Cold sintering enables recyclable composites

Enrique GomezChemical Engineering, Materials Science and Engineering, and Materials Research Institute

The Pennsylvania State University

Gomez 10/30/2020

Penn State

Can we design materials that produce less waste?

• Introduction – can we change our thinking

• Cold sintering – enabling new composites

• Recyclable materials – cold sintering as a low-energy processing and re-processing strategy

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Gomez 10/30/2020

Penn State

Solid waste is a problem

As of 2015, more than 6.9 billion tons of plastic waste has been generated

World plastic production is increasing exponentially (1/2 of all plastic ever produced was made in the last 15 yrs)

3

Global solid waste composition World Bank, 2012

nationalgeographic.com

Gomez 10/30/2020

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Where does that waste end up?

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Landfills tend to be sited around non-white populations

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Mohai and Saha, Environ. Res. Lett. 10 (2015) 115008

Gomez 10/30/2020

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Buildings are big contributors

Construction and demolition waste is 2x municipal waste

Global construction output will increase by 85% by 2030~ 1 lb of CO2 per pound of cement

Composites emerging as alternative constructure materials

Challenging to recycle

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Stuck between two choices: bury the world in solid waste,

or large increase in CO2emissions

Gomez 10/30/2020

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Battery waste is a growing problem

Between now and 2030:1

Expect 11 million metric tons of spent Li-ion batteriesNow <5% of Li-ion recycled (smelting)

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1International Energy Agency, US Department of Energy

Chevy volt battery packC&EN, 97 (28), 2019

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We have to change our thinking

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Steidle Buildingnationalgeographic.com

Research Waste

(as t → ∞)forbes.com

Products

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Opportunity: ceramic composites

Cold sintering:Sintering of ceramics and

composites near 130 oC assisted by solvent and pressure

Guo et al., Advanced Functional Materials 26 (39), 7115-7121Guo et al., Angewandte Chemie 128 (38), 11629-11633

Guo et al., ACS Nano 10 (11), 10606-10614…

Clive Randall, PSU

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Composites through cold sintering

LAGP/PVDF-HFP (80:20 by volume)Purple - Ge (LAGP)Green - F (PVDF-HFP).

Guo et al., Advanced Functional Materials 26 (39), 7115-7121

Can we achieve co-continuous morphologies?

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Gomez 10/30/2020

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Reprocessing through cold sinteringLow energy cost is enabling Co-sintering of organic and

inorganic phase is enabling

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0.01

0.1

1

10

100

1000

0.1 1 10 100

Bi4Ti3O13_laserKH2PO4_CSNaNO2_CSMgO_CSBaTiO3_CSZrO2_CSV2O5_CSZrO2_SPSBaTiO3_Sintering AidBT_Fast_FiringZrO2_FastBaTiO3_MicrowaveKH2PO4_Conven.NaNO2_Conven.

Nor

mal

ized

exc

ess

ener

gy

Power density (W/g)

LaserSintering

Cold Sintering

Furnace based sintering

(b)

From Heidary et al., J. European Ceramic Soc. 2018, 38, 1018

Ceramic-organic compositeLee et al.., Advanced Functional Materials, 2019, 29, 1807872

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Waste as inputs for structural materials

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bbc.com

Ceramic-Polymer-Salt composites

Chemical Degradation

Mechanical Degradation

Cold sintering

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Ionic Area Specific Resistance (ASR) must be lower than 5 ohm-cm2 to allow 1C rate

Ionic conductivity ~ 10-4 S/cm for 20 micron electrolyte

polymers

P. Knauth, Solid State Ionics 2009, 180, 911

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Dendrites can also grow through ceramics

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Porz et al., Adv. Energy Mater. 2017, 1701003Bachman et al., Chem. Rev. 2016, 116, 140−162

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Challenge: solid electrolyte with a combination of high conductivity, high modulus, high stability, etc.

Paul Albertus, ARPA-E

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Cold sintering of LAGP and LATP

LAGPDensity 89% of theoretical max

LATPDensity 93% of theoretical max

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380 MPa, 130 oC, 2 hrWater prior to drying: 9 wt%

620 MPa, 130 oC, 2 hrWater prior to drying: 18 wt%

Li1.5Al0.5Ge1.5(PO4)3 Li1+x+yAlxTi2−xSiyP3−yO12

Gomez 10/30/2020

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Composites with polymers enable robust thin films

40 micron free standing films, 90% LAGP, 10% PVDF~90% densityJoo-Hwan Seo, T. Mallouk, C. Randall

Tape casting Punch & LaminationBurning-out organics Humidification 70`C Cold sintering 120C

LAGPCathodeAl Foil

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Powder particle size is important, but conductivity is still too low

10-7

10-6

10-5

10-4

0 0.2 0.4 0.6 0.8 1Con

duct

ivity

(S/c

m)

Composition(fraction of 1 micron particles)

LATP (Temp : 130 oC, Pressure : 620 Mpa)

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0.4 micron particles

Gomez 10/30/2020

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LAGP dissolution is incongruent

Element Composition (norm.)

