Resolving atomic-scale phase transformation and oxygen loss mechanism in ultrahigh-nickel layered cathodes for cobalt-free lithium-ion batteries
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77 NANOSCIENCE AND NANOTECHNOLOGY↗
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A Glance of the Layered Transition Metal Oxide Cathodes in Sodium and Lithium-ion Batteries: Difference and Similarities
The fast-growing demand of energy storage devices has prompted diverse battery techniques, while the state-of-the-art Li-ion batteries (LIBs) continue to flourish, Na-ion batteries (SIB) have been identified to be a promising alternative to share the burden with LIBs, particularly for large scale grid storage applications. Both LIBs and SIBs techniques work based on similar fundamental mechanisms, with a heavy focus on intercalation chemistry of layered transition metal (TM) oxides. However, the differences between Li-ion and Na-ion in terms of their size and Lewis acidity induce many different behaviors when crystallizing or diffusing in layered cathode materials. This minireview summarizes some typical cases where Li and Na-ion differ in layered cathode materials and discusses potential approaches to leverage their similarities and dissimilarities for future developments of high-performance Na-ion batteries.
Xiao, Biwei↗
Evolution of lithium ordering with (de)-lithiation in β-LiVOPO 4 : insights through solid-state NMR and first principles DFT calculations
The lithium-ion battery cathode material β-VOPO 4 is capable of intercalating more than one Li ion per transition metal ion due to the accessibility of both the V 5+ /V 4+ and V 4+ /V 3+ redox couples at ~4.5 V and ~2.3 V vs. Li, respectively, giving a theoretical capacity greater than ~300 mA h g -1 . The ability to perform full and reversible two Li-ion intercalation in this material, however, has been a matter of debate and the poor crystallinity of the fully lithiated phase has thus far precluded its complete structural characterisation by conventional diffraction-based methods. In this work, 7 Li and 31 P NMR spectroscopy, in combination with first principles DFT calculations, indicate that chemical lithiation results in a single phase β-Li 2 VOPO 4 exhibiting a complex Li ordering scheme with lithium ions occupying multiple disordered environments. 2D NMR 7 Li correlation experiments were used to deduce the most likely Li ordering for the β-Li 2 VOPO 4 phase from amongst several DFT optimised structures. In contrast, electrochemically lithiated β-Li 2- x VOPO 4 discharged to 1.6 V exhibits, in addition to β-Li 2 VOPO 4 , a β-Li 1.5 VOPO 4 phase. Additionally, the existence of β-Li 1.5 VOPO 4 is not reflected in the flat galvanostatic charge and discharge curves nor is evident from diffraction-based methods due to the very close structural similarity between the β-Li 1.5 VOPO 4 phase and β-Li 2 VOPO 4 phases. We demonstrate that solid state NMR spectroscopy, in combination with DFT results, provides a powerful tool for identifying intermediate states formed during charge/discharge of these complex phosphates as these phases can be distinguished from the end member phases primarily by the nature of the lithium ordering.
25 ENERGY STORAGE↗
Lattice-Oxygen-Driven Selective Oxidation Strategy for Stable Argyrodite Solid-State Lithium Metal Batteries
All-solid-state lithium metal batteries (ASSLMBs) with Li6PS5Cl argyrodite electrolytes and high-voltage LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes offer high energy density but suffer from rapid capacity fading due to the layered-to-rock-salt transition of NMC811 and structural degradation of Li6PS5Cl from parasitic interfacial reactions. Here, we demonstrate a catholyte engineering strategy using a Li2S scavenging additive to suppress interfacial reactivity and preserve the structural and electrochemical stability of both NMC811 and Li6PS5Cl. Incorporating 0.10 wt.% Li2S enables exceptional cycling stability, achieving 76% capacity retention after 550 cycles at C/10 and 88% retention after 800 cycles at C/3 at 60 degrees C, compared with rapid failure in pristine cells. Spectroscopic, electrochemical, and morphological analyses confirm that Li2S maintains electrode integrity by sustaining particle contact and suppressing phase decomposition. This work elucidates interfacial degradation pathways in NMC811/argyrodite systems and introduces a low-cost, scalable strategy to stabilize nickel-rich oxide cathodes in ASSLMBs, advancing their practical viability.
