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DOE OSTI2022

Anomalous Ferromagnetic Behavior in Orthorhombic Li 3 Co 2 SbO 6

Monoclinic Li 3 Co 2 SbO 6 has been proposed as a Kitaev spin liquid candidate and investigated intensively, whereas the properties of its polymorph, the orthorhombic phase, are less known. In this work, we report the magnetic properties of orthorhombic Li 3 Co 2 SbO 6 as revealed by dc and ac magnetic susceptibility, muon spin relaxation (μSR), and neutron diffraction measurements. Successive magnetic transitions at 115, 89, and 71 K were observed in the low-field dc susceptibility measurements. The transitions below T N (115 K) are suppressed at higher applied fields. However, zero-field ac susceptibility measurements reveal distinct frequency-independent transitions at about 114, 107, 97, 79, and 71 K. A long-range magnetic ordered state was confirmed by specific heat, μSR, and neutron diffraction measurements, all indicating a single transition at about 115 K. The discrepancy between different measurements is attributed to possible stacking faults and/or local disorders of the ferromagnetic zigzag chains, resulting in ferromagnetic boundaries within the overall antiferromagnetic matrix.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Comparing Thermal Neutron Scintillators for Use With SiPM-Readout Detectors

Scintillator-based thermal neutron detectors for scientific scattering facilities offer an effective combination of large-area coverage and good spatial resolution. At Oak Ridge National Laboratory, silicon photomultiplier (SiPM)-readout Anger cameras using 6 Li glass scintillators have been developed, but the spatial resolution of these detectors is limited by the relatively low light yield of the glass. Recently, several brighter scintillator compositions with sufficient 6 Li concentration have emerged as promising candidates for higher-resolution imaging. Here, in this work, we evaluate five scintillator materials: GS20, LiF/ZnS:Ag, LiF/ZnO:Zn, LiI:Eu, and Cs 2 LiYCl 6 :Ce, each mounted on a SiPM Anger camera. For each scintillator, the neutron detection efficiency, spatial resolution, and count rate capabilities were measured and compared. Each of the new compositions achieved a spatial resolution better than 0.5 mm, compared to 0.66 mm for GS20, with LiI:Eu reaching the best value of 0.32 mm. Although these compositions improve the spatial resolution of the Anger camera, their longer pulse decay times limit their use in high count rate applications, and the camera’s hardware must be optimized for the different properties of the new scintillators.

Neutron detectors↗
DOE OSTI2022

Highly reversible Li 2 RuO 3 cathodes in sulfide-based all solid-state lithium batteries

The practical application of high-capacity lithium-rich cathode materials in lithium-ion batteries has been largely restricted by severe side reactions with electrolytes. Herein, we report a highly stable lithium-rich Li 2 RuO 3 cathode by forming a passivating solid electrolyte interphase at the interface with a sulfide solid electrolyte such as Li 6 PS 5 Cl in all-solid-state lithium batteries (ASSLBs), which efficiently suppresses serious parasitic interfacial reactions and fast-increasing interfacial impedance normally observed in liquid electrolytes. The exceptionally high interfacial stability of the Li 2 RuO 3 /sulfide electrolyte interface contributes to a high reversible capacity of 257 mA h g –1 of Li 2 RuO 3 at 0.05C rate, and unprecedented cycling stability with 90% capacity retention after 1000 cycles at 1C rate. Iin this work, comprehensive experimental characterizations and first-principles calculations disclose that electronically insulating interfacial reaction products forming at the interface between the Li 2 RuO 3 cathode and Li 6 PS 5 Cl facilitate the formation of a stable and passivating interphase and block the continuous side reactions. Importantly, reversible oxygen redox activity of Li 2 RuO 3 is well-maintained in this configuration of ASSLBs even after 600 cycles, thus the common voltage decay of the Li-rich material is also significantly reduced. These new discoveries demonstrate the critical role of interface design for achieving prolonged cycling stability of lithium-rich cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2025

Understanding the Effect of Chiral NN Parametrization on Nuclear Shapes From an Ab Initio Perspective

The ab initio symmetry-adapted no-core shell model naturally describes nuclear deformation and collectivity, and is therefore well-suited to studying the dynamics and coexistence of shapes in atomic nuclei. For the first time, we analyze how these features in low-lying states of 6 Li and 12 C are impacted by the underlying realistic nucleon-nucleon interaction. We find that the interaction parametrization has a notable but limited effect on collective shapes in the lowest 6 Li and 12 C states, while collective structures in the excited 2 + state of 12 C are significantly more sensitive to the interaction parameters and exhibits emergent shape coexistence.

