Decomposition of phosphorus-containing additives at a charged NMC surface through potentiostatic holds

Adam Tornheim; Juan C. Garcia; Ritu Sahore; Hakim Iddir; Ira Bloom; Zhengcheng Zhang

doi:10.1149/2.0951902jes

Decomposition of phosphorus-containing additives at a charged NMC surface through potentiostatic holds

Adam Tornheim, Juan C. Garcia, Ritu Sahore, Hakim Iddir, Ira Bloom, Zhengcheng Zhang

Research output: Contribution to journal › Article › peer-review

13 Scopus citations

Abstract

Multiple phosphorus-containing compounds were evaluated as electrolyte additives for their reactivity at the cathode surface using LiNi_0.5Mn_0.3Co_0.2O₂ (NMC532) // Li₄Ti₅O₁₂ (LTO) cells with both cycling and high voltage potentiostatic holds. We surveyed additives including phosphite and phosphate derivatives with either trifluoroethyl, ethyl, or trimethylsilyl groups. Phosphite additives with the same substituents showed lower Coulombic efficiency (CE) and higher oxidation current during the potentiostatic hold. Regardless of substitution group, all phosphates showed slightly higher CE than the additive-free electrolyte (baseline). However, no additive significantly decreases oxidation reactions over the course of the potentiostatic hold, indicating a non-passivated surface. Post-mortem X-ray photoelectron spectroscopy analysis of the cathodes indicates that the additive with trimethylsilyl groups produces significantly more oxygen and phosphorus on the cathode surface for both phosphites and phosphates. Atomistic simulations indicate that these additives are susceptible to electrochemical and chemical oxidation, however chemical oxidation is much more likely for the phosphite additives. The identity of ligands on the phosphorus-containing additive can dramatically affect both the decomposition current and the cathode surface after the potentiostatic hold.

Original language	English
Pages (from-to)	A440-A447
Journal	Journal of the Electrochemical Society
Volume	166
Issue number	4
DOIs	https://doi.org/10.1149/2.0951902jes
State	Published - 2019
Externally published	Yes

Funding

The electrodes used in this article were fabricated at Argonne National Laboratory’s Cell Analysis, Modeling and Prototyping (CAMP) Facility. We acknowledge the computing resources provided on Bebop, a high-performance computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory. This research also used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231. Support from David Howell and Peter Faguy at the Vehicle Technologies Office (VTO), U.S. Department of Energy, is gratefully acknowledged. The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357. The electrodes used in this article were fabricated at Argonne National Laboratory's Cell Analysis, Modeling and Prototyping (CAMP) Facility. We acknowledge the computing resources provided on Bebop, a high-performance computing cluster operated by the Laboratory Computing Resource Center at Argonne National Laboratory. This research also used resources of the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231. Support from David Howell and Peter Faguy at the Vehicle Technologies Office (VTO), U.S. Department of Energy, is gratefully acknowledged. The submitted manuscript has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357.

Funders	Funder number
U.S. Department of Energy Office of Science
U.S. Department of Energy
Center for Advanced Materials Processing, Clarkson University
Vehicle Technologies Office	DE-AC02-06CH11357
Royal Society of Canada	DE-AC02-05CH11231

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title = "Decomposition of phosphorus-containing additives at a charged NMC surface through potentiostatic holds",

abstract = "Multiple phosphorus-containing compounds were evaluated as electrolyte additives for their reactivity at the cathode surface using LiNi0.5Mn0.3Co0.2O2 (NMC532) // Li4Ti5O12 (LTO) cells with both cycling and high voltage potentiostatic holds. We surveyed additives including phosphite and phosphate derivatives with either trifluoroethyl, ethyl, or trimethylsilyl groups. Phosphite additives with the same substituents showed lower Coulombic efficiency (CE) and higher oxidation current during the potentiostatic hold. Regardless of substitution group, all phosphates showed slightly higher CE than the additive-free electrolyte (baseline). However, no additive significantly decreases oxidation reactions over the course of the potentiostatic hold, indicating a non-passivated surface. Post-mortem X-ray photoelectron spectroscopy analysis of the cathodes indicates that the additive with trimethylsilyl groups produces significantly more oxygen and phosphorus on the cathode surface for both phosphites and phosphates. Atomistic simulations indicate that these additives are susceptible to electrochemical and chemical oxidation, however chemical oxidation is much more likely for the phosphite additives. The identity of ligands on the phosphorus-containing additive can dramatically affect both the decomposition current and the cathode surface after the potentiostatic hold.",

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AU - Iddir, Hakim

AU - Bloom, Ira

AU - Zhang, Zhengcheng

PY - 2019

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N2 - Multiple phosphorus-containing compounds were evaluated as electrolyte additives for their reactivity at the cathode surface using LiNi0.5Mn0.3Co0.2O2 (NMC532) // Li4Ti5O12 (LTO) cells with both cycling and high voltage potentiostatic holds. We surveyed additives including phosphite and phosphate derivatives with either trifluoroethyl, ethyl, or trimethylsilyl groups. Phosphite additives with the same substituents showed lower Coulombic efficiency (CE) and higher oxidation current during the potentiostatic hold. Regardless of substitution group, all phosphates showed slightly higher CE than the additive-free electrolyte (baseline). However, no additive significantly decreases oxidation reactions over the course of the potentiostatic hold, indicating a non-passivated surface. Post-mortem X-ray photoelectron spectroscopy analysis of the cathodes indicates that the additive with trimethylsilyl groups produces significantly more oxygen and phosphorus on the cathode surface for both phosphites and phosphates. Atomistic simulations indicate that these additives are susceptible to electrochemical and chemical oxidation, however chemical oxidation is much more likely for the phosphite additives. The identity of ligands on the phosphorus-containing additive can dramatically affect both the decomposition current and the cathode surface after the potentiostatic hold.

AB - Multiple phosphorus-containing compounds were evaluated as electrolyte additives for their reactivity at the cathode surface using LiNi0.5Mn0.3Co0.2O2 (NMC532) // Li4Ti5O12 (LTO) cells with both cycling and high voltage potentiostatic holds. We surveyed additives including phosphite and phosphate derivatives with either trifluoroethyl, ethyl, or trimethylsilyl groups. Phosphite additives with the same substituents showed lower Coulombic efficiency (CE) and higher oxidation current during the potentiostatic hold. Regardless of substitution group, all phosphates showed slightly higher CE than the additive-free electrolyte (baseline). However, no additive significantly decreases oxidation reactions over the course of the potentiostatic hold, indicating a non-passivated surface. Post-mortem X-ray photoelectron spectroscopy analysis of the cathodes indicates that the additive with trimethylsilyl groups produces significantly more oxygen and phosphorus on the cathode surface for both phosphites and phosphates. Atomistic simulations indicate that these additives are susceptible to electrochemical and chemical oxidation, however chemical oxidation is much more likely for the phosphite additives. The identity of ligands on the phosphorus-containing additive can dramatically affect both the decomposition current and the cathode surface after the potentiostatic hold.

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Decomposition of phosphorus-containing additives at a charged NMC surface through potentiostatic holds

Abstract

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