, rapid material degradation is often associated with oxygen oxidation, leading to formidable challenges in utilizing oxygen redox. Further mechanistic understanding of the oxygen activities thus becomes critical to better control oxygen redox reactions. This review summarizes recent advances for investigating oxygen redox reactions in cathode materials from a multiscale perspective, i.e., from the atomistic level to the microstructure regime. First the mechanistic aspects of oxygen redox and the consequences of this reaction on various electrode degradation pathways during battery operation (e.g., oxygen loss, transition metal migration, irreversible phase transition), relating structural changes at the crystallographic scale to those at the macro scale, are discussed. Then recent developments based on atomic and microstructure modifications that are promising for improving the reversibility of oxygen redox reaction or mitigating the harmful processes arising from oxidation of the oxygen centers under high operating voltage are recounted. The analysis is concluded with a commentary on further research directions toward optimizing the oxygen activity for high-capacity charge storage.

25 ENERGY STORAGE↗
DOE OSTI2022

The Importance of Surface Oxygen for Lithiation and Morphology Evolution during Calcination of High-Nickel NMC Cathodes

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 work, 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.

25 ENERGY STORAGE↗
DOE OSTI2022

A Comprehensive Understanding of the Aging Effects of Extreme Fast Charging on High Ni NMC Cathode

As the battery industry shifts toward high Ni content cathodes, such as LiNi 0.8 Mn 0.1 Co 0.1 O 2 [NMC811], a complete understanding of the degradation mechanisms of NMC811 under extreme fast charging (XFC) (XFC, ≤10–15 min charging) conditions is needed. Such comprehensive understanding would identify the most critical materials gaps that need to be addressed for enabling XFC long-life cells for electric vehicles. This study maps out the key aging mechanisms for NMC811 cycled at different XFC conditions (between 1C and 9C) for up to 1000 cycles. To acquire a fundamental understanding of utilization and degradation, cells are evaluated using a range of electrochemical techniques, and multimodal and multiscale microscopy techniques to quantify chemical, structural, and crystallographic degradation as a function of cycling conditions for the NMC cathode. When comparing NMC811 to NMC532, it is observed that NMC811 has a greater subsurface crystallographic degradation and displays a similar magnitude of subparticle cracking. However, the NMC811 maintains superior performance despite those advanced degradations. Here, the superior cycle life performance is attributed to the NMC811 particles having radially oriented grains and improved transport properties. NMC811 shows between 4.6× and 3.15× reduction in capacity fade than NMC532 for charging rates between 4C (e.g., 15-min charging) and 6C (10-min charging).

25 ENERGY STORAGE↗
DOE OSTI2022

Optimizing Li‐Excess Cation‐Disordered Rocksalt Cathode Design Through Partial Li Deficiency

Li-excess disordered rocksalts (DRXs) are emerging as promising cathode materials for Li-ion batteries due to their ability to use earth-abundant transition metals. In this work, a new strategy based on partial Li deficiency engineering is introduced to optimize the overall electrochemical performance of DRX cathodes. Specifically, by using Mn-based DRX as a proof-of-concept, it is demonstrated that the introduction of cation vacancies during synthesis (e.g., Li 1.3-x Mn 2+ 0.4-x Mn 3+ x Nb 0.3 O 1.6 F 0.4 , x = 0, 0.2, and 0.4) improves both the discharge capacity and rate performance due to the more favored short-range order in the presence of Mn3+. Density functional theory calculations and Monte Carlo simulations, in combination with spectroscopic tools, reveal that introducing 10% vacancies (Li 1.1 Mn 2+ 0.2 Mn 3+ 0.2 Nb 0.3 O 1.6 F 0.4 ) enables both Mn 2+ /Mn 3+ redox and excellent Li percolation. However, a more aggressive vacancy doping (e.g., 20% vacancies in Li 0.9 Mn 3+ 0.4 Nb 0.3 O 1.6 F 0.4 ) impairs performance because it induces phase separation between an Mn-rich and a Li-rich phase.

