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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

A Cobalt– and Manganese–Free High–Nickel Layered Oxide Cathode for Long–Life, Safer Lithium–Ion Batteries

High-nickel LiNi 1–x–y Mn x Co y O 2 and LiNi 1–x–y Co x Al y O 2 cathodes are receiving growing attention due to the burgeoning demands on high-energy-density lithium-ion batteries. The presence of both cobalt and manganese in them, however, triggers multiple issues, including high cost, high toxicity, rapid surface deterioration, and severe transition-metal dissolution. Herein, a Co- and Mn-free ultrahigh-nickel LiNi 0.93 Al 0.05 Ti 0.01 Mg 0.01 O 2 (NATM) cathode that exhibits 82% capacity retention over 800 deep cycles in full cells, outperforming two representative high-Ni cathodes LiNi 0.94 Co 0.06 O 2 (NC, 52%) and LiNi 0.90 Mn 0.05 Co 0.05 O 2 (NMC, 60%) is presented. It is demonstrated that a titanium-enriched surface along with aluminum and magnesium as the stabilizing ions in NATM not only ameliorates unwanted side reactions with the electrolyte and structural disintegrity, but also mitigates transition-metal dissolution and active lithium loss on the graphite anode. As a result, the graphite anode paired with NATM displays an ultrathin (≈8 nm), monolayer anode-electrolyte interphase architecture after extensive cycling. Furthermore, NATM displays considerably enhanced thermal stability with an elevated exothermic temperature (213 °C for NATM vs 180 and 190 °C for NC and NMC, respectively) and remarkably reduced heat release. This work sheds light on rational compositional design to adopt ultrahigh-Ni cathodes in lithium-based batteries with low cost, long service life, and improved thermal stability.

25 ENERGY STORAGE↗
DOE OSTI2018

Effect of Calcination Temperature on the Electrochemical Properties of Nickel-rich LiNi0.76Mn0.14Co0.10O2 Cathodes for Lithium-ion Batteries

High energy density nickel (Ni)-rich layered LiNixMnyCozO2 (NMC, x = 0.6) materials are promising cathodes for lithium-ion batteries. However, several technical challenges, such as fast capacity fading, are hampering their large scale application. Herein, we demonstrate that a Ni-rich cathode LiNi0.76Mn0.14Co0.10O2 (NMC76) calcined at an optimal temperature of 750~775oC exhibits a high discharge capacity (~215 mAh g-1 when charged to 4.5 V) and an excellent high rate capability. Even at a 10C rate, it still exhibits a capacity of more than 160 mAh g-1 and retains ca. 79% of its initial capacity after 200 cycles. The high performance of NMC76 is directly related to its optimized primary particle size (that constitute the spherical secondary particles of >10 m) and cation mixing. Higher calcination temperature (= 800 oC) leads to rapid increase of primary particle size, poor cycling stability, and inferior rate capability of NMC76 due to its severe micro strain and crack formation upon repeated lithium ion de/intercalations. Therefore, NMC76 calcined at 750~775oC is a very good candidate for the next generation of Li ion batteries.

nickel-rich cathodes, calcination temperature, cyc↗
DOE OSTI2018

A New Strategy for High-Voltage Cathodes for K-Ion Batteries: Stoichiometric KVPO 4 F

The exploration of high-energy-density cathode materials is crucial to the practical use of K-ion batteries. Layered K-metal oxides have too high a voltage slope due to their large K + –K + interaction, resulting in low specific capacity and average voltage. In contrast, the 3D arrangement of K + , with polyanions separating them, reduces the strength of the effective K + -K + repulsion, which in turn increases specific capacity and voltage. Here, stoichiometric KVPO 4 F for use as a high-energy-density K-ion cathode is developed. The KVPO 4 F cathode delivers a reversible capacity of ≈105 mAh g -1 with an average voltage of ≈4.3 V (vs K/K + ), resulting in a gravimetric energy density of ≈450 Wh kg -1 . During electrochemical cycling, the K x VPO 4 F cathode goes through various intermediate phases at x = 0.75, 0.625, and 0.5 upon K extraction and reinsertion, as determined by ex situ X-ray diffraction characterization and ab initio calculations. Moreover, our research explains the role of oxygen substitution in KVPO 4+ x F 1- x : the oxygenation of KVPO 4 F leads to an anion-disordered structure which prevents the formation of K + /vacancy orderings without electrochemical plateaus and hence to a smoother voltage profile.

