6.2 Lithium Batteries and Lithium-Ion Batteries
123
The modification of spinel LiMn 2 O 4 is usually through ion doping, surface
coating, and other methods. Doping is one of the most widely reported methods
at present. It mainly inhibits the Jahn–Teller distortion effect by doping some transition metal elements like Mn ions, such as Fe (Bang et al. 2003), Cr (Taniguchi and
Research 2005), Al (Taniguchi and Research 2005), Mg (Kakuda et al. 2007), and
so on. The surface coating is mainly used to protect the electrode active substances,
inhibit the side reaction from the active substances to the electrolyte, reduce the
probability of manganese dissolved in the electrolyte during the reaction process,
thereby improving the overall cycle performance of the material. The commonly
used coating materials include ZnO (Tu et al. 2007), SiO 2 (Arumugam and Kalaignan
2008), Al 2 O 3 (Lee et al. 2004), TiO 2 (Yu et al. 2006), and so on.
Olivine Structure (LiFePO 4 ) Positive Material
LiFePO 4 is used as a new cathode material for the past few years. Since it has stable
structure and high reversible capacity, it is mainly used in high-rate lithium-ion
batteries. People used to call it lithium iron phosphate. In 1997 (Padhi et al. 1997),
John. B. Goodenough et al. Of Texas State University reported that LiFePO 4 had
the function of reversible out/in Li
+ , but the material didn’t cause much attention
because of its low electronic conductivity and poor charge–discharge performance.
Since 2002, ion doping modification of LiFePO 4 materials has greatly improved its
electrical conductivity and high current charge and discharge performance, which
has caused widespread research and rapid development.
LiFePO 4 is an olivine structure with orthonormal symmetry. The space point group
is Pbnm, the cell parameter is a = 0.6008 nm, b = 1.0334 nm, c = 0.4693 nm, and
the cell volume is 0.2914 nm
3 (Sources 2011). In the olivine structure of LiFePO 4 , O
atoms are distributed in the form of six party dense heap. P atoms and O atoms form
PO 4 tetrahedron through covalent bonds, Li and Fe, respectively, form LiO 6 and FeO 6
eight-hedron with the ionic bonds of O atoms, respectively. The FeO 6 octahedron is
connected to the bc plane at a specific angle. A PO 4 tetrahedron, two LiO 6 octahedron
and a FeO 6 octahedron are connected to form a three-dimensional structure. When
Li
+ is removed, the Li x FePO 4
Li 1−x FePO 4 phase interface is produced. With the
continuous withdrawal of Li
+ , the interfacial area decreases. When reaching a critical
surface area, Li
+ is limited by the interface. Therefore, the Li-storage capacities of
LiFePO 4 are affected by diffusion rate of Li
+ , especially under the influence of high
current.
LiFePO 4 is favored by researchers, mainly because of the following advantages:
1. Excellent safety, high temperature property, and thermal stability are the safest
cathode material for lithium-ion battery at present.
2. High reversible specific capacity, its theoretical specific capacity is
170 mAh g
−1 .
3. It has no pollution to the environment and does not contain any heavy metal
elements that are harmful to the human body.
4. It has excellent overcharge resistance and no memory effect.
5. The resources are abundant, and the cost is low.
123
The modification of spinel LiMn 2 O 4 is usually through ion doping, surface
coating, and other methods. Doping is one of the most widely reported methods
at present. It mainly inhibits the Jahn–Teller distortion effect by doping some transition metal elements like Mn ions, such as Fe (Bang et al. 2003), Cr (Taniguchi and
Research 2005), Al (Taniguchi and Research 2005), Mg (Kakuda et al. 2007), and
so on. The surface coating is mainly used to protect the electrode active substances,
inhibit the side reaction from the active substances to the electrolyte, reduce the
probability of manganese dissolved in the electrolyte during the reaction process,
thereby improving the overall cycle performance of the material. The commonly
used coating materials include ZnO (Tu et al. 2007), SiO 2 (Arumugam and Kalaignan
2008), Al 2 O 3 (Lee et al. 2004), TiO 2 (Yu et al. 2006), and so on.
Olivine Structure (LiFePO 4 ) Positive Material
LiFePO 4 is used as a new cathode material for the past few years. Since it has stable
structure and high reversible capacity, it is mainly used in high-rate lithium-ion
batteries. People used to call it lithium iron phosphate. In 1997 (Padhi et al. 1997),
John. B. Goodenough et al. Of Texas State University reported that LiFePO 4 had
the function of reversible out/in Li
+ , but the material didn’t cause much attention
because of its low electronic conductivity and poor charge–discharge performance.
Since 2002, ion doping modification of LiFePO 4 materials has greatly improved its
electrical conductivity and high current charge and discharge performance, which
has caused widespread research and rapid development.
LiFePO 4 is an olivine structure with orthonormal symmetry. The space point group
is Pbnm, the cell parameter is a = 0.6008 nm, b = 1.0334 nm, c = 0.4693 nm, and
the cell volume is 0.2914 nm
3 (Sources 2011). In the olivine structure of LiFePO 4 , O
atoms are distributed in the form of six party dense heap. P atoms and O atoms form
PO 4 tetrahedron through covalent bonds, Li and Fe, respectively, form LiO 6 and FeO 6
eight-hedron with the ionic bonds of O atoms, respectively. The FeO 6 octahedron is
connected to the bc plane at a specific angle. A PO 4 tetrahedron, two LiO 6 octahedron
and a FeO 6 octahedron are connected to form a three-dimensional structure. When
Li
+ is removed, the Li x FePO 4
Li 1−x FePO 4 phase interface is produced. With the
continuous withdrawal of Li
+ , the interfacial area decreases. When reaching a critical
surface area, Li
+ is limited by the interface. Therefore, the Li-storage capacities of
LiFePO 4 are affected by diffusion rate of Li
+ , especially under the influence of high
current.
LiFePO 4 is favored by researchers, mainly because of the following advantages:
1. Excellent safety, high temperature property, and thermal stability are the safest
cathode material for lithium-ion battery at present.
2. High reversible specific capacity, its theoretical specific capacity is
170 mAh g
−1 .
3. It has no pollution to the environment and does not contain any heavy metal
elements that are harmful to the human body.
4. It has excellent overcharge resistance and no memory effect.
5. The resources are abundant, and the cost is low.