25 ENERGY STORAGE↗
DOE OSTI2023

Cation Disordered Anti-Perovskite Cathode Materials with Enhanced Lithium Diffusion and Suppressed Phase Transition

Recently, a new family of anti-perovskite Li 2 TMSO was discovered as promising cathode materials for Li-ion batteries (LIBs) with superiorities in high specific capacity, low cost, and environmental friendliness. However, the applications of these anti-perovskite materials meet severe challenges in the cyclability and rate performance. In this work, a cation-disordered anti-perovskite type solid solution Li 2 Fe 1– x Mn x SO (LFMSO, x = 0, 0.2, 0.5) with excellent electrochemical performance is reported. On the basis of comprehensive structural characterizations, the role of the cation disordering in LFMSO is clarified. In comparison with Li 2 FeSO (LFSO), the reduced Li-ion diffusion barrier and the increased Li-rich octahedral configurations in LFMSO with higher configurational entropy imply the facilitated long-range Li-ion diffusion and the suppressed phase transition, which favor the high-rate capability and cycling stability. In addition, the large lattice distortion and Coulombic interaction between the anions and cations lead to the breathing of the unit cell during charge/discharge. The variation of the unit cell volume decreases to 2.5% upon Li-ion delithiation. A superstructure is observed in LFMSO for the first time. These findings help to pave the way for the research and development of novel cathode materials for the next generation LIBs.

25 ENERGY STORAGE↗
DOE OSTI2023

Origin of Rapid Delithiation In Secondary Particles Of LiNi 0.8 Co 0.15 Al 0.05 O 2 and LiNi y Mn z Co 1− y − z O 2 Cathodes

Abstract 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 0.8 Co 0.15 Al 0.05 O 2 . Here, nano‐focused X‐ray probes are used 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 (‐XRD) leverages the relationship between Li content and lattice parameter to further reveal that rate acceleration occurs between Li‐site fraction ( x Li ) ≈0.9 and ≈0.5 for LiNi 0.8 Co 0.15 Al 0.05 O 2 . Physics‐based modeling shows that, to reproduce the experimental results, the exchange current density ( i 0 ) must depend on x Li , and that i 0 should increase rapidly over three orders of magnitude at the transition point. The specifics and implications of this jump in i 0 are crucial to understanding the charge‐storage reaction of Li‐ion battery cathodes.

25 ENERGY STORAGE↗
DOE OSTI2023

The Mechanism of Fluorine Doping for the Enhanced Lithium Storage Behavior in Cation-Disordered Cathode Oxide

Li-rich cation-disordered rock-salt (DRX) materials have emerged as promising candidates for high-capacity oxide cathodes. Their fluorinated variants have shown improved cycling stability with effectively suppressed oxygen loss. However, a comprehensive understanding of how fluorination impacts the multiscale structure and lithium transportation in DRX remains elusive in experiments. In this study, the neutron total scattering technique in conjunction with the advanced reverse Monte Carlo (RMC) fitting method is employed to characterize the intricate structure of Li 1.16 Ti 0.37 Ni 0.37 Nb 0.1 O 2 (LTNNO) and the fluorinated Li 1.2 Ti 0.35 Ni 0.35 Nb 0.1 O 1.8 F 0.2 (LTNNOF). Through rigorous statistical analysis, the multiscale structural evolution upon fluorination is quantified from atomic (≤5 Å) to long-range scale (≈100 Å). The local Li-rich environments around F induce a modest 2.4% increment in the number of fast Li 0TM (transition metal) channels. Crucially, at a broader scale, the proportion of 0TM channels participating in percolation increases significantly from 2.9% in LTNNO to 8.7% in LTNNOF. Fluorination improves the capacity release mainly through merging isolated fast Li channels into the percolation network. This work experimentally unravels the multiscale mechanism of fluorination-induced performance improvement in DRX materials and highlights the necessity of adopting an advanced RMC fitting method to obtain a full view of the complex structural features in developing high-capacity DRX cathodes.

