High voltage lithium ion batteries have been a focus in the current energy storage research due to their potential application as high energy density batteries for electric vehicles. With more energy stored in a system with the same weight and volume, the impact of battery fabrication and its utilization on the environment will be minimized .Electrolyte solutions based on fluorinated solvents were studied in high-voltage Li-ion cells using lithium as the anode has a great enhancement over conventional electrolyte and Li1.2Mn0.56Co0.08Ni0.16O2 as the cathode provides excellent voltage stability on the 5.0 V at both ambient and elevated temperatures. Performance can be reach peak by replacing convectional alky carbonate solvents in electrolyte solution by fluorinated cosolvents. Fluorinated electrolyte solution act as a buffering surface film which is highly reactive electrophilic alkyl carbonates, from continuous detrimental reactions with solution species. Excellent cyclic performance was recorded in solution containing fluorinated solvents. The extraordinary electrochemical stability of this electrolyte solution makes it a suitable candidate for other high-voltage cathode materials.

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Electrolyte Solutions for Rechargeable Li-Ion
Batteries Based on Fluorinated Solvents
Submitted by
Amal Thomas
B17CHA66
Guide
Prof. Anand Unni
TKM College of Engineering
Chemical Engineering
CH451 - Seminar & Project Preliminary

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 Introduction
 Materials
 HE-NCM and their performance
 Electrolyte Solution
 Morphology of Li deposit & SEI
 Electrochemical performance
 Effect of TMSP
 Conclusion
Contents
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High-energy-density Lithium ion batteries
(LIBs), the major power source for portable
electronics.
High operation voltage create challenges for
battery components.
Electrolyte solvents with a high oxidation
potential help to mitigate above challenge.
[Figure 1]
Introduction
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https://bloncampus/columns/cleantech/look-beyond-lithium-for-powerful-
batteries/article31868310.ece

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dMaterials
 Cathode
High Energy NCM Materials
 Anode
Li Metal
 Electrolyte
1,2-dimethoxyethane(DME), 1,1,2,2-
tetrafluoroethyl-2,2,3,3-tetrafluoropropyl
ether (TTE)|, fluoroethylene carbonate
(FEC) [Figure 2]

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Major elements Li, Mn, Ni, Co and O.
Higher Li content, increase capacity specific capacity and energy.
Excess Li and Mn, initially form two phases:
 Monoclinic electrochemically inactive phase
 Rhombohedral electrochemically active phase
Forms intrinsically unstable high-capacity cathode materials.

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 Reactive Gas Treatment
 Lattice doping
 Surface Coating
 Electrolyte Solution
Improving performance of HE-NCM
[Figure
3]

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dElectrolyte’s Quality
Isolate the electron and ion transport
pathways.
Promote ion-pair dissociation.
Penetrate and wet, the electrodes and
separator.
Should not leak, combust or vaporize .
Chemically robust.
Stable in the normal operating voltage range.

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d
Fluorinated Electrolyte Solution
React on the surface and form buffering surface films.
Organic fluorinated carbonates have higher oxidation stability with lower
flammability.
Effective passivation of reactive electrodes.
Fluorinated solvents -strong electron-withdrawing effect.

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Morphology of Li metal deposit
SEM images of Li metal electrochemically plated on a Cu
substrate (a,e) DME, (b,f) DME + FEC, (c,g) DME + TTE + FEC
 DME
Nonuniform shapes and sizes
 DME+FEC
Densely deposited and tightly packed
Formed desirable Stable Electrolyte
Interphase(SEI)
 DME+FEC+TTE
Denser structure of Li deposits
[Figure 4]

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Stable Electrolyte Interface –TTE (SEI)
 During initial Li plating process,
FEC adsorbed on the Li metal.
 Initial LiF formation.
 Aggressive reductive
decomposition of TTE to form
LiF.
[Figure 5]

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Electrochemical Performances
 DME +TTE + FEC - high discharge capacity.
 Reduced overpotential during precycling - penetration
of the electrolyte.
 Large overpotential is associated with activation of
passivated Li metal anode and kinetics of delithiation
from the cathode.
 DME +TTE + FEC – high cycle no
Cycle numberFigure 6

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 (a) Interfacial degradation of the HE-NCM
cathode in DME.
 (b) HE-NCM cathode protected by robust and
uniform CEI in DME + TTE + FEC.
 Anisotropic strain by heterogeneous cycling
led to fragmentation of NCM secondary
particles and resulting in the accumulation of
resistive byproducts in NCM secondary
particles
[Figure 7]

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Effect of Adding 1% TMSP to Fluorinated Electrolyte Solutions
Presence of trace HF in solutions have a detrimental effect on the electrodes’
stability.
TMSP removes the HF molecules from the electrolyte solutions.
Forms a protective film on the cathode surface.
Improves cells performance.

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[Figure 8]

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Excellent performance can achieved by replacing standard alkyl carbonate solvents
by fluorinated cosolvents.
TTE as a cosolvent with concentrated ether-based electrolytes promoted the
formation of an SEI.
Presence of fluorine atoms in the solvent molecules enables the elimination of HF.
TMSP, additive to solutions containing fluorinated solvents, the cycling stability of
HE-NCM will enhanced.
Conclusion
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References
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Aurbach ,2020, “Electrolyte Solutions for Rechargeable Li-Ion Batteries Based on Fluorinated Solvents,”
ACS Appl. Energy Mater, 3, 7485−7499.
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Gumjae Park, 2019, “Fluorine-incorporated interface enhances cycling stability of lithium metal batteries
with Ni-rich NCM cathodes,” Nano Energy Elsevier 104309.
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Electrolytes for Li-Ion Batteries: The Lithium Difluoro(oxalato)borate Additive for Stabilizing the Solid
Electrolyte Interphase”, ACS Omega, 8741−875.

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4. Prasant Kumar Nayak, Judith Grinblat, Elena Levi, Mikhael Levi, Boris Markovsky and Doron Aurbach,
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Electrolytes for Li-Ion Batteries: The Lithium Difluoro(oxalato)borate Additive for Stabilizing the Solid
Electrolyte Interphase”, ACS Omega, 8741−875.
7. Prasant Kumar Nayak, Judith Grinblat, Elena Levi, Mikhael Levi, Boris Markovsky and Doron Aurbach,
2017 “Understanding the influence of Mg doping for the stabilization of capacity and higher discharge
voltage of Li- and Mn-rich cathodes for Li-ion batteries”, Royal Society of Chemistry.

18. Thank You