Compositional Change of Surface Film Deposited on LiNi0.5Mn1.5O4Positive Electrode

Yoon, Taeho; Kim, Daesoo; Park, Kern Ho; Park, Hosang; Jurng, Sunhyung; Jang, Jihyun; Ryu, Ji Heon; Kim, Jae Jeong; Oh, Seung M.

doi:10.1149/2.019404jes

Cited by 33 publications

(62 citation statements)

References 36 publications

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“…For example, the commonly used electrolyte salt LiPF 6 degrades, giving rise either to LiF or, in presence of water, HF [2,3] . Similarly, the PVDF can form either LiF, after reacting with lithium ( reaction 1 ), [4,5] or generate HF ( reaction 2 ), [6] as described in the two following reactions:

true Li + - [CH_{2} - CF_{2}] - \to - [CH = CF] - + boldL boldi boldF + 1 / 2 normalH_{2}

true - [CH_{2} - CF_{2}] - \to - [CH = CF] - + boldH boldF

…”

Section: Introductionmentioning

confidence: 99%

Instability of PVDF Binder in the LiFePO₄versus Li₄Ti₅O₁₂ Li‐Ion Battery Cell

Leanza

Vaz

Novák

et al. 2020

Helvetica Chimica Acta

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This manuscript is dedicated to Professor Antonio Togni on the occasion of his retirement The conventional formulation of electrodes used in Li-ion batteries consists of a mixture of three components: an active material, a conductive additive (carbon), and an organic binder. While the first encompasses a broad spectrum of chemistries, the carbon and the binder are often standard elements of the composite, with the latter being, in most of the cathode cases, the polyvinylidene fluoride (PVDF). The high (electro-)chemical inertia spanning over a broad range of oxidative and reductive potentials gives grounds for this choice. Herein, we demonstrate, contrary to electrochemical expectations, that the PVDF is electrochemically unstable at relatively low potentials. We consider in this study the LiFePO 4 (LFP) cathode cycled versus Li 4 Ti 5 O 12 (LTO) anode as a representative low-voltage battery cell system. The binder degradation process starts upon charge on the LFP electrode at 3.45 V vs. Li + /Li when the PVDF binder reacts with lithium and forms LiF. The latter does not precipitate on the LFP but migrates/diffuses towards the LTO counter-electrode, following the Li-ions' trajectory. X-Ray photoelectron spectroscopy complemented with the high lateral resolution of X-ray photoemission electron microscopy disclosed the formation of a thin layer of LiF homogenously distributed across the LTO electrode, which partially dissolves (or decomposes) upon discharge. The degradation of the PVDF and the deposition and dissolution (and/or decomposition) of the LiF layer continue over subsequent charge and discharge cycles. The process is augmented when the cycling temperature is increased to 80°C. The results shown in this work are crucial to interpret electrochemical data, such as specific charge decay or impedance rise, and have relevance for all PVDF-based electrodes, especially when employed in high-voltage battery cells where the more extreme cycling conditions exacerbate electrode components' stability.

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true Li + - [CH_{2} - CF_{2}] - \to - [CH = CF] - + boldL boldi boldF + 1 / 2 normalH_{2}

true - [CH_{2} - CF_{2}] - \to - [CH = CF] - + boldH boldF

…”

Section: Introductionmentioning

confidence: 99%

Instability of PVDF Binder in the LiFePO₄versus Li₄Ti₅O₁₂ Li‐Ion Battery Cell

Leanza

Vaz

Novák

et al. 2020

Helvetica Chimica Acta

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“…The existence of liquid electrolyte decomposition products, forming very thin SEI (sometimes called cathode electrolyte interphase or CEI) films on the cathode, has been amply demonstrated. 2, [22][23][24][25] The overall speciation of electrolyte decomposition products have been reported, [27][28][29] but elucidation of the atomic structure and chemistry of the active material/SEI interface, expected to be most relevant to Mn dissolution, remains a challenge. The composition of surface films is likely not static but depends on charge/discharge conditions.…”

Section: Introductionmentioning

confidence: 99%

First-Principles Modeling of Mn(II) Migration above and Dissolution from Li_xMn₂O₄ (001) Surfaces

2016

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Density functional theory and ab initio molecular dynamics simulations are applied to investigate the migration of Mn(II) ions to above-surface sites on spinel Li x Mn 2 O 4 (001) surfaces, the subsequent Mn dissolution into the organic liquid electrolyte, and the detrimental effects on graphite anode solid electrolyte interphase (SEI) passivating films after Mn(II) ions diffuse through the separator. The dissolution mechanism proves complex; the much-quoted Hunter disproportionation of Mn(III) to form Mn(II) is far from sufficient. Key steps that facilitate Mn(II) loss include concerted liquid/solid-state motions; proton-induced weakening of Mn-O bonds forming mobile OH − surface groups; and chemical reactions of adsorbed decomposed organic fragments. Mn(II) lodged between the inorganic Li 2 CO 3 and organic lithium ethylene dicarbonate (LEDC) anode SEI components facilitates electrochemical reduction and decomposition of LEDC. These findings help inform future design of protective coatings, electrolytes, additives, and interfaces. keywords: lithium ion batteries; lithium manganese oxide; solid electrolyte interface; ab initio molecule dynamics; computational electrochemistry