25 ENERGY STORAGE↗
DOE OSTI2022

Consolidation of composite cathodes with NCM and sulfide solid-state electrolytes by hot pressing for all-solid-state Li metal batteries

In this study, hot pressing was evaluated as a method of cell fabrication to increase the energy density of next-generation all-solid-state batteries with NCM active material and sulfide solid-state electrolyte. Hot pressing involves consolidating glassy sulfide electrolyte by the application of pressure at a temperature above the electrolyte’s glass transition temperature. Typically, cell stacks are formed at room temperature and retain 15–30% porosity that limits cell energy density. On the other hand, the porosity of hot-pressed cell stacks is reduced to less than 10%. The electrochemical function of hot-pressed cathode composites was assessed as a function of active material and solid-state electrolyte compositions. Specifically, LiNi 0.85 Co 0.10 Mn 0.05 O 2 and LiNi 0.6 Co 0.2 Mn 0.2 O 2 were studied in combination with either glassy Li 7 P 3 S 11 , glassy Li 3 PS 4 , or β-Li 3 PS 4 solid-state electrolytes. Cathode composites composed of LiNi 0.6 Co 0.2 Mn 0.2 O 2 and Li 3 PS 4 maintained the best function after hot pressing at 200 °C and 370 MPa for 10 min. It was found that LiNi 0.6 Co 0.2 Mn 0.2 O 2 ’s resistance to microcracking and the inherent stability of Li 3 PS 4 ’s fully de-networked local structure are critical to maintain good electrochemical function after hot pressing. Furthermore, the results of this study show that hot pressing reduces porosity in the cathode composite and confirms the feasibility of cathode support of consolidated, reinforced glass separators.

25 ENERGY STORAGE↗
DOE OSTI2017

Direct Investigation of Mg Intercalation into the Orthorhombic V 2 O 5 Cathode Using Atomic-Resolution Transmission Electron Microscopy [Direct Investigation of Mg intercalation into orthorhombic V 2 O 5 cathode using Atomic Resolution Electron Microscopy Methods]

Batteries based on Mg metal anode can promise much higher specific volumetric capacity and energy density compared to Li-ion systems and are, at the same time, safer and more cost-effective. While previous experimental reports have claimed reversible Mg intercalation into beyond Chevrel phase cathodes, they provide limited evidence of true Mg intercalation other than electrochemical data. Transmission electron microscopy techniques provide unique capabilities to directly image Mg intercalation and quantify the redox reaction within the cathode material. Here, we present a systematic study of Mg insertion into orthorhombic V 2 O 5 , combining aberration-corrected scanning transmission electron microscopy (STEM) imaging, electron energy-loss spectroscopy (EELS), and energy-dispersive X-ray spectroscopy (EDX) analysis. We compare the results from an electrochemically cycled V 2 O 5 cathode in a prospective full cell with Mg metal anode with a chemically synthesized MgV 2 O 5 sample. Results suggest that the electrochemically cycled orthorhombic V 2 O 5 cathode shows a local formation of the theoretically predicted ϵ-Mg 0.5 V 2 O 5 phase; however, the intercalation levels of Mg are lower than predicted. Lastly, this phase is different from the chemically synthesized sample, which is found to represent the δ-MgV 2 O 5 phase.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Facilitating the Operation of Lithium-Ion Cells with High-Nickel Layered Oxide Cathodes with a Small Dose of Aluminum

