High Energy, Long Cycle Life Lithium-ion Batteries for EV Applications

Project ID: ES212

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

1The Pennsylvania State University2University of Texas at Austin

June 7, 2016

Donghai Wang1

Arumugam Manthiram2

BudgetTotal project funding: $2,425 K

• DOE share: $1,940K• Contractor share: $485KFY 2014: $1,243KFY 2015-2016: $1,182K

Timeline• Project Start – Oct. 01 2013

• Project End – Sep. 30 2016

• Overall % Complete: 85%

• FY 2016 % Complete: 60%

Barriers• Energy/power density• Cycle and calendar life• Battery component

compatibility• Abuse Tolerance

Partners• EC Power (subcontract)• Argonne National Lab

(Zhengcheng Zhang, collaboration)• Lawrence Berkley National Lab

(Gao Liu and Vincent Battaglia, collaboration)

Overview

2

Develop a lithium-ion battery system with high energy density, high power density, good cycle life, and safe operation for EV applications.

RELEVANCE – OBJECTIVES (1)

Project scope

Design and Fabrication of a lithium-ion cell:

Layered Oxide Cathode – high energy/power, stable

Advanced Silicon Alloy-carbon Anode – high energy/power, stable

Functional Binder – improve cyclability

Electrolyte – stabilize electrodes and improve safety

Performance targets

2.5 Ah cells

330 Wh/kg (770 Wh/L)

1600 W/L

Cycle life 500+ cycles

Excellent safety characteristics

Relevance

3

Project Milestones• Nickel-rich layered oxide cathodes

- Realization of Ni-rich LiNi0.7Mn0.15Co0.15O2 with high tap density (~ 2.4 g cm-3) in 1 kg batch with controlled particle size (up to 20 µm) and narrow size distribution. (complete)

- TOF-SIMS analysis reveals a multilayered SEI, active mass dissolution products, and a rock-salt phase formation. (complete)

- Surface conditioning with Mn-rich surface or other inert coatings offers a significant improvement in full-cell cyclability for large number of cycles (up to 1,600 cycles). (complete)

• Si alloy-carbon composite anodes- Design and optimization of crosslinked binders with good electrode quality and battery

performance. (complete)- Optimization and scale-up of PSU Si anode material with 150g per batch. (complete)- Scale-up electrode manufacture with 4.3 mAh/cm2 capacity and above 99.5 % coulombic

efficiency. (complete)• Electrolyte

- Improve cell safety by enhancing voltage window and electrolyte electrochemical stability. (complete)

- Develop novel fluorinated electrolytes and additives to stabilize the anode SEI, prevent electrolyte reaction at the cathode surface. (complete)

• Full Cells- TOF-SIMS analysis of a full cell after 3,000 cycles reveals that the active mass dissolution

severely affects graphite surface with SEI damage and Li plating. (complete) - Full cell performance verification with PSU Si-graphite anodes paired with NCM 523 cathodes.

(complete)- Prelithiation increases the 1st cycle efficiency to 80% in the full cells. (complete)- Optimization of the anodes, cathodes, electrolyte and prelithiation for full cells. (in progress)- Pouch cell fabrication, evaluation and delivery. (in progress) 4

Approach / Strategy• Nickel-rich layered oxide cathodes

- A co-precipitation method with a continuously stirred tank reactor (CSTR) to obtain Ni-rich layered oxides with controlled composition and surface structure.

- Advanced characterization techniques (e.g., TOF-SIMS, XPS, and HAADF-STEM) with half and full cells to understand the degradation mechanisms.

- Four surface modification methods to realize a robust cathode-electrolyte interface and realize long-term cyclabilty with full cell.

• Si-alloy carbon composite anodes- Design micro-sized Si anode materials with carbon coating to enable both good electro-

chemical performance and high tap density.- Construct conductive network at the electrode level to achieve high areal capacity.

