Development of Electrolytes for Lithium-ion Batteries · Develop novel electrolytes for lithium ion...

Development of Electrolytes for Lithium-ion Batteries

Brett Lucht University of Rhode Island

May 15th, 2013 ES067

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

2

• 04/01/2009 • 03/31/2114 • 80 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 FY12 - $147 K

• Funding for FY13 - $147 K

Timeline

Budget

Barriers

• A. Garsuch (BASF)

• Spinel Focus group (LBNL-BATT)

• F. Puglia & B. Ravdel (Yardney)

• D. Abraham (ANL)

• M. Smart (NASA JPL)

• V. Battaglia & J. Kerr (LBNL)

Partners

Overview

3 3 3

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 in

Carbonates). • Develop an understanding of the source of performance fade in

graphite/LiNi0.5Mn1.5O4 cells cycled to high voltage (4.8 V vs Li). • Develop an electrolyte formulation that allows for superior performance of

graphite/LiNi0.5Mn1.5O4 cells. • 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.

• 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

4

Milestones FY 12 • (a) Develop an understanding of the role of electrolytes in capacity fade and poor

cycling efficiency of LiNi0.5Mn1.5O4 cathodes. (March 12) Completed • (b) Design electrolyte formulations to improve efficiency (>99 %) and decrease

capacity fade (50 % of SOA) for high voltage Ni-Mn spinel cathode materials in Li/ LiNi0.5Mn1.5O4 cells. (July 12) Completed

• (c) Optimize a LiPF4(C2O4) electrolyte for graphite/LiNixCo1-2xMnxO2 cells for high and low temperature performance (50 % of SOA capacity fade). (Sept. 12) Completed

FY 13 • (a) Develop an understanding of the role of electrolyte in capacity fade for graphite/

LiNi0.5Mn1.5O4 full cells cycled at moderately elevated temperature (55 o). Completed • (b) Design electrolyte formulations to decrease cell inefficiency (50 % of SOA) and

decrease capacity fade (50 % of SOA) for graphite/LiNi0.5Mn1.5O4 full cells. July 13, on schedule

• (c) Synthesize and characterize novel non-fluorinated lithium salts and test novel electrolytes in graphite/LiNixCo1-2xMnxO2 cells. Sept 13, on schedule

5 5 5

• Investigate electrochemical properties of LiPF4(C2O4)/carbonate or ester electrolytes in small Li-ion cells.

• Investigate electrode surface films for cells cycled with LiPF4(C2O4) and LiPF6 to determine source of performance differences.

• Use computational methods to screen potentially interesting additives. • Investigate the mechanism of capacity fade for LiNi0.5Mn1.5O4

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

cathode materials. • 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.

Approach

6

• The use of the novel lithium salt lithium tetrafluorooxalatophosphate (LiPF4(C2O4), LiFOP) allows reversible cycling with PC based electrolytes with graphite anodes and both LiFePO4 and LiNi1/3Co1/3Mn1/3O2 cathode.

J. Power Sources 2012, 205, 439-448.

• Developed Cathode film forming additives

which improve the performance of Li/LiNi0.5Mn1.5O4 cells cycled to 4.9 V.

Electrochem. Solid State Lett. 2012, 15, A28-A31.

• Developed Lewis Basic/LiPF6 stabilizing

additives which improve the performance of Li/LiNi0.5Mn1.5O4 cells cycled to 4.9 V

J. Electrochem. Soc. 2012, 159, A739-A751.

Previous Technical Accomplishments

0 5 10 15 20 25 30 35 40 45 50

60

80

100

120

140

160

Effic

ienc

y, %

STD 0.5% DMMP 1% DMMP

Capa

city

, mAh

/g

Cycle Number

88

90

92

94

96

98

100

STD 0.5% DMMP 1% DMMP

0 2 4 6 8 10 12 14 16 18 20 22 24 260

20

40

60

80

100

120

140

160

180

Aged

Formed

-10oC,C/10RT,C/5-10oC,C/10RT,C/5Formation

Spec

ific D

ischa

rge C

apac

ity (m

Ah g-1

)

Cycle numbers (n)

LiPF6 LiFOP

thermal storage at 55oCfor one weekLiNi1/3Co1/3Mn1/3O2/NG

7

FY 12 Technical Accomplishments – Investigation of LiPF4(C2O4)/MB Electrolytes

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 300

20

40

60

80

100

120

140 25oC

-10oC

-30oC

-10oC

25oC

Spec

ific d

ischa

rge

capa

city

(mAh

g-1

)

Cycle numbers (n)

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

1.2 M LiPF6 in EC/EMC/MB (2:2:6, v/v)

1.2 M LiFOP in EC/EMC/MB (2:2:6, v/v)

Cycling performance for natural graphite/ LiNi1/3Co1/3Mn1/3O2 cells

was investigated.