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“…The capacity fade is generally explained by the loss of active particles that are disconnected from the C/PVdF network as a consequence of formation of thick insulating surface films at contact spots between C and LNMO and/or C degradation. [9][10][11][12][13][14][15][16][17][18] The discharge capacity versus cycle number for LNMO/Li cells is shown in Figs. 4c-4e, for electrodes M1 to M4 prepared by magnetic stirring and LNMO loadings of 7-8 mg cm −2 (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…The charge/discharge reaction becomes sluggish due to polarization increase, which eventually leads to capacity fading. 14 Only a very few reports, however, were focused on the influence of the formulation of the composite electrode (binder and conductive additive content, calendaring, active mass loading) on the cyclability of LNMO. High operating voltages also lead to parasitic reactions with inactive components of the cell such as the carbon conductive additives, the metallic parts of the can and the separator.…”

mentioning

confidence: 99%

“…z E-mail: bernard.lestriez@cnrs-imn.fr degradation products at the surface of the active mass, the degradation of the carbon conductive additive with the loss of LNMO/CB electrical contacts, all lead to an increase of the polarization and, hence, loss of active mass utilization. 14 Vidal et al evaluated the influence of sonication and densification on the rate performance of electrode with active mass loading up to 17 mg/cm 2 . 19 Except the study of Vidal et al, all other works were focused on much lower active mass loadings (e.g.…”

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confidence: 99%

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Manufacturing of LiNi_0.5Mn_1.5O₄Positive Composite Electrodes with Industry-Relevant Surface Capacities for Lithium Ion-Cells

Nguyen

Mariage

Fredon

et al. 2015

J. Electrochem. Soc.

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Influence of the electrode formulation on the cyclability of LiNi 0.5 Mn 1.5 O 4 was studied for industry-relevant surface capacities (i.e. up to ∼3 mAh cm −2 ) with two mixing methods at the lab scale: ball milling and magnetic stirring. The inactive binder and carbon additives content were varied, as well as the type of those. A more homogeneous distribution of additives is observed in ball milled electrodes compared to stirred ones. The cycle life of the former is degraded with lower coulombic efficiency at first cycle, as a consequence of higher specific surface area of the electrodes and increased parasitic reactions. The coulombic efficiency stabilizes at 99.25% after several cycles, irrespective of the electrode formulation used. The fading of the capacity is minimized by increasing the amount of conductive additives or by substituting part of carbon black for carbon nanofibers. However, the cyclability of the electrodes with high active mass loading is severely decreased. The best result found is capacity retention of 85% after 300 cycles. The electrodes prepared in water with carboxylmethyl cellulose (CMC) exhibit poorer cyclability compared to the ones prepared in N-Methylpyrrolidone (NMP) with Polyvinylidene Fluorine (PVdF). Finally, electrodes with optimized formulation was prepared at the pilot scale and evaluated. LiNi 0.5 Mn 1.5 O 4 (LNMO) shows very good structural stability upon cycling. 1-7 As a positive electrode active material, its large reversible capacity of ca 135 mAh/g and high working voltage results in higher specific energy than that of LiFePO 4 , undoped-LiMn 2 O 4 and LiCoO 2 . Moreover, LNMO can be a high rate electrode material even in the form of micron-size particles. 8 This material is thus envisioned for electric vehicles as it meets the performance/cost requirements needed. Its advantages are, however, largely counter-balanced by the instability of several of the cell constituents at the high working voltage of this positive electrode, which is beyond the thermodynamic stability window of common organic electrolytes. As a consequence, parasitic reactions occur at the surface of the active material with the electrolyte that decompose and form surface films deposit including lithium salts and organic carbonates. 9 As a result, large irreversible capacity at the first cycle and low coulombic efficiency (CE) are usually observed for LNMO with conventional electrolytes, which prohibit the use of LNMO for electric vehicle application. 10 Through accurate measurements, Dahn and co-workers showed the CE decreases proportionally to the increase in charge-discharge cycle time indicating that parasitic reactions at the positive electrode occur at a fixed rate at a given temperature. It was found that for LNMO-based cells, time and temperature, and not the cycle number, determine the parasitic reactions and the calendar life. 11 In that regard, the influence of the particle size has been studied, in general by varying the temperature of the material's synthesis. 9-13 The observed trend sh...

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Compositional Change of Surface Film Deposited on LiNi_0.5Mn_1.5O₄Positive Electrode

Cited by 33 publications

References 36 publications

Instability of PVDF Binder in the LiFePO₄versus Li₄Ti₅O₁₂ Li‐Ion Battery Cell

Instability of PVDF Binder in the LiFePO₄versus Li₄Ti₅O₁₂ Li‐Ion Battery Cell

First-Principles Modeling of Mn(II) Migration above and Dissolution from Li_xMn₂O₄ (001) Surfaces

Manufacturing of LiNi_0.5Mn_1.5O₄Positive Composite Electrodes with Industry-Relevant Surface Capacities for Lithium Ion-Cells

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Compositional Change of Surface Film Deposited on LiNi0.5Mn1.5O4Positive Electrode

Cited by 33 publications

References 36 publications

Instability of PVDF Binder in the LiFePO4versus Li4Ti5O12 Li‐Ion Battery Cell

Instability of PVDF Binder in the LiFePO4versus Li4Ti5O12 Li‐Ion Battery Cell

First-Principles Modeling of Mn(II) Migration above and Dissolution from LixMn2O4 (001) Surfaces

Manufacturing of LiNi0.5Mn1.5O4Positive Composite Electrodes with Industry-Relevant Surface Capacities for Lithium Ion-Cells

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Product

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Compositional Change of Surface Film Deposited on LiNi_0.5Mn_1.5O₄Positive Electrode

Instability of PVDF Binder in the LiFePO₄versus Li₄Ti₅O₁₂ Li‐Ion Battery Cell

Instability of PVDF Binder in the LiFePO₄versus Li₄Ti₅O₁₂ Li‐Ion Battery Cell

First-Principles Modeling of Mn(II) Migration above and Dissolution from Li_xMn₂O₄ (001) Surfaces

Manufacturing of LiNi_0.5Mn_1.5O₄Positive Composite Electrodes with Industry-Relevant Surface Capacities for Lithium Ion-Cells