25 ENERGY STORAGE↗
Role of Redox-Inactive Transition-Metals in the Behavior of Cation-Disordered Rocksalt Cathodes
Owing to the capacity boost from oxygen redox activities, Li-rich cation-disordered rocksalts (LRCDRS) represent a new class of promising high-energy Li-ion battery cathode materials. Redox-inactive transition-metal (TM) cations, typically d 0 TM, are essential in the formation of rocksalt phases, however, their role in electrochemical performance and cathode stability is largely unknown. In the present study, the effect of two d 0 TM (Nb 5+ and Ti 4+ ) is systematically compared on the redox chemistry of Mn-based model LRCDRS cathodes, namely Li 1.3 Nb 0.3 Mn 0.4 O 2 (LNMO), Li 1.25 Nb 0.15 Ti 0.2 Mn 0.4 O 2 (LNTMO), and Li 1.2 Ti 0.4 Mn 0.4 O 2 (LTMO). Although electrochemically inactive, d 0 TM serves as a modulator for oxygen redox, with Nb 5+ significantly enhancing initial charge storage contribution from oxygen redox. Further studies using differential electrochemical mass spectroscopy and resonant inelastic X-ray scattering reveal that Ti 4+ is better in stabilizing the oxidized oxygen anions (O n- , 0 < n < 2), leading to a more reversible O redox process with less oxygen gas release. As a result, much improved chemical, structural and cycling stabilities are achieved on LTMO. Detailed evaluation on the effect of d 0 TM on degradation mechanism further suggests that proper design of redox-inactive TM cations provides an important avenue to balanced capacity and stability in this newer class of cathode materials.
25 ENERGY STORAGE↗
Boosting energy efficiency of Li-rich layered oxide cathodes by tuning oxygen redox kinetics and reversibility
In developing electrode materials for next-generation Li-ion batteries, significant efforts have been given to the energy, power density and cycling stability, with much less (if any) attention paid to the energy efficiency – arguably, the most important practical measure for large-scale applications. This is particularly true for the oxygen-redox active electrodes, such as Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 , the notorious energy-inefficient cathode that has an extremely high capacity but comes with large voltage hysteresis and voltage decay. Herein, we report the rational design of an energy-efficient Li-rich layered cathode along with high energy, power density and cycling stability enabled by tuning oxygen redox activity. Specifically, the target material Li 1.12 Ni 0.22 Co 0.13 Mn 0.52 O 2 exhibits an ultrahigh energy efficiency at 1 C (90.6%), high capacity (> 200 mAh g -1 ) with 98.9% retention and less than 150 mV decay at the extended 200 cycles. Overall, through direct comparison between the material and Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 , we show that the compositional change, although slightly, greatly improves the oxygen redox kinetics and reversibility, thereby boosts energy efficiency. The findings offer a strategy to narrow the gap between scientific interest and practical application of oxygen-redox chemistry.
36 MATERIALS SCIENCE↗
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↗
Opportunities and challenges in cathode development for non-lithium-ion batteries
Lithium (Li)-ion batteries have stimulated the societal transformation to clean energy systems. This carry-on electricity is revolutionizing how society communicates, functions, and evolves efficiently by enabling mobile electronics, zero-emission electric vehicles, and stationary energy storage. In preparation for the sustainable energy future, however, there are growing concerns about depleting critical elements used in the Li technology (e.g., lithium, cobalt, and nickel), especially for large-scale applications that will accelerate the rate of elemental consumption. Various non-Li-based rechargeable batteries composed of earth-abundant elements, such as sodium, potassium, magnesium, and calcium, have been proposed and explored as alternative systems to promote sustainable development of energy storage. In this perspective, we discuss challenges in Li-ion batteries in the sustainability aspect and provide our opinions on the potential applications of non-Li-based batteries. We also highlight the current status, important progress, and remaining challenges of the Li-alternative technologies.
