nanomaterials for enhancing electrochemical energy...
TRANSCRIPT
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.