materials chemistry to advance na-batteries -...

Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned

subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Materials Chemistry to Advance Na-Batteries

Erik D. Spoerke

Leo Small, Stephen Percival, Josh Lamb,

Paul Clem, and David Ingersoll

Sandia National Laboratories, Albuquerque, NM

DOE Office Electricity Delivery and Energy Reliability 2017 Peer Review

San Diego, CA October 9-10, 2017

Sai Bhavaraju and Alexis Eccleston

Ceramatec, Inc. Salt Lake City, UT

Teaming

2

▪ Program Sponsor▪ Dr. Imre Gyuk – Program Manger, DOE-OE

▪ DOE – Office of Electricity Delivery and Energy Reliability

▪ Team▪ SNL: Erik Spoerke, Leo Small, Jill Wheeler, Paul Clem, Josh Lamb, Eric

Allcorn, Ganesan Nagasubramanian, John Hewson, and David Ingersoll

▪ Ceramatec/Field Upgrading: Sai Bhavaraju, Alexis Eccleston, Andrew Read, Matt Robins

▪ SK Innovation: Jeongsoo Kim

This collaboration between National Laboratory and Industry aims to utilize state of

the art expertise in materials chemistry, electrochemistry, and advanced

characterization to enable development of new sodium-based batteries.

Critical need for Grid Scale Batteries

3

Safe, grid-scale electrical

energy storage is critical!

• Renewable/Remote

Energy

• Grid Reliability/Agility

• Humanitarian Efforts

• National Defense

Challenges with Current Battery Technologies

4

Pb-Acid: Pb + PbO2 + 2H2SO4 2PbSO4 + 2H2O Ecell ~ 2.1V

• Utilizes lead and sulfuric acid (hazardous, heavy)

• Overcharging (high charging voltages) produces potential explosion hazard from accumulation of

hydrogen and oxygen

• Capacity fades quickly from sulfation and grid corrosion (typically 200-300 cycles)

E. Krieger, et al. (2013) Energy 60. 492-500.


5

Li-ion: LiC6 + CoO2 C6 + LiCoO2 Ecell ~ 3.6V

• Cost (decreasing recently)

• Limited operational temperature range (near room temperature)

• Capacity fades relatively quickly (~500 cycles) from oxidation reactions, electrolyte degradation,

cathode degradation, increased cell resistance, cell short circuits

• Significant safety concerns associated with thermal runaway and flammable organic electrolytes

E. Krieger, et al. (2013) Energy 60. 492-500.


6

Cell Phone Laptop Computer Tesla EV Battery Battery Recycling Plant

<10Wh <100Wh kWh (~6895 18650 cells) MWh (?)

Li-ion: LiC6 + CoO2 C6 + LiCoO2 Ecell ~ 3.6V

• Cost (decreasing recently)

• Limited operational temperature range (near room temperature)

• Capacity fades relatively quickly (~500 cycles) from oxidation reactions, electrolyte degradation,

cathode degradation, increased cell resistance, cell short circuits

• Significant safety concerns associated with thermal runaway and flammable organic electrolytes


7

Na-S Batteries : 2Na + 4S Na2S4 Ecell ~ 2V

• Cost (potentially feasible)

• Operates at elevated temperatures (270-350oC – required for molten chemistry and solid state

electrolyte operation). Cell freezing can cause mechanical failure.

• Corrosive, toxic chemistries

• Molten sodium and molten sulfur are highly reactive (cascading thermal runaway and fire hazard)

September, 2011: Fire at the Tsukuba

Plant (Joso City, Ibaraki Prefecture).

Failure of single cell (out of 15,360

cells) led to short circuit and cascading

thermal runaway.

February, 2010: Fire at the Oyama Plant

(Oyama City) of Takaoka Electric Mfg.

Co., Ltd.

February, 2005: Fire at NGK's NAS

battery plant in Komaki City. Fire broke

from modular battery undergoing high-

voltage testing.

Sodium-Based Batteries: A Path to Safe, Reliable, Cost-Competitive Energy Storage

8

• Sodium-bromine: Na + ½ Br2 Na+ + Br-

• Sodium-iodine: Na + ½ I2 Na+ + I-

• Sodium-nickel chloride: Na + ½ NiCl2 Na+ + Cl- + Ni(s)

• Sodium-copper iodide: Na + CuI2- Na+ +2I- + Cu(s)

Our approach stands to enable numerous new Na-based battery technologies:

• Sodium-air

• Sodium-ion

• Aqueous Redox Flow

• Low temperature sodium-sulfur

Objective: We aim to enable development of low cost, long lifetime, low

temperature, safe, nonflammable alternatives to Na-S and Li-ion batteries.

