development of electrolytes for lithium-ion batteries

Development of Electrolytes for Lithium-ion Batteries

Brett LuchtUniversity of Rhode Island

May 11th, 2001ES067

This presentation does not contain any proprietary, confidential, or otherwise restricted information

2

• 04/01/2009• 12/31/2113• 44 Percent complete

• Barriers addressed– (Calendar Life (40 oC for 15 years)– Cycle life (5000 cycles)– Abuse Tolerance -Survival Temp

Range (-46 to 66 oC)– Performance – Increased Energy

Density

• Total project funding– DOE share $731 K

• Funding received in FY10 -$146 K

• Funding for FY11 - $146 K

Timeline

Budget

Barriers

Partners

Overview

• D. Abraham (ANL)

• M. Smart (NASA JPL)

• W. Li (S. China Univ. Tech.)

• V. Battaglia & J. Kerr (LBNL)

• M. Payne (Novolyte)

• F. Puglia & B. Ravdel (Yardney)

• G. Smith & O. Borodin (U. Utah)

33

Develop novel electrolytes for lithium ion batteries that improve performance to meet or exceed DOE goals.

• Develop novel electrolytes with superior performance to SOA (LiPF6).• Develop additives that allow for formation of protective coatings on the

cathode, i.e., a cathode SEI, and enhance electrochemical stability above 4.5 V.

• Develop electrolytes for improved performance of Si-based alloy anodes.

• The development of improved electrolytes is of critical importance for meeting the DOE goals for cycle life, calendar life, temperature of performance, capacity loss, and Increased energy density.

Objective

44

MilestonesFY10• (a) Develop cathode film forming additives for high voltage (>4.5 V vs Li) cathode

materials. (March 10) Completed• (b) Investigate cell performance upon accelerated aging of graphite/LiNixCo1-2xMnxO2

cells with LiPF4(C2O4) electrolytes compared to LiPF6 electrolytes. (March 10) Completed

• (c) Investigate cell performance of LiPF4(C2O4) compared to LiPF6 in small cells with new chemistries graphite/LiMn2O4,LiNixCo1-2xMnxO2 cells, or with PC electrolytes. (Sept 10) completed

• (d) Develop commercially viable synthesis for LiPF4(C2O4). (Sept 10) completed

FY11• (a) Develop improved cathode film forming additives for high voltage Ni-Mn spinel

cathode materials. (July 11) on schedule• (b) Investigate cell performance upon accelerated aging of graphite/LiNiXCo1-

2xMnXO2 with LiPF4(C2O4)/PC electrolytes compared to LiPF6 electrolytes. (March 11) delayed

• (c) Develop an understanding of the source of irreversible capacity loss with LiPF4(C2O4) electrolytes during formation cycling (July 11) completed

• (d) Investigate novel electrolytes to improve performance of Si-alloy anodes (Sept 11) On Schedule.

55

• Investigate properties of LiPF4C2O4/carbonate electrolytes in small Li-ion cells.

• Investigate electrode surface films for cells cycled with LiPF4(C2O4) to determine source of performance differences.

• Investigate cathode film forming additives for high voltage (> 4.5 V) cathode materials.

• Investigate incorporation of electrolyte SEI forming additives for Si-based Alloy anodes.

• Investigate the surface of cathodes and anodes cycled with novel electrolytes, with or without additives, to develop a mechanistic understanding of interface formation and degradation.

• Use computational methods to screen potentially interesting additives.

Approach

66

• Investigated combinations of additives for LiPF6 electrolytes.

• Investigated cell performance upon accelerated aging of graphite/LiNixCo1-2xMnxO2 cells with LiPF4(C2O4) electrolytes compared to LiPF6 electrolytes.

• Studied changes in anode SEI structure with LiPF4(C2O4).

• Investigated LiPF4(C2O4) in small cells and produce 100 g LiPF4(C2O4) for testing.

• Developed cathode film forming additives for high voltage (>4.5 V vs Li) cathode materials.

Previous Technical Accomplishments

0 10 20 30 40 500

1

2

3

4

5

60

70

80

90

100

Capa

city,

mAh

Cycle Number

LiPF6 LiPF4(C2O4)

initial formation cycles

Effic

ienc

y, %

Cycling behavior of LiPF4(C2O4) and LiPF6 in 1:1:1 (EC:DEC:DMC) in MCMB/LiNi0.8Co0.2O2 cells before and after storage at 65 oC for two weeks.

