# Presentation: 112236

## Research Needs: A Transportation Perspective

"Applied Problems
 Can Be Addressed In A Fundamental Way"

Presented to
The Workshop on Basic Research Needs for Electrical Energy Storage

Tien Q. Duong
Office of FreedomCAR & Vehicle Technologies
April 2, 2007

- "Applied Problems
-  Can Be Addressed In A Fundamental Way"
- Presented to
- The Workshop on Basic Research Needs for Electrical Energy Storage
- Tien Q. Duong
- Office of FreedomCAR & Vehicle Technologies
- April 2, 2007

## Outline

- Introduction
- PHEV Overview
- Battery (and UltraCapacitor) Status
- PHEV Battery Requirements
- Technology Development Roadmap
- Program Elements
- Research Directions and Needs
- Conclusion

## Introduction

**Steady Progress has been made over the years**
- Consumer acceptance of HEVs is partially due to the durability of the NiMH batteries.
- Cost of lithium-ion batteries for consumer electronics continues to decline – presently it is below that of NiCd and NiMH batteries.

## Introduction

- Lithium-ion is viewed as the most commercially viable chemistry for PHEVs due to its potential for much higher energy and power density.
- Further improvements are needed before a larger penetration of HEVs and PHEVs can take place into the marketplace.

## PHEV Overview Design Strategy

**PHEV Overview**** Design Strategy**

- The “all-electric” strategy leads to more petroleum displacement and less emissions with some potential performance penalty; but the cost increase for the electric power-train may not be justifiable.
- The “HEV charge-depleting” strategy leads to the same “equivalent” electric range, a slightly lower fuel economy, higher tailpipe emissions, and an affordable cost without sacrificing performance.

## PHEV OverviewBattery Operation 

**PHEV Overview****Battery Operation **

- HEV

- PHEV

- EV

- EV

- PHEV

- HEV

**Battery State of Charge (SOC)**

- HEV

- PHEV

- EV

*(Fully Charged) *

*(Fully Discharged)*

- Uncharged
- Capacity

- ~1-2 kWh, P/E = 15-20

- ~5-15 kWh, P/E = 5-18

-  >40 kWh, P/E = 2

- 0

- 20

- 40

- 60

- 80

- 100

**Battery Size (kWh)**

- Impact on battery life with these two modes of operation is not fully understood.

## Status: HEV Batteries

- Conventional lithium-ion batteries for HEVs are nearly ready for commercialization
- Gradual displacement of NiMH batteries is expected, Li-ion promises reduced cost, increased performance, and longer life.
- Major R&D focus remains on cost reduction; current cost is approximately 2 times the goal.  Additional issues include
- Life: projections of 10-15 years are based on limited data
- Abuse tolerance
- Low-temperature performance
- Emerging technologies include advanced materials
- Li4Ti5O12 and alloy composite negatives
- LiFePO4, LiMnPO4, and high voltage layered and layered-spinel positives

## Status: HEV Batteries Power / Available Energy

- Power level decreases with time
- Energy window at constant power decreases with time

## Status: EV Batteries

- Lithium batteries for EVs are far from commercialization
**Lithium metal polymer** suffers from poor cycle life.  A stiffer solid polymer electrolyte with significantly improved ionic conductivity at room temperature is required.
**Lithium sulfur** is still immature. Improved lithium and sulfur utilization is needed to improve cycle life.  No practical cells have been built for evaluation.
- Major R&D is focused on suppressing dendrite formation and stabilizing the lithium interphase
- Additional barriers include cost, low specific energy and poor cycle and calendar life.
- Gradual advances in energy density and performance are planned, permitting evolution from HEVs, to PHEVs, to EVs.
- Emerging technologies include
- Composite electrolytes with a hard non-conducting component and a softer conducting component.

## Status: EV Batteries

- Power Fading at 80% Depth of Discharge Limits Battery Life

## Status: UltraCapacitors

- Currently funded development is limited to symmetric EDLCs for micro hybrids
- Technologies with acetonitrile and propylene carbonate solvents are being considered.
- Systems utilizing acetonitrile solvent have better power performance.
- Current ultracapacitors are approaching the USABC 42V Start/Stop performance requirements of life, weight and volume.
- Advantages**:** High power, performance not affected by low temperatures, long cycle and calendar life
- Issues
**Cost:** Projected to cost 2-4 times the USABC 42V goal.
**Energy density:** Restricts use in automotive applications, 30 Wh system requires ~13 liters (< 3 Wh/l and < 3 Wh/kg).
- Research direction and current efforts
- Lower cost carbon
- Novel low cost cell and module packaging
- Higher voltage carbon and electrolyte

