A Parametric Open Circuit Voltage Model for Lithium Ion Batteries

Birkl, Christoph; McTurk, Euan; Roberts, Matthew; Bruce, Peter G.; Howey, David A.

doi:10.1149/2.0331512jes

Cited by 137 publications

(121 citation statements)

References 28 publications

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“…The method for the manufacture of half-cells is described elsewhere. 27 The PE material of the Kokam pouch cells is a blend of lithium cobalt oxide (LCO) and lithium nickel cobalt oxide (NCO) and the NE material is graphite. Two half-cells were made-one PE and one NE half-cell.…”

Section: Methodsmentioning

confidence: 99%

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Degradation Diagnostics for Commercial Lithium-Ion Cells Tested at − 10°C

Birkl

McTurk

Zekoll

et al. 2017

J. Electrochem. Soc.

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Degradation of lithium ion (Li-ion) cells affects both performance and safety of Li-ion batteries. In order to avoid potential safety hazards, it is crucial to detect the onset and extent of critical degradation modes in commercial Li-ion cells. This work demonstrates the application of a diagnostic algorithm to identify and quantify degradation modes of commercial Li-ion pouch cells cycled at −10 • C and a C-rate of 2 C. Rapid loss of active negative electrode material was successfully identified and results were validated using 3-electrode cells, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The positive electrode material was less strongly affected by the tests, as found by the diagnostic algorithm and confirmed with EDX and SEM results. Lithium ion (Li-ion) cells degrade as a result of usage and environmental influences, typically resulting in capacity fade and increased internal resistance.1-3 Some degradation mechanisms can lead to safety hazards through increased risk of fire or explosion. The deposition of metallic lithium and dendrite formation on graphite negative electrodes (NE) are particularly dangerous mechanisms, since metallic dendrites can pierce the separator and lead to internal short-circuits resulting in thermal runaway. [4][5][6] Understanding and detecting lithium plating and dendrite formation are important milestones on the pathway to safer, more reliable Li-ion batteries. Low operating temperatures during charge increase the risk of lithium plating and dendrite formation. [7][8][9][10][11][12][13][14][15][16] This makes it important to assess and model the behavior of Li-ion batteries at low temperatures, which is undertaken in this study.Arora et al. 4 proposed a mathematical model to predict lithium deposition on the NE during charge and overcharge, which can be used to determine operational and design limitations in order to minimize safety hazards. Other authors have focused on in-situ detection of lithium plating using electrochemical calorimetry, 17 a combination of an electrochemical model with a particle filter, 18 Although in-situ detection of lithium plating is an important advance, safety hazards can be further reduced by detecting the factors leading up to lithium plating before the onset of the plating mechanism itself. Deposition of metallic lithium on graphite NEs occurs under high charging rates, at low charging temperatures and in poorly balanced cells with an excess of active positive electrode (PE) material. 4,12,24,25 These circumstances are easily avoided in new cells by appropriate cell design and observation of operational limitations such as minimal charging temperature and maximal cell voltages and current rates. However, as cells degrade, active electrode material can be lost, changing the ratio of negative to positive electrode material and the current rates and voltage limits imposed on the remaining active material. Loss of NE material leads to higher current rates on the NE and a higher ratio of active PE to NE material...

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Section: Methodsmentioning

confidence: 99%

“…For a more detailed account, the reader is referred to Ref. 27. The OCV of the electrodes can be described implicitly by…”

Section: Methodsmentioning

confidence: 99%

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Degradation Diagnostics for Commercial Lithium-Ion Cells Tested at − 10°C

Birkl

McTurk

Zekoll

et al. 2017

J. Electrochem. Soc.

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“…7 (again, Li-graphite) and 8 for LiGa. Birkl et al 9 employed a similar approach (Eq. 9 below) to obtain parameter-fit expressions for full-cell open-circuit potentials of commercial lithiated graphite/metal oxide batteries.…”

Section: Theory For the Equilibrium Thermodynamicsmentioning

confidence: 99%

Thermodynamic Model for Substitutional Materials: Application to Lithiated Graphite, Spinel Manganese Oxide, Iron Phosphate, and Layered Nickel-Manganese-Cobalt Oxide

