V. Focused Fundamental Research - EERE - U.S. Department of ...

V.B.6 Cell Analysis-Interfacial Processes: SEI Formation and Stability on
Cycling (HQ)
Karim Zaghib
Hydro-Quebec IREQ
1800 Lionel Boulet
Varennes, QC, Canada J3X 1S1
Phone: (450) 652 8019; Fax: (450) 652 8424
E-mail: Zaghib.Karim@ireq.ca
mailto:cashtiani@ENERDEL.com
Subcontractor:
Lawrence Berkeley National Laboratory, Berkeley, CA
Start Date: March 2010
Projected End Date: September 2011
Objectives
· Synthesis and evaluation of high-voltage cathode
(spinel Mn-Ni) with improved electrochemical
stability.
· Reduce the oxidation of the cathode composition,
electrolyte, and separator. Find the appropriate
alternative anode composition that meets the
requirement for low cost and high energy.
· Continue development of ex situ and in situ SEM to
increase our understanding of the failure mode of the
cathode and anode materials.
Technical Barriers
Low energy density and poor cycle/calendar life
Technical Targets
· Identify a suitable technique to stabilize the interface
reaction of the high-voltage oxide (Mn-Ni based, e.g.,
LiMn 1.5 Ni 0.5 O 4 ) cathode by surface coating with a
more stable material such as an olivine. The emphasis
is to improve electrochemical performance at high
voltage
· Investigate the effect of the type of binder, electrolyte
composition, and separator on performance at high
voltage
· Develop high-capacity anodes based on Si
composition.
Accomplishments
· Demonstration of the benefit of surface coating of
high-voltage LiMn 1.5 Ni 0.5 O 4 cathode with LiFePO 4
olivine material
· Optimize a silicon-based composition as highcapacity
anode material.
· Develop ex situ and in situ SEM tools for
understanding the SEI layer and the failure mode in
Si-based anode.
Introduction
BATT is searching for the next-generation systems for
high energy. In 2011, BATT program management
recommended working with; (i) spinel high-voltage
cathode based on Mn-Ni, (ii) Si-based alloy anode and (iii)
studies on SEI layers on alloy anode and cathode.
Following the strategy to develop high-energy
batteries, high-voltage cathodes based on Mn-Ni spinel
will be studied. In the first part of the project, HQ plans to
protect the surface of the cathode by a thin layer of olivine
LiFePO 4 . By this process, we expect to reduce the
oxidation of the electrolyte and enhance the safety of the
high-voltage cathode. Dry or wet processes will be
explored to modify the surface of the cathode.
The HQ strategy related to the anode material is based
on mixing particles of carbon-coated SiO x with graphite
powder to reduce the volume expansion and increase the
first-cycle coulombic efficiency. To improve the capacity
of the anode; we evaluated nano-Si particles mixed with
graphite as one configuration and ternary compounds
nano-Si-SiOx-graphite as a second configuration. Varying
Si-nano:graphite:SiOx compositions will be investigated to
determine the minimum content of graphite required in the
anode. Due to the major effect of the binder on the
performance of the anode, various types of binder were
investigated
To further improve our comprehension on the SEI
layer with the Si-based anodes and Mn-Ni cathodes, two
analysis methods are adopted; ex situ SEM on cycled
electrodes with liquid electrolyte and in situ SEM during
anode cycling where the dry polymer was used as binder in
the anode to avoid electrolyte evaporation.
Energy Storage R&D 492 FY 2011 Annual Progress Report