Additive Effect on Reductive Decomposition and Binding of Carbonate-Based Solvent
toward Solid Electrolyte Interphase Formation in Lithium-Ion Battery!
Yoshitaka Tateyama1,2,3, Keitaro Sodeyama1,3, Keisuke Ushirogata1,4, Yukihiro Okuno1,4!
1International

Centre for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS); 2PRESTO, Japan Scienceand Technology Agency (JST); 3Elements Strategy Initiative for Catalysts & Batteries (ESICB), Kyoto University; 4Research and Development
Management Headquarters, FUJIFILM Corporation !
E-mail: TATEYAMA.Yoshitaka@nims.go.jp

Before ﬁrst charging

Negative!
ElectrodeSurvey: DFT studies

Lithium Ion Battery (LIB) is a central target to resolve current energy issues.

Electrolyte Positive!
Electrode

After ﬁrst charging

Solid Electrolyte Interphase (SEI)

Infer©NTSB
Thermal runaway

W DFT studies on reductive decompositions already exist.!
(Cluster DFT with PCM, Periodic DFT-MD)!
SEI formation mechanism NOT established yet.!
NO free energy analysis!
aaNO evaluation of activation free energies!
K. Leung, JPCC116, 9852-9861,
Only a few sets of electrolyte investigated.!
(2012)

Our target!
 Thermodynamics & kinetics of the reductive decomposition and the subsequentoligomerisation of the electrolyte molecules toward SEI formation on the atomic scale.!
 Most typical case: ethylene carbonate (EC) solvent & vinylene carobonate (VC) additive.!

Methods

DFT Car-Parrinello MD Reduction condition model!

EC system (32EC)& !
EC/VC system (31EC/VC)!
with/without Li+ion.

(Low potential modelVV vs. Li/Li+!
Constant number of electrons.)!
electricpotential

 Blue-moon ensemble for free energy proﬁle Tuned CPMD for K computerEC

VC+ Periodic boundary condition (PBC)!
+ Cubic supercell with a=15.24Å!
+ Plane wave basis with 90Ry cutoff!
+ PBE functional!
+ T=353K (Nose thermostat)!
+ ∆t=5 a.u. (~0.12fs)!
+ Several initial conﬁgurations!
% supplemental cluster BC calc. with B3LYP!

modelnegative electrodeelectrolyte

supercell

V vs Li/Li+Solvation & Reduction
VC Before reduction

A(xb ) − A(xa ) =xa+ Hybrid parallel calc.!
(Tuning achieved a rather high efﬁciency )!
+ Parallel Blue-moon ensemble (statCPMD@NIMS)!
+ Parallel I/O (statCPMD@NIMS)!

dAdx′ ′dx

One electron (1e) reductive decomposition
 Reductive decomposition of EC
CE-O2 breaking After reduction

2W

a1CC-O2 breaking

(2)

20
15
10
50-5-10-15-20-25-30

path
(1)
CE-O2
path
(2)
CC-O2

0.0

0.5

1.0
1.5
∆ξ [Å]

3

EC can be reduced even in the presence of VC.!

W(3)# a,b: Reactant = undecomposed EC-!
CO evolution!

c! Li+ - O1O2C2O2C2H4
46W# c: Reactant = OE-EC-!
C2H4 and CO32- evolution!
consistent with experiments!

e+(4b)!
# d,e: Reactant = undecomposed VC!
CO evolution!
similar to 1e reductive decomposition!

ConclusionSummary of the reductive decomposition
reactions of EC and EC/VC systems. !

 Reductive decomposition of VC

(4)!

dCE-O2 : ∆A# = 4.8, ∆A= -24.5 (kcal/mol)!

4! CO evolution

aThese results not only reveal the primary role of the VC additive in the EC solvent, butalso provide a new fundamental perspective for the reductive decomposition of carbonatebased electrolyte near the negative electrode. !

Future computational design of novel electrolytes (solvents & additives) !
with higher performance as well as higher safety.!