• Low cost (reduced material costs, low CAPEX, high cycle life)

• Target unit cost < $100/kWh,

• Cycle life 5,000-10,000 cycles

• LCOS $0.05-0.10/kWh-cycle

• Enabled by low to intermediate temperature (<200oC) ceramic Na-ion conductor (NaSICON)

• Robust physical barrier - no electrode crossover!

• Reduced operating costs

• Lower cost materials/seals

• Engineered safe

• Fully inorganic, no volatile organic electrolytes

• Robust ceramic separator isolates anode and cathode

• Cross-reaction generates benign byproducts

NaSICON tube separator enables lower

temperature operation

Molten salt catholyte

Na-NiCl2 battery• Salt: NiCl2/AlCl3

Na-I2 battery• Salt: NaI/AlCl3

Our Goal: to develop low cost (≤ $100/kWh), intermediate temperature (≤200C),

long-lifetime, safe, nonflammable Na-based alternatives to

Na-S, Pb-acid, and Li-ion batteries.

• Na-chemistry utilizes abundant Na-supply

• Intermediate temperature enabled by highly

conductive NaSICON (Sodium Super Ion

CONductor) ceramic separator.

✓ High Na-conductivity (>10-3 S/cm at 25oC)

✓ Scalable production

✓ Demonstrated up to 250Wh prototypes

Sodium-nickel chloride (195oC, Ecell~2.6V):

Na + ½ NiCl2 Na+ + Cl- + Ni(s

Sodium-iodine (120-150oC, Ecell~ 3.25V):

Na + ½ I2 Na+ + I-

SNL Principal Investigator: Dr. Erik Spoerke ([email protected])

Intermediate Temperature Molten Salt Na-Based Batteries

250 Wh Nasicon tube

100 Wh,

Na-battery

prototype

9

Pre-Commercial Demonstrations of Na-NiCl2 Prototypes

10

250 Wh pre-commercial Na-NiCl2 unit cell:• operational for 3+ months

• 110 cycles (70% DOD)

• coulombic efficiency ~100%

• energy efficiency 80 %

• 53 mA/cm2 & C/7 rate

100 Wh pre-commercial Na-NiCl2 unit cell:• operational for 4+ months.

• 500+ cycles (70% DOD )

• coulombic efficiency ~100%

• energy efficiency 81.5 %

• 53 mA/cm2 & C/7 rate

30

40

50

60

70

80

90

100

110

0 50 100 150 200

Pe

rce

nta

ge(

%)

Cycles

Coulombic Efficiency

Energy Efficiency

Usable SOC

30

40

50

60

70

80

90

100

110

0 20 40 60 80 100

Pe

rce

nta

ge(

%)

Cycles

Coulombic Efficiency

Energy Efficiency

Usable SOC

NiCl2 + 2Na+ + 2e- Ni +

2NaCl

Charge

Discharge

Open Circuit Potential: 2.58V

Operating temperature: 195oC

Na-I2 Battery Technology: A Liquid Catholyte

11

Consider Na-I2 Batteries: • Increased cell voltage (3.3V*)

• Lower temperature (120-180oC)➢ Lower cost materials/seals

➢ Lower operational costs

➢ New cathode chemistries

• Liquid cathode increases feasible cycle life

I2 + 2Na+ + 2e- 2NaI

Discharge

Charge

Na-I2 Prototype Assembly

12

Lab Scale Test Conditions

• Up to 28Wh lab-scale cell

• Graphite felt + tungsten wire current

collectors

• NaI-AlCl3 based molten salt catholyte

• 1" NaSICON tube glass sealed to a-

alumina

• T = 150-180˚C

NaSICON

carbon

current

collector

in

NaI-AlCl3

molten

sodium

Na+

Na Na+ + e-

I3- + 2e-

3I-

e-

current collector

electrically insulated feedthrough

braze

stainless steel cap

welds

stainless steel can

plastic seal

alumina tube

NaSICON tube

current collector

51

Cycle Life Testing

Demonstrated long term performance

More than 300 cycles @ DOD 20%

About 200 cycles @ DOD 50%

High NaSICON current densities and C-rates

High energy efficiency of > 80%

28 WhCell

NaSICONSeparator

2 cm

NaSICON

separato

r

L.J. Small, et al. J. Power Sources (2017) 360 569-574

Overall:

2Na + I3- 2Na+ + 3I-

Cathode:

I3- +2e-

3I-

Anode:

Na Na+ + e-

13

✓ Demonstrated long term

performance across multiple

prototype scales

• Promising cycle life across battery scales

• Functional C-rates

• 28.5 mA/cm2 current density

• High energy efficiency of ~ 80%

Promise in Na-I2 Prototypes!