Comparable performance before storage at 55 oC, but worse after.

0 20 40 60 80 100 1200

-5

-10

-15

-20

-25

-30

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



Z'' (

ohm

)

Z' (ohm)

Electrochemical impedance spectra after accelerated

aging.

LiFOP electrolyte has much higher impedance

-30 -20 -10 0 10 20 300

2

4

6

8

10 1.2 M LiPF6 in EC/EMC (3:7, v/v)



Cond

uctiv

ity (

mS

cm-1)

Temperature ( oC)

Ionic conductivity of electrolytes was investigated between +30 and -30oC.

LiFOP electrolyte has higher

conductivity at low temperature.

While conductivity of LiFOP is comparable to LiPF6, the interfacial films after accelerated aging have greater impedance

8

FY 12 Technical Accomplishments – Investigation of LiPF4(C2O4)/MB Electrolytes

2000 1800 1600 1400 1200 1000 800

1579 8651047

d) LiFOP in EC/EMC/MB

c) LiPF6 in EC/EMC/MB

b) LiPF6 in EC/EMC

wavenumber (cm-1)

a) Fresh NG anode

1427

IR Spectra after accelerated Aging Baseline electrolyte has Li2CO3, 1427 cm-1 . LiPF6/MB electrolyte has Li2CO3 and an additional peak at ~ 1600 cm-1 for lithium alkyl carbonates. LiFOP/MB electrolyte has Li2CO4 1640 cm-1 and 1323 cm-1, poly(ethylenecarbonate) at 1760 cm-1. XPS provides corresponding results Cathode Surface films similar

SEM Images After Accelerated aging Baseline electrolyte or the LiPF6/MB electrolyte have a thin SEI LiFOP/MB electrolyte has a much thicker film consistent with a thicker anode SEI

J. App. Electrochem. In Press

9 9

FY 13 Technical Accomplishments – Investigation of Electrolytes for HV Spinel

Preliminary investigations suggest two primary mechanisms of performance loss due to electrolyte (LiPF6 in Carbonates)

Oxidation of the electrolyte on cathode surface

Metal ion dissolution due to acidic electrolyte decomposition products

Investigation of novel electrolytes to Improve Performance of LiNi0.5Mn1.5O4 cathodes cycled to high Voltage

Cathode Film forming additives which generate a passivation layer inhibiting electrolyte oxidation

Lewis Basic Additives which inhibit Mn dissolution

0 10 20 30 40 50 60 700

20

40

60

80

100

120

140

160

Effic

ienc

y, %

Capa

city

, mAh

g-1

Cycle No.

Room Temperature

Elevated 55 oC 65

70

75

80

85

90

95

100

Very little capacity fade at RT followed by dramatic capacity

fade at 55 oC for graphite/LiNi0.5Mn1.5O4 cells

10


0 5 10 15 20 25 30 35

60

80

100

120

140

160

180

Capa

city

, mAh

g-1

Cycle No.

Cell 1 Cell 2

0

20

40

60

80

100

RT Cycling againET Cycling

Effic

ienc

y, %

Cell1 Cell 2

1.0 M LiPF6 EC/EMC (3/7)

RT Cycling

Capacity loss upon cycling Li/LiNi0.5Mn1.5O4 cells at 55 oC is minimal. Performance much better than in graphite/LiNi0.5Mn1.5O4 cells. Increased impedance is significant and efficiency is low during ET cycling. LiNi0.5Mn1.5O4 surface changing upon cycling at 55 oC.

After ET cycling Before ET cycling

11

0 10 20 30 40 50 60 70 80 90 100 110 120 1303.0

3.2

3.4

3.6

3.8

4.0

4.2

4.4

4.6

4.8

5.030th

30th

20th

20th

10th

10th

1st

1st

Cell V

olta

ge/V

Capacity/mAh.g-1

In graphite/LiNi0.5Mn1.5O4 cells capacity loss accompanied by changing voltage profiles.

Charging shoulder at 4.6 V is lost upon cycling at 55 oC


0 5 10 15 20 25 30 35 40

30

40

50

60

70

80

90

100

110

120

130

140

150

0

20

40

60

80

100

Char

ge E

fficie

ncy/

%

Disc

harg

e Ca

pacit

y/m

Ah.g

-1

Cyclic Number

ET(550C)RT

12

0 2 4 6 8 10 12 14 16 18 20 22 24 2610

20

30

40

50

60

70

80

90

100

0

10

20

30

40

50

60

70

80

90

100

Char

ge E

fficie

ncy/%

tCV=1h

tCV=13h

tCV=5h

tCV=2h

Disc

harg

e Ca

pacit

y/mAh

.g-1

Cyclic Number

Most of the capacity can be accessed for Li/ LiNi0.5Mn1.5O4 cells ,

but the rates are much lower

0 2 4 6 8 10 12 14 16 18 200

40

80

120

160

200

240

280

320

360

40

50

60

70

80

90

100

Fresh anode Anode from ET cycled cell

Cha

rge

effic

ienc

y/%

CC-CV modeCC mode

Dis

char

ge c

apac

ity/m

Ah.g

-1Cyclic Number

Fresh anode Anode from ET cycled cell


Cells were disassembled after aging. Li/ LiNi0.5Mn1.5O4 and Li/ graphite cells were prepared from the cycled electrodes

