Materials Design for

Grid-Scale Energy Storage

Yi Cui

Department of Materials Science and Engineering

Stanford University

Stanford Institute for Materials and Energy Sciences

SLAC National Accelerator Laboratory

Collaborator: Prof. Robert Huggins

Students: Colin Wessels, Mauro Pasta, Richard Wang, Hyun-Wook Lee

Solar Wind

Electric grid

Energy Storage: Enable Renewable Penetration

- Smooth fluctuations: seconds-to-minutes-to-hours

- Peak shifting: hours-to-days

Grid Scale Energy Storage

Life: 20-30 Years

Low-cost:

- Initial cost: <$100/kWh

- Life time cost: <$0.025/kWh cycle

Scalable (~MW-GW/plant) to TW

Cycle life: > 5000 cycles

Round trip energy efficiency: >90%

Energy density: affecting cost

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• Pumped hydroelectric power:

- Scalable, low-cost, long life.

- Location dependent, low energy density, low energy efficiency.

Electricity Energy Storage Technology Options. EPRI, Palo Alto, CA: 2010. 1020676.

Existing Storage Technologies Are Not Adequate

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1. Electricity Energy Storage Technology Options. EPRI, Palo Alto, CA: 2010. 1020676.

2. Energy Storage for the Electricity Grid: Benefits and Market Potential Assessment Guide.

Sandia National Laboratories, Albequerque, NM, and Livermore, CA: 2010. SAND2010-0815.

3. 2020 Strategic Analysis of Energy Storage in California. California Energy Commission, Sacramento, CA: 2011. CEC-500-2011-047.

Too Expensive Not Enough Cycles

Existing Electrochemical Energy Storage

Not yet scalable:

World annual Li-battery production: 40GW for 1 hr.

Need 30 years to get to 1TW scale.

Battery Basics

(Courtesy of Venkat Srinivasan)

1) Low-cost abundant materials

- Electrode

- Electrolyte

- Separators

2) 500 cycles need to go to 50,000 cycles

2) Scalable processing to make batteries

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Prussian Blue: Open Framework

Ferric ferrocyanide hydrate:

KFeIIIFeII(CN)6 ·nH2O

R P

Channel Through Framework

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Open Framework Allows Fast Ion Transport

Crystal Ionic Radius

Li+ 0.59-0.73 Å

Na+ 1.12 Å

K+ 1.52 Å

Shannon, R. D. Acta Cryst., A32, 751 (1976).

Prussian Blue analogues:

Channel radius: Rc = 1.6 Å

LiCoO2:

Channel radius: Rc = 0.43 Å

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• Open Framework Crystal Structure: APR(CN)6·nH2O

– P and R = Transition Metals, A = Alkali Ions

R P

Examples:

• Prussian Blue:

P=Fe3+ R=Fe2+

• Copper Hexacyanoferrate

(CuHCF):

P=Cu2+ R=Fe3+

• Nickel Hexacyanoferrate

(NiHCF):

P=Ni2+ R=Fe3+

A Family of Prussian Blue-Like Materials

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Synthesis of Prussian Blue Analogues

Room-temperature aqueous chemical reaction of transition metal salts. Result: spontaneous precipitation of solid product.

Example: Prussian Blue

General synthesis:

A = K+, Na+

P = Fe, Cu, Ni, Co, Mn, Zn…

R = Fe, Cr, Mn…

K Fe3 Fe II CN6

4KFeIIIFe II CN

6

A P2 RIII CN6

3APR CN

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(C. Wessels, R. Huggins, Y. Cui, Nature Communication, 2:550 (2011))

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Copper Hexacyanoferrate As Ultrafast Positive Electrodes

1 M K+ Aqueous Electrolyte:

(C. Wessels, R. Huggins, Y. Cui, Nature Communication, 2:550 (2011))

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1 M K+ aqueous electrolyte:

(C. Wessels, R. Huggins, Y. Cui, Nature Communication, 2:550 (2011))

Copper Hexacyanoferrate As Ultrafast Positive Electrodes

Also Work Well in Na+ Electrolyte

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7

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Rate Capability of Copper Hexacyanoferrate

(C. Wessels, R. Huggins, Y. Cui, Nature Communication, 2:550 (2011))

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Cycle Life of CuHCF/1 M K+ at 17C

Ultralong Cycle Life of Copper Hexacyanoferrate

(Yi Cui Group, Nature Communication, 2:550 (2011))

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Near Zero Strain: Stable Open Framework

CuHCF 400 Peak vs. Charge State CuHCF a0 vs. Charge State

400

Reason for strain: 2·∆rFe-C = 0.1 Å

∆a0 = 0.1 Å Strain = 0.1%

(Yi Cui Group, Nature Communication, 2:550 (2011))

C. Wessels, R. Huggins, Yi Cui ACS Nano, 6, 1688 (2012).

Tuning the Voltage: Cu, Ni HCF and Their Solid Solution

CuHCF Open Framework: Effects of A+ ions

C. Wessels, R. Huggins, Y. Cui, Journal of The Electrochemical Society, 159 (2) A98-

A103 (2012)

What About Negative Electrodes?

Need negative electrodes with potential ~0V versus H2/H+

time

Po

tenti

al v

s. S

HE

/ V

1.0

0.25

-0.10

(+) CuHCF

(-) Activate Carbon (AC)

(-) PPy/AC

-0.30

What About Hybrid Negative Electrodes?

(+) CuHCF

(-) 10% PPy/AC

NaBH4

[K+]=1M, pH=1, 1 C

Hybrid Negative Electrodes

M. Pasta, R. Huggins, Y. Cui Nat. Comm. (2012), In Press.

Open Framework Battery: Full Cell Potential Profile

(+) CuHCF

(-) 10%PPy-AC

([K+]=1M, pH=1, 10

C)

Full Cell

M. Pasta, R. Huggins, Y. Cui Nat. Comm. (2012), In Press.

CuHCF- PPy/C Full Battery: Cycle Life

([K+]=1M, pH=1, 10 C)

M. Pasta, R. Huggins, Y. Cui Nat. Comm. (2012), In Press.

Manganese (II) Hexacyanomanganate (III) MnIII—C≡N—MnII

Mn(II), P site

Mn (I, II, III), R site

Open Framework Structure Negative Electrodes

M. Pasta, Y. Cui (unpublished results)

CV MnIIHCMnIII, NaClO4 sat. pH=7, 2 mV/s

MnII—N≡C—MnIII/II

M. Pasta, Y. Cui (unpublished results)

Mg2+ Ca2+

What About Divalent Ion Batteries?

Sr2+ Ba2+

R. Wang, Y. Cui (unpublished results)

M+ and e-

M2+ and 2e-

Summary

- Single valent aqueous batteries: Na+, K+

- Divalent aqueous battteries: Mg2+

- Potentially low cost and scalable

- High power

- High energy efficient