Becker, Kevin S. [Louisiana State University, Bato↗
DOE OSTI2022

Isotopic Signatures of Lithium Carbonate and Lithium Hydroxide Monohydrate Measured Using Raman Spectroscopy

Lithium isotopic ratios have wide ranging applications as chemical signatures, including improved understanding of geochemical processes and battery development. Measurement of isotope ratios using optical spectroscopies would provide an alternative to traditional mass spectrometric methods, which are expensive and often limited to a chemical laboratory. In this work, Raman spectra of 7 Li 2 CO 3 , 6 Li 2 CO 3 , 7 LiOH*H 2 O and 6 LiOH*H 2 O have been measured to determine the effect of lithium isotope substitution on the Raman molecular vibrations. Thirteen peaks were observed in the spectrum of lithium carbonate, with discernable isotopic shifts occurring in eleven of the thirteen vibrations, two of which have not been previously reported in the literature. The spectrum of lithium hydroxide monohydrate contained nine peaks, with discernable isotopic shifts occurring in eight of the nine vibrations, four of which have not been previously reported in the literature. The Raman spectral data reported here for lithium carbonate and lithium hydroxide monohydrate are in agreement with the previously reported works in the literature, in which the Raman active modes of these molecules were first identified and assigned. However, due to the stability and resolution of the detection system used in this work, isotopic shifts with a magnitude less than one wavenumber have been identified. Principal Component Regression was used to evaluate the sensitivity to isotopic content of small Raman peak shifts in Li 2 CO 3 and indicates differences greater than 2 atom-% could be reliably determined. These measurements add to the body of work on lithium isotope Raman spectroscopy for these two compounds and increases the number of Raman bands which could be used for lithium isotope content analysis.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Achieving stable all-solid-state lithium-metal batteries by tuning the cathode-electrolyte interface and ionic/electronic transport within the cathode

All-solid-state batteries with sulfide electrolytes and high-nickel layered oxide cathodes attract much interest due to their high specific energy. However, their cycling performance is primarily influenced by the interface between the sulfide electrolyte and the high-Ni layered oxide particles, which requires the use of composite cathodes with high ionic and electronic conductivities to achieve a kinetically stable interface inside the cathode. Here, we apply Ti 2 O 3 particles to the high-Ni cathode LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), where Ti 2 O 3 not only acts as an electronic conductor to provide a fast diffusion path for electrons in the composite cathode, but also absorbs the lattice oxygen released from NCM811 cathode during cycling, stabilizing the Li 6 PS 5 Cl/NCM811 interface and suppressing electrolyte oxidation. The as-modified cathode exhibits an initial specific capacity of 192 mAh g -1 and retains 166 mAh g -1 after 140 cycles at 0.1C rate with a good capacity retention of 86.5%. Furthermore, the composite cathode displays high rate capability even at 1C rate. By contrast, the unmodified Li 6 PS 5 Cl/NCM811 cathode shows poor cycling performance with only 130 mAh g -1 remaining after 130 cycles. This work provides a new direction for the design of cathodes for all-solid-state batteries that can deliver high specific energy with long cycle life.

25 ENERGY STORAGE↗
DOE OSTI2025

Expanding Configurational Complexity through Dipole Dilution in Pseudohalide Argyrodite Ion Conductors

The advantageous properties of (pseudo)halide argyrodite ion conductors of the formula Li 6 PS 5 X (X = Cl – , Br – , I – , CN – ) have motivated extensive studies of their structure-transport relationships, particularly as they pertain to the role of atomic site disorder. The argyrodite structure can accommodate additional configurational complexity to promote ion transport via extended three-anion site mixing and the potential for orientational disorder of molecular anions. In this work, we explore a ternary anion system including the cyanide anion, expanding site disorder and introducing dipolar orientations as an additional degree of freedom. We prepared the series Li 6 PS 5 (CN) 1–x Br x , in which the dipolar cyanide anions are systematically diluted with bromide. We find that anion disorder, as determined by synchrotron and neutron diffraction and quantified by configurational entropy (S config ), is correlated with lowered activation barriers and increased lithium ion conductivity. We propose that S config describes the electrostatic heterogeneity of the Li environments, flattening the energetic landscape for ion transport. While anion substitution strongly impacts the activation barrier for transport, the temperature-independent Arrhenius prefactor does not follow the same trend. Through heat-capacity measurements of attempt frequency and deconvolution of terms within the prefactor, we rationalize the apparent decoupling of activation energy and prefactor to strong cyanide-lithium interactions that increase the entropy of migration. Together, these results expand the structure–property relationships in the argyrodite family to encompass multiple facets of disorder and the subsequent impact on lithium ion transport.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Self-Stabilized LiNi 0.8 Mn 0.1 Co 0.1 O 2 in thiophosphate-based all-solid-state batteries through extra LiOH