Most of the capacity cannot be accessed for Li/ graphite cells, even with

lower rates

Both electrodes contribute to performance fade

13

Electrochemical Impedance after cycling at 25 oC and after cycling at 55 oC (left) graphite/ LiNi0.5Mn1.5O4 cells; (center) Li/ graphite cells; (right) Li/ LiNi0.5Mn1.5O4 cells. Half cells were prepared from electrodes extracted from cells cycled at ET Most of the impedance growth occurs on the cathode


14 14

Surface Cross-section (SEI) Cross-section (BSI)

Fresh

Cathode

Cathode Cycled At RT

Cathode Cycled At ET

SEM images of a LiNi0.5Mn1.5O4 cathode fresh, after cycling at 25 oC (RT) and after cycling at

55 oC (ET).

Cathode particles and laminate are retained after cycling at 55 oC.

XPS spectra a LiNi0.5Mn1.5O4 cathode fresh, after cycling at 25 oC (RT) and after cycling

at 55 oC (ET).

Cycling at 55 oC results in a slight thickening of the

cathode surface film and possible decomposition of

PVDF

Mn and Ni content at surface is decreased


Plane Cross-section

Fresh

anode

Anode

Cycled

at 25 oC

Anode

Cycled

at 55 oC

15 15

SEM images of the graphite anode fresh, after cycling at 25 oC and after cycling at 55 oC.

Changes to bulk anode particles are consistent

with SEI formation

Anode experiences delamination

XPS spectra of the graphite anode fresh, after cycling at 25 oC and after cycling at 55 oC. Significant electrolyte decomposition occurs upon cycling at 55 oC, products include lithium alkyl carbonates, Li2CO3 , LiF, and LixPFyOz Mn is also present on the anode surface (ICP-MS)


16 16

Incorporation of electrolyte additive(s) results in dramatic decrease in capacity fade upon cycling at 55 oC for graphite/LiNi0.5Mn1.5O4 cells


17 17 17 17


Changes to cathode surface are small upon incorporation of additive

XPS spectra of the anode

Additive inhibits LiF formation on Anode

Mn deposition is also

inhibited, as supported by ICP-MS

18 18

Collaborations

18

• 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.

• V. Battaglia (LBNL, National Lab, BATT Program): Collaboration on performance testing of novel salts and additives in BATT program cells.

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

• A. Garsuch (BASF, Industrial): Collaboration on the development of novel electrolytes for high voltage cathodes.

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

• High Voltage Spinel Focus Group (LBNL, National Lab, BATT Program)

19 19

• Develop an understanding of the role of electrolyte in capacity fade

for graphite/ LiNi0.5Mn1.5O4 full cells cycled at moderately elevated temperature (55 o) (FY 13).

• Develop improved cathode film forming additives for graphite/ LiNi0.5Mn1.5O4 cells to improve cycling performance at 55 oC. (FY 13)

• Develop novel non-fluorinated salts for use in lithium ion batteries. (FY 13-14)

• Investigate novel electrolytes to improve performance of nanostructured Si anode materials (FY 14)

• Develop mechanistic understanding of performance limiting reactions of electrolytes in lithium ion batteries (FY 13-14)

Proposed Future Work FY 13 – FY 14

20

Summary Slide

20

• Investigated the performance of LiPF4(C2O4) electrolytes at low temperature before

and after accelerated aging.

• Developed an understanding of performance limiting reactions of LiPF4(C2O4)/ EB electrolytes at low temperature: generates thick resistive anode SEI after aging.

• Investigated the performance limiting reactions of LiNi0.5Mn1.5O4 cathodes cycled to high voltage (4.9 V vs Li)

Discovered that the two leading sources of performance fade are electrolyte oxidation and Mn dissolution/reduction on anode

Electrolyte oxidation below 4.9 V lesser contributor, thermal effects are larger contributor.

Both the anode and cathode are damaged from cycling at 55 oC.

Additives have been developed that inhibit Mn dissolution and improve performance of high voltage cathodes

Novel electrolyte formulations can improve the cycling performance of LiNi0.5Mn1.5O4 cathodes at high voltage (4.9 V vs Li)

Development of Electrolytes for Lithium-ion Batteries · Develop novel electrolytes for lithium ion...

Documents

Transcript of Development of Electrolytes for Lithium-ion Batteries · Develop novel electrolytes for lithium ion...