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Results for “Lithiation”

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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Unveiling the Structural Evolution of Ag 1.2 Mn 8 O 16 under Coulombically Controlled (De)Lithiation

MnO 2 materials are considered promising cathode materials for rechargeable lithium, sodium, and magnesium batteries due to their earth abundance and environmental friendliness. One polymorph of MnO 2 , α-MnO 2 , has 2 × 2 tunnels (4.6 Å × 4.6 Å) in its structural framework, which provide facile diffusion pathways for guest ions. In this work, a silver-ion-containing α-MnO 2 (Ag 1.2 Mn 8 O 16 ) is examined as a candidate cathode material for Li based batteries. Electrochemical stability of Ag 1.2 Mn 8 O 16 is investigated through Coulombically controlled reduction under 2 or 4 molar electron equivalents (e.e.). Terminal discharge voltage remains almost constant under 2 e.e. of cycling, whereas it continuously decreases under repetitive reduction by 4 e.e. Thus, detailed structural analyses were utilized to investigate the structural evolution upon lithiation. Significant increases in lattice a (17.7%) and atomic distances (~4.8%) are observed when x in Li x Ag 1.2 Mn 8 O 16 is >4. Ag metal forms at this level of lithiation concomitant with a large structural distortion to the Mn–O framework. In contrast, lattice a only expands by 2.2% and Mn–O/Mn-Mn distances show minor changes (~1.4%) at x < 2. The structural deformation (tunnel breakage) at x > 4 inhibits the recovery of the original structure, leading to poor cycle stability at high lithiation levels. This report establishes the correlation among local structure changes, amorphization processes, formation of Ag 0 , and long-term cycle stability for this silver-containing α-MnO 2 type material at both low and high lithiation levels.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Dynamic imaging of metastable reaction pathways in lithiated cobalt oxide electrodes

Understanding how lithium-ion batteries function down to the atomic level during charge and discharge cycling can provide valuable guidance to optimize structure-property relationships and to design and understand new electrode materials. Lithium insertion and reactions with the electrodes during charge and discharge cycling can occur via metastable structures with complex ordering and related non-equilibrium phenomena. Remarkably, these processes remain still poorly understood despite their significance in the operation of lithium battery systems in critical technologies. In this communication, we present the dynamics of lithium insertion into Co3O4 and the evolution of metastable phases as probed by in-situ transmission electron microscopy, in concert with first principles density functional theory calculations. We show that the initial lithium intercalation reaction occurs with the formation of several metastable and intermediate phases, followed by a sequence of conversion reactions that perturb and expand the cubic-close-packed oxygen array, ultimately generating an end-product of finely dispersed cobalt metal clusters within a Li2O matrix. The calculated non-equilibrium lithiation pathways corroborate with the experimental lithiation voltages, and explain the significant hysteresis that occurs during electrochemical cycling. The data provide new insights into the complexity of solid state lithium electrochemistry in metal oxides that are relevant to advancing lithium battery technology.

conversion reaction electrode↗
DOE OSTI2017

Revealing the Conversion Mechanism of Transition Metal Oxide Electrodes during Lithiation from First-Principles

Transition metal oxides such as Co3O4 and NiO are of significant interest as conversion anode materials for lithium-ion batteries (LIBs), due to their remarkably high theoretical capacities and low cost. While many previous experiments have found that the charge/discharge reactions of Co3O4 and NiO can be highly reversible, detailed information about the mechanisms of these reactions, such as the origin of the voltage hysteresis (>1.0 V) between the charge/discharge cycles, is still poorly understood. In this work, we develop and utilize a new computational mechanistic approach that helps elucidate the hysteresis and nonequilibrium reaction pathways associated with these conversion materials. We apply this methodology to investigate a variety of lithiation reaction pathways of Co3O4 and NiO by systematically exploring the energetics of a large number of equilibrium and nonequilibrium LixCo3O4 (0 ≤ x ≤ 8) and LixNiO (0 ≤ x ≤ 2) structural configurations using first-principles calculations. The overall value of the voltages from our nonequilibrium pathway is in much better agreement with experimental lithiation than the calculated equilibrium voltage while the overall value of the latter reasonably agrees with experimental delithiation. Hence, we propose the charge and discharge processes proceed through equilibrium and nonequilibrium reaction paths, respectively, which contribute significantly to the experimentally observed voltage hysteresis in Co3O4 and NiO. Additionally, we find a low-energy, lithiated intermediate phase (Li3Co3O4) with an oxygen framework equal to that of the initial Co3O4 spinel phase. This intermediate phase represents the capacity threshold below which limited volume expansion and better reversibility can be realized and above which reactions lead to structural degradation and huge expansion.