The cycling performance of Li1.17Mn0.58Ni0.25O2 half cells charged to 4.9 V vs Li confirm superior cycling performance with additives.

0 10 20 30 40 50 600.0007

0.0008

0.0009

0.0010

0.0011

0.0012

0.0013

0.0014

0.0015

0.0016

0.0017

0.0018

Standard 1% LiBOB 0.5% 2,5-DHF Additive X

Capa

city

(Ah)

Cycling Number

FY 10 Technical Accomplishments: Performance of LiPF4(C2O4)

7

0 5 10 15 20 250.0000

0.0005

0.0010

0.0015

0.0020

0.0025

Dis

char

ge C

apac

ity (A

h)

cycling numbers (n)

LiFePO4 with LiPF6 in EC/EMC(3:7) LiFePO4 with LiFOP in EC/EMC(3:7)

0 5 10 15 20 250.0000

0.0001

0.0002

0.0003

0.0004

0.0005

0.0006

0.0007

0.0008

0.0009

0.0010

0.0011

LiMn2O4 with LiPF6 in EC/EMC(3:7) LiMn2O4 with LiFOP in EC/EMC(3:7)

Disc

harg

e Ca

pacit

y (Ah

)

Cycling Numbers (n)

LiPF6 and LiFOP electrolytes in MCMB/ LiNi1/3Co1/3Mn1/3O2 cells.LiPF6 and LiFOP electrolytes in natural graphite/LiFePO4 cells.

LiPF6 and LiFOP electrolytes in MCMB/LiMn2O4 cells.

LiPF4(C2O4) Electrolytes cycles well for most Anode/Cathode pairs

Formation cycle irreversible capacity differences not observed for all cells

Cycles well with PC

0 5 10 15 20 25 300.0000

0.0004

0.0008

0.0012

0.0016

0.0020

0.0024

Disc

harg

e Ca

paci

ty, A

h

Cycle Number (n)

LiNi1/3Co1/3Mn1/3O2 with LiPF6 in EC/EMC (3/7) LiNi1/3Co1/3Mn1/3O2 with LiFOP in EC/EMC (3/7)

8

FY 10 Technical Accomplishments –Commercially Viable Synthesis of LiPF4(C2O4)• We have been

investigating the novel lithium salt LiPF4(C2O4) for use in lithium ion battery electrolytes.

• The salt has been investigated in our laboratory by BATT investigators (V. Battaglia, LBNL), and companies under confidential non-disclosure agreements.

• The development of a commercially viable process has focused on PF5 delivery methods and purification optimization

8

O

O

OLi

OLiLi++ 2 x PF5 + LiPF6PO

O FF

F

FO

O

LiPF4(C2O4) is synthesized via the reaction of PF5 with lithium oxalate. We have investigated several methods of synthesis and purification resulting in significantly higher yields of purified material (> 60 %).

We are currently working with industrial partners to analyze commercial viability of this salt and synthetic process under NDA.

9

FY 11 Technical Accomplishments –Irreversible Capacity Loss with LiPF4(C2O4)

Prepared several batches of LiPF4(C2O4) with different purity levels.

No correlation between salt purity and shoulder at 1.7 V vs Li irreversible capacity of first cycle for LiNi0.8Co0.2O2/MCMB cells.

Source of irreversible capacity is not Li2C2O4

1.0 M LiPF4C2O4 Efficiency (%)1st (C/20) 67.72nd(C/10) 97.33rd (C/10) 98.54th (C/5) 97.85th (C/5) 98.9

0 5 10 15 20 25 30 350.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

0.0 0.5 1.0 1.5 2.0 2.5 3.0

0.0 0.5 1.0 1.5 2.0 2.5 3.0

1.50

1.75

2.00

Volta

ge, V

vs.

Li/L

i+

Time, h

10


MCMB/LiNi0.2Co0.8O2NG/LiFePO4

MCMB/LiFePO4 NG/LiNi0.2Co0.8O2

First cycle irreversible capacity/shoulder at 1.7 V vs Li changes with different electrode materials.

LiPF4(C2O4) cycled with Natural Graphite (NG) anodes has nearly identical first cycle efficiency.

0 2 4 6 8

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1st efficiency 43%

reduction of oxalate

deintercalationintercalation

irreversible capacity

Volta

ge, v

s. L

i/Li+

Time, h

11

First charge-discharge curve of 1.2 M LiPF4C2O4NG/lithium metal half anode cell

First charge-discharge curve of 1.2 M LiPF4C2O4MCMB/lithium metal half cell


The first cycle irreversible capacity is dependent upon graphite structure.

