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.