Two electrolyte decomposition pathways at nickel-rich cathode surfaces in lithium-ion batteries

Rinkel, Bernardine L. D.; Vivek, J. Padmanabhan; Garcı́a-Aráez, Nuria; Grey, Clare P.

doi:10.1039/d1ee04053g

Cited by 119 publications

(160 citation statements)

References 114 publications

Supporting

Mentioning

120

Contrasting

Order By: Relevance

“…Both mechanism (i) and (ii) are possible and may be occurring in tandem, as several electrolyte oxidation pathways generate water , in addition to the HF etching reactions of the LNMO surface and explain the cyclic production of the reaction products (e.g., increasing HF concentration seen in Figure b, while Karl Fischer titration of the pristine electrolyte yielded < 10 ppm H 2 O and HF is below the NMR detection limit in the pristine electrolyte). Similarly, HPO 2 F 2 is associated with the formation of HF, as shown in eqs and . , 2H 2 normalO + PF 5 → HPO 2 normalF 2 + 3HF POF 3 + normalH 2 normalO → HPO 2 normalF 2 + HF …”

Section: Resultsmentioning

confidence: 99%

Transition Metal Dissolution Mechanisms and Impacts on Electronic Conductivity in Composite LiNi_0.5Mn_1.5O₄ Cathode Films

et al. 2022

View full text Add to dashboard Cite

The high-voltage LiNi 0.5 Mn 1.5 O 4 (LNMO) spinel cathode material offers high energy density storage capabilities without the use of costly Co that is prevalent in other Li-ion battery chemistries (e.g., LiNi x Mn y Co z O 2 (NMC)). Unfortunately, LNMO-containing batteries suffer from poor cycling performance because of the intrinsically coupled processes of electrolyte oxidation and transition metal dissolution that occurs at high voltage. In this work, we use operando electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopies to demonstrate that transition metal dissolution in LNMO is tightly coupled to HF formation (and thus, electrolyte oxidation reactions as detected with operando and in situ solution NMR), indicative of an acid-driven disproportionation reaction that occurs during delithiation (i.e., battery charging). Leveraging the temporal resolution (s-min) of magnetic resonance, we find that the LNMO particles accelerate the rate of LiPF 6 decomposition and subsequent Mn 2+ dissolution, possibly due to the acidic nature of terminal Mn-OH groups. X-ray photoemission electron microscopy (XPEEM) provides surfacesensitive and localized X-ray absorption spectroscopy (XAS) measurements, in addition to X-ray photoelectron spectroscopy (XPS), that indicate disproportionation is enabled by surface reconstruction upon charging, which leads to surface Mn 3+ sites on the LNMO particle surface that can disproportionate into Mn 2+ (dissolved) and Mn 4+ (s) . During discharge of the battery, we observe high quantities of metal fluorides (in particular, MnF 2 ) in the cathode electrolyte interphase (CEI) on LNMO as well as the conductive carbon additives in the composite. Electronic conductivity measurements indicate that the MnF 2 decreases film conductivity by threefold compared to LiF, suggesting that this CEI component may impede both the ionic and electronic properties of the cathode. Ultimately, to prevent transition metal dissolution and the associated side reactions in spinel-type cathodes (particularly those that operate at high voltages like LNMO), the use of electrolytes that offer improved anodic stability and prevent acid byproducts will likely be necessary.

show abstract

Section: Resultsmentioning

confidence: 99%

Transition Metal Dissolution Mechanisms and Impacts on Electronic Conductivity in Composite LiNi_0.5Mn_1.5O₄ Cathode Films

et al. 2022

View full text Add to dashboard Cite

show abstract

“…Overall, the NMR data further demonstrate that the surface LiF phase can alleviate direct contact between the Fe–LNMO cathode and electrolyte, which significantly reduces the generation of HPO 2 F 2 with an active proton. Other acid species, such as formic acid, ethanol/methanol, and water, have also been reported in the literature, and they have been deemed as one of the main culprits of cell failure. , …”

Section: Resultsmentioning

confidence: 99%

“…Other acid species, such as formic acid, ethanol/ methanol, and water, have also been reported in the literature, and they have been deemed as one of the main culprits of cell failure. 40,41 To understand the chemical stability of baseline and LT1 cathodes at the charge state, both electrodes were charged to 4.8 V in full cells and rinsed with LP57 electrolyte for 2 weeks for the FTIR characterization. Figure 4b displays two regions of FTIR peaks, which are the region of P-F bond vibration peaks of free and coordinated PF 6 − (820−880 cm −1 ) and the region of C�O bond vibration peaks of free and coordinated EC and EMC solvents (1650−1850 cm −1 ).…”

Section: Analyses Of Degradations Of Interphases and Electrolytementioning

confidence: 99%

Laser-Assisted Surface Lithium Fluoride Decoration of a Cobalt-Free High-Voltage Spinel LiNi_0.5Mn_1.5O₄ Cathode for Long-Life Lithium-Ion Batteries

