6.2 Lithium Batteries and Lithium-Ion Batteries
137
The doping with ions method is a simple way to improve the electrochemical
property of the electrode materials. For instance, Mg
2+ or Mo
6+ doping can enhance
electric conductivity of electrode material. Besides, Ni-doped Li 3 VO 4 can display
the superior Li-storage capacity and cycling stability. Cu-doped Li 3 VO 4 is another
method to improve electrical conductivity. For example, Wang et al. adopt the Cudoped Li 3 VO 4 to improve the electrochemical properties of the electrode materials.
In the work, Li 3 VO 4 doped with 10% Cu content displays the ultrahigh Li-storage
capacity (about 335 mAh g
−1 ) at 8 Ag
−1 , which is more than twice as high as the
pristine Li 3 VO 4 .
6.2.3 Electrolyte
Organic electrolyte is a key factor restricting the development of lithium-ion battery.
The organic electrolyte of Lithium-ion battery mainly has three parts: (1) lithium
electrolyte salt, (2) organic solvent, (3) additives. In addition, the organic electrolyte
also contains some other impurities such as water, hydrogen fluoride, metal ions,
and so on. Currently, LiPF 6 is used in commercial Li-ion battery. To date, no single
solvent has met the requirements of lithium-ion batteries. Therefore, typical mixed
solvents and alkyl carbonate mixed solvents have been applied in commercial Li-ion
battery.
6.2.3.1 Lithium Electrolyte Salt
Chemical and electrochemical performance of electrolyte lithium salts lithiumion battery electrolyte lithium salt, according to different types of anions, can
be divided into inorganic anion lithium salt and organic anion lithium salt as
the two major categories. The inorganic anionic lithium salts mainly include
LiClO 4 , LiBF 4 , LiAsF 6 , and LiPF 6 , etc. The organic anionic lithium salts mainly
include LiCF 3 SO 3 and LiN(SO 2 CF 3 ) 2 and their derivatives and the like. It can also
be divided into fluorine-containing lithium salts and non-fluorine-containing lithium
salts simply based on whether the anions contain fluorine or not. The anion structure is a vital factor affecting the property of lithium salt, and the smaller lattice
energy is the first condition for the lithium salt to obtain certain solubility in organic
solvents. Therefore, the lithium anion must first have a larger anion radius and the
second is easy to dissociate with the lithium ion to enhance the electronic conductivity of an electrolyte. In addition, the lithium salt anion should also have good
electrochemical stability, thermal stability, and decomposition products to form a
particularly stable SEI membrane on the negative electrode surface. The fluorinated
lithium salt anion has a charge delocalization effect, it inhibits the formation of ion
pairs and improves the conductivity of the electrolyte; besides, it also improves the
electrochemical stability of the electrolyte system; the decomposition product of salt
137
The doping with ions method is a simple way to improve the electrochemical
property of the electrode materials. For instance, Mg
2+ or Mo
6+ doping can enhance
electric conductivity of electrode material. Besides, Ni-doped Li 3 VO 4 can display
the superior Li-storage capacity and cycling stability. Cu-doped Li 3 VO 4 is another
method to improve electrical conductivity. For example, Wang et al. adopt the Cudoped Li 3 VO 4 to improve the electrochemical properties of the electrode materials.
In the work, Li 3 VO 4 doped with 10% Cu content displays the ultrahigh Li-storage
capacity (about 335 mAh g
−1 ) at 8 Ag
−1 , which is more than twice as high as the
pristine Li 3 VO 4 .
6.2.3 Electrolyte
Organic electrolyte is a key factor restricting the development of lithium-ion battery.
The organic electrolyte of Lithium-ion battery mainly has three parts: (1) lithium
electrolyte salt, (2) organic solvent, (3) additives. In addition, the organic electrolyte
also contains some other impurities such as water, hydrogen fluoride, metal ions,
and so on. Currently, LiPF 6 is used in commercial Li-ion battery. To date, no single
solvent has met the requirements of lithium-ion batteries. Therefore, typical mixed
solvents and alkyl carbonate mixed solvents have been applied in commercial Li-ion
battery.
6.2.3.1 Lithium Electrolyte Salt
Chemical and electrochemical performance of electrolyte lithium salts lithiumion battery electrolyte lithium salt, according to different types of anions, can
be divided into inorganic anion lithium salt and organic anion lithium salt as
the two major categories. The inorganic anionic lithium salts mainly include
LiClO 4 , LiBF 4 , LiAsF 6 , and LiPF 6 , etc. The organic anionic lithium salts mainly
include LiCF 3 SO 3 and LiN(SO 2 CF 3 ) 2 and their derivatives and the like. It can also
be divided into fluorine-containing lithium salts and non-fluorine-containing lithium
salts simply based on whether the anions contain fluorine or not. The anion structure is a vital factor affecting the property of lithium salt, and the smaller lattice
energy is the first condition for the lithium salt to obtain certain solubility in organic
solvents. Therefore, the lithium anion must first have a larger anion radius and the
second is easy to dissociate with the lithium ion to enhance the electronic conductivity of an electrolyte. In addition, the lithium salt anion should also have good
electrochemical stability, thermal stability, and decomposition products to form a
particularly stable SEI membrane on the negative electrode surface. The fluorinated
lithium salt anion has a charge delocalization effect, it inhibits the formation of ion
pairs and improves the conductivity of the electrolyte; besides, it also improves the
electrochemical stability of the electrolyte system; the decomposition product of salt