V. Focused Fundamental Research - EERE - U.S. Department of ...

V.D.5 Advanced Electrolyte and Electrolyte Additives (ANL)
Khalil Amine (Project Manager)
Argonne National Laboratory
Chemical Sciences and Engineering Division
Argonne, IL 60439
Phone: (630) 252-3838; Fax: (630) 252-4672
E-mail: amine@anl.gov
Start Date: Jan 1, 2010
Projected End Date: Dec. 30, 2014
Objectives
· Use our advanced quantum chemical model to predict
functional additives that form stable Solid Electrolyte
Interphases (SEI) on electrodes and for overcharge
protection.
· Use the model to predict how additives interact with
the surface of anode and cathode to form good
protective films.
· Synthesize suitable additives predicted by the
modeling, characterize them and carry out extensive
cycle and calendar life test.
Technical Barriers
This project addresses the following technical barriers
in lithium ion battery technology
(a) Cycle/calendar life
(b) Abuse tolerance
Technical Targets
· New additives that form stable film formation on
anodes and cathodes
· Increased cycle life
· Improved safety
Accomplishments
· We have used our improved quantum chemical model
for screening of reduction and oxidation potentials of
over 300 additive molecules and shuttle molecules.
· Further screening has identified about 75 candidates
with favorable reaction pathways for decomposition
including oxalates, carbonates, anhydrides., and allyl
substituted compounds.
· Tetrafluoro(oxalate) phosphate and lithium
difluoro[oxalato] borate were found to be effective
electrolyte additives to significantly improve both the
life and safety of Li-ion batteries. Density functional
calculations have shown how the fluorine groups
promote a good SEI layer.
· A computational study of the reaction pathways
involving one and two-electron transfer for
decomposition of ethylene carbonate has provided
evidence for possible products important in forming
an effective SEI.
· Among promising additive candidates predicted by
density functional theory is 1,3,5-triallyl­
[1,3,5]triazinane-2,4,6-trione (TTT). This has been
found to be effective as an SEI additive in
experimental testing.
Introduction
The development of advanced electrolytes with
functional additives that provide for stabilization of the
interface of lithium ion batteries to prevent detrimental
decomposition is important for enhancing the cycle life
and safety of lithium ion batteries. In addition, electrolyte
additives can provide protection against overcharge. We
are using high level quantum chemical methods to screen
for electrolyte additives that can be added to the electrolyte
and form a protective SEI during the initial charging to
prevent any conventional passivation film from taking
place first. These additives must form a thin and a uniform
film that protects the electrode. We are also investigating
new additives for overcharge protection.
Approach
We are using a joint theoretical/experimental
approach for design and discovery of new electrolytic
additives that react in a preferential manner to prevent
detrimental decomposition of cell components. We use
quantum chemical screening to predict oxidation and
reduction potentials and decomposition pathways that form
desirable coatings and to find stable additives for
overcharge protection. Synthesis of the new additives and
testing of them is done to determine the cycle life of the
batteries. Investigation of the SEI is done to determine
structure and formation with both experiment and theory.
Results
Screening of electrolyte additives. Over 300
candidate additives have been screened for their reduction
FY 2011 Annual Progress Report 609 Energy Storage R&D