Nickle-rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NMC 811) cathode material exhibits engaging properties in high energy density and low cost, making it great potential for the next generation high-energy all-solid-state lithium batteries (ASSLBs). However, NMC 811 suffers from severe surface electrochemical, chemical, and voltage incompatibility towards solid-state electrolytes (SSE), especially thiophosphate-based electrolytes like Li 6 PS 5 Cl. Although diverse coating methods have been made to overcome this issue, they are typically cumbersome and expensive. A coating strategy that satisfied all the requirements of cost-efficiency, stability, uniformity, scalability, and easy-achieving is still challenging. Here, we developed a LiOH-based surface stabilization strategy that provides a ~10 nm stable permeable layer on NMC 811. After one-step sintering of NMC 811 precursor mixed with LiOH, which is commonly used for NMC 811 lithiation process, excessive LiOH simultaneously distributes on NMC 811 particles. Unlike other reported methods, this coating method can be easily controlled and fabricated without additional complicated processes. By simply controlling the thickness of LiOH layer, which protects the Li 6 PS 5 Cl solid electrolyte materials from being oxidized, optimized cycling stability can be obtained for 600 cycles with capacity of 130 mAh g – 1 on average at a wide electrochemical window of 2.50–4.20 V (vs. Li-In).

25 ENERGY STORAGE↗
DOE OSTI2022

Gamma-based nuclear fusion measurements at inertial confinement fusion facilities

Experiments performed on an inertial confinement fusion (ICF) platform offer a unique opportunity to study nuclear reactions, including reaction branches that are useful for diagnostic applications in ICF experiments as well as several that are relevant to nuclear astrophysics. In contrast to beam-accelerator experiments, experiments performed on an ICF platform occur over a short time scale and produce a plasma environment with physical parameters that are directly relevant to big bang and/or stellar nucleosynthesis. Several reactions of interest, such as D(T,γ) 5 He, H(D,γ) 3 He, H(T,γ) 4 He, and T( 3 He,γ) 6 Li produce high-energy gamma rays. S factors or branching ratios for these four reactions have recently been studied using various temporally-resolved Cherenkov detectors at the Omega laser facility. This work describes these detectors as well as the current standard technique for performing these measurements. Recent results for reactions D(T,γ) 5 He, H(D,γ) 3 He, H(T,γ) 4 He, and T( 3 He,γ) 6 Li are reviewed and compared to accelerator-based measurements. Limitations associated with implosion experiments and use of the current standard gamma detectors are discussed. A basic design for a gamma spectrometer for use at ICF facilities is briefly outlined.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

A Large Area Picosecond Photodetector for Neutron Transmission Measurements at DICER at LANSCE

The Device for Indirect Capture Experiments on Radionuclides (DICER) is a new instrument that is being developed at the Los Alamos Neutron Science Center (LANSCE) to study neutron capture reactions on short-lived radionuclides. To achieve that, DICER is using an indirect technique based on measuring the neutron transmission through very small samples (0.12–1.2 mm in diameter, $\mu \text{g}$ -mg in mass). The main detection system of DICER consists of two dual photomultiplier (PMT)-based detectors which are sensitive to the scintillation light produced when neutrons interact with 6 Li glass disks. DICER is developing a new collimation system that includes a 0.1-mm collimator. In such small sizes, the need for neutron beam imaging is crucial and necessary to confirm the appropriate alignment between the irradiated sample and the neutron detectors. The large area picosecond photodetector (LAPPD) is a multichannel plate (MCP)-based photodetector, with picosecond-level timing, single-photon detection capabilities, and spatial resolution of the order of 1 mm. Coupling the LAPPD with a 6 Li glass scintillator results in a neutron imaging detector. The first irradiation of the LAPPD at DICER indicated that apart from imaging the beam, the LAPPD can be used as the main neutron detection system. Furthermore, these results were proof of principle measurements demonstrating the capabilities of the beamline, and the challenge with small samples will be addressed in the future. The first efforts and developments, including irradiations of the LAPPD and the first beam images, will be presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Evidence of lithium mobility under neutron irradiation

