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

V.C.9 New Layered Nanolaminates for Use in Lithium Battery Anodes (Drexel
U)
Yury Gogotsi and Michel Barsoum
Drexel University
Materials Science and Engineering Department
3141 Chestnut St, MSE Dept. Lebow 344.
Phone: (215) 895-6446; Fax: (215) 895-1934
Email: gogotsi@drexel.edu, barsoumw@drexel.edu
Subcontractor: None
Start Date: Jan 1, 2011
Projected End Date: December 30, 2015
Objectives
· To replace graphite in Li-ion battery (LIB) anode with
new materials: layered ternary carbides and nitrides
(MAX phases). The strategy may offer anodes with
higher charge density than graphite, lesser expansion,
longer cycle life and, potentially, a lower cost than Si
nanoparticles.
Technical Barriers
This project aims to address the following technical
barriers facing the modern LIB technology:
(A) short life-span of modern batteries,
(B) low charge density, and
(C) compromised safety.
Technical Targets
· Perform the ab initio simulation of Li incorporation
into MAX phase carbides.
· Perform electrochemical experiments on a variety of
MAX phases to select the most promising ones for
more detailed study.
· Study the effect of particle size on the capacity of the
three best MAX phase materials.
· Improve capacity by selective extraction of M or A
atoms, to add space for the Li.
· Investigate SEI formation on selected MAX phase
carbides.
· Optimization of the material. Testing the rate
capability of the anode.
· In situ study of charge/discharge processes and better
understanding of the mechanism of Li insertion.
· Comparison of powder vs. MAX phase solids with 10­
20% porosity.
Accomplishments
· Successful synthesis of porous anodes composed of
MAX phase requiring neither binder nor carbon black
additives.
· DFT simulations of Li intercalation into different
MAX phases were carried out, allowing us to gain an
insight into the dynamics controlling the process.
· Complete electrochemical study and characterization
of different MAX phases.
· Selective etching of an “A” layer was achieved
resulting in the exfoliation of MAX phases forming
new graphene-like 2-D structures composed of
transition metal carbides and/or nitrides ("MXene").
Introduction
Lithium metal, although providing the highest energy
density anode material, cannot be used due to its high
reactivity, electrolyte depletion, and dendrite formation
issues. As a substitute for Li, graphitic carbon is currently
used. We are exploring the feasibility of using layered
ternary carbides and nitrides (MAX phases) as new
generation anodes for LIB. These materials promise
increased capacity (above the 372 mAh g –1 of graphite, and
to address concerns such as safety, cycle-life, and storagelife.
We believe the MAX phases can deliver to the
strictest LIB demands due to the following: (i) their vastly
superior mechanical properties relative to graphite, (ii)
their (at least one order of magnitude) better electronic
conductivity than graphite; (iii) the possibility to make
anodes without binders by first forming thin wafers
followed by a sintering step, (iv) given the higher density
of MAX phases they can potentially outperform the
volumetric capacity of graphite, even if their gravimetric
capacity would be found wanting, (v) large choice of
chemistries available, allowing one to fine tune the
performance of the system, (vi) the latter can be further
expoited by the preparation of the sub-stoichiometric
MAX phases in A and/or M elements. We estimate, for
example, that if 50% of the Si and Ti atoms are removed
from Ti 3 SiC 2 and 4 Li atoms surround each Si, the
theoretical capacity increases to 738 mAh g –1 . Such a value
would exceed the capacity of graphite by a factor of ≈ 2.
Even higher values can potentially be reached by using
FY 2011 Annual Progress Report 567 Energy Storage R&D