Li x CoO 2 cathode). It appears that the basic anode process in these cells is lithium
insertion into tin oxides, which forms LiaSn alloys in a matrix of Li 2 O. Hence, the
reversible process that finally remains is lithium alloying with metallic tin. For this
purpose we have prepared SnO 2 , and later SnO semiconductor nanoparticles. They
were synthesized by ultrasonic irradiation of an aqueous solution of SnCl 4 and
azodicarbonamide under ambient air [93]. These nanoparticles are 3–5 nm in size,
as calculated using the Debye–Scherrer formula, and as observed by TEM. Electrochemical tests were performed using the SnO 2 nanoparticles as the electrode
materials in nonaqueous Li salt solutions. Amorphous, as well as crystalline,
nanoparticles were prepared for this project. The performance of the anode was
examined as a function of the crystalline state of the SnO 2 , as well as the particle
size.
These tests clearly indicated that the SnO 2 particles prepared by sonochemical
synthesis have a promising capacity, reversibility, and cycle life in repeated lithium
insertion and deinsertion processes. Heat treatment of the sonochemically prepared SnO 2 nanoparticles had a pronounced effect on their electrochemical behavior. The crystallization of the particles due to the heat treatment increased
both the electrode’s irreversible and reversible capacities measured during the first
lithiation–delithiation cycle. However, while the reversible capacity retention upon
cycling of electrodes made of as-prepared SnO 2 material was good, the capacity of
electrodes made of the heat-treated materials degrades upon cycling.
SnO was prepared similarly to the preparation of SnO 2 [94]. Nanoparticles of
SnO were synthesized sonochemically in mildly basic SnCl 2 solutions. The amorphous product thus obtained could be transformed to a nanocrystalline phase by
heating to 200
C. Composite electrodes comprised (by weight) of 80% SnO, 10%
graphite flakes (conductive additive), and 10% polymeric binder (an optimal composition) were tested as anodes for rechargeable Li batteries. Both the amorphous
and the nanocrystalline SnO are electrochemically active and can be reduced in
nonaqueous Li salt solutions to matrixes of Li 2 O and Li1 7 Sn 4 . The nanocrystalline
SnO was found to be much more effective and a superior anode material to the
amorphous and microcrystalline phases, as an active material for electrodes. These
electrodes could reach nearly their theoretical capacity (¼ 790 mA h g
À1 , SnO) in
electrochemical lithiation–delithiation processes versus a Li counter electrode in
nonaqueous Li salt solutions. However, there is still a long way to go to the possible use of SnO as an anode material in practical batteries. This is due to its high
irreversible capacity (Li 2 O formation and surface film precipitation due to reactions
of lithium–tin compounds with solution species) and gradual capacity decrease
during repeated charge–discharge cycling. Possible reasons for this capacity fading
are discussed in [94].
6.1.2.6 The Sonochemical Synthesis of Mesoporous Materials and the Insertion
of Nanoparticles into the Mesopores by Ultrasound Radiation
In a recent review article the synthesis of mesoporous (MSP) silica is considered to
be one of the four most important discoveries in solid-state and materials science
in the last decade [95]. We have summarized our activities in this field in an article
6.1 Sonochemistry 137
insertion into tin oxides, which forms LiaSn alloys in a matrix of Li 2 O. Hence, the
reversible process that finally remains is lithium alloying with metallic tin. For this
purpose we have prepared SnO 2 , and later SnO semiconductor nanoparticles. They
were synthesized by ultrasonic irradiation of an aqueous solution of SnCl 4 and
azodicarbonamide under ambient air [93]. These nanoparticles are 3–5 nm in size,
as calculated using the Debye–Scherrer formula, and as observed by TEM. Electrochemical tests were performed using the SnO 2 nanoparticles as the electrode
materials in nonaqueous Li salt solutions. Amorphous, as well as crystalline,
nanoparticles were prepared for this project. The performance of the anode was
examined as a function of the crystalline state of the SnO 2 , as well as the particle
size.
These tests clearly indicated that the SnO 2 particles prepared by sonochemical
synthesis have a promising capacity, reversibility, and cycle life in repeated lithium
insertion and deinsertion processes. Heat treatment of the sonochemically prepared SnO 2 nanoparticles had a pronounced effect on their electrochemical behavior. The crystallization of the particles due to the heat treatment increased
both the electrode’s irreversible and reversible capacities measured during the first
lithiation–delithiation cycle. However, while the reversible capacity retention upon
cycling of electrodes made of as-prepared SnO 2 material was good, the capacity of
electrodes made of the heat-treated materials degrades upon cycling.
SnO was prepared similarly to the preparation of SnO 2 [94]. Nanoparticles of
SnO were synthesized sonochemically in mildly basic SnCl 2 solutions. The amorphous product thus obtained could be transformed to a nanocrystalline phase by
heating to 200
C. Composite electrodes comprised (by weight) of 80% SnO, 10%
graphite flakes (conductive additive), and 10% polymeric binder (an optimal composition) were tested as anodes for rechargeable Li batteries. Both the amorphous
and the nanocrystalline SnO are electrochemically active and can be reduced in
nonaqueous Li salt solutions to matrixes of Li 2 O and Li1 7 Sn 4 . The nanocrystalline
SnO was found to be much more effective and a superior anode material to the
amorphous and microcrystalline phases, as an active material for electrodes. These
electrodes could reach nearly their theoretical capacity (¼ 790 mA h g
À1 , SnO) in
electrochemical lithiation–delithiation processes versus a Li counter electrode in
nonaqueous Li salt solutions. However, there is still a long way to go to the possible use of SnO as an anode material in practical batteries. This is due to its high
irreversible capacity (Li 2 O formation and surface film precipitation due to reactions
of lithium–tin compounds with solution species) and gradual capacity decrease
during repeated charge–discharge cycling. Possible reasons for this capacity fading
are discussed in [94].
6.1.2.6 The Sonochemical Synthesis of Mesoporous Materials and the Insertion
of Nanoparticles into the Mesopores by Ultrasound Radiation
In a recent review article the synthesis of mesoporous (MSP) silica is considered to
be one of the four most important discoveries in solid-state and materials science
in the last decade [95]. We have summarized our activities in this field in an article
6.1 Sonochemistry 137