Understanding the evolution of intermetallic materials in high-radiation environments is of great importance for fusion science and national security. Tritium ( 3 H) and lithium ( 6 Li, 7 Li) transport within neutron irradiated claddings coated with aluminide (FeAl3) has been investigated using state-of-the-art multimodal imaging. Specifically, scanning electron microscopy – focused ion beam (SEM-FIB) was used to prepare irradiated coating lift-out samples for follow-on microanalysis. Here, scanning transmission electron microscopy (STEM) was used to acquire atomic-scale information on the carbonaceous structure and elemental mapping. Atomic force microscopy (AFM) was used to determine lift-out dimensions nondestructively. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) spectral and depth profiling show unexpected lithium isotopic distributions in the irradiated cladding, raising an important evidence of possible light isotope mobility within the cladding under elevated temperature and irradiation. ToF-SIMS three-dimensional chemical mappings of mid- and bottom-cladding coatings show light isotopic (e.g., 3 H, 6 Li, 7 Li) distributions in the irradiated coating and give new insights into the fundamental mechanism related to transport mechanisms within the cladding. Multimodal imaging is power to link microstructure, chemistry, and nanoscale defects that impact reliability of these materials. Furthermore, chemical mapping offers observations of the microstructural evolution due to irradiation and provides insights into unexpected material transport under extreme conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Comparison of optical potential for nucleons and $\varDelta $ resonances

Precise modeling of neutrino interactions on nuclear targets is essential for neutrino oscillations experiments. The modeling of the energy of final state particles in quasielastic (QE) scattering and resonance production on bound nucleons requires knowledge of both the removal energy of the initial state bound nucleon as well as the average Coulomb and nuclear optical potentials for final state leptons and hadrons. We extract the average values of the real part of the nuclear optical potential for final state nucleons ( $U_{opt}^{QE}$ U opt QE ) as a function of the nucleon kinetic energy from inclusive electron scattering data on nuclear targets ( $_\mathbf{6 }^\mathbf{12 }{} \mathbf{C} $ 6 12 C + $_\mathbf{8 }^\mathbf{16 }{} \mathbf{O} $ 8 16 O , $_\mathbf{20 }^\mathbf{40 }{} \mathbf{Ca} $ 20 40 Ca + $_\mathbf{18 }^\mathbf{40 }{} \mathbf{Ar} $ 18 40 Ar , $_\mathbf{3 }^\mathbf{6 }{} \mathbf{Li} $ 3 6 Li , $_\mathbf{18 }^\mathbf{27 }{} \mathbf{Al} $ 18 27 Al , $_\mathbf{26 }^\mathbf{56 }{} \mathbf{Fe} $ 26 56 Fe , $_\mathbf{82 }^\mathbf{208 }{} \mathbf{Pb} $ 82 208 Pb ) in the QE region and compare to calculations. We also extract values of the average of the real part of the nuclear optical potential for a $\varDelta (1232)$ Δ ( 1232 ) resonance in the final state ( $U^\varDelta _{opt}$ U opt Δ ) within the impulse approximation. We find that $U^\varDelta _{opt}$ U opt Δ is more negative than $U_{opt}^{QE}$ U opt QE with $U^\varDelta _{opt}\approx $ U opt Δ ≈ 1.5 $U_{opt}^{QE}$ U opt QE for $_\mathbf{6 }^\mathbf{12 }{} \mathbf{C} $ 6 12 C .

