Fachgebiet 3D-Nanostrukturierung, Institut für Physik

Contact: yong.lei@tu-ilmenau.de; yang.xu@tu-ilmenau.de

Office: Unterpoerlitzer Straße 38 (Heisenbergbau) (tel: 3748) http://www.tu-ilmenau.de/3dnanostrukturierung/

Vorlesung: Wedsnesday 9:00 – 10:30, C 108

Übung: Friday (G), 9:00 – 10:30, C 110

Prof. Yong Lei & Dr. Yang Xu

(a) (b2) (b1)

UTAM-prepared free-standing one-dimensional surface nanostructures on Si

substrates: Ni nanowire arrays (a) and carbon nanotube arrays (b).

Nanostrukturphysik (Nanostructure Physics)

• Class 1: a general introduction of fundamentals of nano-structured materials, and definition

• Class 2: research at 3D-Nanostructuring (01)

• Class 3: research at 3D-Nanostructuring (02)

• Class 4: graphene

• Class 5: 2D atomically thin nanosheets

• Class 6: optical properties of 1D nanostructures

• Class 7: carbon nanotubes

• Class 8: solar water splitting I: fundamentals

• Class 9: solar water splitting II: nanostructures for water splitting

• Class 10: Lithium-ion batteries: Si nanostructures

• Class 11: Sodium-ion batteries and other ion batteries

• Class 12: Solar cells

Energy storage devices:

-Batteries -Supercapacitors

Osaka et al. Journal of Power Sources, 1997, 68, 173.

More power required for short time in

200 m race.

Supercapacitors

Constant but less power required for

long time in Marathon race.

Batteries

Energy storage devices:

-Batteries -Supercapacitors

A perfect athlete?

Starting materials of commercial LIBs

• Anode: graphite (layered structure)

• Cathode: layered lithium metal oxides, e.g.

LiCoO2, LiNiO2….

• Both electrodes are layered structures, so Li-

ions can insert into/extract from the electrode

materials

• Separator: ionic conductive, not electric

conductive

• Electrolyte: non-aqueous organic, air sensitive,

moisture sensitive (glove box)

Energy Environ. Sci. 2012, 5, 7854.

Cathode Anode

First discharge of a commercial LIB

In the first discharge, the carbonates (solvent of electrolyte)

react to form a Solid-Electrolyte Interphase(SEI) layer on the

graphite electrode.

Lithiation

Existing technology

• Carbon anode (theoretical capacity 372

mAh/g for graphite)

• Lithium metal oxide or phosphate cathode

(LiCoO2, LiMn2O4, LiFePO4, theoretical

capacity 140-170 mAh/g)

Reaching its limit in energy density (per

volume, Wh/L; or per weight, Wh/kg) and

specific energy (per weight, mAh/g).

Opportunities and challenges for Si

anodes

Highest gravimetric capacity (4200 mAh/g)

Highest volumetric capacity (9786 mAh/cm3 calculated based on the

initial volume of Si)

Relatively low discharge voltage (0.4 V averagely)

Second-most abundant element in the earth’s crust and

environmental benign

A large and mature infrastructure for processing Si in industry

• Rapid capacity fading

• Large initial irreversible capacity,

i.e., low first cycle Coulombic

Efficiency (CE)

• A single crystalline-to-amorphous

phase transformation during the

first lithiation (discharging)

• Remains amorphous afterwards

Large volume changes during Li insertion and extraction:

420% volume expansion

Si particle size: 10 μm

Fundamental materials challenges to

use Si as a viable battery electrode

• Material pulverization

(volume change 420%)

• Morphology and

volume change of the

whole Si electrode

(current collector)

• Solid-electrolyte

interphase (SEI)

Nanostructured Si anodes

• Solid Si nanostructures

• Si nanowires (NWs)

• Core/shell Si NWs

• Si nanoparticles

• Hollow Si nanostructures

• Hollow Si nanostructures with clamping

Solid Si nanostructures-core-shell Si NWs (avoid pulverization)

• The core material is structurally stable and electrically conducting

• The shell material is the active Si for storing Li

Core: crystalline

Shell: amorphous

Cutoff: 150 mV Cutoff: 10 mV

J. Phys. Chem. C 2009, 113, 11390.

90% @ 100th cycle

88% capacity retention @ 6000 cycles

1000 mAh/g @ 12C

Fast charging/discharging up to 20C

Nat. Nanotechnol. 2012, 7, 309.

