The reversible heat effects at lithium iron phosphate- and graphite electrodes

Gunnarshaug, Astrid Fagertun; Kjelstrup, Signe; Bedeaux, Dick; Richter, Frank; Burheim, Odne Stokke

doi:10.1016/j.electacta.2019.135567

Cited by 18 publications

(42 citation statements)

References 21 publications

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“…Transient concentration gradients can be tracked voltammetrically using open-circuit-potential (OCP) measurements between two identical reference electrodes. For small enough concentration gradients, the OCP will be directly proportional to concentration differences [11,18,21].…”

Section: Restricted Diffusionmentioning

confidence: 99%

Shifting-reference concentration cells to refine composition-dependent transport characterization of binary lithium-ion electrolytes

Wang

Hou

Karanjavala

et al. 2020

Electrochimica Acta

105

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We present a novel 'shifting-reference concentration-cell' method, altering the traditional protocol for measuring liquid-junction potentials by using a sequence of reference concentrations in regularly spaced intervals, rather than a fixed reference. The method, applied to solutions of lithium hexafluorophosphate (LiPF6) in propylene carbonate (PC) and ethyl methyl carbonate (EMC) at 25 °C, helps to determine thermodynamic factors more accurately, and is useful across a wider concentration range. For LiPF6:PC, good agreement with prior fixed-reference measurements is shown, and new data at low concentrations is consistent with Debye-Hückel theory. Original composition-dependent property correlations are produced for LiPF6:EMC up to 2 M, including the density and thermodynamic factor, as well as isothermal-transport properties such as transference number, conductivity, diffusivity, and viscosity. Polarization-relaxation simulations validate these correlations. For LiPF6:EMC, the low thermodynamic factor and cation/anion Stefan-Maxwell diffusivity, as well as Walden analysis, suggest that ion association dominates, even at high dilution.

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Section: Restricted Diffusionmentioning

confidence: 99%

Shifting-reference concentration cells to refine composition-dependent transport characterization of binary lithium-ion electrolytes

Wang

Hou

Karanjavala

et al. 2020

Electrochimica Acta

105

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“…Gunnarshaug et al 16 derived the Seebeck coefficient of a LFP thermoelectric cell with ternary electrolyte and two identical electrodes. Their derivations included all reversible heat effects.…”

Section: Thermoelectric Cell Theorymentioning

confidence: 99%

“…More than two components in the electrolyte can complicate the situation. 16 The emf of the initial and stationary states can differ widely. 16 The difference gives information on the Soret effect or the heats of transfer in the electrolyte.…”

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confidence: 99%

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Review—Reversible Heat Effects in Cells Relevant for Lithium-Ion Batteries

Gunnarshaug

Vie

Kjelstrup

2021

J. Electrochem. Soc.

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We review measurements of reversible heat effects in lithium-ion batteries, i.e. entropy changes and Seebeck coefficients of cells with relevant electrodes. We show how to compute the Peltier heat of battery electrodes from Seebeck coefficients. The Seebeck coefficient depends on the heat of transfer (Soret effect), which is found from the difference of initial and stationary state values of the Seebeck coefficient. We apply non-equilibrium thermodynamics theory and obtain initial Peltier heats not reported before. For the oxidation of lithium metal we propose the value 34 ± 2 kJ mol −1 when the electrolyte contains 1 M LiPF 6 , while the value is 29 ± 1 kJ mol −1 when the electrolyte contains 1 M LiClO 4 . The positive values imply that the electrode cools when it serves as an anode. For oxidation of lithium under stationary state conditions, the stationary state Peltier heat is ≈120 kJ mol −1 . A large reversible heating effect can then be expected for the single electrode; much larger than expected from the full-cell entropy change. These values have a bearing on thermal modelling of batteries. Peltier heats for anodic reactions are presented in tables available for such modelling. We discuss the need for measurements and point at opportunities.

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“…At varied C-rates, the selfheating rate curves during charge and discharge process are symmetrical ( Figure S2d-f), evidencing that the heat generation mainly consisted of the irreversible joule heat and the reversible electrochemical reaction heat. [49][50] Obviously, the reversible electrochemical reaction heat dominates the total heat at low rates and irreversible joule heat dominates the total heat at high rates. These results clearly tell us that, at the worst case of adiabatic condition, the 5 Ah NCM523/G pouch cell at higher rates will easily get thermal runaway in few cycles, revealing the importance of battery thermal management.…”

Section: Heat Generation During Charge-discharge Operationmentioning

confidence: 99%

Uncovering hydrogen anion triggered thermal runaway mechanism of a high-energy LiNi0.5Co0.2Mn0.3O2/graphite pouch cell

Huang

et al. 2021

Preprint

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The continuous energy density increase of lithium ion batteries (LIBs) inevitably accompanies with the rising of safety concerns. Here, the thermal characteristics of a high-energy 5 Ah LiNi0.5Co0.2Mn0.3O2/graphite pouch cell using a thermally stable dual-salt electrolyte were analyzed. Heat determination during cycling at two boundary scenarios of adiabatic and isothermal environment clearly states the necessity of designing an efficient and smart battery thermal management system. More importantly, it is innovatively proposed that the hydrogen anion (H−) induced H2 releasing at anode side and H2 migration to cathode side is the rooted thermal runaway trigger of the pouch cell, while the phase transformation of lithiated graphite anode and the O2-releasing by delithiated cathode are just accelerating factors for thermal runaway. These findings will shed promising lights on thermal runaway route map depiction and thermal runaway prevention, as well as formulation of electrolyte for high energy safer LIBs.

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The reversible heat effects at lithium iron phosphate- and graphite electrodes

Cited by 18 publications

References 21 publications

Shifting-reference concentration cells to refine composition-dependent transport characterization of binary lithium-ion electrolytes

Shifting-reference concentration cells to refine composition-dependent transport characterization of binary lithium-ion electrolytes

Review—Reversible Heat Effects in Cells Relevant for Lithium-Ion Batteries

Uncovering hydrogen anion triggered thermal runaway mechanism of a high-energy LiNi0.5Co0.2Mn0.3O2/graphite pouch cell

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