Slightly Fluorination of Al2O3 ALD Coating to Improve the Electrochemical

Performance of Li1.2Mn0.54Co0.13Ni0.13O2 for Lithium Ion Battery

Han Yu, and Xinhua Liang*

Department of Chemical and Biochemical Engineering, Missouri University of Science and Technology

Objectives➢ To apply AlF3-Al2O3 thin films by atomic layer deposition

(ALD) on Li1.2Mn0.54Co0.13Ni0.13O2 (Li-rich NMC) cathode

material for lithium ion battery (LIB).

➢ To improve the electrochemical performance of Li-rich

NMC including cyclic stability and voltage stability.

Problems➢ Oxygen release during the first charging process results in

thermal instability of Li-rich NMC.

➢ Phase transition from layered to spinel structure during

cycling leads to the voltage fade.

➢ Charging to high voltage aggravates the decomposition of

electrolyte.

➢ Dissolution of transition metals causes the consumption of

actives material.

Strategy

➢ Apply a thin Al2O3 film on the surface of Li-rich NMC by

ALD to suppress side reactions between electrode and

electrolyte.

➢ Apply an ultra thin AlF3 film on Al2O3 coated Li-rich NMC

by ALD to inhibit the consumption of Al2O3 by HF.

➢ Promote the structural stability and lithium diffusion

capacity of Li-rich NMC by the composite coating film, as

well as mitigate the dissolution of transition metals .

Fundamentals of ALD

Fluidized Bed ALD Reactor and ALD Coating.

.

Precursor B

Precursor A

N2To pump

Pump

Electrochemical Analysis

Conclusions

➢ A composite film consisting of AlF3 and Al2O3 was coated on

Li-rich NMC electrodes by ALD.

➢ Side reactions between the electrolyte and electrode were

suppressed, and the transformation of layered Li2MnO3 into

a spinel-like phase was mitigated.

➢ The cycling stability and voltage stability of AlF3-Al2O3coated NMC were significantly improved.

Precursor A: Al(CH3)3

Precursor B: HF-pyridine

Reaction Temperature: 100 ℃

Sample: Li1.2Mn0.54Co0.13Ni0.13O2

A: S-OH* + Al(CH3)3 → S-OAl(CH3)2* + CH4B: S-AlCH3* + H2O → S-AlOH* + CH4

Example: Alumina ALD

XPS results of F 1s of fresh and cycled UC NMC

and AlF3-Al2O3 coated NMC

➢ This work was supported in part by the National Science

Foundation.

➢ Reference:

Yu, H., Gao, Y., and Liang, X. Journal of the Electrochemical

Society, 166, A2021-A2027, 2019

0

2000

4000

6000

8000

10000

12000

14000

680682684686688690

Inte

nsit

y

Binding Energy (eV)

1AlF3-5Al2O3FreshF1s

PVDFLiF

AlF3

700

1700

2700

3700

4700

5700

6700

7700

680682684686688690

Inte

ns

ity

Binding Energy (eV)

NMC 100cyclesF1sPVDF

LixPFyOz

0

2000

4000

6000

8000

10000

12000

14000

16000

680682684686688690

Inte

ns

ity

Binding Energy (eV)

1AlF3-5Al2O3100cyclesF1s

LiAlF4

700

1700

2700

3700

4700

5700

6700

7700

8700

9700

680682684686688690

Inte

nsit

y

Binding Energy (eV)

NMC FreshF1s

PVDF

0

40

80

120

160

0 50 100 150 200

Dis

ch

arg

e C

ap

ac

ity

(m

Ah

g-1

)

Cycling Number

Li-Rich NMC

Layered structure

Spinel structure

-300

200

700

1200

1700

2200

2.5 3.0 3.5 4.0 4.5

dQ

/dV

(m

Ah

V-1

g-1

)

Voltage (V)

Oxygen Release

0

40

80

120

160

200

0 50 100 150 200

Dis

ch

arg

e C

ap

ac

ity

(m

Ah

/g)

Cycle Number

UC NMC

6Al2O3

6AlF3

1AlF3-5Al2O3

2.4

2.6

2.8

3.0

3.2

3.4

0 50 100 150

Vo

lta

ge

(V

)

Cycle Number

UC NMC6Al2O36AlF31AlF3-5Al2O3

Electrochemical Performance

20406080100120140In

ten

sit

y a

.u.

Binding Energy (eV)

UC NMC

20AlF3Al2s

Al2p

F2s

Mn3p

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

2 2.5 3 3.5 4 4.5 5

Cu

rre

nt(

mA

)

Voltage(V)

UC NMC 1st

1AlF35Al2O3 1st

-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

0.05

2 2.5 3 3.5 4 4.5 5

Cu

rre

nt(

mA

)

Voltage(V)

UC NMC 2nd

1AlF3-5Al2O3 2nd

Li-Rich NMC

Mn3+

ALDMn4+ Mn2+

Al2O3

AlF3

Li+

e-

LIBLi-Rich NMC

dQ/dV plot for the first charge-

discharge cycle of Li-rich NMC

Discharge performance and separated

discharge capacities of NMC

XPS spectra of uncoated NMC electrode

and 20AlF3 NMC electrode

Discharge performance of Al2O3 and

AlF3 coated NMC at a 1C rateDischarge voltage change of Al2O3 and

AlF3 coated NMC at a 1C rate

CV curves of the uncoated and AlF3-Al2O3 coated

NMC with a scan rate of 0.05 mV/s