Journal of Power Sources 160 (2006) 638–644
Preparation of carbon-coated Sn powders and their loading
onto graphite ﬂakes for lithium ion secondary battery
, Tadamitsu Hirabayashi
, Tomoyuki Okuni
, Michio Inagaki
Faculty of Engineering, Aichi Institute of Technology, Yakusa, Toyota 470-0392, Japan
ToyoTanso Co. Ltd., Ohnohara-cho, Mitoyo-gun, Kagawa 769-1612, Japan
Received 4 November 2005; received in revised form 25 January 2006; accepted 25 January 2006
Available online 7 March 2006
Carbon-coated Sn powders were prepared from the powder mixtures of thermoplastic precursor PVA, SnO
and MgO. The characterization of
composite powders synthesized was carried out by XRD, TG, TEM, SEM and anodic performance measurement. SnO
was reduced to metallic Sn
by heating with PVA, and its particle size in carbon shell was around 30–100 nm. MgO existence hindered the agglomeration of molten metallic
Sn and made the dispersion of metallic Sn as ﬁne particles possible. They showed high anodic performance in lithium ion batteries; high charge
capacity as 500 mAh g
even after tenth cycle and stable cyclic performance. The spaces left in carbon shell by MgO after its dissolution were
supposed to absorb a large volume expansion of Sn metal particle by Li alloying during discharging. When carbon-coated Sn loaded onto graphite
ﬂakes, metallic tin contributed to the increase in capacity.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Lithium ion secondary battery; Anode; Tin; Carbon-coating
The development in lithium ion rechargeable batteries has
helped to make various modern electronic devices lighter and
smaller. Now their higher power, better performance and longer
life are strongly desired. Commercial cells have been devel-
oped by selecting suitable electrode materials, either LiCoO
for the cathode and graphite for the anode, where the
intercalation and deintercalation processes of lithium ions were
known to be fundamental electrochemical reactions [1–4].
For the anode, various types of carbon materials were used:
a wide range of carbon materials from low-temperature carbons
with amorphous structure to well-crystallized natural graphite
, surface modiﬁed carbons  and carbon nanotubes .
Instead of carbon materials, metal oxides and metal alloys
also have been investigated; for example, MnV
brannerite-type structure [8,9], silicon–carbon alloy  and
Corresponding author. Tel.: +81 56 5488121; fax: +81 56 5480076.
E-mail address: email@example.com (T. Morishita).
metallic tin mixed in carbon materials [11,12]. Tin, Sn, was one
of the materials, which attracted attention, mainly because of its
large theoretical capacity of 990 mAh g
, but it shows marked
volume expansion when it is alloyed with lithium in the elec-
trode of lithium ion rechargeable batteries. In order to prevent
volume expansion, various preparation and dispersing processes
of ﬁne Sn particles were tried [11–14].
Carbon coating through a simple process, i.e., heat treatment
of a mechanical mixture of a ceramic powder with a carbon pre-
cursor in inert atmosphere, has been successfully applied on var-
ious ceramics, such as different aluminum oxides, magnesium
oxide, titanium oxide, various iron oxides, nickel oxide, natural
graphite, ceramic tiles, etc., and also aluminum plate of which
surface was electrochemically oxidized [15–25]. The particles of
oxides of typical elements, Al and Mg, were covered by thin car-
bon layers and kept in separated particles, no aggregation, if the
mixing ratio of carbon precursor was selected appropriately .
In the cases of transition elements, Fe and Ni, their oxides were
reduced to metals through the interaction with coated carbon,
resulting in carbon-coated metal particles, and graphite crystals
were formed at a temperature of 900–1100
C by the catalytic
0378-7753/$ – see front matter © 2006 Elsevier B.V. All rights reserved.