Layered oxide cathodes with a high Ni content of >0.6 are promising for high-energy-density lithium-ion batteries. However, parasitic electrolyte oxidation of the charged cathode and mechanical degradation arising from phase transitions significantly deteriorate the cell performance and cycle life as the Ni content increases. Here we demonstrate here a significantly prolonged cycle life with superior cell performance by substituting a small-dose of Al (2 mol %) for Ni in LiNi 0.92 Co 0.06 Al 0.02 O 2 ; the capacity retention after operating a full cell fabricated with graphite anode for 1000 cycles increases from 47% to 83% on going from the Al-free LiNi 0.94 Co 0.06 O 2 to the Al-doped LiNi 0.92 Co 0.06 Al 0.02 O 2 cathode. Through in situ X-ray diffraction, we provide the operando evidence that the Al-doping tunes the H2–H3 phase transition process from a two-phase reaction to a quasi-monophase reaction, minimizing the mechanical degradation. Furthermore, secondary-ion mass spectrometry reveals considerably suppressed transition-metal dissolution with Al-doping, effectively preventing sustained parasitic reactions and active Li trapping due to chemical crossover on graphite anodes. This work offers a viable approach for adopting high-Ni cathodes in lithium-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2022

Li 8 MnO 6 : A Novel Cathode Material with Only Anionic Redox

In Li-excess transition-metal-oxide cathode materials, anionic oxygen redox can offer high capacity and high voltages, although peroxo and superoxo species may cause oxygen loss, poor cycling performance, and capacity fading. Previous work showed that undesirable formation of peroxide and superoxide bonds is controlled to some extent by Mn substitution, and the present work uses density functional calculations to examine the reasons for this by studying the anionic redox mechanism Li 8 MnO 6 . This material is obtained by substituting Mn for Sn in Li 8 SnO 6 or for Zr in Li 8 ZrO 6 , and we also compare to previous work on those materials. The calculations predict that Li 8 MnO 6 is stable at room temperature (with a band gap of 3.19 eV as calculated HSE06 and 1.82 eV as calculated with the less reliable with PBE+U), and they elucidate the chemical and structural effects involved in the inhibition of oxygen release in this cathode. Throughout the whole delithiation process, only O 2- ions are oxidized. The directional Mn-O bonds formed from unfilled 3d orbitals effectively inhibit the formation of O-O bonds, and the layered structure is maintained even after removing 3 Li per Li 8 MnO 6 formula unit. The calculated average voltage for removal of 3 Li is 3.69 V by HSE06, and the corresponding capacity is 389 mAh/g. The high voltage of oxygen anionic redox and the high capacity result in a high energy density of 1436 Wh/kg. The Li-ion diffusion barrier for the dominant interlayer diffusion path along the c-axis is 0.57 eV by PBE+U. Finally, these results help us to understand the oxygen redox mechanism in a new lithium-rich Li 8 MnO 6 cathode material and contribute to the design of high-energy-density lithium-ion-battery cathode materials with favorable electrochemical properties based on anionic oxygen redox.

Li8MnO6↗
DOE OSTI2022

Effect of Electrolytes on the Cathode-Electrolyte Interfacial Stability of Fe-Based Layered Cathodes for Sodium-Ion Batteries

Iron (Fe)-based layered oxide cathodes that employ Fe 3+ /Fe 4+ redox reaction present a family of attractive cathode materials for sodium-ion batteries as iron is abundant, low-cost, and environmentally benign. However, their electrochemical performance is not yet satisfactory and requires further improvement. In this study, we investigate the effect of electrolytes on the electrochemical performance of α -NaFeO 2 , a prototypical model of Fe-based layered cathodes. First, we established the critical impact of the poor cathode-electrolyte interfacial stability on cell performances. Systematic electrochemical tests and material characterizations further revealed the degradation mechanism in which the highly reactive Fe 4+ state in the charged Na 1−x FeO 2 electrodes promotes severe electrolyte decomposition and subsequent growth of a thick interface layer that leads to impedance rise and performance degradation. In addition, the superior performance of NaPF 6 over NaClO 4 and the beneficial effect of the FEC additive are reported.

