6.3 The Theory and Research Progress of Sodium-Ion Batteries
149
6.3.2 Anode Material
6.3.2.1 Carbon-Based Anode Material
I. Graphite carbon-based anode materials
Structured graphite has good electrical conductivity and is suitable for the insertion and extraction of Li
+ . It has a wide range of sources and low cost, which is
commonly used in LIB systems. Through the electrochemical reduction process, Li
+
is embedded in the Van der Waals gap between the graphitic carbon layers and forms
a first-order lithium-graphite intercalation compound (LiC 6 ). Its reversible capacity
is greater than 360 mAh/g (C the = 372 mAh/g) (Chen et al. 2017b). In contrast,
the results of graphite as a cathode material in SIBs are not optimistic. Early firstprinciples calculations showed that Na
+ ions are unable to form intercalated graphite
compounds than other alkali metals (DiVincenzo and Mele 1985).
Studies have shown that the insertion of Na
+ forms a higher order compound of
NaC 64 , and the possibility of electrochemical reduction to form low-order sodiumgraphite remains to be explored. In addition, the theoretical capacity of the anode
material in SIBs is only 35 mAh/g, due to the fact that the distance between the
graphite layers of the graphite ink is about 0.335 nm, which is smaller than the
minimum interlayer spacing of Na
+ (0.37 nm). In recent years, researchers have
found that by increasing the interlamellar spacing of graphite and selecting suitable
electrolyte systems (such as ether-based electrolytes), it is possible to increase the
sodium storage capacity of graphite and improve its electrochemical performance.
Expanded Graphite (EG) is a superior carbon-based anode material in SIB. EG is a
graphite-derived material formed by a two-step redox process that retains the longrange ordered layered structure of graphite. The interlaminar distance of 0.43 nm
can be obtained by modulating oxidation and reduction processes. These features
provide electrochemical insertion of Na
+ . The favorable conditions are shown in
Fig. 6.7. EG may be a promising carbon-based anode material in SIBs.
Fig. 6.7 Schematic illustration of sodium storage in graphite-based materials, reprinted from Ref.
(Wen et al. 2014), copyright 2014, with permission from Nature
149
6.3.2 Anode Material
6.3.2.1 Carbon-Based Anode Material
I. Graphite carbon-based anode materials
Structured graphite has good electrical conductivity and is suitable for the insertion and extraction of Li
+ . It has a wide range of sources and low cost, which is
commonly used in LIB systems. Through the electrochemical reduction process, Li
+
is embedded in the Van der Waals gap between the graphitic carbon layers and forms
a first-order lithium-graphite intercalation compound (LiC 6 ). Its reversible capacity
is greater than 360 mAh/g (C the = 372 mAh/g) (Chen et al. 2017b). In contrast,
the results of graphite as a cathode material in SIBs are not optimistic. Early firstprinciples calculations showed that Na
+ ions are unable to form intercalated graphite
compounds than other alkali metals (DiVincenzo and Mele 1985).
Studies have shown that the insertion of Na
+ forms a higher order compound of
NaC 64 , and the possibility of electrochemical reduction to form low-order sodiumgraphite remains to be explored. In addition, the theoretical capacity of the anode
material in SIBs is only 35 mAh/g, due to the fact that the distance between the
graphite layers of the graphite ink is about 0.335 nm, which is smaller than the
minimum interlayer spacing of Na
+ (0.37 nm). In recent years, researchers have
found that by increasing the interlamellar spacing of graphite and selecting suitable
electrolyte systems (such as ether-based electrolytes), it is possible to increase the
sodium storage capacity of graphite and improve its electrochemical performance.
Expanded Graphite (EG) is a superior carbon-based anode material in SIB. EG is a
graphite-derived material formed by a two-step redox process that retains the longrange ordered layered structure of graphite. The interlaminar distance of 0.43 nm
can be obtained by modulating oxidation and reduction processes. These features
provide electrochemical insertion of Na
+ . The favorable conditions are shown in
Fig. 6.7. EG may be a promising carbon-based anode material in SIBs.
Fig. 6.7 Schematic illustration of sodium storage in graphite-based materials, reprinted from Ref.
(Wen et al. 2014), copyright 2014, with permission from Nature