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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

A Comparative Study of Degradation Behaviors of LiFePO 4 , LiMn 2 O 4 , and LiNi 0.8 Mn 0.1 Co 0.1 O 2 in Different Aqueous Electrolytes

Aqueous Li-ion batteries (ALIBs) are an important class of battery chemistries owing to the intrinsic non-flammability of aqueous electrolytes. However, water is detrimental to most cathode materials and could result in rapid cell failure. Identifying the degradation mechanisms and evaluating the pros and cons of different cathode materials are crucial to guide the materials selection and maximize their electrochemical performance in ALIBs. Here, in this study, we investigate the stability of LiFePO 4 (LFP), LiMn 2 O 4 (LMO) and LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC) cathodes, without protective coating, in three different aqueous electrolytes, i.e., salt-in-water, water-in-salt, and molecular crowding electrolytes. The latter two are the widely reported "water-deficient electrolytes." LFP cycled in the molecular crowding electrolyte exhibits the best cycle life in both symmetric and full cells owing to the stable crystal structure. Mn dissolution and surface reduction accelerate the capacity decay of LMO in water-rich electrolyte. On the other hand, the bulk structural collapse leads to the degradation of NMC cathodes. LMO demonstrates better full-cell performance than NMC in water-deficient aqueous electrolytes. LFP is shown to be more promising than LMO and NMC for long-cycle-life ALIB full cells, especially in the molecular crowding electrolyte. However, none of the aqueous electrolytes studied here provide enough battery performance that can compete with conventional non-aqueous electrolytes. This work reveals the degradation mechanisms of olivine, spinel, and layered cathodes in different aqueous electrolytes and yields insights into improving electrode materials and electrolytes for ALIBs.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Preparing Li-garnet electrodes with engineered structures by phase inversion and high shear compaction processes

We report solid-state lithium batteries are promising for safety and energy density com-pared with traditional lithium-ion batteries. However, the large interfacial resistance between the electrode and electrolyte is a bottleneck to achieving high-performance solid-state batteries. Engineered electrode structures with a porous scaffold of the solid electrolyte material are promising to lower the interfacial resistance and provide a mechanical support for a thin solid electrolyte layer. In this work, two ceramic processing techniques are used to fabricate porous/dense bilayer architectures based on a Li 6.25 Al 0.25 La 3 Zr 2 O 12 (LLZO) Li-garnet material. Finger-like vertically aligned pores are created by the phase inversion (PI) process. A water bath presaturated with Li salt prevents Li loss during the PI solvent exchange step. Pore size and porosity can be optimized by adjusting the bath temperature. The high shear compaction process was used to prepare LLZO tapes with 40, 60, and 80 vol% poreformer. The porosity of the tapes after sintering is 39.5%, 58.4%, and 75.4%, respectively. Microtomography exhibits the porosity, pore shape, and pore distribution of the tapes. A typical cathode material LiNi 0.33 Mn 0.33 Co 0.33 O 2 (NMC) is filled into the pores via vacuum infiltration, and a dense cathode layer is formed within the garnet scaffold.

25 ENERGY STORAGE↗
DOE OSTI2020

A New Class of Ionically Conducting Fluorinated Ether Electrolytes with High Electrochemical Stability

Increasing battery energy density is greatly desired for applications such as portable electronics and transportation. However, many next-generation batteries are limited by electrolyte selection because high ionic conductivity and poor electrochemical stability are typically observed in most electrolytes. For example, ether-based electrolytes have high ionic conductivity but are oxidatively unstable above 4 V, which prevents the use of high-voltage cathodes that promise higher energy densities. In contrast, hydrofluoroethers (HFEs) have high oxidative stability but do not dissolve lithium salt. Here, we synthesize a new class of fluorinated ether electrolytes that combine the oxidative stability of HFEs with the ionic conductivity of ethers in a single compound. We show that conductivities of up to 2.7 × 10 –4 S/cm (at 30 °C) can be obtained with oxidative stability up to 5.6 V. The compounds also show higher lithium transference numbers compared to typical ethers. Furthermore, we use nuclear magnetic resonance (NMR) and molecular dynamics (MD) to study their ionic transport behavior and ion solvation environment, respectively. Finally, we demonstrate that this new class of electrolytes can be used with a Ni-rich layered cathode (NMC 811) to obtain over 100 cycles at a C/5 rate. The design of new molecules with high ionic conductivity and high electrochemical stability is a novel approach for the rational design of next-generation batteries.