Data published as collaborative paper between

SNL and Ceramatec in 2017:

L.J. Small, et al. J. Power Sources (2017) 360

569-574

14

FY17 Priorities

Having effectively established proof of principle for these Na-

battery systems, our focus shifted in FY17 to emphasize:

1. Basic research and development of potential materials-based

limitations to long-term success of Na-based batteries.

2. Inherent safety of all-inorganic molten salt system.

3. Identifying a pathway to large-scale NaSICON separator

production.

15

Reconfiguring Industrial Partnerships

• In August, 2017, Ceramatec, Inc. sold its NaSICON technology to Field

Upgrading, USA.

• The core research team, including our lead collaborator (Dr. Sai Bhavaraju), will

continue work developing and implementing NaSICON.

• The primary NaSICON application emphasis will be on the large scale

extraction of sulfur from marine fuels.

• To meet these new application demands, Field Upgrading is planning a $100M

demonstration plant capable of dramatically increasing the rate of NaSICON

production: “commoditizing” NaSICON.

This scale-up of NaSICON production by Field Upgrading is expected

to substantially enable the application of NaSICON for large scale

battery production.

16

NaSICON Utilization for DSU Purification Process by Field Upgrading

Clean Seas Program: http://cleanseas.ca

17

Reconfiguring Industrial Partnerships

• In August, 2017, Ceramatec, Inc. sold its NaSICON technology to Field

Upgrading, USA.

• The core research team, including our lead collaborator (Dr. Sai Bhavaraju), will

continue work developing and implementing NaSICON.

• The primary NaSICON application emphasis will be on the large scale

extraction of sulfur from marine fuels.

• To meet these new application demands, Field Upgrading is planning a $100M

demonstration plant capable of dramatically increasing the rate of NaSICON

production: “commoditizing” NaSICON.

This scale-up of NaSICON production by Field Upgrading is expected

to substantially enable the application of NaSICON for large scale

battery production.

18

FY17 Priorities

Having effectively established proof of principle for these Na-

battery systems, our focus shifted in FY17 to emphasize:

1. Basic research and development of potential materials-based

limitations to long-term success of Na-based batteries.

2. Inherent safety of all-inorganic molten salt system.

3. Identifying a pathway to large-scale NaSICON separator

production.

19

Ultrafast Imaging with AC-STEM

a

Befored

b

c

Mn K

Mn K

Mn K

Ni K

Ni K

Ni K

TM Li TM

Mn /Ni: O:

Li/Ni:

Time-resolved atomic-scale chemical imaging

t=0.0 s

t=4.5 s

t=9.0 s

t=13.5 s

Beam exposure

Time scale

➢ Preferred jumping of Ni atoms (relative

to Mn) from the TM layers to the Li

layers

➢ Mn maintaining its position in the TM

layer

(002)

TM

0.474nm

(001)

Li

After

Using an SNL-

developed

technique for

ultrafast imaging

and chemical

mapping allows

for visualization of

atomic movement

in ion-conductive

materials.

P. Lu et al., Nano Letters 16, 2728 (2016).

20

Ultrafast Imaging with AC-STEM

Ping Lu

NaZr2P3O12

Pt

The crystal is sensitive to the

electron beam

Atomic structure (lattice

fringes) are evident in

NaSICON crystallites.

NaZr2P3O12

Initial AC-STEM imaging of local crystal planes in beam-sensitive NaSICON

highlights feasibility of ultrafast imaging of Na-movement in NaSICON.

21

✓ Demonstrated long term

performance across multiple

prototype scales

• Promising cycle life across battery scales

• Functional C-rates

• 28.5 mA/cm2 current density

• High energy efficiency of ~ 80%

Promise in Na-I2 Prototypes!

*Note that for 28 Wh (10 Ah) system,

every 11th cycle benefited from a C/15

rate to “refresh” performance.

