High Voltage Electrolyte for Lithium Batteries

Zhengcheng Zhang, Jian Dong, Huiming Wu, A. Abouimrane, Khalil Amine

Argonne National Laboratory Vehicle Technologies Program Annual Merit Review and Peer Evaluation Meeting

Washington, D.C. June 9-13, 2011 es113

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

Timeline Barriers . Conventional carbonate based . Project start date: FY10 (new electrolyte decomposes at 4.5V project) . Low voltage operation limit energy . Project end date: FY14 density both volumetric and . Percent complete: 10% gravimetric.

Budget Partners . Total project funding . US Army Research Lab - 100% DOE funding . Center of Nanoscale Materials (ANL) ® . Funding for FY11: $200K . Daikin Chemical Company . EnerDel® Company . Project Lead – Zhang & Amine

2 Objective

 To develop an electrolyte with wide electrochemical window that can provide stable cycling performance for 5V cathode materials recently developed for high energy and high power lithium ion battery for PHEV and EV applications.

 FY10’s objective is to identify and synthesize several solvent systems as possible candidates for high voltage electrolytes.

33 Approach

Silane/Sulfone Approach  Investigate linear and cyclic sulfones as electrolyte solvents using high

voltage spinel LiNi0.5Mn1.5O4 cathode and lithium titanate oxide anode;

 Formulate various electrolytes with hybrid sulfone/silane solvents.

Fluorinated Ester/Ether Approach  Synthesize and formulate various fluorinated ester or/and fluorinated ether/carbonate electrolytes;

 Synthesize and formulate sulfone/silane/ flourinated tertiary electrolytes.

Ionic Liquids Approach  Design, synthesize functional ionic liquids with functional groups.

Electrochemical Characterizations/Evaluations  Evaluate electrolyte performance with high voltage cathodes.

4 Achievements and Progress

5 Sulfone/Silane Hybrid Electrolyte

 Sulfone based electrolyte showed excellent cycling performance in LiMn2O4/LTO and LiNi0.5Mn1.5O4/LTO cells. 1.0M LiTFSI TMS or EMS electrolytes achieved 100 cycles with no capacity fade for LiMn2O4/LTO chemistry.  Sulfone based electrolyte has an issue of wettability with polyolefin separators and electrode. Good performance was achieved by using glass fiber separator and a formation step.  Sulfone based electrolyte performance deteriorates when cycled with high C-rate.  Sulfone based electrolyte is not compatible with graphite-based anode - No SEI formation.

R1 R2 H3C O R S Si 3

O O H3C CH3

Sulfone Silane

 High oxidation potential  Medium wide electrochemical window  High to medium ionic conductivity  High ionic conductivity  Low cost  Non-flammability  High melting point for symmetrical sulfones  Excellent wetting property – narrow liquid-phase temperature  Wide liquid-phase temperature (-40~200°C)  High viscosity compared with carbonate electrolyte  Low viscosity-comparable with carbonate electrolyte

6 Tetramethylene sulfone (TMS)/Silane (1NM3)

H C H3C 2 CH2 O O CH3 H3C H2C Si O O CH2

S H3C O O TMS 1NM3

3.50 1.0M LiPF6 TMS/1NM3 9/1 1.0M LiPF6 TMS/1NM3 8/2 3.00 1.0M LiPF6 TMS/1NM3 7/3 1.0M LiPF6 TMS/1NM3 5/5

2.50

2.00

Conductivity (mS/cm) 1.50

1.00 10 20 30 40 50 60 70

Temperature (°C)

Fig. (left): Ionic conductivities versus temperature for 1.0M LiPF6 TMS/1NM3 hybrid electrolytes (Left). Fig. (right): Cyclic voltammograms of 1.0M LiPF6 TMS/1NM3 electrolytes with weight ratios of 9:1 and 5:5.

7 Charge/Discharge Profiles for Li1.2Ni0.15Co0.10Mn0.55O2/LTO Cell Using 1.0M LiPF TMS/1NM3 (5/5) Electrolyte 6

3.5 5th, 10th, 15th charge

3.0 1st charge

2.5

2.0

1.5 Voltage (V) Voltage

1.0

0.5

5th, 10th, 15th discharge 1st discharge 0.0 0 50 100 150 200 250

Capacity (mAh/g)

1st cycle charged to 3.25V as activation step; 2nd and the subsequent cycles are regular cycling: 0.5~3.1V, C/20 at room temperature 8 Charge/Discharge Profiles for LiMn2O4/LTO and Li1.2Ni0.15Co0.10Mn0.55O2/LTO with 1.0M LiPF6 TMS/1NM3 (5/5) Electrolyte