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

In-built ultraconformal interphases enable high-safety practical lithium batteries

There is an urgent need for high-safety and high-energy lithium-ion batteries to satisfy the rapidly increasing need for energy storage. Nickel-rich layered cathodes have been at the forefront of the revolution for batteries due to their relatively high capacity and low cost. However, with the increase of nickel content, the batteries suffer from severe safety concerns, which caused by thermal runaway. Herein, we show that the ultraconformal cathode-electrolyte interphase (CEI) protective skin with high inorganic content dramatically enhances the safety of high-energy practical Li-ion pouch cells. We find that the robust CEI skin significantly improves the intrinsic thermal stability, mitigates the evolution of oxygen resulting from phase transition, and effectively suppresses the associated parasitic reactions between the delithiated cathodes and electrolyte. The in-situ CEI engineering strategy is simple and suitable for practical industrial manufacture, and it provides design ideas for aggressive nickel-rich cathodes towards safe and high-energy batteries.

25 ENERGY STORAGE↗
DOE OSTI2021

Location-Dependent Cobalt Deposition in Smartphone Cells upon Long-Term Fast-Charging Visualized by Synchrotron X-ray Fluorescence

In this work, we investigate the transition-metal dissolution of the layered cathode material LiCoO 2 upon repeated fast-charging of three smartphone batteries from different manufacturers using synchrotron micro X-ray fluorescence (μ-XRF). Using this spatially resolved technique, dissolution of Co and subsequent location-dependent deposition on the anode are observed. μ-XRF mapping of selected parts of the anode electrode sheets, such as electrode folds and edges of the jelly roll, reveals the difference in the way Co is deposited on specific regions of the anode electrode. While some folds show no depositions, edges of the anode show gradually accumulating Co depositions. Furthermore, careful quantification of the dissolved Co reveals that the capacity loss scales with the amount of deposited Co on the anode, that is, total Co loss from within the cathode. Soft X-ray absorption spectroscopy of the Co depositions on the anode shows that Co is mainly deposited in a reduced 2 + state. While optimization of the fast-charging protocol mitigates Li plating on the anode, no significant difference in the amount of deposited Co can be observed between an optimized and a nonoptimized fast-charging algorithm.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Direct Imaging of the Structural and Morphological Evolution of Epitaxial LiCoO 2 Films during Charge and Overcharge

The capacity decay of layered cathodes in high-voltage applications underscores the need to utilize accurate and precise techniques to understand the underlying mechanisms. Here, we use well-defined epitaxial LiCoO 2 (LCO) films on SrRuO 3 /SrTiO 3 (SRO/STO) with controlled orientations and defect structures along with in situ electrochemical atomic force microscopy to probe the structural and morphological evolutions during the charge and overcharge processes. We quantitatively show the morphological changes in both the reversible delithiation regime and the irreversible over-delithiation regime and correlate the overall electrochemical behaviors to atomic scale defect evolutions in the films. Further, we also observe a significantly lower charging capacity for LCO/SRO/STO(111) compared to that of LCO/SRO/STO(001) films of the same thickness, which is ascribed to different types of atomic scale defects formed during the film growth process. Our high- resolution scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) studies reveal that the antiphase boundaries in LCO/SRO/STO(111) act as viable channels for Li migration but are more susceptible to irreversible phase transitions, which then block subsequent Li diffusion. The failure mechanisms developed here may provide insight into the design of future cathode materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Solvent-Mediated, Reversible Ternary Graphite Intercalation Compounds for Extreme-Condition Li-Ion Batteries

Traditional Li-ion intercalation chemistry into graphite anode exclusively utilizes the co-intercalation-free or co-intercalation mechanism. The latter mechanism is based on ternary graphite intercalation compounds (t-GICs), where glyme solvents were explored and proved to deliver unsatisfied cyclability in LIBs. Herein, we report a novel intercalation mechanism, that is, in-situ synthesis of t-THF-GICs in the tetrahydrofuran (THF) electrolyte via a spontaneous, controllable reaction between binary-GICs and free THF molecules during initial graphite lithiation. The spontaneous transformation from b-GIC to t-GIC, which is different from conventional co-intercalation chemistry, is characterized and quantified via operando synchrotron X-ray and electrochemical analyses. The resulting t-GIC chemistry obviates the necessity for complete Li-ion desolvation, facilitating rapid kinetics and synchronous charge/discharge of graphite particles even under high current densities. Consequently, the graphite anode demonstrates unprecedented fast charging (1 min), dendrite-free low-temperature performance, and ultralong lifetimes exceeding 10,000 cycles. Full cells coupled with layered cathode, display remarkable cycling stability upon a 15-min charging and excellent rate capability even at -40 °C. Furthermore, our chemical strategies are shown to extend beyond Li-ion batteries to encompass Na-ion and K-ion batteries, underscoring their broad applicability. Our work contributes to the advancement of graphite intercalation chemistry and presents a low-cost, adaptable approach to achieving fast-charging and low-temperature batteries.