Irreversible capacity loss can be reduced/eliminated by proper choice of graphite anode.

12SEMs of anodes before and after formation cycles, (top left) fresh MCMB, (top right) fresh CMS, (bottom left) MCMB after formation cycles, and (bottom right) NG after formation cycles, electrolyte composition 1.2 M LiPF4C2O4 EC/EMC (3/7, v/v)


13

C 1s, F 1s, O 1s and P 2p XPS spectra of fresh MCMB, fresh NG, cycled MCMB, and cycled NG graphite, electrolyte composition 1.2 M LiPF4C2O4 EC/EMC (3/7, v/v)

The composition of the surface films is very similar on MCMB and NG.

The surface films on MCMB are thicker as suggested by sputtering experiments.


14

FY 11 Technical Accomplishments –Cathode film forming additives for HV Spinel

C/20 charging to 4.75 & 5.30V and hold at same voltage on LNi0.5Mn1.5O4 electrode and scan (5mV/S) and hold (4.75 & 5.30V) experiment on Pt electrode in LiPF6 in 3:7 EC/EMC.

Upon subtracting the current associated with Li extraction the residual current is very similar.

The oxidation reaction of the electrolyte is similar for both surfaces.

Previous investigations uncovered the generation of polyethylene carbonate on cathode surfaces stored at high potential

0 50 100 1500.0

0.4

0.8

1.2

1.6

2.0

2.4

mAh

/cm

2

Time(hr)

4.75V (Pt) 5.30V (Pt) 4.75V(LNMO) 5.30V(LNMO)

Investigation of electrochemical

reactions

Does electrolyte react on metal oxide

surfaces at lower potential?

15


Investigation of the oxidation reaction of LiPF6 in EC/EMC with glassy carbon electrode in solution.

Collaboration with Smith and Borodin – Computational data suggests that oxidation of LiPF6 with EC generates HF

Oxidation experiments cannot detect HF (~ -17 ppm) or related species in solution by NMR.

50Hour 5.2V

30Hour 5.2V

20Hour 5.2V

19F NMR spectra of electrolyte after storage.

LiPF6 Investigation of electrochemical reactions


16

Investigate thermal reaction of electrolyte with cathode surface and Mn dissolution.

Storage of LiNi0.5Mn1.5O4 in 1.2 M LiPF6 in 3/7 EC:EMC at 80 oC for 4 days.

XPS suggests presence of electrolyte decomposition products including polyethylene carbonate, LixPFyOzLiF. (J. Electrochem. Soc. 153, A1617 (2006).

Before Storage After Storage

ICP Suggests concentration of

Mn ~1 mM

17


0 2 4 6 8 10 12 14 16 18 200.88

0.90

0.92

0.94

0.96

0.98

1.00

1.02

Disc

harg

e Ca

pcity

/Cha

rge

Capa

city

Cycle Number

TEOS LiBOB LiDFOB TMTi STD

Efficiency Plots of Additives Compared to Standard

Incorporation of cathode film forming additives improve the cycling efficiency of Li/LiNi0.5Mn1.5O4 cells cycled to 4.9 V vs Li.

(TEOS, Tetraethoxy silane; TMTi, Tetramethoxy Titanium; STD, LiPF6is 3:7 EC/EMC).

18

PVDFLi2CO3

137 136 135 134 133 132 131Binding Energy (eV)

138 137 136 135 134 133 132 131Binding Energy (eV)






690 689 688 687 686 685 684 683 682Binding Energy (eV)




535 534 533 532 531 530 529 528 527Binding Energy (eV)292 290 288 286 284 282

Binding Energy (eV)

292 290 288 286 284 282Binding Energy (eV)



Carbon Oxygen Fluorine Phosphorus

Standard

LiBOB

LiDFOB

TMTi

C-CPVDFC-O/PVDF

Metal OxideCarbonyl

Li2CO3

LiF

LiF & LixPOyFz

LixPOyFzLiPF6


XPS surface analysis suggests similar cathode film structures with and without additives. Cells cycled with LiBOB have a significant concentration of B on the surface (7 %). Cells cycled with the standard electrolyte have thicker surface films.

19

Collaborations

19

• D. Abraham (ANL, National Lab, ABRT Program): Collaborations on the investigation of novel salts, solvents and additives in lithium ion battery electrolytes.