25 ENERGY STORAGE↗
Recovery of cathode materials from spent lithium-ion batteries using eutectic system of lithium compounds
Not Available
Ji, Yi (ORCID:0000000205900994)↗
Electron Backscatter Diffraction for Investigating Lithium-Ion Electrode Particle Architectures
Not Available
25 ENERGY STORAGE↗
Oxygen-Based Anion Redox for Lithium Batteries
The importance of current Li-ion batteries (LIBs) in modern society cannot be overstated. While the energy demands of devices increase, the corresponding enhancements in energy density of battery technologies are highly sought after. Currently, many different battery concepts, such as Li-S and metal-air among many others, have been investigated. However, their practical implementation has mostly been restricted to the prototyping stage. In fact, most of these technologies require rework of existing Li-ion battery manufacturing facilities and will naturally incur resistance to change from industry. For this reason, one specifically attractive technology, anionic redox in transition metal oxides, has gained much attention in the recent years. Its ability to be directly used in already established processes and higher energy density with similar electrolyte formulation make it a key materials research direction for next generation Li-ion batteries. In regular LIBs, the redox active centers are the transition metal cation. In anion redox, both the anion (typically O) and the transition metal cation are utilized as redox centers with enormous implications for increasing energy density. This new material can be highly competitive for replacing the current LIB technologies. However, much is still unknown about its cyding mechanism. Upon activating the O redox couples, most cationic and anionic redox active materials will either evolve O 2 or undergo irreversible structural degradation with associated severe decreases in electrochemical performance. By understanding the transition from full anion redox to partial cationic and anionic redo; we hope readers can gain a deeper understanding of the topic. This Account will focus mainly on the work that was conducted by our group at Argonne National Laboratory. Herein, the phenomenon of cationic and anionic redox in a lithium-ion battery cathode will first be discussed. Our work in resonant inelastic X-ray scattering to investigate the spectroscopic features of O after delithiation has found potential "fingerprint" signals that could likely be used to identify and confirm reversible O redox if corroborated with other techniques. To follow, we will examine our work on Li-O 2 batteries. While our group and the research community have had many significant contributions and improvements to the field of Li-O 2 (such as decreasing overpotential and achieving cyclability in air environment), its practical application is still far from realization. Perhaps our most important contribution to this area is the discovery that Ir deposited on reduced graphene oxide can be used to halt the reduction of O 2 at the LiO 2 oxidation state. This not only significantly decreases the charge overpotential but also presents the important concept of oxidation-state controlled discharge. Subsequently, we will focus on our oxidation state-controlled redox-based charging of oxygen in a pure oxygen redox Li-ion battery. Future implications of this technology will be emphasized.
25 ENERGY STORAGE↗
Operando Bragg Coherent Diffraction Imaging of LiNi 0.8 Mn 0.1 Co 0.1 O 2 Primary Particles within Commercially Printed NMC811 Electrode Sheets
Due to complex degradation mechanisms, disparities between the theoretical and practical capacities of lithium-ion battery cathode materials persist. Specifically, Ni-rich chemistries such as LiNi 0.8 Mn 0.1 Co 0.1 O 2 (or NMC811) are one of the most promising choices for automotive applications; however, they continue to suffer severe degradation during operation that is poorly understood, thus challenging to mitigate. Here in this paper we use operando Bragg coherent diffraction imaging for 4D analysis of these mechanisms by inspecting the individual crystals within primary particles at various states of charge (SoC). Although some crystals were relatively homogeneous, we consistently observed non-uniform distributions of inter- and intracrystal strain at all measured SoC. Pristine structures may already possess heterogeneities capable of triggering crystal splitting and subsequently particle cracking. During low-voltage charging (2.7–3.5 V), crystal splitting may still occur even during minimal bulk deintercalation activity; and during discharging, rotational effects within parallel domains appear to be the precursor for the nucleation of screw dislocations at the crystal core. Ultimately, this discovery of the central role of crystal grain splitting in the charge/discharge dynamics may have ramifications across length scales that affect macroscopic performance loss during real-world battery operation.
