nanomaterials for enhancing electrochemical energy...

Nanomaterials for Enhancing Electrochemical Energy Storage

Wolfgang Sigmund, Rui Qing

Department of Materials Science and Engineering, University of Florida

M. Winter et al, Chemical Reviews, 104 (2004) 4245-4269.

http://www.green-and-energy.com/blog/whats-is-your-battery-size/

http://physics.ucsd.edu/do-the-math/2012/08/battery-performance-deficit-disorder/

V. Srinivasan, AIP Conference Proceedings, Volume 1044, pp. 283-296 (2008)

Ragone chart of electrochemical systems and various type of batteries:

0.01 0.1 1 10 100 1000 10000 100000

0.1

1

10

100

1000

10000

100000

1000000

1E7

Specific

Pow

er

(W/L

)

Specific Energy (Wh/L)

Capacitors

Supercapacitors

Batteries

Fuel Cells

http://www.telegraph.co.uk/technology/apple/7558319/Apple-iPad-launch-marred-by-technical-

problems

http://www.worldproutassembly.org/archives/2006/06/incentives_come.html Review: Lithium batteries: Status, prospects and future. Bruno Scrosati∗, Jürgen Garche

Schematic of a lithium ion battery cell:

Load

Electrolyte

An

od

e

Cath

od

e

Separator

Li+

Li+

Li+

Li+

Li+

e- flow

:Charging :Discharging

Y. S. Meng, Univerisity of Florida, Gainesville 2008.

Specific charge [Ah/kg] Capacity Ratio:

Anode: Cathode

Specific Energy

[Wh/kg] Anode Cathode

372 (C6) 137 (Li0.5CoO2) 2.72:1 360 (@3.6V) Standard

4200 (Si)* 137 (Li0.5CoO2) 30.65:1 478 (@3.6V) High cap. anode

372 (C6) 372 (new)* 1:1 670 (@3.6V) High cap. cathode

372 (C6) 137 (Co-like)* 2.72:1 500 (@5V) “5V” cathode

372 (C6) 170 (LiFePO4) 2.19:1 396 (@3.4V) Olivine cathode

* indicates theoretical or hypothetical value

Why is the cathode material currently the bottleneck for reaching higher energy density for LIBs?

Higher energy density via: o Increase in capacity o Increase the voltage of the material against Li/Li+ redox pair

http://agmetalminer.com/2013/12/will-general-motors-car-sales-keep-booming-steel-aluminum-

sectors-hope-so/.

Two commercial anodes:

o Carbon: low cost, abundant; outstanding kinetics; large volume change (12%); SEI layer and denditric growth; easy to catch fire.

o Li4Ti5O12: zero-strain material (0.2% volume change); negligible SEI layer growth; limited capacity (175mAh/g).

O. Le Bacq, A. Pasturel, First-principles study of LiMPO4 compounds (M=Mn, Fe, Co, Ni) as

electrode material for lithium batteries. Philosophical Magazine 2005, 85, 1747. V. C. Fuertes et al, Journal of Physics-Condensed Matter 2013, 25.

Superiority: High voltage (5.1V for LiNiPO4) and high energy density (40% enhancement over current cathodes), structure stability (olivine), low cost, abundance in nature.

Limitation: poor electronic conductivity; no electrochemical capacity.

Approach: nanostructure fabrication, M2 site solid solution, carbon coating.

LiNixFe1-xPO4 cathode materials Superiority: low cost, abundance; negligible

SEI layer; < 4% volume change; larger theoretical capacity (336 mAh/g) over Li4Ti5O12, comparable to carbon.

Limitation: poor electronic conductivity; limited rate performance.

Approach: nanostructure fabrication; electronic conductivity enhancement by carbon coating, inducing oxygen vacancy and forming composite with carbon nanotubes.

TiO2 based anode materials

Lithium insertion/extraction was shown in LiNixFe1-xPO4 nanocomposites.

Argon calcination reduces sizes of TiO2 and renders a 27.1% enhancement in capacity.

Hydrogen treatment increases oxygen vacancies and adds 48.3% in capacity at 10C.

Novel LiNixFe1-xPO4 - TiO2 LIBs may deliver similar performance as traditional LiCoO2 – graphite system but without fire hazard. It is promising in applications where safety is crucial such as in EVs.