• M. Smart (NASA JPL, National Lab, ABRT Program): Collaborations on the investigation of novel salts, solvents and additives in lithium ion battery electrolytes.

• W. Li (S. China Univ. Tech., Academic): Collaboration on the investigation of LiPF4(C2O4) and computational investigations of additives for cathode and anode film formation.

• V. Battaglia (LBNL, National Lab, BATT Program): Collaboration on performance testing of LiPF4(C2O4) electrolytes in BATT program cells.

• J. Kerr (LBNL, National Lab, BATT Program): Collaboration on the investigation of novel electrolytes.

• M. Payne (Novolyte, Industrial): Collaboration on the investigation and commercialization of novel electrolytes.

• F. Puglia, J. Gnanaraj, and B. Ravdel (Yardney, Industrial): Collaboration on testing novel electrolytes in large format cells and investigation of high voltage LNMS (7 – 12 Ah).

• G. Smith & O. Borodin (U. Utah, BATT): Collaboration on investigation of electrolyte reactions with high voltage LNMS cathodes.

• High Voltage Spinel Focus Group (LBNL)

20

• Investigate cell performance upon accelerated aging of graphite/LiNiXCo1-

2xMnXO2 with LiPF4(C2O4)/PC electrolytes compared to LiPF6 electrolytes with a focus on low temperature behavior. (FY11)

• Optimize LiPF4(C2O4) electrolytes for high temperature and low temperature performance. (FY 12)

• Develop a thorough understanding of the source of performance fade in high voltage Ni-Mn spinel cathode materials. (FY11-12)

• Develop improved cathode film forming additives for high voltage Ni-Mn spinelcathode materials. (FY 11-12)

• Investigate novel electrolytes to improve performance of Si-alloy anodes. (FY 11)

• Develop novel salts and additives for use in lithium ion batteries. (FY11 – 12)

Proposed Future Work FY 10 – FY 11

Summary Slide

21

• Investigated cell performance of LiPF4(C2O4) compared to LiPF6 in small cells with new chemistries graphite/LiMn2O4,LiNixCo1-2xMnxO2, LiFePO4 cells, or with PC electrolytes.

• Developed commercially viable synthesis for LiPF4(C2O4).

• Developed an understanding of the source of irreversible capacity loss with LiPF4(C2O4) electrolytes during formation cycling.

• LiPF4(C2O4) is a promising alternative to LiPF6.

• Developed cathode film forming additives for high voltage (>4.5 V vs Li) cathode materials.

• Studied the reaction of High Voltage Ni-Mn spinel with electrolyte.

• Cathode film forming additives can improve the performance of electrolyte at high voltage (> 4.5 V vs Li).

2222

Technical Back-Up Slides

23

FY10 Technical Accomplishments –Investigation of LiPF4(C2O4) with PC

23

0 5 10 15 20 25

0.0000

0.0002

0.0004

0.0006

0.0008

0.0010

0.0012

0.0014

0.0016

disc

harg

e ca

pacit

y/Ah

cycle numbers (n)

1.2M LiPF6 in EC/EMC (3:7)

1.2M LiFOP in PC/EMC (3:7) 1.2M LiPF6 in PC/EMC (3:7)

Use of LiPF4(C2O4) salt allows the use of PC based electrolytes. There is also less initial irreversible capacity loss.

24

296294292290288286284282280278 540 538 536 534 532 530 528 526 696 694 692 690 688 686 684 682 144142140138136134132130128126

296294292290288286284282280278 540 538 536 534 532 530 528 526 696 694 692 690 688 686 684 682 144142140138136134132130128126

296 294 292 290 288 286 284 282 280 278 540 538 536 534 532 530 528 526 696 694 692 690 688 686 684 682 144142140138136134132130128126

296294292290288286284282280278 540 538 536 534 532 530 528 526 696 694 692 690 688 686 684 682 144142140138136134132130128126

PVdFgraphitefresh

C1s O1s F1s P2p-CO2

LixPOyFz

PVdF

Std. Li2CO3LiF

1.2M LiPF6 in PC

1.2M LiFOP in PC

Binding Energy (eV)Binding Energy (eV) Binding Energy (eV)Binding Energy (eV)