Could this issue be related to catholyte

materials chemistry?

L.J. Small, et al. J. Power Sources (2017) 360 569-574

Can we eliminate particle phase in catholyte?

22

Toward Improved Lifetime

More Details:

Oral Presentation by Erik Spoerke (Wednesday, 10:00-12:00)

Poster Presentation by Leo Small: (Wednesday Evening 17:30-19:00)

23

PreliminaryPhaseDiagramofNaI-AlCl3Catholyte

0

50

100

150

200

250

0 25 50 75 100

Te

mp

era

ture

/ °

C

Composition / mol% NaI

Solid NaI-AlCl3

Liquid NaI-AlCl3

+

solid NaI

Liquid NaI-AlCl3

Solid � + Solid β + liquid

Solid NaI-AlCl3

NaI-AlCl3

liquid +

solid AlCl3

85 °C

115 °C

90 °C

Understanding Basic Cathode Materials Chemistry

New phase diagram created from differential scanning calorimetry data.

Leo Small and Eric Allcorn

Catholyte Compositions Tested

24


0

50

100

150

200

250

0 25 50 75 100

Te

mp

era

ture

/ °

C


Solid NaI-AlCl3

Liquid NaI-AlCl3

+

solid NaI

Liquid NaI-AlCl3


Solid NaI-AlCl3

NaI-AlCl3

liquid +

solid AlCl3

85 °C

115 °C

90 °C

Originally

demonstrated

Current

investigation

Leo Small and Eric Allcorn

Molten Catholyte Development

25

Stephen Percival and Leo Small

Molten Catholyte Desired

26


0

50

100

150

200

250

0 25 50 75 100

Te

mp

era

ture

/ °

C


Solid NaI-AlCl3

Liquid NaI-AlCl3

+

solid NaI

Liquid NaI-AlCl3


Solid NaI-AlCl3

NaI-AlCl3

liquid +

solid AlCl3

85 °C

115 °C

90 °C

Originally

demonstrated

Current

investigation

dischargecharge

27

Critical Findings of Molten NaI/AlCl3 Catholyte Studies

• Solid phase formation can be complex, involving complex processes of

particle dissolution, reagent diffusion, and electrochemical conversion.

• Solid phases can occlude electrodes, limiting current density.

• High current densities can lead to iodine bubble formation that can limit

electrode reactions.

• High NaI content yields highest current densities and Open Circuit

Potentials.

• Cycling between 50-25% NaI content at 150oC allows for functional

capacity and fully liquid catholyte performance.

Stephen Percival and Leo Small

NaSICON tube separator enables lower

temperature operation

Molten salt catholyte

Na-NiCl2 battery• Salt: NiCl2/AlCl3

Na-I2 battery• Salt: NaI/AlCl3

Our Goal: to develop low cost (≤ $100/kWh), intermediate temperature (≤200C),

long-lifetime, safe, nonflammable Na-based alternatives to

Na-S, Pb-acid, and Li-ion batteries.

• Na-chemistry utilizes abundant Na-supply

• Intermediate temperature enabled by highly

conductive NaSICON (Sodium Super Ion

CONductor) ceramic separator.

✓ High Na-conductivity (>10-3 S/cm at 25oC)

✓ Scalable production

✓ Demonstrated up to 250Wh prototypes

• Reduced temperature (relative to traditional Na-

batteries) enables:

✓ Lower cost

✓ Increased reliability and lifetime

✓ Improved capacity retention (limitation of Li-

ion and Pb-acid)

• Safety-by-design in all-inorganic system

✓ No cascading thermal runaway

✓ No flammable gas generation

✓ Separator failure and electrode cross-over

produces inert Al metal and NaCl.

Sodium-nickel chloride (195oC, Ecell~2.6V):

Na + ½ NiCl2 Na+ + Cl- + Ni(s

Sodium-iodine (120-150oC, Ecell~ 3.25V):

Na + ½ I2 Na+ + I-

Intermediate Temperature Molten Salt Na-Based Batteries

28

Safety Performance of Catholyte Salt

29

Accelerating Rate Calorimetry (ARC) Shows No Significant Exotherms

30

When complete separator failure is simulated by mixing Na metal and NaI/AlCl3catholyte, ARC testing reveals no hazardous runaway exothermic behavior!