74% capacity retention

@ 1000 cycles

2800 mAh/g @ C/10

High CE: 99.84%

After 800 cycles

Nano Lett. 2012, 12, 3315.

Sodium-ion batteries (SIBs)

• Abundant

• Similar electrochemistry to Li system

• High ion conductivity of Na+-based electrolyte

Johnson et al. Advanced Functional Materials, 2013, 23, 947.

Cost, carbonates

Cost, current collectors at the anode

Number of publications

related to SIBs

(2014: ~250; 2015.10: ~340)

Komaba et al. Chem. Rev. 2014, 114, 11636

Goodenough et al. J. Am. Chem. Soc. 2013, 135, 1167

Tarascon et al. Science 2011, 334, 928

Komaba et al. Phys. Chem. Chem. Phys. 2014, 16, 15007

SIBs: Competitive performance

but lower cost!

Energy Environ. Sci. 2012, 5, 7854.

Cathode Anode

First discharge of a commercial LIB

Our strategies for high-performance SIBs

Defects, molecular configurations,

composites

Highly ordered arrays, 3D porous

structure Xu Y., Zhou M., Lei Y., Advanced Energy Materials (invited review

and front cover), 6 (7), DOI: 10.1002/aenm.201502514, 2016.

Electrode design ‒ highly ordered arrays

Oriented and facile pathways for electrons and Na-ions

Void spaces for restraining structural deviation of the single unit

Strong attachment to the substrate protecting from mechanical and

electrical separation

Xu Y., Zhou M., Lei Y., Advanced Energy Materials (invited review

and front cover), 6 (7), DOI: 10.1002/aenm.201502514, 2016.

Sb Ni Ni-TiO2

L. Liang, Y. Lei, et al. Energy & Environmental Science, 2015, 8, 2954;

Y. Xu, Y. Lei, et al. Chemistry of Materials, 2015, 27, 4274.

Half-cell

Full-cell

Stable output voltage (0.5 V for

half-cell and 2.9 V for full-cell)

High reversible capacity (600

mAh/g) and areal capacity (200

μAh/cm2)

Excellent rate capability (up to

20 A/g for both half- and full-

cell)

High energy and power density

for full-cell

Highly ordered Sb nanorod arrays

L. Liang, Y. Lei, et al. Energy & Environmental Science, 2015, 8, 2954.

L. Liang, Y. Lei, et al.

Energy & Environmental Science (IF 29.518), 2015, 8, 2954.

Hierarchical leaf-like Sb as high-rate SIB anode

L. Liang, Y. Lei,* et al. J. Mater. Chem. A 2017, 5, 1749.

Half-cell performance

L. Liang, Y. Lei,* et al. J. Mater. Chem. A 2017, 5, 1749.

589 mAh/g at 0.5 A/g @ 150 cycles

Hierarchy: electrode stability

Small domain: short diffusion distance

Conductive additive- and binder-free: no “dead” weight

This work

Full-cell performance

L. Liang, Y. Lei,* et al. J. Mater. Chem. A 2017, 5, 1749.

• Full-cell: Sb (anode)/Na2/3Ni1/3Mn2/3O2 (cathode) • Average output voltage: ~2.9 V • Capacity: full realization of half-cell capacity • Rate capability: as high as 10 A/g

Hierarchical Sb-Ni nanoarrays as high-rate SIB anodes

L. Liang, Y. Lei,* et al. Nano Res. 2017, DOI: 10.1007/s12274-017-1536-0.

Sb

Ni

Half-cell performance

L. Liang, Y. Lei,* et al. Nano Res. 2017, DOI: 10.1007/s12274-017-1536-0.

High percentage of pseudocapacitance shows that rate capability depends on surface-controlled process instead of diffusion-controlled process.

Full-cell performance

L. Liang, Y. Lei,* et al. Nano Res. 2017, DOI: 10.1007/s12274-017-1536-0.

Fast charging and discharging

Structural stability after 200 cycles.

95 mAh/g

35 s/charge or discharge

Y. Xu, Y. Lei, et al. Chemistry of Materials, 2015, 27, 4274.

One of the most downloaded papers

in June, 2015!