25 ENERGY STORAGE↗
DOE OSTI2024

Insight of Synthesis of Single Crystal Ni-Rich LiNi 1-x-y Co x Mn y O 2 Cathodes

Single-crystal Ni-rich LiNi 1-x-y Co x Mn y O 2 (NCM) cathodes have garnered widespread attention in the lithium-ion battery community due to their unique advantages in mechanical performance and their ability to minimize interfacial electrochemical side reactions. The synthesis of single-crystal materials with monodisperse and appropriate size, minimal lattice defects, and highly ordered structures is the key for high-performance batteries. However, achieving this goal poses challenges due to the lack of in-depth understanding regarding specific experimental parameters and the solid reaction mechanism during the synthesis process. Further, in this review, the aim is to provide an in-depth analysis of the critical process parameters involved in the synthesis and their impact on crystal morphology, structure, and electrochemical performance. Consequently, the first section focuses on the effect of the precursor morphology, lithium salt, atmosphere, and sintering procedure. In the second section, the study delves into an in-depth discussion of the solid reaction and crystal growth mechanism. Lastly, it is concluded by highlighting the prospects and challenges associated with the synthesis and application of single-crystal Ni-rich NCM cathodes.

25 ENERGY STORAGE↗
DOE OSTI2025

In Situ Diffraction and Ex Situ Transmission X‐Ray Microscopy Studies of Solid‐State Upcycling for NMC Cathodes

Upcycling of recycled LiNi 0.6 Mn 0.2 Co 0.2 O 2 (NMC622) cathodes offers an economical route to produce cathode materials with increased energy density (i.e., LiNi 0.8 Mn 0.1 Co 0.1 O 2 , NMC811) that meet the performance needs of present-day electric vehicles. In this work, solid-state upcycling of NMC622 via calcination with Ni(OH) 2 and LiOH was monitored using in situ synchrotron powder X-ray diffraction measurements. Sequential Rietveld refinements indicate that the calcination proceeds by initially converting Ni(OH) 2 to a rocksalt NiO phase followed by lithiation of NiO to form LiNiO 2 (LNO), with both NMC and LNO phases present in nearly equal proportions at the calcination endpoint. Variable-energy transmission X-ray microscopy tomograms of upcycled samples reveal that the NMC and LNO domains are intermixed at sub-micron length scales. Depth-dependent analysis of multi-elemental fitting maps matches the expected NMC811 composition at the secondary particle level and indicates that transition metal diffusion is not limited by the secondary particle size.

cathode upcycling↗
DOE OSTI2025

Mitigating Cyclable Li‐Ion Inventory Loss in Full Cells with Mn‐Rich Disordered Rocksalt Cathodes

Lithium (Li)- and manganese (Mn)-rich disordered rock salt (DRX) materials are promising cathode materials for next-generation Li-ion batteries. Although these cathode materials are Li-ions rich in their pristine state, their incorporation into full cells results in challenges with maintaining Li-ion inventory during cycling. Herein, the degradation mechanisms of DRX materials in different DRX||Graphite full cells are reported. It is found that DRX electrodes contain Li impurities, primarily due to the environmental sensitivity of mechanochemically synthesized DRX materials during sample transfer and storage. In addition, the structural instability of DRX triggers Mn dissolution. Dissolved Mn ions react with exposed Li x C y compounds and induce electrolyte decomposition on the anode, further depleting Li-ion inventory. Control experiments involving the pre-addition of Mn 2+ provide clear evidence of the impact of Mn dissolution on Li-ion inventory. The electrochemical activation process can stabilize DRX, alleviate Mn dissolution and thus mitigate the loss of Li-ion inventory. These mechanistic insights inform the development of chemical pre-lithiation and electrolyte additive strategies to collectively passivate interfaces, mitigate the effects of trace dissolved Mn ions, and preserve Li-ion inventory. Ultimately, the DRX||Graphite full cell achieves highly reversible electrochemical reactions with a high capacity retention. This study fills a research gap in DRX-based full cells and provides insights into degradation mechanisms and optimization strategies for their practical use.

36 MATERIALS SCIENCE↗