Josh Lamb

0

50

100

150

200

250

300

350

400

450

500

0 50 100 150 200 250 300 350 400 450

No

rmal

ize

dR

ate

(°C

/min

-Ah

)

Temperature(°C)

LiCoO2/Graphite(4.2V)NCA/Graphite(4.2V)LMR-NMC/Graphite(4.4V)NMC[523]/Si-C(4.2V)NMC[523]/Graphite(4.2V)

NMC[111]/Graphite(4.2V)

0

50

100

150

200

50 150 250 350

Pre

ssu

re(

bar

)

Temperature(C)

Na-System Shows Minimal System Pressurization

31

Measuring pressure generated during ARC testing shows no significant gas

generation/pressurization from the Na-NaI/AlCl3 mixture. Even in up to 75% charge state, no

significant gas pressurization (e.g., I2 evolution) was observed.

In contrast volatile components of an NMC Li-Ion produce a dramatic pressure spike at elevated

temperatures.

NMC Li-Ion

Na-NaI/AlCl3

(Discharged, 50%

Charged, 75% Charged)

This minimal pressurization represents a dramatic safety benefit of Na-batteries.

Josh Lamb and Leo Small

32

Programmatic Accomplishments

Journal Publications:

L.J. Small, A. Eccleston, J. Lamb, A.C. Read, M. Robins, T. Meaders, D. Ingersoll, P.G. Clem, S. Bhavaraju, and E.D.

Spoerke. “Next generation molten NaI batteries for grid scale energy storage.” (2017) J. Power Sources. 360, 569-574.

L.J. Small, M.T. Brumbach, P.G. Clem, and E.D. Spoerke. “Deposition of tungsten metal by an immersion process.” (2017)

J. Electrochem. Soc. 164 (6) D269-D274.

E. Allcorn, G. Subramanian, E.D. Spoerke, and D. Ingersoll. “Elimination of Active Species Crossover in a Room

Temperature, Neutral pH, Aqueous Flow Battery using Ceramic NaSICON Membrane.” (2017) J. Power Sources, in

revision.

L.J. Small, J.S. Wheeler, J.F. Ihlefeld, P.G. Clem, and E.D. Spoerke "Enhanced Alkaline Stability in a Hafnium-Substituted

NaSICON Ion Conductor.” (2017) J. Mater. Chem. A, in review.

Patents:

E.D. Spoerke, L.J. Small, et al. “Cation-Enhanced Chemical Stability of Ion-Conducting Zirconium-Based Ceramics."

3/16/2017 U.S Patent Appl. 15/460,570.

L.J. Small, E.D. Spoerke, et al. “Electroless Process for Depositing Refractory Metals.” 12/9/2016 U.S. Patent Appl.

15/374,775.

D. Ingersoll, E. Allcorn, G. Nagasubramanian. “Aqueous Na-ion Redox Flow Battery with Ceramic NaSICON Membrane”

Prov. Pat. 62397664 (Sept, 2016).

33

Presentations:

E.D. Spoerke, L.J. Small, J. Lamb, A. Eccleston, and S. Bhavaraju. “Emerging Stationary Battery Technologies.”

(Invited) 2017 DLA Worldwide Energy Conference (04/2017) (Invited)

E.D. Spoerke, L.J. Small, J. Lamb, A. Eccleston, and S. Bhavaraju. “Enabling Next Generation Sodium-Based

Batteries with Engineered NaSICON Ion Conductors.” Electronic Materials and Applications 2017 (EMA 2017)

(01/2017)

E.D. Spoerke, L.J. Small, J. Lamb, A. Eccleston, and S. Bhavaraju. “Safety-by-Design in All-Inorganic Sodium

Batteries.” 2017 ESS Safety Forum, (02/2017)

E.D. Spoerke, L.J. Small, J. Lamb, A. Eccleston, and S. Bhavaraju. “Sodium-Based Batteries: Engineering

Interfaces for Optimized Performance.” 2017 Spring Materials Research Society Meeting (04/2017)

Conference Organization:

E.D. Spoerke - Co–organizer of Ion Conducting Ceramics symposium at Electronic Materials and Applications

2017 (an American Ceramics Society meeting). January, 2017, Orlando, FL.

E.D. Spoerke and S. Bhavaraju – Organizers for 2018 Spring Materials Research Society Meeting: “Next

Generation Solid State Super Ion Conductors.”

Programmatic Accomplishments

34

FY18 Path Forward

• Develop high surface area, chemically compatible current collector

configuration for high efficiency molten salt battery performance.