25 ENERGY STORAGE↗
DOE OSTI2022

Additive engineering for robust interphases to stabilize high-Ni layered structures at ultra-high voltage of 4.8 V

Nickel-rich layered cathode materials promise high energy density for next-generation batteries when coupled with lithium metal anodes. However, the practical capacities accessible are far less than the theoretical values due to their structural instability during cycling, especially when charged at high voltages. Here we demonstrate that stable cycling with an ultra-high cut-off voltage of 4.8 V can be realized by using an appropriate amount of lithium difluorophosphate in a common commercial electrolyte. The Li||LiNi 0.76 Mn 0.14 Co 0.10 O 2 cell retains 97% of the initial capacity (235 mAh g -1 ) after 200 cycles. The cycling stability is ascribed to the robust interphase on the cathode. It is formed by lithium difluorophosphate decomposition, which is facilitated by the catalytic effect of transition metals. The decomposition products (Li 3 PO 4 and LiF) form a protective interphase. This suppresses transition metal dissolution and cathode surface reconstruction. It also facilitates uniform Li distribution within the cathode, effectively mitigating the strain and crack formation.

25 ENERGY STORAGE↗
DOE OSTI2020

A redox-active organic cation for safer high energy density Li-ion batteries

Ni-rich layered cathode materials are at the forefront to be deployed in high energy density Li-ion batteries for the automotive market. However, the intrinsic poor structural and interfacial stability during overcharging could trigger violent thermal failure, which severely limits their wide application. To protect the Ni-rich cathode from overcharging, we firstly report a redox-active cation, thioether-substituted diaminocyclopropenium, as an electrolyte additive to limit the cell voltage within the safe value during overcharging. The organic cation demonstrates a record-breaking electrochemical reversibility at ~4.55 V versus Li + /Li and solubility (0.5 M) in carbonate-based electrolyte. The protection capability of the additive was explored in two cell chemistries: a LiNi 0.8 Co 0.15 Al 0.05 O 2 /graphite cell and a LiNi 0.8 Co 0.15 Al 0.05 O 2 /silicon–graphene cell with areal capacities of ~2.2 mA h cm -2 and ~3 mA h cm -2 , respectively. With 0.2 M addition, the LiNi 0.8 Co 0.15 Al 0.05 O 2 /graphite cell survived 54 cycles at 0.2C with 100% overcharge. Moreover, the cell can carry an utmost 4.4 mA cm -2 (2C) with 100% overcharge and a maximum capacity of 7540% SOC at 0.2C.

25 ENERGY STORAGE↗
DOE OSTI2026

Revealing short- and long-range Li-ion diffusion in Li 2 MnO 3 from finite-temperature dynamical mean field theory

Li 2 MnO 3 is a key component of Li-excess layered cathodes of the form (1 − x), LiMO 2 + x, Li 2 MnO 3 (M = Mn, Ni, Co, …), yet its role in setting Li-ion transport limitations remains under debate. Here, in this study, we combine DFT+U, finite-temperature DFT+DMFT with a continuous-time quantum Monte Carlo impurity solver, and nudged-elastic-band (NEB) calculations to study Li + migration in paramagnetic Li 2 MnO 3 in the presence of a single Li vacancy. Evaluating DMFT total energies along the DFT+U NEB geometries reveals that dynamical correlations strongly renormalize the lowest-barrier processes, reducing the activation energies to E a = 0.18 eV for the shortest-range hop and E a = 0.50 eV for the next-lowest (transport-controlling) step. The 0.18 eV barrier quantitatively reproduces the short-range activation energy from µ+SR, while the 0.50 eV barrier is consistent with the long-range transport scale extracted from ac-impedance measurements. This single-vacancy, paramagnetic DMFT description thus provides a unified interpretation of local and macroscopic probes without invoking clustered vacancy configurations or strong extrinsic disorder, consistent with nearly stoichiometric Li 2 MnO 3 powders. More broadly, our results highlight finite-temperature dynamical correlations as an essential ingredient for predicting ionic migration energetics in correlated oxide electrodes.