25 ENERGY STORAGE↗
DOE OSTI2020

High–Nickel NMA: A Cobalt–Free Alternative to NMC and NCA Cathodes for Lithium–Ion Batteries

High-nickel LiNi 1–x–y Mn x Co y O 2 (NMC) and LiNi 1–x–y Co x Al y O 2 (NCA) are the cathode materials of choice for next-generation high-energy lithium-ion batteries. Both NMC and NCA contain cobalt, an expensive and scarce metal generally believed to be essential for their electrochemical performance. Herein, a high-Ni LiNi 1–x–y Mn x Al y O 2 (NMA) cathode of desirable electrochemical properties is demonstrated benchmarked against NMC, NCA, and Al–Mg-codoped NMC (NMCAM) of identical Ni content (89 mol%) synthesized in-house. Despite a slightly lower specific capacity, high-Ni NMA operates at a higher voltage by ≈40 mV and shows no compromise in rate capability relative to NMC and NCA. In pouch cells paired with graphite, high-Ni NMA outperforms both NMC and NCA and only slightly trails NMCAM and a commercial cathode after 1000 deep cycles. Further, the superior thermal stability of NMA to NMC, NCA, and NMCAM is shown using differential scanning calorimetry. Here, considering the flexibility in compositional tuning and immediate synthesis scalability of high-Ni NMA very similar to NCA and NMC, this study opens a new space for cathode material development for next-generation high-energy, cobalt-free Li-ion batteries.

25 ENERGY STORAGE↗
DOE OSTI2016

In Situ Probing and Synthetic Control of Cationic Ordering in Ni-Rich Layered Oxide Cathodes

Ni-rich layered oxides (LiNi1-xMxO2; M = Co, Mn, ...) are appealing alternatives to conventional LiCoO2 as cathodes in Li-ion batteries for automobile and other large-scale applications due to their high theoretical capacity and low cost. However, preparing stoichiometric LiNi1-xMxO2 with ordered layer structure and high reversible capacity, has proven difficult due to cation mixing in octahedral sites. Herein, in situ studies of synthesis reactions and the associated structural ordering in preparing LiNiO2 and the Co-substituted variant, LiNi0.8Co0.2O2, are made, to gain insights into synthetic control of the structure and electrochemical properties of Ni-rich layered oxides. Results from this study indicate a direct transformation of the intermediate from the rock salt structure into hexagonal phase, and during the process, Co substitution facilities the nucleation of a Co-rich layered phase at low temperatures and subsequent growth and stabilization of solid solution Li(Ni, Co)O-2 upon further heat treatment. Optimal conditions are identified from the in situ studies and utilized to obtain stoichiometric LiNi0.8Co0.2O2 that exhibits high capacity (up to 200 mA h g(-1) ) with excellent retention. The findings shed light on designing high performance Ni-rich layered oxide cathodes through synthetic control of the structural ordering in the materials.

Zhao, Jianqing↗
DOE OSTI2018

KVOPO 4 : A New High Capacity Multielectron Na-Ion Battery Cathode

Sodium ion batteries have attracted much attention in recent years, due to the higher abundance and lower cost of sodium, as an alternative to lithium ion batteries. However, a major challenge is their lower energy density. In this work, we report a novel multi–electron cathode material, KVOPO4, for sodium ion batteries. Due to the unique polyhedral framework, the V 3+ ↔ V 4+ ↔ V 5+ redox couple was for the first time fully activated by sodium ions in a vanadyl phosphate phase. The KVOPO 4 based cathode delivered reversible multiple sodium (i.e. maximum 1.66 Na + per formula unit) storage capability, which leads to a high specific capacity of 235 Ah kg –1 . Combining an average voltage of 2.56 V vs. Na/Na+, a high practical energy density of over 600 Wh kg –1 was achieved, the highest yet reported for any sodium cathode material. The cathode exhibits a very small volume change upon cycling (1.4% for 0.64 sodium and 8.0% for 1.66 sodium ions). In conclusion, density functional theory (DFT) calculations indicate that the KVOPO4 framework is a 3D ionic conductor with a reasonably, low Na + migration energy barrier of ≈450 meV, in line with the good rate capability obtained.