200 mAh/g @50 mA/g after 100 cycles

Highly ordered Ni-TiO2 core-shell

nanopillar arrays

Electrode design ‒ highly

ordered arrays

Electrode design ‒ 3D porous structure

Amorphous TiO2 inverse opal structure

One of the best rate capability of

TiO2-based anode so far

First realization of inverse opal

structure for SIBs

First correlation of surface ion availability with solvent

wettability for SIBs

M. Zhou, Y. Lei, et al. Nano Energy, 31, 514-524, 2017.

Material design‒defects

Utilizing oxygen vacancies in SIBs for the first time

Promoted by surface thin-layer coating

Boosting the long-term cycling capacity by 4 times

and rate capability by 10 times, comparing to the

counterpart sample without oxygen vacancies

284 mAh/g @50 mA/g, 100 cycles 174 mAh/g @ 1 A/g

Y. Xu, Y. Lei, et al. Angewandte Chemie International Edition, 2015, 54, 8768

Ultrathin Al2O3-coated MoO3-x nanosheets

Oxygen vacancies (OVs) to boost sodium-storage of amorphous SnO2 anode

Y. Xu, Y. Lei,* et al. Nano Energy 2017, 38, 304.

• Highly ordered Ni/amorphous SnO2 core/shell nanoarrays: no influence from binder and conductive additive

• Annealing in N2 atmosphere: creating OVs • Annealing in air: no OVs

Annealing in N2 Annealing in air

XPS ESR OVs

Y. Xu, Y. Lei,* et al. Nano Energy 2017, 38, 304.

Half-cell performance

• Enhanced capacity at low rates • Significantly improved rate capability • One of the best rate capabilities of SIB anodes without

conductive additive: ~200 mAh/g at 10 and 20 A/g

50 mA/g

Y. Xu, Y. Lei,* et al. Nano Energy 2017, 38, 304.

Function of OVs

Better linear relationship between log(CV peak current) and log(CV scan rate): less limitation by diffusion-controlled process of charges

Less increased impedance with changing the angular frequency: higher Na diffusion coefficient (DNa).

Y. Xu, Y. Lei,* et al. Nano Energy 2017, 38, 304.

Material design ‒ molecular configurations Extended π-conjugated system

C. Wang, Y. Lei, et al. Journal of the American Chemical Society, 2015, 137, 3124;

C. Wang, Y Lei, et al. Advanced Functional Materials, 26, 1777-1786, 2016.

Stable output voltage (discharge plateau)

High reversible capacity

Excellent fast-charge and -discharge ability (up to 10 A/g)

Long cycling life (400 cycles (SSDC) and 1500 cycles (DSR) @ 1 A/g)

Among the best performance of organic SIB materials when published

SSDC

DSR

Material design ‒ molecular configurations

Extended π-conjugated system

(Anode)

(Cathode)

SSDC

(sodium 4,4”-stilbene-dicarboxylate)

C. Wang, Y. Lei, et al. Journal of the American Chemical Society, 2015, 137, 3124;

C. Wang, Y Lei, et al. Advanced Functional Materials, 26, 1777-1786, 2016.

A selectively permeable membrane for enhancing cyclability of organic SIB electrode

C. Wang, Y. Lei,* et al. Adv. Mater. 2016, 28, 9182.

Separator with large hole size: more active material diffusing through, more dissolving

Separator with pin hole-free coating: less active material diffusing through, less dissolving

PT as model material: 5,7,12,14-pentacenetetrone

• Large size permitting ion diffusion • Severe dissolution

PEDOT:PSS complex coated glass fiber separator

• Na-ion conductive • Pin hole-free

Significantly enhanced cyclability !

C. Wang, Y. Lei,* et al. Adv. Mater. 2016, 28, 9182.

Our response to the challenge: potassium-ion batteries (PIBs)

• High abundance of K

• Close electrochemical potential (standard electrode

potential) of K (-2.92 V) to Li (-3.04 V) (better than Na -2.72 V)

• Carbon anode + Prussian blue-based cathode

Our work is the first report that represents PIBs with competitive rate capability and cyclability to LIBs using a carbon material.

