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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Insight into the Atomic Structure of High-Voltage Spinel LiNi 0.5 Mn 1.5 O 4 Cathode Material in the First Cycle

Application of high-voltage spinel LiNi 0.5 Mn 1.5 O 4 cathode material is the closest and the most realistic approach to meeting the midterm goal of lithium-ion batteries for electric vehicles (EVs) and plug-in hybrid electric vehicles (HEVs). However, this application has been hampered by long-standing issues, such as capacity degradation and poor first-cycle Coulombic efficiency of LiNi 0.5 Mn 1.5 O 4 cathode material. Although it is well-known that the structure of LiNi 0.5 Mn 1.5 O 4 into which Li ions are reversibly intercalated plays a critical role in the above issues, performance degradation related to structural changes, particularly in the first cycle, are not fully understood. Here, we report detailed investigations of local atomic-level and average structure of LiNi 0.5 Mn 1.5 O 4 during first cycle (3.5–4.9 V) at room temperature. We observed two types of local atomic-level migration of transition metals (TM) ions in the cathode of a well-prepared LiNi 0.5 Mn 1.5 O 4 //Li half-cell during first charge via an aberration-corrected scanning transmission electron microscopy (STEM). Surface regions (~2 nm) of the cycled LiNi 0.5 Mn 1.5 O 4 particles show migration of TM ions into tetrahedral Li sites to form a Mn 3 O 4 -like structure. However, subsurface regions of the cycled particles exhibit migration of TM ions into empty octahedral sites to form a rocksalt-like structure. The migration of these TM ions are closely related to dissolution of Ni/Mn ions and building-up of charge transfer impedance, which contribute significantly to the capacity degradation and the poor first-cycle Coulombic efficiency of spinel LiNi 0.5 Mn 1.5 O 4 cathode material. Accordingly, we provide suggestions of effective stabilization of LiNi 0.5 Mn 1.5 O 4 structure to obtain better electrochemical performance.

25 ENERGY STORAGE↗
DOE OSTI2019

Mixed material cathode for secondary alkaline batteries

A secondary alkaline battery using manganese dioxide is described. The battery includes a mixed cathode material with birnessite-phase manganese dioxide or electrolytic manganese dioxide (EMD), a bismuth compound and a copper compound selected from the group consisting of elemental copper and a copper salt. In some embodiments, a conductive carbon and/or a binder may also be included.

25 ENERGY STORAGE↗
DOE OSTI2019

Mixed material cathode for secondary alkaline batteries

A secondary alkaline battery using manganese dioxide is described. The battery includes a mixed cathode material with birnessite-phase manganese dioxide or electrolytic manganese dioxide (EMD), a bismuth compound and a copper compound selected from the group consisting of elemental copper and a copper salt. In some embodiments, a conductive carbon and/or a binder may also be included.

25 ENERGY STORAGE↗
DOE OSTI2016

Unraveling the Complex Delithiation Mechanisms of Olivine-Type Cathode Materials, LiFe x Co 1– x PO 4

The delithiation mechanisms occurring within the olivine-type class of cathode materials for Li-ion batteries have received considerable attention owing to the good capacity retention at high rates for LiFePO4. A comprehensive mechanistic study of the (de)lithiation reactions that occur when the substituted olivine-type cathode materials LiFexCo1-xPO4 (x = 0, 0.05, 0.125, 0.25, 0.5, 0.75, 0.875, 0.95 and 1) are electrochemically cycled is reported here, using in situ X-ray diffraction (XRD) data. On the first charge, two intermediate phases are observed and identified: Li1-x(Fe3+)x(Co2+)1- xPO4 for 0 < x < 1 (i.e. after oxidation of Fe2+ => Fe3+) and Li2/3FexCo1-xPO4 for 0 ≤ x ≤ 0.5 (i.e. the Co-majority materials). For the Fe-rich materials, we study how nonequilibrium, single-phase mechanisms that occur discretely in single particles, as observed for LiFePO4 at high rates, is affected by Co substitution. In the Co-majority materials, a two-phase mechanism with a coherent interface is observed, as was seen in LiCoPO4, and we discuss how it is manifested in the XRD patterns. We then compare the nonequilibrium, single-phase mechanism with the bulk single-phase and the coherent interface two-phase mechanisms. Despite the apparent differences between these mechanisms, we discuss how they are related and interconverted as a function of Fe/Co substitution and the potential implications for the electrochemistry of this system.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Open‐Structured V 2 O 5 · n H 2 O Nanoflakes as Highly Reversible Cathode Material for Monovalent and Multivalent Intercalation Batteries

The high‐capacity cathode material V 2 O 5 · n H 2 O has attracted considerable attention for metal ion batteries due to the multielectron redox reaction during electrochemical processes. It has an expanded layer structure, which can host large ions or multivalent ions. However, structural instability and poor electronic and ionic conductivities greatly handicap its application. Here, in cell tests, self‐assembly V 2 O 5 · n H 2 O nanoflakes shows excellent electrochemical performance with either monovalent or multivalent cation intercalation. They are directly grown on a 3D conductive stainless steel mesh substrate via a simple and green hydrothermal method. Well‐layered nanoflakes are obtained after heat treatment at 300 °C (V 2 O 5 ·0.3H 2 O). Nanoflakes with ultrathin flower petals deliver a stable capacity of 250 mA h g −1 in a Li‐ion cell, 110 mA h g −1 in a Na‐ion cell, and 80 mA h g −1 in an Al‐ion cell in their respective potential ranges (2.0–4.0 V for Li and Na‐ion batteries and 0.1–2.5 V for Al‐ion battery) after 100 cycles.