• Functional binders- Prepare cross-linked binders to form interpenetrated conductive network to accommodate

volume change of Si and improve integrity of Si electrodes.

• Electrolytes- Design fluorinated compounds as electrolyte solvents with intrinsic oxidation stability, non-

flammability and capability of solid electrolyte interphase formation on the anode.

• Prelithiation- Apply prelithiation at pouch cells using solid Li metal particles to improve cycling efficiencies

5

Technical Accomplishments I. Degradation of Ni-rich LiNi0.7Mn0.15Co0.15O2

500 nmEDL: electrolyte decomposition layer; SRL: surface reaction layer; SSRL: surface structural reorganization layer

0 50 100 150 200

3.0

3.5

4.0

4.5

100

Baseline NCM 71515

Specific Capacity (mA h g-1)

25 oC C/5

1

Volta

ge (V

)

(a)

(c)

0 200 400 600 800 1,0000

120

240

360

480

600

20 Cycles50 Cycles100 Cycles

-Zim

ag (Ω

cm

2 )

Zreal (Ω cm2)

NMC 71515

0 20 40 60 800

15

30

45

0

1,000

2,000

3,000

4,000

5,000

0.5 1.0 1.5 2.0

"SEI"

EDLSRL

Normalized Ratio

NiO-/Ni-

MnF2-

LiF2-

Sput

terin

g Ti

me

(s)

SSRL

0

25

50

75

100

125

150

0.9 1.0 1.1 1.2 1.3

Depth (nm)

0.95 1.1 1.151.05

43.01 43.02 43.03

Mass (a. m. u.)

C2H3O-

45.01 45.02 45.03

20

100 Cycles Fresh

LiF2-

3

(e) (f)

10 μm

(g)

2 nm2 nm400 nm 20 nm

(d)

20 μm

(b)

6

Technical Accomplishments II. ToF-SIMS of cycled Ni-rich cathode (3000 cycles)

0 200 400 600 80015,000

30,000

45,000

60,000

Pristine Electrode 100 Cycles (FCG) 3000 Cycles (FCG) 3000 Cycles (FCG-Al)

Inte

nsity

(Cou

nts)

Sputtering time (s)

C2HO-

(c)

2 nm2 nm

0 50 100 150 2002.5

3.0

3.5

4.0

4.5

Pristine Al 0.75%

3.0-4.2V, 0.1C

Volta

ge /

V

Discharge capacity / mAhg-1 0 500 1000 1500 2000 2500 300060

80

100

120

140

160

180

Pristine Al 0.75%

2.7-4.3V, 1.0C 30

Disc

harg

e ca

paci

ty /

mAh

g-1

Number of cycle

0 2,000 4,000 6,000 8,0000

2,500

5,000

7,500

10,000

12,500

15,000

Pristine Electrode 100 Cycles (FCG) 3000 Cycles (FCG) 3000 Cycles (FCG-Al)

Inte

nsity

(Cou

nts)

Sputtering time (s)

MnF3-

0 2,000 4,000 6,000 8,0000.2

0.4

0.6

0.81

Pristine Electrode 100 Cycles (FCG) 3000 Cycles (FCG) 3000 Cycles (FCG-Al)

Inte

nsity

(Cou

nts)

Sputtering time (s)

60Ni-

Sample0.1C, 1st

Discharge Specific Capacity

1st

Efficiency

1C, 1st

Discharge Capacity

1C Cycle Retention

FCG 168.1 mAh/g 87.5 % 19.31 mAh 65.1% (3000th)

FCG-Al doped 162.2 mAh/g 85.9 % 17.31 mAh 83.2% (3000th)

• The organic surface deposits do not show substantial buildup as cycling proceeds (30 oC), while the corrosion products continuously accumulate

(a) (b)

(c)

(d)

(e)

Pouch-type full cell Pouch-type full cell

Cycled electrodes from Prof. Yang-Kook Sun, Hanyang Univ.