Potassium Prussian blue (KPB) nanoparticles as potassium-ion battery cathode

3D framework: open channels Large interstitial sites: > 3 Å

Crystal size: 20-30 nm Domain size: ~8 nm

K0.220Fe[Fe(CN)6]0.805⋅□0.195⋅4.01H2O Great cyclability: 73.2 mAh g-1@50 cycles

C. Zhang, Y. Xu, Y. Lei,* et al. “Potassium Prussian blue nanoparticles: a low-cost cathode material for potassium-ion batteries” Adv. Funct. Mater. (back cover), 27 (4), 1604307, 2017.

First discharge of a commercial LIB

Half-cell: KPB//K Full-cell: KPB//Carbon

C. Zhang, Y. Xu, Y. Lei,* et al. “Potassium Prussian blue nanoparticles: a low-cost cathode material for potassium-ion batteries” Adv. Funct. Mater. (back cover), 27 (4), 1604307, 2017.

13.07.2017 Seite 48 http://www.tu-ilmenau.de/3d-nanostrukturierung/

Advantages: • Higher energy density than conventional capacitors;

• Higher power density than batteries;

• Very high charge and discharge rate;

• Long cycling stability.

More power required for short time in

200 m race.

P. Simon, Y. Gogotsi, Nature Materials, 2008, 7, 845.

Supercapacitors

13.07.2017 Seite 49

Principle of supercapacitors

Charge storage mechanism:

Double-layer capacitors: Ionic adsorption at the electrode/electrolyte interface.

Pseudocapacitors: Fast surface redox

reactions between electrode and electrolyte.

Prerequisites on electrode to achieve

high-performance supercapacitors:

Large specific surface area;

Low ionic/electronic transport resistance.

Template-directed 3D nanostructure arrays

with highly-ordered structure and large specific surface area are the promising building blocks for construct high-

performance supercapacitors.

13.07.2017 Seite 50

Conductive nanotube arrays for construction of supercapacitors

Large surface area for ion adsorption and surface redox reactions;

Highly-ordered porous structure to ensure good utilization of the active material and

a short ion diffusion pathway;

Conductive core to provide fast electron transport.

13.07.2017 Seite 51

AAO

ALD

Pt

Etching

Transfer

MnO2

L. Wen, Y. Lei, et al. Small, 2014, 10, 3162.

Pt@MnO2 core/shell nanotube arrays with enhanced supercapacitor

performance

13.07.2017 Seite 52

“It is the main objective of today’s research to improve the specific

energy of supercapacitors without sacrificing power and cycle life.”

Increase specific capacitance (C) New active electrode materials;

Fast electrode kinetics and efficient material utilization.

Increase potential window (V) Asymmetric device configuration.

Challenge - Increasing specific energy

13.07.2017 Seite 53

Asymmetric supercapacitors based on core/shell nanotube arrays

AAO

ALD of SnO2 in AAO

SnO2 nanotubes

MnO2 (or PPy) coated on SnO2 nanotubes

SnO2/PPy

SnO2/MnO2

Separator

F. Grote, Y. Lei, Nano Energy, 2014, 10, 63; & Journal of Power Sources, 2014, 256, 37.

13.07.2017 Seite 54

Asymmetric supercapacitors based on core/shell nanotube arrays

F. Grote, Y. Lei, Nano Energy, 2014, 10, 63; & Journal of Power Sources, 2014, 256, 37.

13.07.2017 Seite 55

A key point of nanostructures for supercapacitor applications

Mechanical stability of nanostructure arrays during

device assembling process.

Mass loading of active materials.

1. Thick-layer of active materials;

2. Increasing specific surface area of nanostructured electrode.

13.07.2017 Seite 56

AAO Nanowires/Nanotubes

H. Zhao, Y. Lei, et al. Advanced Materials, 2014, 26, 7654.

13.07.2017 Seite 57 http://www.tu-ilmenau.de/3d-nanostrukturierung/

Metallic nanopore arrays replicated from AAO

AAO

Ni nanopores

H. Zhao, Y. Lei, et al. Advanced Materials, 2014, 26, 7654.

13.07.2017 Seite 58

Ni nanopores coated with different mass loading of MnO2

13.07.2017 Seite 59

0 20 40 60 80 1000

100

200

300

400

500

600

Sp

ec

ific

ca

pa

cit

an

ce

(F

/g)

Current density (A/g)

80 g/cm2

160 g/cm2

240 g/cm2

400 g/cm2

0 1000 2000 3000 4000 50000

20

40

60

80

100

Ca

pa

cit

an

ce

re

ten

tio

n (

%)

