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.