(103d) Incorporating Nano-Si Particles Into Cellulose-Based Anodic Composites for Lithium-Ion Batteries

Incorporating Nano-Si Particles into Cellulose Fibers as a Way
of Making Anodic Composites for Lithium-Ion Batteries

Joseph
Wokpetah^{1, 2}, Simon Leijonmarck² and Goran
Lindbergh²

¹The Pennsylvania State University,
Department of Chemical Engineering, 212 Fenske Laboratory, University Park, PA
16802,USA

² KTH-Royal Institute of
Technology, Division of Applied Electrochemistry, Teknikringen
42, 100 44 Stockholm, Sweden

Lithium-ion batteries are a class
of rechargeable batteries in which lithium ions migrate from the cathode to the
anode during discharge and vice versa during charging of the battery. These
batteries have become if not the most important, one of the important batteries
over the years and have grown from R&D interest to sales of over 4 billion
units in 2009 [3].
Most devices and electronics that require multiple recharging cycles use
lithium ion batteries since they can be recharged many times without losing
their capacity. In addition, due to their high electric potential, one can
store lots of energy per mass of lithium.

One of the many areas of
lithium-ion batteries that are still being researched is the anode material.
Silicon is becoming more preferred compared to carbon as the negative electrode
material due to many factors and the most renowned being its capacity: '3579
mAh/g for silicon versus 372 mAh/g for carbon' [4]. This
means that using silicon instead of carbon, as the anodic material for
lithium-ion batteries will make the battery better in terms of storage of
energy density and cycling.

Silicon is, however, known to fall
off the cupper current collector during discharging and charging of the
battery, due to the increase in its size as it forms complexes with the lithium
ions. This effect decreases the capacity and lifetime of the battery. Sanchez
et al have shown that binding these silicon particles on the surface of a
cellulose fiber increases the batteries' performance[5]. This
project aims to investigate how lithium-ion batteries will perform when silicon
particles are incorporated in the pores of a cellulose fiber used in making the
anodic material for the battery.

The method used involves
continuous mixing of cellulose fibers with silicon and carbon particles in
ethanol. Part of the mixture is solvent exchanged from ethanol to acetone and
finally to pentane, whilst the other part is not solvent exchanged. The purpose
of solvent exchange is to keep the fibers relatively open after drying. We
hypothesize that after analysis of our final results, the battery's capacity
and lifetime will increase compared to the conventional method which uses just
silicon.

We were successful in building a functional
lithium ion battery with a silicon-cellulose anodic material but had challenges
with the battery's cyclability.