Yao, Zhenpeng↗
DOE OSTI2018

In Situ Transmission Electron Microscopy of Oxide Shell-Induced Pore Formation in (De)lithiated Silicon Nanowires

Silicon (Si) nanowires with a silicon oxide (SiOx) shell were observed in situ during lithiation and delithiation using transmission electron microscopy (TEM). The oxide shell constrains the volume expansion, which prevents full lithiation of the nanowire and retention of a crystalline Si core. Pores form in the amorphized silicon upon the first delithiation. We propose that this is caused by a high barrier to vacancy migration in the SiOx shell, which prevents vacancies formed during delithiation from transporting through the shell to the nanowire surface. These in situ studies demonstrate the importance of the direct observation of structural changes that occur in a material during cycling upon the addition of a coating.

Adkins, Emily R.↗
DOE OSTI2023

Electrolyte Role in SEI Evolution at Si in the Pre-lithiation Stage vs the Post-lithiation Stage

The formation and evolution of the dynamic solid electrolyte interphase (SEI) at the Si anode/electrolyte interface are yet to be completely understood to solve irreversible capacity loss and increase battery cycle life. Herein, the evolution of SEI and its dynamic properties at the Si anode/electrolyte interface are investigated in two electrolyte systems, a 1.2 M LiPF6 in EC: EMC 3:7 (wt%) electrolyte (referred to as Gen2) and a 1.2 M LiTFSI in EC: EMC 3:7 (wt%) electrolyte (referred to as LiTFSI). Two lithiation stages are studied: the pre-lithiation (pre-Li) SEI stage and the post-lithiation (post-Li) stage. Findings reveal at the pre-Li, SEI formation starts at an early potential and contributes to the greater mass gain in the Si/Gen2, and it is dominated by the formation of a non-uniform F- and P-rich layer in Si/Gen2, in contrast to a homogeneous F- and C-containing layer at the Si/LiTFSI interphase. The initially formed SEI in LiTFSI further benefits the charge transfer kinetics. At the post-Li stage, a more substantial SEI evolution is observed at Si/LiTFSI. This paper offers a foundational understanding of the SEI dynamic evolution with electrolyte dependence. Findings from this report offer important insights into solving the complex SEI stability issues on Si.

25 ENERGY STORAGE↗
DOE OSTI2017

In Situ TEM Investigation of ZnO Nanowires during Sodiation and Lithiation Cycling

The development of sodium-ion batteries has drawn lots of attention recently due to the low-cost and eco-friendly sodium source. However, a fundamental understanding of the sodiation behavior for commonly used electrode materials is still limited. Here, combining in situ transmission electron microscopy, aberration-corrected scanning transmission electron microscopy, and ex situ battery cycling tests, the lithiation and sodiation behavior of ZnO nanowires is investigated. The findings show a direct correlation between the mechanical behavior of the lithiated/sodiated ZnO nanowires and their electrochemical cyclability. The mechanical brittleness of LiZn and the formation of nanocracks lead to the poor cyclability of Li-ion batteries with a ZnO anode. However, the sodiated ZnO nanowires show profuse dislocation plasticity. The observed high-density dislocations offer the sodiated ZnO anode more ductility and subsequently better cyclability than its Li-ion counterpart. The results reveal the importance of understanding the correlation between mechanical properties of battery electrodes and their cycling abilities.

Asayesh-Ardakani, Hasti↗
DOE OSTI2025

Topotactic Phase Transformation of Lithiated Spinel to Layered LiMn0.5Ni0.5O2: The Interaction of 3-D and 2-D Li-ion Diffusion

This study investigates the structural evolution of LiMn0.5Ni0.5O2 cathode materials for Li-ion batteries as a function of synthesis temperature and its effect on electrochemical performance. It is demonstrated that, as the synthesis temperature increases from 400 to 900 ?C, a gradual topotactic transformation occurs between a lithiated spinel structure, denoted herein as “lithium-excess spinel” LxS-LiMn0.5Ni0.5O2 (or LxS-LMNO), and the well-known layered LiMn0.5Ni0.5O2 structure prepared at high temperature, HT-LiMn0.5Ni0.5O2 (HT-LMNO). The electrochemical capacity of the LiMn0.5Ni0.5O2 electrodes follows a parabolic trend with increasing synthesis temperature, which is attributed primarily to the gradual transformation of 3-dimensional (3-D) to 2-dimensional (2-D) diffusion pathways for the Li ions. When synthesized at 400 °C, LxS-LiMn0.5Ni0.5O2 electrodes perform well, benefitting from the 3-D network of channels within the LxS structure. By contrast, when prepared at 500-700 °C, LiMn0.5Ni0.5O2 electrodes operate poorly, which is attributed to the formation of locally disordered structural arrangements that impede Li-ion diffusion. Such an increase in local disorder in the mid-temperature synthesis range is attributed to the structural frustration between the lithium-excess spinal and layered end-members. The transformation from the locally disordered to more ordered layered components between 700 °C and 900 °C enhances electrochemical performance. The study opens new avenues for designing next-generation Mn-rich cathode materials by fine-tuning the synthesis conditions as well as the composition and structure of LxS-LMNO electrodes.

energy storage↗