Lee, Alex Taekyung [University of Illinois, Chicag↗
DOE OSTI2025

Revealing the roles of the solid–electrolyte interphase in designing stable, fast-charging, low-temperature Li-ion batteries

Designing the solid–electrolyte interphase (SEI) is critical for stable, fast-charging, low-temperature Li-ion batteries. Fostering a “fluorinated interphase,” SEI enriched with LiF, has become a popular design strategy. Although LiF possesses low Li-ion conductivity, many studies have reported favorable battery performance with fluorinated SEIs. Such a contradiction suggests that optimizing SEI must extend beyond chemical composition design to consider spatial distributions of different chemical species. In this work, we demonstrate that the impact of a fluorinated SEI on battery performance should be evaluated on a case-by-case basis. Sufficiently passivating the anode surface without impeding Li-ion transport is key. We reveal that a fluorinated SEI containing excessive and dense LiF severely impedes Li-ion transport. In contrast, a fluorinated SEI with well-dispersed LiF (i.e., small LiF aggregates well mixed with other SEI components) is advantageous, presumably due to the enhanced Li-ion transport across heterointerfaces between LiF and other SEI components. An electrolyte, 1 M LiPF 6 in 2-methyl tetrahydrofuran (2MeTHF), yields a fluorinated SEI with dispersed LiF. This electrolyte allows anodes of graphite, μSi/graphite composite, and pure Si to all deliver a stable Coulombic efficiency of 99.9% and excellent rate capability at low temperatures. Pouch cells containing layered cathodes also demonstrate impressive cycling stability over 1,000 cycles and exceptional rate capability down to −20 °C. Through experiments and theoretical modeling, we have identified a balanced SEI-based approach that achieves stable, fast-charging, low-temperature Li-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2022

First-principles comparative study of Cr migration in O3 and O/P hybrid-phased NaCrO 2

In layered Na transition-metal (TM) oxides, TM migration usually occurs at highly charged states and severely deteriorates the capacity and reversibility. Meanwhile, the formation of hybrid phases with the intergrowth of octahedral (O-type) and prismatic (P-type) Na layers also takes place at highly charged states. These hybrid phases are often more stable than simple O3 or P3 stackings. However, little is known about the mechanism and impact of TM migration in these hybrid phases. In this work, a comparative first-principles study is performed to understand the connections between structural changes and Cr migration in layered O3 and hybrid-phased NaCrO 2 . After Cr migration, the hybrid-phased NaCrO 2 suffers from greater layer shrinkage than the O3 phase. Three factors affect the Cr migration energy E mig : the Na concentration, local 3D configurations, and 2D in-plane geometries. Low Na concentrations and certain local 3D configurations facilitate the Cr migration. The Cr migration barriers in both O3 and hybrid-phased NaCrO 2 are positively correlated with the Cr E mig . The Cr migration in 17 doped O3 and hybrid-phased NaCrO 2 is surveyed. In these doped NaCrO 2 , a more uniform distribution of the Cr–O bond lengths usually suggests suppressed Cr migration. Optimal dopants for suppressing Cr migration are identified by considering E mig for both Cr and the dopant. Finally, our comparative study on Cr migration in O3 and hybrid-phased NaCrO 2 reveals the significant role of hybrid-phased structures in the development of layered cathode materials.

36 MATERIALS SCIENCE↗
DOE OSTI2025

The Effect of a Carbon Fiber Layer Between the Cathode and the Current Collector on Battery Cell Performance

Contact resistance between the cathode active material (CAM) and the Al current collector can be reduced by applying carbon coatings to the Al current collector surface. However, this process requires an additional step of carbon layer coating on the current collector, which increases both manufacturing costs and processing time. In the present work, an interlayer of continuous unsized carbon fibers aligned in one direction (CF interlayer), is introduced between the Al current collector and the NMC811 cathode during cathode deposition on the Al current collector. This single-step approach eliminates the need for the additional carbon layer coating on the current collector. Additionally, this approach removes the use of toxic solvents and insulative polymers used for making the carbon coating. The CF interlayer improves the rate capability at higher C-rates. The CF interlayer lowers the contact resistance between the cathode particles and the current collector while improving the activation energy of charge transfer. The peel test showed that the CF interlayer does not affect the adhesion strength of the cathode layer with the current collector.

25 ENERGY STORAGE↗
DOE OSTI2023

Asynchronous domain dynamics and equilibration in layered oxide battery cathode

To improve lithium-ion battery technology, it is essential to probe and comprehend the microscopic dynamic processes that occur in a real-world composite electrode under operating conditions. The primary and secondary particles are the structural building blocks of battery cathode electrodes. Their dynamic inconsistency has profound but not well-understood impacts. In this research, we combine operando coherent multi-crystal diffraction and optical microscopy to examine the chemical dynamics in local domains of layered oxide cathode. Our results not only pinpoint the asynchronicity of the lithium (de)intercalation at the sub-particle level, but also reveal sophisticated diffusion kinetics and reaction patterns, involving various localized processes, e.g., chemical onset, reaction front propagation, domains equilibration, particle deformation and motion. These observations shed new lights onto the activation and degradation mechanisms of state-of-the-art battery cathode materials.