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
Unlocking the passivation nature of the cathode–air interfacial reactions in lithium ion batteries
Not Available
25 ENERGY STORAGE↗
Highly reversible oxygen redox in layered compounds enabled by surface polyanions
Oxygen-anion redox in lithium-rich layered oxides can boost the capacity of lithium-ion battery cathodes. However, the over-oxidation of oxygen at highly charged states aggravates irreversible structure changes and deteriorates cycle performance. Here, we investigate the mechanism of surface degradation caused by oxygen oxidation and the kinetics of surface reconstruction. Considering Li 2 MnO 3 , we show through density functional theory calculations that a high energy orbital (lO 2p’ ) at under-coordinated surface oxygen prefers over-oxidation over bulk oxygen, and that surface oxygen release is then kinetically favored during charging. We use a simple strategy of turning under-coordinated surface oxygen into polyanionic (SO 4 ) 2- , and show that these groups stabilize the surface of Li 2 MnO 3 by depressing gas release and side reactions with the electrolyte. Experimental validation on Li 1.2 Ni 0.2 Mn 0.6 O 2 shows that sulfur deposition enhances stability of the cathode with 99.0% capacity remaining (194 mA h g -1 ) after 100 cycles at 1 C. Our work reveals a promising surface treatment to address the instability of highly charged layered cathode materials.
25 ENERGY STORAGE↗
Sub-10 second fly-scan nano-tomography using machine learning
Abstract X-ray computed tomography is a versatile technique for 3D structure characterization. However, conventional reconstruction algorithms require that the sample not change throughout the scan, and the timescale of sample dynamics must be longer than the data acquisition time to fulfill the stable sample requirement. Meanwhile, concerns about X-ray-induced parasite reaction and sample damage have driven research efforts to reduce beam dosage. Here, we report a machine-learning-based image processing method that can significantly reduce data acquisition time and X-ray dose, outperforming conventional approaches like Filtered-Back Projection, maximum-likelihood, and model-based maximum-a-posteriori probability. Applying machine learning, we achieve ultrafast nano-tomography with sub-10 second data acquisition time and sub-50 nm pixel resolution in a transmission X-ray microscope. We apply our algorithm to study dynamic morphology changes in a lithium-ion battery cathode under a heating rate of 50 o C min −1 , revealing crack self-healing during thermal annealing. The proposed method can be applied to various tomography modalities.
36 MATERIALS SCIENCE↗
Manganese-rich high entropy oxides for lithium-ion batteries:materials design approaches to address voltage fade
Lithium- and manganese-rich oxides are of interest as lithium-ion battery cathode materials as Mn is earth abundant, low cost, and can deliver high capacity. Herein, a high entropy strategy was used to prepare Mn rich high entropy oxide (HEO) materials by including four additional metals (Ni, Co, Fe and Al) in the compositions using a mild co-precipitation method. Two HEOs (Li x Ni 0.1 Mn 0.6 Co 0.1 Al 0.1 Fe 0.1 O y , where x = 1.5 for HEO-L and x = 0.5 for HEO-H) with layered and spinel-layered hybrid structures were investigated where the morphology, elemental composition, structure, atomic level phase distribution, and electrochemistry were determined. The HEO-L samples involve a Li 2 TMO 3 layered structure with ~39% stacking faults. HEO-H is a hybrid structure comprised of 80 wt% spinel and 20 wt% LiMO 2 layered structure. The high entropy manganese-rich HEO-L showed higher capacity and 93% retention of the average voltage after 100 cycles while HEO-H showed higher capacity retention and near 100% average voltage retention. Finally, operando X-ray absorption spectroscopy revealed that the Ni, Co, and Mn are redox active in both materials while the Fe center remains at the Fe 3+ oxidation state throughout cycling, where the changes in the oxidation states for both materials during discharge were consistent with the delivered electrochemical capacity rationalizing the observed electrochemistry.
25 ENERGY STORAGE↗