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Decoupling first-cycle capacity loss mechanisms in sulfide solid-state batteries

Solid-state batteries (SSBs) promise more energy-dense storage than liquid electrolyte lithium-ion batteries (LIBs). However, first-cycle capacity loss is higher in SSBs than in LIBs due to interfacial reactions. The chemical evolution of key interfaces in SSBs has been extensively characterized. Electrochemically, however, we lack a versatile strategy for quantifying the reversibility of solid electrolyte (SE) redox for established and next-generation SSB electrolytes. In this work, we perform tailored electrochemical tests and operando X-ray diffraction to disentangle reversible and irreversible sources of capacity loss in positive electrodes composed of Li 6 PS 5 Cl SE, Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 (NMC), and carbon conductive additives. We leverage an atypically low voltage cutoff (2.0 V vs. Li/Li + ) to quantify the reversibility of SE redox. Using slow (5.5 mA g NMC −1 ) cycling paired with >100 h low-voltage holds, our cells achieve a surprising 96.2% first-cycle coulombic efficiency, which is higher than previously reported (mean: 72%, maximum: 91.6% across surveyed literature). We clarify that sluggish NMC relithiation kinetics have been historically mistaken for permanently irreversible capacity loss. In conclusion, through systematic decoupling of loss mechanisms, we uncover the unexpected reversibility of SE redox and isolate the major contributors to capacity loss, outlining a strategy for accurate assessment of next-generation SE materials and interface modifications.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Material Design Strategy for Halide Solid Electrolytes Li 3 MX 6 (X = Cl, Br, and I) for All-Solid-State High-Voltage Li-Ion Batteries

Although several solid electrolyte (SE) candidates have been explored, achieving the necessary combination of performance, stability, and processability has been challenging. Recently, several lithium ternary halides have attracted increasing attention for SEs because of their favorable combination of high ionic conductivity and wide electrochemical window. This study aims to provide a material design strategy for lithium halides Li 3 MX 6 (X = Cl, Br, and I) for high-voltage all-solid-state Li-ion batteries, achieved by the systematic investigation of crystal structures, phase and electrochemical stabilities, electronic and mechanical properties, and ionic conductivities. Calculation results reveal that the electronegativity difference between M and X affects structural properties and stabilities. Weak Coulomb interactions in Li 3 MX 6 result in the preference of the monoclinic phase, and the oxidation potential and chemical stability against the cathode materials of Li 3 MX 6 increase for relatively small X. Chlorides exhibit the highest oxidation potential (~4.3 V) among Li 3 MX 6 , suggesting that chlorides are appropriate SEs for high-voltage cathodes. The band gap and elastic moduli increase for relatively small X, suggesting the relatively low electronic conductivity and elastic deformability of chlorides. Chlorides with transition metals typically exhibit trigonal phases, a wider electrochemical stability window, a larger band gap, and higher elastic moduli compared to other types of halides. Additionally, chloride Li 3 MCl 6 is expected to have relatively high ionic conductivities with the aliovalent substitution of M 3+ to Zr 4+ and the anion mixing of Cl with Br. The findings of this study will provide fundamental guidelines for the development of lithium halide SEs for high-voltage all-solid-state Li-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2020

Direct thermal neutron detection by the 2D semiconductor 6 LiInP 2 Se 6

Highly efficient neutron detectors are critical in many sectors, including national security, medicine, crystallography and astronomy. The main neutron detection technologies currently used involve 3 He-gas-filled proportional counters and light scintillators for thermalized neutrons. Semiconductors could provide the next generation of neutron detectors because their advantages could make them competitive with or superior to existing detectors. In particular, solids with a high concentration of high-neutron-capture nuclides (such as 6 Li, 10 B) could be used to develop smaller detectors with high intrinsic efficiencies. However, no promising materials have been reported so far for the construction of direct-conversion semiconductor detectors. Here we report on the semiconductor LiInP 2 Se 6 and demonstrate its potential as a candidate material for the direct detection of thermal neutrons at room temperature. This compound has a good thermal-neutron-capture cross-section, a suitable bandgap (2.06 electronvolts) and a favourable electronic band structure for efficient electron charge transport. We used α particles from an 241 Am source as a proxy for the neutron-capture reaction and determined that the compact two-dimensional (2D) LiInP 2 Se 6 detectors resolved the full-energy peak with an energy resolution of 13.9 per cent. Direct neutron detection from a moderated Pu–Be source was achieved using 6 Li-enriched (95 per cent) LiInP 2 Se 6 detectors with full-peak resolution. Here, we anticipate that these results will spark interest in this field and enable the replacement of 3 He counters by semiconductor-based neutron detectors.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Boron-Based Neutron Scintillator Screens for Neutron Imaging