High voltage Cathode: Li1.2Ni0.15Co0.10Mn0.55O2 Anode: LTO Electrolyte: 1.0M LiPF6 TMS/1NM3 (5/5) Separator: Celgard 2325 Cut off voltage: 0.5~3.1V, Charge discharge current: C/20

250

200

150

100

Charge 50 Discharge Capacity(mAh/g) 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Cycle Number 9 Cycling Performance Using Graphite Based Anode with Electrolyte 1.0M LiPF6 TMS/1NM3 5/5

10 Differential Capacity (dQ/dV) Profiles of Electrolyte 1.0M LiPF6 TMS/1NM3 with and w/o Additives

1.0E-03 1.0E-03 1st Charge 1st Charge 1.0M LiPF TMS/1NM3 5/5 1.2M LiPF6 EC/EMC 3/7 5.0E-04 6 5.0E-04 with 2% and 4% VC dQ/dV (Ah/V) dQ/dV (Ah/V) dQ/dV 0.0E+00 0.0E+00 2 2.2 2.4 2.6 2.8 2 2.2 2.4 2.6 2.8 Voltage (V) Voltage (V)

1.0E-03 1.0E-03 st 1 Charge 1st Charge 1.0M LiPF6 TMS/1NM3 5/5 1.0M LiPF6 TMS/1NM3 5/5 5.0E-04 with 2% LiDfOB 5.0E-04 with 4% LiDfOB dQ/dV (Ah/V) dQ/dV (Ah/V) 0.0E+00 0.0E+00 2 2.2 2.4 2.6 2.8 2 2.2 2.4 2.6 2.8 Voltage (V) Voltage (V)

dQ/dV data support the Formation of New Solid Electrolyte Interphase on Graphite Anode 11 Fluorinated Solvents as High Voltage Electrolyte F O F O F F O Li O Rf1 Rf2 P O O F F F O

FEC DMC D2 LiPF6

4.0 3.5 1st charge/discharge profile 3.0 2.5 Cut off Voltage: Cathode: LiNi0.5Mn1.5O4

2.0 2.0-3.45V

1.5 Anode: Li4Ti5O12 Voltage (V) 1.0 Gen 2 electrolyte 1.0M LiPF6 FEC/DMC/D2(3/4/3) Electrolyte: 1.0M LiPF 0.5 6 FEC/DMC/D2 =3:4:3 (volume) 0.0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Capacity (mAh/g) 12 Fluorinated Solvents as High Voltage Electrolyte

13 Accelerated Cycling Performance at RT and 55oC To increase the thermal stability and reactivity Comparison of cycling stability at RT and 55oC with 2C charge/discharge rate

O O (FEC)

O Rf1 Rf2 (D2)

14 Fluorinated Solvents as High Voltage Electrolyte O F F F O O O Li O O or P O Rf1 Rf2 F F F O O O

FEC DMC/EMC D2 LiPF6

15 Collaboration and Interactions

. US Army Research Laboratory - Dr. Richard Jow and Dr. Kang Xu for technical and information exchanges; . Center of Nanomaterials -Argonne National Laboratory - Dr. Larry Curtiss for calculation of reduction/oxidation potentials of solvents by quantum chemical methods; . Daikin Chemical Company -Dr. Meiten Koh for the supply of FEC and D2 solvents and material synthesis discussions. . EnerDel - Dr. Yumoto and Naoki for high voltage spinel cathode and LTO anode and technical discussions.

16 Proposed Future Work

 Further explore sulfone/silane hybrid electrolytes

 Further explore the fluorinate ethers/carbonate hybrid electrolytes;

 Investigate the sulfone/fluorinated hybrid electrolytes;

 Continue exploring formulations based on silane/fluorinated solvents hybrid electrolyte;

 Evaluate the battery cycling performance of these high voltage electrolytes at 55oC using LiNMO/LTO chemistry;

 Study their impact on calendar and cycle life of lithium ion battery;

 Investigate their impact on safety of lithium ion battery.

17 Summary

 Sulfone/Silane hybrid system shows an increase in a voltage window stability vs. Sulfone only;

 Performance of Sulfone/Silane hybrid system using high voltage composite layered electrode shows good cycling stability;

 New additive were developed for sulfone/silane hybrid electrolyte system to enable their use in graphite anode;

 Fluorinated ether mixed with conventional electrolyte shows excellent cycling performance both at room and high temperature using high voltage LNMO spinel system as cathode and LTO as anode.