Cycles

20 A/g

61025 61050 61075 61100 61125 61150

0,0

0,2

0,4

0,6

0,8

Po

ten

tial (V

vs A

g/A

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l)Time (s)

0 50 100 150 200 250 300 350

0.0

0.2

0.4

0.6

0.8

Po

ten

tia

l (V

vs

Ag

/Ag

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Time (s)

80 g/cm2

160 g/cm2

240 g/cm2

400 g/cm2

0.0 0.2 0.4 0.6 0.8-6

-3

0

3

6

Cu

rre

nt

(mA

)

Potential (V vs Ag/AgCl)

80 g/cm2 160 g/cm

2

240 g/cm2 400 g/cm

2

100 mV/s

Supercapacitor performance of Ni nanopores coated with MnO2

H. Zhao, Y. Lei, et al. Advanced Materials, 2014, 26, 7654.

13.07.2017 Seite 60

Ultrahigh-rate cable-type micro-supercapacitors based on polarized

TiO2 nanotubes

Vellacheri R., Lei Y, et al., Advanced Materials Technologies, in press (DOI: 10.1002/admt.201600012), 2016.

13.07.2017 Seite 61

Device assemble of cable-type micro-supercapacitors based on

polarized TiO2 nanotubes

Unpublished results

Such cable-type micro-supercapacitor with ultrahigh scan rate (200 V/s) as well as

impressive areal capacitance (0.86 F/cm2) should be beneficial for developing next-

generation flexible and/ wearable electronic devices.

Vellacheri R., Lei Y, et al., Advanced Materials Technologies, in press (DOI: 10.1002/admt.201600012), 2016.

13.07.2017 Seite 62

Supercapacitors based on Graphene

Flexible supercapacitors based on self-

stacked rGO–Co(1-x)Nix(OH)2 nanosheets

with fast electrochromic properties.

Graphene based supercapacitors for

efficient energy storage under extreme

environmental temperatures

R. Vellacheri, Y. Lei, et al. Nano Energy, 2014, 8, 231. F. Grote, Y. Lei, et al. Small, 2015, 11, 4666.

13.07.2017 www.tu-ilmenau.de/nanostruk Page 63

Wen L.Y., Lei Y., et al., Small (invited review) (frontispiece cover), 11, 3408, 2015.

Wang Z.J., Lei Y., et al., Nano Energy (invited review), 19, 328, 2016.

Zhao H., Lei Y., et al. Nano Energy (invited review), 2015,13, 790.

Xu Y., Zhou M., Lei Y.,Advanced Energy Materials (invited review), 6 (7), DOI: 10.1002/aenm.201502514, 2016.

13.07.2017 www.tu-ilmenau.de/nanostruk Page 64

1. Lei Y.*, ‘Functional Nanostructuring for Efficient Energy Conversion and Storage’, Advanced Energy

Materials (Invited Editorial), 6 (23), 201600461, 2016.

2. Wen L.Y., Zhou M., Wang. C.L., Mi Y., Lei Y.*, ‘Nanoengineering energy conversion and storage

devices via atomic layer deposition’, Advanced Energy Materials, 6 (23), 201600468, 2016.

3. Zhou M., Xu Y., Xiang J.X., Wang C.L., Liang L.Y., Fang Y.G., Wen L.Y., Mi Y., Lei Y.*,

‘Understanding the orderliness of atomic arrangement towards enhanced sodium storage’, Advanced

Energy Materials, 6 (23), 201600448, 2016.

Special issue ‘Functional Nanostructuring for

Efficient Energy Conversion and Storage’,

Advanced Energy Materials (impact

factor 15.230), 6 (23), Dec 9th, 2016.

• Class 1: a general introduction of fundamentals of nano-structured materials, and definition

• Class 2: research at 3D-Nanostructuring (01)

• Class 3: research at 3D-Nanostructuring (02)

• Class 4: graphene

• Class 5: 2D atomically thin nanosheets

• Class 6: optical properties of 1D nanostructures

• Class 7: carbon nanotubes

• Class 8: solar water splitting I: fundamentals

• Class 9: solar water splitting II: nanostructures for water splitting

• Class 10: Lithium-ion batteries: Si nanostructures

• Class 11: Sodium-ion batteries and other ion batteries

• Class 12: solar cells

Thank you!