Baker

Koch²,

Xiao

et al. 2017

J. Electrochem. Soc.

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We derive and implement a method to describe the thermodynamics of electrode materials based on a substitutional lattice model. To assess the utility and generality of the method, we compare model results with experimental data for a variety of electrode materials: lithiated graphite and layered nickel-manganese-cobalt oxide (Chevrolet Bolt Electric Vehicle negative and positive electrode materials, respectively), manganese oxide (in the positive electrodes of the Gen 1 and Gen 2 Chevrolet Volt Extended Range Electric Vehicle and the positive electrode of many high-power-density batteries), and iron phosphate (Gen 1 Chevrolet Spark Electric Vehicle positive electrode material and of immediate interest for 12 and 48 V applications). An early version of the model has been applied to lithiated silicon (Li-Si). As was found in the Li-Si study, the model enables one to quantitatively represent experimental data from these different electrode materials with a small number of parameters, and, in this sense, the approach is both general and efficient. An open question is the utility of controlled-potential vs. controlled-current experiments for the elucidation of the system thermodynamics. We provide commentary on this question, and we highlight other open questions throughout this work. Central to the modeling of electrochemical systems, particularly batteries relying on solid-state diffusion within the active materials, is an accurate description of the system thermodynamics.1-4 We describe and implement a thermodynamic model for substitutional electrode materials. At the heart of the model is a simple expression for the open-circuit potential U in terms of the fraction of filled sites x within a host material. To assess the value of the model, we apply it to four electrode materials of commercial interest today: lithiated graphite, spinel manganese oxide, iron phosphate, and nickel-manganese-cobalt oxide. The model is an expanded version of that described in Ref. 12. A slight alteration is needed to describe the nickel-manganese-cobalt oxide so that inaccessible lithium can be considered (giving rise to x 0 in Table I), and we also describe how reactions between sites within the electrode material can be addressed.This document is organized as follows. First, we provide an overview of the materials and instrumentation for the experimental characterization of the electrode materials. An introduction of the thermodynamic model is then presented, followed by a detailed description of the model. A discussion of results is then presented, followed by a brief Appendix devoted to the convergence properties of the series summation employed in the U(x) model. • C under about 0.01 Torr vacuum. Other materials were dried at 100 Experimental• C under vacuum of about 0.01 Torr. Cell assembly and cycling were performed under an inert argon atmosphere with O 2 and H 2 O concentrations < 1 ppm. Cycling was performed with a Princeton Applied Research PMC 2000 potentiostat/galvanostat. For the voltammetry work on the Ni 0.6 Mn 0.2 Co ...

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“…The data obtained from repeated electrochemical characterizations of WE and CE may also be used in an open circuit voltage model to investigate different electrode-specific aging mechanisms. 11 Moreover, the presented technique can be used to construct 3-electrode cells for the validation of lithium-ion cell models aimed at simulating electrode and cell potentials, using a simple and reproducible procedure without detrimental modifications.…”

Section: Discussionmentioning

confidence: 99%

Minimally Invasive Insertion of Reference Electrodes into Commercial Lithium-Ion Pouch Cells

McTurk

Birkl

Roberts

et al. 2015

ECS Electrochemistry Letters

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Two procedures to introduce a lithium metal reference electrode into commercially manufactured lithium-ion pouch cells (Kokam SLPB 533459H4) are described and compared. By introducing a stable reference potential, the individual behavior of the positive and negative electrodes can be studied in operando under normal cycling. Unmodified cells and half-cells made from harvested electrode material were cycled under identical conditions to the modified cells to compare capacity degradation during cycling and thus validate each modification procedure for degradation testing. A configuration that did not affect the performance of the cell over 20 cycles was successfully developed. © The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. [DOI: 10.1149/2.0081512eel] All rights reserved.Manuscript submitted August 11, 2015; revised manuscript received September 29, 2015. Published November 4, 2015 Understanding the behavior of the individual electrodes in commercial lithium-ion cells gives insight into the degradation mechanisms that result in capacity and power fade and enables design of better battery management systems (BMSs), for example by allowing more accurate predictions of future cell behavior.1 However, commercial lithium-ion cells are two-electrode systems i.e. only the potential difference between the working electrode (WE) and counter electrode (CE) may be measured. Therefore, the performance of the electrodes cannot be monitored in isolation and it is impossible to determine the electrode which is ultimately determining cycle life. The introduction of a stable fixed reference electrode (RE) potential allows the WE and CE behavior to be investigated separately.Previous studies have introduced a RE into commercial cylindrical 18650 cells.2-5 However, the modifications may not always have resulted in the ideal conditions, for example by (a) exposing the cell to a different electrolyte from that originally used in the cell, 2 (b) positioning the RE some distance from the WE and CE, 3 or (c) risking damaging the cell through invasive and complex drilling procedures to insert the RE into the centre of the cell.2,4,5 Previous studies of pouch cells have typically involved the construction of bespoke 3-electrode cells in the lab 6,7 rather than the modification of existing commercial cells, thus not allowing a direct, in-situ comparison with unmodified commercial cells.Here we discuss the development of two different modification procedures to insert a RE into commercial lithium-ion pouch cells with minimal intrusion on the original structure and chemistry of the cell: (1) the "patch" method, and (2) the "wire" method. This allows separate cycling and degradation data for the WE and CE to be obtained. The accuracy of the results obtained from the cell modifications and ...

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A Parametric Open Circuit Voltage Model for Lithium Ion Batteries

Cited by 137 publications

References 28 publications

Degradation Diagnostics for Commercial Lithium-Ion Cells Tested at − 10°C

Degradation Diagnostics for Commercial Lithium-Ion Cells Tested at − 10°C

Thermodynamic Model for Substitutional Materials: Application to Lithiated Graphite, Spinel Manganese Oxide, Iron Phosphate, and Layered Nickel-Manganese-Cobalt Oxide

Minimally Invasive Insertion of Reference Electrodes into Commercial Lithium-Ion Pouch Cells

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