25 ENERGY STORAGE↗
DOE OSTI2018

Direct Visualization of Li Dendrite Effect on LiCoO 2 Cathode by In Situ TEM

Li dendrites are known to cause deterious, and in many cases catastrophic, effect on the performance of Li rechargeable batteries. However, the mechanistic failure mechanism of cathodes upon in contact with Li metal is far from clear. In this study, using in situ transmission electron microscopy, we directly visualize at an atomic scale the interaction of Li dendrites with well-defined, epitaxial thin films of LiCoO2, the most widely used cathode material. We show that a spontaneous and prompt chemical reaction is trigged once the Li contact is made, leading to expansion and amorphization of the LiCoO2 structure, with Li2O and Co metal being the final reaction products. A topotactic phase transition is identified close to the reaction front, resulting in the formation of CoO as a metastable intermediate. Dynamic structural and chemical imaging in combination with ab inito simulations reveal that a high density of antiphase grain boundaries are formed at the reaction front, which are critical for enabling the short-range topotactic reactions and long-range Li propagation. The fundamental insights are of general importance in mitigating Li dendrites related issues and guiding the design principle for more robust energy materials.

In situ transmission electron microscopy (TEM), Li↗
DOE OSTI2017

Suppressed oxygen extraction and degradation of LiNixMnyCozO2 cathodes at high charge cut-off voltages

The capacity degradation mechanism in lithium nickel-manganese-cobalt oxide (NMC) cathodes (LiNi1/3Mn1/3Co1/3O2 (NMC333) and LiNi0.4Mn0.4Co0.2O2 (NMC442)) during high-voltage (cut-off of 4.8 V) operation has been investigated. In contrast to NMC442, NMC333 exhibits rapid structural changes including severe micro-crack formation and phase transformation from a layered to a disordered rock-salt structure, as well as interfacial degradation during high-voltage cycling, leading to a rapid increase of the electrode resistance and fast capacity decline. The fundamental reason behind the poor structural and interfacial stability of NMC333 was found to be correlated to its high Co content and the significant overlap between the Co3+/4+ t(2g) and O2- 2p bands, resulting in oxygen removal and consequent structural changes at high voltages. In addition, oxidation of the electrolyte solvents by the extracted oxygen species generates acidic species, which then attack the electrode surface and form highly resistive LiF. These findings highlight that both the structural and interfacial stability should be taken into account when tailoring cathode materials for high voltage battery systems

Environmental Molecular Sciences Laboratory↗
DOE OSTI2021

Mesoporous Textured Fe-N-C Electrocatalysts as Highly Efficient Cathodes for Proton Exchange Membrane Fuel Cells

A new platinum group metal (PGM)-free proton exchange membrane fuel cell (PEMFC) cathode catalyst materials, synthesized using the VariPore™ method by Pajarito Powder, LLC, are characterized for their structure and activity. The physico-chemical analysis of the iron-nitrogen-carbon (Fe-N-C) electrocatalysts show mesoporous carbon material effectively doped with iron and nitrogen. The materials have an average pore size of 7-8 nm and high specific surface area. The Fe-N-C catalysts exhibit good oxygen reduction reaction (ORR) activity in 0.5 M H2SO4 electrolyte with high half-wave potential and sustainable electrochemical stability over 10,000 repeated potential cycles with insignificant losses in their activities. As cathode catalysts in a PEMFC, the Fe-N-C materials deliver remarkably good fuel cell performance at low overpotential approaching that of the commercial Pt catalyst. The high ORR electrocatalytic activity of these Fe-N-C catalysts is credited to the synergy between nitrogen-moieties, specifically pyrrolic-N, pyridinic-N, and graphitic-N, and iron in addition to the high mesoporosity that facilitate an effective reaction path in boosting the electrocatalytic activity and stability.

DIRECT ENERGY CONVERSION↗