L.J. Small, et al. J. Electrochem. Soc. (2017) 164 (6) D269-D274

• Characterize relationships between microstructure, material phase, and

ion conduction in solid-state ion conducting materials (e.g. NaSICON

and related materials).

• Apply aqueous-stabilized NaSICON chemistry (SNL-developed) for

novel asymmetric aqueous battery systems.

E. Allcorn, et al. J. Power Sources (2017), in revision.

• Optimize composition and properties of molten salt catholytes for high

efficiency charge transfer processes at reduced temperatures.

• Adapt current concentric tubular battery configuration for more versatile

ceramic separator integration (e.g., ceramic plates).

• Continue to engage industrial partners to enable ultimate

commercialization of Na-Batteries.

35

Alternative Na-based Battery Chemistries

NaSICON

Membrane

Fe3+(EDT

A) –

Na2SO4Fe2+(BPY) –

Na2SO4

Cell charges at ~1.0 V

Cell discharges at ~0.8 V

Full Cell CV @ 5 mV/sec

Fe3+(EDTA) // NaSICON // Fe2+(BPY)

0.4M Na2SO4

Fe(bpy)2+/3+ (0.9V)

NaSICON separators offer the high

conductivity, chemical and mechanical

stability, and ion-selectivity needed to

enable Na-based, aqueous redox flow

batteries.


Fe Fe

Fe(EDTA)2-/3- (0V)

36

FY18 Path Forward
















Catholyte Salt

Cathode

current

collector Molten Na

Anode Current Collector

Insulating

alumina

sheath

Ceramic

pellet

Swagelok® VCR

Fitting

Na-Battery Test Platform

38

FY18 Path Forward
















Thank you!

39

Work at Sandia National Laboratories is supported by Dr. Imre

Gyuk through the Department of Energy Office of Electricity

Delivery and Energy Reliability.

Contact: Erik D. Spoerke, Ph.D.

[email protected]

Work on Na-NiCl2 batteries was performed through

collaboration between Ceramatec and SK Innovation.

Post-doctoral positions at SNL expected in FY18 for qualified candidates.

40

EESAT Presentations

Oral Presentation by Erik Spoerke

“Sodium-Based Batteries: Toward Meeting Next

Generation Challenges in Grid-Scale Energy Storage”

(Wednesday 10:00-12:00)

Poster Presentation by Leo Small:

Molten NaI-AlCl3 Catholytes for use in a Sodium Battery

(Wednesday Evening 17:30-19:00)

Backup Slides

41

42

Scanning Microwave Impedance Microscopy (SMIM)

David Scrymgeour

PrimeNano Literature

• Shielded tip for higher SNR

• Look at variation of local impedance (electrical properties – C & R, ε & σ)

• Monotonic in signal response

Demodulation on Al dots on SiO2

Z. Shen et al, Review of Sci Inst, 79, 063703, (2008)

Microwave in

Reflected

Wave

Cancellation

Coupler Amplifier Mixer

Capacitance

Resistance

Reference

Capacitance Resistance

Improving Cathode Structure

43

1 m

Carbon electrode

(graphite, powder, foam)

Intermediate coating

Convert to W-precursor

Reductive anneal creates

Crystalline, metallic tungsten.

2X Reduction in electrode resistance will reduce ASR and

enable superior electrochemical performance.

graphite

W metal

X-ray diffraction

Cyclic Voltammetry

carbon foam

10 mM K3Fe(CN)6

500 mM NaCl

100 mV/s

55

28

Electrolessly Coated Tungsten/Carbon Electrodes

inter 1

inter 2

Molten Catholyte and Carbon Felt Current Collector

44

(A) CV of a carbon felt electrode in the 40AlCl3:60NaI catholyte at 125 C and 100 mV s-1. (B) Ionic conductivity

of the 40AlCl3:60NaI catholyte and NaSICON NaS-GY as a function of temperature.

Motivated by the microscale fibers

of the carbon felt current collector,

we used a carbon microelectrode to

probe the electrochemical

properties of the catholyte salt.