0.0

0.5

1.0

1.5

2.0

∆ξ [Å]
bc6b-21.8 kcal/mol

-23.3 kcal/mol

Radical attack under 1e condition

a 15∆A [kcal/mol]

10(b) A conventional pathway for the EC/VC
system, namely oligomerisation of VC
anion radical sacriﬁcially reduced. !

!

2.5% Conventional = CE-O2

!

Because the present VC mechanism is realized via 1e reduction, the irreversible capacity atthe SEI formation will decrease, consistent with the experiments. !

2.0path(3) with Li+
CE-O2_Li
path(3) without Li+
CE-O2_noLi
path(4) with Li+
CC-O2_Lipath(4) without Li+
CC-O2_noLi

CC-O2 : ∆A# ~ 5, ∆E= -21~-23 (kcal/mol)!

(a) EC only case: EC radical oligomerisation
following 2e reduction will be the sourceof SEI. !

(c) A new mechanism with 1e reduction onlyW for the EC/VC system, proposed in thiswork. VC passivates the EC anion radical. !

20151050-5-10-15-20-25

50-5-10-15-20
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5∆ξ [Å]

WWb

3.5

bond distance [Å]b5∆A [kcal/mol]b

Two electron (2e) reductive decomposition
a22.6 sFree energy proﬁle(1)

Li+-3ECVC- < Li+-3ECEC- < VC- < EC- !
Electron ﬁrst goes to VC (not coordinating to Li+)!
! Transfer to EC coordinating to Li+!
! VC- is migrating into the solvation shell!

! xb

11.9 s

1024MPI!
10 petaﬂops supercomputer! 8192 coresPotential of mean force

Li+-4EC < Li+-3ECVC by 9.6 kcal/mol!
VC is not coordinating to Li+.

EC

512 MPI!
4096 cores

dA!Z −1/2 [−λ + kT G]#x′=dx′!Z −1/2 #x′W

Refere NIMS
code!
ncecodeCalc timeper MD
unit timeConstrained MD w.r.t.!
reaction coordinate!

e-organic solvent

K. Leung, J. L. Budzien, PCCP 12,6583-6586 (2010).!

Y. Wang, S. Nakamura, M. Ue, P. B. Balbuena!
JACS123, 11708-11718 (2001).!
Y. Wang, S. Nakamura, S. Tasaki, P. B. Balbuena!
JACS124, 4408-4421 (2002).!

 “Solid Electrolyte Interface (SEI)” is formed at the ﬁrst charging!
 SEI plays a role of electronic insulator but transporting Li+ ions.!
 Quality of SEI controls capacity, power & safety, cycle life of LIB.!
 Characterisation & control of SEI is crucial for future development of LIB with high performance & high safety.

∆A [kcal/mol]

Introduction

3.0

CE-O2
r(CE-O2)r(CCC-O2
C-O2)

2.5
2.01.51.0
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5∆ξ [Å]# VC radical + intact EC: endothermic!
# EC radical + intact VC: exothermic!
∆A# = 9.7, ∆A= -16.2 (kcal/mol)!

Role of VC additive is to passivate the EC anion radical,!
not sacriﬁcial reductive decomposition & oligomerisation.

Acknowledgements
K.S. and Y.T. were partly supported by KAKENHI (# 23340089). This work also supported by the Strategic
Programs for Innovative Research (SPIRE), MEXT, and the Computational Materials Science Initiative (CMSI),
Japan. The calculations in this work were carried out on the K computer at the RIKEN AICS through the HPCI
Systems Research Projects (Proposal Numbers hp120181 and hp130021), the Fujitsu PRIMEHPC FX10 System in
the Information Technology Center, The University of Tokyo, and the supercomputer center of NIMS.!

Reference: K. Ushirogata, K. Sodeyama, Y. Okuno, and Y. Tateyama, !
J. Am. Chem. Soc. 135, 11967-11974 (2013). DOI: http://dx.doi.org/10.1021/ja405079s!