Wang, Huali↗
DOE OSTI2017

LiMnPO4·Li3V2(PO4)3 composite cathode material derived from Mn(VO3)2 nanosheet precursor

The LiMnPO4·Li3V2(PO4)3/C composite cathode material was synthesized from Mn(VO3)2 nanosheet precursor, which was prepared by a hydrothermal method. The structure and morphology of the composite were systematically investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and scanning transmission electron microscopy (STEM), etc. The LiMnPO4·Li3V2(PO4)3/C composite material exhibits a low polarization and high specific capacity of 150.7 mAh g-1 at 0.1C in voltage range of 2.5–4.5V, and excellent cycle and rate performance for its stable nanocomposite framework. The composite material dominantly exists in the morphological shape of nanograins and nanorods, which increases the surface area and hence facilitate the electrolyte penetration. The nanoparticle components were even further identified in detail.

Lei, Zhihong↗
DOE OSTI2018

Nucleation of dislocations and their dynamics in layered oxide cathode materials during battery charging

Lithium-rich layered oxides (LRLO) are among the leading candidates for the next-generation cathode material for energy storage, delivering 50% excess capacity over commercially used compounds. Despite excellent prospects, voltage fade has prevented effective use of the excess capacity, and a major challenge has been a lack of understanding of the mechanisms underpinning the voltage fade. Here, using operando three-dimensional Bragg coherent diffractive imaging, we directly observe the nucleation of a mobile dislocation network in LRLO nanoparticles. The dislocations form more readily in LRLO as compared with a classical layered oxide, suggesting a link between the defects and voltage fade. We show microscopically how the formation of partial dislocations contributes to the voltage fade. The insights allow us to design and demonstrate an effective method to recover the original high-voltage functionality. Furthermore, our findings reveal that the voltage fade in LRLO is reversible and call for new paradigms for improved design of oxygen-redox active materials.

25 ENERGY STORAGE↗
DOE OSTI2014

Functioning Mechanism of AlF 3 Coating on the Li- and Mn-Rich Cathode Materials

We report systematic studies of the microstructural changes of uncoated and AlF3-coated Li-rich Mn-rich (LMR) cathode materials (Li1.2Ni0.15Co0.10Mn0.55O2) before and after cycling using a combination of aberration-corrected scanning/transmission electron microscopy (S/TEM) and electron energy loss spectroscopy (EELS). TEM coupled with EELS provides detailed information about the crystallographic and electronic structure changes that occur after cycling, thus revealing the fundamental improvement mechanism of surface coating. The results demonstrate that the surface coating reduces oxidation of the electrolyte at high voltage, suppressing the accumulation of a thick solid electrolyte interface (SEI) layer on electrode particle surface. Surface coating significantly enhances the stability of the surface structure and protects the electrode from severe etching/corrosion by the acidic species in the electrolyte, reducing the formation of etched surfaces and corrosion pits. Moreover, surface coating alleviates the undesirable voltage fade by mitigating layered to spinel-like phase transformation in the bulk region of the material. These fundamental findings may also be widely applied to explain the functioning mechanisms of other surface coatings used in a broad range of electrode materials.

Zheng, Jianming↗
DOE OSTI2016

Structural integrity--Searching the key factor to suppress the voltage fade of Li-rich layered cathode materials through 3D X-ray imaging and spectroscopy techniques

Li-rich layered materials are important cathode compounds used in commercial lithium ion batteries, which, however, suffers from some drawbacks including the so-called voltage fade upon electrochemical cycling. Here, our study employs novel transmission X-ray microscopy to investigate the electrochemical reaction induced morphological and chemical changes in the Li-rich Li 2 Ru 0.5 Mn 0.5 O 3 cathode particles at the meso to nano scale. We performed combined X-ray spectroscopy, diffraction and microscopy experiments to systematically study this cathode material's evolution upon cycling as well as to establish a comprehensive understanding of the structural origin of capacity fade through 2D and 3D fine length scale morphology and heterogeneity change of this material. This work suggests that atomic manipulation (e.g. doping, substitution etc.) or nano engineering (e.g. nano-sizing, heterogeneous structure) are important strategies to mitigate the internal strain and defects induced by extensive lithium insertion/extraction. It also shows that maintaining the structural integrity is the key in designing and synthesizing lithium-rich layered materials with better cycle stability.

25 ENERGY STORAGE↗
DOE OSTI2019

High capacity and stable cathode materials

High energy density cathode materials, such as LiNiXMnYCoZO2 (NMC) cathode materials, with improved discharge capacity (hence energy density) and enhanced cycle life are described. A solid electrolyte, such as lithium phosphate infused inside of secondary particles of the cathode material demonstrates significantly enhanced structural integrity without significant or without any observable particle cracking occurring during charge/discharge processes, showing high capacity retention of more than 90% after 200 cycles at room temperature. In certain embodiments the disclosed cathode materials (and cathodes made therefrom) are formed using nickel-rich NMC and/or are used in a battery system with a non-aqueous dual-Li salt electrolytes.

25 ENERGY STORAGE↗