Li 1Al ~0Ge 2.53P 0.3

ICP-AES analysis(Li1.5Al0.5Ge1.5(P04)3 dissolution)

Incongruent dissolution:more dissolution of Li, Ge

Li+

Ge+4

LAGP

19 Penn State15

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Adding salt

LAGP + LiTFSI 17vol%LATP + LiTFSI 17vol%

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Porosity does not percolate for sampleswith densities of 90%

Pushed water to test whether pores traverse sample:

Water flux measurements

-2

0

2

4

6

8

10

80 82 84 86 88 90 92

Wat

er fl

ux (L

/m2 hr

bar)

Relative density (%)

6.9 bar

6.9 bar

20.7 bar(no water flux)

Suggests densities of ~ 90% required to potentially stop dendrites

LAGP

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Lithium enrichment enhances ionic conductivities

Cold sintering at 130 oC, 2 hr, 380 MPa

Approach: add LiTFSI salt to LAGP or LATP powder

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10-5

10-4

10-3

10-1 100 101 102 103 104 105 106

' (

S/cm

)

Frequency (Hz)

Lee et al., Adv. Funct. Mater. 2019, 29, 1807872

Gomez 10/30/2020

Penn State

Temperature dependence and control experiments suggest transport through solid phase crucial

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Water-in-salt electrolytes suitable for Li batteries

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Suo et al., Science 2015, 350, 941

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Moving beyond LiSICON materials

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Argon Glovebox

T = 100 oCF = 3 tonst = 1 hours

PPCLiClO4

AcetonitrileAdditives DMF

LLZO

Vacuum Chamber

Temperature-controlled plate

EIS MeasurementsCrimped into

coin cell

Al FoilSampleAl Foil

Steel Spring/Spacer

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LLZO-salt composites achieve 10-3 S/cm conductivities

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Sample σRT (S/cm)Control 4.5 x 10-4

BMT 8.98 x 10-4

SDBS 2.85 x 10-4

+ LiClO4 2.15 x 10-3

++ LiClO4 1.20 x 10-3

-6

-5

-4

-3

-2

-11 2 3 4 5

log(σ)

(S/c

m)

1000/T (K-1)

Control

BMT

SDBS

+ LiClO4

++ LiClO4

1-butyl-1-methylpyrrolidiniumtetrafluoroborate (BMT)

sodium dodecylbenzene sulfonate (SDBS)

Gomez 10/30/2020

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Re-processing LLZO composite electrolytes

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1.E‐06

1.E‐05

1.E‐04

1.E‐03

3.0

3.2

3.4

3.6

3.8

0 1 2 3 4 5 6 7 8 9 10 11cond

uctiv

ity (S/cm)

density

 (g/cm

3 )

generation

LLZO‐PPC‐LiClO4

1.E‐06

1.E‐05

1.E‐04

1.E‐03

3.0

3.2

3.4

3.6

3.8

0 1 2 3 4 5 6 7 8 9 10 11

cond

uctiv

ity (S/cm)

density

 (g/cm

3 )

generation

LLZO

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Heat treatment (170 C) improves reprocessing

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0.E+00

1.E‐04

2.E‐04

3.E‐04

4.E‐04

5.E‐04

6.E‐04

3.0

3.2

3.4

3.6

3.8

0 1 2 3 4 5 6 7 8 9 10

cond

uctiv

ity (S/cm)

density

 (g/cm

3 )

generation

With heat treatment

0.E+00

1.E‐04

2.E‐04

3.E‐04

4.E‐04

5.E‐04

6.E‐04

3.0

3.2

3.4

3.6

3.8

0 1 2 3 4 5 6 7 8 9 10 11

cond

uctiv

ity (S/cm)

density

 (g/cm

3 )

generation

Without heat treatment

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Recyclable cathode materials

Reprocessing LiFePO4 cathodes

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2.42

2.46

2.5

2.54

0.01

0.014

0.018

0.022

0 1 2 3 4

Den

sity

(g/c

m3 )

Conductivity (S/cm

)

Generation

Gomez 10/30/2020

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Summary

Cold sintering enables newceramic composites

Solid electrolyte composites exceed 10-3 S/cm ionic conductivities

Cold sintering provides a uniqueopportunity for reprocessing

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0.E+00

1.E‐04

2.E‐04

3.E‐04

4.E‐04

5.E‐04

6.E‐04

3.0

3.2

3.4

3.6

3.8

0 1 2 3 4 5 6 7 8 9 10

cond

uctiv

ity (S/cm)

density

 (g/cm

3 )

generation

With heat treatment

-6

-5

-4

-3

-2

-11 2 3 4 5

log(σ)

(S/c

m)

1000/T (K-1)

Control

BMT

SDBS

Gomez 10/30/2020

Penn State

Acknowledgements

Collaborators:

Funding:

31

Clive Randall Chao-Yang Wang