##   Status: Abuse Tolerance

- Lithium-ion batteries can be made abuse tolerant for vehicle applications
- Cell, modules, and battery level electronic and mechanical controls are necessary.
- Well-designed thermal management at the module and battery levels is critical to mitigate thermal runaway (and extend life).
- These components add **cost, weight, and volume**.  Thus, improved inherent abuse tolerance is desired.
- Current Activities
- Laboratories perform cell and component (positive, negative, etc.) level investigations to determine operational limits of current technology.
- Laboratories and universities investigate material stabilities.
- Fundamental Question:
*How can material properties be modified to maintain high power and energy, but with significantly enhanced thermal conductivity to help alleviate thermal runaway risks?*

## USABC Goals for Advanced Batteries for PHEVs 

| Power requirements are set to allow an all-electric operation under Urban Dynamometer Driving Schedule (UDDS) 
in charge-depleting mode |  |  |  |
| --- | --- | --- | --- |
| 
Characteristics at EOL (End of Life) |  | High Power/ Energy Ratio Battery | High Energy/ Power Ratio Battery |
| Reference Equivalent Electric Range | miles | 10 | 40 |
| Peak Pulse Discharge Power - 2 Sec / 10 Sec | kW | 50 / 45 | 46 / 38 |
| Peak Regen Pulse Power (10 sec) | kW | 30 | 25 |
| Available Energy for CD (Charge Depleting) Mode, 10 kW Rate | kWh | 3.4 | 11.6 |
| Available Energy for CS (Charge Sustaining) Mode | kWh | 0.5 | 0.3 |
| Minimum Round-trip Energy Efficiency (USABC HEV Cycle) | % | 90 | 90 |
| Cold cranking power at -30°C, 2 sec - 3 Pulses | kW | 7 | 7 |
| CD Life / Discharge Throughput | Cycles/MWh | 5,000 / 17 | 5,000 / 58 |
| CS HEV Cycle Life, 50 Wh Profile | Cycles | 300,000 | 300,000 |
| Calendar Life, 35°C | year | 15 | 15 |
| Maximum System Weight | kg | 60 | 120 |
| Maximum System Volume | Liter | 40 | 80 |

## Technology Development Roadmap

**Commercialized**

- 10

** ****Phase 1: Materials **
**Development **

**Phase 2: Cell**
**Development **

** ****Phase 3: Battery**
**Development **

** ****Phase 4: Cost**
**Reduction**

**Intermediate term**

**Long-term, exploratory**

**Near market-ready**

- 4

- 5

- 6

- 7

- 1

- 2

**Commercialization**

**Li Metal Polymer**
**Li/Sulfur system**
**Li alloy/high V TMO system**
**Li titanate/Mn spinel**
**         ****- **Enerdel

**Graphite/Mn spinel  **
**         ****- **CPI/LG Chem
**Graphite/Iron phosphate**
-          - A123Systems
**Graphite/Nickelate**
-           - Johnson Controls - Saft

**Ultracapacitors**
-           - Nesscap, Maxwell
**Low cost separators**
-          - Celgard, UMT, AMS
**NiMH**
-          - Cobasys, Saft, Varta

_***Cost Goals***_

- 3

_***Research Goals***_

## Program Elements

- Cost-shared development activity with industry leading to full battery systems
- Benchmark and assess existing and candidate battery technologies
- Assist battery developers to overcome barriers for high power Li-ion batteries
- Innovative, cutting-edge long term research to understand and solve life and performance limitations of mid-term technologies

## Research Directions

- Interphase Studies
- Continue search for better membranes or glasses
- Continue search for the cause of high interfacial resistance
*What is the composition of the SEI, how might it change with aging, and what should comprise an ideal and stable SEI?*
- Electrolytes
- High voltage electrolytes (4.5 – 5 Volts)
- Solid polymer electrolytes
*What should a non-flammable electrolyte (with performance similar to today’s materials) contain?*
- Positive Electrode Material
- Next-generation olivine, layered, and spinel structures** **
*What new materials/structures should be considered for high capacity positive materials (>250 mAh/g)?*
- Negative Electrode Material
- Novel inter-metallic alloys and new binders** **
- Nanophase metal oxides
*How can the volume changes inherent in high-energy alloys be accommodated or reduced?*

## Conclusion

- We look forward to continued collaboration with our Basic Energy Sciences colleagues to
- Discover new solutions to existing problems, and
- Apply new discoveries in material and chemical sciences that will result in major breakthroughs.