25 ENERGY STORAGE↗
DOE OSTI2022

Layered oxide cathode-inspired secondary hard carbon microsphere anode material for high-power and long-life rechargeable batteries

A new anode material that will provide lithium ion (Li-ion) batteries with high energy and power density is urgently needed. In this work, a layered oxide cathode-inspired secondary hard carbon microsphere (CMS) anode material was designed, and exhibited excellent rate performance and long cyclability. Polyacrylonitrile/poly(styrene-co-acrylonitrile) (PAN/SAN) compositions displaying the meatball-like shape of the PAN precursor were carbonized into CMSs having turbostratic microstructures. The CMS carbonized at 1,000°C (CMS1000) displayed high specific capacity at the highest current density of 1,000mAg -1 , i.e., 77.6 % of its average charge capacity at 100 mA g -1 , and considerable cycling retention after 500 cycles, i.e., 83.8 % of the specific capacity at cycle 25. In conclusion, our work demonstrates that the design of new anode materials is a fruitful route to improve commercial Li-ion batteries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Extended Interfacial Stability through Simple Acid Rinsing in a Li-Rich Oxide Cathode Material

Layered Li-rich Ni, Mn, Co (NMC) oxide cathodes in Li-ion batteries provide high specific capacities (>250 mAh/g) via O-redox at high voltages. However, associated high-voltage interfacial degradation processes require strategies for effective electrode surface passivation. Here, we show that an acidic surface treatment of a Li-rich NMC layered oxide cathode material leads to a substantial suppression of CO 2 and O 2 evolution, ~90% and ~100% respectively, during the first charge up to 4.8 V vs. Li +/0 . CO 2 suppression is related to Li 2 CO 3 removal as well as effective surface passivation against electrolyte degradation. This treatment does not result in any loss of discharge capacity and provides superior long-term cycling and rate performance compared to as-received, untreated materials. We also quantify the extent of lattice oxygen participation in charge compensation (“O-redox”) during Li + removal by a novel ex-situ acid titration. Our results indicate that the peroxo-like species resulting from O-redox originate on the surface at least 300 mV earlier than the activation plateau region around 4.5 V. X-ray photoelectron spectra and Mn -L X-ray absorption spectra of the cathode powders reveal a Li + deficiency and a partial reduction of Mn ions on the surface of the acid-treated material. More interestingly, although the irreversible oxygen evolution is greatly suppressed through the surface treatment, our O K-edge resonant inelastic X-ray scattering shows the lattice O-redox behavior largely sustained. The acidic treatment, therefore, only optimizes the surface of the Li-rich material and almost eliminates the irreversible gas evolution, leading to improved cycling and rate performance. This work therefore presents a simple yet effective approach to passivate cathode surfaces against interfacial instabilities during high-voltage battery operation.

25 ENERGY STORAGE↗
DOE OSTI2021

Current Status and Future Directions of All-Solid-State Batteries with Lithium Metal Anodes, Sulfide Electrolytes, and Layered Ternary Oxide Cathodes

All-solid-state batteries (ASSBs) offer great promise as a next-generation energy storage technology with higher energy density, wider operating temperature range, and improved safety for electric vehicles. ASSBs employing lithium metal anodes (Li), sulfide-based solid-state electrolytes (SSE), and Ni-rich layered transition metal oxide cathodes (LiMO 2 , M = Ni, Mn, Co, Al) are particularly promising due to its superior electrochemical performance compared to other solid-electrolyte systems. However, the battery cycle life at high cathode mass loading and high current is still limited because the failure mechanism is not fully understood. Lithium dendrite growth at the anode or inside a solid electrolyte still represents as a serious risk of cell failure. Interfacial resistance increases attributed to electrolyte decomposition and interfacial void formation at both cathode–electrolyte and anode–electrolyte interfaces lead to gradual capacity fading. In this Review, we present the fundamental challenges and recent scientific understandings of each component in ASSBs. The novel diagnostic tools for these components, especially the interfaces buried under the surface that are often hard for characterization are mainly examined. Lastly, we offer a perspective for future research directions. We hope this Review will provide a timely snapshot of state-of-the-art research progress in ASSBs to accelerate the development of ASSBs.

25 ENERGY STORAGE↗