NaSICON

AlCl3-NaI

Na-NiCl2 Battery Technology

45

Features of Na-NiCl2 Cell

• Open-circuit Voltage: 2.58 V• Lower Operating Temperature: 195°C• Less metal corrosion compared to NaS• Safer reaction between Na and NaAlCl4 in case of solid electrolyte

fracture

Cathode CurrentCollector

Cathode + Catholyte (Liquid

Electrolyte)

NaSICON(Solid Electrolyte)

AnodeAnode CurrentCollector

2Na+ MCl2

M

NaCl

2e- Discharge Process

NiCl2 + 2Na+ + 2e- Ni +

2NaCl

Charge

Discharge

NaSICON Electrolyte Enables Multiple Na-Battery Chemistries

46

NaSICONb” Alumina

Engineered materials chemistry and advanced, scalable processing

(Ceramatec, CoorsTek) make NaSICON a chemically/mechanically

stable, low temperature, high conductivity (>10-3 S/cm @RT)

separator technology.

Poster: S. Bhavaraju

NaSICON (Na Super Ion CONductor): Na3Zr2PSi2O12

Na-I2 Electrochemistry

47

NaSICON

carbon

current

collector

in

NaI-AlCl3

molten

sodium

Na+

Na Na+ + e-

I3- + 2e-

3I-

e-

Overall:

2Na + I3- 2Na+ + 3I-

3I- I3- + 2e- E = 2.9V vs. Na/Na+

2I3- 3I2 + 2e- E = 3.3V vs. Na/Na+

The iodine generation step is a

2-stage reaction:

150oC

10V/s

3I- I3- + 2e-

2I3- 3I2 + 2e-

Cathode:

I3- +2e-

3I-Anode:

Na Na+ + e-

*Practical OCV for

tested batteries was

2.8-2.9V

48


0

50

100

150

200

250

0 25 50 75 100

Te

mp

era

ture

/ °

C


Solid NaI-AlCl3

Liquid NaI-AlCl3

+

solid NaI

Liquid NaI-AlCl3


Solid NaI-AlCl3

NaI-AlCl3

liquid +

solid AlCl3

85 °C

115 °C

90 °C

Molten Salt Conductivity Compares with NaSICON Conductivity

NaSICON

AlCl3-NaI

Ionic

conductivity

Ionic conductivity of molten salt phase should not limit battery performance.


49


0

50

100

150

200

250

0 25 50 75 100

Te

mp

era

ture

/ °

C


Solid NaI-AlCl3

Liquid NaI-AlCl3

+

solid NaI

Liquid NaI-AlCl3


Solid NaI-AlCl3

NaI-AlCl3

liquid +

solid AlCl3

85 °C

115 °C

90 °C

Originally

demonstrated

Current

investigation

Hindered Diffusion: Solid State

50

Possible solid precipitation

observed at electrode

surface

• Hindered diffusion

from presence of

solids near electrode

Current Peaks then settles to

a lower “residual” current

SaltCrystals

ElectrodeSurface

Reactant

I-orI3-

150 °C

100 mV/s

25 mol% NaI

-0.5

0.5

1.5

2.5

3.5

4.5

5.5

6.5

7.5

2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

Cu

rren

t D

en

sit

y /

A c

m-2

Potential / V vs. Na/Na+

Current

decreases with

each scan

3I- I3- + 2e-


51


0

50

100

150

200

250

0 25 50 75 100

Te

mp

era

ture

/ °

C


Solid NaI-AlCl3

Liquid NaI-AlCl3

+

solid NaI

Liquid NaI-AlCl3


Solid NaI-AlCl3

NaI-AlCl3

liquid +

solid AlCl3

85 °C

115 °C

90 °C

Originally

demonstrated

Current

investigation

Hindered Diffusion: Gas State

52

ElectrodeSurface

I-orI3-

Reactant

I2(g)

I2(g)

Stable bubble formation

observed for very high NaI-

content salt compositions

• Rapid I2 generation

stabilizes bubbles

• Dissolution/diffusion of I2is in equilibrium with

generation rate

150°C100mV/s50mol%NaI

-2

0

2

4

6

8

10

12

14

16

2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4

Cu

rren

t D

en

sit

y / A

cm

-2

Potential / V v. Na/Na+

3I- à I3- + 2e-

Gas bubble formation

Electrochemical Performance of Catholyte

53

Highest current densities are observed at highest NaI concentrations.

There is a significant drop in current density when solid AlCl3 is formed.

Current Density at +3.05 V vs. Na/Na+

150 °C

Solid AlCl3present

Battery Potential is Modestly Affected by Catholyte Composition

54

Oxidation Potential for

3I- I3- + 2e-

180 °C

As expected, slightly higher battery operating potentials seen at higher NaI

concentrations.

materials chemistry to advance na-batteries -...

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