In digital neutron imaging, the neutron scintillator screen is a limiting factor of spatial resolution and neutron capture efficiency and must be improved to enhance the capabilities of digital neutron imaging systems. Commonly used neutron scintillators are based on 6 LiF and gadolinium oxysulfide neutron converters. This work explores boron-based neutron scintillators because 10 B has a neutron absorption cross-section four times greater than 6Li, less energetic daughter products than Gd and 6 Li, and lower γ-ray sensitivity than Gd. These factors all suggest that, although borated neutron scintillators may not produce as much light as 6 Li-based screens, they may offer improved neutron statistics and spatial resolution. This work conducts a parametric study to determine the effects of various boron neutron converters, scintillator and converter particle sizes, converter-to-scintillator mix ratio, substrate materials, and sensor construction on image quality. The best performing boron-based scintillator screens demonstrated an improvement in neutron detection efficiency when compared with a common 6 LiF/ZnS scintillator, with a 125% increase in thermal neutron detection efficiency and 67% increase in epithermal neutron detection efficiency. The spatial resolution of high-resolution borated scintillators was measured, and the neutron tomography of a test object was successfully performed using some of the boron-based screens that exhibited the highest spatial resolution. For some applications, boron-based scintillators can be utilized to increase the performance of a digital neutron imaging system by reducing acquisition times and improving neutron statistics.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Understanding the Fluorination of Disordered Rocksalt Cathodes through Rational Exploration of Synthesis Pathways

Here, we have designed and tested several synthesis routes targeting a highly fluorinated disordered rocksalt (DRX) cathode, Li 1.2 Mn 0.4 Ti 0.4 O 1.6 F 0.4 , with each route rationalized by thermochemical analysis. Precursor combinations were screened to raise the F chemical potential and avoid the formation of LiF, which inhibits fluorination of the targeted DRX phase. MnF 2 was used as a reactive source of F, and Li 6 MnO 4 , LiMnO 2 , and Li 2 Mn 0.33 Ti 0.66 O 3 were tested as alternative Li sources. Each synthesis procedure was monitored using a multi-modal suite of characterization techniques including X-ray diffraction, nuclear magnetic resonance, thermogravimetric analysis, and differential scanning calorimetry. From the resulting data, we advance the understanding of oxyfluoride synthesis by outlining the key factors limiting F solubility. At low temperatures, MnF 2 consistently reacts with the Li source to form LiF as an intermediate phase, thereby trapping F in strong Li-F bonds. LiF can react with Li 2 TiO 3 to form a highly lithiated and fluorinated DRX (Li 3 TiO 3 F); however, MnO is not easily incorporated into this DRX phase. Although higher temperatures typically increase solubility, the volatility of LiF above its melting point (848 °C) inhibits fluorination of the DRX phase. Based on these findings, metastable synthesis techniques are suggested for future work on DRX fluorination.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Multimodal quantification of degradation pathways during extreme fast charging of lithium-ion batteries

Enabling fast charging of Li-ion batteries will be a key step towards realizing the technology's full potential in electric vehicles. Currently, fast charging is limited by a variety of processes that reduce cell capacity upon extended cycling. Using a multimodal approach combining incremental capacity analysis (dQ/dV), high energy X-ray diffraction (HEXRD), and mass spectrometry titration (MST), we identify specific degradation mechanisms—including Li plating, dead Li x C 6 formation, Li 2 C 2 formation, solid carbonate solid-electrolyte interphase (SEI) deposition, and loss of positive electrode active material (LAM PE )—that occur during extended fast charge cycling. We find that Li plating is the major source of capacity loss in cells cycled at 6C, while non-carbonate SEI species deposition on the graphite anode is the main source of capacity loss when cycled at 4C. We also study local degradative phenomena by examining specific ~1–5 cm 2 regions of the cells using HEXRD and MST. Here, we find that plated Li is often collocated with dead Li x C 6 , Li 2 C 2 , and solid carbonate SEI species, and these additional species cumulatively account for ~20% of the capacity lost during 6C cycling. Finally, in a cell with an anomalously high amount of LAM PE (quantified via dQ/dV), we find that regions of cathode degradation were accompanied by non-carbonate SEI products on the adjacent region of the anode. We postulate that this phenomenon arises due to crosstalk between the electrodes, wherein soluble electrolyte oxidation products formed at the delithiated cathode migrate to the graphite anode and are ultimately deposited on the graphite surface. This work demonstrates the utility of combining multiple characterization techniques to reveal a more holistic understanding of degradative phenomena that occur across multiple length scales during fast charge.

25 ENERGY STORAGE↗