7

Technical Accomplishments III. ToF-SIMS of cycled graphite anode (3000 cycles)

(c)

2 nm2 nm

0 150 300 450 600 7500.0

0.2

0.4

0.6

0.8

1.0

C2HO-

LiF2-

MnF3-

Ni-

Li-C3

-

Norm

alize

d In

tens

ity

Sputtering Time (s)

0

150,000

300,000

450,000

600,000

750,000

C2HO-

PO2-

LiF2-

Inte

nsity

(Cou

nts)

0 150 300 450 600 7500

150,000

300,000

450,000

600,000

750,000

C2HO-

PO2-

LiF2-

Inte

nsity

(Cou

nts)

Sputtering Time (s)

0

100,000

200,000

300,000

400,000

Li-

Inte

nsity

(Cou

nts)

0 150 300 450 600 7500

100,000

200,000

300,000

400,000

Li-

Inte

nsity

(Cou

nts)

Sputtering Time (s)

0

5,000

10,000

15,000

20,000

LiO-

Ni-

MnF3-In

tens

ity (C

ount

s)

0 150 300 450 600 7500

5,000

10,000

15,000

20,000

LiO-Ni-

MnF3-In

tens

ity (C

ount

s)

Sputtering Time (s)

FCG 3000 cycles

FCG-Al 3000 cycles

• Cycled graphite also exhibits multilayer feature

• Al-doping reduces the amount of dissolution products from the cathode on the graphite surface, SEI damage, and Li plating

(a)

(b) (c) (d)

Cycled electrodes from Prof. Yang-Kook Sun, Hanyang Univ.

8

Technical Accomplishments IV. Strategies to enhance cyclability-I1. Concentration gradient with Ni-rich core and Mn-rich surface: LiNi0.75Co0.10Mn0.15O2

2. Double-coated AlF3@Li2MnO3@ LiNi0.7Co0.15Mn0.15O2

Half cell C/3 at 25 oC

5 µm

Double-coated

5 µm

Bare

0 10 20 30 40 50 60 70 80 90 1000

40

80

120

160

200

240

py

g

Cycle number

Bare20LNM-noAlF20LNM-AlF

0 20 40 60 80 100 120 140 160 1800

50

100

150

200

250

300

py

g

Cycle number

Bare

20LNM-ALFLi-rich ordering

Half cell C/3 at 25 oC

Half cell C/3 at 55 oC

9

Technical Accomplishments IV. Strategies to enhance cyclability-II

Long-term full-cell cyclability3. Li2ZrO3-coated LiNi0.7Co0.15Mn0.15O2

Zr

Good long-term cyclability has beenachieved with surface-controlled Ni-rich cathodes in pouch-type full cells

Half cell

4. Li2MnO3-integrated xLi2MnO3·(1-x)LiNi0.7Co0.15Mn0.15O2

Half cell

Half cell

10

Technical Accomplishments V. Cross-linked binders enabling fabrication of high quality Si anodes with good performance

R1 R1

R2 R2

Cross-linking

R1

R2 R2

R1

R1

R1 R2 R2

n

m

n

m

m

n

A B C

Cross-linking

AB

AB

n

AB

AB

n

AB

AB

n

C

C

Mass loading limit:4 mg/cm2 Target: 5.8 mg/cm2

PSU Si with binder I PSU Si with binder II

Electrode information: Si-Graphite anode

Electrode capacity excluding current collector: 850 mAh/g

Mass loading: 5.8 mg/cm2

Binder: PSU binder II0 10 20 30 40 50012345678

Si-graphite anode with cross-linked binder II

Are

al c

apac

ity (m

Ah/

cm

2 )

Cycle number

4.9 mAh/ cm2

11

Technical Accomplishments VI. PSU Si material scale up and electrode optimization

0 10 20 30 40 50 600

200

400

600

800

1000

1200

1400

PSU Si without additive PSU Si with additive

Cha

rge

capa

city

(mA

h/g)