Stable anode SEI is formed with LiPF6/PC

FY10 Technical Accomplishments –Investigation of LiPF4(C2O4) with PC

25

Similar anode SEI structure lithium alkylcarbonates, LiF and LixPOyFz

Cathode surface contains lithium oxalate with LiPF4(C2O4) and some LiF

296 294 292 290 288 286 284 282 280 278 540 538 536 534 532 530 528 526

296 294 292 290 288 286 284 282 280 278 696 694 692 690 688 686 684 682

296 294 292 290 288 286 284 282 280 278 696 694 692 690 688 686 684 682

540 538 536 534 532 530 528 526

540 538 536 534 532 530 528 526

LiPF6

CMSC-C

F1sO1sC1sCO2

-

C-O

C=OLixPFy

LiF

Binding Energy (eV)

LiFOP

Binding Energy (eV)

LixPOyFz

C-O

C=O

Binding Energy (eV)

296294292290288286284282280278540 538 536 534 532 530 528 526696 694 692 690 688 686 684 682 144142140138136134132130128126

540 538 536 534 532 530 528 526696 694 692 690 688 686 684 682 144142140138136134132130128126

296294292290288286284282280278 540 538 536 534 532 530 528 526

296294292290288286284282280278

144142140138136134132130128126696 694 692 690 688 686 684 682

PVdF

PVdF

P2pF1sO1sC1sFreshC-C LiFePO4(P-O)LiFePO4(P-O)

C-O LixPOyFzLixPOyFz

LiFOP

Binding Energy (eV)

LiPF6

Binding Energy (eV) Binding Energy (eV) Binding Energy (eV)

FY10-Technical Accomplishments – Investigation of LiPF4(C2O4) with Natural Graphite/LiFePO4 cells - XPS

XPS surface analysis suggests that both the anode and cathode surface films are very similar for LiPF6 and LiPF4(C2O4)

26

Thicker cathode surface film with LiPF4(C2O4), presence of lithium oxalate and less metal oxide.

(top) fresh; (middle) cycled with electrolyte of LiPF6 in EC/EMC (3:7, vol.); (bottom) cycled with electrolyte of LiFOP in EC/EMC (3:7, vol.)

Anode surfaces are different and consistent with differences in initial irreversible capacity. Presence of oxalate and less LiF with LiPF4(C2O4)

(top) fresh; (middle) cycled with electrolyte of LiPF6 in EC/EMC (3:7, vol.); (bottom) cycled with electrolyte of LiFOP in EC/EMC (3:7, vol.)

296 294 292 290 288 286 284 282 280 278 540 538 536 534 532 530 528 526 696 694 692 690 688 686 684 682

296 294 292 290 288 286 284 282 280 278 540 538 536 534 532 530 528 526 696 694 692 690 688 686 684 682

296 294 292 290 288 286 284 282 280 278 540 538 536 534 532 530 528 526 696 694 692 690 688 686 684 682 144142140138136134132130128126

PVdFCO2-

PVdF

Fresh

C-O

C=OLiPF6

C=O

LixPOyFz

LixPOyFz

C-O

LiF

LiFOP

graphite

Binding Energy (eV)Binding Energy (eV)Binding Energy (eV)Binding Energy (eV)

P2pF1sO1sC1s

296294292290288286284282280278540 538 536 534 532 530 528 526696 694 692 690 688 686 684 682

296294292290288286284282280278540 538 536 534 532 530 528 526696 694 692 690 688 686 684 682

296294292290288286284282280278 540 538 536 534 532 530 528 526696 694 692 690 688 686 684 682 144142140138136134132130128126

PVdF

PVdF

C-CFresh Mn-O

LiPF6

C=O

LiFOPC=O

C-O

Binding Energy (eV)Binding Energy (eV)Binding Energy (eV)Binding Energy (eV)

LiF

LixPOyFz

P2pF1sO1sC1s

FY10-Technical Accomplishments – Investigation of LiPF4(C2O4) with Natural Graphite/LiMnO4 cells - XPS

27

.

0 5 10 15 20 25 30 35 40 45 500.0000

0.0002

0.0004

0.0006

0.0008

0.0010

0.0012

0.0014

Disc

harg

e Ca

paci

ty (A

h)

Cycle Number

LiFOB TMTi LiBOB TEOS STD

Discharge Capacities of LiNiMnO Cathode with Various Additives

Discharge Capacities of Half Cells (Li/LiNi0.5Mn1.5O4) using 1.0M LiPF6 1:1:1 EC/DMC/EMC electrolyte with LiDFOB (2%), TMTi (0.5%), TEOS (0.5%), LiBOB (2%), & No Additive (STD). All percentages are based on weight.


development of electrolytes for lithium-ion batteries

Documents