Cui

Khosla

Lai

et al. 2022

ACS Appl. Mater. Interfaces

View full text Add to dashboard Cite

High-voltage spinel LiNi 0.5 Mn 1.5 O 4 (LNMO) is a promising nextgeneration cathode material due to its structural stability, high operation voltage, and low cost. However, the cycle life of LNMO cells is compromised by detrimental electrode−electrolyte reactions, chemical crossover, and rapid anode degradation. Here, we demonstrate that the cycling stability of LNMO can be effectively enhanced by a high-energy laser treatment. Advanced characterizations unveil that the laser treatment induces partial decomposition of the polyvinylidene fluoride binder and formation of a surface LiF phase, which mitigates electrode−electrolyte side reactions and reduces the generation of dissolved transition-metal ions and acidic crossover species. As a result, the solid electrolyte interphase of the graphite counter electrode is thin and is composed of fewer electrolyte decomposition products. This work demonstrates the potential of laser treatment in tuning the surface chemistry of cathode materials for lithium-ion batteries.

show abstract

“…Note that oxygen contact here can only mimic the interface reaction of the CEI external surface, oxygen itself may well participate in CEI formation from the very beginning or even presents dynamic evolution upon cycle [11, 22] . Based on some previous research, the released oxygen is actually singlet oxygen, which is chemically much more active to arouse interface reactions [31] . Still, the CEI surface can be further oxidized upon O 2 contact experimentally, indicating incomplete CEI oxidization from lattice oxygen release.…”

Section: Figurementioning

confidence: 91%

“…[11,22] Based on some previous research, the released oxygen is actually singlet oxygen, which is chemically much more active to arouse interface reactions. [31] Still, the CEI surface can be further oxidized upon O 2 contact experimentally, indicating incomplete CEI oxidization from lattice oxygen release. In conventional DEMS, oxygen release can only be detected in the very first cycle, [6b] such interface reaction of oxygen participation in CEI formation and evolution may well explain this phenomenon.…”

Section: Methodsmentioning

confidence: 98%

Unveiling the High‐valence Oxygen Degradation Across the Delithiated Cathode Surface

Zhang

et al. 2022

Angewandte Chemie

View full text Add to dashboard Cite

Charge compensation on anionic redox reaction (ARR) has been promising to realize extra capacity beyond transition metal redox in battery cathodes. The practical development of ARR capacity has been hindered by high-valence oxygen instability, particularly at cathode surfaces. However, the direct probe of surface oxygen behavior has been challenging. Here, the electronic states of surface oxygen are investigated by combining mapping of resonant Auger electronic spectroscopy (mRAS) and ambient pressure X-ray photoelectron spectroscopy (APXPS) on a model LiCoO 2 cathode. The mRAS verified that no high-valence oxygen can sustain at cathode surfaces, while APXPS proves that cathode electrolyte interphase (CEI) layer evolves and oxidizes upon oxygen gas contact. This work provides valuable insights into the high-valence oxygen degradation mode across the interface. Oxygen stabilization from surface architecture is proven a prerequisite to the practical development of ARR active cathodes.

show abstract

Two electrolyte decomposition pathways at nickel-rich cathode surfaces in lithium-ion batteries

Abstract: NMR and operando gas measurements show that at low potentials, EC is dehydrogenated to VC, whereas at high potentials, EC is chemically oxidised to CO2, CO and H2O, where the water that is formed induces secondary decomposition reactions.

Cited by 119 publications

References 114 publications

Transition Metal Dissolution Mechanisms and Impacts on Electronic Conductivity in Composite LiNi_0.5Mn_1.5O₄ Cathode Films

Transition Metal Dissolution Mechanisms and Impacts on Electronic Conductivity in Composite LiNi_0.5Mn_1.5O₄ Cathode Films

Laser-Assisted Surface Lithium Fluoride Decoration of a Cobalt-Free High-Voltage Spinel LiNi_0.5Mn_1.5O₄ Cathode for Long-Life Lithium-Ion Batteries

Unveiling the High‐valence Oxygen Degradation Across the Delithiated Cathode Surface

Contact Info

Product

Resources

About

Two electrolyte decomposition pathways at nickel-rich cathode surfaces in lithium-ion batteries

Abstract: NMR and operando gas measurements show that at low potentials, EC is dehydrogenated to VC, whereas at high potentials, EC is chemically oxidised to CO2, CO and H2O, where the water that is formed induces secondary decomposition reactions.

Cited by 119 publications

References 114 publications

Transition Metal Dissolution Mechanisms and Impacts on Electronic Conductivity in Composite LiNi0.5Mn1.5O4 Cathode Films

Transition Metal Dissolution Mechanisms and Impacts on Electronic Conductivity in Composite LiNi0.5Mn1.5O4 Cathode Films

Laser-Assisted Surface Lithium Fluoride Decoration of a Cobalt-Free High-Voltage Spinel LiNi0.5Mn1.5O4 Cathode for Long-Life Lithium-Ion Batteries

Unveiling the High‐valence Oxygen Degradation Across the Delithiated Cathode Surface

Contact Info

Product

Resources

About

Transition Metal Dissolution Mechanisms and Impacts on Electronic Conductivity in Composite LiNi_0.5Mn_1.5O₄ Cathode Films

Transition Metal Dissolution Mechanisms and Impacts on Electronic Conductivity in Composite LiNi_0.5Mn_1.5O₄ Cathode Films

Laser-Assisted Surface Lithium Fluoride Decoration of a Cobalt-Free High-Voltage Spinel LiNi_0.5Mn_1.5O₄ Cathode for Long-Life Lithium-Ion Batteries