Cycle number

With FECwithout FEC additive

PSU Si-graphite anodes (5.8 mg/cm2)PSU Si-graphite anodes (750 mAh/g)

PSU Si-graphite anodes (750 mAh/g, 4.3 mg/cm2)

PSU Si-graphite anodes with NCM523 (coin cells, 750 mAh/g, 4.3 mg/cm2)

0 50 100 150 2000.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

NCM523-PSU Si-Electrolyte I NCM523-PSU Si-Electrolyte II

Cap

acity

(mA

h)

Cycle number

Gen I ElectrolyteGen II Electrolyte

100 g/batch

0 10 20 30 40 50 60 70 80 900

200

400

600

800

1000

1200

Char

ge c

apac

ity (m

Ah/g

-ano

de)

Cycle number

3.3 mg/cm2 4.3 mg/cm2 5.8 mg/cm2

0 5 10 15 20 25 30 35 40 45 50 55 60 650

200

400

600

800

1000

1200

1400

Char

ge c

apac

ity (m

Ah/g

-ano

de)

Cycle number

750 mAh/g 850 mAh/g 1000 mAh/g

12

Technical Accomplishments VII. Performance verification and optimization in pouch-type full cells• NCM523 cathode – PSU Si-graphite anode with a specific capacity of 750 mAh/g

Cell information: Voltage: 4.2 / 4.3 V – 2.5 VCurrent: 100 mA/gSize: 4.4 * 5.6 cmN/P ratio: 1.2Remaining issues:Low 1st cycle efficiency of 58%Optimization of N/P ratio

0 20 40 60 80 100 120 140 160 1802.0

2.5

3.0

3.5

4.0

4.5

Volta

ge (V

)

Capacity (mAh)

1st 2nd 5th 10th 20th 50th 100th

4.2 V- 2.5 V cut-off voltage, with FEC0 20 40 60 80 100 120 140

0

20

40

60

80

100

120

140

With FEC Without FECC

apac

ity re

tent

ion

(%)

Cycle number

4.2 V- 2.5 V cut-off voltage

0 20 40 60 80 100 120 1400

20

40

60

80

100

120

140

Without FEC With FECC

apac

ity re

tent

ion

(%)

Cycle number

PSU Si anodes with the samevoltage window of 4.3 V- 2.5 V

4.3 V- 2.5 V cut-off voltage

13

VIII. Electrolyte additive development

Capacity retention of ANL electrolyte additive on PSU Si/C anode.

"! 1.0 M LiPF6 EC/EMC 3/7 +10% FEC+0.5% Additive

"! Si-C/Li half cell "! specific capacity is based on total

electrode weight

Structural formulas for TEP and TTFP additives.

Oxidation decomposition of TEP and TTFP additives.

TTFP additive impact on capacity retention of NCM/Li cell. Proposed electrocatalytic cycle of TTFP.

PSU a PSU Si G2+10% FEC PSU Si G2+10% FEC+0.5% additive

N,N-Diethyltrimethylsilylamine

14

IX. Fluorinated electrolyte development with expanded voltage window and improved performance

Comparison of capacity retention of the NCM523/graphite cells in G2 electrolyte and fluorinated electrolyte cycled between 3.0-4.6 V. Charge and discharge voltage profiles and dQ/dV

data of the optimized FEC/HF-DEC/LiPF6 electrolyte in a NCM523/graphite full cells.

15

Technical Accomplishments X. Prelithiation

Cell# Loading (mg/cm2)

TestProcedure

Theoretical Capactiy(mAh/g)

Current (mA) Electrolyte

Cathode NMC 36.759 0.05C 2 cycles then0.1C

150 2.569 for 0.05C & 5.138 for 0.1C

1M LiPF6, EC/DEC 30%FEC

Anode PSU Si 10.619 0.05C 2 cycles then0.1C

1000 2.569 for 0.05C & 5.138 for 0.1C

1M LiPF6, EC/DEC 30%FEC

12cm x 20cm SLMP coated graphite electrode

SLMP coated Si based electrode 3cm x4cm

Electrodes configuration

Coulombic efficiency of prelithiated full cell

Capacity-voltage curve of prelithiated full cell

16

Response to Reviewer Comments

Comment: “With 500 mAh/g and 3 mAh/cm2 the capacity or loading are not outstanding, it is recommended to address the potential of the Si-C approach towards higher capacities and the interaction with cycle life.” Response: We have focused on development of anode with 750 mAh/g and 4.2 mAh/cm2 and demonstrates its cycling performance in pouch-type full cells.

