TU Clausthal FSU Jena Beijing UT

TU Clausthal FSU Jena Beijing UT

M. Drüe1, A. Kozlov2, M. Seyring1, X. Song3, R. Schmid-Fetzer2, M. Rettenmayr1

JP09: Phase stability of alloy-type lithium storage anode materials

Phase formation in alloy-type lithium storage

anode materials with C, Si and Sn

1Otto-Schott-Institut für Materialforschung, Friedrich-Schiller-Universität Jena

2Institut für Metallurgie, Technische Universität Clausthal

3School of Materials Science and Engineering, Beijing University of Technology

TU Clausthal FSU Jena Beijing UT

electrode materials must be able to take up lithium

anode: graphite LiC6

improvement of capacity, charging time etc. needed

Motivation: Lithium Ion Battery

2

M. Winter et al., Adv. Mat. 10 (1998)

TU Clausthal FSU Jena Beijing UT

Si and Sn can take up much more Li, different Li insertion mechanism

volume expansion up to 300% still graphite used

battery-related properties strongly depend on thermodynamic data phase diagram

Anode Materials: Alternatives

3

M.N. Obrovac et al., J. Eletrochem. Soc. 154 (2007)

Sn

C

Si

Li JP 09:

TU Clausthal FSU Jena Beijing UT

combined approach of DSC, long-term annealing and XRD

Li2C2 is the only stable phase in the Li-C phase diagram, LiC6 decomposes during annealing

re-assessment of the Li-C phase diagram (TUC)

Anode Materials: Alternatives

4

Sn

C

Si

Li

JP 09:

M. Drüe et al., J. All. Comp. 575 (2013)

TU Clausthal FSU Jena Beijing UT

Si-C

Binary phase diagrams

5

Li1

7Si

4

good assessment of binary systems

investigation of the ternary phase diagram needed

Li-C Li-Si

A. Kozlov et al. Int. J. Mat Res. 101 (2013) P. Wang et al. Intermetallics 42 (2013) S. Kawanishi et al. Mat. Trans. 50 (2009)

TU Clausthal FSU Jena Beijing UT

two key compositions chosen, according to preliminary calculations 1: LiSiC 2: Li68Si25C7

DSC and long-term annealing experiments

adjustment of compositions is complicated starting materials: binary compounds

Selection of alloy compositions

6

Li13Si4+SiC+Li2C2

25°C SiC Li2C2

Li12Si7

Li17Si4

Li13Si4+SiC

TU Clausthal FSU Jena Beijing UT

Ar-filled Glovebox (O2, H2O<2ppm)

compressing of pure elements to pellets, subsequent annealing • Li+C or Li+Si Li2C2, Li12Si7, Li17Si4

XRD analysis air-tight capsule

Synthesis and characterization of Li-alloys

7

Li2C2

Li12Si7

Li17Si4

TU Clausthal FSU Jena Beijing UT

binary pre-alloys for adjustment of ternary compositions: Li2C2, Li12Si7, Li17Si4

Synthesis and characterization of Li-alloys

8

mixed in the chosen compositions for DSC and compressed to pellets for long-term annealing

subsequent XRD analysis

Li2C2

Li12Si7

Li17Si4

TU Clausthal FSU Jena Beijing UT

DSC measurements

Composition 1: LiSiC

9

α-SiC + Li12Si7 + Li2C2

fabrication of pellets

annealing: 650°C, 96h Li7Si3?

Li13Si4+SiC+Li2C2?

TU Clausthal FSU Jena Beijing UT

Composition 1: LiSiC

10

α-SiC + Li12Si7 + Li2C2

α-SiC + Li17Si4 + Li2C2

fabrication of pellets

annealing: 650°C, 96h

annealing: 630°C, 96h

Li7Si3, Li2C2 and SiC can be identified no Li13Si4?

Li13Si4+SiC+Li2C2?

TU Clausthal FSU Jena Beijing UT

Composition 2: Li68Si25C7

11

Li2C2 + Li12Si7 + Li17Si4

DSC measurements

Li7Si3

Li13Si4+SiC?

TU Clausthal FSU Jena Beijing UT

fabrication of pellets

annealing: 630°C, 96h

Composition 2: Li68Si25C7

12

Li2C2 + Li12Si7 + Li17Si4

phases identified: Li7Si3, Li2C2, little SiC (?) no Li13Si4!

Li13Si4+SiC?

TU Clausthal FSU Jena Beijing UT

first approach to investigate ternary system Li-Si-C

no ternary phases

three-phase equilibrium identified

Li7Si3 has formed during all experiments equilibrium at the studied compositions contains Li7Si3 instead of Li13Si4

Conclusion

13

Li7Si3+SiC+Li2C2

25°C Li13Si4+SiC+Li2C2?

TU Clausthal FSU Jena Beijing UT

Joint project JP 09

information about phase stabilities insufficient

sensitive Li-alloys have to be handled under protective gas (no H2O, O2, N2)

C

Sn

Si

Li

alloy fabrication

FSU Jena TU Clausthal Beijing UT

annealing experiments

microstructure characterization (XRD, LM, SEM, TEM)

thermodynamic data (DSC) nanostructuring (SPS)

phase diagrams (CALPHAD) modeling of nc-Li-alloys

TU Clausthal FSU Jena Beijing UT

Li-C: pure samples of LiC6 and Li2C2, DSC (TUC) and long-term annealing

Li2C2 is the only stable phase in the Li-C phase diagram, LiC6 decomposes during annealing

Synthesis and phase diagram: Li-C

[Kozlov2013]

re-assessment of the Li-C phase diagram (TUC)

[Okamoto1989]