Comment: “The reviewer questioned that the high degradation of the cathode material down to 100 mAh/g at C/3 discharge rate after 500 cycles is critical, …and it is recommended to look in detail on the effect causing this degradation. ”Response: We have used advanced characterization techniques (e.g., TOF-SIMS, XPS and HAADF-STEM) to understand the degradation mechanism.

Comment: “The reviewer recommended prioritizing which action items give the highest output in a short time, and the highest benefit to approach the target on cell level.”Response: We have focused on evaluation and optimization at full cell level for each cell component (e.g., the cathode, anode, binder and electrolyte) and process (e.g., prelithiation) aiming to approach the technical target at pouch cells.

17

Collaboration

• Working with EC Power on design, development and testing of pouch cells.

• Working with Argonne National Laboratory on concurrent electrolyte additive development and testing for both cathodes and anodes.

• Working with Lawrence Berkeley National Laboratory on prelithiationof Si anodes and pouch cell testing.

• Independent testing of pouch cells is being conducted by Idaho National Lab.

18

Remaining Challenges and Barriers• The cyclability of Ni-rich cathodes needs to be improved while keeping the

capacity above 200 mAh/g

• Elevated temperature (e.g., 55 ºC) cycle performance needs to be improved

• Safety concerns regarding thermal runaway needs to be overcome

• Further surface optimization coupled with advanced characterization methodologies could help overcome the remaining problems in cathodes

• Key challenges in anode are to improve the 1st cycle efficiency, cycling efficiency and cycling stability of PSU Si-graphite anodes at high mass loading in full cells.

• Compatibility between electrolytes containing various additives and both cathodes and PSU Si anodes needs to be further investigated to improve cycling stability of electrodes and full cells.

19

Proposed Future Work

• Understand the role of carbon additives during the formation and evolution of cathode interphases, which is crucially related to the cell performance

• Develop further understanding of the composition-structure-performance relationship to mitigate the thermal runaway issue

• Further increase specific capacity of Si anode while maintaining good cycling efficiency and stability in high mass-loading anodes in full cells

• Using prelithiation techniques to solve the low 1st cycle efficiency issue and improve cycling stability

• The final surface-stabilized Ni-rich cathodes will be coupled with optimized PSU Si anode and electrolytes in full cells to enhance the energy density while maintaining the cycle life

20

• Ni-rich layered oxide cathodes with optimized particle size and surface structure along with high tap density (~ 2.4 g cm-3) have been produced in large quantity (1 kg per batch).

• A comprehensive understanding of the surface degradation of the cathode and graphite anode during cell cycling has been developed by employing in-depth TOF-SIMS analysis.

• Good cyclability up to 1,600 cycles with pouch-type full cells has been demonstrated with surface-controlled Ni-rich layered oxide cathodes.

• Crosslinked binders enable good electrode quality at high mass loading and cell performance for Si-based anodes.

• PSU Si anode materials scale up and optimizations of the specific capacity, mass loading, electrolyte and additive in the full cells.

• Full cell performance verification of PSU Si-graphite anodes in pouch cells.

• Development of FEC-HF DEC electrolyte and other electrolyte additives to improve stability of cathode and anode, and cycling performance of full cells.

• Prelithiatoin of PSU Si-graphite electrodes has increased the 1st cycle efficiency to 80% in pouch-type full cells.

Summary

21